A well‐characterised peak identification list of MALDI MS profile peaks for human blood serum

Abstract

. AbstractMALDI MS profiling has attracted considerable interest from the clinical community as a potentially valuable alternative to other diagnostic and prognostic tools by analysing biomarkers from easily available body fluids such as blood serum. Despite the numerous reports on MALDI MS profiling of human serum there is only scarce information on the identity of the biomolecular species making up these profiles, particularly in the mass range of larger peptides. Here we provide a methodology for MALDI MS profiling peak identification and an extensive list of peak identities up to 10 kDa obtained from human blood serum. The list of identities obtained so far comprises more than 90 entries. In addition to peptides published in other lists, we have also identified high-molecular weight peptides with masses above 5 kDa. Some of the identifications were related to endogenous lipids. Amongst the peptide identifications various modifications such as phosphorylation were detected. The overlap with the few other peptide lists published so far was found to be limited and hence our list significantly extends the number of identified peptides commonly found in MALDI MS profiling of human blood serum. With the data from this study it is further shown that lists of endogenous serum peptides can only be useful for MALDI MS profiling if the peak identifications can be directly linked to the MALDI MS profiles. A list of identifications of MALDI MS profile peaks from human blood serum, compiled from published data and this work, is presented.

Mapping O‐glycosylation of apolipoprotein C‐III in MALDI‐FT‐ICR protein profiles

“…In the current study, we have used a new MALDI‐FT‐ICR method for profiling of large serum peptides and proteins in the mass range from 6000 to 15 300 Da with high sensitivity and high resolution. Based on the previously reported identifications in MALDI profiles, we focused on apolipoproteins that were observed in the current profiles, namely apolipoprotein C‐I (Apo‐CI), C‐II (Apo‐CII), and C‐III (Apo‐CIII), including its glycosylated isoforms . Apolipoproteins C (Apo‐Cs) are present in blood associated, at different degrees, with various lipoproteins particles .…”

“…In the first approach, long centrifugation times are often required, thus decreasing the throughput of the analysis. Apo‐Cs have been successfully extracted and profiled using a combination of SPE and MALDI‐TOF MS . In the present study, we perform magnetic bead (MB) based SPE of serum samples followed by the acquisition of ultrahigh resolution MALDI‐FT‐ICR profiles including Apo‐CI, Apo‐CII, and glycosylated Apo‐CIII isoforms.…”

Precision profiling and identification of human serum peptides using Fourier transform ion cyclotron resonance mass spectrometry

“…In the TOF profiles 24 peptides were selected for a detailed evaluation, whereas in the low‐mass and high‐mass FTICR profiles 36 and 21 peptides were used, respectively. The standard deviation of 48 mass measurements at 48 different spots was calculated for each of the considered peptides after internal calibration using known MALDI profile peptides . In the MALDI‐TOF profiles this standard deviation varied from 0.70 to 7.7 ppm, with an average of 3.0 ppm.…”

“…After a selection procedure based on the presence of calibrant peptides at a predefined S/N level 301 MALDI‐TOF and 314 MALDI‐FTICR spectra remained . The m/z ‐values in the profiles were compared to a previously reported list of ‘MALDI MS profile peaks’ . Six of these identified peptides were selected for internal calibration, with calculated m/z ‐values of monoisotopic peaks of protonated species at 1206.5749 (fibrinopeptide A (FPA) 5‐16, P02671), 1350.6284 (FPA 3‐16, P02671), 1616.6594 (FPA 1‐16 + P, P02671), 2021.1039 (complement C3f fragment, P01024), 2931.2915 (fibrinogen alpha (FGA) chain precursor 576‐601, P02671), and 3261.4641 (FGA chain precursor 576‐604, P02671).…”

Commentary on ‘Performance of ultrasound as a second line test to serum CA125 in ovarian cancer screening’

“…The systematic prospective collection of serum samples in asymptomatic women may result in the discovery of more relevant biomarkers of early disease than have been suggested by the comparison of samples from women with clinically detectable cancers with controls. Proteomic discovery studies aimed at identifying an at‐risk signature from the antecedent serum of women who subsequently developed ovarian cancer in UKCTOCS are underway …”