PHYSICOCHEMICAL STUDIES ON DI-IODOTYROSINE DEXTRAN

Dextran is currently being considered as a carrier biopolymer system for drug targeting. Di-iodotyrosine (DIT), and its radioactive derivative are useful markers for identifying the in-vivo route of these substrates. The performance of these substances in vivo is closely linked to their physico-chemical properties in solution. These properties have been investigated on a series of gel permeation chromatography fractionated DIT-dextrans using a combination of sedimentation, viscometric and laser-light scattering techniques. Weight average molecular weights, M(W), from sedimentation equilibrium and light scattering range from 0.0195 to 0.054 x 10(6). Double logarithmic representations of M(W) versus sedimentation coefficient, S20,W(O), and intrinsic viscosity [eta] suggest that these labelled dextrans have a more compact conformation in solution than do their unlabelled analogues - which behave as random coils. The implications of this for drug delivery are indicated.