Retention time as an extra dimension for proteome-wide cross-link identification

Chemical crosslinking methods have not been successfully applied to protein-protein interaction discovery mainly due to the computation complexity (O (n2)) issue. In a previous report, we proposed a decision tree searching strategy which can reduce complexity by orders of magnitude. In this study, we found that the mono-linked peptides carry out the information of the retention time of the cross-linked pairs, therefore the retention time of cross-linked peptide pairs can be predicted accurately. By utilizing the obtained retention time information, the false positive rate can be reduced by around 86% with a sensitivity loss of 12%. The method was successfully applied to the identification of inter cross-links obtained from E. coli cell lysate crosslinked by a newly synthesized enrichable crosslinker.