Vibrational Spectra of a Mechanosensitive Channel

We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the transmembrane helices, which is changing during the opening process. Linear dichroism cannot distinguish an intermediate structure from the closed structure, but sum-frequency generation can. In addition, we find that two-dimensional infrared spectroscopy can be used to distinguish all three investigated gating states of the mechanosensitive membrane channel.

Исследования ледового режима на акватории Хатангского залива в море Лаптевых

The study was carried out to reveal characteristics of the ice regime of poorly explored water area of the Khatanga Bay in the South-Western part of the Laptev Sea. Actuality of the research is due to the high potential of hydrocarbon reserves in the license area «Khatangsky» of the PAO «NK «Rosneft Currently available methods of monitoring ice cover and hydrometeorological conditions throughout the year were used. The main features of the hydrological regime of the region in the ice-free period, reflected in the spatial distribution of thermohaline characteristics and sea level fluctuations, are shown. The area under investigation has specific features of the conditions for the formation of ice cover: the entire area is covered with the fast ice; the winter fresh water infl w from Khatanga and Anabar rivers results in the desalination of sea water, and this promotes formation of ice cover, which differs in crystal structure and texture from both fresh and sea ices. These factors do influence on the mechanical properties of ice, including its strength. It was found that the average and maximum values of strength of the smooth and deformed ice of the Khatanga Gulf are approximately twice as high as the similar values of the sea ice strength in the southern part of the Laptev Sea. The basic features of the spatial distribution of different types of deformations of the ice cover such as lines of ice hummocks, zones of homogeneous ice hummocking, and stamukhas had been determined.Цель исследований – выявить особенности ледового режима малоизученной акватории Хатангского залива в море Лаптевых. На основе круглогодичных исследований на стационаре «Хастыр» и весенних исследований с использованием вертолёта обнаружены новые особенности формирования ледяного покрова, связанные с притоком пресных вод и большого количества примесей, которые приводят к повышенной прочности льда. Установлено пространственное распределение различных видов деформированного льда

PIP2-Binding Site in Kir Channels: Definition by Multiscale Biomolecular Simulations†

Phosphatidylinositol bisphosphate (PIP(2)) is an activator of mammalian inwardly rectifying potassium (Kir) channels. Multiscale simulations, via a sequential combination of coarse-grained and atomistic molecular dynamics, enabled exploration of the interactions of PIP(2) molecules within the inner leaflet of a lipid bilayer membrane with possible binding sites on Kir channels. Three Kir channel structures were investigated: X-ray structures of KirBac1.1 and of a Kir3.1-KirBac1.3 chimera and a homology model of Kir6.2. Coarse-grained simulations of the Kir channels in PIP(2)-containing lipid bilayers identified the PIP(2)-binding site on each channel. These models of the PIP(2)-channel complexes were refined by conversion to an atomistic representation followed by molecular dynamics simulation in a lipid bilayer. All three channels were revealed to contain a conserved binding site at the N-terminal end of the slide (M0) helix, at the interface between adjacent subunits of the channel. This binding site agrees with mutagenesis data and is in the proximity of the site occupied by a detergent molecule in the Kir chimera channel crystal. Polar contacts in the coarse-grained simulations corresponded to long-lived electrostatic and H-bonding interactions between the channel and PIP(2) in the atomistic simulations, enabling identification of key side chains

Molecular Biomechanics: The Molecular Basis of How Forces Regulate Cellular Function

Recent advances have led to the emergence of molecular biomechanics as an essential element of modern biology. These efforts focus on theoretical and experimental studies of the mechanics of proteins and nucleic acids, and the understanding of the molecular mechanisms of stress transmission, mechanosensing and mechanotransduction in living cells. In particular, single-molecule biomechanics studies of proteins and DNA, and mechanochemical coupling in biomolecular motors have demonstrated the critical importance of molecular mechanics as a new frontier in bioengineering and life sciences. To stimulate a more systematic study of the basic issues in molecular biomechanics, and attract a broader range of researchers to enter this emerging field, here we discuss its significance and relevance, describe the important issues to be addressed and the most critical questions to be answered, summarize both experimental and theoretical/computational challenges, and identify some short-term and long-term goals for the field. The needs to train young researchers in molecular biomechanics with a broader knowledge base, and to bridge and integrate molecular, subcellular and cellular level studies of biomechanics are articulated.National Institutes of Health (U.S.) (grant UO1HL80711-05 to GB)National Institutes of Health (U.S.) (grant R01GM076689-01)National Institutes of Health (U.S.) (grant R01AR033236-26)National Institutes of Health (U.S.) (grant R01GM087677-01A1)National Institutes of Health (U.S.) (grant R01AI44902)National Institutes of Health (U.S.) (grant R01AI38282)National Science Foundation (U.S.) (grant CMMI-0645054)National Science Foundation (U.S.) (grant CBET-0829205)National Science Foundation (U.S.) (grant CAREER-0955291

Thermal conductivity of high- T c superconductors

This paper reviews existing data on the thermal conductivity of high- T c superconductors. Included are discussions of pristine polycrystalline high- T c ceramics, single crystal specimens, and high- T c materials structurally modified by substitution or by radiation damage. The thermal conductivity of high- T c superconductors is compared with that of conventional superconductors, and dramatic differences are found between the two families. Mechanisms of thermal conductivity applicable to high- T c perovskites are discussed and implications for theories of high- T c superconductivity are noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45121/1/10948_2004_Article_BF00617463.pd