- Soft laser desorption
Infobox chemical analysis
name = Soft laser desorption
acronym = SLD
Biomolecules Synthetic polymers
Matrix-assisted laser desorption/ionization Surface-enhanced laser desorption/ionization
Soft laser desorption is
laserdesorption of large molecules that results in ionizationwithout fragmentation. "Soft" in the context of ionformation means forming ions without breaking chemical bonds. "Hard" ionization is the formation of ions with the breaking of bonds and the formation of fragment ions.
The term "soft laser desorption" has not been widely used by the
mass spectrometrycommunity, which in most cases uses matrix-assisted laser desorption/ionization(MALDI) to indicate soft laser desorption ionization that is aided by a separate matrix compound. The term soft laser desorption was used most notably by the Nobel Foundationin public information released in conjunction with the 2002 Nobel Prize in Chemistry. [cite news | first= | last= | coauthors= | title=The Nobel Prize in Chemistry 2002: Information for the Public | date=9 October 2002 | publisher=The Nobel Foundation | url =http://nobelprize.org/nobel_prizes/chemistry/laureates/2002/public.html | work = | pages = | accessdate = 2007-08-29 | language = ] Koichi Tanaka was awarded 1/4 of the prize for his use of a mixture of cobalt nanoparticles and glycerolin what he called the “ultra fine metal plus liquid matrix method” of laser desorption ionization. With this approach, he was able to demonstrate the soft ionization of proteins. [ cite journal|title=Protein and polymer analyses up to "m/z" 100 000 by laser ionization time-of-flight mass spectrometry|journal= Rapid Communications in Mass Spectrometry|date=1988|first=Koichi|last=Tanaka|coauthors=Hiroaki Waki, Yutaka Ido, Satoshi Akita, Yoshikazu Yoshida, Tamio Yoshida, T. Matsuo|volume=2|issue=8|pages=151–153|doi=10.1002/rcm.1290020802|format=|accessdate=2007-08-29 ] The MALDI technique was demonstrated (and the name coined) in 1985 by Michael Karas, Doris Bachmann, and Franz Hillenkamp, [cite journal |author=Karas, M.; Bachmann, D.; Hillenkamp, F. |title=Influence of the Wavelength in High-Irradiance Ultraviolet Laser Desorption Mass Spectrometry of Organic Molecules |journal=Anal. Chem. |volume=57 |issue= |pages=2935–9 |year=1985 |pmid= |issn= |doi=10.1021/ac00291a042] but ionization of proteins by MALDI was not reported until 1988, immediately after Tanaka's results were reported.
Some have argued that Karas and Hillenkamp were more deserving of the Nobel Prize than Tanaka because their crystalline matrix method is much more widely used than Tanaka's liquid matrix. [cite news | first=Laura | last=Spinney | coauthors= | title=Nobel Prize controversy | date=December11, 2002 | publisher= | url =http://cmbi.bjmu.edu.cn/news/0212/55.htm | work =The Scientist | pages = | accessdate = 2007-08-29 | language = ] [cite news | first= | last= | coauthors= | title=ABC News Online: 2002 Nobel chemistry choice sparks protest | date=Week of 13 December 2002 | publisher=Boston University | url =http://www.bu.edu/bridge/archive/2002/12-13/in-the-news.html | work =B.U. Bridge | pages = | accessdate = 2007-08-29 | language = ] Countering this argument is the fact that Tanaka was the first to use a 337 nm
nitrogen laserwhile Karas and Hillenkamp were using a 266 nm . The "modern" MALDI approach came into being several years after the first soft laser desorption of proteins was demonstrated.cite journal |author=Beavis RC, Chait BT |title=Matrix-assisted laser-desorption mass spectrometry using 355 nm radiation |journal=Rapid Commun. Mass Spectrom. |volume=3 |issue=12 |pages=436–9 |year=1989 |pmid=2520224 |doi=10.1002/rcm.1290031208] cite journal |author=Beavis RC, Chait BT |title=Cinnamic acid derivatives as matrices for ultraviolet laser desorption mass spectrometry of proteins |journal=Rapid Commun. Mass Spectrom. |volume=3 |issue=12 |pages=432–5 |year=1989 |pmid=2520223 |doi=10.1002/rcm.1290031207] [cite journal |author=Strupat K, Karas M, Hillenkamp F |title=2,5-Dihidroxybenzoic acid: a new matrix for laser desorption-ionization mass spectrometry. |journal=Int. J. Mass Spectrom. Ion Processes |volume=72 |issue=111 |pages=89–102 |year=1991 |doi=10.1016/0168-1176(91)85050-V ]
Examples in mass spectrometry
matrix-assisted laser desorption/ionizationapproach [Karas, M.; Bachmann, D.; Hillenkamp, F., Influence of the Wavelength in High-Irradiance Ultraviolet Laser Desorption Mass Spectrometry of Organic Molecules. "Anal. Chem". 1985, "57", 2935-2939.] typically uses a small organic acid solid matrix, although liquids have been used. The light source is a pulsed IR or UV laser. The surface-enhanced laser desorption/ionization(SELDI) variand is similar to MALDI, but uses a biochemical affinity target. [Hutchens, T. W.; Yip, T. T., New desorption strategies for the mass spectrometric analysis of macromolecules. "Rapid Commun. Mass Spectrom." 1993, "7", 576-580.doi|10.1002/rcm.1290070703] cite journal |author=Poon TC |title=Opportunities and limitations of SELDI-TOF-MS in biomedical research: practical advices |journal=Expert review of proteomics |volume=4 |issue=1 |pages=51–65 |year=2007 |pmid=17288515 |doi=10.1586/14789422.214.171.124] The technique known as surface-enhanced neat desorption (SEND) [(Hutchens 1993] is a variant of MALDI with the matrix is covalently linked to the target surface.The surface-assisted laser desorption/ionization (SALDI) approach [Sunner, J.; Dratz, E.; Chen, Y.-C., Graphite surface-assisted laser desorption/ionization time-of-flight mass spectrometry of peptides and proteins from liquid solutions. "Anal. Chem." 1995, "67", 4335-42.] can be described as MALDI using a liquid plus particulate matrix. The desorption ionization on silicon (DIOS) approach [Wei, J.; Buriak, J. M.; Siuzdak, G., Desorption-ionization mass spectrometry on porous silicon. "Nature" 1999, "399", 243-246.] is laser desorption/ionization of a sample deposited on a porous silicon surface. The technique known as laser induced acoustic desorption (LIAD ) is transmission geometry LDI with a metal film target. cite journal|title=Laser-induced acoustic desorption|journal=International Journal of Mass Spectrometry and Ion Processes|date=12/1997|first=V. V.|last=Golovlev|coauthors=Allman, S. L.; Garrett, W. R.; Taranenko, N. I.; Chen, C. H.|volume=169-170|issue=|pages=69–78|id= |url=|format=|accessdate=2007-08-29|doi=10.1016/S0168-1176(97)00209-7 ] cite journal |author=Somuramasami J, Kenttämaa HI |title=Evaluation of a novel approach for peptide sequencing: laser-induced acoustic desorption combined with P(OCH(3))(2)(+) chemical ionization and collision-activated dissociation in a Fourier transform ion cyclotron resonance mass spectrometer |journal=J. Am. Soc. Mass Spectrom. |volume=18 |issue=3 |pages=525–40 |year=2007 |pmid=17157527 |doi=10.1016/j.jasms.2006.10.009 |issn=]
Matrix-assisted laser desorption/ionization
* [http://nobelprize.org/chemistry/laureates/2002/public.html The Nobel Prize in Chemistry 2002 – Information for the Public]
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