regarding precursor ion mass difference in novor vs pepnovo+

[Bhanu Ramanand]

hi,
I am using denovo gui ver 1.7.8. i have analyzed raw file from q exactive . i am doing mutation assignment work. for the same psm, precusor ion mass displayed against pepnovo+ is generally 0.5/0.3 dalton different ((higher) than novor for +2/+3 charges respectively. for example a denovo peptide identified by pepnovo+ "LEQDHYNTYLSK" has precursor mass as 504.24 with +3 charge state, same peptide with novor has a precursor mass of 503.91. how can same peptide spectrum have two precursor ion weights? please help me differentiate as there is scope mutation with 1Da mass shifts.
Regards
Bhanu

[Harald Barsnes]

 

Hi Bhanu,

 

Thanks for telling us about this. It turns out that there was a minor error in the way we calculated the precursor mass for the Novor results. The peptide in question should have a mass of 504.24, i.e., the mass given for PepNovo+ is the correct one.

 

The bug has now been fixed and DeNovoGUI v1.8.2 released. Please let us know if this is not the case.

 

Note that the error had no impact on the analysis, it was only a problem when displaying the precursor mass in the results table.

 

Best regards,

Harald

 

 

PS: For future issues, please use the DeNovoGUI issue tracker (https://github.com/compomics/denovogui/issues) for similar questions, as this makes it much easier for us to keep track of them.