Iam working on seaweed protein. After extraction of protein, i have precipitated with ammonium sulphate and freeze dried the sample after dialysis. In kjeldahl iam getting good percentage of protein but when iam performing lowry or biuretthe colour is not changing. I dissolved my powdered sample in water to perform this and it got completely dissolved. For cross-checking, i have performed DUMAS method also using protein analyzer. I that also iam getting good amount of protein. so what can be the reason for this and how to solve this?