1.An N-terminal threonine mutation produces an efflux-favorable, sodium-primed conformation of the human dopamine transporter.
Fraser R1, Chen Y1, Guptaroy B1, Luderman KD1, Stokes SL1, Beg A1, DeFelice LJ1, Gnegy ME2. Mol Pharmacol. 2014 Jul;86(1):76-85. doi: 10.1124/mol.114.091926. Epub 2014 Apr 21.
The dopamine transporter (DAT) reversibly transports dopamine (DA) through a series of conformational transitions. Alanine (T62A) or aspartate (T62D) mutagenesis of Thr62 revealed T62D-human (h)DAT partitions in a predominately efflux-preferring conformation. Compared with wild-type (WT), T62D-hDAT exhibits reduced [(3)H]DA uptake and enhanced baseline DA efflux, whereas T62A-hDAT and WT-hDAT function in an influx-preferring conformation. We now interrogate the basis of the mutants' altered function with respect to membrane conductance and Na(+) sensitivity. The hDAT constructs were expressed in Xenopus oocytes to investigate if heightened membrane potential would explain the efflux characteristics of T62D-hDAT. In the absence of substrate, all constructs displayed identical resting membrane potentials. Substrate-induced inward currents were present in oocytes expressing WT- and T62A-hDAT but not T62D-hDAT, suggesting equal bidirectional ion flow through T62D-hDAT.
2.Copper(II) triflate catalyzed amination of 1,3-dicarbonyl compounds.
Ton TM1, Himawan F, Chang JW, Chan PW. Chemistry. 2012 Sep 17;18(38):12020-7. doi: 10.1002/chem.201201219. Epub 2012 Aug 13.
A method to prepare α,α-acyl amino acid derivatives efficiently by Cu(OTf)(2)+1,10-phenanthroline (1,10-phen)-catalyzed amination of 1,3-dicarbonyl compounds with PhI=NSO(2) Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper-nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α-aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3-styryl-2-benzoyl-L-alanine.