Regulation of the physiology and virulence of Ralstonia solanacearum by the second messenger 2',3'-cyclic guanosine monophosphate.

Previous studies have demonstrated that bis-(3',5')-cyclic diguanosine monophosphate (bis-3',5'-c-di-GMP) is a ubiquitous second messenger employed by bacteria. Here, we report that 2',3'-cyclic guanosine monophosphate (2',3'-cGMP) controls the important biological functions, quorum sensing (QS) signaling systems and virulence in Ralstonia solanacearum through the transcriptional regulator RSp0980. This signal specifically binds to RSp0980 with high affinity and thus abolishes the interaction between RSp0980 and the promoters of target genes. In-frame deletion of RSp0334, which contains an evolved GGDEF domain with a LLARLGGDQF motif required to catalyze 2',3'-cGMP to (2',5')(3',5')-cyclic diguanosine monophosphate (2',3'-c-di-GMP), altered the abovementioned important phenotypes through increasing the intracellular 2',3'-cGMP levels. Furthermore, we found that 2',3'-cGMP, its receptor and the evolved GGDEF domain with a LLARLGGDEF motif also exist in the human pathogen Salmonella typhimurium. Together, our work provides insights into the unusual function of the GGDEF domain of RSp0334 and the special regulatory mechanism of 2',3'-cGMP signal in bacteria.

Easy access to secondary and tertiary alcohols via metal-free and light mediated radical carbonyl allylation.

Here we report a strategy for carbonyl addition with unactivated alkenes using an organic photocatalyst on both aldehyde and ketone substrates. This protocol grants us a good alternative to the traditional Barbier-Grignard allylation that exhibits poor functional group tolerance. With this method the stoichiometric use of metals can be avoided, high atom economy can be achieved and fewer by-products are generated.

Recent Development in Ligation Methods for Glycopeptide and Glycoprotein Synthesis.

Glycoproteins are produced by the post-translational modification process of proteins and they play an important role in mediating various biological processes. Our understanding towards biochemical functions of individual glycoproteins has been seriously hampered due to the heterogeneous expression of carbohydrate parts in glycoproteins. Despite the advancement in recombinant expression and chromatographic techniques, the isolation of pure glycoforms remains nearly impossible. To obtain homogenous glycoproteins, tremendous efforts hves been spent in developing various ligation and glycosylation techniques. This minireview discusses selected methods for the preparation and ligation of glycopeptides. The importance of the development of new chemical synthesis method for glycoproteins has also been discussed, which would be one of the next directions in this field.