Dear wise person,
I have recently conducted TMT proteomics of cultured cells.
I am unsure about how certain the detection is.
Do I understand it correct mass spec cannot distinguish between 2-hydroxypropionic acid (lactate) and 3-hydroxypropionic acid since they have the exact same molecular weight?
Also goes for differentiating e.g. omega- from beta-hydroxy fatty acids?
Chromatography will add to MS in this case for improved resolution. Isomers must be resolved by chromatography or ion mobility configuration for mass-based detection
Dear Staffan Holmqvist ,
It depends to a large degree on the equipment (GC-MS, LC-MS, LC-MS/MS) and techniques (electrospray ionization (ESI), matrix-assisted laser desorption (MALDI), use of TMS/trimethylsilyl derivative etc.) you have available, see for a nice overview:
Chace, D. H. (2001). Mass spectrometry in the clinical laboratory. Chemical reviews, 101(2), 445-478 (see enclosed file).
But in general, it is the fragmentation (and not so much the molecular mass of the compound) that gives the unique fingerprint. I found two examples of MS spectra of 2- and 3-hydroxypropanoic acid:
https://www.chemicalbook.com/SpectrumEN_503-66-2_13CNMR.htm
https://webbook.nist.gov/cgi/cbook.cgi?Spec=C50215&Index=0&Type=Mass&Large=on
Warning this is/might be an oversimplification (!) but I guess the main difference in both spectra might be explained by:
-Lactic acid (2-Hydroxypropanoic acid) where the predominant peak m=45 is mass of fragment minus COOH
-3-Hydroxypropanoic acid where the predominant peaks are 73 and 60. m=73 is mass of fragment minus OH and m=60 is mass of fragment minus CH2OH
So, the hopeful message is that it is/should be possible to distinguish between these types of substances, but you need assistance of a GC/LC-MS expert.
Best regards.
- Badges
- Science topic
- Similar topics
- Chemistry
- Biochemistry
- Biochemical Techniques
- Blotting Techniques
- Immunoblotting
- Dyes