Musings: September 2021 to ?? (current posts)

Musings is an informal newsletter mainly highlighting recent science. It is intended as both fun and instructive. Items are posted a few times each week. See the Introduction, listed below, for more information.

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   October 13 (Current e-mail)
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New items

Posted since most recent e-mail; they will be announced in next e-mail, but feel free...


Identical twins: an epigenetic marker, which may allow people to tell if they are an identical twin

October 16, 2021

This post should be of particular interest to anyone who is -- or might be -- an identical twin. Might be? Wouldn't you know? It is actually likely that most identical twins don't know, because the other twin did not survive, even to birth, and was never recognized.

Pretty much everything about identical twinning is a mystery. But a new article offers a clue -- and perhaps a test that could allow a single identical twin to be identified.

This is a story about epigenetic marks: methyl groups that decorate the genome. At least some of them affect gene activity.

Remember, the formal name for identical twins is monozygotic twins (MZ); they arise from a single fertilized egg, or zygote. In contrast, fraternal twins are dizygotic (DZ); they are from two separate zygotes, and, genetically, are just ordinary siblings.

Here is a key part of the story...

Start with parts c and d (the two graphs to the right). They are different. That is the main point, so let's look at what these two graphs are for.

Each graph compares genome methylation patterns for four groups of twins.

The four groups of twins are listed below part c. Group 1 is DZ. The others are all MZ; we'll focus on group 4 for the moment, and explain this later.

The key observation is that, in part c, groups 1 and 4 give different results. The results are the agreement in methylation patterns for a subset of methylation sites. Part d is a control, showing the results for all methylation sites; there is no difference between the types of twins (at least for the position of the peaks). (The other two groups of MZ twins give intermediate results.)

DMP = differentially methylated positions. Note that these may be either more methylated or less methylated than usual; the point is that the twins are more similar to each other than to the average.

Part b describes the three types of MZ twins. This is interesting, but is not needed for our basic point here. Briefly... Identical twins occur when a fertilized egg splits and becomes two separate organisms. Depending on when this occurs, there may be various arrangements within the uterus. These are shown in part b, labeled at the top by time of twinning. The results in part c show that each type of MZ twin gave a different result. Importantly, all types of MZ twins showed an effect. We focused on the type that gave the most extreme result.

This is part of Figure 2 from the article. I have added numbers for the four typos of twins, for ease of referring to them. The numbers are shown in the key, and in some parts of the main figure.


That is, the methylation patterns in MZ (especially group 4 MZ) are distinct. In particular, there is a set of sites (about a thousand of them, out of 400,000 sites tested) that are methylated the same way in most MZ -- measured in adults, decades after the twinning occurred.

This methylation pattern seems to be associated with twinning. What it means is unknown at this point, but clearly it will be a target of further work.

The finding also provides a test to see if someone is a MZ twin. Take an adult, measure their methylation pattern. If it best fits the right-hand distribution of part c above, that is evidence that they are a MZ twin (of type 4). Obviously, that is probabilistic, but the point is that no such test is currently available; what is shown here opens up the possibility of doing such testing.


News stories. Caution... Some of the coverage, especially in headlines, suggests a causal connection between methylation and twinning. At this point, there is no evidence about what the relationship is. To quote the article itself: "Whether these methylation differences represent a cause, effect, or byproduct of the MZ twinning event remains to be determined." (last sentence of the Discussion)
* Unique epigenetic profile found in identical twins. (Molly Godfrey, BioNews, October 4, 2021.) As usual for BioNews, it links to more information, including news stories.
* New leads in research into the origin of identical twins. (Vrije Universiteit Amsterdam, September 28, 2021.)

The article, which is open access: Identical twins carry a persistent epigenetic signature of early genome programming. (Jenny van Dongen et al, Nature Communications 12:5618, September 28, 2021.)

Among other posts on twins...
* The oldest known identical twins (December 7, 2020).
* Unusual twins: neither monozygotic nor dizygotic, but... (March 11, 2019).
* A DNA test that can distinguish identical twins (July 17, 2015). Links to more. This post also deals with genome methylation, but a different aspect.



October 13, 2021 (Current e-mail)


Briefly noted... Lakes that explode -- II

October 13, 2021

This is a follow-up to Lakes that explode (October 13, 2009)

Lakes that accumulate gas (carbon dioxide or methane, along with some hydrogen sulfide) to high pressure may explode, sometimes with devastating effect. In the earlier post we discussed two such lakes, Nyos and Kivu. Now we have an updated news feature on them, focusing on Kivu. Engineers have now completed a vent system on Nyos, which should relieve the build-up of pressure. Kivu is still a concern, but it is not clear how big the risk is. An interesting issue is that methane is now being harvested from the lake and used as fuel; whether this is being done "properly" is a matter of debate. In any case, the news feature is good reading, whether you are familiar with the topic or not. It is interesting -- and important -- geology, biology, and engineering. And politics.
* News feature: How dangerous is Africa's explosive Lake Kivu? -- An unusual lake in central Africa could one day release a vast cloud of greenhouse gases that suffocates millions of people. But it's not clear whether the threat is getting worse. (Nicola Jones, Nature, September 23, 2021. In print: Nature 597:466, September 23, 2021.)



A new way to recover valuable metals from discarded electronics

October 12, 2021

Recovery of metals from electronics waste (e-waste) is an issue. Some of the materials are scarce and expensive, some are toxic. But recycling them is difficult.

A new article offers a promising approach to recovering metals from e-waste. Simplified, the idea is to vaporize the material.

The following figure gives an example of some results...

The purpose of this particular test was to see how the presence of sodium fluoride, NaF, affected the recovery of some metals.

Recovery results are shown for four precious metals, listed along the bottom of the figure.

For each metal, there are two bars.

The left-hand bar (orange) shows the recovery, as a percentage. See the left-hand y-axis.

The right-hand bar (green) shows the effect of the additive. See the right-hand y-axis. What is plotted is Y/Yo, the ratio of recovery (yield) with and without additive.

For example, for rhodium, the first metal, recovery with the additive was over 80%, and it was enhanced about 20-fold by the additive.

Results vary for the metals, but are at least good for all except gold. In two cases, the additive made a big improvement.

The colors of the two y-axes correspond to the bar colors.

If you are concerned about the use of a toxic salt here... The full figure contains results with various additives. The general picture is similar: halide salts help. NaCl is actually quite good. I chose to show part a here because it is more fully labeled.

   This is Figure 2a from the article.


That's the idea.

What kinds of temperature are we talking about here? And how long does it take? The following figure shows temperature-time profiles from some test runs...

The top curve, for 150 volts, shows that the peak temperature was over 3300 K (about 3000 °C) after about 1/50 of a second.

At such temperatures, the metals are volatilized, but the carbon is not. That is a key point for the separation. Addition of metal halides (see first figure) leads to the metal halides, which are even more volatile.


   This is Figure 1e from the article.


That is flash heating.

The scientists then add a step, leaching the residue. They find that metals can be more easily leached from the residue than from the original material.

Overall, they achieve good recovery of several valuable metals. It isn't shown above, but they even get good recovery of gold. They also get good separation of toxic metals, which generally are more volatile than the precious metals. The residue is thought to be clean enough that it could be put on agricultural land. That hasn't been tested, but whether it is literally true or not, there is a high degree of separation.

Is it practical? Time will tell. The authors estimate that the energy input for the process is about 1% of current processes. They have scaled it up to the 10 kilogram/day level in the lab.

There are complexities. It helps to powder the e-waste. The first test above shows that additives can help, but the answer is not simple. And of course, there is downstream processing to recover much of the material. Clearly, work is needed to tune the process. But it looks worth pursuing.

The work is from the same lab that developed a flash heating process for making graphene from waste carbon-containing material. See the background post listed below.


News stories:
* Flash heating recovers precious metals from e-waste in seconds. (Amit Malewar, Inceptive Mind, October 8, 2021.)
* Urban mining for metals flashes electronic trash into treasure -- Flash Joule heating by Rice lab recovers precious metals from electronic waste in seconds. (Rice University, October 4, 2021.)
* That news release from the university was also posted at Yahoo Sports.

The article, which is open access: Urban mining by flash Joule heating. (Bing Deng et al, Nature Communications 12:5794, October 4, 2021.)

Background post about another flash heating process developed by the same lab: Briefly noted... Turning trash into graphene (October 28, 2020).

The e-waste problem was also addressed in the post Using wood-based material for making biodegradable computers (July 21, 2015).



A step toward a practical thermoelectric converter: get the oxide out

October 11, 2021

Thermoelectric conversion? It is the conversion of heat energy to electrical energy. In principle, one could convert waste heat, which is generally of low value, to useful electrical energy. However, developing a practical economical way of doing this has proved elusive.

A recent article presents a significant improvement in thermoelectric (TE) conversion, with an explanation of why it works.

The work is with tin selenide, SnSe. This material has shown promise for TE conversion, but, again, practical implementation has been elusive.

The following figure presents the bottom-line results, along with some of the evidence...

Start with the bottom graph. It plots ZT vs temperature (T).

What is ZT? It is a parameter commonly called the figure of merit for TE conversion. It is thought that a ZT above 2 would be required to make the process practical. (We'll come back to the nature of ZT in a moment.)

You can see that the red curve looks promising, with ZT even above 3. In contrast, the green curve is poor.

What's the difference? They are both for SnSe. That material tends to have some tin oxides, labeled here as SnOx, in it; those oxides prevent effective TE conversion. The red curve is for SnSe lacking tin oxides. It makes a big difference.

Why does it matter? That gets us back to ZT. Without getting into the mathematical details, the feasibility of TE depends on the ratio of electrical conductivity to heat conductivity. Remember, the goal is to convert heat to electricity. One wants low thermal conductivity, so the heat can't easily escape. And high electrical conductivity, so the electricity can easily "escape".

The top frame of the figure shows the thermal conductivity, κtot , of the two materials. You can see that removing the oxides greatly reduces the thermal conductivity. That is good, and is the key here.

- The κ is a Greek "kappa".
- It isn't shown here, but there is little effect on the electrical conductivity.
- The figure legend in the article mixes up the curves; the labeling on the figure itself, which is all that is shown here, is correct.

   This is the right-hand part of Figure 1 from the article.


That's the main message. Improving the quality of the SnSe, by reducing the amount of tin oxides in it, lowers the thermal conductivity, and enhances the TE conversion efficiency, as reflected in a high ZT.


The next figure is "for fun"...

The figure shows two pieces of SnSe, stained for tin oxide. The SnOx shows up as red.

I realize that color resolution varies, but I'll let you decide which is which here.

The white dashed lines indicate grain boundaries. That is where the oxides tend to be.

Scale bars (lower right) are 10 micrometers.

The yellow lines are related to analyses shown in later parts of the figure; you can ignore them.

   This is part of Figure 2 from the article.


The ZT of over 3 for tin selenide with an ultra-low content of oxides is the highest value ever reported. The material is inexpensive, and the processing seems practical. It is a promising development.

The envisioned application is recovering useful energy from waste heat from high-temperature industrial processes. Care will be needed to keep the device free of oxygen during long-term use. That is probably a solvable design problem. And worth it, given the huge amounts of such energy potentially available.


News stories:
* Researchers make an inexpensive material that efficiently turns waste heat to electricity -- The practical, efficient tin-based material could be a way to harness immense amounts of heat thrown out by factories, power plants, and cars. (Prachi Patel, Anthropocene, August 12, 2021.)
* Cheap material could help convert waste heat into electricity -- More than 65% of the energy we use is wasted as heat. (Tibi Puiu, ZME Science, August 3, 2021.)
* New material offers ecofriendly solution to converting waste heat into energy -- Purified tin selenide has extraordinarily high thermoelectric performance. (Science Daily (Northwestern University), August 2, 2021.)

* News story accompanying the article: Thermoelectrics: Breaking thermoelectric performance limits -- Through meticulous care for detail, researchers have now shattered the ceiling on thermoelectric performance, achieving a figure of merit above 3 for bulk SnSe polycrystalline powder. (Bo Brummerstedt Iversen, Nature Materials 20:1309, October 2021.)
* The article, which is open access: Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal. (Chongjian Zhou et al, Nature Materials 20:1378, October 2021.)

A post about a very different application of thermoelectrics: An air-conditioner you can wear? (August 19, 2019).

More tin: Pumping tin (January 12, 2018).

There is more about energy issues on my page Internet Resources for Organic and Biochemistry under Energy resources. It includes a list of some related Musings posts.



Earth is not as bright as it used to be

October 9, 2021

What do we mean by brightness of Earth? Here we are talking about its reflectance, or albedo. Shine a light on Earth; the Sun will do. How much light is reflected?

It's a bit tricky to measure, because the original light gets in the way. So you have to stand off to the side, so you can see the reflected light, without the original light interfering.

It's worth doing, because it tells us something about the Earth's energy budget. Changes in brightness may be related to climate change.

A new article reports measuring "earthshine", the reflected light from Earth lighting up the back side of the Moon.

The following figure summarizes the results, and compares them with measurements from another system...

The y-axis shows the amount of reflected light -- in energy terms, which can be derived from the reflectance measurements. The y-axis scale is relative; that is, changes are of interest, but the absolute values are not.

Look at the black points, and the black dashed line. The black data set is for the current work, based on measuring earthshine over two decades from an observatory in California. Each point is the average over a year of measurements. The dashed line is the linear best-fit for those annual averages. You can see that the dashed line does a reasonable job of fitting most of the points. And it shows a decline in reflected light corresponding to about 0.5 watts per square meter over the two-decade period.

The gray region shows the complexity of the measurements. That gray region indicates the error bars, based on individual measurements during the year. Reflectance varies a lot, but the annual average seems fairly consistent.

The blue data? Independent measurements of Earth reflectance, from a satellite, over approximately the same period. (The data is from the CERES instrument records at NASA.) The blue dashed line is similar to the black one, with about twice the slope.

   This is Figure 3 from the article.


So we have two independent sets of measurements of how bright the Earth has been over the last two decades. They are done by independent methods, and are subject to different problems. They are in reasonable agreement.

There is some attempt at interpretation. The reduced reflectance seems to correlate with reduced cloud cover over a warming ocean. If this is correct and causal, it would represent a positive feedback loop: a warming ocean leading to lower energy loss by reflectance, thus leading to more warming.

The authors here argue that their approach, using a ground-based observatory, is easier. You may or may not want to make much of the results shown above. Perhaps more importantly, the current work may pave the way for more such measurements, from multiple sites.


News stories:
* Climate change is making the Earth dimmer, which, in turn, warms up the climate -- Our planet is reflecting less sunlight into outer space. (Alexandru Micu, ZME Science, October 2, 2021.) Mixes up what makes the Moon bright at night, but generally a useful overview of the article.
* Earth is dimming due to climate change -- Warming oceans cause fewer bright clouds to reflect sunlight into space, admitting even more energy into earth's climate system. (AGU, September 30, 2021.)

The article, which is open access: Earth's Albedo 1998-2017 as Measured From Earthshine. (P R Goode et al, Geophysical Research Letters, 48:e2021GL094888, September 8, 2021.)

Among other posts about reflectance:
* Why are some icebergs green? (May 11, 2019). Discusses the term albedo.
* Why do many tarantulas have blue hair? (March 7, 2016).

A post about "geoengineering", to increase Earth reflectance, and promote cooling. Geoengineering: the advantage of putting limestone in the atmosphere (January 20, 2017).

A post about measuring ocean temperature: Seismologists measure temperature changes in the ocean (October 6, 2020).



October 6, 2021


Briefly noted... Are birthdays a risk factor for COVID-19?

October 6, 2021

Yes, according to a recent article. An extensive statistical analysis shows a significant increase in COVID within two weeks of birthdays. The authors are not able to directly measure how much of the effect is due to birthday parties, but there are suspicions. On a serious note, this could be evidence for the importance of informal social gatherings in COVID transmission.
* News story: Birthdays and COVID-19: New Analysis Reveals a Link. (SciTechDaily (Harvard Medical School), June 21, 2021.) Links to the article, which is temporarily freely available.
* I have listed this post on my BITN page section for SARS, MERS (coronaviruses).



Printing microneedle patches for vaccine delivery to the skin

October 5, 2021

Musings has noted the development of microneedle patches as an alternative to the conventional hypodermic needle for the delivery of vaccines [link at the end]. There have been promising results, but the technology has not taken off. Using the patches is easy, but producing them is not.

A new article reports progress with that step, using a version of 3D printing to make the microneedle patches. It's rather high-resolution stuff for 3D printing.

The following figure gives the idea, though without the technical advances, which were largely developed in an earlier article.

The left-hand frame shows the design pattern. Conventional needles are smooth; that is what ordinary molds can make. 3D printing allows for the production of more complex shapes. The ridged needle allows for absorption of more antigen.

The next two images are scanning electron micrographs of a needle without and with antigen bound (middle and right frames, respectively).

The scale bar on the needle images is 0.5 millimeters. The needles are about 700 µm high. They are printed in a 10x10 array on a patch that is 1 cm on a side.

The full figure in the article compares these needles with needles of a more traditional shape (square pyramidal). The surface area of these more complex needles is about 20% greater. The amount of antigen absorbed is about 36% greater.

   This is part of Figure 1A from the article.


The article contains results from tests with mice showing that the new microneedle patches work.

One of the tests is particularly intriguing. It involves looking at the T-cell response.

In this test, the production of interferon-γ (IFNγ) was measured, to reflect the T-cell response. What is shown is the number of cells making IFNγ.

The left-hand data is for "untreated" mice; no inoculation, and no IFNγ.

The next two data sets are for the use of traditional needles, giving the antigen either subcutaneous (SC) or intradermal (ID). OVA = ovalbumin, the antigen for these tests. CpG is an oligonucleotide used here as an adjuvant, which stimulates the immune response. Note that ID is better.

The next data set is for the current microneedle (MN) patch. It is much better. Note that the patch is a type of ID injection, but it is much better than the traditional ID injection.

The final (right-hand) data set is for the use of alum. It is also an adjuvant. It is used here as a variation of the traditional SC injection. It does indeed improve the response, but not much.

   This is Figure 5A from the article.


In general, the testing shows that the new microneedle patch is effective. By some tests, it is very effective. And the scientists here think they have made a significant step toward making such patches practical, by improvements in how they are made.


News stories:
* Vaccine-coated, 3D-printed patches may soon replace a syringe near you -- No jab, and more efficiency. (Alexandru Micu, ZME Science, September 25, 2021.)
* 3D Printed Vaccine Patch Offers Vaccination Without a Shot -- Outperforms Needle Jab in Boosting Immunity. (SciTechDaily (University of North Carolina at Chapel Hill), September 25, 2021.)

The article, which is open access: Transdermal vaccination via 3D-printed microneedles induces potent humoral and cellular immunity. (Cassie Caudill et al, PNAS 118:e2102595118, September 28, 2021.)

Background post about vaccine patches: Clinical trial of self-administered patch for flu immunization (July 31, 2017). The article of this earlier post is reference 27 of the current article.

More on vaccines is on my page Biotechnology in the News (BITN) -- Other topics under Vaccines (general). There is a list of related Musings posts.



Aging without memory loss in cuttlefish

October 4, 2021

Among the invertebrates, the "smartest" seem to be the cephalopods, such as octopus, squid and cuttlefish. Study of their capabilities and brains may be revealing.

A recent article suggests that cuttlefish do not lose their memory as they age, in contrast to mammals, including humans. The work is specifically about episodic memory, the ability to remember details of specific events.

Here are the key results...

The general nature of the test is that the animals were trained where to expect food. They were then tested one or three hours later, to see if they remembered. The y-axis is the fraction of responses that were correct.

There were two groups of animals: aged-adults, and sub-adults.

The results are about the same for both the old and young animals.


   This is Figure 5b from the article.


What is the significance of the finding? We don't know. For now, it is just an interesting observation. Mammals would not fare so well with such a test. How can these things do better? Is there something we should know about the advantages of a cephalopod brain? The only way we will know ...

Are we making too much of the finding, given that the cuttlefish only live for about two years? Well, let's not make too much of it. This is an animal very different from mammals; its braininess is unusual for invertebrates. Let's just continue to learn more about them.


News stories:
* Unlike Humans, Cuttlefish Retain Sharp Memory of Specific Events in Old Age. (SciTechDaily (Jacqueline Garget, University of Cambridge), August 17, 2021.)
* The Best Kind of Aging Brain -- Unlike humans, cuttlefish can form crystal-clear memories even in their final weeks. (Katherine J Wu, Atlantic, August 17, 2021.)

The article, which is open access: Episodic-like memory is preserved with age in cuttlefish. (Alexandra K Schnell et al, Proceedings of the Royal Society B 288:20211052, August 25, 2021.) A very readable article, with much discussion of the context. A caution... the actual experiments are complex.

Posts about cephalopods include:
* Sleep stages in octopuses -- do they dream? (July 13, 2021).
* A new brain study (March 3, 2020).
* Cuttlefish vs shark: the role of bioelectric crypsis (May 10, 2016).
* Deceiving a rival male (August 28, 2012).

My page for Biotechnology in the News (BITN) -- Other topics includes a section on Brain. It includes a list of brain-related posts.



An artificial organelle

October 2, 2021

Can we make a new organelle from scratch, in the lab? A recent article describes doing just that.

The article is quite complex. We'll just hit some highlights here. We'll start with the plan, then show one result for a test case, making a simple organelle. We'll then sample the results for a complex organelle that the scientists made.

Here is the plan...

Even the plan is complex. Let's start with the final step, to the right of the big bracket with a red "metal ion" next to it. There are two small structures with membranes around them; the structures are called exosomes. Just to their right, a dashed oval shows a blow-up of how they come together. Each has on it a catechol -- a benzene ring with two phenol groups. The red metal ion joins the two catechol groups, effectively holding the two structures together. That allows their membranes to fuse, making one larger structure, with a mixing of the contents.

That is the key step. The final fused exosome (FEx) is the new "organelle".

That FEx has in it the little structures from both of the small exosomes that fused together. Together, those things do something new. In this case, which is just a test, they can fluoresce. The fluorescence can be detected, as evidence that fusion occurred. This is shown here in cartoon form. The point is that the new "organelle" has new functional capabilities because of the mixed contents.


The left side shows how the exosomes that fuse, the catechol-engineered exosomes (CEx), are made. Briefly, exosomes are harvested from cells growing in lab culture, then loaded with cargo. The most interesting step, perhaps, is attaching that catechol group. That is done by attaching the catechol to an antibody against a protein on the exosome surface. When the antibody binds to the exosomes, it brings along the catechol, which ultimately is the key to directing the fusion.

Fe3+ ions were most commonly used to promote fusion, though a number of other ions tested also work.

The preferred fusion is between one of each kind of exosome (with different contents). The procedure as described so far would give random fusion. To give a higher frequency of the preferred fusion product, fusions were done in tiny droplets prepared by mixing dilute streams of the two CEx types; such droplets were most likely to contain different types of CEx.

   This is Figure 1a from the article.


The following figure shows evidence that the plan worked...

The figure shows electron micrograph images of examples of exosomes before and after fusion: small CEx and big FEx, respectively.

The Au prefix on the labels is not needed for our discussion.


   This is part of Figure 1e from the article.


The article contains data on the size distributions, and also on the new function when the contents of the two kinds of exosomes were mixed. Bottom line: the test case worked.

The authors then went on to try to establish a more complex function: production of ATP. The following figure shows some results...

In this case, fused exosomes were put in cells. ATP production was measured.

There are five curves.

The top curve (red circles) is for cells with fused exosomes and the two key materials (glucose and DTT).

The next two curves show that providing only one of those two key materials led to some, but reduced, activity.

The bottom two curves are negative controls:
- cells without added exosomes, or
- cells with exosomes, but neither of the key materials.

   This is Figure 5d from the article.


Overall, the scientists have shown that they can fuse exosomes with certain activities to create fused exosomes with novel activities. These fused exosomes can function inside cells; they are effectively artificial organelles. In particular the scientists made a new organelle that can make ATP inside cells.

No, they can't replicate.


News story: UNIST scientists created artificial organelles -- The technology can be used to construct artificial organelles that can supply ATP. (Amit Malewar, Tech Explorist, September 15, 2021.) UNIST = Ulsan National Institute of Science and Technology, South Korea.

The article: Programmed exosome fusion for energy generation in living cells. (Sumit Kumar et al, Nature Catalysis 4:763, September 2021.)

A recent post on unusual endosymbionts or organelles... A purple-green protist, with an unusual set of endosymbionts (September 25, 2021). Last week. Links to more.

A previous mention of exosomes: Briefly noted... Decoy receptors. (November 4, 2020).



September 29, 2021


Briefly noted... Improved control of gene therapy

September 29, 2021

The general plan of gene therapy has been clear for decades, but making it work well with real people remains a challenge. It is complex, and it all has to work right. A new article develops a system to control the level of gene expression. The key development here is to use a small molecule drug that controls the splicing of the messenger RNA. The drug itself can be given orally to effectively turn the gene on; the drug level determines how much protein is made. It is a known drug, developed to treat a condition that involves a splicing defect. What the current authors have done is to exploit their understanding of how the drug works in the disease case so that the delivered gene responds to the drug in a way that promotes effective gene therapy, by allowing fine tuning of the level of activity. The control system itself is portable, and can be attached to any gene of interest.
* News story: Researchers develop 'dimmer switch' to help control gene therapy -- Delivery system fine tunes gene therapy expression levels and may pave the way for a new wave of gene therapies to treat rare and complex diseases. (Science Daily (Children's Hospital of Philadelphia), July 28, 2021.) Links to the article.
* More about gene therapy is on my Biotechnology in the News (BITN) page Agricultural biotechnology (GM foods) and Gene therapy. It includes a list of related Musings posts.



Milky seas: now observable from space

September 27, 2021

The following figure shows a reconstructed image of what was seen in a region of the Indian Ocean on the night of August 3, 2019.

The bright oblong object near the top is the island of Java. It is bright from the lights of human society.

The region below is the ocean. Some of it is dark, as expected at night. But much of it is distinctly glowing. Why? From the bioluminescent bacteria in the sea.

The figure was reconstructed from actual light measurements -- taken by a set of satellites. What's special is that the satellites are very sensitive to light, and can record what might seem a faint -- though quite visible -- glow. A faint glow, but not what one expects from a body of water. (The intensities shown in the figure are scaled logarithmically from the actual intensities.)

The lit-up area of the ocean was about 100,000 square kilometers. (The area of Java is about 150,000 km2.)

   This is Figure 4e from the article.


There is nothing new about bioluminescence in the ocean. What is unusual is the large luminescent area, visible over days or even weeks. Such events are sometimes called "milky seas". Ships have reported milky sea events over the ages. Now, improved light detection systems allow satellites to observe them systematically from 830 km above. The sensitivity of the new detectors is about 1/10,000 of the intensity of reflected moonlight.

The detection system was partially implemented in 2011, and became mature in about 2018. Analysis of data on hand allowed the identification of 12 such events from December 2012 through January 2021. The current article reports on three of those events. Now, the system allows detection of events in real time. The satellites collect extensive data, tracking an event for days. Importantly, it may be possible to send research teams to the event site in some cases. Prior to the current satellite system, there was little but anecdotal reports of milky seas.

The 2019 Java event was followed from July 25 to August 9, before being lost to moonlight. It was picked up again from August 25 to September 7.


The following figure shows some aspects of the historical record...

Part c (left) shows the distribution of reports of such events in this general region -- dating back to 1796. The blue dots are reports from ships.

The distribution of events appears non-random. That is even clearer from part a of the full figure in the article, which shows a worldwide view. It is dominated by a cluster of points just south of the Arabian peninsula.

Part d (right) shows the distribution of reported events (worldwide) over the months. They are most common in August, followed by January. In some places, there seems to be a correlation with the monsoon seasons.

   This is part of Figure 7 from the article.


The satellite system ushers in a new era of studying these milky sea events -- structures at the thousand-kilometer scale formed from micrometer-sized objects. The scientists estimate the number of bacteria in the event shown above at about 1023 -- or about a sixth of a mole!


News stories:
* Scientists unravel mystery of 'milky seas' made by billions of trillions of luminous bacteria -- Milky seas have fascinated sailors and scientists alike. Now we know how they form. (Tibi Puiu, ZME Science, September 21, 2021.)
* Chasing the light from elusive 'milky seas': Unraveling mysteries of the ocean from space. (Science Daily (Colorado State University), July 29, 2021.)
* Scientists are using new satellite tech to find glow-in-the-dark milky seas of maritime lore. (Steven D Miller, Conversation, August 26, 2021.) From the lead author. Excellent.

The article, which is open access: Honing in on bioluminescent milky seas from space. (Steven D Miller et al, Scientific Reports 11:15443, July 29, 2021.)

Among posts on bioluminescence:
* Observing inside animals with an improved bioluminescence system (April 6, 2018).
* Xystocheir bistipita is really a Motyxia: significance for understanding bioluminescence (May 9, 2015).

There is a section of my page Internet resources: Chemistry - Miscellaneous on Chemiluminescence. It includes a list of related Musings posts.



A purple-green protist, with an unusual set of endosymbionts

September 25, 2021

Look...

That's a Pseudoblepharisma tenue.

Purple and green regions are clearly evident.

Scale bar = 10 micrometers.

   This is Figure 1A from the article. It is turned sideways from how it appears in the article.


The protist was first described nearly a century ago; its unusual symbionts were noted. We now have an article addressing what is going on inside.

The short answer is that it contains two photosynthetic symbionts. One is a purple bacterium, and one is a green alga. It also has mitochondria, of course. (Purple and green are the names used for the types of organisms, so we do not need to quibble about what color things seem to be.)

The purple bacterium is of particular interest. Such bacteria, of the family Chromatiaceae, are known for carrying out non-oxygenic photosynthesis. Finding eukaryotes harboring purple bacteria is rare. The current case also carries a green alga symbiont, a Chlorella species. DNA sequencing shows that the bacterial genome is significantly reduced. It is likely that these purple bacteria are obligate intracellular symbionts, not capable of living free.

What does this collection of endosymbionts do? The big story is that it provides flexibility. The host is a single-celled microbe, commonly found in habitats low in oxygen and rich in organics. It can both respire and ferment. And it can photosynthesize, under a range of conditions because of its pair of photosynthetic symbionts.

The cell shown above has a contractile vacuole (CV), at the right end. That suggests that the organism also feeds by phagocytosis.

The scientists still have difficulty maintaining the organism in lab culture. Therefore, they have done little to experimentally test their ideas of what it can do.

It is another example of the diversity of metabolism found in nature.


News stories:
* An unusual symbiosis of a ciliate, green alga, and purple bacterium. (Science Daily (University of Cologne), June 14, 2021.)
* A Protist Hosts Both Green Algae and Purple Bacteria Symbionts -- Having two different endosymbionts may allow the ciliate Pseudoblepharisma tenue to live in both oxygen-rich and oxygen-poor zones of the muddy bogs of southern Germany. (Abby Olena, The Scientist, June 11, 2021.)
* A microbial eukaryote with a unique combination of purple bacteria and green algae as endosymbionts. (Sergio A Muñoz-Gómez, ISEP (International Society for Evolutionary Protistology), June 12, 2021.) A brief overview by the lead author of the article.

The article, which is open access: A microbial eukaryote with a unique combination of purple bacteria and green algae as endosymbionts. (Sergio A Muñoz-Gómez et al, Science Advances 7:eabg4102, June 11, 2021.)

Among posts on unusual endosymbionts or organelles...
* Added October 2, 2021. An artificial organelle (October 2, 2021).
* A new energy-generating organelle (May 11, 2021).
* Briefly noted... What organisms carry genes for bacterial cell walls (peptidoglycan)? (April 1, 2020).
* What if a yeast cell contained a bacterial cell? A step toward understanding the evolution of mitochondria? (January 29, 2019).

More about purple bacteria: Arsenic and photosynthesis (September 9, 2008).



September 22, 2021


Briefly noted... A claim for the possible detection of dark energy

September 22, 2021


A team working on detecting dark matter recently claimed to detect a signal somewhat above background. Now, a group of theoretical physicists argue that dark matter is an unlikely explanation for the signal. They suggest that the signal -- if it is real -- could, more reasonably, be due to dark energy particles. There is no answer here. The story starts with a weak signal. It then goes on to complex competing theories. This is very much a science-in-progress item, about a fascinating and difficult set of topics.
* News story: XENON1T Experiment May Have Directly Detected Dark Energy. (Sci-News.com, September 16, 2021.) Links to the article, which is open access.
* A recent post about dark matter: A galaxy that lacks dark matter? (June 12, 2018). Links to more.



Briefly noted... Tiny plastics in the environment

September 21, 2021

We are increasingly recognizing how much plastic is in the environment. Among the questions... How harmful is the stuff? Of course, that may be complex, with different answers for different materials and different sizes. (The very smallest pieces, referred to as nanoplastics, are presumably most likely to get deep into tissues.) Here are two items addressing parts of the story. The big message is how much needs to be learned.

1. A news feature on "microplastics", freely available: Microplastics are everywhere - but are they harmful? Scientists are rushing to study the tiny plastic specks that are in marine animals - and in us. (XiaoZhi Lim, Nature, May 4, 2021. In print: Nature 593:22, May 6, 2021.)

2. A news story on "nanoplastics": Tiny plastic particles in the environment: Nanoplastics - an underestimated problem? (Nanowerk, May 4, 2021.) It links to an article, which is labeled Perspective.

A background post: History of plastic -- by the numbers (October 23, 2017). Links to more.



How to get bees to make better venom

September 20, 2021

Bee venom is a valuable commercial product. However, production is rather casual. That is, people just collect what they get; there is no good developed process for making bee venom.

A new article takes a step toward changing the situation. The general approach was to test the effect of a range of variables on the production of bee venom. Both the amount and composition were measured.

The following figure shows one of the more dramatic results...

The bars show the amount of venom made by two groups of bees: "active" bees vs "docile" (calm) bees.

   This is Figure 6 from the article.


Bees make more venom when they are excited -- or angry!

The scientists also looked at other factors. For example, they found differences between venoms from various sites; temperature is undoubtedly a controlling factor. But the important point is that a variable within their control -- disturbing the bees -- resulted in a major increase in the amount of venom.

Further, the scientists also measured the composition of the venom. They identified 99 components of bee venom, many of which had not been previously identified. Factors that affect the amount of bee venom can also change its composition. Further work needs to sort out which components are of particular interest, and how they can be controlled.

Much use of bee venom is not well-grounded in evidence. The current work should be a step toward high-quality systematic investigation.


News stories:
* Feisty bees make more potent venom, which makes for better medicine -- Temperature and geographical location of the hive also have an effect. (Alexandru Micu, ZME Science, August 16, 2021.)
* Angry Bees Produce Richer, More Protein-Dense Venom, Study Finds. (Sci-News.com, August 16, 2021.)

The article, which is open access: Factors driving the compositional diversity of Apis mellifera bee venom from a Corymbia calophylla (marri) ecosystem, Southwestern Australia. (Daniela Scaccabarozzi et al, PLoS ONE 16:e0253838, June 30, 2021.)

More about venom production... Snake venom gland organoids (March 17, 2020). Links to more, including a book.

A recent post about bees: If a bee visits a plant and there are no flowers, can the bee place an order? (June 23, 2020).



Square-planar silicon

September 18, 2021

A few months ago Musings discussed the shape predicted for oganesson tetratennesside, OgTs4. It is an example of a molecule having a central atom with four things attached. Structures of that general type, AB4, may be tetrahedral or square planar. Theoretical calculations for OgTs4 suggest that it might not have the shape predicted by our common simple models. That post [link at the end] includes pictures of the general shapes.

A new article reports another case of an AB4 with an unexpected shape.

Carbon and silicon are two elements that commonly form AB4 molecules. CH4 and its silicon analog SiH4 are both tetrahedral, just as one would expect.

But look...

The structure in part D (right) shows the shape of a new molecule, which is quite complex. The structure shown here is based on actual measurement, using X-ray crystallography.

Look at the silicon atom, in the middle (pink; labeled S1). It is bonded to four nitrogen atoms (blue; N1-N4). They are arranged in a plane around the Si.

There are no lone pairs on the Si. The two dashed lines upward from the Si are to show the distances; they may reflect weak interactions.

A bit about the other parts of the figure in a moment.

   This is part of Figure 2 from the article. The figure legend in the article gives bond lengths and angles around the Si.


It is the first known case of an ordinary Si atom bonded to four other atoms in this square planar geometry. The chemical may be complex, but it is stable -- stable enough to form crystals that can be measured.

A brief tour of the other parts of the figure...
- Part C (bottom center) shows a top view of the same structure.
- The structure at the top (in part A of the full figure) is a conventionally drawn structural formula. It shows the layout of the atoms, but is not intended to show shape.
- Part B (lower left) shows some crystals, as seen under the microscope.

Why does this Si show square planar bonding? It is due to the surrounding structure, which has a strong tendency to be planar. The four outer rings are planar, as are the bonds outward from those rings. So we have a planar framework with an Si that would generally be tetrahedral. Something has to give. The results show that the Si gives -- and bonds square planar in this case. Apparently, it is easier to distort the Si bonding than the surrounding framework.

The authors provide theoretical calculations that agree with what is seen.

Chemists would normally think of the square-planar geometry as representing a high-energy transition state of Si during a reaction. The current work stabilizes that high-energy state in an isolable compound. Thus the work should open up new approaches to silicon chemistry.


News stories:
* Researchers Synthesize Square-Planar Silicon-IV. (Sci-News.com, July 27, 2021.) (Erratum... The statement beginning with "To create..." is not about how the molecule was made, but about how the shape was determined.)
* Silicon with a two-dimensional structure -- Chemists succeed in producing synthesis and complete characterization. (Science Daily (University of Heidelberg), July 22, 2021.)

The article, which is open access: An isolable, crystalline complex of square-planar silicon(IV). (Fabian Ebner and Lutz Greb, Chem 7:2151, August 12, 2021.) The article also notes other types of unusual silicon bonding that have been found; see their Figure 1. (In that Figure 1, the legend items for B and C are switched.) The current case is the first unusual geometry for Si in AB4 molecules.

Background post about AB4-type molecules: The molecular shape of OgTs4 (June 29, 2021).

More unusual silicon chemistry: Carbon-silicon bonds: the first from biology (January 27, 2017). Links to more about silicon.



September 15, 2021


Briefly noted... Endometriosis: a target for treatment?

September 15, 2021

Endometriosis is a disease of uterine tissue. It is complex, with limited treatment options. There has been evidence for a genetic component. A new article used a variety of genetic approaches, studying humans and monkeys, to pinpoint a gene that makes a substantial contribution to the heritability of endometriosis. That finding led the authors to a drug that targets that gene product. The drug work is all lab-level, including treatment of mice, at this point, but it is a promising lead. Overall, the work identifies a target that is associated with endometriosis, and shows that a drug against that target has potential. The drug used here is not itself clinically useful; it provides a lead for further work.
* News stories. Both link to the article.
- Scientists identified genetic cause of endometriosis -- New insight into how to treat this debilitating disease. (Pranjal Mehar, Tech Explorist, August 26, 2021.)
- A New Drug Target for Endometriosis Treatment? (Molly Campbell, Technology Networks, August 25, 2021.) Includes an interview with two of the authors.



Do apes say "hello"?

September 14, 2021

When you meet up with someone, there are usually some preliminaries before starting what is planned. Saying "hello" is an example. Similarly, when you separate, there is usually some exchange.

A recent article explores whether two kinds of apes do this, too.

The following table summarizes the main results. Caution, it is complicated; we'll walk through parts of it. (The table title is also too complicated; leave it until you have an idea what the table is about.)

Let's look at a specific set of data.

The first column is labeled PL (play events), for bonobos. The first number is labeled "beginnings total". The number means that the scientists recorded 156 cases of two bonobos coming together and then playing. Of those, 144 began with "entries"; 12 did not.

What is an entry? It is a "hello" -- an ape form of hello. The scientists looked for interactions including gazes, physical gestures, and vocalizations. That is, most of the time, a play event began with some form of greeting. This established what the scientists call a "joint commitment", a personal bond between the two. Play followed.

The bottom numbers in that column are for the "endings". Once again, most meetings ended with some form of personal gesture that the scientists consider an "exit" -- an ape form of good-bye.


Now, the big picture...

The left half of the table is for bonobos. The right half is for chimpanzees.

The individual columns are for different kinds of activity, as listed at the bottom. The column labeled subtotal is the total for bonobos or chimpanzees. There is a total at the right, summing all the results for both types of ape.

Look over the various data sets... totals, subtotals, beginnings and endings for each activity. The general picture is the same, and is what we said above. Most beginnings and endings were accompanied by some form of "joint action", marking the start and finish of the joint commitment session.

In fact, the ratio of with to without some such joint action is about 10;1 for most of the larger data sets. The main exception is chimpanzees-grooming, where it is only 2:1.

The animals studied here are in zoos.

   This is Table 1 from the article.


From such results, the authors suggest that "joint commitments" are part of our genetic legacy.

Importantly, this is not about whether animals do things together. It is about the extent of their coordination and commitment when they do so.

The scientists also explored how such interactions depended on social structure.

It's a fun story -- and rather confusing. I suggest you take the article as opening up an idea. As so often, we'll see how it develops with further work.


News stories:
* Like humans, apes communicate to start and end social interactions. (Science Daily (Cell Press), August 11, 2021.)
* Apes signal 'hello' and 'farewell' when starting and exiting social interactions -- Our closest living relatives on the tree of life may also exhibit complex social cues that are paramount to joint commitment. (Tibi Puiu, ZME Science, August 11, 2021.)
* Animals Say "Hi" and "Bye" to Communicate What They Want -- A new study shows how bonobos and chimpanzees coordinate playing and grooming. (Marc Bekoff, Psychology Today, August 16, 2021.) This item offers a different interpretation of the findings. The author here notes that other animals, including dogs, seem to have such signals to mark the ends of social interactions. Note that he does not question the findings, but their interpretation. (Hm, are dogs special because of their relationship, even if non-genetic, with humans?) Again, there is more to be done. The item includes some references.

The article, which is open access: Assessing joint commitment as a process in great apes. (Raphaela Heesen et al, iScience 24:102872, August 20, 2021.)

More about apes:
* A new species of orangutan? (January 16, 2018).
* Age-related development of far-sightedness in bonobos (January 10, 2017).
* What do chimpanzees think about cooking food? (August 30, 2015).
* Speech: Are chimps good listeners? (July 25, 2011).



Using an electrical conductor as an insulator

September 12, 2021

Insulation of high voltage power lines is an issue. Even low losses can accumulate, with a significant overall impact.

Here is a test of how an additive affects the conductivity of power line material...

The graph shows conductivity (log scale; y-axis) vs the electric field (x-axis).

The upper curve (triangles) is for the basic material, low density polyethylene (LDPE). For the other curves, the LDPE also has a small amount of an additive, called P3HT.

Observations:
- The additive reduces the conductivity. The effect is as much as three-fold.
- The lower concentration of additive is more effective. Interesting.
- The amount of additive is very small. 0.0005% by weight is 5 ppm (parts per million).

The work here is with direct current (DC).

   This is Figure 3c from the article.


What is this P3HT stuff? The following figure shows it, with some context...

The top part is a diagram of a cable. It's complicated. But for now... There is a conducting wire in the middle. And one insulation layer is polyethylene, which is shown just below.

Also shown there is P3HT, which stands for poly(3-hexylthiophene). Thiophene is the ring, with a sulfur; it is an aromatic ring, using the lone pair electrons of the S. The polymer is an electrical conductor.

   This is Figure 1a from the article.


The authors define efficiency of an insulator additive as the reduction in conductivity per weight. By that standard, P3HT is the most efficient insulator additive known. On the other hand, the amount of improvement (reduced conductivity) is fairly low (3-fold, as noted above), because it only works at very low amounts.

The efficiency of the P3HT is nearly ten times better than the previous record-holder, graphene oxide. In contrast, zinc oxide can give a 300-fold reduction in conductivity, but only at a much higher concentration (3%); its efficiency is only 1/60 that of the P3HT.

How does this electrical conductor reduce conductivity under these circumstances? That is not at all clear.

It's all quite intriguing. A conductive polymer, which efficiently improves electrical insulation. It will be interesting to see where this leads.


News story: More efficient electricity distribution thanks to new insulation material. (Science Daily (Chalmers University of Technology), August 26, 2021.)

The article, which is open access: Repurposing Poly(3-hexylthiophene) as a Conductivity-Reducing Additive for Polyethylene-Based High-Voltage Insulation. (Amir Masoud Pourrahimi et al, Advanced Materials 33:2100714, July 8, 2021.)

More about electrical insulation:
* The SF6 story: an emerging greenhouse gas? (August 25, 2020).
* Stretchable electric wires (January 22, 2013).

A post about conductive organic polymers: What if you pulled on the ends of a ladderene? (September 26, 2017).



September 8, 2021


Briefly noted... The infection process for the SARS-2 (COVID-19) virus

September 8, 2021

A recent Nature news feature is a useful overview of the infection process, describing what is known and what is not known. The article includes comparison with other coronaviruses, and includes information on some of the "variants". If you would like to step through the process, try this item.
* A tidbit... There are two ways for the virus to enter cells. One pathway is inhibited by (hydroxy)chloroquine. Some early lab work was done with cells using that pathway. However, that is not the major pathway used in vivo. That discrepancy may explain why there was some early indication, from lab work, that the drug might work, but it did not work in the real world.
* News feature, freely available: How the coronavirus infects cells - and why Delta is so dangerous -- Scientists are unpicking the life cycle of SARS-CoV-2 and how the virus uses tricks to evade detection. (Megan Scudellari, Nature, July 28, 2021. In print, with a slightly different title: Nature 595:640, July 29, 2021.) The online version starts with a beautiful animated gif of the virus.
* Does post-exposure administration of hydroxychloroquine prevent Covid-19? A clinical trial (June 16, 2020).
* I have listed this post on my BITN page section for SARS, MERS (coronaviruses).



Making better muscles using bacteria -- and inteins

September 7, 2021

The following figure shows the toughness of a wide variety of materials...

They are grouped into three major classes: man-made, natural, and microbial materials. And then there is one more material at the right, in red. It is called "UHMW titin". It is about the best in the figure.

Toughness is one measure of the strength of a material. It is, loosely, the ability to absorb energy without being damaged.

   This is Figure 3c from the article.


What is this UHMW titin stuff? And why doesn't it fit into the first three classes?

Titin is actually a common protein. It is part of your muscles -- vertebrate muscles, contributing to their springiness. People have long been interested in making titin. However, that is hard; it is a huge protein, and very complex.

Titin is the largest protein known, with a molecular weight over 3 million.

A new article reports a process for making a titin derivative in bacteria. The product is called UHMW titin; UHMW = ultra-high molecular weight.

The following figure diagrams the process...

The box at the upper left is a diagram of part of the protein. It consists of four purple blobs linked together. Each purple blob is one "Ig" -- immunoglobulin domain, but we won't worry about that connection. The point is that this 4Ig unit, which is found like this in titin, is what promotes its strength. What we might like is more Ig.

So, let's make 4Ig units -- with "hooks" on both ends.

Drop down to the big blue boxed region. At the upper left of that box is the 4Ig with hooks on both ends. That protein is called IntC-4Ig-IntN. The two Int regions are the hooks. We'll explain the hooks in a moment. For now, let's just look at the result.

Just below that is a titin dimer. 8Ig, with hooks on both ends. To get this, two of the units shown just above are joined together, using the hooks. (The left-over hook pieces are also shown, just above the dimer.)

The process can continue, connecting together more and more 4Ig blocks. The result: a long protein with many Ig subunits. It's all done within bacteria.

   This is Figure 1b from the article.


The authors report making UHMW titin with a wide range of molecular weights, some as large as or larger than natural titin. (The 4Ig monomer unit has a molecular weight about 43,000.) Those molecules could be spun into fibers. The first figure shows one property of the UHMW titin fibers.

What are those Int hooks? Int stands for intein. It refers to an uncommon process called protein splicing. That is logically much like the better-known RNA splicing, but actually involves splicing of proteins, removing an intervening region. The two Int regions are the signals for protein splicing. That is, a key step here is exploiting the signals for natural protein splicing, so that the protein produced in the bacteria splices itself together to make longer chains.

So, the scientists have made an interesting material. Further, they have developed an interesting tool for joining proteins together.


News stories:
* Synthetic Microbial Process Produces Muscle Fibers That Are Stronger than Kevlar. (GEN, August 30, 2021.)
* Microbes build synthetic muscle fibres stronger than Kevlar. (BioTechScope, September 1, 2021.)

The article, which is open access: Microbial production of megadalton titin yields fibers with advantageous mechanical properties. (Christopher H Bowen et al, Nature Communications 12:5182, August 30, 2021.)

Other posts about muscle include... Making better artificial muscles (March 13, 2018). Links to more.



Effect of LED street lights on insects

September 4, 2021

Data...

The figure compares the number of caterpillars (moth larvae) found in similar areas, depending on the type of lighting.

Each narrow bar is for a pair of sites considered similar except for the lighting. The bars are grouped by the type of lighting, and by the type of landscape.

A specific example... The first group of narrow blue bars at the left compares sites with LED lights vs similar unlit sites; the sites here are all with hedgerows. Each bar shows the ratio (caterpillars in lit site)/(caterpillars in unlit site); low values mean that there were fewer caterpillars in the lit area. You can see that all six (narrow) bars in that part of the figure are like that. The next bar -- same color, but wide -- shows the average for that set.

In fact, the general pattern is the same for all the data sets: fewer caterpillars with lighting. The data sets to the left of the vertical dashed line for are sites with hedgerows; the data sets to the right are for sites with grass. Lighting groups are LED (light-emitting diodes), HPS (high pressure sodium), and LPS (low pressure sodium -- on the right side only).

The article contains statistical analyses of these data.

   This is Figure 1 from the article.


That's a rather impressive pattern.

One limitation of the study is that the paired sites were chosen "as is". The scientists classified existing sites based on whatever lighting they had. Is it possible that the sites differ in some other way, which is what really matters?

That calls for an experimental test...

In this test, lighting was added to two of three similar sites.

The results are shown as number of caterpillars. The bar on the left is for the unlit sites; the other two bars are for two types of lighting.

The results for the sites with LEDs are significantly lower than for the control unlit sites. The sites with HPS lights are a bit lower than the controls, but that difference is not statistically significant. (Different letters at the top indicate statistically significant differences. That is, the set labeled b tests as significantly different from those labeled a.

   This is Figure 3 from the article.


The major conclusion from the two experiments together is that LED lights reduce the activity of these caterpillars. The higher intensity and broader spectrum of current LEDs may contribute. How the light affects the insects is not understood.

How does this fit in the big picture? How should the work here affect our street lighting programs? Things to think about, but we won't address them here.


News stories. A long set, sampling the diverse interests. As common, the first one listed is perhaps the simplest overview, and the last is the most complete.
* Light pollution from street lamps linked to insect loss. (Helen Briggs, BBC, August 26, 2021.)
* LED streetlights are hurting insect populations. (Steve Bush, Electronics Weekly, August 27, 2021.)
* Dim Those Lights: Bright Streetlights Decrease Insect Populations -- They might be energy-efficient, but white LED lights are far worse for insects than the traditional sodium bulbs they are replacing, says new study. (Maureen Nandini Mitra, Earth Island Journal, August 31, 2021.)
* Streetlights reduce moth populations. (Richard Fox, Butterfly Conservation, August 26, 2021.) From an author of the article.
* LED streetlights reduce insect populations by half. (UKRI_News, August 26, 2021.)

The article, which is open access: Street lighting has detrimental impacts on local insect populations. (Douglas H Boyes et al, Science Advances 7:eabi8322, August 25, 2021.) A short, very readable article. The one-page Introduction is good.

Among posts about caterpillars...
* Caterpillars can see color even if blindfolded (September 14, 2019).
* Studying predation around the world: What can you do with 2,879 fake caterpillars? (July 28, 2017). Links to more.

Among posts about lighting:
* How to light a cave (August 30, 2021).
* Effect of artificial lighting on the environment (September 3, 2015). This post also notes special concerns about LEDs.

My page of Introductory Chemistry Internet resources has a section on Lighting: halogen lamps, etc. It includes a list of related Musings posts.



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