Cell theory, as formulated by Theodor Schwann in 1839, introduced the idea that the cell is the main structural unit of living nature. Later, in solving the problem of cell multiplication, Rudolf ...Virchow expanded the cell theory with a postulate: all cells only arise from pre-existing cells. But what did the very first cell arise from? This paper proposes extending the Virchow's law by the assumption that between the nonliving protocell and the first living cell the continuity of fundamental physical properties (the principle of invariance of physical properties) is preserved. The protocell is understood here as a cell-shaped physical system on the basis of the self-organized biologically significant prebiotic macromolecules, primarily peptides, having a potential to transform into the living cell. Biophase is considered as the physical basis of the membraneless protocell, the internal environment of which is separated from the external environment due to the phase of adsorbed water. The evidence is given that the first protocells may have been formed on the basis of intrinsically disordered peptides. Data on the similarity of the physical properties of living cells and the following model systems are given: protein and artificial polymer solutions, coacervate droplets, and ion-exchange resin granules. Available data on the similarity of the physical properties of cell models and living cells allow us to rephrase the Virchow's postulate as follows: the physical properties of a living cell could only arise from pre-existing physical properties of the protocell.
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A comparative study of anticorrosive inhibited polymer films on the tungsten surface formed from an aqueous solution of inhibited formulations (INFOR) containing organosilane and corrosion inhibitors ...was carried out by means of the prolonged exposure of a tungsten product in a modifying solution and by the method of cataphoretic deposition (CPD). Depending on the method of forming films on tungsten, the molecular organization of the near-surface layers was studied (ATR-FTIR), and the subprimary structure of the films was explored (TEM). The optimal modes of cataphoresis deposition (CPD duration and current density applied to the sample) for the formation of a protective inhibited polymer film on the tungsten surface were established by means of SEM. The energy and thermochemical characteristics (sessile drop and DSC methods), as well as operational (adhesive behavior) and protective filming ability (EIS and corrosion behavior), according to the method of formation of inhibited polymer film, were determined. Based on the combined characteristics of the films obtained by the two methods and the deposition modes, the CPD method showed better performance than the electroless dipping method.
In the present work, the effect of divinylbenzene (DVB) on the kinetics of post-radiation chemical graft polymerization styrene (St) on polyethylene (PE) film and its structural and morphological ...features were investigated. It has been found that the dependence of the degree of polystyrene (PS) grafting on the DVB concentration in the solution is extreme. An increase in the rate of graft polymerization at low concentrations of DVB in the solution is associated with a decrease in the mobility of the growing chains of PS. A decrease in the rate of graft polymerization at high concentrations of DVB is associated with a decrease in the rate of diffusion of St and iron(II) ions in the cross-linked network structure of macromolecules of graft PS. A comparative analysis of the IR transmission and multiple attenuated total internal reflection spectra of the films with graft PS shows that graft polymerization of St in the presence of DVB leads to the enrichment of the film surface layers in PS. These results have been confirmed by the data on the distribution of sulfur in these films after sulfonation. The micrographs of the surface of the grafted films show the formation of cross-linked local microphases of PS with fixed interfaces.
Diffusion coefficients of ions and water have been measured in two- and three-component concentrated (“water-in-salt”) aqueous solutions of KOAc and LiOAc, which were proposed as new electrolytes for ...water-based Li-ion batteries. It was demonstrated that the diffusion coefficient for acetate anion is greater than for lithium cation one in the KOAc-containing solutions and the difference grows under increasing concentration of potassium acetate. Water diffusion is also faster comparing with lithium cation and acetate anion in all solutions studied. Temperature dependences of spin–lattice relaxation rates (1/
T
1
) of
1
H,
7
Li, and
39
K nuclei have been measured for both ions and water. The dependences do not reach their maxima for most samples, and only for acetate anion in sample IV (31.9 mol KOAc–8.0 mol LiOAc–H
2
O) it turned out to be possible the reliable calculation of the rotational correlation time
τ
c
. Comparison of the translational (via D) and rotational (via
τ
c
) mobility of the acetate anion near the eutectic point showed that the Stokes–Einstein relation is valid for this solution only in a small high-temperature part of the studied range, but not for the lower temperatures.
More than five hundred images of individual macromolecules of random styrene-butadiene copolymers and styrene-isoprene block copolymers dissolved in a polystyrene matrix were analyzed. The presence ...of density fluctuations inside the macromolecular coil has been established. Within the framework of the model of harmonic oscillations, the radial distribution of such density fluctuations is estimated.
The ionic liquid
propylammonium nitrate
(PAN) was elaborated in the present study applying NMR. Temperature dependences of
1
H and
13
C spin–lattice relaxation rates and diffusion coefficients were ...measured to describe molecular mobility in PAN. It was discovered that the temperature dependences of the relaxation rates do not have a maximum. An approach to solve the problem of finding a “hypothetical” maximum was applied. Verification of the correctness of the approach on the examples of temperature dependences with a pronounced real maximum was performed. As a result, the correlation times for selected molecular groups of PAN were calculated. Analyzing the data obtained one can conclude that the translational and rotational degrees of freedom in PAN are weakly correlated. The translational motion “slows down” more strongly with the decrease in temperature.
Since the 1880s, the concept of compartmentalizing through membranes has taken a firm place in cell physiology and has defined the objects, methods, and goals of physiologists’ research for decades. ...A huge mass of biologists know about the important role of intra-membrane pumps, channels, and lipids, and various hypotheses about the origin of life often begin with explanations about how the lipid membrane occurred, without which it is impossible to imagine the origin of a living cell. Against this background, there was a dissonance of statements that there are membraneless organelles in the cell, the functions of which are rapidly expanding under our eyes. Physically, they are similar to coacervate droplets, which from time to time were used to explain the origin of life, and now the coacervates are being more and more often discussed when describing the physics of the nucleus and cytoplasm of modern cells. However, ideas about the coacervate nature of cytoplasm/protoplasm originated in the first half of the 19th Century, when the contents of cells were likened to jelly, but this approach gradually faded into the shadows. Nevertheless, limited research in this area continued and was completed in the form of a membraneless cell physiology. Now that the focus of attention has turned to membraneless compartmentalization, it’s time to remember the past. The sorption properties of proteins are the physical basis of membraneless cell because of water adsorbed by proteins changes the physical state of any biomolecular system, from supramolecular and subcellular structures to the cell as a whole. A thermodynamic aqueous phase is formed because adsorbed water does not mix with ordinary water and, in this cause, is separated from the surrounding solution in the form of a compartment. This article discusses the fundamental physical properties of such a phase – a biophase. As it turned out, the Meyer–Overton rule, which led to the idea of a lipid membrane, also applies to membraneless condensates.
The amino acid sequences of the coat proteins (CPs) of the potexviruses potato virus X (PVX) and alternanthera mosaic virus (AltMV) share ~40% identity. The N-terminal domains of these proteins ...differ in the amino acid sequence and the presence of the N-terminal fragment of 28 residues (∆N peptide) in the PVX CP. Here, we determined the effect of the N-terminal domain on the structure and physicochemical properties of PVX and AltMV virions. The circular dichroism spectra of these viruses differed significantly, and the melting point of PVX virions was 10-12°C higher than that of AltMV virions. Alignment of the existing high-resolution 3D structures of the potexviral CPs showed that the RMSD value between the C
α
-atoms was the largest for the N-terminal domains of the two compared models. Based on the computer modeling, the ∆N peptide of the PVX CP is fully disordered. According to the synchrotron small-angle X-ray scattering (SAXS) data, the structure of CPs from the PVX and AltMV virions differ; in particular, the PVX CP has a larger portion of crystalline regions and, therefore, is more ordered. Based on the SAXS data, the diameters of the PVX and AltMV virions and helix parameters in solution were calculated. The influence of the conformation of the PVX CP N-terminal domain and its position relative to the virion surface on the virion structure was investigated. Presumably, an increased thermal stability of PVX virions vs. AltMV is provided by the extended N-terminal domain (ΔN peptide, 28 amino acid residues), which forms additional contacts between the adjacent CP subunits in the PVX virion.
Cross-linking of polysaccharides by metal ions provides polymer gels highly required by industrial applications. In this article, we study the rheological properties and microstructure of solutions ...of a stiff anionic polysaccharide xanthan cross-linked by chromium (III) ions, and we demonstrate that their properties are highly sensitive to the preparation pH. Stable gels are obtained in a wide range of pH from 2.4 to 7.8. The maximum elastic modulus is observed for the gels made at pH 6.3, and by freeze-fracture transmission electron microscopy it is shown that they are characterized by the most dense network structure. However, out of this pH interval, no gelation is observed. At low pH (< 2.4) it is due to high protonation of carboxylic groups of xanthan preventing their interaction with chromium ions, and to the disappearance of oligomeric ions, which are effective in cross-linking. At high pH (> 7.8) the absence of gelation is caused by the transformation of reactive chromium ions into insoluble chromium hydroxide. At the same time, for the gels initially formed at pH 6.3, subsequent change of pH to strongly acidic (1.4) or basic (8.9) medium does not affect appreciably their properties, meaning that chromium cross-links are stable once they are formed. These observations open a reliable route to produce polysaccharide gels with required mechanical properties in a wide pH range where they initially cannot be prepared. It is also shown that the increase of pH to 6.3 of the initially ungelled solution prepared at pH 1.5 results in gelation. This effect offers a facile way for delayed gelation of polysaccharides, which is especially required by oil industry.
It has been found that a high electrical conductivity of 63.1%, the International Annealed Copper Standard (IACS), and high mechanical properties are achieved by the initial aluminum alloy after ...undergoing four cycles of the severe plastic deformation (SPD) process. It has been found that when TiB2 particles are introduced into aluminum and the samples are subject to SPD, the mechanical characteristics of the aluminum alloy are improved. Microhardness (HV) increases from 329 to 665 MPa, yield strength (YS) increases from 38 to 103 MPa, and ultimate tensile strength (UTS) increases from 73 to 165 MPa while maintaining the initial electrical conductivity of cast aluminum without reinforcing particles (53.9–54.1% IACS).
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