Characterization of collagenous meshworks by volume exclusion of dextrans

Abstract

The volumes from which 3H-labeled dextrans are excluded by [human] dermal collagenous fibers were calculated by dilution of dextran probes. Five dextrans, of average Stokes'' radii 1.72, 2.53, 3.92, 4.54 and 14.24 nm, were investigated at concentrations between 0.1 and 3% (wt./wt.). The excluded volume was dependent on dextran concentration only for the 2 smaller probes. The largest dextran did not bind to the fibers. A plot of the square root of excluded volume against Stokes'' radius was linear for the 4 smallest dextrans, corresponding to the predictions of Ogston''s rod-and-sphere model of fibrous exclusion, and suggesting that dextrans of Stokes'' radius between 1.72 and 4.54 nm were excluded by a cylindrical solid fiber of radius 2.90 .+-. 0.72 nm. Larger molecules were excluded by a structure of much greater size, since the volume exclusion for the largest dextran was only slightly greater than that of the dextran less than 1/3 its radius. The excluded volume of 3H2O fell slightly below the line describing the dextran data, indicating that water had access to most of the volume not occupied by the collagenous fibers.