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Hydrogen bonds play a crucial role in many biochemical processes and in supramolecular chemistry. In this study, we show quantum chemically that neither aromaticity nor other forms of π assistance are responsible for the enhanced stability of the hydrogen bonds in adenine-thymine (AT) DNA base pairs. This follows from extensive bonding analyses of AT and smaller analogs thereof, based on dispersion-corrected density functional theory (DFT). Removing the aromatic rings of either A or T has no effect on the Watson-Crick bond strength. Only when the smaller mimics become saturated, that is, when the hydrogen-bond acceptor and donor groups go from sp2 to sp3, does the stability of the resulting model complexes suddenly drop. Bonding analyses based on quantitative Kohn-Sham molecular orbital theory and corresponding energy decomposition analyses (EDA) show that the stronger hydrogen bonds in the unsaturated model complexes and in AT stem from stronger electrostatic interactions as well as enhanced donor-acceptor interactions in the σ-electron system, with the covalency being responsible for shortening the hydrogen bonds in these dimers. [ABSTRACT FROM AUTHOR]

Abstract: The title proton transfer complex was isolated from the reaction of CuCl2·2H2O with pyridine-2,6-dicarboxylic acid (dipic-H2) in presence of 3-amino-1-propanol (PA) under reflux condition. It was thoroughly characterized by FAB-mass, FT-IR, electronic (ligand field), EPR spectroscopic and X-ray crystallographic techniques. The complex crystallizes in the space group C1c1 of the monoclinic system. The unit cell parameters are, a =17.247(5), b =20.058(5)Å, c =15.320(4)Å and β =109.235(5)°. Extensive H-bonding between the complex anion [Cu(dipic)2]2− and the surrounding cations [PA-H]+ results in a 3D network, supported with additional π–π interactions of the ligand (dipic)2− neighboring units. The SOD mimic activity of the present complex was also examined using NBT assay. [Copyright &y& Elsevier]

The synthesis of a novel Phe-Ala dipeptide mimic, built up on a diazaspirocyclic lactam core, is presented. This new scaffold was evaluated for conformational mimicry of reverse turn by combining molecular modeling, IR, NMR, and X-ray diffraction experiments. All these tools agree on the presence of a strong intramolecular hydrogen bond, thus demonstrating the ability of this spiro compound to act as a type II′ β-turn inducer. [ABSTRACT FROM AUTHOR]

Background: The study and comparison of protein-protein interfaces is essential for the understanding of the mechanisms of interaction between proteins. While there are many methods for comparing protein structures and protein binding sites, so far no methods have been reported for comparing the geometry of non-covalent interactions occurring at proteinprotein interfaces. Methodology/Principal Findings: Here we present a method for aligning non-covalent interactions between different protein-protein interfaces. The method aligns the vector representations of van der Waals interactions and hydrogen bonds based on their geometry. The method has been applied to a dataset which comprises a variety of protein-protein interfaces. The alignments are consistent to a large extent with the results obtained using two other complementary approaches. In addition, we apply the method to three examples of protein mimicry. The method successfully aligns respective interfaces and allows for recognizing conserved interface regions. Conclusions/Significance: The Galinter method has been validated in the comparison of interfaces in which homologous subunits are involved, including cases of mimicry. The method is also applicable to comparing interfaces involving nonpeptidic compounds. Galinter assists users in identifying local interface regions with similar patterns of non-covalent interactions. This is particularly relevant to the investigation of the molecular basis of interaction mimicry. [ABSTRACT FROM AUTHOR]

α,γ- and β,γ-hybrid peptides, which are composed of two different homologous amino acid constituents in alternate order, are suggested as novel classes of peptide foldamers. On the basis of a systematic conformational search employing the methods of ab initio MO theory, the possibilities for the formation of periodic secondary structures in these systems are described. The conformational analysis provides a great number of helix conformers widely differing in energy, which can be arranged into three groups: (i) helices with all hydrogen bonds formed in forward direction along the sequence, (ii) helices with all hydrogen bonds in backward direction, and (iii) helices with alternate hydrogen-bond directions (mixed or β-helices). Most stable are representatives of β-helices, but their stability decreases considerably in more polar environments in comparison to helix conformers from the other two classes. There is a great similarity between the overall topology of the most stable hybrid peptide helices and typical helices of peptides which are exclusively composed of a single type of homologous amino acids. Thus, the helices of the β,γ-hybrid peptides mimic perfectly those of the native α-peptides as, for instance, the well-known α-helix, whereas the most stable helix conformers of α,γ-hybrid peptides correspond well to the overall structure of β-peptide helices. The two suggested novel hybrid peptide classes expand considerably the pool of peptide foldamers and may be promising tools in peptide design and in material sciences. [ABSTRACT FROM AUTHOR]

The article focuses on the design, synthesis, and structural analysis of a novel and extendable foldamer which mimics the rigidity and side chain position on β-strands. It explores the possibility of the application of foldamer to the inhibition of therapeutically relevant interactions. It describes the foldamer scaffold as based 2,2-disubstituted indolin-3-ones in which intramolecular hydrogen bonding has indicated a conformation that mimics the β-strand's residues.

The article introduces the newly designed cross-linked poly(n-butyl acrylate) network. This new material mimics the strength and elasticity of muscle protein titin. Its side chains that could form four hydrogen bonds carry long-chain terminal olefinic groups, which provides two levels of chain cross-linking through ring-closing metathesis formed flexible covalent links between the hydrogen bonding pairs. Compared to a control material with a poly(ethylene glycol) cross-link, its tensile strength increased by 700% for similar elongations at a cross-link density of 6%.