A lysine-based 2:1-[α/aza]-pseudopeptide series used as additives in polymeric membranes for CO capture: synthesis, structural studies, and application.

The current study presents for the first time the synthesis of a new 2:1-[α/aza]-pseudopeptide series possessing charged amino acids (, lysine) and aims at studying the influences of chirality, backbone length, and the nature of the lysine side chains on the conformation of the 2:1-[α/aza]-oligomers in solution using NMR, FTIR spectroscopy and molecular dynamic calculations. The spectroscopic results emphasized the conservation of the β-turn conformation adopted by the trimers regardless of the chirality which demonstrated a noticeable effect on the conformation of homochiral hexamer (8c) compared with the hetero-analogue (8d). The molecular dynamic calculations predicted that the chirality and the side chain of the lysine residues caused a little distortion from the classical β-turn conformation in the case of short trimer sequences (7c and 7d), while the chirality and the backbone length exerted more distortion on the β-turn adopted by the longer hexamer sequences (8c and 8d).

On the Observation of N Quadrupole Resonance Transitions in Water Proton NMR Relaxometry Dispersion Curves: The Case of a Labile NH Grouping in a Semirigid Molecular Moiety.

The electric field gradient tensor (considered here at the level of a nitrogen nucleus) can be described by two parameters: the largest element in the (,,) principal axis system, denoted by (leading to the nuclear quadrupole coupling), and the asymmetry parameter η = (|| - ||)/|| with || > || > ||. The frequencies of the three nitrogen-14 nuclear quadrupole resonance (NQR) transitions depend on both parameters but, for sensitivity reasons, their determination may be especially difficult and time consuming. For a partly rigid NH grouping with a labile proton, water nuclear magnetic resonance (NMR) relaxometry curves may exhibit these three transitions (dubbed quadrupolar dips or quadrupole relaxation enhancement (QRE)), provided that the NH grouping belongs to a moiety possessing a sufficient degree of ordering.

Emerging low-molecular weight nucleopeptide-based hydrogels: state of the art, applications, challenges and perspectives.

Over the last twenty years, low-molecular weight gelators and, in particular, peptide-based hydrogels, have drawn great attention from scientists thanks to both their inherent advantages in terms of properties and their high modularity (, number and nature of the amino acids). These supramolecular hydrogels originate from specific peptide self-assembly processes that can be driven, modulated and optimized specific chemical modifications brought to the peptide sequence. Among them, the incorporation of nucleobases, another class of biomolecules well-known for their abilities to self-assemble, has recently appeared as a new promising and burgeoning approach to finely design supramolecular hydrogels.

Co-assembly and multicomponent hydrogel formation upon mixing nucleobase-containing peptides.

Peptide-based hydrogels are physical gels formed through specific supramolecular self-assembling processes, leading to ordered nanostructures which constitute the water entrapping scaffold of the soft material. Thanks to the inherent properties of peptides, these hydrogels are highly considered in the biomedical domain and open new horizons in terms of application in advanced therapies and biotechnologies. The use of one, and only one, native peptide to formulate a gel is by far the most reported approach to design such materials, but suffers from several limitations, including in terms of mechanical properties.

Cyclohexamer [-(d-Phe-azaPhe-Ala)-]: good candidate to formulate supramolecular organogels.

Molecular self-assembly is a fascinating process which has become an area of great interest in supramolecular chemistry, as it leads in certain cases to molecular gels. Organogels formulated from low molecular weight compounds (LMWOGs) have attracted much interest in the past decades due to their applications as new soft materials. Herein, we report on the ability of the cyclic pseudopeptide cyclo-[-(d-Phe-azaPhe-Ala)-] (2) to self-assemble in some aromatic solvents and to form organogels driven by non-covalent forces, mainly hydrogen bonding and π-stacking interactions.

Improving and fine-tuning the properties of peptide-based hydrogels via incorporation of peptide nucleic acids.

Peptide self-assemblies have attracted intense research interest over the last few decades thanks to their implications in key biological processes (e.g., amyloid formation) and their use in biotechnological and (bio)material fields.

Both metal-chelating and free radical-scavenging synthetic pentapeptides as efficient inhibitors of reactive oxygen species generation.

Reactive oxygen species (ROS) are major sources of oxidative stress playing prominent roles in the development of several pathologies including cardiovascular and neurodegenerative diseases or cancers. The presence of transition biometal ions, specifically copper and iron, induces ROS formation by catalyzing the reduction of molecular oxygen to superoxide anion (O2˙-), hydrogen peroxide (H2O2) and hydroxyl (HO˙) radical. To limit ROS production and their detrimental effects, we report on the synthesis, physicochemical studies and antioxidant assays of an innovative series of synthetic pentapeptides exhibiting a dual direct/indirect mode of action, both as iron(iii)-chelators and as radical scavengers.

Unprecedented chain-length-dependent conformational conversion between 11/9 and 18/16 helix in α/β-hybrid peptides.

α,β-Hybrid oligomers of varying lengths with alternating proteogenic α-amino acid and the rigid β(2,3,3) -trisubstituted bicyclic amino acid ABOC residues were studied using both X-ray crystal and NMR solution structures. While only an 11/9 helix was obtained in the solid state regardless of the length of the oligomers, conformational polymorphism as a chain-length-dependent phenomenon was observed in solution. Consistent with DFT calculations, we established that short oligomers adopted an 11/9 helix, whereas an 18/16 helix was favored for longer oligomers in solution.

Mixed oligoureas based on constrained bicyclic and acyclic β-amino acids derivatives: on the significance of the subunit configuration for folding.

The combination of a non-functionalized constrained bicyclo[2.2.2]octane motif along with urea linkages allowed the formation of a highly rigid 2.

Cyclic enkephalins with a diversely substituted guanidine bridge or a thiourea bridge: synthesis, biological and structural evaluations.

Two series of 22 and 15 atom cyclic enkephalins incorporating a diversely substituted guanidine bridge have been prepared to assess the potential effect of the bridge substitutions on their opioid activity profile. The most notable results were obtained with the shortest cyclic analogues, which showed a significant variation of their binding affinity toward μ and δ opioid receptors in relation to bridge substitution. NMR studies were performed to rationalize these data.

Helical oligomers of thiazole-based γ-amino acids: synthesis and structural studies.

9-Helix: 4-Amino(methyl)-1,3-thiazole-5-carboxylic acids (ATCs) were synthesized as new γ-amino acid building blocks. The structures of various ATC oligomers were analyzed in solution by CD and NMR spectroscopy and in the solid state by X-ray crystallography. The ATC sequences adopted a well-defined 9-helix structure in the solid state and in aprotic and protic organic solvents as well as in aqueous solution.

Robust helix formation in a new family of oligoureas based on a constrained bicyclic building block.

BAC for more: a constrained bicyclic building block with urea linkages is an efficient combination for the formation of a highly rigid helical system. This type of bicyclic amino carbamoyl (BAC) foldamer was studied both in solution and in the solid state. A robust H-bond (dotted line) network was found between the carbonyl oxygen atoms (red) and the amino groups (dark blue) within the helix.

(S)-ABOC: a rigid bicyclic β-amino acid as turn inducer.

In order to investigate the ability of the (S)-aminobicyclo[2.2.2]octane-2-carboxylic acid 1 (H-(S)-ABOC-OH) to induce reverse turns into peptides, two model tripeptides, in which this bicyclic unit was incorporated into the second position, were synthesized and analyzed by FT-IR, CD, NMR, and X-ray studies.

Noncationic dipeptide mimic oligomers as cell penetrating nonpeptides (CPNP).

Small oligomers of constrained dipeptide mimics have been synthesized as new vectors for intracellular delivery. They are highly internalized by cells and delivered to the lysosomes by an energy-dependent pathway. This new class of vectors referred to as cell penetrating nonpeptides (CPNP) possess the distinctive feature of being noncationic.

1H, 13C, and 15N resonance assignment of the C103S mutant of the N-terminal domain of DsbD from Neisseria meningitidis.

We report the nearly complete 1H, 13C, and 15N resonance assignments of the C103S mutant of the N-terminal domain of DsbD from Neisseria meningitides. Secondary structure determination using CSI method leads to the prediction of nine beta-sheet parts.

Solution structure and backbone dynamics of the cysteine 103 to serine mutant of the N-terminal domain of DsbD from Neisseria meningitidis.

The DsbD protein is essential for electron transfer from the cytoplasm to the periplasm of Gram-negative bacteria. Its N-terminal domain dispatches electrons coming from cytoplasmic thioredoxin (Trx), via its central transmembrane and C-terminal domains, to its periplasmic partners: DsbC, DsbE/CcmG, and DsbG. Previous structural studies described the latter proteins as Trx-like folds possessing a characteristic C-X-X-C motif able to generate a disulfide bond upon oxidation.

Solution structure and dynamics of the reduced and oxidized forms of the N-terminal domain of PilB from Neisseria meningitidis.

The secreted form of the PilB protein was proposed to be involved in pathogen survival fighting against the defensive host's oxidative burst. PilB protein is composed of three domains. The central and the C-terminal domains display methionine sulfoxide reductase A and B activities, respectively.

1H, 13C and 15N resonance assignment of the oxidized form (Cys(67)-Cys (70)) of the N-terminal domain of PilB from Neisseria meningitidis.

We report the nearly complete 1H, 13C and 15N resonance assignments of the oxidized form (Cys(67)-Cys(70)) of the N-terminal domain of PilB from Neisseria meningitidis. Secondary structure determination using CSI method and TALOS leads mainly to the prediction of 7 alpha-helical and 5 beta-sheet parts.

N,N'-linked oligoureas as foldamers: chain length requirements for helix formation in protic solvent investigated by circular dichroism, NMR spectroscopy, and molecular dynamics.

N,N'-linked oligoureas with proteinogenic side chains are peptide backbone mimetics belonging to the gamma-peptide lineage. In pyridine, heptamer 4 adopts a stable helical fold reminiscent of the 2.6(14) helical structure proposed for gamma-peptide foldamers.