Laser desorption mass

Thermal electrocyclizations of perhalogenated 1,3-butadienes yield perhalogenated cyclobutenes which can be solvolysed to 3,4-dihydroxy-3-cydobutene-l,2-dione ( squaric acid") and its derivatives (G. Maahs, 1966 H. Knorr, 1978 A.H. Schmidt, 1978). Double CO extrusion from fused cyclobutenediones has been used to produce cycloalkynes, e.g., benzyne from benzocyclobutenedione by irradiation in an argon matrix (O.L. Chapman, 1973) and cyc/o-Ci8, cyclo-Cn, etc. by laser desorption mass spectroscopy of appropriate precursors (see section 4.9.8). 

Laser-desorption mass spectrometry (LDMS) or matrix-assisted laser desorption ionization (MALDI) coupled to a time-of-flight analyzer produces protonated or deprotonated molecular ion clusters for peptides and proteins up to masses of several thousand. 

Matrix-assisted laser desorption mass spectrometry (MALDI-MS) is, after electrospray ionization (ESI), the second most commonly used method for ionization of biomolecules in mass spectrometry. Samples are mixed with a UV-absorbing matrix substance and are air-dried on a metal target. Ionization and desorption of intact molecular ions are performed using a UV laser pulse. 

Automated organic and elemental ion mapping of TLC plates by LMMS techniques, without focus correction, has been reported [802,839]. One of the early TLC-MS scanners used laser desorption combined with Cl detection [807,808]. The use of laser desorption mass spectrometry (LDMS), in connection with TLC separations, allows sampling of a very small area of a spot (ca. 5 im). In this way spot homogeneity can be determined (e.g. in the case of overlapping components), and also leaves the bulk of the material unaffected for further study. An important advantage... 

LDMS Laser desorption mass spectrometry desorption/ionisation... 

Posthumus, M. A. Kistemaker, P. G. Meuzelaar, H. L. C. Laser desorption-mass spectrometry of polar nonvolatile bio-organic molecules. Anal. Chem. 1978, 50, 985-991. 

MALARIA DETECTION BY LASER DESORPTION MASS SPECTROMETRY... 

Demirev, P. A. Feldman, A. B. Kongkasuriyachai, D. Scholl, P. Sullivan, D. J. Kumar, N. Detection of malaria parasites by laser desorption mass spectrometry. 

Fenyo, D. Chait, B. T. Johnson, T. Lindsey, J. S. Laser desorption mass spectrometry of synthetic multiporphyrin arrays. J. Porph. Phthalocyan. 1997, 1, 93-99. 

Spengler, B. Kirsch, D. Kaufmann, R. Metastable decay of peptides and proteins in matrix-assisted laser-desorption mass spectrometry. Rapid Comm. Mass Spectrom. 1991, 5,198-202. 

Mass spectral data have also been employed for biological studies aimed at determining the distribution of quinolizidine alkaloids within a plant. For instance, the analysis of stem sections of Lupinus polyphyllus and Cytisus scoparius by laser desorption mass spectrometry led to the conclusion that these alkaloids are restricted to the epidermis and probably also to the neighboring one or two subepidermal cell layers <1984MI230>. 

R. D Agata, G. Grasso, S. Parlato, S. Simone, and G. Spoto, The Use of Atmospheric Pressure Laser Desorption Mass Spectrometry for the Study of Iron gall Ink, Appl. Phys. A, 89, 91 95 (2007). 

Figure 6.9 Laser desorption mass spectra of extracts of the Murchison and Allende carbonaceous chondrites and an extraction from the K/T boundary. (Adapted from Becker L, Poreda R. J. and Bunch T. E., 2000 by permission of the Proceedings of the National Academy of Sciences 97 2979)...

R. C. Beavis and B. T. Chait. Cinnamic Acid Derivatives as Matrices for Ultraviolet Laser Desorption Mass Spectrometry of Proteins. Rapid Commun. Mass Spectrom., 3(1989) 432-435. 

P. Juhasz, C. E. Costello, and K. Biemann. Matrix-Assisted Laser Desorption Mass Spectrometry with 2-(4-Hydroxyphenylazo)benzoic Acid Matrix. J. Am. Soc. Mass Spectrom., 4(1993) 399-409. 

R. S. Bordoli, K. Howes, R. G. Vickers, R. H. Bateman, and D. J. Harvey. Matrix-Assisted Laser Desorption Mass Spectrometry on a Magnetic Sector Instrument Fitted with an Array Detector. Rapid Commun. Mass Spectrom., 8(1994) 585-589. 

Koch [82] and optimized further by us. The polyphenylene 28, which represents a first-generation dendrimer, forms 28 new bonds yielding the planar polycyclic aromatic hydrocarbon 56 (Scheme 23). Owing to its extreme insolubility in all common solvents, PAH 56 is characterized by laser desorption mass spectrometry based on its M+ peak at miz =1621. 

Hillenkamp, F. Influence of the wavelength in high-irradiance ultraviolet laser desorption mass spectrometry of organic molecules. Anal. Chem. 1985, 57, 2935-2939. 

The first of two stays of the senior author at Iowa State University was supported by a contract between Ae United Nations Industrial Development Organization and Ae National Chemical Laboratory, administered in the United States by the Carl Duisberg Society, Inc. This work was also supported by the Engineering Research Institute of Iowa State University. The authors thank Ron Niece, Cynthia Wadsworth, Nick Strickland, and Tony Grabski of the University of Wisconsin Biotechnology Center for providing confirmation of the amino acid sequence, and Brian Chait and Ron Beavis of Rockefeller University for attempting matrix-assisted laser desorption mass spectroscopy on Ac enzyme. This article is N(X Communication No. 4950. 

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