Electrospray ionization , degradation

With the identities and amounts of amino acids known, the peptide is sequenced to find out in what order the amino acids are linked together. Much peptide sequencing is now done by mass spectrometry, using either electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI) linked to a time-of-flight (TOF) mass analyzer, as described in Section 12.4. Also in common use is a chemical method of peptide sequencing called the Edman degradation. 

Herbach, K.M., Stintzing, E.C., and Carle, R., Identification of heat-induced degradation products from purified betanin, phyUocactin and hylocerenin by high-performance liquid chromatography/electrospray ionization mass spectrometry, Rapid Commun. Mass Spectrom., 19, 2603, 2005 20, 1822, 2006. 

Gosetti, F. et ah. Oxidative degradation of food dye El33 Brilliant Blue FCF. Liquid chromatography-electrospray ionization mass spectrometry identification of the degradation pathway, J. Chromatogr. A, 1054, 379, 2004. 

Zhang and Nunes [92] studied the structure and the generation mechanism of a novel degradation product formed by oxidatively induced coupling of miconazole nitrate with butylated hydroxy toluene in a topical ointment studied by high performance liquid chromatography-electrospray ionization mass spectrometry and organic synthesis. 

Liquid chromatography was developed to analyze carbonyl (2,4-dinitro-phenyl) hydrazones with detection by diode array ultraviolet spectroscopy (DA-UV) and by atmospheric pressure negative chemical ionization (APNCI) mass spectrometry [716]. In addition, LC can be combined with electrospray ionization coupled on-line with a photolysis reactor for better detection and confirmation of photo degradation products [717]. 

Kamel AM, Zandi KS, Massefski WW. 2003. Identification of the degradation product of ezlopitant, a non-peptidic substance P antagonist receptor, by hydrogen deuterium exchange, electrospray ionization tandem mass spectrometry (ESI/MS/MM) and nuclear magnetic resonance (NMR) spectroscopy. J Pharm Biomed Anal 31 1211. 

There are no available data on the formation of hydroperoxides derived from DNA within cells. This is likely explained, at least partly, by the fact that DNA is a poorer target than proteins for OH radical as observed upon exposure of mouse myeloma cells to ionizing radiation . However, indirect evidence for DNA peroxidation within cells may be inferred from the measurement of final degradation products that may derive from thymine and guanine hydroperoxidation as the result of oxidation reactions mediated by OH radical and O2, respectively (Sections n.A.2 and n.E.2). It may be pointed out that the measurement of oxidized bases and nucleosides within DNA has been the subject of intense research during the last decade and accurate methods are now available . This includes DNA extraction that involves the chaotropic Nal precipitation step and the use of desferrioxamine to chelate transition metals in order to prevent spurious oxidation of overwhelming nucleobases to occur . HPLC coupled to electrospray ionization... 

Lamouroux, C., Aychet, N., Lelievre, A., Jankowski, C.K., Moulin, C. 2004. High-performance liquid chromatography with electrospray ionization mass spectrometry and diode array detection in the identification and quantification of the degradation products of calix[4]arene crown-6 under radiolysis. Rapid Commun. Mass Spectrom. 18 1493-1503. 

As part of a study to identify the degradation products of sulfur mustard, bis(2-chloroethyl) sulfide, the behavior of various sulfonium salts towards electrospray ionization mass spectrometry has been investigated. Among the compounds studied was 3 -(2-chloroethyl)pentamethylene sulfonium tetrafluoroborate. The ion was readily detected at the 0.01 M level with no ion fragmentation <1997JMP1247>. 

Lopez C, Valade AG, Combourieu B et al (2004) Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry. Anal Biochem 335 135-149... 

Coupling CE with electrospray ionization mass spectrometry (MS) can potentially be a very powerful tool for detecting and identifying product-related impurities in recombinant pharmaceuticals. Proteins can be detected in the femtomole range with this mode. Conceivably, the bioanalyst could perform a peptide map with CZE-MS and detect, identify, and sequence aberrant peptides derived from degradates. 

Tak, V. et al. Application of Doehlert design in optimizing the determination of degraded products of nerve agents by ion-pair liquid chromatography electrospray ionization tandem mass spectrometry, J. Chromatogr. A. 2007,1161,198-206. 

Kujawinski, E. B., Del Vecchio, R., Blough, N. V., Klein, G. C., and Marshall, A. G. (2004). Probing molecular-level transformations of dissolved organic matter Insights on photochemical degradation and protozoan modification of DOM from electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Mar. Chem. 92, 23—37. 

Although APCI can accommodate higher flow rates (up to approximately 2 mL/min), the source is usually operated at higher temperatures than an electrospray ionization source, which can lead to thermal degradation of the sample. This is especially problematic with the detection of fragile glucuronides, N-oxides, and sulfates. Either ion source can accommodate a wide range of EIPLC mobile-phase... 

Unfortunately, substantial problems remain with the CIEF-MS approach. Most importantly, the ampholyte used in CIEF co-elutes with the analyte and perturbs the electrospray ionization (ESI) process in a manner that suppresses analyte signal intensity and degrades mass resolution. In addition, the resolution of CIEF alone is not sufficient to separate proteins completely in complex samples. When proteins co-elute from an ESI source, some... 

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