Real-Time Sensing with Multiplexed Optomechanical Resonators.

Nanoelectromechanical resonators have been successfully used for a variety of sensing applications. Their extreme resolution comes from their small size, which strongly limits their capture area. This leads to a long analysis time and the requirement for large sample quantity.

Water Loss from Protonated XxxSer and XxxThr Dipeptides Gives Oxazoline-Not Oxazolone-Product Ions.

Neutral loss of water and ammonia are often significant fragmentation channels upon collisional activation of protonated peptides. Here, we deploy infrared ion spectroscopy to investigate the dehydration reactions of protonated AlaSer, AlaThr, GlySer, GlyThr, PheSer, PheThr, ProSer, ProThr, AsnSer, and AsnThr, focusing on the question of the structure of the resulting [M + H - HO] fragment ion and the site from which HO is expelled. In all cases, the second residue of the selected peptides contains a hydroxyl moiety, so that HO loss can potentially occur from this side-chain, as an alternative to loss from the C-terminal free acid of the dipeptide.