Структурный переход в пленках триацетата целлюлозы

Electron microscopy data are used to comparative analysis of the topological structure of the surface of two samples of cellulose triacetate (СTA) films. The samples were obtained from CTA solutions without use (sample №1) and with the use of a small sodium fluoride additive that lowers the viscosity of the solution (sample №2). It is shown that in sample №1, the nodes of the physical network of macromolecules are periodically alternating regions of local orientation order - microdomains of average size d~18 nm. In sample №2, due to repackaging of microdomains on the scale R >d, a uniformly disordered fractal cluster of the mesophase CTA is formed. The fractalization of the surface and the growth of structural anisotropy are consistent with the decrease in the viscosity of the solution and explain the change in the deformation properties of sample №2 compared to №1.

Laser synthesis of nanocomposite hydrocarbon fuel and CARS diagnostics of its combustion flame

We report an analysis of diffusive combustion in oxygen of a composite fuel formed by the addition of aluminium nanoparticles (NPs) to isopropanol. The process of obtaining Al NPs consisted in laser fragmentation of initially large industrial NPs using radiation of a pulsed nanosecond neodymium laser. The size distribution of Al NPs was determined using a measuring disk centrifuge. The average nanoparticle size was 20 nm, which is confirmed by transmission electron microscopy data. A diagnostic system based on coherent anti-Stokes Raman scattering (CARS) was used to experimentally study the diffusive combustion of composite fuel. The temperature distributions were measured in two mutually orthogonal directions (along the flame and in the transverse direction) in pure isopropanol and in isopropanol with the addition of 0.15 wt % of Al nanoparticles.

3D-Strudel - a novel model-dependent map-feature validation method for high-resolution cryo-EM structures

Recent technological advances in electron cryo-microscopy (cryo-EM) have led to significant improvements in the resolution of many single-particle reconstructions and a sharp increase in the number of entries released in the Electron Microscopy Data Bank (EMDB) every year, which in turn has opened new possibilities for data mining. Here we present a resolution-dependent library of rotamer-specific amino-acid map motifs mined from entries in the EMDB archive with reported resolution between 2.0 and 4.0A. We further describe 3D-Strudel, a method for map/model validation based on these libraries. 3D-Strudel calculates linear correlation coefficients between the map values of a map-motif from the library and the experimental map values around a target residue. We also present "Strudel Score", a plug-in for ChimeraX, as a user-friendly tool for visualisation of 3D-Strudel validation results.

Bacteriophages and their microbial hosts in terrestrial biotopes of Antarctica

Virus diversity in Antarctic biotopes remains understudied. Here, we describe bacteriophages isolated from terrestrial environments, provide data on their natural bacterial hosts and study phage-host systems. Six bacterial isolates (FCKU 539, FCKU 533, FCKU 534, FCKU 538, FCKU 542 and FCKU 540) were recovered and characterized. Isolated bacteria belonged to Pseudomonas genus (Pseudomonas sp., Pseudomonas fluorescens, Pseudomonas putida) with optimal cultivation temperatures of 16–28°C. These bacteria and previously described Bacillus subtilis FCKU 537 were used for analysing virus-host interactions. Six lytic phages were isolated and named P. fluorescens Antarctic virus 1 (PFAV1), P. fluorescens Antarctic virus 2 (PFAV2), P. fluorescens Antarctic virus 3 (PFAV3), P. putida Antarctic virus 4 (PPAV4), Pseudomonas sp. Antarctic virus 5 (PSAV5) and B. subtilis Antarctic virus 6 (BSAV6) in relation to their natural hosts. According to electron microscopy data, these phages belonged to Caudovirales order. Cross-inoculation demonstrated high specificity of all Antarctic phages, which infected only their initial hosts at moderate temperatures. PFAV2 and PFAV3 phages also infected laboratory Pseudomonas savastanoi and P. fluorescens isolates. This paper adds new data on the occurrence and diversity of viruses and their respective bacterial hosts in soil biotopes of Antarctica.

A method for intuitively extracting macromolecular dynamics from structural disorder

Macromolecular dynamics manifest as disorder in structure determination, which is subsequently accounted for by displacement parameters (also called temperature factors, or B-factors) or alternate conformations. Though B-factors contain detailed information about structural dynamics, they are the total of multiple sources of disorder, making them difficult to interpret and thus little-used in structural analysis. We report here an analytical approach for decomposing molecular disorder into a parsimonious hierarchical series of contributions, providing an intuitive basis for quantitative structural-dynamics analysis. We demonstrate the decomposition of disorder on example SARS-CoV-2 and STEAP4 structures, from both crystallographic and cryo-electron microscopy data, and reveal how understanding of the macromolecular disorder leads to deeper understanding of molecular motions and flexibility, and suggests hypotheses for molecular mechanisms.