Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 3554−3554
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 12
J. Phys. Chem. Lett. 2018.9:3554-3554. Downloaded from pubs.acs.org by UNIV OF SUSSEX on 07/09/18. For personal use only.
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MECHANISM OF CARDIAC TROPOMYOSIN TRANSITIONS ON FILAMENTOUS ACTIN AS REVEALED BY ALL-ATOM STEERED MOLECULAR DYNAMICS SIMULATIONS You may not feel its rhythmic contractions, but your heart is pumping blood through your body right now. This key organ, made of cardiac muscle, is keeping you alive without any conscious effort from you, leaving you free to focus on these words. Like all muscle, cardiac muscle contracts through the interaction of thin and thick filaments. The control mechanism for this process resides in the positioning of one protein complex, tropomyosin (Tm), on the thin filament. The motion of Tm is central to all current models of the regulation of contraction and relaxation of muscle, but little is known about the manner in which Tm repositions from one state to another. Williams et al. (10.1021/acs.jpclett.8b00958) used steered molecular dynamics to study the possible movements of Tm on actin that allow transition from the blocked to the closed state. They found significant free-energy differences between an azimuthal motion and both the longitudinal motion and a motion that combined the two, possibly because of the topography of the actin subunit and the geometry of Tm binding. Tm sits in a “valley” on the actin subunit, and to make the transition azimuthally, the path would go over a “mountain”. Because of the extra work involved in traversing longitudinally along F-actin, the azimuthal transition seems to be favored over the longitudinal transitions. Although there is still no explanation for the energy required to break the interactions to allow motion of any kind, the authors speculate that the process may be initiated or promoted by the binding of myosin to actin, which mechanically destabilizes these interactions. This could disrupt electrostatic interactions to the extent that longitudinal motion is made possible by a combination of thermal energy and further myosin binding.
physical, as a barrier that blocks UV radiation; chemical, with antioxidative activity; and biological, through the activation of cellular antioxidative defense. The authors found GO to be a multitask UV protector increasing fibroblast survival, making it a potential comprehensive UV filter for use in commercially sold sunscreens and cosmetics.
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SINGLE-FILE PROTEIN TRANSLOCATIONS THROUGH GRAPHENE−MOS2 HETEROSTRUCTURE NANOPORES Graphene oxide may play a key role in photoprotection, but graphene could also contribute to global health in other ways. For example, Luan and Zhou (10.1021/acs.jpclett.8b01340) used graphene and molybdenum disulfide (MoS2) to test the currently accepted nanopore-based DNA sequencing method. Nanopore technologies show great promise in the fight against human diseases that are caused by mutations or modifications of amino acids in a protein, such as breast cancer and Alzheimer’s disease. However, a high-throughput and low-cost nanopore-based protein sequencing method is hampered by the need to thread unfolded protein molecules through nanopores whose sizes are comparable to that of an amino acid. The electric driving method can be effective for a homogeneously charged DNA molecule, but it fails to drive an unfolded protein through a nanopore because the net charge of a protein fragment inside of the pore (where the electric field exists) can be positive, negative, or neutral. Through molecular dynamics simulations, Luan and Zhou show that the transport of an unfolded protein chain through the pore is driven by the different chemical potentials for the protein adsorbed on the graphene and the MoS2 surfaces. They describe the underlying energetics of protein transport and suggest that during the transport the protein entropy is less important than the protein−pore interaction. The authors note that their design allows unidirectionally driven motion of an unfolded protein chain through the nanopore and is compatible with current electric sensing methods for amino acids.
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GRAPHENE OXIDE-MEDIATED PROTECTION FROM PHOTODAMAGE While your heart quietly keeps your body functioning, your skin is doing its part by fighting the environmental challenges it faces every day. One threat to humans’ skin is exposure to ultraviolet (UV) radiation, a major risk factor for most skin cancers. Human skin cells are equipped with a wide range of systems for protection and repair, but external UV protection has become necessary in our modern world. Despite the great deal of research that has been conducted on photoprotection, there is still no substance, compound, or material that can be called a perfect anti-UV protectant, i.e., very active, stable, and nontoxic for human cells. Therefore, scientists are searching for new photoprotective applications for both old and newly synthesized materials and have made some progress with graphene oxide. As described in their Letter, Bolibok et al. (10.1021/acs.jpclett.8b01349) analyzed GO’s capability to serve as a universal, multifunctional photoprotectant based on assays of fibroblast viability in in vitro culture. They verified three mechanisms of GO action on fibroblast in vitro cultures: © 2018 American Chemical Society
Published: June 21, 2018 3554
DOI: 10.1021/acs.jpclett.8b01848 J. Phys. Chem. Lett. 2018, 9, 3554−3554
