Activity-based Ubiquitin probes(Ub-ABPs)carrying a reporter group have emerged as effective tools for the investigation of deubiquitinating enzymes(DUBs),such as studying the molecular mechanism of DUBs,profiling new DUBs.But so far,the synthesis of commonly used biotin-bearing Ub-ABPs is a technical challenge.Here,we report a one-pot semi-synthetic strategy for the acquiring of Ub-ABPs carrying a biotin tag through sequential enzymatic ligation,N-S acyl transfer and aminolysis reaction without any purification steps.These probes enable to capture the different family of DUBs for enrichment and immunoblotting using the attached biotin tag.
Yu WangQiong XiaXiao HuaYanyan GuoJing ShiYi-Ming Li
Surface hydrophilization is required for numbers of applications such as biosensor,biomedical implants and marine coating.However,the preparation of hydrophilic surface from a solid substrate still suffers from limited thicknesses,complex procedures,restricted substrates and harsh conditions.Herein,a method based on in-situ aminolysis of poly(pentafluorophenyl acrylate)(pPFPA)capable of generating arbitrary hydrophilic surface is proposed,enabling high design freedom and abundant choices of hydrophilic molecules.Simply immersing pPFPA coated substrates into 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate(ADPS),β-alanine and amine-terminal poly(ethylene glycol)(NH2-PEG)solutions for two hours drastically reduces the water contact angle of the corresponding surfaces,indicating the high efficiency and excellent generality of such method.Systematical studies reveal that these coatings are able to mitigate fog formation,self-clean the oil contaminant and exhibit excellent antifouling performance against algae.Notably,relying on the fast and quantitative feature of the aminolysis,these hydrophilic surfaces possess excellent regeneration capability and well-recover their hydrophilic feature after being physically damaged.This work represents a facile and universal way to fabricate versatile hydrophilic surfaces for multi-functional applications such as self-cleaning,patterning,sensing,antifogging and anti-biofouling.
The aminolysis of ethyl acetate was promoted significantly via continuous reaction in a tubular reactor.Npropylacetamide was thus synthesized without presence of solvent and catalyst.The optimum conditions were obtained as follows:the reaction temperature is 218℃,the reaction pressure is 3.5 MPa,the molar ratio(ethyl acetate:N-propylamine)is 1:1,and the residence time is 350 min.Accordingly,the conversion of ethyl acetate is up to94.8%.Furthermore,the kinetics of the rapid reaction stage(when the conversion of ethyl acetate is 20%-80%)can be expressed as Ink=-4629.441/T+2.1366,and the apparent activation energy is Ea=38489 J·mol-1.
A comprehensive exploration of the aminolysis mechanism for methyl indole-3-acetate with ammonia is carried out by employing the B3 LYP/6-311++G(d,p), M06-2 X/6-311++G(d,p) and MP2/6-311++G(d,p)//M06-2 X/6-311++G(d,p) levels. Two alterative reaction channels of the concerted and addition/elimination stepwise processes including the uncatalyzed, base-catalyzed reactions are taken into consideration. Subsequently, the substituent effects and solvent effects in methanol are also evaluated at the M06-2 X/6-311++G(d,p) level. The calculated results indicate that the calculated values of M06-2 X level are quite close to those of MP2, the stepwise pathway has more advantages to the concerted one for all of the reaction processes and the catalyst facilitates the proton migration and decreases the energy barriers as well. It is shown that the most preferred mechanism is the based-catalyzed stepwise process, the substituent of NH2 group slightly accelerates all the aminolysis reaction processes, and the solvent effect does not remarkably change the mechanism of the reaction.
Direct aminolysis of selenoester in aqueous media was investigated as a glycopeptide ligation strategy.This strategy allows the peptide and glycopeptide ligation to proceed smoothly(even with hindered amino acids) without the need of cysteine residue, N-terminal thiol auxiliary or coupling additive, and to afford the corresponding amide products in excellent yields. No epimerization was observed during ligation reations. In this work, the selenoester of unprotected glycopeptide was readily prepared, and the direct aminolysis of glycopeptide selenoester was successfully applied to synthesize MUC1 mucin sequence efficiently.
This paper reports a computational study elucidating reaction mechanism for amide bond formation from esters and amines catalyzed by acetic acid. Two optional mechanisms（namely, classic stepwise and concerted acyl substitution mechanisms） have been studied. Calculation results establish the reaction energy profiles of both mechanisms and locate all the intermediates and transition states in both catalytic cycles. Our results propose that the concerted acyl substitution mechanism may be more likely wherein the formation of CààN bond and the cleavage of CààO bond occur concurrently without the need of rehybridization of the carbonyl carbon. This is also consistent with the fact that no significant racemization/epimerization were observed in the amide products when asymmetric esters and/or amines were used as the reactants, because concerted acyl substitution mechanism precludes the intermediacy of tetrahedral adducts and the accompanying generation/elimination of new chiral centers.Further discussion implies that the concerted acyl substitution mechanism may widely occur in related amidation reactions in the presence of different types of coupling reagents.
