Talk:Matrix-assisted laser desorption/ionization

Trying to Keep NPOV in History of MALDI Section
201.147.87.66 made several edits in Matrix-assisted_laser_desorption/ionization section effectively arguing that the “ultra fine metal plus liquid matrix method” of Tanaka is not MALDI. This is debatable, so the change of with the proper combination of laser wavelength and matrix, MALDI can be used to ionize proteins to with the proper combination of laser wavelength and matrix, a protein can be ionized is consistent with NPOV.

The statement that the Tanaka and Karas/Hillenkamp demonstration of protein ionization occurred at the same time is incorrect. Note that Karas, M. and Hillenkamp, F. Laser desorption ionisation of proteins with molecular masses exceeding 10.000 daltons. Anal. Chem. 60 (1988) 2299-2301 cites Tanaka, K., Ido, Y., Akita, S., Yoshida, Y. and Yoshida, T. Proc. Second Japan-China Joint Symposium on Mass Spectrometry. Editors Matsuda, H. and Xiao-tian, L. (Osaka, Japan, 15-18 September 1987) p. 185-188 and the latter publication was an important consideration for the Nobel committee.

The argument about who deserved the 2002 Nobel Prize for soft desorption of ions is confused by the facts that Karas and Hillenkamp discovered and named MALDI yet Koichi Tanaka broke the 10 kDa barrier of laser desorption ionization of proteins. Good arguments can be made as to the relative importance of these contributions, but these arguments must be supported by facts.


 * --Kmurray 16:32, 4 May 2006 (UTC)

Good Review

 * Dreisewerd K., The Desorption Process in MALDI. Chem. Rev. 2003, 103, 395-425. DOI

From the Hillenkamp group gifing a good insight in development and history of MALDI! --Stone 09:43, 23 June 2006 (UTC)

Rbeavis changes
I am concerned about copyright and somewhat about appropriateness of some of the material. A chapter on MALDI informatics is not needed and inappropriate. I have asked for his input here.--Nick Y. 18:52, 30 January 2007 (UTC)

I can assure you that the material is mine and it does not have any copyright problems: I wrote the material myself (Ronald Beavis) with the help of David Fenyo. If it would be more appropriate to place this material under a separate heading, such as "Maldi informatics", I will be happy to move it there, leaving a link to the new article on the MALDI page.--RBeavis 23:05, 30 January 2007 (UTC)

I have removed my contribution from the MALDI page altogether. I actually hadn't read the rest of the article before I added my material. As one of the people originally involved in the development of MALDI, I can't support this version of the history of MALDI's origin. Frankly, this particular version of history was cooked up in the late 90's to discount Tanaka's original invention. I also have never been accused of copyright violation before (particularly by someone lurking on a web site): the contents of the section were part of a book chapter on the history of MALDI software development that was never used.

Prof. Ronald C. Beavis

Department of Medical Genetics

University of British Columbia

rbeavis@brc.ubc.ca

1-604-822-7805

--RBeavis 03:40, 31 January 2007 (UTC)


 * No offense was intended. I apologize if any was taken and thank you for your generous contribution. You need to understand that it is common for people to take chapters of books and paste them into science pages on wikipedia without the author's permission. I very specifically did not accuse anybody of anything. I only expressed concern and asked the question to be sure and verify. If it was your work being volunteered by some other person I think you would very much appreciate me asking the question. When we submit journal articles we all have to sign a release of copyright that states that it is ours to release. Not the case here. I ask the question as a concerned editor and then take your word for it. It is the honor system. Be thankful that someone is asking, just as when you are asked for your ID when you use your credit card. They don't have to but they are looking out for you when they do. For some reason many people today do not understand that the hard work of others is not theirs to take freely. Be aware however that you are releasing copyright by donating the text to wikipedia. Others may change it, maybe for the better, maybe for the worse. I agree with your decision to make a separate MALDI informatics page rather than include it here. If you have issues with the history section here perhaps we can fix that together. I would ask you to be careful to act as a balanced editor on this very controversial subject of which you are in part a subject of. Your input however is very welcome. People come here frequently and shift the viewpoint 180 degrees. As it is I think this is reasonably neutral. The most useful thing to contribute are verifiable facts. I hope that you understand that I am only being helpful and responsible and perhaps you are more informed for it. I do not make the rules. I find many flaws in the wikipedia system myself. I only try to contribute and be a good citizen. --Nick Y. 20:32, 31 January 2007 (UTC)

Crystallinity of prepared sample
Does it really matter that the sample crystallizes when the solvent evaporates (as is put quite strongly in the article at the moment)? I always thought that this just happens 'because it does', not because it's important. If so, then how and why do results differ with an amorphous sample? TheBendster 08:52, 22 April 2007 (UTC)


 * My understanding is that the co-crystalization of the matrix and analyte is very important in determining ionization efficiency. The variability in results between analyses is most dependent on the rate of evaporation and how the crystals form. Small fine crystals tend to produce more efficient ionization as well as exhibiting greater spatial homogeneity to the signal (where the laser is pointed). Larger crystals tend to have lower signal and require more hunting for "sweet spots". Of course the crystallization process is hard to control and in most cases depends heavily on analyst variables such as how the solvent is applied and things like placing it on top of a particular CRT monitor to get a good crystallization temperature. Remember the crystals are mostly matrix so crystallization of the sample really does not occur (except as an inclusion) so crystals are always formed. Sometimes mixtures of matrices are used but they still crystallize. Certainly there are non-crystal matrices (e.g. glycerol) but most modern MALDI involves co-crystallization of matrix and analyte.--Nick Y. 17:15, 23 April 2007 (UTC)


 * Thanks. That makes sense to me - smaller crystals will mean a higher surace area for evaporation, as well as greater homogeneity. I guess it also indicates that faster crystallization has taken place, which would lead to better inclusion of the analyte. TheBendster 08:48, 25 April 2007 (UTC)

WikiProject class rating
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:59, 10 November 2007 (UTC)

what happened to informatics component, notably post-translational issue?
Sorry, this is a thing with me LOL. What happened to this with a whole ( probably excessive ) section on informatics, http://en.wikipedia.org/w/index.php?title=Matrix-assisted_laser_desorption/ionization&oldid=104381377#Informatics:_Introduction. Certainly a tutorial on bioinformatics is probably not called for but the thing about MALDI versus normal sequencing is that you stand a chance of finding fragile modifications that may get lost if you just want to pick 1 of 20 amino acids at each blank. This comes up in places like immunology where small modificaitons to proteins could matter and many regulatory approaches use gross of subtle changes to acids. Added sugars and stuff are recnetly appreciated issues too. Send a link to Dendreon LOL( my personal tirade but a possible application). Nerdseeksblonde (talk) 12:40, 18 October 2009 (UTC)
 * It was cut. There's no reason that it couldn't be restored, although it would need editing to avoid WP:NOTHOWTO. --Kkmurray (talk) 01:21, 19 October 2009 (UTC)
 * From the edit summaries, it did look like part of it was moved somewhere but wasn't clear. Certainly this was a huge section and maybe it could have been integrated into other articles but you have to concede that taking a mixture of macro-molecules apart could create a data explosion both at raw level and after ambiguous assignment- and this problem would be inherent to MALDI for any application where it has merit. So, I think a reader could reasonably expect to find something on the topic but not a set of lecture notes. Since I've expressed personal "interest" in this topic, I may try to do some research and put together a short section but it may have some bias and other problems. Nerdseeksblonde (talk) 13:56, 20 October 2009 (UTC)

Ionization mechanism
"The matrix absorbs the laser energy and it is thought that primarily the matrix is desorbed and ionized (by addition of a proton) by this event." If I understand correctly, a quant of laser radiation (which is UV or IR, i.e. close to electronic levels in molecules) just excites an electron in a matrix molecule, and it goes away as in photoelectric effect. Now, we have cation left. Which means, a proton is NOT added but rather electron is subtracted => the phrase should be ... (by subtraction of an electron) ... or (by excitation of an electron) ... Please correct if it's wrong. Thanks. — Preceding unsigned comment added by Dinvlad (talk • contribs) 22:01, 11 August 2011 (UTC)

Microbial resistance
A role in the identification of bacterial resistance patterns - 10.1128/CMR.00058-12 JFW &#124; T@lk  22:33, 7 January 2013 (UTC)

Open data?
Is there open MALDI-TOF data? For example I just read a paper saying "All datasets generated for this study are included in the manuscript." Huh, they only gave the results from the software they used, not the raw MS data. --SCIdude (talk) 08:34, 1 July 2019 (UTC)


 * Yes! There is a MALDI-TOF data set of milk here. It's part of an R package of baseline correction methods that are detailed in Liland, K. H., Almøy, T., & Mevik, B. H. (2010). Optimal choice of baseline correction for multivariate calibration of spectra. Applied spectroscopy, 64(9), 1007-1016.. 2001:4C4C:1F9F:DB00:0:0:0:1000 (talk) 00:11, 1 March 2023 (UTC)