Hello eveyone,

I'm trying to conjugate azide-MMAE compound to a protein. The azide-containg group is soluble in DMSO. The problem is when i combine all the ingridients for the reaction i get precipitation and only the protein remains (checked in MS analysis). My theory is that the amount of DMSO is so little in the total amount of the reaction that the organic compound is not soluble anymore. How do i prevent the precipitation of azide-MMAE, while also not denaturing the protein?

My reaction is as follows (for 1 ml, 37C, 550 rpm, 2hr):

50 ul of 50mM THPTA

25 ul of 20mM CuSO4

160 ul of 31.195uM protein

20 ul of 5mM azide-MMAE (stock is 50mM and diluted with PBS)

50 ul of 100mM ascorbic acid

and PBS to 1 ml

I would appreciate any assistance on this matter.