Phosphorylated peptides, selective

Martin R. Larse N,Tine E, et al. Highly selective enrichment of phosphorylated peptides from peptide mixtures using titanium dioxide microcolumns. Molec. Cell. Proteomics (2005) 4 873-886. 

In terms of ionization, the majority of large-scale phosphoproteomics strategies utilize ESI. The difficulty to effectively analyze phosphopeptides by ESI-based approaches is often attributed, among other factors, to selective suppression of phosphorylated peptides in the presence of unmodified peptides, and fo decreased ionization efficiencies of phosphopeptides relative to their non-phosphorylated counterparts. However, this notion has been challenged in a recent study (18) underscoring the... 

Thinghokn TE, Jprgensen TJ, Jensen ON, Larsen MR. Highly selective enrichment of phosphorylated peptides using titanium dioxide. Nat Protoc. 2006 1 1929-1935. 

Our initial applications of the stepped collision energy LC-ESMS approach involved selective detection (and differentiation) of N- or O-glycosylated peptides (5,6), and detection of phosphorylated peptides (7,8,11). The method has been in routine use in our laboratory for over two years and during this time has become one of the mainstays of our work in characterizing protein modifications. Here we present some of our more recent studies on protein glycosylation and phosphorylation, and illustrate a preliminary evaluation of the stepped collision energy LC-ESMS method for selective detection of sulfated and acylated peptides in protein digests. 

The significant emission enhancement of these chemosensors and the high selectivity towards phosphorylated peptides enabled the detection of phosphorylated peptides by naked inspection of the emission change. This is illustrated in the photograph shown in Fig. 5. Such fluorescence intensification of the chemosensors is clearly ascribed to the phosphate-assisted binding of the second Zn cation. A schematic illustration of the sensing mechanism toward the phosphorylated peptide is depicted in Scheme 11. In the absence of a phosphorylated peptide, the second Dpa site of the chemosensor is... 

Results widi the ten chosen scFvs are shown in Figiue 3A. ScFvs selected with phosphorylated peptide were highly specific for phosphorylated peptide over nonphosphorylated peptide (D5, DIO, D12, E6, E9, FI, H7). ScFvs... 

Jalili, P.R. Ball, H.L. Novel reversible biotinylated probe for the selective enrichment of phosphorylated peptides from complex mixtures. J. Am. Soc. Mass Spectrom. 2008,19, 741-750. 

Figure 4.4. Precursor-ion scan of miz 79 for selective detection of phosphopeptides. Two tyrosine phosphorylated peptides (1303.2 and 1686.7 Da) are detected in an LC fraction. (Reproduced from ref. 5 by permission of the American Chemical Society, Washington, DC, copyright 1993.)...

The VACM-1 receptor is a membrane-associated protein with a single putative transmembrane domain that binds selectively AVP (XD — 2 nM), but cannot discriminate between VXR and V2R analogues. It is expressed in endothelial and medullary collecting duct cells and upon stimulation by AVP. It induces a mobilization of cytosolic-free Ca2+, decreases cAMP production and inhibits cellular growth via MAPK phosphorylation and p53 expression. The mechanism of action and physiological functions of this new receptor are not well understood, but it seems to participate in the regulation of AVP induced signal transduction pathways or of a yet unidentified peptide. 

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