A new strategy for synthesis of branched cyclic peptide by Asn side-chain hydrazide ligation

Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO₂ and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics.     

Experimental studies on active control of a dynamic system via a time-delayed absorber

The traditional passive absorber is fully effective within a narrow and certain frequency band.To solve this problem,a time-delayed acceleration feedback is introduced to convert a passive absorber into an active one.Both the inherent and the intentional time delays are included.The former mainly comes from signal acquiring and processing,computing,and applying the actuation force,and its value is fixed.The latter is introduced in the controller,and its value is actively adjustable.Firstly,the mechanical model is established and the frequency response equations are obtained.The regions of stability are delineated in the plane of control parameters.Secondly,the design scheme of control parameters is performed to help select the values of the feedback gain and time delay.Thirdly,the experimental studies are conducted.Effects of both negative and positive feedback control are investigated.Experimental results show that the proper choices of control parameters may broaden the effective frequency band of vibration absorption.Moreover,the time-delayed absorber greatly suppresses the resonant response of the primary system when the passive absorber totally fails.The experimental results are in good agreement with the theoretical predictions and numerical simulations.     

Imine Macrocycle with a Deep Cavity: Guest‐Selected Formation of syn/anti Configuration and Guest‐Controlled Reconfiguration

A dynamic covalent bond is one of the ideal linkages for the construction of large and robust organic architectures. In the present article, we show how organic templates can efficiently transform a complex dynamic imine library into a dynamic imine macrocycle. Not only is the constitution well controlled, but also the syn/anti host configuration is efficiently selected and even the orientation of the guest in the asymmetric cavity of the host can be well aligned. This is attributed to the delicate balance and the cooperation of multiple noncovalent interactions between the hosts and the guests. Through sequential additions of three guests in appropriate amounts, controlled structural reconfiguration of dynamic covalent architectures has been achieved for the first time.