Publications by authors named "J D Dufresne"
Naturally occurring peptides display a wide mass distribution after ionization due to the presence of heavy isotopes of C, H, N, O, and S and hydrogen loss. There is a crucial need for sensitive methods that collect as much information as possible about all plasma peptide forms. Statistical analysis of the delta mass distribution of peptide precursors from MS/MS spectra that were matched to 63,077 peptide sequences by X!TANDEM revealed Gaussian peaks representing heavy isotopes and hydrogen loss at integer delta mass values of -3, -2, -1, 0, +1, +2, +3, +4, and +5 Da.
View Article and Find Full Text PDFOrganic precipitation of proteins with acetonitrile demonstrated complete protein recovery and improved chromatography of human plasma proteins. The separation of 25 μL of human plasma into 22 fractions on a QA SAX resin facilitated more effective protein discovery despite the limited sample size. Micro chromatography of plasma proteins over quaternary amine (QA) strong anion exchange (SAX) resins performed best, followed by diethylaminoethyl (DEAE), heparin (HEP), carboxymethyl cellulose (CMC), and propyl sulfate (PS) resins.
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- The study examines changes in gap junction protein expression in the rat epididymis during postnatal development, revealing decreased levels of Gjb2 (Cx26) and increased levels of other connexins (Cx32, Cx30.3, and Cx31.1).
- The research aims to identify mechanisms behind these expression changes, indicating that decreased Gjb2 does not trigger compensatory mechanisms in principal cells and noting hormone interactions.
- Findings show that androgens, particularly testosterone, and glucocorticoids like dexamethasone significantly influence the expression of these connexins, with orchidectomy revealing hormonal influence on GJB2 and GJB1 levels in the epididymis.
Previous meta-analysis indicated that plasma or serum proteome groups using various experimental conditions detected different peptides from the same plasma proteins, which is strong evidence for the veracity of blood fluid LC-ESI-MS/MS but also evidences that the trypsin digestion step is a key source of variation in plasma proteomics. Agreement between different digestion conditions and MS/MS algorithms may serve as an independent confirmation of the validity of the LC-ESI-MS/MS analysis of plasma peptides. Plasma contains a high percentage of albumin held together by multiple disulfide bonds; hence, reduction and/or alkylation may greatly enhance the digestion efficiency of albumin.
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