Quantitative Characterization of Polymer−Polymer, Protein−Protein, and Polymer−Protein Interaction via Tracer Sedimentation Equilibrium

Abstract

Quantitative analysis of the composition dependence of the concentration gradient of each species of macromolecule within a solution mixture at sedimentation equilibrium permits the quantitative characterization of self- and heterointeractions between sedimenting solutes. Sedimentation equilibrium experiments were conducted on solutions containing a trace concentration of FITC-labeled BSA in varying concentrations of Ficoll 70 and on solutions containing a trace concentration of FITC-labeled Ficoll 70 in varying concentrations of BSA. The equilibrium gradient of each solute component in each mixture was measured independently. Analysis of the resulting gradients resulted in evaluation of the dependence of the activity coefficient of Ficoll upon the concentrations of Ficoll and BSA at concentrations of up to 100 g/L and the dependence of the activity coefficient of BSA upon the concentrations of Ficoll and BSA at concentrations of up to 100 g/L. The activity coefficients of both species increase significantly with increasing Ficoll and BSA concentration and do not vary with temperature, to within the precision of measurement, over the temperature range of 5–37 °C, indicating that the dominant interaction between Ficoll molecules and between BSA and Ficoll molecules is repulsive and probably due to steric volume exclusion. The measured dependences may be accounted for quantitatively by a simple model in which BSA and Ficoll 70 are represented by equivalent rigid particles.

Respiratory epithelial cytotoxicity and membrane damage (holes) caused by amine-modified nanoparticles

“…Regarding the marked differences between albumin adsorption onto 50 and 100 nm amino-modified NPs, according to the space-filling model of the crystal structure of human albumin (Fodeke and Minton 2010), it is best described as a sphere with diameter of 69Å (6.9 nm). 50 nm nanospheres with a surface area of 7,857 nm 2 could theoretically adsorb 210 albumin molecules on their surface, whereas 100 nm spheres (surface area 31,428 nm 2 ) could adsorb up to 840 albumin molecules on their surface.…”

Effect of Nonadditive Repulsive Intermolecular Interactions on the Light Scattering of Concentrated Protein−Osmolyte Mixtures

“…9,10,24 However, the effective volume of the hard sphere representing protein as sensed by a neutral TMAO molecule has little or no contribution from electrostatic interaction, and hence would be expected to be smaller. 25 We denote the effective specific volume of the protein with respect to self-interaction by $v_{\text{eff},1}^{(\text{self})}$ and the effective specific volume with respect to interaction with TMAO by $v_{\text{eff},1}^{(\text{other})}$. The question then arises, how may one calculate the composition-dependent activity coefficients and concentration derivatives of the activity coefficients of both species using hard particle fluid theory when the effective volume of protein is not constant?…”

Macromolecular Crowding In Vitro , In Vivo , and In Between

“…At the same time, experimental measurement of the pH dependence of colligative properties of protein solutions revealed that under other conditions, longer-ranged repulsive and attractive electrostatic interactions between macromolecules contribute significantly to the chemical potential, and hence reactivity, of macromolecules in concentrated solutions 36, 37 . Nonspecific electrostatic attraction between probe and crowder species was found to counteract the effects of volume exclusion to a varying extent, and in certain instances to dominate the overall behavior of individual tracer proteins, peptides, and nucleotides 19, 38–40 . Several approaches to the generalization of crowding theory to allow for enthalpic as well as entropic intermolecular interactions have been published 21, 36, 38, 41–46 .…”