Control of secondary structure and morphology of peptide-guanidiniocarbonylpyrrole conjugates by variation of the chain length

Peptide amphiphiles with well-organized secondary structure are an important family of molecules that are known to assemble into a variety of nanostructures.In this work,we present three guanidiniocarbonylpyrrole(GCP)containing peptide amphiphiles,which show versatile morphology and secondary structure changes as a result of different chain lengths and in different concentration regimes.The random coil conformation,α-helix,andβ-sheet are obtained for peptide 1,peptide 2,and peptide 3,respectively under neutral aqueous conditions.Furthermore,all peptide amphiphiles can aggregate to form nanoparticles at low concentrations.However,at high concentrations,peptide 1 selfassembles into left-ha nded twisted helical fibers,while longer bamboo-like mo rphology can be obse rved exclusively for peptide 2.For peptide 3,freshly prepared samples show uniform spherical morphology,whereas an obvious morphological transition from original nanoparticles to disordered fibers was realized after incubating for one week.These fascinating morphology changes were determined by the combination of circular dichroism,dynamic light scattering,transmission electron microscopy,atomic force microscopy,and theoretical calculations.

Visible-light-induced three-component reaction of quinoxalin-2(1H)-ones,alkenes and CF_(3)SO_(2)Na leading to 3-trifluoroalkylated quinoxalin-2(1H)-ones

A facile and metal-free visible-light-enabled three-component reaction of quinoxalin-2(1 H)-ones,alkenes and CF_(3)SO_(2)Na has been developed under air at room temperature.This photocatalytic tandem reaction using 4 CzIPN as the photocatalyst and air as the green oxidant,provides a mild and environmentally friendly approach to access a series of 3-trifluoroalkylated quinoxalin-2(1 H)-ones.

Silver-mediated aminophosphinoylation of propargyl alcohols with aromatic amines and H-phosphine oxides leading to α-aminophosphine oxides

A new silver mediated aminophosphinoylation of propargyl alcohols with aromatic amines and Hphosphine oxides for the construction of a-aminophosphine oxides has been developed.The C-N and C-P bond could be efficiently formed in one pot operation via sequential C-C and C-O bond cleavage of propargylic alcohols.This present methodology,which not only provides a simple and alternative strategy for the synthesis of α-aminophosphine oxides,but also opens a new window for the cleavage reactions of propargyl alcohols via dealkynalation coupling.

Catalyst-and additive-free selective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones leading to sulfonylated γ-butyrolactams

A convenient and regioselective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones has been developed to access a series of sulfonylated γ-butyrolactams.The present reaction could be efficiently conducted under catalyst-and additive-free conditions,in which C-S and C-C bonds were selectively constructed in one-pot procedure.

Metal-free visible-light-induced oxidative cyclization reaction of 1,6-enynes and arylsulfinic acids leading to sulfonylated benzofurans

A new and convenient visible-light-induced method has been developed for the synthesis of sulfonylated benzofurans via oxidative cyclization reaction of 1,6-enynes and arylsulfinic acids.This reaction was carried out under metal-free and mild conditions,in which the C-S,C-C and C=O bonds could be sequentially formed in one pot operation.

Visible-light-initiated 4CzIPN catalyzed multi-component tandem reactions to assemble sulfonated quinoxalin-2(1H)-ones

A mild and efficient photochemical multi-component tandem reaction of quinoxalin-2(1H)-ones, alkenes and sulfinic acids is reported. This tandem reaction could be conveniently carried out at room temperature by employing 4Cz IPN as the metal-free photocatalyst and dioxygen(air) as the environmentally benign oxidant. A number of sulfonated quinoxalin-2(1H)-ones were obtained in satisfactory yields with favorable functional group tolerance. Radical trapping experiment and fluorescence quenching experiments were performed to elucidate this visible-light mediated radical reaction process.

Pillar[5]arene-modified peptide-guanidiniocarbonylpyrrol amphiphiles with gene transfection properties

Pillar[5]arene-modified amphiphilic peptides with varying numbers of guanidiniocarbonylpyrrol(GCP)moieties have been successfully synthesized,which can self-assemble to multivalent cationic superstructures in aqueous solutions.These assembled peptides can condense DNA into various compact multimolecular aggregates to achieve successful intracellular DNA delivery and demonstrate great potential for gene transfection.Transfection efficiencies of the self-assembled superstructures have been evaluated in vitro with He La and HEK 293T cells.We demonstrate that GCP moiety could enhance the cell transfection ability,owing to its excellent binding towards cytomembrane.It was also found that subtle structure difference in peptides 2 and 3 could result in distinct transfection efficacy,which makes it possible to gain an in-depth understanding of their structure-activity relationship.This work presents a good example of rational structural design in achieving effective gene transfection vectors.