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Digitale Medien

A classification scheme for epigenetic Archaean lode-gold deposits (1995)

Gebre-Mariam, M. ; Hagemann, S. G. ; Groves, D. I.

Springer

Mineralium deposita 30 (1995), S. 408-410

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ISSN: 1432-1866

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie

Notizen: Abstract Recent research has shown that Archaean lode-gold deposits occur in environments that range in their metamorphic grade from prehnite-pumpellyite to lower granulite facies. Based on this data a new classification is proposed for these deposits. In this classification, shallow-level gold deposits are classed as epizonal, the so-called “mesothermal” deposits are mesozonal, and the deeper deposits, commonly in mid-amphibolite or lower-granulite terrains, are hypozonal.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00202283

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2

Digitale Medien

Detection of point mutations in chloroplast genes of Antirrhinum majus L. I. Identification of a point mutation in the psaB gene of a photosystem I plastome mutant (1995)

Schaffner, Claudia ; Laasch, Henrik ; Hagemann, Rudolf

Springer

Molecular genetics and genomics 249 (1995), S. 533-544

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ISSN: 1617-4623

Schlagwort(e): Antirrhinum majus ; Plastome mutant ; Photosystem I ; psaB gene ; PCR-SSCP

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract A point mutation in the plastome-encoded psaB gene of the mutant en:alba-1 of Antirrhinum majus L. was identified by an analysis of chloroplast DNA with a modified PCR-SSCP technique. Application of this technique is indicated when a gene or a group of genes is known in which the point mutation is located. Analysis of primary photosynthetic reactions in the yellowish white plastome mutant indicated a dysfunction of photosystem (PS) 1. The peak wavelength of PS I-dependent chlorophyll (Chl) fluorescence emission at 77 K was shifted by 4 nm to 730 nm, as compared to fluorescence from wild-type. There were no redox transients of the reaction center Chl P700 upon illumination of leaves with continuous far-red light or with rate-saturating flashes of white light. The PS I reaction center proteins PsaA and PsaB are not detectable by SDS-PAGE in mutant plastids. Hence, plastome encoded PS I genes were regarded as putative sites of mutation. In order to identify plastome mutations we developed a modified SSCP (single-strand conformation polymorphism) procedure using a large PCR fragment which can be cleaved with various restriction enzymes. When DNA from wild-type and en:alba-1 was submitted to SSCP analysis, a single stranded Hinf I fragment of a PCR product of the psaB gene showed differences in electrophoretic mobility. Sequence analysis revealed that the observed SSCP was caused by a single base substitution at codon 136 (TAT → TAG) of the psaB gene. The point mutation produces a new stop codon that leads to a truncated PsaB protein. The results presented indicate that the mutation prevents the assembly of a functional PS I complex. The applicability to other plastome mutants of the new method for detection of point mutations is discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00290579

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