Instruct provides mass spectrometry infrastructure and expertise jointly between the Universities of Oxford and Utrecht. These centres provide access to cutting-edge mass spectrometers and organise regular training workshops.
Visits to the centre range from one day to a full week, depending on the complexity and number of experiments to be performed, and the experience of the visitor in MS. While mass spectrometry is applicable to almost any protein system, probably the single most important consideration is sample purity. To ensure a successful visit it is important to have tested the purity of the sample before visiting the centre.
A number of resources exist in the literature including protocols and background information providing the means for a visitor to aquaint themselves with the application of MS to structural biology.
Mass spectrometry (MS) is a gas-phase technique, which relies on the ionisation of the molecules of interest and their transferral into vacuum. For structural biology studies, nanoelectrospray is the most commonly employed ionisation technique as it allows proteins to be introduced into the gas-phase in their native buffers.
Once in the gas phase the ions are separated according to their mass-to-charge ratio using an analyser, and detected. Different analysers have different benefits, such as resolution, or mass range. Some instruments, so-called 'hybrid mass spectrometers', have two or more analysers and allow tandem-MS experiments. In these experiments an initial mass spectrum is acquired, then a sub-population of ions are selected for activation in a collision cell. The ensuing dissociation products are separated in the second analyser, enabling the detailed interrogation of sample composition.
Complementary to this mass separation, ions can also be separated according to their physical size. This is achieved using ion-mobility spectrometry, which is typically introduced as an additional stage within a mass spectrometer. The size measurement can then be used to restrain structural modelling of the protein in question.
MS is a useful analysis tool subsequent to various in-solution manipulations, such as cross-linking, or hydrogen-deuterium exchange.
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