Dilute Solution Properties Research Articles

Single-File Water Permeation through Aquaporin Channels

A diffusive model of osmosis is presented that explains currently available experimental data. It makes predictions that distinguish it from the traditional convective flow model of osmosis, some of which have already been confirmed experimentally and others have yet to be tested. It also provides a simple kinetic explanation of Raoult's law and the colligative properties of dilute aqueous solutions. The diffusive model explains that when a water molecule jumps from low to high osmolarity at equilibrium, the free energy change is zero because the work done pressurizing the water molecule is balanced by the entropy of mixing. It also explains that equal chemical potentials are required for particle exchange equilibrium in analogy with the familiar requirement of equal temperatures at thermal equilibrium. These are topics that should be considered for inclusion in the redesign of introductory physics courses for the life sciences (IPLS). The diffusive model also makes detailed predictions for the unidirectional fluxes through single-file aquaporins that can be tested experimentally or via molecular dynamics simulation. Predictions are made for both non-equilibrium and equilibrium simulations in which there may or may not be a water chemical potential difference across the membrane. The effects of both osmolarity and hydrodynamic pressure differences are included in the model. DUE-0836833 http://circle4.com/biophysics

非線状半屈曲性高分子の稀薄溶液物性—剛直鎖からランダムコイルへのクロスオーバー

非線状高分子，とくに，星型および環状高分子の稀薄溶液物性に対する鎖の固さの影響をKratky–Porodのみみず鎖(KP鎖)モデルを用いて理論的あるいは計算化学的に検討した．3本腕星型KP鎖について，剛直性パラメータλ－1を単位に測った還元鎖長λLの関数として，星型鎖と対応する線状鎖の固有粘度[η]，並進拡散係数(有効流体力学的半径)，および良溶媒条件下の第二ビリアル係数A2の各比の挙動を検討した．[η]に関しては，4本腕星型KP鎖の場合も同様の検討を行った．環状KP鎖について，平均二乗回転半径，[η]，および散乱関数に対する鎖の固さおよび環状鎖の結び目の型に対する位相幾何学的拘束の影響を検討した．さらに，環状鎖間の分子間位相幾何学的相互作用を反映するΘ状態におけるA2に関する結果を示し，Θ溶媒中における環状アタクチックポリスチレンに対する文献データとの比較を行った．

Thermodynamic properties of dilute solutions of various elements in liquid lead

Published evidence about the thermodynamic properties of dilute solutions of various elements in liquid lead are reviewed. Particular attention is given to the characteristic impurities in lead smelted both from ores and from secondary raw materials and also to alkali and alkaline-earth metals whose behavior is of interest for electrolysis processes with a liquid lead cathode. In experimental data processing, the activity coefficient of a component at infinite dilution was estimated by using, when necessary, the analytical representation of the concentration dependence of thermodynamic functions and various graphical extrapolation procedures.

Low-Temperature Transport Properties of Very Dilute Classical Solutions of $$^3$$ 3 He in Superfluid $$^4$$ 4 He

We report microscopic calculations of the thermal conductivity, diffusion constant, and thermal diffusion constant for classical solutions of \(^3\)He in superfluid \(^4\)He at temperatures \(T \lesssim 0.6\) K, where phonons are the dominant excitations of the \(^4\)He. We focus on solutions with \(^3\)He concentrations \(\lesssim \) \(10^{-3}\), for which the main scattering mechanisms are phonon–phonon scattering via 3-phonon Landau and Beliaev processes, which maintain the phonons in a drifting equilibrium distribution, and the slower process of \(^3\)He–phonon scattering, which is crucial for determining the \(^3\)He distribution function in transport. We use the fact that the relative changes in the energy and momentum of a \(^3\)He atom in a collision with a phonon are small to derive a Fokker–Planck equation for the \(^3\)He distribution function, which we show has an analytical solution in terms of Sonine polynomials. We also calculate the corrections to the Fokker–Planck results for the transport coefficients.

Effect of dilute solutions of biologically active substances on cell membranes

The article presents data on changes in physicochemical properties of different biological membranes (plasmatic, microsomal, synaptosomes) under the action of biologically active substances, which are different in their chemical structure and the mechanism of action (natural and synthetic antioxidants, thyrotropin--releasing hormone, phorbol esters), in the wide range of concentrations (10(-22)-10(-3)M). Dose dependences of the effect of biologically active substances on the activity of membrane-bound enzymes, lipid peroxidation, the structural state of the various regions of the lipid bilayer of membranes have been obtained and analyzed in terms of their formal generality of polymodality, number and position of the maxima, a sign change of the effect. An attempt to explain the mechanism of each of the observed peaks in these curves has been made. The maximum in the range of relatively high "physiological" concentrations (10(-3)-10(-7)M) is associated with introduction of biologically active substances into biomembranes. In this study maxima in the range of ultra-low doses (10(-11)-10(-16)M) and "apparent" concentrations -(10(-18)M), where the presence of biologically active substance molecule in a reaction volume is probabilistic in nature, are explained by physicochemical properties of diluted biologically active substances solutions. This conclusion is based on our data on the changes in IR spectra of aqueous solutions of biologically active substances and the results obtained by academician A.I. Konovalov et al. concerning the physicochemical properties of dilute solutions of biologically active substances (conductivity, surface tension, charge), due to the formation of so-called "nanoassociates" from biologically active substance molecule and numerous number of water molecules. The nanoassociates formation and biological effect disappear if the low concentration solutions are kept in a special shielded permalloy container protecting its contents from external electromagnetic field. Thus, nanoassociates are the material carriers of the unique ability of the ultra-low doses of biologically active substances to exhibit biological effects.

Evaluation of the scaling parameters of lignin macromolecules

The results of a study of the topological structure of lignin from Betula pendula birch twigs are presented. The molecular properties of dilute solutions of lignin in DMF were investigated by the sedimentation velocity and translational diffusion methods, and by viscosimetry. The molecular weights of fractions, the conformational parameters, and the Tsvetkov-Klenin hydrodynamic invariant were determined. Correlations between the hydrodynamic, conformational, and fractal parameters of lignin were studied. Lignin from birch twigs was found to be a randomly branched polymer.

Study of the structure of lignin macromolecules by molecular hydrodynamics methods

The hydrodynamic properties of dilute solutions of lignin isolated from Rhodiola rosea L. plant roots were studied. The values of intrinsic viscosity and coefficients of translational diffusion and sedimentation were determined. It was shown that the scaling principle was fulfilled, and the parameters of the Mark-Kuhn-Houwink equation were calculated. The findings indicate that lignin from Rhodiola rosea L. belongs to the universal class of star-like polymers.

The influence of molar mass on rheological and dilute solution properties of poly(butylene succinate)

ABSTRACTThe fundamental rheological properties of a wide molar mass Mw range of poly(butylene succinate)s (PBSs) are investigated. For entangled samples and a reference temperature of 140°C, the shear viscosity is described by the Carreau–Yasuda model. The plateau modulus is estimated at 1.5 × 105 Pa, the average activation energy of PBS melt is , and the critical molar mass for entanglement Mc is found to be 16,000 g mol−1 (PS equivalent). The dilute solution properties of PBS are also studied. A size exclusion chromatography equipped with a triple detection system is used to estimate the Mark–Houwink–Sakurada (MHS) parameters of PBS in solution in chloroform at 30°C. The exponent a and the coefficient K of the MHS relationship are found to be 0.71 ± 0.1 and 39.94 × 10−5 ± 6.31 × 10−5 dL g−1(g mol−1)−a, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40887.

Synthesis and dilute aqueous solution properties of ester functionalized cationic gemini surfactants having different ethylene oxide units as spacer

New series of ester functionalized quaternary ammonium gemini surfactants having different ethylene oxide units as spacer have been synthesized and investigated for their aggregation behavior and thermodynamic properties of micellization by surface tension, conductivity, and fluorescence methods. The critical micelle concentration (cmc) of these gemini surfactants increases with the increase in the length of polar hydrophilic ethylene oxide spacer. The micellization process has been found to be entropy-driven and dependent on both the tendency of the hydrophobic group of the surfactants to transfer from aqueous environment to interior of micelle as well as the rearrangement of flexible ester-linked ethylene oxide units (hydrophilic spacer) into aqueous phase. The polar ester functional groups and pairs of nonbonding electrons on oxygen atom of ethylene oxide spacer form hydrogen bonding with water molecules enhancing their solubility in aqueous system.

Dilute solution properties of semiflexible star and ring polymers

Our recent theoretical and/or Monte Carlo (MC) studies of dilute solution properties of semiflexible stars and rings are briefly summarized. The theoretical results for the intrinsic viscosity [η] of the Kratky–Porod (KP) wormlike three- and four-arm stars are shown, and effects of chain stiffness on [η] of the stars are examined. A comparison of the results for [η] with those for the effective hydrodynamic radius and the second virial coefficient A2 in a good solvent was made for the semiflexible three-arm stars. It was found that [η] is the most suitable object of study to examine the effects of chain stiffness on average chain dimensions of the stars. As for the rings, the MC results for A2 of the ideal KP rings, which is related to the intermolecular topological interactions, are presented and then compared with the data in the literature for ring atactic polystyrene (a-PS) at Θ for large molecular weight M (1 × 104−6 × 105). Even for ring a-PS in such a range of M, the effects of chain stiffness were still remarkable. The effects of the intramolecular topological constraints on the mean-square radius of gyration and the scattering function of the KP rings are also discussed. Theoretical and/or Monte Carlo studies are made of dilute solution properties of semiflexible stars and rings based on the Kratky–Porod wormlike chain model. The behavior of the properties in the range of the crossover from the rigid limit to the random-coil one is clarified. It is shown that effects of chain stiffness affect largely the dilute solution behavior not only of linear polymers but also of stars and rings, and are still remarkable even for typical flexible polymers with large molecular weight (∼105).

Influence of temperature, mono- and divalent cations on dilute solution properties of sage seed gum

The functional properties of food hydrocolloids are remarkably affected by the quality of solvent/cosolutes and temperature in a food system. In this paper, dilute solution properties of sage seed gum (SSG) as a function of salt type (NaCl, KCl, MgCl2 and CaCl2), salt concentration (10, 50, 100 and 200mM) and temperature (25, 45 and 65°C) were investigated. Among various models, Higiro model showed a higher performance to determine intrinsic viscosity of SSG at all temperatures and cosolutes. From 25 to 65°C for every 20°C rise in temperature, intrinsic viscosity decreased about 18.99 and 63.86%, respectively. The divalent cations had more reduction effect on intrinsic viscosity than monovalet cations. More flexibility of SSG in monovalent salts solutions compared with divalent ones was observed. A high value for activation energy (2.53×107J/kgmol) and chain flexibility (3046.45) of SSG was obtained, which was higher than many hydrocolloids. The shape factor of SSG macromolecules at 25–65°C was an oblate or prolate and for all used cosolutes, the shape was roughly found to be ellipsoidal.

Chemical Thermodynamics: A Journey of Many Vistas

Chemical thermodynamics is of central importance in chemistry, physics, the biosciences and engineering. It is a highly formalized scientific discipline of enormous generality, providing a mathematical framework of equations (and a few inequalities), which yields exact relations between macroscopically observable thermodynamic equilibrium properties of matter and restricts the course of any natural process. While these aspects alone are already of the greatest value for practical applications, in conjunction with judicially selected molecular-based models of material behavior, that is to say by using concepts from statistical mechanics, experimentally determined thermodynamic quantities contribute decisively towards a better understanding of molecular interactions and hence of real macroscopic systems. A plenary lecture affords the lecturer an opportunity to survey a few reasonably large sub-areas of the fields he works/worked in and to reflect on them from the perspective of many years of research. The general subject I selected for this review, i.e. chemical thermodynamics of liquid nonelectrolytes (pure or mixed), is vast. Over the last decades, the field’s impressive growth has been stimulated by the continuously increasing need for thermophysical property data and phase equilibrium data in the applied sciences, and it has greatly profited by advances in experimental techniques, by advances in the theory of liquids in general, and by advances in computer simulations of reasonably realistic model systems in particular. Specifically, I shall focus on just three topics of increasing complexity: (1) heat capacities and related quantities of fairly simple molecular liquids, predominantly at or near orthobaric conditions; (2) chemical thermodynamics of binary liquid mixtures containing one strongly dipolar aprotic component; (3) caloric properties of dilute solutions of nonelectrolytes, with emphasis on properties of aqueous solutions at infinitedilution (which are of importance in biophysical chemistry).

Single-chain nanoparticles vs. star, hyperbranched and dendrimeric polymers: effect of the nanoscopic architecture on the flow properties of diluted solutions.

The flow properties of dilute solutions of linear, star, hyperbranched and dendrimeric polymers have been the subject of numerous studies. However, no systematic analysis has been carried out for the case of single-chain nanoparticles (SCNPs) of different nature, which are unimolecular soft nano-objects consisting of individual polymer chains collapsed to a certain degree by means of intramolecular bonding. On the basis of the fractal nature of SCNPs and experimental data of the hydrodynamic radius, a simple predictive power-law between the intrinsic viscosity and molecular weight is proposed. Furthermore, a comparison is made between the intrinsic viscosities of SCNPs and of low-functionality stars, hyperbranched and dendrimeric polymers of the same chemical nature and molecular weight. As a consequence of their complex nanoscopic architecture, the intrinsic viscosities of SCNPs are systematically smaller than those of linear chains and low-functionality stars. When compared with hyperbranched and dendrimeric polymers, a complex behaviour is found, this being highly dependent on the molecular weight and amount of X-linkers of SCNPs.

ChemInform Abstract: Solution Phase Thermodynamics of Strong Electrolytes Based on Ionic Concentrations, Hydration Numbers and Volumes of Dissolved Entities

AbstractReview: 54 refs.

Effect of Hard Segment Molecular Weight on Dilute Solution Properties of Ether Based Thermoplastic Polyurethanes

A systematic study was conducted on the effect of hard segment molecular weight (or length) on solution and bulk properties of ether based thermoplastic polyurethanes (TPUs). The purpose of this study is to provide a roadmap to deliver the desired end-use performance of a polyurethane product based on the optimal design of the starting materials. In this paper, we report our findings on the effects of hard segment molecular weight on properties of a dilute solution of TPUs in N, N-dimethyl formamide (DMF). The molar feed was used to determine the molecular weight of the hard segment. Then, the weight fraction of the hard segment is determined by calculating the ratio of the molecular weight of the hard segment to the number average molecular weight of the TPU determined by Gel Permeation Chromatography. It was found at low hard segment weight fraction there is a significant impact on the weight average molecular weight and molecular weight distribution, intrinsic viscosity, critical concentration, hydrodynamic diameter, polymer-solvent interaction parameter and second virial coefficient. However, at high weight fractions at around 0.4, the impact is minimal. Furthermore, the weight fraction has a minimal impact on number average molecular weight, and the expansion parameter in the Flory-Huggins analysis.

알로에 한외여과 다당분획의 희석용액 특성

알로에 한외여과 다당분획의 희석용액 특성

Viscosity of dilute solutions of styrene copolymers in the course of polymer-analogous transformations

The properties of dilute solutions of styrene copolymers and their porphyrin derivatives prepared via the functional group transformations have been studied in DMF at 20–35°C. The effect of the copolymer composition, on the intrinsic viscosity, the Huggins constant, the macromolecule dimensions, and thus on the interaction with solvent has been elucidated. The nature and content of functional groups in the polymer influence the behavior of macromolecule coil in the solution. Introduction of the porphyrin fragment loosens the macromolecular coil, but does not qualitatively change the solution behavior.

Influence of spatial isomerism of tetrathiacalix[4]arene functionalized by hydrazide groups on self-organization and physicochemical properties of aqueous dimethyl sulfoxide solutions of low concentration

264 Recently, we have discovered a new phenomenon that opens the way to elucidating the mechanism of the effect of weak action of different nature on living organisms [1–5]. This phenomenon, referred to as “effect of ultralow concentrations and electromag netic fields” [2], consists in the formation of nano sized molecular ensembles, so called nanoassociates, in aqueous solutions of low concentrations. The nanoassociate formation is responsible for the emer gence of unique physicochemical properties of dilute solutions and, which is especially important, corre lates with bioeffects of these solutions [3, 4]. Forma tion of nanoassociates is initiated by a solute under certain conditions, the most essential among which are the presence of external electromagnetic fields and a definite structure of a substance [5].

Dilute Solution Properties of a Polymacromonomer Consisting of a Polystyrene Main Chain with Polyisoprene Side Chains. Relation of Molecular Parameters to Polymer Segment Interactions

Light scattering and viscosity measurements were made on dilute solutions of a polymacromonomer consisting of a polystyrene main chain and polyisoprene (PI) side chains, which was synthesized by an...

Dilute solution properties of carboxymethyl celluloses of various molecular weights and degrees of substitution

The intrinsic viscosities of six carboxymethyl celluloses (CMC) of different degrees of substitution, molecular weights, and molecular weight distributions (MWDs) were measured as a function of pH, ionic strength, and temperature. The molecular weights and MWDs were determined by analytical ultracentrifugation. It was demonstrated that the raw viscosity data could be represented by the Fedors equation allowing for accurate determination of the intrinsic viscosity. Ionic strength, rather than pH or temperature had the strongest effect on the conformation of CMC. An estimate of the Mark–Houwink–Kuhn–Sakurada exponent (α=0.83) and calculations of chain flexibility and expansion factors indicated that CMC has semi-flexible, randomly coiling chains in solution with persistence lengths on the order of 8.8–24.5nm in distilled water and 11.3–14.8nm in 0.01mol/L sodium chloride. It was also found that the lowest molecular weight CMC was most flexible among the tested samples.