Collagen Tipe I filtration - (Jul/09/2015 )

I extracted I collagen from tilapia skin , i have it in a acetic acid solution , before that i precipitated it with a NaCl solution, so i want to diafiltrate it and i want to know the right kDa acording to the molecular weight, any suggestion?  By now i have decided do it with 80 kDa

if you think that the molecular weight is 80 kDa then you may use a 10 kDa cutoff filter for diafiltration. that's good for a globular protein, may not be as good for a linear protein but should be mostly okay.