de novo Peptide Sequencing

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Key Features:

  • Automated de novo peptide sequencing with high throughput
  • Accuracy at amino acid level
  • Combines complementary fragmentations
  • Supports CID, HCD, ETD/ECD, EThcD, UVPD
  • Integrates with database search

de novo Peptide Sequencing

PEAKS de novo peptide sequencing

In a tandem mass spectrometer, the peptide is fragmented along the peptide backbone and the resulting fragment ions are measured to produce the MS/MS spectrum. Depending on the fragmentation method used, different fragment ion types can be produced. de novo Peptide sequencing derives an amino acid sequence from a mass spectrum without the need of a sequence database. It is in contrast to another popular peptide identification approach – “database search”, which searches in a given database to find the largest peptide. De novo peptide sequencing is the only choice when the sequence database is not available. This makes PEAKS the preferred method for identifying novel peptides and proteins from unsequenced organisms.

Accuracy

PEAKS uses a comprehensive scoring system to provide accurate de novo peptide sequencing results. Unique to PEAKS is the Local Confidence Score – the likelihood of each amino acid assignment in a resultant peptide. The local confidence score extends the accuracy to the amino acid level. In the figure, TLCDEFKADEK is a confident sequence tag with significant fragment proof.

PEAKS - de novo peptide sequencing - local confidence scoring

Complementary Fragmentation

Utilization of Spectrum-Pairs: de novo sequencing using spectrum-pairs that are generated in different fragmentation modes (eg.ETD/HCD). Confident de novo sequence tags from each complementary spectrum are used to reconstruct a peptide sequence, which is optimized to both spectra.

PEAKS - de novo peptide sequencing - complementary ETC-CID

Individual Spectrum Sequencing (before)

PEAKS - de novo peptide sequencing - complementary ETC-CID combined

Complementary Spectra Sequencing (after)

Integrated with Database Search

Unique to PEAKS is the ability to combine de novo peptide sequencing results with those of a database search. De novo peptide sequences are aligned with protein database entries to provide additional information about PTMs, mutations, homologous peptides, and novel peptides.

PEAKS - de novo peptide sequencing coverage pane

From de novo Peptide Sequencing to Protein Sequencing

Protein sequences could be obtained from the de novo peptide sequences. The confident de novo peptide sequence tags, which have direct fragmentation ion proof, were assembled into protein sequences, See PEAKS AB Software.

de novo peptide Sequencing View

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