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  • 1
    Electronic Resource
    Electronic Resource
    Novel hydroxycarotenoids with improved antioxidative properties produced by gene combination in Escherichia coli (2000)
    [s.l.] : Nature America Inc.
    Nature biotechnology 18 (2000), S. 843-846 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have used combinatorial biosynthesis to synthesize novel lipophilic carotenoids that are powerful cellular antioxidants. By co-expressing three different carotenoid desaturases in combination with a carotenoid hydratase, a cyclase, and a hydroxylase on compatible plasmids in Escherichia coli, we ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/78443
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  • 2
    Electronic Resource
    Electronic Resource
    New carotenoids from the thermophilic green sulfur bacterium Chlorobium tepidum: 1′,2′-dihydro-γ-carotene, 1′,2′-dihydrochlorobactene, and OH-chlorobactene glucoside ester, and the carotenoid composition of different strains (1997)
    Springer
    Archives of microbiology 168 (1997), S. 270-276 
    Details
    ISSN: 1432-072X
    Keywords: Key words Carotenoid biosynthesis ; Green sulfur ; bacteria ; Thermophily ; Chlorobium tepidum ; 1′ ; 2′-Dihydro-γ-carotene ; 1′ ; 2′-Dihydrochlorobactene ; OH-Chlorobactene glucoside ester ; Nicotine ; Bacteriochlorophyll c
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The complete carotenoid composition of the thermophilic green sulfur bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: γ-carotene, chlorobactene, and their 1′,2′-dihydro derivatives (1′,2′-dihydro-γ-carotene and 1′,2′-dihydrochlorobactene). In lesser amounts, hydroxyl γ-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonsulfur bacterium Chloroflexus aurantiacus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050498
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of the CO2/O2 specificity of ribulose 1, 5-bisphosphate carboxylase/oxygenase by 31P- and 1H-NMR (1998)
    Springer
    Photosynthesis research 58 (1998), S. 103-109 
    Details
    ISSN: 1573-5079
    Keywords: carboxylation ; oxygenation ; Rubisco ; specificity factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High resolution NMR spectroscopy has been demonstrated to be capable of measuring the CO2/O2 specificity factor of ribulose 1,5-bisphosphate carboxylase/oxygenase. 31P-NMR provides a simple method for quantitatively determining the ratio of the products, 3-phosphoglycerate and phosphoglycolate. Both the specificity factor and degree of the reaction can be measured during the reaction without the need for complete consumption of ribulose bisphosphate or removal of it from the reaction mixture. Inorganic phosphate can also be detected and this may be used for monitoring the phosphatase activity and pH changes. Measurement by highly sensitive 1H-NMR is most time-efficient and is particularly suitable for the Rubisco with a high specificity factor. By optimizing the experimental conditions, it is possible to follow the simultaneous reactions in situ. The NMR method has been applied to three Rubisco enzymes with different values of specificity factor. Both 31P- and 1H-NMR gave similar results, agreeing with those previously reported by other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006094721113
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  • 4
    Electronic Resource
    Electronic Resource
    Structures of chlorosomes and aggregated BChlc inChlorobium tepidum from solid state high resolution CP/MAS13C NMR (1994)
    Springer
    Photosynthesis research 41 (1994), S. 211-223 
    Details
    ISSN: 1573-5079
    Keywords: antenna structure ; green photosynthetic bacteria ; cross polarization ; magic angle spinning ; ring current shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cross polarization/magic angle spinning (CP/MAS)13C (solid state high resolution) NMR spectra were observed for chlorosomes and BChlc aggregates. Similarity of both kinds of spectra (except for some signals assignable to proteins and lipids in chlorosomes) indicates that BChlc's in chlorosomes are present just as in synthetic BChlc aggregates. Chemical shifts for C131 carbonyl and C31 hydroxylethyl carbons indicate hydrogen bonding between them. Comparison of solution and solid state13C NMR chemical shifts shows the five coordinated nature of BChlc aggregates. Some chemical shift differences were attributable to ring currents shifts. Their comparisons with calculated ring current shift values predicted structures for the aggregates. Cross polarization dynamics of the CP/MAS13C NMR signals explored dynamic and structural nature of the BChlc aggregates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184162
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  • 5
    Electronic Resource
    Electronic Resource
    High-resolution solid-state 13C NMR of the LH1 from Rhodospirillum rubrum (1997)
    Springer
    Photosynthesis research 52 (1997), S. 167-173 
    Details
    ISSN: 1573-5079
    Keywords: bacteriochlorophyll ; correlation time ; cross-polarization ; light harvesting ; mobility ; relaxation time ; T1ρH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High-resolution solid-state 13C NMR spectra of the light-harvesting antenna complex (LH1) from Rhodospirillum rubrum were observed for the first time by cross-polarization (CP), magic angle spinning (MAS) methods with a total elimination of spinning side band technique (TOSS). Chemical shift analysis of the CP/MAS/TOSS 13C NMR spectra confirmed that the LH1 consists mainly of α-helices in the solid state. Time constants of cross polarization (TCH) and relaxation time T1 in a rotating frame (T1ρH) were determined from the experiments at various contact times. Smaller values of TCH were obtained for the carbons attached directly with protons in a rigid state. Relaxation times T1ρH revealed the dynamic structure of the complex and showed that bacteriochlorophyll a in the LH1 has high internal mobility even in the solid state. The proton spin-lattice relaxation time in a laboratory frame (T1H) determined by the 13C NMR signal amplitude changes suggested that protons in the LH1 proteins have such strong interaction among them that the spins of all protons in the protein can diffuse through spin-lattice-relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005802117233
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  • 6
    Electronic Resource
    Electronic Resource
    Biochemical and spectral characterization of the core light harvesting complex 1 (LH1) from the thermophilic purple sulfur bacterium Chromatium tepidum (1998)
    Springer
    Photosynthesis research 58 (1998), S. 193-202 
    Details
    ISSN: 1573-5079
    Keywords: bacterial antenna ; chromatiaceae ; membrane protein ; puf operon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photoreceptor complex (LH1-RC) of the thermophilic purple sulfur bacterium Chromatium tepidum (Chr. tepidum) has been investigated and isolated using the detergent Triton X-100 followed by sucrose density gradient centrifugation (SDGC). The isolated LH1-RC complex had an absorption maximum at 915 nm, the longest absorption band observed in light harvesting complex 1 (LH1) in purple bacteria containing bacteriochlorophyll a (BChl a). The absorption maximum of this LH1-RC complex showed a 30 nm blue-shift to 885 nm after being purified by DEAE cellulose column chromatography. The blue-shifted absorption band was found to return to 915 nm after removing the salt ion, indicating a reversible effect of salt ion on this LH1-RC complex. We have determined the nucleotide sequences of genes coding for the α, β polypeptide subunits of the LH1 core complex from Chr. tepidum and have found some characteristic features. The deduced amino acid sequences of the α subunit showed a deletion of an arginine residue in the C terminal of membrane helix. A possible correlation between the unusual absorption behavior and structural features of α and β polypeptide subunits of the LH1 core complex is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006146713751
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  • 7
    Electronic Resource
    Electronic Resource
    Excitation energy transfer in the green photosynthetic bacterium Chloroflexus aurantiacus: A specific effect of 1-hexanol on the optical properties of baseplate and energy transfer processes (1996)
    Springer
    Photosynthesis research 48 (1996), S. 263-270 
    Details
    ISSN: 1573-5079
    Keywords: Chloroflexus aurantiacus ; chlorophyll ; chlorosome ; energy transfer ; green bacteria ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of 1-hexanol on spectral properties and the processes of energy transfer of the green gliding photosynthetic bacterium Chloroflexus aurantiacus was investigated with reference to the baseplate region. On addition of 1-hexanol to a cell suspension in a concentration of one-fourth saturation, a specific change in the baseplate region was induced: that is, a bleach of the 793-nm component, and an increase in absorption of the 813-nm component. This result was also confirmed by fluorescence spectra of whole cells and isolated chlorosomes. The processes of energy transfer were affected in the overall transfer efficiency but not kinetically, indicating that 1-hexanol suppressed the flux of energy flow from the baseplate to the B806-866 complexes in the cytoplasmic membranes. The fluorescence excitation spectrum suggests a specific site of interaction between bacteriochlorophyll (BChl) c with a maximum at 771 nm in the rod elements and BChl a with a maximum at 793 nm in the baseplate, which is a funnel for a fast transfer of energy to the B806-866 complexes in the membranes. The absorption spectrum of chlorosomes was resolved to components consistently on the basis, including circular dichroism and magnetic circular dichroism spectra; besides two major BChl c forms, bands corresponding to tetramer, dimer, and monomer were also discernible, which are supposed to be intermediary components for a higher order structure. A tentative model for the antenna system of C. aurantiacus is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041017
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  • 8
    Electronic Resource
    Electronic Resource
    Size distribution and photophosphorylation of chromatophores from t Rhodospirillum rubrum (1997)
    Springer
    Photosynthesis research 51 (1997), S. 51-59 
    Details
    ISSN: 1573-5079
    Keywords: aggregation ; dynamic light scattering ; hydrodynamic diameter ; 31P-NMR ; t R. rubrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphology and photophosphorylation of chromatophores from t Rhodospirillum rubrum have been investigated by dynamic light scattering (DLS) and in situ 31P-NMR measurement. Two components, designated as light and heavy fractions, with different average sizes and size distributions were detected by the DLS and can be separated by sucrose density gradient centrifugation. The light fraction has an average size of about 140 nm in diameter with a narrow distribution and shows a high activity of photophosphorylation. About 70 of ADP were found to be converted to ATP purely by the photophosphorylative reaction. In contrast, the heavy fraction has a broad size distribution centered around 350 nm and a low activity of photophosphorylation. Only about 50 of ADP was converted into ATP and AMP with a ratio of 7:3, indicating that most membrane-bound adenylate kinase are attached on the particles of the heavy fraction. Effect of physical disruption on the structural integrity of chromatophores has been examined by using sonication with various oscillating strengths. The result shows that the morphology of chromatophores for both light and heavy fractions is relatively stable to the disruption, while the photophosphorylative activity of the light fraction is very sensitive to the disrupting strength, suggesting that the internal structure of the purified chromatophores could be partially damaged by the disruption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005788528069
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  • 9
    Electronic Resource
    Electronic Resource
    The genes coding for the L, M and cytochrome subunits of the photosynthetic reaction center from the thermophilic purple sulfur bacterium t Chromatium tepidum (1997)
    Springer
    Photosynthesis research 51 (1997), S. 71-82 
    Details
    ISSN: 1573-5079
    Keywords: chromatiaceae ; γ subclass ; membrane protein ; PCR ; t pufoperon ; tetraheme cytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The complete nucleotide sequences of the genes coding for L, M protein subunits and part of cytochrome subunit of the photosynthetic reaction center were determined for the thermophilic purple sulfur bacterium t Chromatium tepidum (t Chr. tepidum) which belongs to the γ subclass. The DNA fragments with 860 bp and 1900 bp were amplified by the Polymerase Chain Reaction (PCR) with the primers designed on the basis of amino acid sequences according to chemical sequence analysis of the proteins. The deduced amino acid sequences of these genes showed a significantly high degree of homology with those from purple non-sulfur bacteria. The L subunit consisted of 280 amino acids and had a molecular mass of 31,393. The M subunit consisted of 324 amino acids and had a molecular mass of 36,299. The aligned sequences of the L subunits of other purple bacterial reaction center polypeptides, showed the insertion of 8 amino acids in t Chr. tepidum in the connection of the first and second membrane-spanning helices different from those of purple non-sulfur bacteria. The aligned sequences of the L, M and cytochrome subunits were compared with other species and discussed in terms of phylogenetic trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005718404736
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  • 10
    Electronic Resource
    Electronic Resource
    How the formation process influences the structure of BChl c aggregates (1999)
    Springer
    Photosynthesis research 60 (1999), S. 229-239 
    Details
    ISSN: 1573-5079
    Keywords: BChl c-stacking size ; chlorosomes ; high aggregates ; ordering of BChl c molecules ; time variation of absorption spectra ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The change of absorption spectra has been measured during the drying process of (31 R)bacteriochlorophyll (BChl) c from diethyl ether, dichloromethane (CH2Cl2) and carbon tetrachloride (CCl4) solutions. Absorption maxima of the Qy(0–0) transition of BChl c appear at 659 nm in diethyl ether, 680 nm in CH2Cl2 and 710 nm in CCl4. All these peaks are red-shifted to about 740 nm with formation of solid high aggregates when the solutions are completely dried. Fourier transform infrared spectra of the three solid aggregates are almost identical. However, magnetic circular dichroism and circular dichroism spectra are different and can be explained in terms of variations in stacking size of the aggregates and molecular arrangement of BChl c. Small-angle X-ray diffraction has been observed only for the aggregates treated with CH2Cl2, and the same sample gave rise to highly resolved cross polarization/magic angle spinning 13C nuclear magnetic resonance spectrum. The results suggest that molecular ordering of the solid-state BChl c aggregates is highly dependent on the formation process which is largely determined by the solvent used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006258029191
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