Determination of Molecular Shape by Osmotic Measurement

Isihara, A.

doi:10.1063/1.1747510

Cited by 218 publications

(114 citation statements)

References 2 publications

Supporting

Mentioning

113

Contrasting

Order By: Relevance

“…A thermodynamic effective diameter, σ B2 = 7.40 nm, follows from demanding equal second virial coefficients, B 2 (T ), of hard spheroid and effective hard sphere [36].…”

Section: Single-particle Propertiesmentioning

confidence: 99%

Viscosity and diffusion: crowding and salt effects in protein solutions

et al. 2012

View full text Add to dashboard Cite

We report on a joint experimental-theoretical study of collective diffusion in, and static shear viscosity of solutions of bovine serum albumin (BSA) proteins, focusing on the dependence on protein and salt concentration. Data obtained from dynamic light scattering and rheometric measurements are compared to theoretical calculations based on an analytically treatable spheroid model of BSA with isotropic screened Coulomb plus hard-sphere interactions. The only input to the dynamics calculations is the static structure factor obtained from a consistent theoretical fit to a concentration series of small-angle X-ray scattering (SAXS) data. This fit is based on an integral equation scheme that combines high accuracy with low computational cost. All experimentally probed dynamic and static properties are reproduced theoretically with an at least semi-quantitative accuracy. For lower protein concentration and low salinity, both theory and experiment show a maximum in the reduced viscosity, caused by the electrostatic repulsion of proteins. The validity range of a generalized Stokes-Einstein (GSE) relation connecting viscosity, collective diffusion coefficient, and osmotic compressibility, proposed by Kholodenko and Douglas [PRE, 1995[PRE, , 51, 1081 is examined. Significant violation of the GSE relation is found, both in experimental data and in theoretical models, in semi-dilute systems at physiological salinity, and under low-salt conditions for arbitrary protein concentrations.

show abstract

“…A thermodynamic effective diameter, σ B2 = 7.40 nm, follows from demanding equal second virial coefficients, B 2 (T ), of hard spheroid and effective hard sphere [36].…”

Section: Single-particle Propertiesmentioning

confidence: 99%

Viscosity and diffusion: crowding and salt effects in protein solutions

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Normalized by the radius of a sphere with equal volume (the mean radius of curvature of a sphere is just the spherical radius), the mean radius of curvature R for an ellipsoid of revolution becomes [43] The value of R for the triaxial ellipsoid has also been worked out [49]. The electrostatic capacity of an object is de6ned by the following problem.…”

Section: B Mean Radius Of Curvaturementioning

confidence: 99%

“…This functional is always defined for a pair of objects. The "excluded volume" terminology comes from the statistical mechanics of gases, where this functional arises in the leading order concentration expansion (virial expansion) for the pressure in the case of gas particles that repel each other with a hard-core volume exclusion [43]. Isihara [43] gives a general expression for the excluded volume of two convex objects, involving the surface area ( V,") = V, + V2+( A, R, + A zRz )/4m .…”

Section: E Excluded Volumementioning

confidence: 99%

“…In the present paper, these functionals of particle shape are normalized so as to be independent of the size of the particle and to equal unity for a sphere. The surface area of an ellipsoid of revolution is well known [43]. The surface area of a triaxial ellipsoid involves a more complicated closed form involving elliptic functions [44,45].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Geometrical percolation threshold of overlapping ellipsoids

et al. 1995

View full text Add to dashboard Cite

A recurrent problem in materials science is the prediction of the percolation threshold of suspensions and composites containing complex-shaped constituents. We consider an idealized material built up from freely overlapping objects randomly placed in a matrix, and numerically compute the geometrical percolation threshold p, where the objects first form a continuous phase. Ellipsoids of revolution, ranging from the extreme oblate limit of platelike particles to the extreme prolate limit of needlelike particles, are used to study the inhuence of object shape on the value of p, . The reciprocal threshold 1/p, (p, equals the critical volume fraction occupied by the overlapping ellipsoids) is found to scale linearly with the ratio of the larger ellipsoid dimension to the smaller dimension in both the needle and plate limits. Ratios of the estimates of p, are taken with other important functionals of object shape (surface area, mean radius of curvature, radius of gyration, electrostatic capacity, excluded volume, and intrinsic conductivity) in an attempt to obtain a universal description of p, . Unfortunately, none of the possibilities considered proves to be invariant over the entire shape range, so that p, appears to be a rather unique functional of object shape. It is conjectured, based on the numerical evidence, that 1/p, is minimal for a sphere of all objects having a finite volume.

show abstract

“…Although the predictions were later improved by Mayer-Saupe approach which completely neglects steric contributions in favour of dispersion interactions, Onsager's approach has been applied to more realistic nematogenic molecules. An early generalization was the analytic computation of E for a pair of ellipsoids of revolution by Isihara [2] through a format that relies on classical mathematical work on convex geometry, also used by Kihara [3] who obtained the formal expression of the excluded volume for a pair of equal convex bodies. A step forward was moved by Tjipto-Margo and Evans [4] who obtained a closed form for the excluded volume of biaxial ellipsoids which, at variance with Isihara's case, are only endowed with D 2h , instead of D ∞h , symmetry.…”

Section: Introductionmentioning

confidence: 99%

Excluded area computations for non-convex molecules

Rosso

2008

Mol. Phys.

View full text Add to dashboard Cite

International audienceBy using methods of computer-aided geometric design (CAGD), we compute explicitly the excluded area for a pair of non-convex molecules obtained by moving a disk of radius h on a circular arc of radius R and amplitude 2α: they are referred to as boomerangs or horseshoes, depending on the value of α. As a result, the excluded area always attains its absolute minimum when the molecules are antiparallel, instead of parallel, a feature that makes them a good candidate to study shape polarity effects in steric interactions. Although the excluded area is in general a rather complicated function of the relative orientation, with α and η:=h/R acting as parameters, when η<< 1 a remarkably simple formula is obtained. In this limit, the anisotropic part of the excluded area is independent of η

show abstract

Determination of Molecular Shape by Osmotic Measurement

Abstract: The second coefficient A2 of osmotic pressure π of high-polymer solutions is calculated in the case of the rigid ovaloid. A2 is a function of the molecular shape and thus we can determine the shape of high polymers.

Cited by 218 publications

References 2 publications

Viscosity and diffusion: crowding and salt effects in protein solutions

Viscosity and diffusion: crowding and salt effects in protein solutions

Geometrical percolation threshold of overlapping ellipsoids

Excluded area computations for non-convex molecules

Contact Info

Product

Resources

About