Analysing molecular structures

When we analyse a sample, we want to identify the molecules which are contained in it and maybe also in what amounts. Mass spectrometers are like a balance, only that they can weigh single, individual molecules and identify them based on their sum formula. We can also fragment molecules in a controlled way, and the pieces into which they break are characteristic for the structure so that we can for example assign the correct isomer.

An exciting recent development allows us to use mass spectrometry in combination with a technique called ion mobility, which enables us to look at the shape and size of particles directly – a bit like under a microscope. With this approach the mass, structure and conformation of a molecule can be determined at the same time within one rapid experiment, even from a complex sample.

The samples we study are typically complex organic or biological molecules. We use a solution which contains the molecules of interest, and a technique called electrospray ionisation (ESI) to produce a fine mist of droplets which is introduced into the vacuum of the mass spectrometer. It is possible to keep solutions of biomolecules ‘native’ so that important noncovalent complexes of biological molecules survive the transfer into the gas phase intact and we can study biomolecular structures in that way.

You will learn how to make molecules ‘fly’, and how to operate a high-tech instrument used for analysis of complex organic or biological molecules. You will investigate intact protein molecules in the native and denatured state and study their conformational change upon denaturation. You will also analyse the amino acid sequence of the proteins by using controlled fragmentation inside the mass spectrometer, and search for the presence of post-translational modifications. You will use bio-informatics and database searching to identify the protein samples. There is also the opportunity to study your ‘own’ molecules with this technique.