Hydrogen-Bonding Patterns in the Secondary Structure Elements

3 Hydrogen-Bonding Patterns in the Secondary-Structure Elements 

Because main-chain to main-chain hydrogen bonds in the secondary-structure elements, a-helix, /J-pleated sheet and / -turn, are comparable in character and geometry, they are considered together in the following. 

The nonbonding of the )C=0 groups may be overestimated, since some may be involved in long three-center bonds. The presence of unidentified disordered water molecules as donors may also reduce this statistic. 

Total number of C = O groups 1733 Total number of N - H groups 1679 

Only one main-chain N-H 621 (41.1%) Only one main-chain C = O 1012 (76.1%) 

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