Glycine residues can adopt many different conformations

Glycine residues can adopt many different conformations 

Observed values for all residue types except glycine. Each point represents (j) and values for an amino acid residue in a well-refined x-ray structure to high resolution, (c) Observed values for glycine. Notice that the values include combinations of (j) and that are not allowed for other amino acids. (From J. Richardson, Adv. Prot. Chem. 34 174-175, 1981.1 

Certain side-chain conformations are energetically favorable 

The three staggered conformations are different for valine because the three groups attached to Cp are different. The first staggered conformation (b) is less crowded and energetically most favored because the two methyl groups bound to Cp are both close to the small H atom bound to Ca- 

Many proteins contain intrinsic metal atoms 

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