Abstract: A method for the selective fragmentation of peptides using free radical initiator-peptide conjugates is provided. Free radical initiated peptide sequencing, or FRIPS, consists of covalently attaching a free radical initiator to a peptide and collisionally activating this conjugate. This results in fragment formation. Subsequent collision-activated dissociation further dissociates the fragments, producing a group of ions based on the interaction of the free radical initiator and the target molecule. The methodology is applied to the fundamental study of biologically relevant reactions of free radicals with peptides and proteins in the gas phase, as well as to a completely gas-phase approach to protein sequencing.

Abstract: A new optical sensing method for detection of analyte vapors down to ppb levels is described. The sensor is based on the use of a visible indicator, such as Bromocresol green, adsorbed onto a high surface area substrate, such as a silica sphere matrix. When the analyte gas is adsorb onto the matrix, the indicator undergoes a color change. The color change in turn is detected with a suitable spectrometer. Sensor performance is demonstrated for an exemplary amine sensor for the aliphatic amines tert-butylamine, diethylamine and triethylamine and also for pyridine and aniline. The microsphere sensor is more sensitive than other prior art optical amine sensor designs. The sensor response varies with temperature, with lower sensitivity and faster response at higher temperatures allowing for adjustment to prioritize sensitivity or speed. The sensor response is also highly reproducible and fully reversible.

Abstract: A method and apparatus for probing the chemistry of a single droplet are provided. The technique uses a variation of the field-induced droplet ionization (FIDI) method, in which isolated droplets undergo heterogeneous reactions between solution phase analytes and gas-phase species. Following a specified reaction time, the application of a high electric field induces FIDI in the droplet, generating fine jets of highly charged progeny droplets that can then be characterized. Sampling over a range of delay times following exposure of the droplet to gas phase reactants, the spectra yield the temporal variation of reactant and product concentrations. Following the initial mass spectrometry studies, we developed an experiment to explore the parameter space associated with FIDI in an attempt to better understand and control the technique.

Abstract: Biomimetic reagents capable of selectively forming non-covalent complexes and initiating intermolecular reactions with peptides in the gas phase are described. The reagents are particularly useful in gas phase peptides chemistry.