Effects of storage time on quality of Desmodium styracifolium seeds / 中国中药杂志

The dynamic changes of germination percentage, germination potential, thousand-seed weight, antioxidase activity in Desmodium styracifolium seeds with different storage time were tested, and electrical conductivity, contents of soluble sugar, soluble protein, starch in seed leach liquor were also determined in order to reveal the mechanism of seed deterioration. The results as the following. (1) The germination percentage, germination potential and thousand-seed weight of D. styracifolium seeds declined, while the seed coat color darkened with the extension of storage time. (2) The activities of superoxide dismutase (SOD) and peroxidase (POD) decreased with the prolongation of storage period. The SOD activity declined fastest in 1,095-1,185 d of storage, while the POD activity declined significantly in 365-395 d of storage. (3) The electrical conductivity and the contents of soluble sugar, starch in seed leach liquor increased, while the content of soluble protein declined with the extension of storage time. (4) Correlation analysis indicated that the germination percentage, germination potential and thousand-seed weight of D. styracifolium seeds have a significantly positive correlation with SOD and POD activity, while have a significantly negative correlation with the electrical conductivity, contents of soluble sugar and starch. It can be concluded that during the storage of D. styracifolium seeds, physiological and biochemical changes including decrease in antioxidase activity, rise in electrical conductivity, degradation effluent of soluble sugar and starch, degradation of soluble protein were the main factors leading to the seed deterioration.

Improved the solubility of maize uroporphyrinogen III methyltransferase as the red fluorescent indicator by site-directed mutagenesis / 生物工程学报

S-adenosylmethionine-dependent uroporphyrinogen III methyltransferase (SUMT) is a novel red fluorescence indicator. However, the production of SUMT in Escherichia coli is restricted by its relatively low solubility, and little is known about the red fluorescent materials that are associate with SUMT. Two individual SUMT mutations, L166A and L88R/L89G double mutant were produced by site-directed mutagenesis. Both mutants were overexpressed in E. coli and purified by Ni-NTA chromatography. The reddish mixtures isolated from the purified L88R/L89G double mutant were analyzed by UV-visible spectra scanning and mass analysis(MS). The L88R/L89G double mutant has enzymatic activity in vivo, whereas L166A mutant loses the activity. Trimethylpyrrocorphin is identified as the main constituent in the isolated pigments. The purified L88R/L89G mutant increases protein solubility, which is applied potentially as the fluorescent indicator denoting the solubility of protein fusion partner.