Hydrogen Bonds in Biological Molecules

Huggins predicted in 1936 that H bonds should be involved in various biological molecules [13]. In fact, the ubiquitous involvement of H bonds in biological systems such as proteins and DNA is now beyond doubt [20]. Most of the nitrogen and oxygen atoms in proteins engage in H bonding with either protein or solvent atoms 

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G. A. Jeffrey and W. Soenger, Hydrogen Bonding in Biological Molecules, Springer-Verlag, Berlin, 1991. 

Most common hydrogen bonds in biological molecules ... 

Dr. Schneider s paper has given an introduction to the subject of the nuclear resonance study of hydrogen bonding, which will not be repeated here. Our initial aim was to study molecular complexes in aqueous solution, with particular emphasis on complexes of biological importance. It soon became apparent that the phenomena were so complex that a fundamental study of hydroxyl-type hydrogen bonds in simple molecules was first required. 

Statistical analyses of both proteins and small molecules reveal fhat hydrogen bond stereochemistry is influenced by two major factors the electronic configuration of the acceptors and the steric accessibility of the acceptors and donors. Considering the most common hydrogen bond in biological chemistry, there is a distinct preference for N-H - O=C bonds to form in the O=C-RR plane and in the directions of the conventionally viewed sp lone pairs [13], wifh the proton lying within 30 of the plane and at 30-60 ° to the O=C axis in the majority of cases. 

Sulfur is most commonly encountered in biological molecules either in compounds called thiols, which have a sulfur atom bonded to one hydrogen and one carbon, or in sulfides, which have a sulfur atom bonded to two carbons. Produced by some bacteria, methanethiol (CH3SH) is the simplest example of a thiol, and dimethyl sulfide [(ChP S l is the simplest example of a sulfide. Both can be described by approximate sp3 hybridization around sulfur, although both have significant deviation from the 109.5° tetrahedral angle. 

The native, biologically active form of a protein molecule is held together by a delicate balance of noncovalent forces hydrophobic, ionic, van der Waals interactions, and hydrogen bonds. In addition,... 

The relatively recent development27 of the direct methods of crystal structure analysis has produced a great increase in the number of crystal structures reported in the literature, particularly with regard to the possible hydrogen bonds (also for biological molecules). Hence, the classical spectroscopic data on hydrogen bonding in solution are backed up by X-ray diffraction analysis data. 

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