Mass Spectrometry

Mass Spectrometry

Mass spectrometry [MS] is an analytical technique that identifies the chemical composition of a sample on the basis of the mass-to-charge ratio of charged ions. The technique has both qualitative and quantitative uses. Another way of thinking about MS is that of “the world’s most accurate scale” to weigh a molecule. The sophistication in instrument design has improved over the last 100 years allowing for a wide range of applications. ESI-MS had as its first uses, the ionization of intact chemical species but now has found wide acceptance in the identification of large biologically important molecules. At its root is this instruments ability to form charged ions from relatively non-volatile, thermally labile compounds. In the case of proteins, multiple charged ions are generated which serves to extend the useful mass range of the instrument. ESI-MS is often the method of choice for intact protein mass analysis coupled with reversed phase HPLC and for protein characterization through the use of peptide maps [mass fingerprinting].

Matrix assisted laser desorption/ionization, time of flight [MALDI-TOF] MS developed in 1987 is a highly sensitive technique that has expanded the useful mass range of bio-molecule analysis to over 300,000 Da. MALDI-TOF has also shown great value in the analysis of natural and synthetic polymers. The sample to be analyzed is mixed with a UV absorbing organic molecule [matrix] and dried. The resulting mixture is a co-crystal of sample and matrix. The sample is ionized typically using an N2 laser operating at 336 nm. The energy of the laser is mostly spent on ionization of the matrix which carries with it the vaporized and charged sample with little or no degradation. MALDI-TOF-MS is particularly useful for identification of polymer component end groups, purity, and overall molecular weight distribution. This data also provide us with the ability to calculate polydispersity values for synthetic polymer systems.

The various mass spec instrument design types that have been developed allow for a wide range of experiment types from quantification to structural elucidation. This type of instrumentation is now such an important tool that it can be found in most major biological chemical laboratories throughout the world.

The linking of mass specs to other convection techniques such as reversed phase HPLC [RPLC-MS] is a natural and synergistic combination. Now complex mixtures can be separated, quantified and identified on the fly. Structural information can be obtained on small molecules <1000 Da and complete protein sequence information can be obtained through the use of [RPLC-MSMS] peptide maps. Post translational modifications such as glycation, deamidation, oxidation, acetylation and phosphorylation can be detected localized and quantified. A proteins disulfide structure and glycosylation profile can be determined. This is just a partial list of the benefits of analysis using mass spec.

At Analytical Ventura, we have years of experience with almost all of the various forms of mass spectroscopy. Our scientists are happy to work with you to determine what type of mass spec technique will work best for you and to develop a protocol using individual or combined methods to solve your analytical challenges.

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