Thermodynamics and Reaction Mechanisms for Decomposition of a Simple Protonated Tripeptide, HGGA: From HGGG to HGAG to HGGA.

We present a thorough characterization of fragmentations observed in threshold collision-induced dissociation (TCID) experiments of protonated glycylglycylalanine (HGGA) with Xe using a guided ion beam tandem mass spectrometer. Kinetic energy dependent cross sections for nine ionic products were obtained and analyzed to provide 0 K barriers for the five primary products, [b], [y + 2H], [b], [y + 2H], and [a]; and four secondary products, [a], [a], high-energy [y + 2H], and CHCHNH, after accounting for multiple ion-molecule collisions, the internal energy of reactant ions, unimolecular decay rates, competition between channels, and sequential dissociations. Relaxed potential energy surface scans performed at the B3LYP-GD3BJ/6-311+G(d,p) level of theory are used to identify transition states (TSs) and intermediates of the five primary and three secondary products (with the mechanism of the other secondary product previously established).

Linkage Memory in Underivatized Protonated Carbohydrates.

Carbohydrates are among the most complex class of biomolecules, and even subtle variations in their structures are attributed to diverse biological functions. Mass spectrometry has been essential for large scale glycomics and glycoproteomics studies, but the gas-phase structures and sometimes anomalous fragmentation properties of carbohydrates present long-standing challenges. Here we investigate the gas-phase properties of a panel of isomeric protonated disaccharides differing in their linkage configurations.

High-Precision, Gas-Phase Hydrogen/Deuterium-Exchange Kinetics by Mass Spectrometry Enabled by Exchange Standards.

Mass spectrometry (MS) has become a primary tool for identifying and quantifying biological molecules. In combination with other orthogonal techniques, such as gas-phase hydrogen/deuterium exchange (gHDX), MS is also capable of probing the structure of ions. However, gHDX kinetics can depend strongly on many factors, including laboratory temperature, instrumental conditions, and instrument platform selection.

Dissection of Fragmentation Pathways in Protonated N-Acetylhexosamines.

Structural characterization of carbohydrates by mass spectrometry necessitates a detailed understanding of their gas phase behavior, particularly for protonated carbohydrates that can undergo complex structural rearrangements during fragmentation. Here we utilize tandem mass spectrometry, isotopic labeling, gas-phase hydrogen/deuterium exchange, and ion mobility measurements to characterize structures of the various product ions of protonated N-acetylhexosamines. Following the facile loss of the reducing end hydroxyl group, we identify two primary fragmentation pathways.

Bridging the structural gap of glycoproteomics with ion mobility spectrometry.

Over the past two decades mass spectrometry (MS) has enabled high throughput studies on the level of a complex proteome. While it has similarly advanced glycobiology, the level of progress has been more restrained. This is in large part due to the diversity and complexity of carbohydrate structures.

Thermodynamics and Reaction Mechanisms of Decomposition of the Simplest Protonated Tripeptide, Triglycine: A Guided Ion Beam and Computational Study.

We present a thorough characterization of fragmentations observed in threshold collision-induced dissociation (TCID) experiments of protonated triglycine (HGGG) with Xe using a guided ion beam tandem mass spectrometer (GIBMS). Kinetic energy-dependent cross-sections for 10 ionic products are observed and analyzed to provide 0 K barriers for six primary products: [b], [y + 2H], [b], CO loss, [y + 2H], and [a]; three secondary products: [a], [a], and [y + 2H - CO]; and two tertiary products: high energy [y + 2H] and [a - CO] after accounting for multiple ion-molecule collisions, internal energy of reactant ions, unimolecular decay rates, competition between channels, and sequential dissociations. Relaxed potential energy surface scans performed at the B3LYP-D3/6-311+G(d,p) level of theory are used to identify transition states (TSs) and intermediates of the six primary and one secondary products.

Kinetic determination of potassium affinities by IRMPD: elucidation of precursor ion structures.

Dissociation kinetics of the K(+) loss reaction of three potassiated tertiary amino acids (Scheme 1) were studied by infrared multiple photon dissociation (IRMPD) in a Fourier transform ion cyclotron resonance (FT ICR)-MS instrument. The aim of the study was to probe if a kinetic study by IRMPD can yield useful information on the ion structure of the precursor ion species. The measured activation energy values determined by IRMPD are related to the potassium affinity, DeltaH(K(+)), of N-methyl proline determined by threshold collision-induced dissociation experiments.