ES-MSElectro Spray Mass Spectroscopy
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ES-MS; (m/z): [M+H]+ 423.1 (27), [M+H-CH3]+ 408.1 (100), [M-C11H13N3O]+ 220.1 (34), [M- C6H5SO2Br]+ 202.1 (39).
The most downfield peak at [delta] 138.8 of one carbon was assigned to the carbon alpha to -[CH.sub.2]OH group (C-3) and the most high-field quaternary signal at [delta] 131.5 was due to the C-47 carbon bearieans of es-ms, ng two terminal methyls.
Although technologies such as Boronate affinity chromatography and ES-MS provide a means of accurately determining gHb in these individuals, results are unlikely to accurately reflect long-term glycemic control due to pathological conditions that affect the formation and turnover of gHb in vivo.
[1] Nonstandard abbreviations: gHb, glycohemoglobin; Hb, hemoglobin; GSP, glycated serum protein; GSA, glycated serum albumin; IEF, isoelectric focusing; and ES-MS, electrospray mass spectrometry.
Here we describe an investigation into the potential of ES-MS for quantifying GHb.
A working solvent of equal volumes of water and acetonitrile acidified with 2 mL/L formic acid was generally used for preparing samples for the ES-MS analysis of peptides and proteins and serves to denature the protein.
On the basis of these assumptions and the knowledge that the ES-MS analyte originates from whole-blood hemoglobin that contains equal molar amounts of [alpha]- and non-[alpha]-chain species, it can be rigorously shown that
Nevertheless, the close correlation between the ES-MS results and the results obtained with other techniques imply that the assumptions are not widely divergent from reality.
This result indicates that using diluted whole blood without further purification to remove alkali metal salts is adequate for determining GHb by ES-MS. It further suggests that the assumptions made regarding alkali metal adducts in calculating %GHb are reasonable.
No evidence for multiple glycation was observed even at the highest value analyzed for GHb (15%, as determined by ES-MS).
The imprecision (CV) of the ES-MS measurements was determined by performing 10 replicate analyses on five separate samples.
A comparison of GHb determined by ES-MS with GHb determinations by other established methods is presented graphically in Fig.