Stereospecific collision-induced dissociation and vibrational spectroscopy of protonated cyclo (Tyr-Pro)

How change in chirality prevents β-amyloid type interaction in a protonated cyclic dipeptide dimer

“…Indeed, the strong sensitivity to chirality observed here strongly contrasts with what is observed for the cyclo (Tyr-Pro) protonated dimer, the structure of which is identical for identical or opposite absolute configurations of the residues. 46 These results support the peculiar role of histidine in the structure and fragmentation of peptides. 51,87 The differences between (c-LL) 2 H + and (c-LD) 2 H + are very marked, and do not involve weak ancillary interactions as seen in other systems but the presence or not of an antiparallel b-sheet.…”

“…The details of the experiments can be found in previous publications. 45,46,[59][60][61] Briefly, the ions were mass-selected in a quadrupole mass filter, thermalized in the hexapole linear trap by colliding with argon, and transferred to the FT-ICR cell.…”

“…As a result, protonation of cyclic dipeptides usually happens on the amide CO, which results in the limited effect of chirality on their collision-induced dissociation (CID) efficiency. [45][46][47] Histidine-containing peptides stand out by the basic nature of the His residue, which is protonated on the imidazole ring. 48 This peculiar protonation site makes histidine very sensitive to solvation.…”

Determination of kinetic properties in unimolecular dissociation of complex systems from graph theory based analysis of an ensemble of reactive trajectories

“…More detailed description of the reactivity will be left to specific studies as done previously for other systems. 65,66 Experimentally this is obtained by counting the number of structures as a function of their mass-tocharge (m/z) ratio. Theoretically we can obtain it in the same way using the rigorous definition of a primary fragmentation product given before.…”

Do Stereochemical Effects Overcome a Charge-Induced Perturbation in Isolated Protonated Cyclo(Tyr-Tyr)?

“…Protonated cyclic dipeptides have been the subject of several studies as possible intermediates in the fragmentation of peptides. − A comparison between collision-induced dissociation (CID) experiments and chemical dynamics simulations showed that the fragmentation processes of the amide CO protonated systems do not depend much on chirality, in contrast to those that are protonated on the side chain of a basic residue. − Protonation modifies the balance between the different conformers of biomolecules . For cyclic dipeptides based on Tyr, Phe, or Pro residues, the proton is located on the amide CO and does not influence its conformation much.…”