title: Solution structure of physiological Cu(His)2: novel considerations into imidazole coordination.
abstract: A disagreement on the mode of histidine binding to copper and the structure of [Cu(2+)(His)(2)] in solution still exists. Spectroscopic data in solution support a six-coordinate species with N4O2 donor atoms, while X-ray crystallography reveals five-coordinate N(3)O(2) donor atoms. We modified [Cu(2+)(His)(2)] in solution using diethyl pyrocarbonate (DEPC) and monitored the products spectrophotometrically and by mass spectrometry. Our spectrophotometric study indicates the presence of a free imidazole in the [Cu(2+)(His)(2)] complex in solution. Mass spectral characterization of a DEPC-modified [Cu(2+)(His)(2)] complex yielded a peak at 587.8 amu corresponding to three DEPC adducts. Taken together, our data indicate that the [Cu(2+)(His)(2)] complex in solution exists as a neutral five-coordinate structure with N3O2 donor atoms.
authors.affiliation: Biometry and Nutrition Group, Animal Sciences Division, Agharkar Research Institute, Pune 411 004, India.
authors.forename: Yamini P
authors.initials: YP
authors.lastname: Ginotra
authors.forename: Prasad P
authors.initials: PP
authors.lastname: Kulkarni
mesh_terms: D018360:Crystallography, X-Ray; D004047:Diethyl Pyrocarbonate / Q000737:chemistry; D006639:Histidine / Q000737:chemistry* / Q000502:physiology; D007093:Imidazoles / Q000737:chemistry*; D013058:Mass Spectrometry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D009942:Organometallic Compounds; C045576:copper bis(histidinate); D006639:Histidine; C029899:imidazole; D004047:Diethyl Pyrocarbonate