The photoactive site modulates current rectification and channel closing in the natural anion channelrhodopsin GtACR1

ABSTRACTThe crystal structure of GtACR1 from Guillardia theta revealed an intramolecular tunnel predicted to expand to form the anion-conducting channel upon photoactivation (Li et al. 2019). The location of the retinylidene photoactive site within the tunnel raised the question of whether, in addition to triggering channel opening by photoisomerization, the site also participates in later channel processes. Here we demonstrate the involvement of the photoactive site in chloride conductance and channel closing. Electrostatic perturbation of the photoactive retinylidene Schiff base region by glutamate substitutions alters the rectification of the photocurrent as well as channel closing kinetics. Substitutions on opposite sides of the photoactive site causes opposite changes, with channel closing kinetically correlated with Schiff base deprotonation, and the extent of these effects closely correlate with distance of the introduced glutamyl residue from the photoactive site.

Linear Nuclear Acoustic Waves in Degenerate Quantum Plasma

A rigorous theoretical investigation has been made on the linear propagation of electrostatic perturbation modes of degenerate pressure driven modified nucleus-acoustic (DPDMNA) ‘waves in a degenerate quantum plasma (DQP) system. It contains cold inertia-less degenerate electron species (DES), cold inertial non-degenerate light nucleus species (LNS) and stationary heavy nucleus species (HNS) which maintains the quasi-neutrality condition at equilibrium only. The mass density of the cold LNS provides the inertia and the cold inertia-less cold LNS provides the inertia and the cold inertia-less DES gives rise to the restoring force. The reductive perturbation method has been used for the study of nonlinear propagation of the DPDMNA waves. The basic features of linear waves are supervised in a theoretical manner. It has been observed that the phase speed of DPDMNA waves changes with the change of charge density of the stationary HNS for both non-relativistic and ultra-relativistic DES; The NA waves with their dispersion properties which are consequential in various astrophysical and laboratory plasmas, have been broadly considered. GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 5(1), Dec 2018 P 20-23

MEPPitope: spatial, electrostatic and secondary structure perturbations in the post-fusion Dengue virus envelope protein highlights known epitopes and conserved residues in the Zika virus

The dramatic transformation of the Zika virus (ZIKV) from a relatively unknown virus to a pathogen generating global-wide panic has exposed the dearth of detailed knowledge about this virus. Decades of research in the related Dengue virus (DENV), finally culminating in a vaccine registered for use in endemic regions (CYD-TDV), provides key insights in developing strategies for tackling ZIKV. The previously established MEPP methodology compares two conformations of the same protein and identifies residues with significant spatial and electrostatic perturbations. In the current work, MEPP analyzed the pre-and post-fusion DENV type 2 envelope (E) protein, and identified several known epitopes (His317, Tyr299, Glu26, Arg188, etc.) (MEPPitope). These residues are overwhelmingly conserved in ZIKV and all DENV serotypes. Characterization of α-helices in E-proteins show that α1 is not conserved in the sequence space of ZIKV and DENV. Furthermore, perturbation of α1 in the post-fusion DENV structure includes a known epitope Asp215, a residue absent in the pre-fusion α1. A cationic β-sheet in the GAG-binding domain that is stereochemically equivalent in ZIKV and all DENV serotypes is also highlighted due to a residue pair (Arg286-Arg288) that has a significant electrostatic polarity reversal upon fusion. Finally, two highly conserved residues (Thr32 and Thr40), with little emphasis in existing literature, are found to have significant electrostatic perturbation. Thus, a combination of different computational methods enable the rapid and rational detection of critical residues that can be made the target of small drugs, or as epitopes in the search for an elusive therapy or vaccine that neutralizes multiple members of theFlaviviridaefamily.

A new electrostatic mode in a dusty plasma due to dust charge fluctuation

A dusty plasma consisting of cold and hot electrons, cold ions, and charge fluctuating isolated cold dust has been considered. It has been shown by a normal mode analysis that in such a dusty plasma there exists a new type of electrostatic perturbation mode due to the charge fluctuation of the isolated dust. The basic features of this new electrostatic perturbation mode, which are different from those of the electron-acoustic waves, have also been analytically identified. The implications of these results in both the space and laboratory dusty plasma conditions are briefly discussed.