THE AGGREGATION OF TRICHOSANTHIN IN AQUEOUS-SOLUTION

As a kind of cytotoxin extracted from the root tuber of Trichosanthes kirilowil Maxim (Cucurbitaceae), trichosanthin can selectively bind to and kill the placental trophoblastic cells, which leads to a number o f biomedical applications including the inhibition of trophoblastic tu mors. However, the stability of trichosanthin in living organism is st ill one of the problems hindering the effectiveness of its application s. In this study, laser light scattering has been used successfully to investigate the stability of trichosanthin in both deionized water an d KSCN aqueous solution in terms of the hydrodynamic size distribution of the trichosanthin aggregates as a function of both time and the sa lt concentration. It is found that the size distribution is always a b imodal one. One peak corresponds to a single trichosanthin chain; the other corresponds to the trichosanthin aggregates, which have an avera ge hydrodynamic radius of similar to 49 nm and are composed of similar to 127 trichosanthin molecules when C-KSCN is higher than 0.5 mol/L. This implies that there exists an equilibrium between the single trich osanthin chain and its aggregates [i.e., nT reversible arrow (T)(n)]. Our results also suggest that the aggregates are made of the loosely p acked trichosanthin molecules and behave as flexible polymer chains in theta solvent. (C) 1996 John Wiley & Sons, Inc.