Experiment-8: Determination of Molecular Weight of Intact Proteins using MALDI-TOF MS
To determine accurate molecular weight of intact proteins using MALDI TOF MS
Mass spectrometry deals with the accurate mass measurement by producing charged molecular species in vacuum and their separation by magnetic and electric fields based on mass to charge (m/z) ratio. MALDI is an efficient process for generating gas-phase ion of peptides and proteins for mass spectrometric detection. TOF is a mass analyzer in which the flight time of the ion from the source to the detector is correlated to the m/z of the ion. MALDI mass spectrometry is an attractive approach for determination of accurate molecular weight of intact proteins. Choice of the matrix depends on the type of analyte to be analysed. Majority of the matrices are suitable for UV laser. For some particular analytes (oligonucleotides and some non-covalent compounds), infrared laser (IR-MALDI) is used. Succinic acid is the commonly used matrix for IR-MALDI. However, water can be used in IR-MALDI since IR laser ionization is not restricted to any specific matrix.
One of the major advantage of MALDI is that is allows rapid analysis. TOF mass analyzer is mostly combined with MALDI, however, implication of FT-ICR analyzer can provide very accurate and reliable information regarding molecular mass. In this experiment, we will discuss the determination of molecular mass of four intact proteins; serum albumin, aldolase, amyloid A and apolipoprotein A-I, using MALDI-TOF mass spectrometry.
Figure 1. Crystal structures of the serum albumin (A), aldolase (B), amyloid A (C) and apolipoprotein A-I(D).Molecular weight of these four proteins were determined using MALDI-TOF MS