Structural studies of two antiaggregant RGDW peptides by ^lH and ¹³C NMR

The structural features of Arg‐Gly‐Asp‐related sequences have been investigated by ¹H and ¹³C NMR. Two linear peptides which inhibit platelet aggregation with a high efficiency have been studied: D‐Arg‐Gly‐Asp‐Trp and L‐Arg‐Gly‐Asp‐Trp. Analysis of pH titration effects, amide proton exchange rates and inter‐proton distances obtained from ROESY spectra suggest that these small fragments predominantly adopt a type II′β‐turn structure in solution. Folding features of a non‐active cyclic peptide based on the same sequence (cyclo‐[Arg‐Gly‐Asp‐Trp]₂) have also been investigated. The biological relevance of these structures is discussed.