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  • 1
    Electronic Resource
    Electronic Resource
    Taurine entry into perilymph of the guinea pig (1998)
    Springer
    European archives of oto-rhino-laryngology and head & neck 255 (1998), S. 331-333 
    Details
    ISSN: 1434-4726
    Keywords: Key words Amino acid transport ; Blood-perilymph barrier ; Cochlea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Taurine is a β-aminosulfonic acid and is a ubiquitous amino acid whose role in the cochlea is not well established. In this study, its entry from blood into perilymph was investigated in the guinea pig as animal model. The penetration rate of [3H]taurine (molecular weight 125) into the perilymph of the scala vestibuli was measured 1 and 2 h after the intravenous infusion of [3H]taurine in nephrectomized animals. Results showed a rate of penetration in perilymph related to plasma at 36 ± 4.7% (n = 5) after 1 h and 43 ± 5.6% (n = 5) after 2 h. Compared to the penetration rate of urea (molecular weight 60) and mannitol (molecular weight 186) reported previously in rats, a passive entry of taurine into perilymph through the blood-perilymph barrier is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004050050071
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  • 2
    Electronic Resource
    Electronic Resource
    Defective RNA packaging is responsible for low transduction efficiency of CAEV-based vectors} (1998)
    Springer
    Archives of virology 143 (1998), S. 681-695 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  Replication defective retroviral vectors are regularly used for transfer and expression of exogenous genes into dividing cells and in animals. Since lentiviruses are able to infect terminally differentiated and non-dividing cells, their use to produce replication defective vectors may overcome this limitation. We developed two replication-defective lentiviral vectors based on the genome of Caprine Arthritis Encephalitis Virus (CAEV). The first vector (pBNL2) carries the neo and lacZ marker genes. Neo gene is expressed from a genomic RNA and lacZ gene from a subgenomic RNA. The second vector (pCSHL) carries a single fusion gene encoding both phleomycin resistance and β-galactosidase activity. Replication-competent CAEV was used as helper virus to provide the viral proteins for transcomplementation of these vectors. Our data demonstrated that the genomes of both vectors were packaged into CAEV virions and transduced into goat synovial membrane cells following infection. However, the vector titers remained 3 to 4 logs lower than those of CAEV. Further analysis showed a lack of accumulation of unspliced pBNL2 RNA into the cytoplasm of producer cells resulting in the packaging of pBNL2 sub-genomic RNA only. In contrast, RNA produced from pCSHL vector was correctly transported to the cytoplasm and more efficiently packaged than the pBNL2 sub-genomic RNA as revealed by slot-blot and quantitative RT/PCR analyses. However this higher packaging efficiency of pCSHL genome did not result in a higher transduction efficiency of lacZ gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007050050323
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of cytochrome c 6 from the cyanobacterium Anabaena PCC 7119 (1997)
    Springer
    JBIC 2 (1997), S. 225-234 
    Details
    ISSN: 1432-1327
    Keywords: Key words Cytochrome c6 ; Anabaena PCC 7119 ; EPR ; NMR ; Redox-Bohr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  A soluble monoheme c–type cytochrome c 6 has been isolated from the cyanobacterium Anabaena PCC 7119. It is a basic protein, with a molecular mass of 9.7 kDa, which accepts electrons from Anabaena ferredoxin in the ferredoxin-NADP+reductase-dependent NADPH cytochrome c reductase activity assay. The turnover of the reaction has an optimum pH at 7.5. Flavodoxin can also replace ferredoxin in this assay, but with only 20% efficiency. Plastocyanin from Anabaena PCC 7119, as well as the c 6 cytochromes from the green algae Chlorella fusca and Monoraphidium braunii are also shown to accept electrons from Anabaena ferredoxin. The reduction potential of cytochrome c 6 at pH 6.7 was determined to be 338 mV and is pH dependent, with pK a ox=8.4±0.1 and pK a red≈9.5. The ferric and ferrous cytochrome forms and their pH equilibria have been studied using visible, EPR and 1H-NMR spectroscopies. The amino acid sequence and the visible and NMR spectroscopic data indicate that the heme iron has a methionine-histidine axial coordination in the pH range 5–11. However, the EPR data for the ferricytochrome are complex and show that in this pH range five distinct forms are present. Between pH 5 and 9 the spectrum is dominated by two rhombic species, with g–values at 2.94, 2.29, 1.43 and at 2.84, 2.34, 1.56, which interconvert with a pK a of 8.4. The NMR data also show a main interconversion between two cytochrome forms at this pH, which coincides with that determined from the pH dependence of the reduction potential. Both these forms were associated with a methionine-histidine heme-iron coordination by correlation with the visible and NMR spectral data, although having crystal field parameters atypical for this type of coordination. Anabaena cytochrome c 6 is one more example of a heme protein for which the widely used crystal field analysis of the EPR data (truth diagram) fails to unequivocally determine the type of heme-iron ligation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050128
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  • 4
    Electronic Resource
    Electronic Resource
    Di-cluster, seven-iron ferredoxins from hyperthermophilic Sulfolobales (1998)
    Springer
    JBIC 3 (1998), S. 499-507 
    Details
    ISSN: 1432-1327
    Keywords: Key words Ferredoxins ; Thermophiles ; Archaea ; EPR ; Iron-sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Seven-iron ferredoxins from the thermoacidophilic archaea Acidianus ambivalens, A. infernus, Metalosphaera prunae and Sulfolobus metallicus were extensively characterised, allowing study of their expression under aerobic and anaerobic growth conditions as well as the putative role in thermal stability of a recently described zinc centre. The archaeon S. metallicus was found to express, under the same growth conditions, two ferredoxins in almost identical amounts, a novelty among Archaea. Most interestingly, these two ferredoxins differ at the N-terminal amino acid sequence in that one has a zinc binding motif (FdA) and the other does not (FdB); in agreement with these findings, FdA contains a zinc ion and FdB does not. These two ferredoxins have identical thermal stabilities, indicating that the zinc atom is not determinant in the protein thermostability. Further, the presence of the additional zinc centre does not interfere with the redox properties of the iron-sulfur clusters since their reduction potentials are almost identical. From the other three archaea, independently of the growth mode in respect to oxygen, only a single zinc-containing ferredoxin was found. EPR studies on the purified proteins, both in the oxidised and dithionite reduced states, allowed the identification of one [3Fe-4S]1+/0 centre and one [4Fe-4S]2+/1+ centre in all proteins studied. The complete sequence of A. ambivalens ferredoxin is reported. Together with the data gathered in this study, the properties of the seven-iron ferredoxins from Sulfolobales so far known are re-discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050260
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  • 5
    Electronic Resource
    Electronic Resource
    The membrane-bound high-molecular-mass cytochromes c from Desulfovibrio gigas and Desulfovibrio vulgaris Hildenborough; EPR and Mössbauer studies (1997)
    Springer
    JBIC 2 (1997), S. 23-31 
    Details
    ISSN: 1432-1327
    Keywords: Key words Multiheme cytochrome c ; Desulfovibrio ; Membrane proteins ; Electron transfer ; EPR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The high-molecular-mass cytochromes c (Hmcs) from the sulfate-reducing bacteria Desulfovibrio gigas and Desulfovibrio vulgaris (Hildenborough) were found to be strongly bound to the cytoplasmic membrane. After detergent solubilization they were shown to be water soluble and to be similar to those previously isolated from the soluble fractions in terms of N-terminal sequence, molecular mass, UV-visible and EPR spectroscopies. In D. gigas, higher amounts of Hmc can be obtained from the membranes than from the soluble fraction. This enabled further characterization of both cytochromes. The apparent heme reduction potentials of both Hmcs, determined at pH 7.5 through visible and EPR redox titrations, span a large range of redox potentials, approximately between 0 and –280 mV, and can be roughly divided into three groups: four to five hemes have E 0s of –30 mV to –100 mV, three to four hemes have E 0s around –170 mV, and seven to eight hemes have a lower E 0 of –250 to –280 mV. Several of these redox potentials are strongly pH dependent. Mössbauer studies of oxidized and reduced D. vulgaris Hmc show that this protein contains two high-spin hemes in both oxidation states. The rate of reduction of both Hmcs with the periplasmic hydrogenases from the corresponding organisms is extremely slow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050102
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