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.