Beta-Sheet are formed by at least two extended segments aligned in a parallel (fi=-139 and psi=135) or antiparallel (fi=-119 and psi=-113) arrangement so that the amide groups of one segment from hydrogen bonds with the amide groups of the other segment. Characteristic NMR restraints are:

Sequential NOEs are similar to those of random coils. Strong d_aN(i,i+1), very meak or absent d_NN(i,i+1), and d_bN(i,i+1) are usually weaker than in alpha-helices.

There is no d(i,i+2), d(i,i+3), and d(i,i+4) NOEs.

Very characteristic interstrand d(i,j) interactions. Medium-to-strong d_aa(i,j) NOEs in antiparallel beta-sheets.

String of consecutive large ³J_HN-HA coupling constants (> 8 Hz).

Amide protons (except at the edges) participate in hydrogen bonds, which results in decreased H/D exchange.

Downfield conformational chemical shift effect of HA (average de +0.38 ppm) and NH (average de +0.29 ppm) protons and upfield effect for CA carbons (average of /1.4 ppm).

¹J_CA-HA of 140.5+-1.8 Hz

Articles of interest: ( 01JACS12318).