ESI-MS is an effective way to study intermolecular interaction. In this paper

the non-covalent interaction between a series of synthesized N-phosphoryl dopamine and insulin was studied by using ESI-MS. The effects of different groups of P on N-phosphoryl dopamine were compared. The results showed that length and sequence of alkyl group of alkoxyl group on P were very important for the interaction under ESI-MS conditions. N-phosphoryl dopamines with longer carbon chains could contract the protein configuration more greatly and form complex with higher stoichiometric proportion in solution

while the sequence of carbon chain with a same number carbon atom have no obvious difference on contraction of protein. The result also showed that the length of carbon chain also had an obvious effect on the stability of complexes. Straight chain was more beneficial for the stability than branched chain when the number of carbon was equal. This conclusion was valuable for design of new active dopamine molecules.