Energetics of an n --> pi interaction that impacts protein structure.
[structure: see text] The trans/cis ratio of the amide bond in N-formylproline phenylesters correlates with electron withdrawal by a para substituent. The slope of the Hammett plot (rho = 0.26) is indicative of a substantial effect. This effect arises from a favorable n --> pi interaction between the amide oxygen and ester carbonyl. In a polypeptide chain, an analogous interaction can stabilize the conformation of trans peptide bonds, alpha-helices, and polyproline type-II helices.
Hodges
Jonathan A
JA
Departments of Chemistry and Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Raines
Ronald T
RT
D008956:Models, Chemical; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
D011506:Proteins