Effect of Organic Solvent and Alcohols in Neocarzinostatin
-A Molecular View of the Drug Delivery System
G. Christopher P. Sudhahar¶§, K. Balamurugan¶, K. Jayachithra¶§, S. Aranganathan¶¥, Ru-Jen Cheng§,
Ta Jung Lu§, Chin Yu¥, Der-Hang Chin¶*
From the ¶Department of Chemistry, National Changhua University of education, Changhua, the §Department of Chemistry, National Chung Hsing University, Taichung, and the ¥Department of Chemistry, National Tsing Hua University, Hsinchu
Neocarzinostatin is a potent enediyne antitumor antibiotic complex in which a non-protein chromophore is non-covalently bound to an apoprotein. The chromophore with an unusual structure is responsible for DNA cleavage and is greatly stabilized by binding to its apoprotein. One important pharmacological function is that the protein regulates the drug by proper release of its biologically potent chromophore. To understand the physiological mechanism of the natural drug delivery system, it is essential to study how the apoprotein bind to the chromophore and how the protein releases the tightly bound chromohore to the potential target DNA. For this we have examined the effect of different alcohols (methanol, ethanol, isopropanol and trifluoroethanol) and organic solvent (acetonitrile) in the neocarzinostatin, using circular dichoism, fluorescence, anilinonapthalene sulphonic acid binding, HPLC and kinetic studies. Our results show that the release of the chromophore precedes protein unfolding, which occurs at higher concentration of alcohols. In addition, kinetic studies reveal that the release rate depends on the hydrophobic nature of the solvent.