MALDI-TOF/TOF Mass Spectrometry (CRF Shared Facility)

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) emerged as an effective analytical tool use for studying the molecular mass determination, protein identification & characterization, identification of post translational modification, terminal sequencing and more other applications . In general, molecules in the gas phase (or species desorbed from a condensed phase) are ionized, and the ions are then accelerated by an electric field and separated on the basis of their mass-to-charge ratio (m/z) and further detected. A time-of-flight (TOF) mass spectrometer separates ions with identical kinetic energy but different m/z, since lighter ions travel faster than heavier ones. A mass spectrum is a chromatogram presenting the signal intensity (y-axis) versus m/z (x-axis). Interpretation of the fragmentation patterns and isotopic peaks can provide valuable clues for the structure determination of organic molecules. MALDI provides a 'soft' ionization source that prevents decomposition of fragile biomolecules, producing primarily singly charged, intact protein ions. The ions produced with the MALDI technique are analyzed using a time-of-flight (TOF) mass spectrometer, which is characterized by a high ion throughput and therefore high sensitivity.

Bruker UltrafleXtreme MALDI-TOF/TOF Mass Spectrometer

1. Acquire protein/ peptide mass information through MALDI -TOF/TOF technology, proteins identified by matching with data base in mascot.
2. Broadband mass resolving power up to 40,000 and 1 ppm mass accuracy for highest confidence.
3. Scanning speed: 2 kHz speed in TOF mode and 1 kHz in TOF/TOF mode
4. LID-LIFT process delivers MS/MS spectra with nominal mass resolution for peptides.
5. Laser-irradiation self-cleaning Ion source: ensures robust, long-term highest-performance operation.
   

Sample Preparation Guidelines Samples :

• Samples for MALDI-TOF analysis need to meet certain requirements for obtaining good spectra. The more careful you prepare samples the more likely a successful analysis will be.
• Samples can be submitted in solid, liquid, or solution form. If you are submitting a sample in solution, you should indicate the solvent on the submission form that your sample is dissolved in and other solvents in which your sample is soluble.
• Suitable solvents are ones that are volatile. For sample work up and purification fresh HPLC grade solutions should be use: water, ammonium hydrocarbonate, ammonium acetate, ammonium formiate,0.1% trifluoroacetic acid, 0.2% formic acid, methanol, acetonitrile, ethanol etc.Some samples can degrade if an acid or base is added to the sample. If you are submitting a sample that is sensitive to acid to base, please indicate so. Please supply the sample in a low-salt buffer (less than 20 mM).
• Avoid the use of non-volatile agents like salts (NaCl, CaCl2, KH2PO4), detergents (Tween, Triton, SDS), chaotropic agents (Urea, Guanidinium salts) and non-volatile solvents like DMSO, DMF, or Glycerol. If you can’t avoid these agents, purify. Dialysis, ZipTips, and RP-HPLC are good purification methods. After purification, lyophilize if possible. Ion exchange beads may work well for salt removal. The range for many samples/preparations is not very large, therefore it is necessary to have a good estimate of the sample amount because the sample amount may need to be varied on the target. The total amount of sample needed for MALDI analysis depends on the sample type. The larger the molecular weight the more sample concentration is needed.
• Give information like: structure, sequence, molecular weight, type of compound, biological activity, chemical reactivity, pH, sample amount/concentration, describe purification/isolation with focus on relative agents/solvents, known or suspected impurities, suitable solvents, hazardous properties: radioactivity, carcinogenicity, poison, or explosive.
  

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