Xinlin Wei

Four flavones (flavone, 7‐hydroxyflavone, chrysin, and baicalein) sharing the same B‐ and C‐ring structure but a different numbers of hydroxyl groups on the A‐ring were studied for their affinities for BSA and HSA. The hydroxylation on ring A of flavones increased the binding constants (K_a) and the number of binding sites (n) between flavones and serum albumins. The affinities of 7‐hydroxyflavone for BSA and HSA were about 800 times and 40 times higher than that of flavone, respectively. It appears that the optimal number of hydroxyl groups introduced to the ring A of flavones is one. As more hydroxyl groups were introduced to positions at C‐5, C‐6, and/or C‐7 of flavones, the affinities for serum albumins decrease. The critical energy transfer distances (R₀) between the hydroxylated flavones (1–3 OH on the ring A) and serum albumins decreased with the increasing affinities for serum albumins.

A chitosan-degrading fungus, BSF114, was isolated from soil. The culture preparation showed strong chitosanolytic enzyme activity at optimum pH 4.0 and optimum temperature of 60 degrees C after 36-40 h fermentation. The rapid decreased viscosity of chitosan solutions at early stage of reaction suggested an endo-type cleavage of the polymeric chitosan chains. To identify the isolated fungus, molecular biological and morphological methods were used. The fungal internal transcribed spacer (ITS) region 1 was amplified, sequenced, and then compared with related sequences in the GenBank database using BLAST. The phylogenetic relationships were then analyzed, and the results showed that the fungus belongs to Aspergillus fumigatus. Morphological observations were also used to confirm the above conclusion. The chitooligosaccharides (COS) obtained through hydrolyzing the colloidal chitosan showed A. fumigatus BSF114 is suitable for degrading chitosan and producing chitooligosaccharides on a large scale. High concentrations of the COS (1000 and 500 microg/mL) significantly proliferated mice marrow cells.

Effects of chitosan pentamer ((GLcN)₅) and chitosan hexamer ((GLcN)₆) in vivo and in vitro on gene transcription and protein translation of interleukin-1 (IL-1), tumour necrosis, factor alpha (TNF-α), interleukin-2 and interferon-γ (IFN-γ) were investigated by relatively quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. The results showed that the expression of IL-1 mRNA, TNF-α mRNA, IFN-γ mRNA as well as the secretion of IL-1, TNF-α and IFN-γ can both be promoted by (GLcN)₆ and (GLcN)₅. The promotion effects caused by (GLcN)₆ were greater than that of (GLcN)₅. Gene transcription and protein secretion of cytokines were promoted by (GLcN)₅ and (GLcN)₆ in vivo and in vitro and thus the immuno-modulating ability was promoted. This may be one of the molecular mechanisms for elucidation of immunity of chitooligosaccharides.