Dataset Information

Retention Order Reversal of Phosphorylated and Unphosphorylated Peptides in Reversed-Phase LC/MS

ABSTRACT: Protein phosphorylation is one of the most ubiquitous post-translational modifications in human, and trypsin-digested phosphorylated peptides have been analyzed by reversed phase LC/MS using C18-silica columns under the acidic conditions to profile human phosphoproteomes. Here, we reported that phosphopeptides generally retain stronger than their unphosphorylated counterparts when C18-silica columns are used with acetic acid or formic acid as an ion-pairing reagent, whereas the retention order is reversed when less hydrophobic stationary phases such as C4-silica columns are used or more acidic and hydrophobic ion-pairing reagents such as trifluoroacetic acid are used with C18-silica columns. These phenomena could be explained by smaller S-values of phosphopeptides in linear solvation strength theory, based on the reduced net charge caused by intramolecular interaction between phosphate and basic groups.

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Yasushi Ishihama

PROVIDER: PXD010327 | JPOST Repository | Sun Nov 11 00:00:00 GMT 2018

REPOSITORIES: jPOST

ACCESS DATA

Dataset's files

Source:

			Action	DRS
	180314ko02NPS_phos_Fr1.wiff	Wiff
	180314ko02NPS_phos_Fr1.wiff.scan	Wiff
	180314ko03NPS_phos_Fr2.wiff	Wiff
	180314ko03NPS_phos_Fr2.wiff.scan	Wiff
	180314ko04NPS_phos_Fr3.wiff	Wiff

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Publications

Retention Order Reversal of Phosphorylated and Unphosphorylated Peptides in Reversed-Phase LC/MS.

Ogata Kosuke K Krokhin Oleg V OV Ishihama Yasushi Y

Analytical sciences : the international journal of the Japan Society for Analytical Chemistry 20180727 9

Protein phosphorylation is one of the most ubiquitous post-translational modifications in humans, and trypsin-digested phosphorylated peptides have been analyzed by reversed phase LC/MS using C18-silica columns under acidic conditions to profile human phosphoproteomes. Here, we report that phosphopeptides generally exhibit stronger retention than their unphosphorylated counterparts when C18-silica columns are used with acetic acid or formic acid as an ion-pairing reagent, whereas the retention o ...[more]

PMID: 30058604

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Project description:Proteome analyses of human induced pluripotent cells (iPSC) were carried out by liquid chromatography–tandem mass spectrometry systems using meter-scale monolithic silica-C18 capillary columns without pre-fractionation. Tryptic peptides from five different iPSC lysates and three different fibroblast cell (FBC) lysates (4 μg each) were directly injected onto a 200 cm long, 100 μm i.d. monolithicsilica-C18 column and an 8-h gradient was applied at 500 nL/min at less than 20 MPa. Consequently, 98,977 non-redundant tryptic peptides from 9,510 proteins (corresponding to 8,712 genes), including low abundant protein groups such as 329 protein kinases, were successfully identified from triplicate measurements within 10 days. The obtained proteome profiles of 8 cells were successfully categorized into two groups, iPSC and FBC, by hierarchical cluster analysis. Further quantitative analysis based on an exponentially-modified protein abundance index approach combined with UniProt keyword enrichment analysis reveals that the iPSC group contains more ‘transcription regulation’ proteins and the FBS group contains more ‘transport’ related proteins. This simplified “one-shot” proteomics approach with long monolithic columns enables to accomplish the rapid, deep, sensitive and reproducible proteome analysis. Sample pretreatment was carried out according to the PTS protocol with some modifications shown below. Proteins were extracted from the pellets with 12 mM SDC, 12 mM SLS, and 50 mM ammonium bicarbonate, reduced with 10 mM dithiothreitol at room temperature for 30 min; and alkylated with 55 mM iodoacetamide in the dark at room temperature for 30 min. The protein mixture was 5-fold diluted with 50 mM ammonium bicarbonate and Lys-C/trypsin digestion was performed. An equal volume of ethyl acetate was added to the eluent solution, and the mixture was acidified with 0.5% trifluoroacetic acid (final concentration). The mixture was shaken for 1 min and centrifuged at 15,700 x g for 2 min, and then the aqueous phase was collected. Tryptic peptides were desalted with reversed phase-StageTips. Raw data files were searched against the IPI human database v3.87 (91,464 sequences) using AB SCIEX ProteinPilot v4.0 with the set parameter of “Instrument: TripleTOF 5600”and “Digestion: trypsin”. A precursor mass tolerance of 0.05 Da and a fragment ion mass tolerance of 0.1 Da were employed. Carbamidomethylation of cysteine, oxidation of methionine, phosphorylation of serine, threonine and tyrosine, deamidation of asparagine, glutamine, N-terminal pyro-glutamic acid of glutamine or glutamic acid and protein N-terminal acetylation were only accepted, and peptides were rejected if the peptide confidence was below 95%, the delta mass was over 0.05 Da, the charge state was more than 5 and the number of missed cleavage was more than 2. For protein identification, peptides were grouped into ‘protein group’ based on the rules previously established. Then, at least two confidently identified peptides per protein were used for protein identification. In addition, single peptides with higher confidence (p<0.01) were allowed for protein identification.