1,721,110 research outputs found
Intrinsically Photoswitchable α/β Peptides toward Two-State Foldamers
No full textA simple, unsaturated, E–Z photoisomerizable β‐amino acid, (Z)‐3‐aminoprop‐2‐enoic acid, has been introduced into peptide foldamers through a one‐pot chemical coupling, based on Pd/Cu‐catalyzed olefin oxidative amidation, between two peptide segments carrying, respectively, a ‐Gly‐NH2 residue at the C‐terminus and an acryloyl group at the N‐terminus. Reversible conversion between the Z and E configurations of the 3‐aminoprop‐2‐enoic linkage was achieved photochemically. A crystallographic analysis on two model compounds shed light on the consequences, in terms of 3D structure and self‐association properties, brought about by the different configuration of the unsaturated linkage. As a proof of concept, E–Z photoisomerization of a 3‐aminoprop‐2‐enoic acid residue, inserted as the junction between two conformationally distinct peptide domains (one helical while the other β‐sheet promoter), allowed supramolecular self‐association to be reversibly turned on/off
Peptido[2]Rotaxanes with Amino Acids Containing either Functional Groups or Folded Peptide Segments in the Axle.
No full textEnhancement of the Helical Content and Stability Induced in a Linear Oligopeptide by an i, i+4 Intramolecularly Double Stapled, Overlapping, Bicyclic [31,22,5]-(E)ene Motif
No full textTwo consecutive i, i+4 intramolecular, side chain-to-side chain, macrocyclizations of different type carried out on a preformed, partially helical peptide result in a largely predominant, double stapled, overlapping, bicyclic [31,22,5]-(E)ene motif. A detailed ECD and NMR conformational study revealed a significant enhancement of the original helical content and stability, accompanied by an increase of the alpha-helix amount over that of the 3(10)-helix
N-Methylation of N-alpha-Acetylated, C-alpha-Ethylated, Fully-Extended Homo-Peptides: Synthetic and Conformational Aspects.
No full textBulky toroidal and vesicular self-assembled nanostructures from fullerene end-capped rod-like polymers
Full text linkIn this work{,} we present novel fullerene (C60) end-capped rod-like polypeptide-polymers{,} obtained by one-pot thiol-ene chemistry. These systems are able to self-assemble in water creating precise bulky microstructures of toroidal or vesicular shapes. Independent molecular dynamics simulations supported the observed experimental results
N-methylation of N-alpha-acylated, fully C-alpha-methylated, linear, folded peptides: Synthetic and conformational aspects
No full textPeptides characterized by single or multiple N-methylated, C-alpha-trisubstituted (e.g., protein) amino acids are of great interest in medicinal chemistry. Several naturally occurring peptides, remarkably stable to enzymatic attacks, are based on N-methylated residues. The classical conditions (CH3I/Ag2O in DMF, 24 h, room temperature) for N-methylation of the peptide function are useful tools for distinguishing solvent exposed from intramolecularly H-bonded -CO-NH-groups in peptides. In this work we have extended this reaction to N-alpha-acylated, linear peptides based exclusively on helicogenic C-alpha-tetrasubstituted alpha-amino acids, e.g., Aib (alpha-aminoisobutyric acid) or (alpha Me)Nva (C-alpha-methyl norvaline) residues. Under the experimental conditions used, only amide monomethylation (on the N-terminal, acylated, residue) takes place. Methylation of internal peptide groups linking two C-alpha-tetrasubstituted residues was not observed
Peptide-based rotaxanes and catenanes: an emerging class of supramolecular chemistry systems
No full text[2]Rotaxanes are interlocked molecular systems in which the cavity of a macrocycle (wheel) is threaded by a linear compound (axle). The axle is held in place principally by a sterically demanding moiety (stopper) at each end. If the two ends of a rotaxane are covalently linked together, then an assembly of two intertwined macrocycles (termed [2]catenane) is generated. Although rotaxanes and catenanes have been extensively investigated by several research groups, only a limited amount of studies has been devoted to these systems when a peptide molecule characterizes either the axle or the wheel(s) (or both). The purpose of this short conceptual overview is to summarize recent findings on synthetic and naturally occurring peptide-based [2]rotaxanes, [3]rotaxanes, and [2]catenanes and discuss future prospects for the research in this emerging area of supramolecular chemistry
Anomalous Distance Dependence of Electron Transfer across Peptide Bridges
No full textThe first investigation on the distance dependence of a dissociative electron transfer process across peptide bridges is reported. This study was carried out by using a series of donor−peptide−acceptor systems in which the donor is a phthalimido moiety, the peptide bridges are provided by α-aminoisobutyric acid (Aib) homooligomers, and the acceptor is a peroxide functional group. The intramolecular electron transfer from the electrogenerated phthalimido radical anion to the peroxide was studied in comparison with the thermodynamic and kinetic information obtained with models of the acceptor and the donor
First Rigid Peptide Foldamers with an Alternating cis-trans Amide Sequence. An Oligomeric Building Block for the Construction of New Helices, Large-Ring Correlates, and Nanotubes
No full textAs part of a program evaluating homochiral and heterochiral amino- and carboxylic acid-substituted gamma -lactams as conformationally constrained dipeptide building blocks, we have synthesized by the solid-phase technique and assessed by X-ray diffraction the crystal-state structure of the terminally blocked homotrimer from (2S,4R)-4-amino-5-oxopyrrolidine-2-carboxylic acid, characterized by a unique, alternating cis-trans amide sequence. Using computer modeling, we also showed that the rigid conformation of the trimer can be exploited as a template to construct novel linear oligopeptide foldamers and large-ring cyclic correlates with self-recognizing properties
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