Gradual opening of Smc arms in prokaryotic condensin

SummaryMulti-subunit SMC ATPases control chromosome superstructure apparently by catalyzing a DNA-loop-extrusion reaction. SMC proteins harbor an ABC-type ATPase ‘head’ and a ‘hinge’ dimerization domain connected by a coiled coil ‘arm’. Two arms in a SMC dimer can co-align, thereby forming a rod-shaped particle. Upon ATP binding, SMC heads engage, and arms are thought to separate. Here, we studied the shape of B. subtilis Smc-ScpAB by electron-spin resonance spectroscopy. Arm separation was readily detected proximal to the heads in the absence of ligands, while separation near the hinge largely depended on ATP and DNA. Artificial blockage of arm opening eliminated DNA stimulation of ATP hydrolysis, but did not prevent basal ATPase activity. We identified an arm-to-arm contact as being important for controlling the molecular transformations. Point mutations at this arm interface eliminate Smc function. We propose that partially open, intermediary conformations provide directionality to SMC DNA translocation by binding suitable DNA substrates.

PdII insertion-triggered meso-carbon extrusion of N-fused pentaphyrin to form N-fused sapphyrin PdII complexes

meso-Carbon extrusion reaction was found in the N-fused [22]pentaphyrin(1.1.1.1.1) scaffold upon PdII insertion to give N-fused [22]pentaphyrin(1.1.1.1.0) (i.e. [22]sapphyrin) PdII complexes.

Preparation and Properties of Nylon 6,6 Grafted Graphene Composites

Nylon 6,6 composite fiber containing grafted graphene (nylon 6,6-g-graphene) was prepared by nylon and graphene grafted with acyl chloride (graphene-COCl) through extrusion reaction. Graphene-COCl was prepared through acid-treated reacting, graphene with thionyl chloride functional group. The chemical structure of nylon 6,6-g-graphene obtained using reactive extrusion technique was characterized using Fourier transform infrared spectrometer. It was found that this kind of composite fiber has the characteristics of less amount of graphene and excellent mechanical properties and has certain application prospects. Nylon 6,6-g-graphene dispersed evenly in the Nylon composite. But pristine graphene exhibited aggregate structure when composite was produced by pristine graphene through reactive extrusion. The composite reinforcement was increased obviously with the increase content of grafted graphene. After examined, the nylon/nylon 6,6-g-graphene with a certain content grafted graphene composite exhibited high level of reinforcement, and mechanical properties were improved.

Synthesis of fully substituted pyrazoles from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides via a [[3 + 3] − 1] pathway

Pyrazoles were synthesized from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides via an unusual [[3 + 3] − 1] pathway, involving a formal [3 + 3] cascade cyclization followed by a spontaneous ring-contraction/sulfur extrusion reaction.

TBHP promoted demethylation of α-amino carbonyl compounds: a concise approach to substituted γ-lactams

A novel tert-butyl hydroperoxide (TBHP) promoted CH2-extrusion reaction of α-amino carbonyl compounds has been developed, which is driven by a demethylenation process to give various ring contraction products γ-lactams under radical conditions.