Figure 2

Geometry of Gly-Cα···O=C interactions after Gly α-hydrogen atoms are placed in their stereochemically predicted positions for: ( a ) the c RGD-αVβ3 crystal structure, and ( b ) the EFB-αIIbβ3 crystal structure. Atoms are colour coded as follows: oxygen, red; nitrogen, blue; hydrogen, white; metal, purple; carbon from integrin in grey; and carbon from the c RGD and EFB peptides in orange. Cα-H···O hydrogen bonds are shown as green dashed lines. ( c ) Hydrogen bonding in the collagen triple helix [15]. Conventional hydrogen bonds are shown in yellow, Cα-H···O hydrogen bonds in green. The two Hα atoms in collagen Gly residues participate in a bifurcated and three-centred hydrogen bonding configuration. Naming of Gly-Hα atoms follows the convention that Hα1 is equivalent to Hα in L-amino acids.