Hydrogen bonds are weak, generally intermolecular bonds, which hold much of soft matter together as well as the condensed phases of water, network liquids, and many ferroelectric crystals. The small mass of hydrogen means that they are inherently quantum mechanical in nature, and effects such as zero-point motion and tunneling must be considered, though all too often these effects are not consi...

The isomeric N-(iodophenyl)nitrobenzamides, C(13)H(9)IN(2)O(3), all form different three-dimensional framework structures. Molecules of N-(2-iodophenyl)-3-nitrobenzamide (II) are linked by a combination of N-H...O and C-H...O hydrogen bonds and a two-centre iodo...carbonyl interaction. The supramolecular structure of N-(2-iodophenyl)-4-nitrobenzamide (III) is built from one N-H...O and two C-H....

The structures of five hydrogen-bonded adducts of triphenylsilanol, Ph3SiOH, with diamines have been determined. In the 4:1 adduct formed with 1,4-diazabicyclo[2.2.2]octane, (Ph3SiOH)4.C6H12N2 (I) (triclinic, P1, Z' = 2), there are two independent five-component aggregates built from O-H...N and O-H...O hydrogen bonds, in one of which the diamine exhibits orientational disorder: these two aggre...

In the title hydrated salt, 2,4,6-triamino-1,3,5-triazin-1-ium perchlorate monohydrate, C(3)H(7)N(6) (+)·ClO(4) (-)·H(2)O, the constituents are linked via hydrogen bonds of the O-H⋯O, N-H⋯O, N-H⋯N and N-H⋯Cl types. All the H atoms of the melaminium cation are involved in the hydrogen bonds. The melaminium residues are inter-connected by four N-H⋯N hydrogen bonds, forming chains parallel to (111...

In the title salt, C(6)H(8)N(3) (+)·Cl(-), each pyridine-carbox-imid-amidate cation is linked to two symmetry-related cations through N-H⋯N hydrogen bonds, and to two chloride ions by N-H⋯Cl hydrogen bonds. The N-H⋯N hydrogen bonds involve the pyridine N atom and one NH(2) group. In the crystal, N-H⋯N and N-H⋯Cl hydrogen bonds extend the structure into two-dimensional layers. Weak C-H⋯Cl inter-...

The title compound, C(6)H(8)N(3) (+)·Cl(-)·H(2)O, crystallizes with three formula units in the asymmetric unit. The cations are non-planar with the -C(NH(2))(2) groups twisted out of the ring planes. Each pyridine carboximidamidate cation is linked to another cation through N-H⋯N hydrogen bonds, to chloride ions by N-H⋯Cl hydrogen bonds, and to water mol-ecules by N-H⋯O hydrogen bonds. Water mo...

In this paper, we consider RNA structures with arc-length 4 . First, we represent these structures as matrix models and zero-one linearprogramming problems. Then, we obtain an optimal solution for this problemusing an implicit enumeration method. The optimal solution corresponds toan RNA structure with the maximum number of hydrogen bonds.

There are three formula units in the asymmetric unit of the title compound, C(14)H(16)N(2)O(4)·H(2)O. Mol-ecules are linked by N-H⋯O hydrogen bonds into dimers with the common R(2) (2)(8) graph-set motif. Between dimers, single N-H⋯O hydrogen bonds are formed between the other N-H group of each pyrimidine ring and the hydroxyl groups. The water mol-ecules accept O-H⋯O hydrogen bonds from the hy...

Low-barrier or short, strong hydrogen bonds have been proposed to contribute 10 to 20 kilocalories per mole to transition-state stabilization in enzymatic catalysis. The proposal invokes a large increase in hydrogen bond energy when the pKa values of the donor and acceptor (where Ka is the acid constant) become matched in the transition state (delta pKa=0). This hypothesis was tested by investi...

The features of hydrogen bonds in DsrD protein from sulfate-reducing bacteria have been investigated by neutron protein crystallography. The function of DsrD has not yet been elucidated clearly, but its X-ray crystal structure revealed that it comprises a winged-helix motif and shows the highest structural homology to the DNA-binding proteins. Since any neutron structure of a DNA recognition pr...