OBJECTIVE: In this study the mechanism of interactions between polyamidoamine (PAMAM) dendrimers and bovine insulin was examined. The insulin is a 51 amino acid peptide-hormone involved in the homeostasis of blood glucose levels. This molecule consists of two chains - A and B - linked by two disulphide bridges. As insulin contains four tyrosine residues it was possible to evaluate dendrimers effect on protein conformation by measuring changes in the fluorescence spectra of insulin after addition of dendrimers or classical quenchers.
METHODS: PAMAM dendrimers are based on ethylenediamine core and branched units which are built from methyl acrylate and ethylenediamine. PAMAM dendrimers with different surface groups (-COOH, -NH2, -OH) were used. Their size is comparable to insulin.
RESULTS: The experiments show that interactions exist between PAMAM dendrimers and insulin. It was found that these interactions depend on a kind of dendrimer surface groups.
CONCLUSIONS: It is very likely that interactions are of electrostatic nature and cause insulin conformational changes....