Study on the interaction between topotecan hydrochloride or 10-hydroxycamptothecin and transferrin bovine

The binding reactions between topotecan hydrochloride(THC) or 10-hydroxycamptothecin(HCPT) and transferrin bovine(Tf) are studied by fluorescence and UV-Vis absorption spectra.The research results indicate that the combination reaction of them is a single static quenching process,camptothecin derivatives strongly bound Tf with the molar ratio of 1∶1,the equilibrium constant(K0) at 25 oC are as follows,K0(THC)=2.38×105L·mol-1,K0(HCPT) =2.43×106 L·mol-1.The shortest binding distance(r)between donor(Tf) and acceptor(camptothecin derivatives) are obtained by Frster's nonradiative energy transfer mechanism,rTHC =3.77nm,rHCPT =3.92.The enthalpy change(△H) and entropy change(△S) are calculated at 25 oC and 37 oC,the results indicate that hydrophobic interaction and the diple-diple force play a major role in the binding of camptothecin derivatives and Tf.The results of 1H NMR spectrum show that the active groups of HCPT interacting with Tf are 10-OH.