1. The problem statement, all variables and given/known data I just purified alkaline phosphatase, and my calculated molecular weight is 100000 g/mol, while literature value is 89000 g/mol. According to how others in my lab did calculations, my calculations are performed correctly, so I am left to explain why my purification is higher than expected. 2. Relevant equations N/A 3. The attempt at a solution I was thinking that since alkaline phosphatase can be inhibited by EDTA, my "purified" enzyme contains some EDTA, making the molecular weight higher.