Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 1465−1465
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 6
■
ION CHANNEL SENSING: ARE FLUCTUATIONS THE CRUX OF THE MATTER? “No pain, no gain!” If your trainer is still using this tired exercise mantra, it’s time to find a new gym. Pain is a signal sent to your brain from your peripheral nervous system to indicate that something is wrong, and finding pain treatment that is both safe and highly effective is one of the biggest challenges in modern medicine. Researchers continue to explore pain pathways in order to determine the best approaches. TRPV1 is an ion channel crucially responsible for transduction of nociceptive stimuli into pain signals. Upon activation, TRPV1 generates the signal that, transmitted to the thalamus through the dorsal root ganglia, is perceived as a painful sensation, which makes TRPV1 an attractive target for next-generation antipain drugs that silence pain pathways. It is known that TRPV1 activation is polymodal (i.e., a variety of stimuli can open the channel), suggesting a complex molecular mechanism of activation. In particular, TRPV1 is a biological temperature sensor because it is activated at temperatures greater than 43 °C while remaining completely nonconductive at lower temperaturesbut why? Kasimova et al. (10.1021/acs.jpclett.7b03396) tackled this question by conducting a computational investigation of TRPV1, and they found that four nonpolar cavities play a crucial role in the close-to-open transition of the channel. Using free-energy calculations, the authors found that dehydration of these four cavities triggers activation of the channel, which can explain the response to diverse environmental factors like increased cytosolic hydrostatic pressure and osmolarity. They note that the process of dehydration is exquisitely temperature dependent and is in quantitative agreement with the available experimental data. The resulting microscopic picture highlights a novel concept in biophysical chemistry, whereby a critical phenomenon (a wet/ dry transition) affects the heat capacity of the open state of the channel and thus its thermodynamic stability.
distinct states originating from two different conformations. Unexpectedly, one of the two states has a red-shifted emission spectrum. This state is not involved in energy dissipation; instead, the authors propose that it is responsible for energy transfer to photosystem I and thus for more effective distribution of energy between the photosystems. Their findings led them to redefine the function of so-called “linker proteins” in cyanobacterial light-harvesting complexes. The results may be of interest in many areas besides photosynthesis research, including super-resolution imaging, structural biology, agriculture, and solar technologies, where fine control of the excitation energy is crucial.
■
INCREASES IN THE CHARGE SEPARATION BARRIER IN ORGANIC SOLAR CELLS DUE TO DELOCALIZATION Organic solar cells are a dynamic field not only because they promise cheap and flexible devices, but also because they advance the frontiers of the fundamental physics of transport in disordered materials. But why do organic solar cells generate electric current at all? Because of their low dielectric constants, the electron and the hole should be attracted to each other with a seemingly insurmountable Coulomb attraction; therefore, the often-efficient charge separation has remained unexplained. A common argument is that charge delocalization lowers the Coulomb barrier and thus assists in charge separation, but Gluchowski et al. (10.1021/acs.jpclett.8b00292) propose that delocalization actually has the opposite effect, resulting in a larger barrier to charge separation. The authors found that, although delocalization can indeed increase efficiency, it does not do so by lowering the barrier height. Their results may lead to a better understanding of quantum effects in organic semiconductors.
■
PHYCOCYANIN: ONE COMPLEX, TWO STATES, TWO FUNCTIONS The importance of photosynthesis is probably not on most people’s minds as they go about their daily business, but the complex process is crucial to our survival. Photosynthesis sustains life by delivering energy to the ecosystem, but the process can cause lethal effects whenever an organism fails to govern the harvested solar energy. Hence, the success of photosynthesis depends equally on the efficient harvesting of solar energy and on precise regulation of energy flow. The ability to regulate the flow of excitation energy in the lightharvesting pigment−protein antenna complexes is vital for the survival of photosynthetic organisms. Gwizdala et al. (10.1021/ acs.jpclett.8b00621) investigated the main components of photosynthetic antennae from cyanobacteria using singlemolecule spectroscopy, and they discovered that these complexes possess a surprising spectroscopic and functional flexibility. Using single-molecule spectroscopy, they show that phycocyanin can dynamically switch between two spectrally © 2018 American Chemical Society
Published: March 15, 2018 1465
DOI: 10.1021/acs.jpclett.8b00708 J. Phys. Chem. Lett. 2018, 9, 1465−1465
