A Comparison of Energy-Resolved Vibrational Activation/Dissociation Characteristics of Protonated and Sodiated High Mannose N-Glycopeptides

Fragmentation of glycopeptides in tandem mass spectrometry (MS/MS) plays a pivotal role in site-specific protein glycosylation profiling by allowing specific oligosaccharide compositions and connectivities to be associated with specific loci on the corresponding protein. Although MS/MS analysis of glycopeptides has been successfully performed using a number of distinction dissociation methods, relatively little is known regarding the fragmentation characteristics of glycopeptide ions with various charge carriers. In this study, energy-resolved vibrational activation/ dissociation was examined via collision-induced dissociation for a group of related high mannose tryptic glycopeptides as their doubly protonated, doubly sodiated, and hybrid protonated sodium adduct ions. The doubly protonated glycopeptide ions with various compositions were found to undergo fragmentation over a relatively low but wide range of collision energies compared with the doubly sodiated and hybrid charged ions, and were found to yield both glycan and peptide fragmentation depending on the applied collision energy. By contrast, the various doubly sodiated glycopeptides were found to dissociate over a significantly higher but narrow range of collision energies, and exhibited only glycan cleavages. Interestingly, the hybrid protonated sodium adduct ions were consistently the most stable of the precursor ions studied, and provided fragmentation information spanning both the glycan and the peptide moieties. Taken together, these findings illustrate the influence of charge carrier over the energyresolved vibrational activation/dissociation characteristics of glycopeptides, and serve to suggest potential strategies that exploit the analytically useful features uniquely afforded by specific charge carriers or combinations thereof

Extending the Capabilities of Tandem Mass Spectrometry for Glycoanalysis: Studies of the Parameters That Dictate the Collision-Induced Dissociation and Surface-Induced Dissociation of Glycopeptides and Oligosaccharides

Tandem mass spectrometry (MS/MS) is among one of the most powerful tools in glycoconjugate and carbohydrate analysis. With a need for further structural characterization of such analytes, there is a rising demand for enhancing the information content of MS/MS spectra. Therefore, in recent years, there have been many efforts to increase glycoprotein sequence coverages and in turn provide more structural and bioanalytical insights toward the functions and bioactivities of glycoproteins. A variety of ion activation and dissociation techniques have been implemented to achieve this goal, though some are subjected to limitations arising from the fragmentation pathways available in the ion activation process. A comprehensive understanding of the key parameters that govern fragmentation channels can allow for prediction of the product ions formed in gas-phase activation routes. This dissertation centers on the development of experimental designs that allow for the investigation into fundamentals of glycopeptide dissociation and major factors that influence the dissociation mechanisms. Chapter I is an overview on MS/MS strategies that are utilized to obtain vast information on peptide composition, attached glycan structure, and the glycosylation site of a glycoprotein. Chapter II describes a study on the effect of glycopeptide charge carrier on vibrational activation / dissociation characteristics of N-linked high mannose glycopeptides. Chapter III illustrates the impact of glycan size on the fragmentation pattern of high mannose N-linked glycopeptides via low energy collision-induced dissociation (CID). Chapter IV discusses the incorporation of surface-induced dissociation (SID) inside Synapt G2-S HDMS quadrupole time-of-flight (Q-TOF) instrument. The resulting comparison of the energy deposition processes in multi-collision (CID) and single event (SID) activation confirms the involvement of diverse energy deposition channels in each method. Chapter V describes the use of energy-sudden activation dissociation to circumvent the limitations of CID in carbohydrate sequencing. Overall, this dissertation works to address some of the ambiguity in glycopeptide and carbohydrate fragmentation processes

Modification of Multiwalled Carbon Nanotubes by Dipyridile Amine for Potentiometric Determination of Lead(II) Ions in Environmental Samples

A carbon paste electrode was modified by dipyridile amine functionalized multiwalled carbon nanotubes for determination of trace amounts of lead(II) ions. The electrode composition was graphite powder 70%, paraffin 23%, and dipyridile amine modified MWCNTs 7% (W/W). The linear range for lead(II) was 9.5 × 10−8 to 2.5 × 10−3 mol L−1, and the limit of detection was obtained 7.0 × 10−8 mol L−1. The lifetime of the electrode was ten weeks, and a fast response time was observed. The electrode was used for determination of trace amounts of Pb(II) ions in real samples and standard reference materials of water, soil, and plant

Flame Atomic Absorption Determination of Gold Ion in Aqueous Samples after Preconcentration Using 9-Acridinylamine Functionalized γ-Alumina Nanoparticles

A simple and sensitive solid phase extraction utilizing 9-acridinylamine functionalized alumina nanoparticles was developed, and their potential use for preconcentration and subsequent determination of gold by flame atomic absorption spectrometry (FAAS) was investigated. A number of parameters, namely, type, concentration, and volume of eluent, pH of the sample solution, flow rate of extraction, and volume of the sample, were evaluated. The effect of a variety of ions on preconcentration and recovery was also investigated. Gold ions were found to be recovered quantitatively at pH 3.0, with 0.1 mol L−1 thiourea in 2 mol L−1 H2SO4 as eluent. The limit of detection (LOD), defined as five times the standard deviation of the blank, was determined to be lower than 13.0 ppb. Under optimum conditions, the accuracy and precision (RSD%) of the method were >98.0 and <1.5%, respectively. To gauge its ability in terms of application to real samples, the proposed method was successfully applied for determination of gold concentration in waste water samples and one soil standard material, and satisfactory results were obtained