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Mass Spectrometric Analysis
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
Structure elucidation of the two major components of partricin also made extensive use of chemical degradation and derivatization combined with mass spectral analyses [192]. Fast atom bombardment was used to determine the molecular weights of the underivatized components; positive and negative ion spectra exhibited (M + H)+ and (M − H)− ions, respectively. In addition, high-resolution EI spectra established elemental compositions of decomposition products. The positions of carbonyl oxygens in the macrolide ring were determined in mepartricin A and B, the active antifungal and antiprotozoal methyl esters of partricin A and B [193]. This was obtained from high-resolution EI spectra of the product obtained after reduction by lithium borodeuteride and methylation of hydroxyl groups by methyl iodide in the presence of sodium hydride in tetrahydrofuran. From these results, HPLC retention times [192], and FAB spectra of the ayfactin components, ayfactin and partricin are probably identical. Other previously isolated antibiotics suspected of being identical to partricin are levorin, hepamycin, gedamycin, and vacidin A.
Protein/Peptide Sequence Analysis by Mass Spectrometry
Published in Ajit S. Bhown, Protein/Peptide Sequence Analysis: Current Methodologies, 1988
Of all the mass spectrometric techniques in use today for polypeptide structure determinations, fast atom bombardment, or FAB analysis, is employed most often. The introduction of FAB mass spectrometry has made this instrumentation a convenient approach to sequence analysis of polypeptides, with sensitivities comparable to Edman sequencing techniques. This methodology, a variant of secondary ion mass spectrometry (SIMS), has two attractive advantages. First, the polypeptide needs no prior derivitization to render it suitable for analysis, and second, molecules containing up to about 100 residues1 are accessible to this methodology. The ability to reach such high masses is the result of the recent development of high field magnets that allow analysis at high accelerating voltages, thus preserving ion beam stability and sensitivity.2 In the future, application to larger molecules may, hopefully, succeed. However, at present, most use for this technique has been with peptides derived from larger protein molecules by enzymatic or chemical means or with intact isolates. Several reviews of this subject have been recently published that are useful for further reading.3-5
Chemical Structure of Lipid A: Recent Advances in Structural Analysis of Biologically Active Molecules
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Zähringer, Buko Lindner, Ernst T. Rietschel
Fast Atom Bombardment or Liquid Secondary Ion Mass Spectrometry The terms fast atom bombardment mass spectrometry (FAB-MS) and liquid secondary ion mass spectrometry (LSI-MS) are used synonymously. The nature of the liquid matrix in which the sample is dispersed rather than the charge of the incident particle is of importance for the generation of ions. The first FAB-MS investigations by Takayama and coworkers were performed on lipid A monophosphate preparations of S. enterica sv. Typhimurium, purified by high-performance liquid chromatography (HPLC). FAB mass spectra were obtained in the positive and negative ion mode, and both modes gave quasimolecular ions allowing the exact determination of the molecular masses (62). The HPLC elution profile allowed an analysis of the heterogeneity of the lipid A preparation. In addition to the molecular mass peaks, FABMS analysis provided the diagnostic fragment origi nating from cleavage at the C-1’-0-C-6 glycosidic bond (m/z 1087) and permitting the conclusion that GlcN (II) carried one dimethyl phosphate, two 14:0(3-OH) residues, one 14:0, and one 12:0 residue (63). Fragments derived from the reducing region of lipid A [GlcN (I)] were not observed in the positive ion FABMS but could be calculated from the difference of the molecular mass and the fragment of the oxonium ion (mlz 1087). In this case, GlcN (I) carried two 14:0(3-OH) fatty acyl groups, which, however, could not be assigned to specific positions 2, 3, or 4 of GlcN (I) or to one of the hydroxyl groups of the two 14:0(3-OH) residues. Nevertheless, the FAB-MS analysis not only confirmed the presence of acyloxyacyl residues, as earlier suggested by chemical analysis (38), but also allowed for the first time the assignment of the two acyloxyacyl residues to the distal GlcN (II). It was thus realized that in S. enterica sv. typhimurium lipid A, GlcN (II) carried four, and GlcN (I) only two acyl groups, i.e., that the fatty acid distribution over the two GlcpN residues was asymmetric (see Table 3). In quite a similar way, the symmetric distribution of fatty acids (3 + 3) was demonstrated in Neisseria gonorrhoeae lipid A (64), and an acylation pattern first recognized in Chromobacterium violaceum, however, in this first case by chemical analysis (37).
Advances in the proteomics of amniotic fluid to detect biomarkers for chromosomal abnormalities and fetomaternal complications during pregnancy
Published in Expert Review of Proteomics, 2019
Aayushi Vasani, Maushmi S. Kumar
Two commonly used methods for producing source ions are matrix-assisted laser desorption ionization detected by time of flight and mass spectrophotometry (MALDI-TOF-MS) and electrospray ionization (ESI)-Tandem MS; which follows their analysis by the tandem mass analyzer. MALDI is based on the identification of a molecule on the basis of small molecular fragments produced by high energy laser beams which are detected and identified by their different m/z ratios. Peptides and polymers upto m/z 100,000 were dealt by fast atom bombardment mass spectrometry (FABMS) and secondary ion mass spectrometry (SIMS) by Tanaka et al. in 1988 where they also used laser desorption-time of flight MS for protein identification [9]. In this technique, gas phase ions are introduced in ion source and are sent to mass analyzer for differentiation according to their m/z ratio.
10H-1,9-diazaphenothiazine and its 10-derivatives: synthesis, characterisation and biological evaluation as potential anticancer agents
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Beata Morak-Młodawska, Krystian Pluta, Małgorzata Latocha, Małgorzata Jeleń, Dariusz Kuśmierz, Kinga Suwińska, Aleksander Shkurenko, Zenon Czuba, Magdalena Jurzak
Melting points were determined in open capillary tubes on a Boetius melting point apparatus and are uncorrected. The 1H NMR, COSY, ROESY, HSQC, HMBC spectra were recorded on an AscendTM 600 spectrometers at 600 MHz in deuteriochloroform with tetramethylsilane as the internal standard. The 13C NMR spectrum was recorded at 75 MHz. Electron impact mass spectra (EI MS), fast atom bombardment mass spectra (FAB MS, in glycerol), chemical ionisation (CI MS) were run on a Finnigan MAT 95 spectrometer at 70 eV and HR MS was run on a Brucker Impact II. The thin layer chromatography was performed on silica gel 60 F254 (Merck 1.05735) with CHCl3-EtOH (10:1 v/v) and on aluminium oxide 60 F254 neutral (type E) (Merck 1.05581) with CHCl3-EtOH (10:1 v/v) as eluents.
Water-soluble porphyrin-PAMAM-conjugates of melphalan and their anticancer activity
Published in Drug Development and Industrial Pharmacy, 2018
Julio César Ramírez-Arroniz, Elena Martínez Klimova, Luis Daniel Pedro-Hernández, Ulises Organista-Mateos, Sandra Cortez-Maya, Teresa Ramírez-Ápan, Antonio Nieto-Camacho, José Calderón-Pardo, Marcos Martínez-García
1 H and 13 C NMR spectra were recorded on a Varian Unity-300 MHz (NMR Laboratory, Urbana, IL) with tetramethylsilane (TMS) as an internal reference. Infrared (IR) spectra were measured on a Nicolet FT-SSX spectrophotometer (Thermo Fisher Scientific Co., Waltham, MA). Elemental analysis was determined by Thermo Scientific, model Flash 2000. Fast atom bombardment (FAB)+ mass spectra were taken on a JEOL JMS AX505 HA instrument (JEOL, Tokyo, Japan). Electrospray mass spectra were taken on a Bruker Daltonic, Esquire 6000 (Conquer Scientific, San Diego, CA). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) mass spectra were taken on a Bruker Omni FLEX using 9-nitroanthracene (9 NA) as a matrix (Conquer Scientific). The Ultraviolet–visible (UV-Vis) absorption spectra were obtained at room temperature with a Shimadzu 2401 PC spectrophotometer (Shimadzu, Koyoto, Japan). Samples were observed in a Zeiss LSM 800 confocal microscope (Zeiss, Oberkochen, Germany), the excitation wavelength used was 488 nm (laser pinhole at 80% intensity). The emission wavelength was 400–700 nm.