The Synapt HDMS, publicly showcased last week, combines high efficiency ion-mobility based measurements and separations with high performance quadrupole, time-of-flight (TOF) mass spectrometry (MS). This additional dimension of separation leads to increased sample definition allowing the detection of previously unseen constituents as well as the detection and measurement of conformational changes in small molecules and proteins.
The instrument allows the separation of differently folded proteins and even allows calculation of their cross-sectional areas. This can be of enormous value to the structural biology research because it can highlight variations in protein structure.
"This technique potentially allows the detection of any conformational change and can tell you whether there is more than one conformation of a protein present in a sample," said Alistair Wallace, marketing manager of MS and proteomics at Waters.
"Our research into biopharmaceutical applications has shown that our technology provides more information on pegylated proteins and the glycosylation states of monoclonal antibodies than any other technique allowing companies to make decisions on their products more quickly," he continued.
The instrument also makes more detailed analysis of intact protein complexes, drug-protein complexes and protein-ligand affinities possible. The ability to separate fragment ions by their mobility allows the extension of protein sequence coverage as well as enhancing the detection and characterization of post-translational modifications.
The system makes use of the fact that smaller ions transfer faster than larger ions, even if they have the same mass and charge, in much the same way as when two pieces of paper, one crumpled up into a ball and the other still flat, are dropped. The crumpled up piece of paper falls faster and hits the ground first.
According to Wallace, the instrument is the first commercial instrument to combine high-efficiency ion mobility separation (IMS) with tandem MS.
The instrument can be coupled with Waters' ultra performance liquid chromatography (UPLC) Acquity system allowing the separation of complex mixtures before they enter the MS system.
The samples are ionized using either electron spray ionisation (ESI) or atmospheric pressure chemical ionization (APCI) before they pass through two 90o direction changes which filter out non-charged and solvent molecules, cleaning up the ion spray.
The ions then pass through a quadrupole filter which can either be set to filter out all but a selected mass range or left in a wide band mode which lets all ions pass through.
The enabling technology inside the instrument, dubbed 'Triwave', traps and releases packets of ions before they are separated in the IMS chamber, based on their mobility. The ions are then transferred to an orthogonal acceleration (oa) TOF mass spectrometer. The configuration of the instrument also allows time aligned parallel (TAP) fragmentation studies to aid detailed structural analysis.
The Triwave system overcomes the problems encountered using conventional ion mobility separation devices, where only a small percentage of the total ions are detected, resulting in low sensitivity. The Triwave device enables high efficiency transmission of the ions to the oa-TOF analyser, enabling mobility-based separations at the limits of MS detection.
Several research groups are already taking advantage of the new technology. For example, the system is being used by Dr Manajit Hayer-Hartl, of the Max Planck Institute, to study the role of protein misfolding in neurodegenerative diseases such as Huntington's.
The University of Oxford recently acquired one of the instruments to study interactions between proteins and small molecules. Professor Chris Schofield, of Oxford University, said: "We hope it will enable us to study the effects of binding events on protein conformation in an efficient manner and complement data obtained from high resolution, but time consuming techniques such as X-ray crystallography and NMR."
