The solution structure of a new recombinant RGD-hirudin, which has the activities of anti-thrombin and anti-platelet aggregation, was determined by H-1 nuclear magnetic resonance spectroscopy and compared with the conformations of recombinant wildtype hirudin and hirudin (variant 2, Lys47) of the hirudin thrombin complex. On the basis of total 1284 distance and dihedral angle constraints derived from a series of NMR spectra, 20 conformers were computed with ARIA/CNS programs. The structure of residues 3-30 and 37-48 form a molecular core with two antiparallel beta-sheets as the other two hirudins. However, significant differences were found in the surface electrostatic charge distributions among the three hirudins, especially in the RGD segment of recombinant RGD-hirudin. This difference may be greatly beneficial to its additional function of anti-platelet aggregation. The difference in extended C-terminal makes its both ionic and hydrophobic interactions with the fibrinogen recognition exosite of thrombin more effective. (c) 2007 Elsevier Inc. All rights reserved.