Hydrogen bond An attractive interaction

Perhaps the most important noncovalent interaction in biological molecules is tbe hydrogen bond, an attractive interaction between a hydrogen bonded to an electronegative O or N atom and an unshared electron pair on another O or N atom. In essence, a hydrogen bond is a very strong dipole-dipole interaction... 

A variety of noncovalent interactions have a significant effect on the properties of large biomolecules. Hydrogen-bonding—the attractive interaction between a positively polarized hydrogen atom bonded to an O or N atom with an unshared electron pair on another O or N atom, is particularly important in giving proteins and nucleic acids their shapes. 

The hydrogen bond is an attractive interaction between a group X-H and an atom or a group of atoms, in the same or different molecule(s), when there is evidence of bond formation. ... 

A hydrogen bond is an attractive interaction between a hydrogen atom bonded to a very electronegative atom (O, N, or F) and an unshared electron pair on another electronegative atom. For example, hydrogen bonds occur in both water and ammonia ... 

There is an attractive interaction between small polar groups and the silica gel, particularly if they are hydrogen bond donors not internally bonded to the amide group. Formally, such groups are assigned to the S (small) class. 

Hydrogen bonds can be considered to represent a special type of electrostatic interaction. The term hydrogen bond was coined in 1920 to help describe the internal structure of water. However, since that time the precise meaning of the term has been subject to change so that it is difficult to define it in a manner that will satisfy all. A simple working description is that it is an attractive interaction between a proton donor and a proton acceptor. In this vein, Pimentel and McClellan" in their classic text define a hydrogen bond as follows ... 

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