Protein thiolation index in microvolumes of plasma.

Abstract Protein Thiolation Index (PTI) has been recently proposed as a new biomarker of oxidative stress. It is calculated by measuring both free thiols and S-thiolated proteins in plasma with the assumption that this redox ratio is altered by a pro-oxidant stimulus. Here the original protocol was modified and adapted to the use of microvolumes of blood collected by finger prick and down to 3 μl blood was shown to be the lowest volume suitable for this kind of analysis. The new procedure was used to evaluate both the circadian rhythm and the annual fluctuations of PTI in healthy humans.