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Second Virial Coefficient (second + virial_coefficient)
Selected AbstractsHow correct is the EOS of weakly nonideal hydrogen plasmas?CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2003A.N. Starostin Abstract Helioseismology opens new possibility to check EOS of weakly nonideal hydrogen plasmas with high precision, using reconstructed local sound velocities within 10-4 accuracy. A comparison of different theoretical models with experiment permits to verify the existing methods of calculation bound states and continuum contribution to the second virial coefficient within the framework of physical nature. The regular way of the deduction expression for EOS is presented and generalization of the EOS for broad atomic states and two temperature non-equilibrium case is proposed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Solvent-dependent conformation of amylose tris(phenylcarbamate) as deduced from scattering and viscosity dataBIOPOLYMERS, Issue 9 2009Taichi Fujii Abstract The z -average mean-square radius of gyration ,S2,z, the particle scattering function P(k), the second virial coefficient, and the intrinsic viscosity [,] have been determined for amylose tris(phenylcarbamate) (ATPC) in methyl acetate (MEA) at 25°C, in ethyl acetate (EA) at 33°C, and in 4-methyl-2-pentanone (MIBK) at 25°C by light and small-angle X-ray scattering and viscometry as functions of the weight-average molecular weight in a range from 2 × 104 to 3 × 106. The first two solvents attain the theta state, whereas the last one is a good solvent for the amylose derivative. Analysis of the ,S2,z, P(k), and [,] data based on the wormlike chain yields h (the contour length or helix pitch per repeating unit) = 0.37 ± 0.02 and ,,1 (the Kuhn segment length) = 15 ± 2 nm in MEA, h = 0.39 ± 0.02 and ,,1 = 17 ± 2 nm in EA, and h = 0.42 ± 0.02 nm and ,,1 = 24 ± 2 nm in MIBK. These h values, comparable with the helix pitches (0.37,0.40 nm) per residue of amylose triesters in the crystalline state, are somewhat larger than the previously determined h of 0.33 ± 0.02 nm for ATPC in 1,4-dioxane and 2-ethoxyethanol, in which intramolecular hydrogen bonds are formed between the CO and NH groups of the neighbor repeating units. The slightly extended helices of ATPC in the ketone and ester solvents are most likely due to the replacement of those hydrogen bonds by intermolecular hydrogen bonds between the NH groups of the polymer and the carbonyl groups of the solvent. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 729,736, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Lysozyme-lysozyme self-interactions as assessed by the osmotic second virial coefficient: Impact for physical protein stabilizationBIOTECHNOLOGY JOURNAL, Issue 9 2009Virginie Le Brun Abstract The purpose of the presented study is to understand the physicochemical properties of proteins in aqueous solutions in order to identify solution conditions with reduced attractive protein-protein interactions, to avoid the formation of protein aggregates and to increase protein solubility. This is assessed by measuring the osmotic second virial coefficient (B22), a parameter of solution non-ideality, which is obtained using self-interaction chromatography. The model protein is lysozyme. The influence of various solution conditions on B22 was investigated: protonation degree, ionic strength, pharmaceutical relevant excipients and combinations thereof. Under acidic solution conditions B22 is positive, favoring protein repulsion. A similar trend is observed for the variation of the NaCl concentration, showing that with increasing the ionic strength protein attraction is more likely. B22 decreases and becomes negative. Thus, solution conditions are obtained favoring attractive protein-protein interactions. The B22 parameter also reflects, in general, the influence of the salts of the Hofmeister series with regard to their salting-in/salting-out effect. It is also shown that B22 correlates with protein solubility as well as physical protein stability. [source] Screening of Protein-Ligand Interactions by Affinity ChromatographyBIOTECHNOLOGY PROGRESS, Issue 2 2003Carlos D. García This paper examines affinity chromatography (AC) as an alternative tool for the determination of protein-ligand interactions for the particular case in which the ligand is the same protein. The methodology is less labor-intensive and more sample-efficient than traditional methods used to measure the second virial coefficient ( B22), a parameter commonly used to evaluate protein-protein interactions. The chromatographic capacity factor ( k,) was studied for lysozyme and equine serum albumin for a wide range of experimental solution conditions such as crystallizing agent concentration, protein concentration and pH. Parallel experiments using AC to determine k, and static light scattering (SLS) to determine B22 showed that the two parameters were highly correlated. Two different column volumes (,1 and ,0.1 mL) were tested and gave essentially the same values for k,, showing the feasibility of miniaturization. [source] Fitting complex potential energy surfaces to simple model potentials: Application of the simplex-annealing methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2005Raúl A. Bustos Marún Abstract A stochastic method of optimization, which combines simulated annealing with simplex, is implemented to fit the parameters of a simple model potential. The main characteristic of the method is that it explores the whole space of the parameters of the model potential, and therefore it is very efficient in locating the global minimum of the cost function, in addition to being independent of the initial guess of the parameters. The method is employed to fit the complex intermolecular potential energy surface of the dimer of water, using as a reference the spectroscopic quality anisotropic site,site potential of Feller et al. The simple model potential chosen for its reparameterization is the MCY model potential of Clementi et al. The quality of the fit is assessed by comparing the geometry of the minimum, the harmonic frequencies, and the second virial coefficients of the parameterized potential with the reference one. Finally, to prove more rigorously the robustness of this method, it is compared with standard nonstochastic methods of optimization. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 523,531, 2005 [source] Effects of additives on surfactant phase behavior relevant to bacteriorhodopsin crystallizationPROTEIN SCIENCE, Issue 12 2006Bryan W. Berger Abstract The interactions leading to crystallization of the integral membrane protein bacteriorhodopsin solubilized in n-octyl-,-D-glucoside were investigated. Osmotic second virial coefficients (B22) were measured by self-interaction chromatography using a wide range of additives and precipitants, including polyethylene glycol (PEG) and heptane-1,2,3-triol (HT). In all cases, attractive protein,detergent complex (PDC) interactions were observed near the surfactant cloud point temperature, and there is a correlation between the surfactant cloud point temperatures and PDC B22 values. Light scattering, isothermal titration calorimetry, and tensiometry reveal that although the underlying reasons for the patterns of interaction may be different for various combinations of precipitants and additives, surfactant phase behavior plays an important role in promoting crystallization. In most cases, solution conditions that led to crystallization fell within a similar range of slightly negative B22 values, suggesting that weakly attractive interactions are important as they are for soluble proteins. However, the sensitivity of the cloud point temperatures and resultant coexistence curves varied significantly as a function of precipitant type, which suggests that different types of forces are involved in driving phase separation depending on the precipitant used. [source] | |||||||||||||