Definition of the "Isolation Width"?

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MSENC
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Definition of the "Isolation Width"?

Postby MSENC » Fri Jan 27, 2012 2:27 pm

Sorry for a rather simple, yet ambiguous question: When you enter a value prior to the data acquisition, is it the full-width or half-width. In other word, does a 2 Da isolation window mean "plus/minus 2 da around my precursor" or "plus/minus 1 da around my precursor".

I couldn't find the exact answer anywhere unfortunately.

Wen

Craig
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Postby Craig » Fri Jan 27, 2012 3:08 pm

Hi Wen,

As far as I am aware, "isolation width" always refers to the full width. So a 2 Da isolation window means +/- 1 Da.

-Craig

Infinity
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Postby Infinity » Sat Jan 28, 2012 7:59 am

I agree with Craig, -/+ 1Da centered at your precursor.

MSENC
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Postby MSENC » Sat Jan 28, 2012 8:46 am

I took a closer look at some data and both of you are right.

Mann published a paper about "100,000 peptide species" in a single HeLa run. They released two Lc-MS/MS with 2 and 16Da isolation respectively. If I took MS/MS from 2Da run and calculate dot-product to MS/MS in 16 Da within the same RT vicinity, the graph would offer an actual picture of what happened due the precursor isolation.

1-27-2012 9-35-16 PM.jpg


Thanks!

Wen
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karthikskamath
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Postby karthikskamath » Sun Jan 29, 2012 8:11 pm

Yes Wen
As Craig n Infinity indicated it is +/- value. BTW could you please share this paper here? I am bit confused with another paper "Deep proteome and transcriptome mapping of a human cancer cell line". This figure really drives some interest. Thanks !!!

Karthik

MSENC
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Postby MSENC » Mon Jan 30, 2012 8:04 am

The paper was published in JPR last year:
"More than 100,000 Detectable Peptide Species Elute in Single Shotgun Proteomics Runs but the Majority is Inaccessible to Data-Dependent LC−MS/MS", http://pubs.acs.org/doi/abs/10.1021/pr101060v.

The conclusion of the paper is not surprising at all. It's consistent with our own observation based on the feature detected by Elucidator as well.

karthikskamath
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Postby karthikskamath » Mon Jan 30, 2012 10:52 pm

Hi Wen

Many thanks for sharing this paper.

Karthik


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