โ Scribed by T.Gregory Schaaff; James L. Stephenson Jr.; Scott A. McLuckey
No coin nor oath required. For personal study only.
The kinetics of HI attachment to gaseous angiotensin-related ions were determined in a quadrupole ion trap mass spectrometer. The (M ฯฉ H) ฯฉ and (M ฯฉ 2H) 2ฯฉ ions of peptides with sequences of DRVYIHPFHL, NRVYVHPFHL, and RVYIHPFHL and the (M ฯฉ H) ฯฉ ions of DRVYIHPF and NRVYVHPF and their respective methyl esters were studied. For many of the ions studied here, multiple reactive conformations were resolved by their differing reactivities. The kinetics of the attachment of HI to the singly charged ions are consistent with structural models that are generated by molecular mechanics calculations, which suggest a high degree of intraionic interactions between the protonation site and other basic sites in the ion. The incorporation of HI can also disrupt the inherent intraionic interactions in the ions, which is not only reflected in the reaction kinetics, but also consistent with the interactions suggested by the molecular mechanics simulations. These results confirm that HI attachment kinetics can be used as a probe of three dimensional ion structure and provide important new information regarding the utility of this molecular probe. (Int J Mass Spectrom 202 (2000) 299 -313) ยฉ 2000 Elsevier Science B.V.
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## Abstract We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteronโtransfer reaction between the photoacid 8โhydroxyโ1,3,6โpyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond la