Sunshine superman
These digests of latest research stories which catch my eye will be paid-for content on the Alcedo newsletter once it’s up and running.
We’ve been using solar cells for longer than you think. The underlying science – the photovoltaic effect, when sunlight dislodges electrons from the structure of certain crystals, allowing them to flow as electric current – was discovered by Einstein in his so-called miraculous year of 1905, and won him his Nobel Prize in physics. Commercial solar cells, using silicon as the current-generating material, were invented in the 1950s.
But plants have been using solar electricity for billions of years. This might sound odd, but photosynthesis is actually an electrical process. Sunlight hits proteins in leaves, dislodging electrons, which then move along the protein molecules as part of the process which uses solar energy to convert carbon dioxide and water into sugars – this is known as charge transfer. Just how this happens has been unclear up to now, but biochemists in Uppsala (where sunshine is notably unevenly distributed throughout the year) believe they might have an answer.
Oddly, the Swedish team’s insight (published in Nature Chemistry: https://www.nature.com/articles/s41557-023-01413-9) came not through studying plants, but fruitflies. Long the unwitting workhorse of biological research, these insects have evolved a mechanism to repair DNA damage which, like photosynthesis, is solar-powered. It uses a protein called photylase, which contains four linked units of the amino acid tryptophan. When sunlight strikes a photylase molecule, electrons travel along this tryptophan chain. The Uppsala team has discovered that the chain changes shape to help the electrons along.
Sebastian Westenhoff and his co-researchers found that the protein structure changed in very specific ways to make charge transfer more efficient. A sequence of fast reactions, taking femto- and picoseconds (a femtosecond is a million billionth of a second, and a picosecond is a billion billionth), reshape the molecule to ease the path of electrons. You might think of it like a scene sometimes seen in cartoons, where a convoluted path suddenly straightens and tilts downwards, propelling a character usually to some misfortune at breakneck speed.
Photylase is part of the same family of proteins as cryptochromes, which regulate plant growth, and also proteins found in the eyes of some birds which use the Earth’s magnetic field to navigate when migrating. The discovery could help engineers to design chemical compounds to improve the efficiency of solar panels, batteries or any electronic component whose function depends on the transfer of electrons (which is most of them).
It's currently 15°C in London, which is just not right for the middle of February. A friend tells me it’s -10°C in Toronto, which seems more appropriate but can’t be comfortable either. It’s a constant struggle deciding what to wear. A thermal control device incorporated into clothes would be very welcome.
Racing drivers and space-farers are among those who are used to such things, usually based on pumps which circulate a warm or cold fluid around underwear. But these pumps are bulky, noisy and need batteries – also bulky and heavy. Not much good for me to pick up my dry-cleaning, or for any Canadian residents craving a Tim Horton’s without lugging equipment around. But help may be at hand! Postgraduate students at Japan’s Shibaura Institute of Technology have described in ACS Applied Materials and Interfaces (https://pubs.acs.org/doi/10.1021/acsami.3c15274) a device with the catchy name of Personal and Smart Electrodynamic Pump for clothes (PSEP for short; they’ll need to work on that). The device uses an electrohydrodynamic (EHD) pump, which works by injecting electrically-conductive materials into a liquid and moving them with an electric field. Silen and with no moving parts, such pumps solve many of the problems associated with temperature-controlled clothing.
The Japanese team, led by Yu Kuwajima, claims to have solved another problem – monitoring the flow-rate of the circulating fluid. Without this, blockages and constrictions caused by deformation of the flexible tubes circulating heating or cooling fluid might go unnoticed. Kuwajima and his labmates devised a system which senses changes in the current between the electrodes which induce flow in the conductive fluid. They have validated the measurements and designed a unit which fits into a shirt pocket and interfaces with a smartphone for monitoring and control. They claim the device can heat or cool the user by 3°C, so it’ll still feel chilly when it’s -10°C, but it’ll be more bearable.
It's clearly not the breakthrough to something Uniqlo might stock, but it’s a big step on the way. And for those who depend on temperature control to get through their day (like chemotherapy patients), it could be a giant step.
We’re very fond of red squirrels in the UK. There aren’t many of them – you won’t see them at all unless you’re in Hampshire, Cumbria or some parts of Scotland – but their starring role in Beatrix Potter’s books, appealing looks and apparent cheeky personalities have made them iconic. In most of the UK they’ve been eradicated by invasive grey squirrels. New research in the Journal of Medical Microbiology could shed new light on how this has happened (https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.001793). Researchers from the universities of Surrey and Bangor, working with the Woodland Trust and the Animal and Plant Health Agency analysed the gut microbiota of both species.
The results indicate that grey squirrels have a more diverse population of gut microbes. This could reflect their broader diet, but might also indicate better overall health and immunity. One particularly striking finding was that grey squirrels had bacteria in their digestive system that can degrade oxalate, indicating that they might be able to digest calcium in tree bark – greys are notorious bark-strippers, sometimes causing severe damage to trees. Chris Nichols of the Woodland Trust comments: “More research needs to be done to further understand the relationship between red and grey squirrels and their gut microbiota, but perhaps in the future we could develop this research into methods that could promote healthy gut bacteria in red squirrels or new ways of preventing squirrels from damaging trees.”
It's not going to bring Mrs Tiggywinkle and her family back from areas where they have been long-absent. But it might help protect red squirrels in their remaining strongholds and might conceivably help to expand these desirable red zones.
