China
Africa
Explore chapters and articles related to this topic
Biophysical and Biochemical Characterization of Peptide, Protein, and Bioconjugate Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Tapan K. Das, James A. Carroll
Tandem mass spectrometry (MS/MS), in which an ion formed in the ionization source is subjected to fragmentation, followed by mass measurement of the resulting fragment ions, is a powerful tool for determining the precise sites of modifications, down to the specific amino acid residue. MS/MS can be accomplished using several different modes of fragmentation. Most commonly used is CAD (also known as “collision-induced dissociation”, or CID), in which the precursor ion is accelerated in a collision cell in the mass spectrometer which is filled with a gas, such as argon, to impart internal energy into the ion, leading to fragmentation. For peptides, fragmentation tends to occur along the peptide backbone at the amide bonds. This leads to fragment ion spectra which differ in mass by the residue mass of the amino acids present in the peptide. In this way, the sequence of the peptide and the sites of modifications to the peptide can be determined. Fragmentation of the peptide can also be generated using other means, including electron transfer dissociation in ion trap or Orbitrap instruments, or electron capture dissociation or multiphoton dissociation in ion cyclotron resonance instruments. These alternate modes of fragmentation may provide complementary information to CAD, such that in combination increased structural information may be obtained.
Determinative Techniques to Measure Organics and Inorganics
Published in Paul R. Loconto, Trace Environmental Quantitative Analysis, 2020
Tandem MS techniques enhance analyte selectivity as well as analyte sensitivity. A fragment ion from the first m/z analyzer can undergo collision-induced dissociation (CID) with an inert gas such as He or Ar to yield product ions. The collision cell is often a quadrupole analyzer operated in the RF-only mode, thereby trapping (in a radial sense) the residual parent ions and all of the daughters in an appropriate concentration of collision gas. (p. 111)73 The second m/z analyzer or third quadrupole provides a means of analyzing all of the products of CID. An illustration of the principles of tandem A block diagram of a tandem-in-space MS is shown in Figure 4.75.
Mass Spectrometry Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Yuan Su, Li-Rong Yu, Thomas P. Conrads, Timothy D. Veenstra
In the 1970s, Cooks et al. proposed the concept of tandem mass spectrometry and established the early generation of instrumentation for analysis of complex mixture by in-vacuum gas collisions (Beynon et al., 1973; Kondrat and Cooks, 1978). Tandem mass spectrometry is a method involving multiple stages of ion selections and fragmentations or chemical reactions occurring between stages (McLafferty, 1981). Typically, direct measurement of the m/z values of ions produced from the ion source is called a full scan (MS1). Unlike the full scan, tandem mass spectrometry involves the selection and isolation of ions in a mass analyzer as the first MS analysis stage, the fragmentation or gas reaction between the two MS analysis stages, and the generation of MS2 spectra of product ions in the second MS analysis stage. This process can be achieved either by using successive mass analyzers spatially or by conducting the steps of MS/MS at separate times. Each precursor ion can produce a unique pattern of product ions with good consistency and better sensitivity than the full scan, so that these diagnostic ions can be used as unambiguous evidence for structural elucidation or confirmation. The most well-known tandem mass spectrometry technique is collision-induced dissociation (CID), which breaks precursor ions by an energy-transfer ion/molecule reaction when the kinetic energy of both precursor ions and inert buffer gas molecules, accelerated by the electric/magnetic field, is converted into internal energy and finally cleaves the weakest bonds of the precursor ions, producing fragments (Wells and McLuckey, 2005). Besides MS/MS, more structural information can be obtained by the fragmentation of product ions or fragmentation in multiple stages, which is called multiple-stage tandem mass spectrometry (MSn). Table 14.1 gives a summary of the typical dissociation methods and the corresponding gas reactions of tandem mass spectrometry for proteomic analysis.
Probing radical versus proton migration in the aniline cation with IRMPD spectroscopy
Published in Molecular Physics, 2023
Laura Finazzi, Jonathan Martens, Giel Berden, Jos Oomens
Mechanistic insights into radical and proton migration processes have been obtained from quantum-chemical computations [16,18], as well as from experimental investigations. These experimental mass spectrometry studies must be able to distinguish isomeric ion structures that differ only in the location of a single H or H, i.e. they must be sensitive to the regioselectivity of protonation and radical formation. Distinguishing structures of the same m/z-value is obviously a challenge in mass spectrometry [19,20], and classical structural elucidation tools rely on tandem mass spectrometry methods, such as collision induced dissociation (CID) [20] or ion-molecule reactions [21]. An alternative, relatively new structural method in MS involves different implementations of ion spectroscopy, which have been extensively employed to characterise CID and ExD reaction products of small peptides [21–30]. These methods provide unique IR fingerprints that relate sensitively to the product ion isomeric structure, including the location of protons and radicals.
Structures and binding energies for complexations of different spin states of Ni+ and Ni2+ to aromatic molecules
Published in Molecular Physics, 2019
Boutheïna Kerkeni, Adelia J. A. Aquino, Michael R. Berman, William L. Hase
Transition metal cation-benzene (Bz) complexes are of particular broad interest, because of their relevance for catalysis and biological processes [21–23], and the fundamental importance that aromatic π-bonding has for organometallic chemistry [2]. Study of transition metal-Bz complexes provides a basic model for understanding d-π binding interactions [2,24,25] and may be used to assist in building new cluster assembled materials. For example, organometallic polymers made of an alternation of metal cations and Bz rings may provide a new class of one-dimensional conductors [26]. In gas-phase studies, many metal cation-Bz species have been studied with mass spectrometry [27–32], collision-induced dissociation [29], equilibrium mass spectrometry [30], and UV-vis photodissociation [27,28], to determine their bond energies. Theory has examined their structures and energetics [12,15,33–37]. As shown by Kaya and co-workers, various metal cation-Bz complexes form fascinating multiple-decker sandwiches [31]. Structures and energies for Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ binding to Bz and Bz2 have been studied with MP2, CCSD, and CCSD(T) theories [38]. Although many transition metal cation-Bz complexes have been studied, significant issues remain about their electronic structure and bonding.
Purification, biochemical, and thermal properties of fibrinolytic enzyme secreted by Bacillus cereus SRM-001
Published in Preparative Biochemistry and Biotechnology, 2018
Manoj Kumar Narasimhan, Selvarajan Ethiraj, Tamilarasan Krishnamurthi, Mathur Rajesh
The lone band obtained during the SDS-PAGE assay (∼1 mm thickness) of purified fibrinolytic enzyme was excised using a sterile sharp scalpel and minced to small pieces. The pieces were processed for mass spectrometry analysis according to the method reported in the literature.[38] The sample was digested in 50 mM ammonium bicarbonate buffer with 2 pmol of sequencing grade Trypsin-Ultra™ (New England Biolabs, Ipswich, MA, USA). The digested samples were analyzed on an ultrafast liquid chromatography (UFLC) system (Shimadzu) coupled to an electrospray ionization-quadrupole-time of flight (ESI-Q-TOF) mass spectrometer (Bruker Impact HD). The peptide sample (5 µL) was separated on a C18 RPLC column (Zorbax Eclipse plus, 4.6 × 100 mm2, 3.5 µm) with 0.4 mL/min flow rate and a 30 min solvent gradient from 2% A (water with 0.1% formic acid) to 70% B (acetonitrile with 0.1% formic acid). The quadrupole-time of flight-mass spectrometry (Q-TOF-MS) was operated in data-dependent collision-induced dissociation-mass spectrometry/mass spectrometry analysis mode, and the MS/MS data were searched with Mascot (Matrix Science, London, UK) to identify the tryptic peptides and proteins.