The intramolecularly hydrogen-bonded bichromophoric tetrapyrrole pigments, bilirubin-IXa and mesobilirubin-XIIIa, adopt either of two folded, intramolecularly hydrogen-bonded, enantiomeric conformations which are in dynamic equilibrium in solution. Added human serum albumin binds preferentially, although not necessarily exclusively, to one conformational enantiomer, and the solutions exhibit bi...

A new class of polypeptide helices in hybrid sequences containing alpha-, beta-, and gamma-residues is described. The molecular conformations in crystals determined for the synthetic peptides Boc-Leu-Phe-Val-Aib-betaPhe-Leu-Phe-Val-OMe 1 (betaPhe: (S)-beta3-homophenylalanine) and Boc-Aib-Gpn-Aib-Gpn-OMe 2(Gpn: 1-(aminomethyl)cyclohexaneacetic acid) reveal expanded helical turns in the hybrid se...

The topology of β-sheets is defined by the pattern of hydrogenbonded strand pairing. Therefore, predicting hydrogen bonded strand partners is a fundamental step towards predicting β-sheet topology. In this work we report a new strand pairing algorithm. Our algorithm attempts to mimic elements of the folding process. Namely, in addition to ensuring that the predicted hydrogen bonded strand pairs...

Despite the inherently quantum mechanical nature of hydrogen bonding, it is unclear how nuclear quantum effects (NQEs) alter the strengths of hydrogen bonds. With this in mind, we use ab initio path integral molecular dynamics to determine the absolute contribution of NQEs to the binding in DNA base pair complexes, arguably the most important hydrogen-bonded systems of all. We find that dependi...

The constituents of the title 1:1 co-crystal, C(7)H(6)O(2)·C(14)H(12)N(2), are connected into dimeric aggregates by a bifurcated O-H⋯N hydrogen bond; the hydroxyl-H atom is hydrogen bonded to the two N atoms of the 2,9-dimethyl-phenanthroline. The hydrogen-bonded residues are almost orthogonal to each other [dihedral angle = 78.56 (7) °]. In the crystal packing, the aggregates are assembled int...

Energetics and geometrical structures of neutral, (H2O)n, and ionized, (H2O)n, water clusters, with n ) 2-5, are investigated using local-spin-density functional electronic structure calculations with exchange-correlation gradient corrections. While the ground-state structures of the neutral clusters are hydrogen-bonded cyclic ones, those of the molecular ions are noncyclic. The lowest energy i...

Sulfur K-edge X-ray absorption spectroscopy of a hydrogen-bonded elongated [Fe4S4]2+ cube is reported. The data show that this synthetic cube is less covalent than a normal compressed cube with no hydrogen bonding. DFT calculations reveal that the observed difference in electronic structure has significant contributions from both the cluster distortion and from hydrogen bonding. The elongated a...

We present a systematic study on the gas-phase hydrogen-bonded complexes formed between formic acid and hydroperoxyl radical, which has been carried out by using B3LYP and CCSD(T) theoretical approaches in connection with the 6-311+G(2df,2p) basis set. For all complexes we have employed the AIM theory by Bader and the NBO partition scheme by Weinhold to analyze the bonding features. We have fou...

A novel inorganic-organic hybrid supramolecular macrocyclic compound, (4-nitroanilinium) (18-crown-6)(PF6)(1), was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. Crystal 1 is found to comprise 1D C–H···F–P hydrogen-bonded chains of (4-nitroanilinium+) (18-crown...

We report the liquid-phase ultrasonic exfoliation of two layered hydrogen-bonded frameworks into monolayer, micron-sized, and water-stable nanosheets (HONs) connected purely by hydrogen-bonding interactions.