The cysteine-specific redox-sensitivity of proteins can shed light on how ROS are regulated and function, but low sensitivity has limited quantification of the redox state of many fundamental cellular regulators in a cellular context. A highly sensitive and reproducible oxidation analysis approach (OxMRM) that combines protein purification, differential alkylation with stable isotopes, and multiple reaction monitoring mass spectrometry  can be applied in a targeted manner to virtually any cysteine or protein. Using this approach, we quantified the site-specific cysteine oxidation status of endogenous p53 for the first time and found that Cys182 at the dimerization interface of the DNA binding domain is particularly susceptible to diamide oxidation intracellularly. OxMRM enables analysis of sulfinic and sulfonic acid oxidation levels, which we validate by assessing the oxidation of the catalytic Cys215 of protein tyrosine phosphatase-1B under numerous oxidant conditions.

 reduction with TCEP before using, any more question ? [email protected] , China

Thanks for everyone respond.  My adviser asked me to use multi cystin peptid when it is not oxidized.  Before, he asked me to order this peptide without oxidation.  Right now,he ask me to do the reduction by DDT and then remove the DDT by using Zip tap technique and then do the experiment immediately. Is DDT better or TCEP for reduction? Can anyone explain to me more about the process? Thank you

TCPE AND DTT BOTH CAN REDUCTION CYSTIN PEPTIDE, I think TCEP works better than DTT ,you can review the paper [Biochemistry. 2004 Dec 7;43(48):15195-203]  ，

 Zip tap technique  ，do you mean purificaiton ZipTip® Pipette Tips? commercial available!

Thanks for your help. Yes. I mean Zip Tip purification method.