Types of Analysis

In the last decade or two, advances in mass spectrometry allow it to be applied to quantitative and qualitative analysis of compounds that are volatile or involatile. Modern separation methods combine in powerful ways with mass spectrometry.

Low Molecular Weight: Analysis of Small Molecules including Metabolomic Analysis

While electron ionisation (EI) coupled with GC/MS is the main technique for volatile compounds, the BMSF has expertise in a particularly sensitive and selective method based on negative ion mass spectrometry. This involves tagging the molecules of interest with a group that makes those molecules capture electrons and so form negative ions. The electron capture negative ion MS technique (ECNI MS) can be used effectively for many metabolite/marker and clinical mass spectrometry studies. Polar small molecules (involatile) are analysed by LC/MS (see below) using ionisation methods such as ESI and APCI. These methods are often useful in environmental analysis, metabolite analysis etc.

Proteins, Polymers and other High MW or Polar Molecules including Proteomics

LC/MS is now a mature method of analysis and it usually is coupled with electrospray ionisation (ESI) or atmospheric pressure chemical ionisation (APCI). Tandem mass spectrometry (MS/MS) is usually applied with these methods to facilitate structural characterisation of many types of compounds (including synthetic polymers) as well as to tailor a quantitative method that detects very low levels of a target analyte in highly complex mixtures. In addition to several LC/MS instruments, the BMSF is equipped with matrix assisted laser desorption/ionisation (MALDI) instruments which analyse samples deposited as solids on a plate. The BMSF is well equipped for the analysis of proteins, lipids, carbohydrates and other biopolymers. The BMSF is particularly experienced in protein identification using modern proteomic methods. In addition staff at the BMSF practice a wide range of quantitative proteomic analysis using isotopic labelling strategies to measure relative protein experession levels between samples and controls.

Mass Accuracy & High Resolution Analysis

The BMSF is equipped with instruments that measure the mass of molecules very accurately. This allows conclusions about their empirical formulae to be reached. It also makes analysis of mixtures easier because otherwise interfering species are resolved by the high resolution. The LTQ FT instrument is a very high resolution instrument for LC/MS and this is primarily used for proteins and other biomolecules.

Prior Separation and Fractionation

Separation methods such as gas and liquid chromatography (GC & LC) are essential in most applications and these are mostly performed on-line with the mass spectrometer. For proteomic analysis the use of very narrow columns in the nanoflow regime (for nanospray - a scaled down version of electrospray) is widely practised at the BMSF including the use of sophisticated 2-dimensional separations (LC-LC). Techniques such as 1 dimensional and 2 dimensional gel eletrophoresis (SDS PAGE & 2DE) are important off-line methods for large biomolecules such as proteins and nucleic acids. The BMSF has a comprehensive range of separation devices and mass spectrometers to address most analytical problems suited to mass spectrometry.

Analysis with Stable Isotopes

One of the most powerful advantages of mass spectrometry is its ability to resolve naturally occurring isotopes. This ability is used in quantitative mass spectrometry to greatly increase accuracy and precision. In proteomics a number of advanced labeling approaches allow the measurement of differential expression of proteins. Isotope enrichment methods can also be applied to trace the fate of molecules in living systems and the environment. The BMSF has extensive capability in these types of analyses.

Desorption Electrospray Ionisation (DESI)

The DESI technology is a simple, sensitive, gentle, and versatile ionization method that allows for the direct sampling of surfaces without any sample preparation and under ambient temperature and pressure conditions. This patented technology (patent #7335897) was first disclosed in Science, Vol. 306, #5695, pp. 471-473, October 2004. (seeĀ http://www.prosolia.com/omnispray.php).