Abstract:Pure catalase from bovine liver was used to study the photosensitive effect by two photosensitizors hematoporphyrim and riboflavin. The change of enzyme protein conformation in solution was determinted by ultraviolet absorption difference spectra. The activity of catalase was measured by oxygen electrode.Catalase activity was inhibited in the presence of light and photosensitizor. The inhibition increased with the increasing concentration of photosensitizor and illumination time. Absorption spectra were shifted and the shape of absorption peak was modified in the cata- lase-photosensitizor reaction. A nagative peak of 229 nm and a 236—240 nm peak in UV difference spectra were observed by the action of hematoporphyrin and riboflavin, respectively. The results indicate that the activity inhibition of catalase induced by photosensitive oxidation was related to the change of enzyme protein conformation. It is suggested that the photosensitive inactivation of catalase may be due to the photodynamic injury caused by the active oxygen produced from photosensitive reaction.

Abstract:The nucleotide sequence of the promoter and the signal peptide of E. coli alkaline phosphotase gene from pFOG405 plasmid has been disclosed and compared with the sequence reported by Kikuchi et al. The result shows that the PvuⅡ-HpaⅡ fragment (144bp) containing the promoter and signal peptide sequence from pYK190 plasmid is sufficient for expression and secretion of foreign genes in E. coli. The deletion of the dyad sequence (26bp) from 5' end of the promoter region doesn't affect expression level of foreign target genes. The experiment also provids the useful information for construction of efficient expression and secretion vector using the PvuⅡ-HpaⅡ fragment and studying regulation of gene expression.

Abstract:A monoclonal antibody (H₆₅) was coupled to ricin using three different cross-agents respectively. Immunotoxins (ITs) with greater cytotoxic potency were obtained through a proper scheme. The ITs reduced the ³H-leucine incorporation of Molt-4 cells by 50％ at a concentration (IC₅₀) of 2.7×10^-12mol/L. ITs prepared with disulfide bond is 5—10 fold more cytotoxic in vitro than those prepared with thioether bond. The speed of metabolism of the latter in vivo is two times slower than that of the former. Because these two kinds of ITs have different degradation products, their metabolism pathways in vivo may be different also.

Abstract:For the study on the relationship between arterial proteoglycans (PG_s) and atherosclerosis (As), PGs of aortic intima-media of man (from Beijing with higher and Nanning in Guang Xi province with lower prevalence of As), rabbit and dog were separated successively on DEAE-Sephacel ion exchange and gel filtration column chromatography. Three types of PG, namely heparan sulfate PG(HSPG), chondroitin sulfate PG (CSPG) and dermatan sulfate-chondroitin sulfate PG(DSCSPG) were characterized and quantitated. Glycosaminoglycans from DSCSPG were run on cellulose acetate membrane and the relative percentages of DS and CS were calculated densitometrically on stained strips. The results revealed: 1. The contents of total PG,, HSPG and DSCSPG in Nanning sample were significantly higher than the corresponding ones in Beijing sample; 2. The contents of total PG, in aortas of rabbit and dog were lower than that of man, among which the contents and relative percentages of CSPG, HSPG of rabbit and dog, the content of DSCSPG of rabbit were also lower than that of corresponding PG in man; while the DSCSPG content of dog were similar to Nanning man; 3. Lower relative percentages of DS in DSCSPG from Nanning man and dog in comparing with those from either Beijing man or rabbit evne though the content and relative percentage of DSCSPG of Nanning man and dog were higher. As HSPG and DSPG were known to be antiproliferative to arterial Smooth muscl tells and of higher binding affinity to plasma low density lipoprotein respectively, the above results might be implicated in the lower prevalence of As in Nanning man and "resistant" co As of dog.