Hi David,

Thanks for the prompt response.
So what I am trying to do is to avoid decoy hit Blocking the possible true 
hit.

The way I perform the analysis is to search data against a FASTA file which 
has reversed sequences appended. Then during PeptideProphet analysis I 
specify the decoy prefix and in the end use the probabilities for 
target/decoy hits to estimate FDR. One potential problem for me is that if 
a spectrum happens to match a decoy as best hit, with a very high score 
let's say XCorr 2.0, and the second hit with Xcorr 1.9, which si actually 
the true hit, would be discarded after PeptideProphet analysis. 

If PeptideProphet takes only top hit, could I do two separate searches 
using target-FASTA and Decoy-FASTA and specify two input files in 
PeptideProphet? Any suggestions?


Thanks,
Chih-Chiang

On Tuesday, April 4, 2017 at 9:45:11 AM UTC-5, David Shteynberg wrote:
>
> No.  It uses the top hit only.  
>
> On Tue, Apr 4, 2017 at 7:34 AM, Chih-Chiang Tsou <[email protected] 
> <javascript:>> wrote:
>
>> Hi
>>
>> Is there any option in xinteract to tell PeptideProphet take topN hits 
>> for each spectrum for probability calculation?
>>
>> Thanks,
>> Chih-Chiang
>>
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