Abstract

Two cyclic disulfide-bridged tetrapeptides [cyclo(Boc-Cys-Pro-Aib-Cys-OMe) (1) and cyclo(Boc-Cys-Pro-Phe-Cys-OMe) (2)] have been monitored by time-resolved mid-IR spectroscopy in the C=O vibrational range. A conformational change is induced by cleavage of the intramolecular disulfide bridge upon UV excitation (lambda(exc) = 260 nm), giving rise to a pair of cysteinyl radicals (thiyl radicals), which diffuse apart allowing the peptide to change conformation before they undergo quenching. The amide I band reports on the dynamics of the peptide backbone, which evolves on a 100 ps time scale and then stays constant up to 10 micros at low enough concentrations ( approximately 100 mM). To probe specifically the lifetime of the free cysteinyl radicals, time-resolved UV laser flash photolysis has been applied. The concentration of the cysteinyl radical decays nonexponentially, but about 50% are still present after 1 ms. The photocleavable disulfide bridge hence may serve as an intrinsic, naturally occurring phototrigger to study peptide dynamics that opens a wide time-window from a few picoseconds to many hundreds of microseconds.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.