Formaldehyde,a well-known environmental toxic hazard,has been found to produce endogenously via semicarbazide-sensitive amine oxidase-catalyzed oxidative deamination of methylamine.In diabetes,the activity of SSAO has been found to increase with a subsequent increase in endogenous formalde-hyde production.It has been postulated that SSAO-induced production of formaldehyde may be in-volved in the alteration of protein structure,which may subsequently cause protein deposition associ-ated with chronic pathological disorders.Formaldehyde has also been found to react(cross-link) with amino group of the N-terminal amino acid residue and with the side-chains of arginine,cysteine,his-tidine and lysine residues.Therefore,formaldehyde may be responsible,at least in part,for protein cross-linkage,oxidative stress and cytotoxicity.The cross-linking of formaldehyde with bovine serum albumin was studied using LC-MS and Mascot database.The peptides sequence for control BSA(un-treated) digested with trypsin was matched in the online database search query by exporting the MS/MS data to online MASCOT database.In this way,a total of twenty-seven peptides were matched in the database search query.These twenty-seven peptides were then searched manually in all of the tryptic BSA samples treated with different concentrations of FA that were incubated in different time intervals.Six formaldehyde-treated BSA peptides(FKDLGEEHFK,HLVDEPQNLIK,KVPQVSTPTLVEVSR,RPCFSALTPDETYVPK,LVNELTEFAK,DAFLGSFLYEYSR) were found to be the possible markers for formaldehyde-protein/peptides adducts. Formaldehyde, a well-known environmental toxic hazard, has been found to produce endogenously via semicarbazide-sensitive amine oxidase-catalyzed oxidative deamination of methylamine. Diabetes, the activity of SSAO has been found to increase with a subsequent increase in endogenous formal de-hyde production. It has been postulated that SSAO-induced production of formaldehyde may be in-volved in the alteration of protein structure, which may subsequently cause protein deposition associ-ated with chronic pathological disorders. Normaldehyde has also been found to react (cross-link ) with amino group of the N-terminal amino acid residue and with the side-chains of arginine, cysteine, his-tidine and lysine residues. before, formaldehyde may be responsible, at least in part, for protein cross-linkage, oxidative stress and cytotoxicity. The cross-linking of formaldehyde with bovine serum albumin was studied using LC-MS and Mascot database. The peptides sequence for control BSA (un-treated) digested with t rypsin was matched in the online database search query by exporting the MS / MS data to online MASCOT database. In this way, a total of twenty-seven peptides were matched in the database search query. these twenty-seven peptides were then searched manually in all of the tryptic BSA samples treated with different concentrations of FA that were incubated in different time intervals.Six formaldehyde-treated BSA peptides (FKDLGEEHFK, HLVDEPQNLIK, KVPQVSTPTLVEVSR, RPCFSALTPDETYVPK, LVNELTEFAK, DAFLGSFLYEYSR) were found to be possible markers for formaldehyde-protein / peptides adducts.