Abstract
The interaction between metals and protein is considered as a scientific challenge. Some metals like Cr could interact with natural protein for scientific purposes; the mechanism of interaction is a key role in controlling this interaction. This work presents the interaction of Cr in different oxidation states with alanine trimmer. Possible interaction with NH2; COOH as terminal and NH2 as side chain is presented. The data is discussed in terms of the calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). It is concluded that the active site of interaction depends not only on the type of amid but also on the oxidation state of the metal as well.