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Digitale Medien

Crystallization and initial spectroscopic characterization of the heme-containing dehaloperoxidase from the marine polychaete Amphitrite ornata (1996)

Zhang, E. ; Chen, Y. P. ; Roach, M. P. ; [weitere]

Copenhagen : International Union of Crystallography (IUCr)

Acta crystallographica 52 (1996), S. 1191-1193

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ISSN: 1399-0047

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Notizen: The heme-containing dehaloperoxidase from Amphitrite ornata was crystallized from an unbuffered solution containing 30% PEG 8000 and 200 mM ammonium sulfate by the hanging-drop vapor-diffusion method. Dark-red bipyramidal crystals are orthorhombic in space group P212121 with unit-cell dimensions a = 68.5, b = 68.4 and c = 61.1 Å. The asymmetric unit contains two subunits related by a non-crystallographic twofold axis. The crystals scatter beyond 2 Å resolution. The native data have been collected and one single-site mercury derivative has been found. SIRAS phasing was used to determine the positions of the heme Fe atoms and structure determination is in progress. A preliminary spectroscopic investigation indicates that the heme is protoporphyrin IX and its coordination sphere resembles that of a typical heme peroxidase, i.e. histidine ligated. Detailed spectroscopic and electrochemical studies are now under way.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0907444996007974

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Digitale Medien

A concordance of nucleotide substitutions in the first and second hypervariable segments of the human mtDNA control region (1996)

Miller, K. W. P. ; Hagelberg, E. ; Dawson, J. L.

Springer

International journal of legal medicine 109 (1996), S. 107-113

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ISSN: 1437-1596

Schlagwort(e): Human populations ; Mitochondrial DNA ; DNA sequencing ; Population genetics ; Anthropology

Quelle: Springer Online Journal Archives 1860-2000

Thema: Medizin , Rechtswissenschaft

Notizen: Abstract A new and easily accessible concordance of nucleotide substitutions in the hypervariable segments of the human mitochondrial DNA (mtDNA) control region has been constructed. The concordance indexes all population-specific mtDNA sequences in a standardized format. The first edition of the concordance includes 1,440 sequences representing 762 mtDNA types from over 65 populations for hypervariable region 1, and 520 sequences representing 260 mtDNA types from over 26 populations for hypervariable region 2. Investigators are invited to submit new sequences to the database, and details for doing so are given in the text.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01369668

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Digitale Medien

Indirect crustal contamination: evidence from isotopic and chemical disequilibria in minerals from alkali basalts and nephelinites from northern Tanzania (1996)

Paslick, C. R. ; Halliday, Alex N. ; Lange, R. A. ; [weitere]

Springer

Contributions to mineralogy and petrology 125 (1996), S. 277-292

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ISSN: 1432-0967

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie

Notizen: Abstract Alkali basalts and nephelinites from the volcanic province of northern Tanzania contain pyroxene and nepheline that show evidence for chemical and/or isotopic disequilibria with their host magmas. Olivine, pyroxene, nepheline and plagioclase all appear to be partially xenocrystic in origin. Five whole rock/mineral separate pairs have been analyzed for Sr, Nd, and Pb isotopic compositions. The 206Pb/204Pb ratios are distinct by as much as 20.94 (whole rock) vs. 19.10 (clinopyroxene separate). The Sr and Nd isotopic disequilibria vary from insignificant in the case of nepheline, to Δ 87Sr/86Sr of 0.0002 and ΔɛNd of 0.7 in the case of clinopyroxene. The mineral chemistry of 25 samples indicates the ubiquitous presence of minerals that did not crystallize from a liquid represented by the host rock. The northern Tanzanian magmas are peralkaline and exhibit none of the xenocrystic phases expected from crustal assimilation. The disequilibria cannot be the result of mantle source variations. Rather the xenocrystic phases present appear to have been derived from earlier alkali basaltic rocks or magmas that were contaminated by the crust. Material from this earlier magma was then mixed with batches of magma that subsequently erupted on the surface. Disequilibrium in volcanic rocks has potentially serious consequences for the use of whole rock data to identify source reservoirs. However, mass balance calculations reveal that the 206Pb/204Pb isotopic compositions of the erupted lavas were changed by less than 0.25% as a result of this indirect crustal contamination.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s004100050222

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