Carboxymethylation and acetylation of the polysaccharide from Cordyceps militaris and their α-glucosidase inhibitory activities.

The crude polysaccharide extracted from Cordyceps militaris was chemically modified to obtain carboxymethylated derivatives (CM-CPS) and acetylated derivatives (AC-CPS). The physicochemical characterizations were comparatively investigated by chemical methods, high-performance gel permeation chromatography, FT-IR spectra, NMR analysis, Congo red test, scanning electron microscopy, atomic force microscopy and differential scanning calorimetry. Then α-glucosidase inhibitory activities were conducted to determine the structure-bioactivity relationship. Results indicated that carboxymethylation and acetylation modification of polysaccharide were successful with the carboxymethyl substitutions might being C-6, C-2 and acetyl substitutions at C-3, C-6 inferred from NMR analysis. In addition, the tertiary structure, ultrastructure, melting properties were also different from native polysaccharide. Besides, α-glucosidase inhibitory activities of derivatives exhibited differently with CM-CPS to be the lowest. Therefore, it was concluded that change of structure in polysaccharide had certain effect on bioactivity with degree of substitution and substituents position being the influence factors.

Expression of rat protamine gene in MEL cells / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the expression of rat protamine (RP) gene in MEL cells and the effect on cell growth.</p><p><b>METHODS</b>Eukaryotic expression plasmid pCR-3.1-RP was constructed and transfected into MEL cells. The changes of cell growth rate, mitotic index and colony-forming rate in semi-solid medium were investigated.</p><p><b>RESULTS</b>Transfected MEL cells showed lower growth rate, mitotic index and colony-forming rate. Volumes of cells were reduced and reduction of RNA transcription was observed.</p><p><b>CONCLUSION</b>These results suggest that expression of RP in MEL cell may inhibit the cell growth and proliferation.</p>