B. Lukas
University of Essex
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Featured researches published by B. Lukas.
Inorganica Chimica Acta | 1983
Jack Silver; B. Lukas
Abstract Mossbauer spectroscopic studies on frozen solutions of protoporphyrin IX iron(II) in the pH range 7–14 reveal evidence for three different species. The species dominant over the pH range 7–13 is a polymeric species (A) made up of a bare protoporphyrin IX iron(II) moieties, the number of moieties in the polymer is discussed relative to concentration and pH. This species is assigned an S = 1 spin state. Above pH 13 a high spin iron(II) species (C) is present. The quadrupole splitting associated with this species is discussed and is the largest yet reported for an iron(II) propoporphyrin. This species (C) is a five coordinate protoporphyrin IX iron(II) with a hydroxide ion as the fifth ligand. The third species (B) is a minor constituent of this system and also has a high spin iron(II) structure, though the Mossbauer parameters for this site are more in keeping with a distorted octahedral environment.
Inorganica Chimica Acta | 1984
Jack Silver; B. Lukas; Golzar Al-Jaff
Abstract Mossbauer parameters are presented for a number of protoporphyrin IX iron(II) complexes containing ligands that allow the iron to be in a five coordinate high spin iron(II) electronic environment. Such environments are characterised by large quadrupole splittings in the range 4.0 to 4.4 mm s −1 . These compounds have characteristic electronic spectra. The implications of catechol type ligands binding protoporphyrin IX iron II/III moieties are discussed.
Inorganica Chimica Acta | 1983
B. Lukas; Jack Silver; Ian E.G. Morrison; P.W.C. Barnard
Abstract Metalprotoporphyriniron(III) complexes are presented for the metal ions Al(III), Ba(III), Cd(II), Ca(II), Cr(III), Co(II), Fe(III), Mn(II), Ni(II), Pb(II), Ag(I), and Zn(II). These are distinct new species by comparison with similar Cu(II)protoporphyriniron(III) complexes. Infrared spectroscopy provides evidence for the metal binding to protoporphyrin propionate groups. Mossbauer data and magnetic susceptibility data are reported for the complexes. There is evidence for interactions between the two metal nuclei.
Inorganica Chimica Acta | 1984
Jack Silver; B. Lukas
Abstract A number of sulphur ligands in solution with protoporphyrin IX iron(II) give Mossbauer data similar to that recorded for cytochromes P-450 in the deoxy-high-spin ferrous stage. Addition of carbonyl to the solution results in Mossbauer spectra that have wider quadrupole splittings than that of P-450 CO. This suggest that the sulphur to iron bond in the cytochromes P-450 is unusually strong, probably due to other bonding forces in these proteins.
Inorganica Chimica Acta | 1983
B. Lukas; Jim Peterson; Jack Silver; Michael T. Wilson
Abstract Conductometric evidence is reported that shows an interaction between alkali metals with protoporphyrin IXiron(III) in aqueous solutions. Mossbauer spectroscopic and pH titration data are also reported. The results are explained in terms of the alkali metals binding to the propionate groups of the protoporphyrin IXiron(III) moieties.
Journal of The Chemical Society-dalton Transactions | 1982
B. Lukas; John R. Miller; Jack Silver; Michael T. Wilson; Ian E. G. Morrison
Methods for preparing copper–protoporphyrin–iron(III) complexes are presented. Comparison of the properties of these complexes with haematin and µ-oxo-dimeric haematin clearly shows that the complexes are distinct new species. Infrared spectroscopy provides evidence for the copper binding to protoporphyrin propionate groups. Mossbauer and e.s.r. spectroscopy provide evidence for high-spin iron(III) and copper(II). There is some evidence for interactions between the two metal nuclei. A possible structure is presented and its properties are discussed in terms of the known behaviour of cytochrome c oxidase.
Inorganica Chimica Acta | 1985
Jack Silver; B. Lukas
Abstract Solutions containing only protoporphyrin IX iron(III) and glutathione (the latter in 100-fold excess) show no evidence for the reduction of the iron(III) when examined using Mossbauer spectroscopy and electronic absorption spectra. This result is discussed in the light of known iron/glutathione chemistry, and iron/protoporphyrin IX chemistry. If carbon monoxide is passed into a solution of protoporphyrin IX iron(III) containing pyridine and glutathione (in excess) for twenty minutes evidence for a characteristic absorption band at 445 nm like that typical for cytochrome P450 is confirmed. This observation is discussed.
Inorganica Chimica Acta | 1986
B. Lukas; Jack Silver
Abstract The Mossbauer and other spectral data of a dicyanoprotoporphyrin IX iron(III) complex are reported. The low quadrupole splitting is discussed in relation to known low-spin iron(III) porphyrin structures and their Mossbauer parameters.
Inorganica Chimica Acta | 1985
B. Lukas; Jack Silver
Abstract Mossbauer parameters of frozen solutions of protoporphyrin IX iron(II) (containing either 2- methyl-piperidine or mercaptoethanol as the fifth iron ligand) that were exposed to oxygen before freezing are similar to those of oxyhaemoglobin. These results are discussed in relation to known porphyrin iron(II) chemistry.
Inorganica Chimica Acta | 1984
Jack Silver; B. Lukas; J. Al Taies