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Correlations of electronic spectra and molecular structures of blue copper proteins
196
Journal of Inorganic Biochemistry 96 (2003)
Correlations of Electronic Spectra and Molecular Structures of Blue Copper Proteins Vera Miiller, Universitdt Heidelberg, Germany Peter Comba, Universitiit Heidelberg, Germany Rainer Remenyi, Universitlit Heidelberg, Germany Blue Copper Proteins are known for their fast and efficient long range electron transfer in plants and bacteria. Characteristic properties of cupredoxines are an intense blue colour (absorption at -600 nm, 2000-6000 l/(M*cm), arising from S(Cys)Cu(I1) charge transfer, and high redox potentials (approx. 180-680 mV). These properties depend to a large extent from the structure of the chromophore and the difference between various speciesmust be due to subtle structural changes. Therefore, it is of interest to correlate structural parameters with electronic properties. This might be possible by the computation of electronic properties from structural parameters and vice versa. Accurate spectroscopic data might also be used to validate experimental and computed structural data. Excited state properties were calculated with DFT (Gausssian 98) and AOM (CAMMAG) methods and compared with experimental electronic spectra.
Chromium(II1)
Complexes Used as Nutritional Structures and Reactivities
Supplements:
Irma Mulvani, School of Chemistry, University of Sydney,Australia Aviva Levina, School of Chemistry, University of Sydney,Australia Peter A Lay, School of Chemistry, Univekity of Sydney,Australia Chromium(II1) is considered by most nutritionists as an essential trace element for humans, enhancing the activity of insulin in glucose and fat metabolism [I]. It is suggested that more than 90% of population in developed countries do not obtain enough Cr(II1) with food, which led to a widespread use of Cr(III)-containing nutritional supplements, particularly Cr(II1) picolinate (I) [I J. Due to the concerns about safety of Cr(III) picolinate, a new supplement, Cr(III) propionate (II) has been recently proposed [I]. The mechanism of biological action of Cr(II1) complexes remains unclear, and no well-defined Cr(III)containing biomolecules has been characterised as yet [2]. In this work, structures and reactivities of I, II, and other Cr(II1) complexes have been studied under biologically relevant conditions. Decompositions of the complexes in neutral aqueous solution and in artificial gastric juice have been studied by UV-visible spectroscopy, electrospray mass spectroscopy, and X-ray "\ " 1' lo absorption spectroscopy. The developed methods will be applied to the studies \$ -1 cp+ w, I:> 4//OH2 of the speciation of Cr(II1) complexes in commercial nutritional supplements. 0 b.,,?cr’.” o cr, ,?\ ==J .s For the first time, the ability of enzymatic systems (such as glucose + glucose J& ‘i ,,, bqE* oxidase +O,) to oxidise Cr(II1) to Cr(V1) in aqueous solutions at pH -7 have been E, .+-+ “‘E, c&-j0% established. The Cr(III) (II) + glucose + glucose oxidase system causesextensive I oxidative damage of DNA in vitro. This finding raises concerns about the safety II of the use of II as a nutritional supplement. Acknowledgment. Financial support of this work was provided by ARC and ASRP grants. References [l] Vincent, J. B. Polyhedron 2001,20, 1-26 [2] Levina, A.; Cood, R.; Dillon, C. T; Lay, P. A. Progr. Inorg.Chem. 2003,51, 145-250.
Journal of Inorganic Biochemistry 96 (2003)
Correlations of Electronic Spectra and Molecular Structures of Blue Copper Proteins Vera Miiller, Universitdt Heidelberg, Germany Peter Comba, Universitiit Heidelberg, Germany Rainer Remenyi, Universitlit Heidelberg, Germany Blue Copper Proteins are known for their fast and efficient long range electron transfer in plants and bacteria. Characteristic properties of cupredoxines are an intense blue colour (absorption at -600 nm, 2000-6000 l/(M*cm), arising from S(Cys)Cu(I1) charge transfer, and high redox potentials (approx. 180-680 mV). These properties depend to a large extent from the structure of the chromophore and the difference between various speciesmust be due to subtle structural changes. Therefore, it is of interest to correlate structural parameters with electronic properties. This might be possible by the computation of electronic properties from structural parameters and vice versa. Accurate spectroscopic data might also be used to validate experimental and computed structural data. Excited state properties were calculated with DFT (Gausssian 98) and AOM (CAMMAG) methods and compared with experimental electronic spectra.
Chromium(II1)
Complexes Used as Nutritional Structures and Reactivities
Supplements:
Irma Mulvani, School of Chemistry, University of Sydney,Australia Aviva Levina, School of Chemistry, University of Sydney,Australia Peter A Lay, School of Chemistry, Univekity of Sydney,Australia Chromium(II1) is considered by most nutritionists as an essential trace element for humans, enhancing the activity of insulin in glucose and fat metabolism [I]. It is suggested that more than 90% of population in developed countries do not obtain enough Cr(II1) with food, which led to a widespread use of Cr(III)-containing nutritional supplements, particularly Cr(II1) picolinate (I) [I J. Due to the concerns about safety of Cr(III) picolinate, a new supplement, Cr(III) propionate (II) has been recently proposed [I]. The mechanism of biological action of Cr(II1) complexes remains unclear, and no well-defined Cr(III)containing biomolecules has been characterised as yet [2]. In this work, structures and reactivities of I, II, and other Cr(II1) complexes have been studied under biologically relevant conditions. Decompositions of the complexes in neutral aqueous solution and in artificial gastric juice have been studied by UV-visible spectroscopy, electrospray mass spectroscopy, and X-ray "\ " 1' lo absorption spectroscopy. The developed methods will be applied to the studies \$ -1 cp+ w, I:> 4//OH2 of the speciation of Cr(II1) complexes in commercial nutritional supplements. 0 b.,,?cr’.” o cr, ,?\ ==J .s For the first time, the ability of enzymatic systems (such as glucose + glucose J& ‘i ,,, bqE* oxidase +O,) to oxidise Cr(II1) to Cr(V1) in aqueous solutions at pH -7 have been E, .+-+ “‘E, c&-j0% established. The Cr(III) (II) + glucose + glucose oxidase system causesextensive I oxidative damage of DNA in vitro. This finding raises concerns about the safety II of the use of II as a nutritional supplement. Acknowledgment. Financial support of this work was provided by ARC and ASRP grants. References [l] Vincent, J. B. Polyhedron 2001,20, 1-26 [2] Levina, A.; Cood, R.; Dillon, C. T; Lay, P. A. Progr. Inorg.Chem. 2003,51, 145-250.