Hydrogen bonding interactions between biological chromophores and their surrounding protein and solvent environment significantly affect the photochemical pathways of the chromophore and its biological function. A common first step in the dynamics of these systems is excited state proton transfer between the noncovalently bound molecules, which stabilizes the system against dissociation and pri...

A classic question regarding hydrogen bonds (H-bonds) concerns their symmetry. Is the hydrogen centered or is it closer to one donor and jumping between them? These possibilities correspond to singleand double-well potentials, respectively. The NMR method of isotopic perturbation can answer this question. It is illustrated with 3-hydroxy-2-phenylpropenal and then applied to dicarboxylate monoan...

> < ABSTRACT: The intramolecular helix backbone C O H— N hydrogen Ž . bonding energies in poly L-alanine a helices have been estimated both in vacuum and in an aqueous environment using the parameter sets of five of the most commonly used force fields for modeling biomolecules, namely AMBER, CHARMM, ECEPP, GROMOS, and OPLS. The relative capabilities of these force fields in describing the H-bon...

Why does a given protein structure form and why is this structure stable? These fundamental biochemical questions remain fascinating and challenging problems because the physical bases of the forces that govern protein structure, stability and folding are still not well understood. Now, a general concept of hydrogen bonding in proteins is emerging. This concept involves not only N-H and O-H don...

The scientific community is allocating more and more resources to space missions and astronomical observations dedicated to the search for life beyond Earth. This experimental endeavor needs to be backed by a theoretical framework aimed at defining universal criteria for the existence of life. With this aim in mind, we have explored which chemical and physical properties should be expected for ...

Water has anomalous properties that emanate from its hydrogen-bond-induced structure. Most of the unique properties ofwater are related to the network of strong three-dimensional hydrogen bonds that interconnect the water molecules [1, 2]. According to Stillinger [3], water has a preferential three-dimensional tetrahedral structure containing a few free or single-bonded water molecules. A simul...

The asymmetric unit of the title compound, C(7)H(9)N(3)O(2), comprises two crystallographically independent mol-ecules (A and B). In each mol-ecule there is an intra-molecular O-H⋯O hydrogen bond making an S(6) ring motif. In the crystal, a pair of N-H⋯N hydrogen bonds link the two mol-ecules (A and B) into a dimer with an R(2) (2)(6) ring motif. The B mol-ecules are linked via pairs of N-H⋯O h...

A combination of neutron diffraction augmented with isotopic substitution and computer modeling using empirical potential structure refinement has been used to extract detailed structural information for L-glutamic acid dissolved in 2 M NaOH solution. This work shows that the tetrahedral hydrogen bonding network in water is severely disrupted by the addition of glutamic acid and NaOH, with the ...

In the crystal structure of the title compound, C(6)H(9)N(2) (+)·0.5C(4)H(2)O(4) (2-)·0.5C(4)H(6)O(4), the fumarate dianion and fumaric acid mol-ecule are located on inversion centres. The 2-amino-5-methyl-pyrimidinium cation inter-acts with the carboxyl-ate group of the fumarate anion through a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. These motifs are centrosymmetricall...