[kino]

I need it in my research.

If I'm using Dithiothreitol (DTT) and PEG, how should I do?

Thanks in advance.

[opsomath]

You can't do it with DTT. You need something else, assuming the end groups of your PEG are OH groups. Off the top of my head, if I had to do what you describe, I would react the PEG with something like tosyl chloride or PBr3 to make the OH into a leaving group, and then react the product with thiourea or sodium hydrosulfide.