A highly efficient di-C-glycosyltransferase GgCGT was discovered from the medicinal plant Glycyrrhiza glabra. GgCGT catalyzes a two-step di-C-glycosylation of flopropione-containing substrates with conversion rates of >98%. To elucidate the catalytic mechanisms of GgCGT, we solved its crystal structures in complex with UDP-Glc, UDP-Gal, UDP/phloretin, and UDP/nothofagin, respectively. Structural analysis revealed that the sugar donor selectivity was controlled by the hydrogen-bond interactions of sugar hydroxyl groups with D390 and other key residues. The di-C-glycosylation capability of GgCGT was attributed to a spacious substrate-binding tunnel, and the G389K mutation could switch di- to mono-C-glycosylation. GgCGT is the first di-C-glycosyltransferase with a crystal structure, and the first C-glycosyltransferase with a complex structure containing a sugar acceptor. This work could benefit the development of efficient biocatalysts to synthesize C-glycosides with medicinal potential.

This paper reports an ytterbium-doped linear-cavity fiber laser with the optical length of 1.6 km passively modelocked by a high modulation depth semiconductor saturable absorber mirror (SESAM). An ultra-low repetition rate of 191 kHz was achieved. The laser delivered the highly-chirped output pulses with the energy up to 75.2 nJ.Intensity, a.u. Pulse spectrum of 400-m mode-locked ytterbium-doped fiber laser where the central wavelength was 1033 nm and FWHM is 3.5 nm

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Ripe green banana (Musa sp., AAA group, cv. Zhonggang) fruits treated with 1-methylcyclopropene (1-MCP) significantly delayed the peaks of respiration rate and ethylene production but did not reduce the peak height. Mature banana fruits were also treated with 1-MCP for 24 h at 20 C and then exposed to 50 mL/L ethylene or stored at different temperatures to analyse the effects of external added ethylene. Reductions in firmness, titratable acidity (TA) and starch content (SC) of banana fruits were remarkably delayed by 1-MCP treatment. 1-MCP treatment also delayed the increase of total soluble sugar (TSS) and soluble pectin (SP) contents. Soluble solids (SS) content in the 1-MCP-treated fruit remained almost unchanged during the first 10 days of storage at 20 C. No significant differences in TA, TSS, SP and SS levels were observed between the fruit treated with 1-MCP alone and the fruit treated with 1-MCP plus ethylene. The 1-MCP effects on all the parameters related to banana ripening were enhanced by low temperature storage and reduced by high temperature storage.