Short, Strong Hydrogen Bonds in the Gas Phase and in Solution:  Theoretical Exploration of pKaMatching and Environmental Effects on the Strengths of Hydrogen Bonds and Their Potential Roles in Enzymatic Catalysis

1998 ◽  
Vol 63 (14) ◽  
pp. 4611-4619 ◽  
Author(s):  
Jiangang Chen ◽  
Michael A. McAllister ◽  
Jeehiun K. Lee ◽  
K. N. Houk
Keyword(s):  
Hydrogen Bonds ◽  
Gas Phase ◽  
Environmental Effects ◽  
Enzymatic Catalysis

Gas-Phase Clustering of NO+ with H2S and H2O

2007 ◽  
Vol 72 (8) ◽  
pp. 1122-1138 ◽  
Author(s):  
Milan Uhlár ◽  
Ivan Černušák
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Saddle Points ◽  
Solvent Molecule ◽  
Local Minima ◽  
Additional Water ◽  
Three Body ◽  
Rain Formation ◽  
Stable Structures

The complex NO+·H2S, which is assumed to be an intermediate in acid rain formation, exhibits thermodynamic stability of ∆Hº300 = -76 kJ mol-1, or ∆Gº300 = -47 kJ mol-1. Its further transformation via H-transfer is associated with rather high barriers. One of the conceivable routes to lower the energy of the transition state is the action of additional solvent molecule(s) that can mediate proton transfer. We have studied several NO+·H2S structures with one or two additional water molecule(s) and have found stable structures (local minima), intermediates and saddle points for the three-body NO+·H2S·H2O and four-body NO+·H2S·(H2O)2 clusters. The hydrogen bonds network in the four-body cluster plays a crucial role in its conversion to thionitrous acid.

scholarly journals Crystal structure, computational study and Hirshfeld surface analysis of ethyl (2S,3R)-3-(3-amino-1H-1,2,4-triazol-1-yl)-2-hydroxy-3-phenylpropanoate

2019 ◽  
Vol 75 (12) ◽  
pp. 1919-1924
Author(s):  
Abdelkader Ben Ali ◽  
Youness El Bakri ◽  
Chin-Hung Lai ◽  
Jihad Sebhaoui ◽  
Lhoussaine El Ghayati ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Gas Phase ◽  
Surface Analysis ◽  
Computational Study ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Dft Methods ◽  
Important Interaction ◽  
The Mean ◽  
Title Molecule

In the title molecule, C13H16N4O3, the mean planes of the phenyl and triazole rings are nearly perpendicular to one another as a result of the intramolecular C—H...O and C—H...π(ring) interactions. In the crystal, layers parallel to (101) are generated by O—H...N, N—H...O and N—H...N hydrogen bonds. The layers are connected by inversion-related pairs of C—H...O hydrogen bonds. The experimental molecular structure is close to the gas-phase geometry-optimized structure calculated by DFT methods. Hirshfeld surface analysis indicates that the most important interaction involving hydrogen in the title compound is the H...H contact. The contribution of the H...O, H...N, and H...H contacts are 13.6, 16.1, and 54.6%, respectively.

Das sterische Verhalten der Alpha-Helix / The steric Behaviour of the Alpha-Helix

1969 ◽  
Vol 24 (6) ◽  
pp. 672-690 ◽  
Author(s):  
R. Jarosch
Keyword(s):  
Hydrogen Bonds ◽  
Polypeptide Chain ◽  
Enzymatic Catalysis ◽  
Alpha Helix ◽  
Side Chains ◽  
Tertiary Structures ◽  
General Variation ◽  
Coiling Direction ◽  
Α Helix ◽  
Molecule Model

The steric behaviour of the α-Helix has been investigated using an elastic molecule-model made of solid rubber balls and steel pins. Shortening of the hydrogen-bonds, which is possible at least in the range from 2.91 to 2.67 A in real α-Helices, has the following effects:1. The α-Helix contracts proportionally to the length of the hydrogen-bonds (figs. 3, 4).2. A torsional force arises leading in the case of longer α-Helices to torsional revolutions of the free ends of the helix (figs. 3 a. 4 a).3. Tertiary structures (superhelices. flattened superhelices. planar wavy lines, planar arcs) superpose the α-Helix if only specific hydrogen-bonds (e. g. indicated by arrows in fig. 5) will be shortened and if the distance between them is repeated in the sequence of the polypeptide chain (Tab. I). Some of the sequence-distances show similar tertiary structures and the same pitches of the superhelices (Tab. II). A general variation in the length of the hydrogen-bonds causes alterations in the superstructure and can also change the coiling direction of the superhelix.4. The Cα— Cβ; bonds incline slightly to the axis of the helix (fig. 11) through which the α-Helix with side chains becomes a little thinner. Because of the torsion (see item 2) the distance between the side chains changes also (fig. 12). The distances increase between specific positions of the side chains and decrease between others (Tab. III).Possible reasons for the shortening of the hydrogen-bonds are briefly discussed. The importance of the described behaviour for biological movements, enzymatic catalysis (“allosteric effect”) and active transport is emphasized.

High resolution electronic spectroscopy of 9-fluorenemethanol in the gas phase: New insights into the properties of Π-hydrogen bonds

2010 ◽  
Vol 133 (12) ◽  
pp. 124312 ◽  
Author(s):  
Diane M. Miller ◽  
Justin W. Young ◽  
Philip J. Morgan ◽  
David W. Pratt
Keyword(s):  
High Resolution ◽  
Hydrogen Bonds ◽  
Gas Phase ◽  
Electronic Spectroscopy
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