Matrix-assisted laser desorption/ionization accuracy

Ramirez, J. Fenselau, C. Factors contributing to peak broadening and mass accuracy in the characterization of intact spores using matrix-assisted laser desorption/ionization coupled with time-of-flight mass spectrometry. J. Mass Spectrom. 2001,36, 929-936. 

R. M. Whittal, L. M. Russon, S. R. Weinberger, and L. Li. Functional Wave Time-Lag Focusing Matrix-Assisted Laser Desorption/Ionization in a Linear Time-of-Flight Mass Spectrometer Improved Mass Accuracy. Anal Chem., 69(1997) 2147-2153. 

Yau, P.M. and Burlingame, A.L. (2002) Identification of acetylation and methylation sites of histone H3 from chicken erythrocytes by high-accuracy matrix-assisted laser desorption ionization-time-of-flight, matrix-assisted laser desorption ionization-postsource decay, and nanoelectrospray ionization tandem mass spectrometry. Analytical Biochemistry, 306, 259-269. 

In 1974, Comarisov and Marshall60 developed Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). This technique allows mass spectrometric measurements at ultrahigh mass resolution (R = 100000-1000000), which is higher than that of any other type of mass spectrometer and has the highest mass accuracy at attomole detection limits. FTICR-MS is applied today together with soft ionization techniques, such as nano ESI (electrospray ionization) or MALDI (matrix assisted laser/desorption ionization) sources. 

Technological advances of ion-trap mass spectrometers are the ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and the recently released technique, the Orbitrap Fourier transform mass spectrometry (Hu et al., 2005), which enable the determination of molecular formulae with a high mass resolution and mass accuracy in mixtures. Today these ion-trap mass spectrometers are most frequently coupled with atmospheric pressure ionization (API) techniques such as electrospray ionization (ESI) (e.g., Fievre et al., 1997 Qian et al., 2001 Kujawinski et al., 2002 Llewelyn et al., 2002 Stenson et al., 2002,2003 Fard et al., 2003) or matrix-assisted laser desorption/ionization (MALDI) (e.g., Solouki et al.,... 

Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) routinely gives MW values with an accuracy of 0.1% or better, and has become increasingly popular for the mass measurement of biopolymers [1]. The technique is simple, rugged, has a mass range in excess of 200,000 Da, and is extremely sensitive, requiring low nanomole to picomole amounts of material. Additionally, the technique is relatively insensitive to the presence of various salts and buffers that are often associated with the isolation of biomolecules. 

Recent advances in protein analysis by MS are due to the introduction of electrospray ionization (ESI), matrix-assisted laser desorption ionization (MALDI), MSN scan modes, as well as improvements in instrument sensitivity, resolution, and mass accuracy. With these improved techniques, researchers will continue to use MS to help elucidate primary, secondary, and to a lesser extent, tertiary structure of proteins. 

Vorm, O., and Mann, M. (1994). Improved Mass Accuracy in Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry of Peptides, J. Am. Soc. Mass Spectrom. 5 955-958. 

Schweer, J., Samecki, J., Mayer Posner, F., Mullen, K., Rader, H.J., and Spickermann, J., Pulsed-Laser Polymerization/Matrix-Assisted Laser Desorption/ionization Mass Spectrometry. An approach toward Free-Radical Propagation Rate Coefficients of Ultimate Accuracy, Macromolecules 29, 4536 (1996). 

Zhu, H., Yalcin, T., and Li, L., Analysis of the Accuracy of I3eteriiiming Average Molecular Weights of Narrow Polydispersity Polymers by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry, /. Am. Soc. Mass Spectrom., 9, 275, 1998. 

In the latest developments, matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has been employed for detection of proteins with the capability to determine their M, with high accuracy. 

Zhu H, Yalcin T, and Liang L (1998) Analysis of the accuracy of determining average molecular weights of narrow polydispersity polymers by matrix-assisted laser desorption ionization time-of-flight mass sepctrometry. Journal of the American Society for Mass Spectrometry 9 275-281. 

Moskovets, E., Chen, H.S., Pashkova, A., Rejtar, T., Andreev, V., and Karger, B.L. (2003) Closely spaced external standard a universal method of achieving 5 ppm mass accuracy over the entire MALDI plate in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Commun. 

Edmondson, R.D.,RnsseU,D. (1996) Evalnation of matrix-assisted laser desorption ionization-time-of-flight mass measurement accuracy by using delayed extraction. J. Am. Soc. Mass Spectrom., 7, 995. 

Several mass spectrometric techniques including fast atom bombardment (FAB), plasma desorption (PD), matrix-assisted laser desorption/ionization (MALDI), and electrospray (ES) mass spectrometry (MS) are presently available for the analysis of peptides and proteins (Roepstorff and Richter, 1992). Of these techniques, mainly PDMS has gained footing in protein laboratories because the instrumentation is relatively cheap and simple to operate and because, taking advantage of a nitrocellulose matrix, it is compatible with most procedures in protein chemistry (Cotter, 1988 Roepstorff, 1989). Provided that the proper care is taken in the sample preparation procedure most peptides and small proteins (up to 10 kDa) are on a routine basis amenable to analysis by PDMS. Molecular mass information can be obtained with an accuracy of 0.1% or better. Structural information can be gained by application of successive biochemical or chemical procedures to the sample. 

The matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technique is suitable to determine the presence of molecules of higher molecular weight with high accuracy, and it has been applied with success to study procyanidin oligomers and other complex phenolic mixtures [67, 141]. 

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