MassIVE MSV000079841

Imported Reanalysis Dataset Public PXD001468

A mass-tolerant database search identifies a large proportion of unassigned spectra in shotgun proteomics as modified peptides

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Description

Less than half of all MS/MS spectra acquired in shotgun proteomics typically result in a confident peptide match. Here we present an ultra-tolerant Sequest database search that allowed peptide matching even with modifications of unknown masses up to ±500 Da. From an HEK293 cell proteome-wide dataset (9,513 proteins and 396,736 peptides), a ±500-Da search matched an additional 184,000 modified peptides. These were linked to both biological and chemical modifications representing 523 distinct ï??mass bins including phosphorylation, glycosylation, and methylation. We attempted to localize all unknown modification masses to specific regions within a peptide, and known modifications were accurately assigned to the correct amino acids with frequencies often >90%. These data demonstrate that a large fraction of previously unassignable spectra are assignable to peptide sequences with modifications. [dataset license: CC0 1.0 Universal (CC0 1.0)]

Keywords: Proteomics ; Sequest ; Large scale ; modifications

Contact

Principal Investigators:
(in alphabetical order) 		Dr Steven P Gygi
Submitting User: ccms

Publications

Chick JM, Kolippakkam D, Nusinow DP, Zhai B, Rad R, Huttlin EL, Gygi SP.
A mass-tolerant database search identifies a large proportion of unassigned spectra in shotgun proteomics as modified peptides.
Nat. Biotechnol. 2015 Jul;33(7):743-9. Epub 2015 Jun 15.

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Identification Results
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Number of distinct conditions across all analyses (original submission and reanalyses) associated with this dataset.

Distinct condition labels are counted across all files submitted in the "Metadata" category having a "Condition" column in this dataset.

"N/A" means no results of this type were submitted.
Number of distinct biological replicates across all analyses (original submission and reanalyses) associated with this dataset.

Distinct replicate labels are counted across all files submitted in the "Metadata" category having a "BioReplicate" or "Replicate" column in this dataset.

"N/A" means no results of this type were submitted.
Number of distinct technical replicates across all analyses (original submission and reanalyses) associated with this dataset.

The technical replicate count is defined as the maximum number of times any one distinct combination of condition and biological replicate was analyzed across all files submitted in the "Metadata" category. In the case of fractionated experiments, only the first fraction is considered.

"N/A" means no results of this type were submitted.
Originally identified proteins that were automatically remapped by MassIVE to proteins in the SwissProt human reference database.

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Number of distinct protein accessions reported across all analyses (original submission and reanalyses) associated with this dataset.

"N/A" means no results of this type were submitted.
Number of distinct unmodified peptide sequences reported across all analyses (original submission and reanalyses) associated with this dataset.

"N/A" means no results of this type were submitted.
Number of distinct peptide sequences (including modified variants or peptidoforms) reported across all analyses (original submission and reanalyses) associated with this dataset.

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Total number of peptide-spectrum matches (i.e. spectrum identifications) reported across all analyses (original submission and reanalyses) associated with this dataset.

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Number of distinct proteins quantified across all analyses (original submission and reanalyses) associated with this dataset.

Distinct protein accessions are counted across all files submitted in the "Statistical Analysis of Quantified Analytes" category having a "Protein" column in this dataset.

"N/A" means no results of this type were submitted.
Number of distinct proteins found to be differentially abundant in at least one comparison across all analyses (original submission and reanalyses) associated with this dataset.

A protein is differentially abundant if its change in abundance across conditions is found to be statistically significant with an adjusted p-value <= 0.05 and lists no issues associated with statistical tests for differential abundance.

Distinct protein accessions are counted across all files submitted in the "Statistical Analysis of Quantified Analytes" category having a "Protein" column in this dataset.

"N/A" means no results of this type were submitted.
This dataset may not contain all raw spectra data as originally deposited in PRIDE. It has been imported to MassIVE for reanalysis purposes, so its spectra data here may consist solely of processed peak lists suitable for reanalysis with most software.