Complex formation of neocarzinostatin chromophore and hydrophobized polysaccharide as an apoprotein model

Abstract

Cholesterol-bearing pullulan (CHP) underwent self-aggregation in water to form hydrogel nanoparticle. On the other hand, neocarzinostatin chromophore (NCS-chr) is separated from the apoprotein of intact neocarzinostatin (NCS) in 0.5M AcONa/AcOH (pH 4.7) in the dark. Complex formation between NCS-chr and the hydrogel nanoparticle of CHP was studied by high performance size exclusion column chromatography (HPSEC), UV-vis spectra, fluorescence spectra, and gel electrophoresis. The complex so obtained was water soluble enough. One hydrogel nanoparticle complexed with approximately 38 NCS-chr molecules. The complex showed the activity to cleave DNA strand of the plasmid. When the actual NCS-chr concentration of the complex was above 11.8μM, circular supercoiled pBR322 plasmid DNA form I was certainly converted to the circular relaxed form II and then to the linear form III. The complexed NCS-chr was stable even for three months under storage at 195K in the dark. Even after heating at 365K, more than ninety percent of NCS-chr still remained in the complex. This is the first example of showing that the simple nonprotein macromolecule, the self-aggregate of a hydrophobized polysaccharide, can nicely substitute for the apoprotein of NCS.