A novel esterase was identified through functional screening of a metagenomic library in Escherichia coli obtained from Antarctic desert soil. The 297-amino-acid sequence had only low (<29%) similarity to a putative esterase from Burkholderia xenovorans. The enzyme was active over a temperature range of 7 to 54°C and at alkaline pH levels and is a potential candidate for industrial application.

A novel, cold-active and highly alkaliphilic esterase was isolated from an Antarctic desert soil metagenomic library by functional screening. The 1,044 bp gene sequence contained several conserved regions common to lipases/esterases, but lacked clear classification based on sequence analysis alone. Moderate (<40%) amino acid sequence similarity to known esterases was apparent (the closest neighbour being a hypothetical protein from Chitinophaga pinensis), despite phylogenetic distance to many of the lipolytic "families". The enzyme functionally demonstrated activity towards shorter chain p-nitrophenyl esters with the optimal activity recorded towards p-nitrophenyl propionate (C3). The enzyme possessed an apparent T(opt) at 20°C and a pH optimum at pH 11. Esterases possessing such extreme alkaliphily are rare and so this enzyme represents an intriguing novel locus in protein sequence space. A metagenomic approach has been shown, in this case, to yield an enzyme with quite different sequential/structural properties to known lipases. It serves as an excellent candidate for analysis of the molecular mechanisms responsible for both cold and alkaline activity and novel structure-function relationships of esterase activity.

A 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-catalysed electrochemical synthesis of 2-amino-1,3,4-thiadiazoles from isothiocyanates and hydrazones is presented. This protocol is mild, practical, metal-free and exogenous oxidant-free, and features a broad substrate scope. Extensive mechanistic...

A visible-light-induced regioselective tandem enamido β-C(sp 2 )À H alkylation/acrylamido alkylation/cyclizative alkenylation sequence of 3aza-1,5-dienes is presented. This protocol is regiospecific, features a broad substrate scope, and provides a direct access to 3,4-dialkylated 4pyrrolin-2-ones from readily available N-alkenylacrylamides. It is readily scalable to a gram scale, and could be induced by natural sunlight.

An efficient one-pot approach for the controllable synthesis of trifluoromethyl/gem-difluoromethylene substituted cyclobutene derivatives has been developed. The mechanism may involve visible light-induced [2+2]-cycloaddition of quinolinones with 1-bromo-1-trifluoromethylethene, followed by base-promoted...