Analysis of metastable defocusing spectra of lycoctonine bases having 7,8-methylenedioxy groups

The parameters of the MD spectra of the fragmentary ions of 21 lycoctonine alkaloids with 7,8-MDOGs have been investigated. On this basis, the monotypicity of the main fragmentation processes characteristic for the individual groups of compounds have been confirmed. A decrease in the number of common group characteristics of the MD spectra of the ions arising as the result of multistage breakdown processes is caused by alternative methods for their formation. This is not shown only by the doublet nature of the fragmentary ions. The results of a comparison of the MD spectra with the structures of the molecules have confirmed the hypothesis expressed previously concerning the 7,8-MDOG as the center of localization of the charge, competing with the nitrogen atom and facilitating the elimination of various substituents from the diterpene skeleton. A comparison has been made of two methods of evaluating the common nature of the fragmentation reaction: from the energies of the metastable transitions and from the relative intensities of the metastable peaks. The two methods give mutually supplementary information concerning the nature of the fragmentation processes.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 397–407, May–June, 1987.     

Coupling between lysozyme and glycerol dynamics: microscopic insights from molecular-dynamics simulations

We explore possible molecular mechanisms behind the coupling of protein and solvent dynamics using atomistic molecular-dynamics simulations. For this purpose, we analyze the model protein lysozyme in glycerol, a well-known protein-preserving agent. We find that the dynamics of the hydrogen bond network between the solvent molecules in the first shell and the surface residues of the protein controls the structural relaxation (dynamics) of the whole protein. Specifically, we find a power-law relationship between the relaxation time of the aforementioned hydrogen bond network and the structural relaxation time of the protein obtained from the incoherent intermediate scattering function. We demonstrate that the relationship between the dynamics of the hydrogen bonds and the dynamics of the protein appears also in the dynamic transition temperature of the protein. A study of the dynamics of glycerol as a function of the distance from the surface of the protein indicates that the viscosity seen by the protein is not the one of the bulk solvent. The presence of the protein suppresses the dynamics of the surrounding solvent. This implies that the protein sees an effective viscosity higher than the one of the bulk solvent. We also found significant differences in the dynamics of surface and core residues of the protein. The former is found to follow the dynamics of the solvent more closely than the latter. These results allowed us to propose a molecular mechanism for the coupling of the solvent-protein dynamics.     

Effect of the Dopant Nature on the Response of Sensor Arrays Based on Polypyrrole

The effect of the nature of the dopant on the response of a sensor array based on films of polypyrrole under the influence of the vapor of various organic solvents was studied. It was found the electric conductivity of the polymer can both increase and decrease during the action of analytes on electropolymerized films of polypyrrole. It is suggested that the main factors determining the response of polypyrrole are the morphology of the films and the type of charge carriers in the polymer, which depend on the nature of the dopant anion, and also the polarity and nucleophilicity/electrophilicity of the analyte. The responses of polypyrrole and polyaniline are compared, and the effect of the nature of the conducting polymer on them is analyzed. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 265–271, September–October, 2005.     

Mode-coupling study on the dynamics of hydrophobic hydration II: Aqueous solutions of benzene and rare gases

The dynamic properties of both the solute and solvent of the aqueous solution of benzene, xenon and neon are calculated by the mode-coupling theory for molecular liquids based on the interaction-site model. The B-coefficients of the reorientational relaxation and the translational diffusion of the solvent are evaluated from their dependence on the concentration of the solute, and the reorientational relaxation time of water within the hydration shell is estimated based on the two-state model. The reorientational relaxation times of water in the bulk and within the hydration shell, that of solute, and the translational diffusion coefficients of solute and solvent, are calculated at 0-30 degrees C. The temperature dependence of these dynamic properties is in qualitative agreement with that of NMR experiment reported by Nakahara et al. (M. Nakahara, C. Wakai, Y. Yoshimoto and N. Matubayasi, J. Phys. Chem., 1996, 100, 1345-1349, ref. 36), although the agreement of the absolute values is not so good. The B-coefficients of the reorientational relaxation times for benzene, xenon and neon solution are correlated with the hydration number and the partial molar volume of the solute. The proportionality with the latter is better than that with the former. These results support the mechanism that the retardation of the mobility of water is caused by the cavity formation of the solute, as previously suggested by us (T. Yamaguchi, T. Matsuoka and S. Koda, J. Chem. Phys., 2004, 120, 7590-7601, ref. 34), rather than the conventional one that the rigid hydration structure formed around the hydrophobic solute reduces the mobility of water.     

Liesegang pattern formation in kappa-carrageenan gel

We report a new class of the spatial pattern formation process in which the gel plays essential roles. The system studied here is the solution of kappa-carrageenan in which potassium chloride is diffused. The solution transforms into the gel state with the diffusion of potassium chloride. Then the stripe pattern, which is perpendicular to the direction of the diffusion of potassium chloride, appears within the gel. The pattern thus formed in the gel is studied as a function of the concentration of the solution of potassium chloride. We find that the dense region of the stripe pattern consists of the liquid crystalline gel, whereas the dilute region is the amorphous gel. The transition from the amorphous gel to the liquid crystalline gel, hence, occurs in the gel state of kappa-carrageenan. The gel behaves as a pattern-forming substance as well as the supporting medium of the pattern in this system. The period and the thickness of the layers of liquid crystalline gel are analyzed. Both the period and the thickness of the layers are found to depend strongly on the concentration of the solution of potassium chloride.     

脉冲激光溅射下固液界面生长的碳纳米管及其机理初探

以脉冲激光束直接溅射浸在水中的单质碳样品，发现在固液界面也能产生的碳纳米管，实验还发现碳纳米管的形成与样品的结构有密切的关联：石墨的层状结构越完整，碳纳米管的形成越容易，而且石墨层面相对于激光束的取向也会显著地影响碳的生成。     

Electrothermal atomization—the way toward absolute methods of atomic absorption analysis

Considering the currently prevailing opinion that electrothermal atomizers are very susceptible to matrix interferences, an opinion which is contradictory to the optimistic forecasts of the first publications, the general status of the problem to date has been investigated.The first part of the paper deals with the ideal models of the two basic types of electrothermal atomizers, viz., those of the semi-enclosed and those of open type. The graphite cuvette and the Massmann furnace have been selected for discussion in their two commercial versions—the HGA and the CRA—of the first type of atomizers; the West filament and the combined atomizers—rod-in-flame and capsule-in-flame—of the second type. The models describing the distribution of atoms in the absorbing zone have been compared and the data obtained have been used to interpret the experimentally observed differences in the sensitivity of real atomizers.The second section of the paper discusses the conformity of real atomizers relative to ideal models and to the requirement of correctly recording the absorption by means of integrating the pulses. A marked time and space non-isothermality of the commercial atomizers has been established which makes it impossible to measure the integral absorption correctly. The graphite cuvette and the combined atomizers best meet the requirements of the ideal models. On the basis of the data obtained, the possible ways of bringing the semi-enclosed atomizers closer to ideal models have been explored. In this connection, the possibility of using a graphite platform for vaporizing samples in tube furnaces as well as using the temperature-controlled furnace and the pulse heated graphite furnace with a capacitance power supply has been examined. The application of the last method ensures time and space isothermality of the absorbing layer and reduces by 10–100 times the electric power input.The third section of the paper examines the thermochemical laws governing the possible chemical effects arising from the interaction between the analytes, on the one hand, and the furnace walls, the gaseous atmosphere and the matrix, on the other. A critical review has been carried out of the results of some recent publications on investigation of sample vaporization in graphite furnaces, which reveals the fact that the temperature of absorption appearance is rarely connected with the heat of vaporization of the free element. In most instances it is determined by the sum of the heat of decomposition of the non-volatile carbide and the heat of vaporization of the free element. Thermochemical examination of the stability of the compounds formed in the gaseous phase revealed the fact that besides forming monoxides, there is the possibility of forming monocyanides. In addition, the presence of large quantities of halogens causes partial binding of the analyte as gaseous monohalides, mainly monochlorides. In order to eliminate the latter effect, it has been suggested to employ higher atomization temperatures or to bind chlorine in a stable lithium monochloride. The efficiency of the proposed methods has been tested by experiment.Our research has shown that the main reasons for the unsatisfactory status of the problem concerning the matrix effects, are connected with the use of the amplitude (peak) method of recording the absorption, with the time and space non-isothermality of the absorbing layer of the commercial atomizers, and with the formation of gaseous monohalides. All these problems may be eliminated on the basis of theoretically proved and tested methods, some of which are discussed in this paper.     

Role of angular momentum conservation in unimolecular translational energy release: validity of the orbiting transition state theory

The translational kinetic energy release distribution (KERD) for the halogen loss reaction of the bromobenzene and iodobenzene cations has been reinvestigated on the microsecond time scale. Two necessary conditions of validity of the orbiting transition state theory (OTST) for the calculation of kinetic energy release distributions (KERDs) have been formulated. One of them examines the central ion-induced dipole potential approximation. As a second criterion, an adiabatic parameter is derived. The lower the released translational energy and the total angular momentum, the larger the reduced mass, the rotational constant of the molecular fragment, and the polarizability of the released atom, the more valid is the OTST. Only the low-energy dissociation of the iodobenzene ion (E approximately 0.45 eV, where E is the internal energy above the reaction threshold) is found to fulfill the criteria of validity of the OTST. The constraints that act on the dissociation dynamics have been studied by the maximum entropy method. Calculations of entropy deficiencies (which measure the deviation from a microcanonical distribution) show that the pair of fragments does not sample the whole of the phase space that is compatible with the mere specification of the internal energy. The major constraint that results from conservation of angular momentum is related to a reduction of the dimensionality of the dynamics of the translational motion to a two-dimensional space. A second and minor constraint that affects the KERD leads to a suppression of small translational releases, i.e., accounts for threshold behavior. At high internal energies, the effects of curvature of the reaction path and of angular momentum conservation are intricately intermeddled and it is not possible to specify the share of each effect.     

Orientation and distance dependent chiral discrimination in the first step of the aminoacylation reaction: Integrated molecular orbital and semi-empirical method (ONIOM) based calculation

Aminoacylation is a vital step in natural biosynthesis process of peptide and is the key step in correlating the realm of protein with the RNA world. Incorrect aminoacylation might lead to misacylation of d-amino acid in the tRNA which might cause synthesis of a hetero-peptide rather than natural homopeptide leading to the altered functionality of the peptide. However, the accuracy of this process is remarkable and leads to the attachment of the correct enantiomer of the amino acid with their cognate tRNA. Thus, the chiral discrimination is stringent. In the present work, we presented a combined ONIOM (ab initio/semi-empirical) study of the chiral discrimination in the first step of aminoacylation reaction based on a model of crystal structure of the oligomeric complex of histidyl-tRNA synthetase (HisRS) from Escherichia coli complexed with ATP and histidinol and histidyl-adenylate. The study reveals that the molecular mechanism of the chiral discrimination involves the amino acid, ATP as well as surrounding residues of the synthetase. Several factors are noted to be responsible for discrimination and explain the high level of stereospecificity of the process. The chirality of the amino acid of the substrate and its (principally) electrostatic interaction with the ATP is important for discrimination. The distance and orientational changes involved in the approach of the d-His towards the ATP is energetically unfavorable. The charge distributions on the His and ATP are important for the discrimination. Removal of the charges in the model drastically reduces the discrimination. Restricted nature of the mutual orientation within the cavity of the active site where the His and ATP are located during the change in orientation for the approach to form the adenylate makes the resultant interaction profile as different for l-His and d-His also influences chiral discrimination. The analysis of the transition state structure revealed that alteration of the chirality of the His destabilize the transition state by removing the favorable electrostatic interaction between the Glu-83 and NH₃⁺ group of the His substrate. The proximity of the surrounding residues as present in the active site of the synthetase with the His and ATP (the separation is of nanometer range) has influence of discrimination. The study provides a molecular mechanism of the retention of biological homochirality.     

On the contact conditions for the charge profile in the theory of the electrical double layer for nonsymmetrical electrolytes

In this paper, we generalize a recently derived expression of the contact value of the charge profile for the case of nonsymmetrical electrolytes. For the electrolytes with a single type of cation and anion, this relation can be presented as the sum of three contributions. One of them is the normal component of the Maxwell electrostatic stress tensor. The second one is the surface electrostatic property, which is defined as the integral of the product of the gradient of the electrical potential and the density distribution function of coions. The third term is the bulk contribution, which is defined by the sum for anions and for cations of the product of their charge and their partial pressure. For noncharged surfaces, only the last two terms are present and have the same sign in the case of size asymmetry. In the case of charge asymmetry, the contact value of the charge profile is the result of the competitions of bulk and surface terms in which the bulk term is dominant. Using both the contact theorems for the density and the charge profiles, the exact expressions for the contact values of the profiles of coions and counterions are obtained and some related properties are discussed. A semiempirical expression of the contact value of the charge profile is discussed in relation to our exact result.     

Capillary osmosis through porous partitions and properties of boundary layers of solutions

According to the theory of one of the authors, when the adsorption layer on a solid surface in contact with a solution is mobile, the gradient of concentration of the solution along the solid surface causes capillary-osmotic slip in addition to diffusional flow of the liquid. In the case of porous partitions separating solutions of different concentrations, slip along the pore walls causes convective transfer of the solution, i.e., capillary osmosis. A special unit has been constructed to study this phenomenon and the velocity of capillary-osmotic flow is measured with the aid of radioactive indicators. Formulas are derived for the arising capillary-osmotic flow of substance, making it possible, by introducing a correction for the diffusional flow, to calculate the velocity of capillary-osmotic slip.

There is usually on the surface of glass both a double layer due to the dissociated part of the solution, and an adsorption layer of the undissociated part of the solution. Thus, under real conditions there are flows due both to the double layer on the glass surface and to the mobile part of the adsorption layer of the undissociated part of the solution. Knowing the values of the capillary-osmotic slip and the zeta-potential, one can calculate which of these processes predominates. For this purpose capillary-osmotic flows through Shott filters of certain aqueous solutions and nonaqueous mixtures are measured simultaneously with their zeta-potentials, on the surface of Shott glass. It is shown that for these solutions the flows caused by the double layer at the glass surface are small compared to those due to the mobile part of the adsorption layer of the undissociated part of the solution.

Expressions are obtained for positive and negative adsorption of the undissociated part of the solution, relating the capillary-osmotic velocity to the constant of effective molecular attraction between the dissolved molecules and the glass.

Hence, the constants of molecular attraction between the molecules and the glass, and the average distance between the solute molecules and the plane of slip are calculated from experimental results for the solutions studied.

Thus, the experimental method and calculations proposed may be used for analyzing the structure of adsorption layers at solid-solution interfaces.     

Simple quantum-mechanical model of the elementary event of organic nucleophilic substitution reactions in the condensed phase

A semiempirical model is proposed for the elementary event of nucleophilic S_N2 substitution in alkyl halides. An analysis was made of the factors which determine the activation energies of the processes, i.e., the energy of approach of the reagents, the energy of extension of the chemical bonds, the energy of reorganization of the medium, and the equilibrium energy of the elementary event. The contributions from the first three energy parameters are commensurable, and the energy of approach has a predominant role. The role of the equilibrium energy, determined by the solvation energy of the reacting ions and the energy of the formed and broken chemical bonds, involves the creation of thermally neutral conditions for the reactions. The effective potential surfaces of the repulsive interaction between the halide ions and the methyl halides were constructed in terms of the model. The tunneling factor and the kinetic isotope effect for the lightest reacting particle in the reaction series (the fluoride ion) were also determined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 417–424, July–August, 1985.     

N-异丙基丙烯酰胺对细乳液聚合制备纳米胶囊形态的影响

将N-异丙基丙烯酰胺(NIPAAm)引入小分子烃为模板的苯乙烯细乳液聚合法制备纳米胶囊的体系.水相引发形成的聚异丙基丙烯酰胺(PNIPAAm)低聚物自由基在聚合温度下(大于其最低临界溶解温度)析出并被苯乙烯细乳液液滴吸附,在热力学推动力和静电斥力的共同作用下,PNIPAAm低聚物倾向于分布在液滴和水的界面上,使液滴界面成为主要的聚合场所,单体从液滴内部向界面扩散补充消耗的单体,生成的聚合物在液滴界面上析出,包覆小分子烃液滴,最终得到纳米胶囊.通过透射电镜观察粒子形态和大小;利用接触角测定仪测定了细乳液液滴的表面张力.考察了NIPAAm用量、油溶性单体/小分子烃比例、交联剂用量及乳化剂和引发剂对的种类对胶囊形态的影响.     

Properties of free surface of water-methanol mixtures. Analysis of the truly interfacial molecular layer in computer simulation

Molecular dynamics simulations of the vapor-liquid interface of water-methanol mixtures of five different compositions were performed on the canonical (N,V,T) ensemble at 298 K. In addition, the vapor-liquid interface of the two neat systems was simulated, as well. The obtained configurations were analyzed by means of the novel identification of truly interfacial molecules method, which provides a full list of the molecules that are right at the surface (i.e., at the boundary of the two phases). The molecular level roughness of the surface, the adsorption of the methanol molecules at the surface layer, the orientation of the surface molecules, the residence time of the molecules at the surface layer, as well as the surface aggregation of the molecules were analyzed in detail. Both the frequency and the amplitude of the surface roughness were found to become larger with an increasing methanol content. This effect was found to be stronger for the amplitude, which falls in the range of 2-4 A, depending on the composition of the system. Methanol was found to be adsorbed at the surface layer, being preferentially at the humps of the molecularly rough surface. Surface methanol prefers to orient in such a way that the O-CH(3) bond remains perpendicular to the macroscopic plane of the surface, pointing the methyl group to the vapor phase. The main orientational preference of the water molecules is to lie parallel to the surface. Methanol was found to remain considerably longer at the surface layer of the mixed systems than water. Thus, contrary to the fact that the residence times of the two molecules were found to be rather similar to each other at the surface of their neat liquids, the residence time of the methanol molecules was an order of magnitude larger than that of water molecules at the surface of their mixtures. A strong lateral microscopic segregation of the molecules was observed at the surface layer; the minor component of the system (irrespective of whether it was water or methanol) was found to form two-dimensional aggregates, leaving the rest of the surface empty for the major component. The effect of the vicinity of the vapor phase on the properties of the molecules was found to vanish very quickly: the composition of the second layer as well as the properties of the molecules of this layer (e.g., dynamics and orientation) did not differ considerably from those in the bulk liquid phase.     

Ab Initio Equilibrium Geometry and Vibrational Spectroscopic Study of 25,26,27,28-tetrahydroxycalix[4]arene

The aim of this work was to present a comprehensive vibrational spectroscopic study of 25,26,27,28-tetrahydroxycalix[4]arene. For this purpose, quantum chemical calculations were carried out at the ab initio HF/4-31G* level, as a consequence of the great size of the molecule. In the frame of these calculations, the symmetry of the molecule was investigated. Trying C 4v , C 2v , and C s symmetries as input, the geometry optimization, however, pointed to the C 2 configuration. In the latter case, all the calculated vibrational frequencies were greater than zero, and therefore the equilibrium geometry could be identified. Medium and far infrared as well as Raman spectra of the compound were measured. On the basis of the calculated force constants and geometric parameters, normal coordinate analysis was applied for the interpretation of the experimental vibrational spectra. Problems arose with the choice of the internal coordinates of the molecule, which are important from the point of view of the internal macrocycle ("lower rim") of the molecule. On the basis of the theory of redundant coordinates, a program was written for choosing the coordinates of this 16-membered cycle. Full interpretation of the vibrational fundamentals of the compound is presented. Several force constant matrix elements have surprisingly high values. As a result of the normal coordinate analysis, the relative rigidity of the lower rim was concluded. Ab initio calculations and assignment of the vibrational spectra of 25,26,27,28-tetrahydroxycalix[4]arene based on the calculations are presented.     

Application of pulsating overpotential regime on the formation of copper deposits in the range of hydrogen co-deposition

Electrodeposition of copper by pulsating overpotential (PO) regime in the range of hydrogen co-deposition was examined by scanning electron microscopy. It was found that the increase of the pause-to-pulse ratio produced a strong effect on the morphology of electrodeposited copper. Honeycomb-like copper structures were formed with the pause-to-pulse ratios up to 5. Up to this value of the pause-to-pulse ratio, the diameter of the holes formed by attached hydrogen bubbles was decreasing, while their number was increasing by the application of PO regime. The compactness of the formed honeycomb-like structures was also increasing with the increasing pause duration. The increase of the pause-to-pulse ratio suppressed a coalescence of neighboring hydrogen bubbles. Copper dendrites in the interior of the holes and at their shoulders were formed with the higher pause-to-pulse ratios. The size of the formed dendrites, as well as their number, increased with the increasing pause duration. Depth of holes was decreasing with the increasing pause duration. The increased compactness of the obtained structures was explained by the use of a set of equations describing the effect of square-wave PO on electrodeposition process.     

Application of 1H NMR spectroscopy method for determination of characteristics of thin layers of water adsorbed on the surface of dispersed and porous adsorbents

The paper presents 1H NMR spectroscopy as a perspective method of the studies of the characteristics of water boundary layers in the hydrated powders and aqueous dispergated suspensions of the adsorbents. The method involves measurements of temperature dependence proton signals intensity in the adsorbed water at temperatures lower than 273 K. Free energy of water molecules at the adsorbent/water interface is diminished due to the adsorption interactions causing the water dosed to the adsorbent surface freezes at T < 273 K. Thickness of a non-freezing layer of water can be determined from the intensity of the water signal of 1H NMR during the freezing-thawing process. Due to a disturbing action of the adsorbent surface, water occurs in the quasi-liquid state. As a result, it is observed in the 1H NMR spectra as a relatively narrow signal. The signal of ice is not registered due to great differences in the transverse relaxation times of the adsorbed water and ice. The method of measuring the free surface energy of the adsorbents from the temperature dependence of the signal intensity of non-freezing water is based on the fact that the temperature of water freezing decreases by the quantity which depends on the surface energy and the distance of the adsorbed molecules from the solid surface. The water at the interface freezes when the free energies of the adsorbed water and ice are equal. To illustrate the applicability of the method under consideration the series of adsorption systems in which the absorbents used differed in the surface chemistry and porous structure. In particular, the behaviour of water on the surface of the following adsorbents is discussed: non-porous and porous silica (aerosils, silica gels); chemically and physically modified non-porous and porous silica (silanization, carbonization, biopolymer deposition); and pyrogeneous Al2O3 and aluminasilicas. The effect of preliminary treatment of the adsorbent (thermal, high pressure, wetting with polar and non-polar solvents) on the characteristics of the structurized water layers was discussed. The influence of the adsorbent porous structure on the free energy of the adsorbed water was also studied. The discussion of the obtained results was made.     

New aspects of migration and flame retardancy in polymer nanocomposites

Annealing of pristine polypropylene blended with the organomontmorillonite (OMMT) at temperatures of 180-340 °C under a stream of nitrogen and of nitrogen-air mixtures is investigated. The oxidative annealing brings about the dispersion of the OMMT in the polypropylene and the formation of a nanocomposite structure. This is evidenced by the increase in the interlayer distance ‘d’ as measured by small angle XRD, with time of annealing and with the weight percent of air. This indicates progressive intercalation of the polymeric matrix into the clay gallery and subsequently exfoliation. The degree of exfoliation is estimated by the extent of migration determined spectroscopically on the surface of the annealed sample. The accumulated clay on the surface due to migration hinders the penetration of the oxygen into the annealing melt as expressed by the decrease in the rate of migration with the increase in the air concentration. This indicates the increase in ageing and storage stability of nanocomposites with increase in the extent of migration. The extent of migration is proportional to the polar carbonyl groups formed on the matrix. The energy of activation of the migration was found to be 37.82 kJ/mol indicating that the rate-determining step of migration is diffusion controlled reaction. The penetration of oxygen into the melt is the first of five steps, followed by oxidation, intercalation, exfoliation and migration. Monitoring the migration with increase in the temperature enables the observation at 275 °C of the transition of the nanocomposite structure to noncolloidal microcomposite. Increasing the annealing temperature above 300 °C brings about a slow, low-temperature combustion and formation of a new kind of char on the surface of the sample.     

坚膜反应对染印法空白片性能的影响

本文研究了在染印法空白片的各种坚膜条件下媒染层的物理机械性能和染印性能,包括媒染层的断裂强度、空白片的膨胀度、染色密度和线格清晰度。铬矾坚膜的效果用媒染层中铬的含量和媒染层经水萃取后所得交联物含量来表示。在此基础上计算出用铬矾坚膜的媒染层的交联密度。为排除空白片中乳剂层的干扰,采用了单独处理媒染层的方法。得到了在本实验中获得空白片最佳清晰度和最佳物理机械性能的条件,并对媒染层中主要物质分子间的相互关系进行了探讨。     

Model for solvent viscosity effect on enzymatic reactions

The solvent viscosity dependence for enzymatic reactions is discussed. We suggest the interpretation of the phenomenon that requires neither a modification of the Kramers’ theory nor that of the Stokes law. We assume that an enzyme solution is an ensemble of samples with different values of the viscosity for the movement of the system along the reaction coordinate. We quantify the extent of this difference by some parameter, introduce heterogeneity in our system with the help of a distribution over this parameter and find the solution of the integral equation for the function of the distribution. All parameters of the model are related to experimentally observable values. The meaning of fractional exponents appears to be the characteristic for the behavior of the distribution. Our approach yields the existence of the limit value for the fractional power exponent with the decrease of cosolvent molecular weight in agreement with known experimental data.