In metabolomics, we are detectives, gathering corroborative evidence from various parameters, such as accurate mass, retention time, etc. in order to draw a valid and correct conclusion.
“Noun: corroborative evidence – additional evidence or evidence of a different kind that supports a proof already offered previously”
Progenesis QI has just been given another piece of decisive corroborative evidence: you can now search using the new Waters Metabolic Profiling CCS library. The initial version of the library includes 956 metabolites and lipids, over 900 of which include CCS measurements and two thirds of which have MS/MS spectral information.
What is CCS?
Ion Mobility Separation (IMS) is a process that differentiates molecules as they tumble through a gas – their progress is related to their average rotational collision cross section, or CCS. This is what makes IMS so powerful, because CCS is determined by unique molecular properties.
CCS is an important distinguishing characteristic of an ion, related to its:
- chemical structure (mass, size)
- 3-dimensional conformation (shape), where conformation can be influenced by a number of factors, including the number and location of charges
CCS is a robust and precise matrix-independent physicochemical property of an ion which can provide many powerful analytical advantages.
You can read more in this poster about the Design and application of a CCS and MS/MS Metabolic Profiling Library.
What are the advantages of CCS? Why would researchers be interested in this technology?
- Ion Mobility Separation provides orthogonal separation for increased confidence in results; you can distinguish between co-eluting compounds of identical mass and elemental composition.
- False positives can be removed and false negatives avoided using CCS values as a screening parameter
- Mobility resolution facilitates spectral clean-up for both precursor and fragment spectra
- CCS improves identification where retention time or mass shifts have been observed
Yesterday, I was talking to two Waters chemists who had been trying out the new CCS library for the first time with a customer. Here’s what they had to say:
“…during a customer demo, we used the new CCS library to screen clinical research samples in metabolomics experiments with special interest in steroid profiling. The correct identifications and relative quantification of the steroids – which partly have same elemental composition – is the intention of this project for a better understanding of diseases like hypertension caused by primary aldosteronism. This was my first time using the new Metabolic Profiling CCS Library with real samples. The last few months I’ve heard a lot of discussion regarding comparability of CCS on different instruments and some of these statements were misleading as CCS is a physicochemical parameter and the CCS value must be independent from the platform of acquisition. Therefore I was very curious to see the outcome of the experiments and it was a very positive surprise to see the library entries and the measured CCS values gave fantastic matches with deviations better than expected. This is even more amazing because it is regardless of lab, instrument, operator and continent. These results give my customers and me great confidence in the added value of CCS for correct identifications during non-targeted research projects and especially here with complex matrices and steroids having same accurate mass…”
Gunnar Weibchen, PhD, Mass Spectrometry Sales Specialist in Germany
“I totally agree, it was excellent to see such good correlation in our results from a CCS database created in a different lab on different instruments by different users – this will be a major factor in helping us build customer confidence in the benefit of adding Ion Mobility measurements to our datasets and will help validate and standardise routine CCS analysis for our customers.”
Jonathan Fox, PhD, Principal Applications Chemist, European Applications Laboratory, Waters U.K. Limited
The determination of CCS values allows an extra measure of confidence for compound identification in Progenesis QI. Each ion’s CCS value can be compared against established values held in a supplementary database file – an additional properties file – as part of the identification process, and this increases the specificity of compound identification. As well as the new Waters Metabolic Profiling CCS Library, you can use an existing database of known CCS values or build one up based on empirical data from your own samples, for use in future experiments. Even if you don’t have ion mobility data, the MS/MS values in the library will be useful to you for identifications. We are looking to build libraries for people to share, so if you are interested in contributing please contact us.
So there you have it, another piece of corroborative evidence to help you identify your compounds with more confidence. The answer you are looking for could well be in the library .
To find out more about the Progenesis QI software and how it can alleviate your identification issues please get in touch.