Hydrogen-bond-directing groups

A from zinc ion in the native enzyme). This hydroxyl group hydrogen-bonds directly to the donor atom in the anion complexes. The sulfonamide complexes... 

Finally, since besides the inductive effect of the sulfoxide and the sulfone functional groups, hydrogen bonding, field effects and steric effects to solvation may or may not work in the same direction, the pKx values can be useful in assigning configurations of suitable pairs of stereoisomeric sulfoxide and sulfone carboxylic acids291. 

Fig. 8. Structure of succinamide. The NHa group form two hydrogen bonds directed at the 0 =C group linking the molecules in a two-dimensional sheet...

The most decisive support for this contention has proceeded from the X-ray study of crystalline sperm whale myoglobin, which, as Kendrew has demonstrated (Kendrew et al., 1960, 1961), contains 118 of its 153 residues, that is, 77 %, in right-handed a-helices. The side chains of L-amino acids in a right-handed helix project in a direction opposite to that of carbonyl groups hydrogen-bonded into the helix, an orientation that is in fact... 

P sheet A mode of protein folding in which two polypeptide chains (/ strands) lie side by side and either parallel or antiparallel with respect to the direction of the NH-Cq-CO group. Hydrogen bonds are formed from a carbonyl group of one chain to an amide nitrogen atom of the other chain and vice versa. 

Hydroxy groups exert a directive effect on epoxidation and favor approach from the side of the double bond closest to the hydroxy group. Hydrogen bonding between the hydroxy group and the peroxidic reagent evidently stabilize the TS. 

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