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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of iodopropyl derivatives of adenosine 3′,5′-cyclic-monophosphate: Potential affinity labels of cAMP binding sites in enzymes (1983)
    Springer
    The protein journal 2 (1983), S. 113-129 
    Details
    ISSN: 1573-4943
    Keywords: cyclic AMP derivatives ; affinity labels ; chemical modification of enzymes ; nucleotide affinity labels ; cAMP phosphodiesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The syntheses of two potential cAMP affinity lables, 1,N 6-(3-iodopropyleno)adenosine 3′,5′-cyclic-monophosphate and 2′-O-(2-iodo-3-hydroxypropyl) adenosine 3′,5′-cyclic-monophosphate, by a two-step chemical procedure are described. TheN 6- and 2′-O-allyl intermediates were prepared selectively by alkylation of cAMP in organic and alkaline aqueous solutions, respectively. Treatment of theN 6-allyl derivative withN-iodosuccinimide resulted in iodine addition to the double bond and cyclization to theN 1 position of the purine ring. The iodohydrin analog was synthesized by reaction of 2′-O-allyl-cAMP with potassium iodide and thallium trichloride in acetate buffered solution. The products were isolated by column chromatography and characterized by thin-layer chromatography, elemental analysis, and ultraviolet,13C, and1H NMR spectroscopy. The cAMP analogs were found to react with lysine and cysteine. Both cAMP derivatives were tested for their reaction with the low-K m cAMP phosphodiesterase of human platelets. The ribose-substituted analog functioned as a competitive inhibitor (K I =0.72 μM) and caused a time-dependent irreversible inactivation of the phosphodiesterase. In contrast, the purine-substituted derivative acted neither as a reversible competitive inhibitor nor as an irreversible inactivator of the enzyme. These results indicate the specificity of these potential cAMP analogs in their interaction with the phosphodiesterase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025376
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  • 2
    Electronic Resource
    Electronic Resource
    A non-motorized dye ejector for visualization of flow in situ and its use with coral reef crinoids (1984)
    Springer
    Marine biology 83 (1984), S. 125-128 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe a portable, non-motorized device for delivering a tracer dye into seawater under field conditions. Dye is ejected at a constant flow rate over a period of tens of minutes. The ejector works in a wide range of ambient pressures without external energy requirements. The flow rate is adjusted simply by varying the length of the delivery tube. The dye streams permitted observations of the upcurrent and downcurrent flow regimes for a filter-feeding crinoid (Comanthus bennetti) living at a depth of 8 m on a coral reef. The results indicate that the crinoid may enhance the rate of particle capture by changing the scale of turbulence in the water passing through the mesh of the filtration fan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394719
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  • 3
    Electronic Resource
    Electronic Resource
    Exclusion of two candidate pigment loci, c and b, part of chromosome 11p, and 33 random polymorphic markers as the locus for tyrosinase-positive oculocutaneous albinism (1993)
    Springer
    Human genetics 〈Berlin〉 90 (1993), S. 556-560 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The locus for Tyrosinase-Positive Oculocutaneous Albinism (ty-pos OCA) has not yet been localised. The search for the ty-pos OCA locus has included a search for linkage to candidate pigment loci and a candidate chromosomal region, as well as a random search using highly polymorphic markers in 42 families, including 271 individuals of whom 79 are affected. The lod scores for the tyrosinase (TYR) locus (11q14–q21), homologous to the albino locus, c, in the mouse and the CAS2/TRP1 locus (9p22-pter), homologous to the brown locus, b, in the mouse were -5.89 and -7.22, respectively, at a recombination fraction of θ=0.01, thus excluding them from being the ty-pos OCA locus. In the candidate chromosomal region, 11p, four loci (probes) were tested, SAA (pSAA82), CALC (pHC36), HBB (Gamma-globin haplotype) and an AC repeat polymorphism at the Wilm's Tumour locus (WT1). A portion of 11p was excluded with the following lod scores: pSAA82 lod=-2.05 at θ=0.10; pHC36 lod=-3.87 at θ=0.05; gamma-globin haplotype lod=-2.80 at θ=0.10; and WT1 lod=-2.34 at θ=0.10. Thirty-three polymorphic markers randomly distributed on 13 different chromosomes were all excluded from close linkage to ty-pos OCA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217458
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of a malate dehydrogenase in the cyanobacterium Coccochloris peniocystis (1991)
    Springer
    Archives of microbiology 156 (1991), S. 28-33 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Malate dehydrogenase ; Glyoxylate cycle ; TCA cycle ; Carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A malate dehydrogenase (MDH) was characterized from the cyanobacterium Coccochloris peniocystis. The enzyme was purified approximately 180-fold and had a molecular weight of about 90000. The enzyme had a pH optimum of pH 6.7 to 7.5; a Km (malate) of 5.6 mM and Kms for NAD and NADP of 24 μM and 178 μM, respectively, although similar Vmax were obtained with either pyridine nucleotide. Enzyme activity was inhibited by ATP, citrate, oxalacetate, acetyl CoA and CoA. Enzyme assays with uniformly 14C-labelled malate caused no 14CO2 release, indicating this MDH is not a malic enzyme. Electrophoresis and S-200 gel filtration of the partially purified enzyme indicated a single MDH was present in this preparation. A second, less abundant, MDH was present in crude extracts. The presence of MDH in this organism is consistent with the operation of a glyoxylate cycle which, in the absence of a TCA cycle, would provide organic acids required in secondary carbon metabolism. ATP inhibition of MDH may allow for light regulation of MDH activity since, in the light, oxaloacetic acid is generated by phosphoenolpyruvate carboxylase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418183
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  • 5
    Electronic Resource
    Electronic Resource
    Formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis (1992)
    Springer
    Archives of microbiology 157 (1992), S. 375-380 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Glycolate metabolism ; Photosynthesis ; Glyoxylate cycle ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis was investigated and the activities of enzymes of glycolate metabolism assayed. Photosynthetic 14CO2 incorporation was O2 insensitive and no labelled glycolate could be detected in cells incubated at 2 and 21% O2. Under conditions of 100% O2 glycolate comprised less than 1% of the acid-stable products indicating ribulose 1,5 bisphosphate (RuBP) oxidation only occurs under conditions of extreme O2 stress. Metabolism of [1-14C] glycolate indicated that as much as 62% of 14C metabolized was released as 14CO2 in the dark. Metabolism of labelled glycolate, particularly incorporation of 14C into glycine, was inhibited by the amino-transferase inhibitor amino-oxyacetate. Metabolism of [2-14C] glycine was not inhibited by the serine hydroxymethyltransferase inhibitor isonicotinic acid hydrazide and little or no labelled serine was detected as a result of 14C-glycolate metabolism. These findings indicate that a significant amount of metabolized glycolate is totally oxidized to CO2 via formate. The remainder is converted to glycine or metabolized via a glyoxylate cycle. The conversion of glycine to serine contributes little to glycolate metabolism and the absence of hydroxypyruvate reductase confirms that the glycolate pathway is incomplete in this cyanobacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248684
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  • 6
    Electronic Resource
    Electronic Resource
    The structure determination of the variable portion of the Bence-Jones protein Au (1975)
    Springer
    European biophysics journal 1 (1975), S. 139-146 
    Details
    ISSN: 1432-1017
    Keywords: Immunoglobulin ; Bence-Jones ; X-Ray ; Structure ; Rotation-Function ; Patterson Search ; Translation Function ; Molecular Replacement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The structure of a χ-type Bence-Jones protein variable fragment Au has been determined by molecular replacement methods using the known structure of an other Bence-Jones variable fragment Rei (Epp et al., Eur. J. Biochem. 45, 513 (1974)). The crystallographic R factor is 0.31 for about 4000 significantly measured reflections between 6.8 to 2.5 å. The Au protein forms a dimer across a crystallographic two fold axis. The spatial relationship of the two monomers, the conformation of the backbones and of the internal residues is extremely similar to that found in Rei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539775
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  • 7
    Electronic Resource
    Electronic Resource
    Subunit symmetry of tetrameric phosphorylase a (1976)
    Springer
    European biophysics journal 2 (1976), S. 43-59 
    Details
    ISSN: 1432-1017
    Keywords: Glycogen Phosphorylase ; Subunit Symmetry ; Non-crystallographic Symmetry ; Rotation Function ; Translation Function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Native crystallographic data of tetrameric phosphorylase a crystals, space group P21; have been collected photographically to 3 å resolution. These data have been used in Patterson search methods in reciprocal and real space. The tetramers were found to exhibit molecular 222 symmetry. The cross vector between the centres of the two symmetry related tetramers in the unit cell was determined by two different translation function methods. On the basis of these rotation and translation function results a model for the arrangement of monomers within the tetramer and of tetramers in the unit cell is proposed. The 222 symmetry of the tetrameric molecule is found only when high resolution diffraction data are included (i.e. higher than 6 å). At lower resolution other symmetries dominate. Calculations with the proposed model have shown that these spurious symmetries result from the nonspecific overlap of protein-protein and solvent-solvent cross vectors. These results emphasize the importance of high resolution data when noncrystallographic symmetry of globular proteins is studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535652
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  • 8
    Electronic Resource
    Electronic Resource
    Hepatic extraction of morphine is impaired in cirrhosis (1989)
    Springer
    European journal of clinical pharmacology 36 (1989), S. 501-506 
    Details
    ISSN: 1432-1041
    Keywords: morphine ; cirrhosis ; drug metabolism ; glucuronidation ; hepatic extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Using hepatic vein catheterization this study has provided the first direct measurement of morphine hepatic extraction in 8 controls and 8 cirrhotics. The extraction ratio was 0.52 in the control group and was reduced by 25% in the cirrhotics. This reduction is due to impaired enzyme capacity rather than reduced blood flow. The effect of cirrhosis is less than that reported in similar studies of high clearance oxidized drugs and this lends support to the concept that glucuronidation may be relatively spared in cirrhosis. A discrepancy between the systemic clearance and the hepatic clearance provides indirect support for extra-hepatic metabolism of morphine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558076
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  • 9
    Electronic Resource
    Electronic Resource
    Research on streptococci in the UK (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 39-40 
    Details
    ISSN: 1573-0972
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02421487
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  • 10
    Electronic Resource
    Electronic Resource
    Mathematical model of the activation of prothrombin by factor X a and factor V t (1980)
    Springer
    Bulletin of mathematical biology 42 (1980), S. 861-870 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A mathematical model of prothrombin activation is being proposed which includes the feedback mechanism of thrombin and the alteration of factor V by thrombin. This model is in good agreement with experimental data for the dependence of the rate of thrombin formation on the concentrations of factors V and X a . In particular, it correctly predicts the existence and location of a maximum in both of these cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461064
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