Our interest in the modifying influence of low-molecular-weight organic compounds on the hydration shell of biopolymers is due to a well-known fact that the former can act as regulators of the ...enzymatic activity changing the hydration shell of the latter. Dioxane was chosen because of its wide application in non-aqueous biocatalysis. In the present study, we investigate the mechanisms of dioxane influence on water of the first hydration layer of the model polypeptides by FTIR-spectroscopy during simultaneous sorption of water-dioxane vapors into the polypeptide films at low water activity. It was found that modification of the hydration shell of the polypeptides studied was mainly due to the indirect ordering of polypeptide secondary structure with the penetration of dioxane molecules under these conditions.
It was found that the enzymes of the coagulation cascade interact with lipid microparticles or microvesicles of natural or artificial origin that circulate in the blood. Such interactions can ...modulate hemostasis. Less is known about the consequences of direct interaction of fibrinogen/fibrin with microvesicles. It was shown in this study with purified systems that the presence of lipid particles of various compositions in a solution can specifically affect the kinetics of fibrin polymerization. Experimental data are presented that indicate that these effects are due to the adsorption of fibrinogen on the surface of microvesicles. In particular, it was shown that the adsorption of fibrinogen at a sufficiently high concentration led to an acceleration of thrombin-induced fibrin polymerization due to the local concentrating effect and the inclusion of microvesicles in the clot structure. Thus, the direct interaction of fibrinogen with microvesicles is a significant factor of hemostasis, which should be considered in the analysis of blood clotting disorders and the development of artificial lipid carriers of drugs.
Numerical characteristics of the aggregation behavior of geminal alkylammonium surfactants in aqueous solutions (the size of micelles, the packing of surfactant molecules, the surface potential, the ...extent of counterion binding) were determined. The formation of mixed micelles geminal surfactant/decylamine resulted in substantial decrease in amine pK
a
; this is the crucial factor determining the strong catalytic effect of the system in ester bond cleavage processes.
The dynamic structure of the micelles of gemini (dimeric) alkylammonium surfactants with different lengths of hydrophobic radicals and polymethylene spacer differing in alkyl substituents of the head ...group and type of counterion are studied by ESR spin probe technique. The use of probes with different localization of spin moiety makes it possible to quantitatively characterize a decrease in micropolarity when going from the surface of micellar aggregates to the core and compare the dynamic structures of the micelles of dimeric and monomeric analogs.
The mechanism of interaction of ficin with a graft copolymer of the sodium salt of carboxymethylcellulose and
N
-vinylimidazole has been investigated by methods of flexible molecular docking, ...infrared and Raman spectroscopy. Functional groups and fragments of graft copolymer molecules, as well as amino-acid residues forming the primary structure of the enzyme that interacts between the ficin and the graft copolymer, have been identified. It was shown that Raman spectroscopy gives more complete representation of fragments of graft copolymer macromolecules interacting with protein compared to infrared spectroscopy. It has been found that the amino-acid residues forming the active site of ficin were involved in the formation of hydrogen bonds and hydrophobic interactions with the graft copolymer, which led to an increase in the proteolytic activity of the conjugated enzyme.
The influence of ethylene glycol (EG) on the kinetics of hydrolysis of N-alpha-benzoyl-L-arginine ethyl ether catalyzed by trypsin encapsulated in sodium bis-(2-ethylhexyl)sulfosuccinate (AOT)-based ...reverse micelles was studied at different temperatures. Ethylene glycol was shown to shift the range of the trypsin activity in the reverse micelles towards higher temperatures. Infrared spectroscopy showed a stabilizing effect of EG on the secondary structure of the protein in the system of reverse micelles. Electron spin resonance spectroscopy showed that the solubilized protein affected the interactions of EG with the polar head groups of AOT and altered the rigidity of the micellar matrix. The results indicate that EG increases the thermostability of the solubilized enzyme in microemulsion media by two mechanisms.
Proton chemical shifts of different atomic groups in sodium dodecyl sulfate (SDS) have been studied by
1
H NMR spectroscopy as functions of surfactant concentration in aqueous solutions. Three ...surfactant concentration ranges of the chemical shifts have been revealed. The first range corresponds to the premicellar solutions, the second one is in the vicinity of critical micelle concentration (CMC
1
), and the third range corresponds to high surfactant concentrations, at which intermicellar interactions play a significant role. The parameters of SDS association (CMC
1
and CMC
2
) determined based on the concentration dependences of the chemical shifts are in satisfactory agreement with the data available from the literature. The concept of critical dimerization concentration (CDC) has been introduced for the first concentration range. The values of CDC and dimerization constant
K
2
(210 × 60 dm
3
/mol) have been estimated within the framework of the two-state model.
Correlation between structural peculiarities of beta-casein and its chaperon-like activity was investigated using the recombinant forms of the protein containing the cysteine residues in the ...polypeptide chain. Aggregation of native and modified forms of β-casein was studied, as well as their chaperon-like activity towards alcohol dehydrogenase thermal aggregation. It has been shown that dimeric and oligomeric forms of β-casein, which are formed due to intermolecular disulfide bonds, significantly differ in their physicochemical and chaperon-like properties from monomeric forms. The thermal stability of alcohol dehydrogenase has been found to depend on the β-casein concentration.
Bacteria most commonly exist in nature in the form of bacterial biofilms, i.e. associations of cells attached to a substrate surrounded by a polymer matrix. Research into biofilm formation and ...functioning is fundamental to the management of microbial associations in ecology, biotechnology and medicine. This task requires the development of analytical approaches capable of providing timely information throughout the life cycle of microbial communities at the same time as maintaining their intact structure. In this paper, we apply scanning electron microscopy and IR spectroscopy as rapid methods for analysing microbial biofilms. To this end, the growth kinetics of a Bacillus subtilis culture cultivated on a solid substrate for 24 h was comparatively studied by the methods of classical microbiology and biochemistry, electron scanning microscopy and Fourier-transform IR spectroscopy. The biofilm morphology was found to vary from a uniform settlement of planktonic cells over the substrate surface at the initial stage of growth (6 h) followed by the accumulation of the extracellular matrix and the formation of microcolonies at the exponential and stationary stage (12–18 h) and a gradual depletion of the matrix at the stage of cell death (24 h). The results of IR spectroscopy were established to agree well with those of biochemical studies, thereby demonstrating the potential of the method for a timely evaluation of the accumulation of proteins, polysaccharides and nucleic acids and for obtaining information about their structural state in the studied biofilm. It is concluded that scanning electron microscopy and Fourier-transform IR spectroscopy can be used for obtaining complementary information about the morphology and chemical composition of microbial biofilms during their cultivation.
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