The utility of ultraviolet photodissociation (UVPD) in comparison to higher-energy collisional dissociation (HCD) to provide sequence coverage was assessed for various protein cation charge states and sizes. UVPD provided consistently higher sequence coverages through more uniform fragment ion distribution along the protein sequence. HCD provided lower sequence coverage values as well as more preference towards cleavage at the most labile bonds. Assessment of coverage dependence at lower charge states was also performed through proton transfer reactions (PTR) with ion parking. Overall, HCD provided preferential cleavage C-terminal to amino acids with acidic sidechains and N-terminal to proline, while UVPD provided more evenly distributed cleavage sites with enhancement near proline and phenylalanine. Using UVPD as a structural analysis tool, PTR was assessed for perturbations to native-like structure of various protein complexes. Through comparison of UVPD fragment intensities, spectra of protein complexes generated through PTR showed little difference to spectra obtained from native-like protein spectra. Following this, PTR-UVPD was applied to elucidate fragment origins of an ambiguous homodimeric protein complex, otherwise displaying complex a complex mass spectrum of overlapping species. A novel approach to performing UVPD using light emitting diodes (LEDs) was explored involving the engineering of a new planar ion trap. Commercially available ultraviolet LEDs emitting photons with wavelengths ranging from 255 to 275 nm were obtained and interfaced with the new ion trap. Sequestration of sample ions in a small spot allowed optimization of overlap with LED photons and resulting fragmentation efficiencies were assessed. Once optimized, LED-UVPD was successfully performed for electron photodetachment (EPD) of single stand DNA and tyrosine sidechain cleavage of a peptide. Custom instrument function was enabled to automatically resonantly eject un-dissociated precursor ions following UVPD and was applied during liquid chromatography (LC) bottom-up proteomics experiments. Through ejection of uninformative, un-dissociated precursor ions, detrimental mass shifting effects caused by increasing the number of charges during spectrum acquisition were relieved. It was observed that performing PE-UVPD resulted in higher protein identification confidence values than for UVPD alone for an E. coli whole cell lysate digest.

The utility of 193 nm ultraviolet photodissociation (UVPD) and negative electron transfer dissociation (NETD) for the characterization of peptide anions was systematically evaluated. UVPD outperformed NETD in nearly all metrics; however, both methods provided complementary information to traditional collision induced dissociation (CID) of peptide cations in high throughput analyses. In order to enhance the performance of NETD, activated ion negative electron transfer dissociation (AI-NETD) methods were developed and characterized. The use of low-level infrared photoactivation or collisional activation during the NETD reaction period significantly improved peptide anion sequencing capabilities compared to NETD alone. Tyrosine deprotonation was shown to yield preferential electron detachment upon NETD or UVPD, resulting in N - C[alpha] bond cleavage N-terminal to the tyrosine residue. LC-MS/MS analysis of a tryptic digest of BSA demonstrated that these cleavages were regularly observed under high pH conditions. Transmission mode desorption electrospray ionization (TM-DESI) was coupled with 193 nm UVPD and CID for the rapid analysis and identification of protein digests. Comparative results are presented for TM-DESI-MS/CID and TM-DESI-MS/UVPD analyses of five proteolyzed model proteins. In some cases TM-DESI/UVPD outperformed TM-DESI-MS/CID due to the production of an extensive array of sequence ions and the ability to detect low m/z product ions. 193 nm UVPD was implemented in an Orbitrap mass spectrometer for characterization of intact proteins. Near-complete fragmentation of proteins up to 29 kDa was achieved. The high-energy activation afforded by UVPD exhibited far less precursor ion charge state dependence than conventional methods, and the viability of 193 nm UVPD for high throughput top-down proteomics analyses was demonstrated for the less 30 kDa protein from a fractionated yeast cell lysate. The use of helium instead of nitrogen as the C-trap and HCD cell bath gas and trapping ions in the HCD cell prior to high resolution mass analysis significantly reduced the signal decay rate for large protein ions. As a result, monoclonal IgG1 antibody was isotopically resolved and mass accurately determined. A new high mass record for which accurate mass and isotopic resolution has been achieved (148,706.3391 Da ± 3.1 ppm) was established.

Photon-based tandem mass spectrometry provides a versatile ion activation strategy for the analysis of polypeptides, proteins, and lipids. 351-nm ultraviolet photodissociation mass spectrometry (UVPD-MS) is a facile and selective tandem dissociation technique used to elucidate chromophore-modified peptides within large mixtures. A bis-aryl chromogenic chemical probe was utilized to target solvent exposed primary amine residues within native protein states. Collision-induced dissociation (CID) was employed to indiscriminatly characterize the complete proteolytic digest while chromophore containing peptides were selectively dissociated with 351-nm UVPD; thus streamlining the identification of targeted peptides with structurally informative residues. Protein amine residue reactivities were then compared with predicted solvent exposures to elucidate protein tertiary structures, their mechanistic properties, and ligand-binding interactions. High-energy 193-nm UVPD is a fast, high-energy tandem mass spectrometry method and frequently generates fragment ions typically inaccessible to CID-based methods. Native mass spectrometry was coupled to top-down 193-nm UVPD for the gas phase characterization of non-covalent protein-ligand and protein-protein complexes. This method yielded a unique array of fragment ions for a comprehensive analysis of protein structures. UVPD of non-covalent complexes generated many polypeptide backbone fragments to characterize the primary sequence of proteins. Furthermore, top-down UVPD engendered cleavages with intact electrostatic interactions; this provided insight into the binding interfaces within protein-ligand complexes and the higher order structural architectures of oligomeric complexes. High-resolution 193-nm UVPD was paired with high performance liquid chromatography (LC) for the streamlined structural analysis of amphiphilic glycolipids within complex mixtures. For all glycolipids, UVPD provided the most comprehensive structural analysis tool by affording a diverse array of fragment ions to characterize both hydrophobic and hydrophilic moieties. UVPD based LC-MS separations of gangliosides shed light on the ceramide lipid bases, glycan moieties, and their isobaric structural variants. UVPD activation of lipid A and lipooligosaccharides (LOS) compounds generated a mixture of C-C, C-O, and C-N fragment ions to illustrate the hydrophobic acyl structures, while cleavages within the glycosidic, and cross-ring cleavages allowed the determination of acylation patterns. Novel LC-MS separation strategies were developed to elucidate and structurally characterize complex mixtures of lipopolysaccharide containing compounds.

The book that highlights mass spectrometry and its application in characterizing proteins and peptides in drug discovery An instrumental analytical method for quantifying the mass and characterization of various samples from small molecules to large proteins, mass spectrometry (MS) has become one of the most widely used techniques for studying proteins and peptides over the last decade. Bringing together the work of experts in academia and industry, Protein and Peptide Mass Spectrometry in Drug Discovery highlights current analytical approaches, industry practices, and modern strategies for the characterization of both peptides and proteins in drug discovery. Illustrating the critical role MS technology plays in characterizing target proteins and protein products, the methods used, ion mobility, and the use of microwave radiation to speed proteolysis, the book also covers important emerging applications for neuroproteomics and antigenic peptides. Placing an emphasis on the pharmaceutical industry, the book stresses practice and applications, presenting real-world examples covering the most recent advances in mass spectrometry, and providing an invaluable resource for pharmaceutical scientists in industry and academia, analytical and bioanalytical chemists, and researchers in protein science and proteomics.

This is an in-depth guide to the theory and practice of analyzing raw mass spectrometry (MS) data in proteomics. The volume outlines available bioinformatics programs, algorithms, and databases available for MS data analysis. General guidelines for data analysis using search engines such as Mascot, Xtandem, and VEMS are provided, with specific attention to identifying poor quality data and optimizing search parameters.

PROVIDES STRATEGIES AND CONCEPTS FOR UNDERSTANDING CHEMICAL PROTEOMICS, AND ANALYZING PROTEIN FUNCTIONS, MODIFICATIONS, AND INTERACTIONS—EMPHASIZING MASS SPECTROMETRY THROUGHOUT Covering mass spectrometry for chemical proteomics, this book helps readers understand analytical strategies behind protein functions, their modifications and interactions, and applications in drug discovery. It provides a basic overview and presents concepts in chemical proteomics through three angles: Strategies, Technical Advances, and Applications. Chapters cover those many technical advances and applications in drug discovery, from target identification to validation and potential treatments. The first section of Mass Spectrometry-Based Chemical Proteomics starts by reviewing basic methods and recent advances in mass spectrometry for proteomics, including shotgun proteomics, quantitative proteomics, and data analyses. The next section covers a variety of techniques and strategies coupling chemical probes to MS-based proteomics to provide functional insights into the proteome. In the last section, it focuses on using chemical strategies to study protein post-translational modifications and high-order structures. Summarizes chemical proteomics, up-to-date concepts, analysis, and target validation Covers fundamentals and strategies, including the profiling of enzyme activities and protein-drug interactions Explains technical advances in the field and describes on shotgun proteomics, quantitative proteomics, and corresponding methods of software and database usage for proteomics Includes a wide variety of applications in drug discovery, from kinase inhibitors and intracellular drug targets to the chemoproteomics analysis of natural products Addresses an important tool in small molecule drug discovery, appealing to both academia and the pharmaceutical industry Mass Spectrometry-Based Chemical Proteomics is an excellent source of information for readers in both academia and industry in a variety of fields, including pharmaceutical sciences, drug discovery, molecular biology, bioinformatics, and analytical sciences.

Proteomics is the study of the subsets of proteins present in different parts of an organism and how they change with time and varying conditions. Mass spectrometry is the leading technology used in proteomics, and the field relies heavily on bioinformatics to process and analyze the acquired data. Since recent years have seen tremendous developments in instrumentation and proteomics-related bioinformatics, there is clearly a need for a solid introduction to the crossroads where proteomics and bioinformatics meet. Computational Methods for Mass Spectrometry Proteomics describes the different instruments and methodologies used in proteomics in a unified manner. The authors put an emphasis on the computational methods for the different phases of a proteomics analysis, but the underlying principles in protein chemistry and instrument technology are also described. The book is illustrated by a number of figures and examples, and contains exercises for the reader. Written in an accessible yet rigorous style, it is a valuable reference for both informaticians and biologists. Computational Methods for Mass Spectrometry Proteomics is suited for advanced undergraduate and graduate students of bioinformatics and molecular biology with an interest in proteomics. It also provides a good introduction and reference source for researchers new to proteomics, and for people who come into more peripheral contact with the field.