The Ac-RGD-NH2 peptide as a probe of slow conformational exchange of short linear peptides in DMSO.
ABSTRACT According to general belief, the conformational information on short linear peptides in solution derived at ambient temperature from NMR spectrometry represents a population-weighted average over all members of an ensemble of rapidly interconverting conformations. Usually the search for discrete conformations is concentrated at low temperatures especially when sharp NMR resonances are detected at room temperature. Using the peptide Ac-RGD-NH(2) (Ac-Arg-Gly-Asp-NH(2), Ac: acetyl) as a model system and following a new approach, we have been able to demonstrate that short linear peptides can adopt discrete conformational states in DMSO-d(6) (DMSO: dimethylsulfoxide) which vary in a way critically dependent on the reconstitution conditions used before their dissolution in DMSO-d(6). The conformers are stabilized by intramolecular hydrogen bonds, which persist at high temperatures and undergo a very slow exchange with their extended structures in the NMR chemical shift time scale. The reported findings provide clear evidence for the occurrence of solvent-induced conformational exchange and point to DMSO as a valuable medium for folding studies of short linear peptides.
- SourceAvailable from: Athanassios Stavrakoudis[Show abstract] [Hide abstract]
ABSTRACT: The peptide sequence YMESRADRKLAEVGRVYLFL, derived from 313-332 region of the αIIb, has been identified as a potent inhibitor of platelet aggregation and fibrinogen binding to αIIbβ3. More detailed studies have revealed that the Y313MESRADR320 sequence is the shortest octapeptide with strong inhibitory activity. This work provides insight of the solution conformation of these peptides, by performing extensive molecular dynamics simulations of 100ns. The 8mer peptide has no stable conformation in water while the 20mer peptide retains a relative conformational stability. Analysis of side chain orientation of the RAD fragment revealed the synplanar arrangement of guanidinium and β-carboxylic groups providing a framework for explaining the similar biological activity of the two peptides, despite their differences in sequence and conformation.International Journal of Peptide Research and Therapeutics 04/2012; 15(4):263-272. · 1.28 Impact Factor
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ABSTRACT: PEGylations of polypeptides with a four-arm PEG (polyethylene glycol) in a dilute DMSO solution resulted in a successful conjugation with terminal specificity, which supports an intriguing PEGylation mechanism via conformational and kinetic control. © 2010 Crown in the right of Canada. J Appl Polym Sci, 2010Journal of Applied Polymer Science 07/2010; 118(6):3269 - 3273. · 1.40 Impact Factor
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ABSTRACT: Inhibition of platelet aggregation is indispensable for the treatment of acute arterial thrombotic episodes. We have previously reported the synthesis of a highly constrained cyclic peptide, that incorporates the -CDC- sequence, (S,S) PSRCDCR-NH(2), which potently inhibits aggregation and fibrinogen binding to human platelets in vitro. We have tested the safety and efficacy of the peptide on the electrically induced carotid artery thrombosis experimental rabbit model. The peptide's effects on carotid blood flow, thrombus weight, in vitro and ex vivo platelet aggregation, and bleeding and hemostatic parameters were evaluated. The peptide was administered via the femoral vein. Carotid blood flow was continuously monitored for 90 min after electrical thrombus formation. The peptide, at 12 mg/kg, prevented total artery occlusion and significantly preserved carotid artery's patency compared with placebo and eptifibatide. Furthermore, (S,S) PSRCDCR-NH(2) administration at 12 mg/kg reduced thrombus weight, whereas it inhibited ex vivo ADP, arachidonic acid (AA) and collagen-induced platelet aggregation. Moreover (S,S) PSRCDCR-NH(2) at 12 mg/kg presented significantly higher inhibitory effects on AA and collagen-induced ex vivo platelet aggregation compared to eptifibatide. The peptide at any dose did not affect the coagulation cascade, the bleeding times or the hemostatic response of the animals. Thus highly constrained cyclic peptides like (S,S) PSRCDCR-NH(2) that incorporate the -CDC- motif and fulfil certain conformational criteria represent novel compounds that potently inhibit thrombus formation, ex vivo platelet aggregation and carotid artery occlusion superiorly to other non-RGD peptides, such as YMESRADR, without causing hemorrhagic complications in a rabbit model of arterial thrombosis.Platelets 12/2010; 22(5):361-70. · 2.24 Impact Factor