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  • Biochemistry and Biotechnology  (2)
  • Clay-fixed NH inf4 sup+  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Transformations of chemically fixed liquid anhydrous ammonia by soil microorganisms (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 145-150 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen-15 ; Ammonia fixation ; Organic matter-fixed NH3 ; Clay-fixed NH inf4 sup+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The application of liquid anhydrous NH3 to soil leads to chemical fixation of NH3 by organic matter and of NH inf4 sup+ by clay minerals. A laboratory study was conducted to ascertain the biological transformations of newly fixed liquid anhydrous 15NH3 in a Drummer silty clay loam by incubation of the 15N-labelled soil with glucose for 0, 7, 30, and 90 days and by sequential extraction of organic-matter-fixed 15NH3 with 0.15 M Na4P2O7, 0.15 M KOH, 0.1 M NaOH, and acidified dimethyl sulfoxide. About 16% of the 15NH3 injected was fixed, of which 52% was accounted for by clay fixation. The various humic fractions (fulvic acid, humic acid, and humin) were obtained, and the distribution patterns of the fixed 15NH3-N in these fractions were compared. The potential availability of the fixed 15NH3-N was also estimated. The percentage of the 15NH3 recovered as organic-matter-fixed 15NH3 decreased as the length of incubation increased (to 28% after 90 days); the decrease was attributed in part to an increase in the amount recovered as clay-fixed NH inf4 sup+ (from 52 to 64%). Changes in the distribution of the organic-matter-fixed 15NH3-N in the humic fractions included: (1) an increase in the relative amount of the fixed 15NH3 as humic acid in both the Na4P2O7 and KOH extracts, (2) an increase in the percentage of organic-matter-fixed 15NH3-N in the fulvic acid fractions as high-molecular-weight components (determined by dialysis) or as generic fulvic acid (determined by sorption-desorption from XAD-8 resin), and (3) an increase in the percentage of the organic-matter-fixed 15NH3 as humin. The potential availability of the organic-matter-fixed 15NH3-N decreased as the length of the incubation increased, from 22 to 4% over the 90-day incubation period, and was correlated significantly (0.05 level) with Na4P2O7-extractable N. These results suggest that organic-matter-fixed liquid anhydrous NH3 is initially more labile than the native soil N but becomes less labile with time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336380
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in crystal properties and ligand affinities of an antifluorescyl fab (4-4-20) in two solvent systems (1988)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 3 (1988), S. 155-160 
    Details
    ISSN: 0887-3585
    Keywords: monoclonal antibodies ; high-affinity combining sites ; MPD ; Effects of fluorescein binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An antigen-binding fragment (Fab) from a murine monoclonal antibody (4-4-20) with high affinity for fluorescein was cocrystallized with ligand in polyethylene glycol (PEG) and 2-methl-2,4-pentanediol (MPD) in forms suitable for X-ray analyses. In MPD the affinity of the intact antibody for fluorescein was 300 times lower than the value (3.4 × 1010 M-1) obtained in aqueous buffers. This decreased affinity was manifested by the partial release of bound fluorescein when MPD was added to solutions of liganded Feb during crystallization trials, In PEG, the ligand remained firmly bound to the protein. The liganded Feb crystallized in the monoclinic space group P21 in PEG, with a = 58.6, b = 97.2, c = 44.5 Å and β = 95.2°. In MPD the space group was triclinic P1, with a = 58.3, b = 43.4, c = 42.3 Å, α = 83.9°, β = 87.6°, and γ = 84.5°. X-ray diffraction data were collected for both forms to 2.5-Å resolution. Surprisingly, the triclinic form of the liganed antifluorescyl Feb had the same space group, closely similar cell dimensions, and practically the same orientation in the unit cell as an unliganded Fab (BV04-01) with activity against single-stranded DNA.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340030304
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  • 3
    Electronic Resource
    Electronic Resource
    An autoantibody to single-stranded DNA: Comparison of the three-dimensional structures of the unliganded fab and a deoxynucleotide-fab complex (1991)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 11 (1991), S. 159-175 
    Details
    ISSN: 0887-3585
    Keywords: anti-ss-DNA autoantibody ; deoxynucleotide-Fab complex ; conformational changes in protein when ligand is bound ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystal structures of the Fabs from an autoantibody (BV04-01) with specificity for single-stranded DNA have been determined in the presence and absence of a trinucleotide of deoxythymidylic acid, d(pT)3. Formation of the ligand-protein complex was accompanied by small adjustments in the orientations of the variable (VL and VH) domains. In addition, there were local conformational changes in the first hypervariable loop of the light chain and the third hypervariable loop of the heavy chain, which together with the domain shifts led to an improvement in the complementarity of nucleotide and Fab. The sugar-phosphate chain adopted an extended and “open” conformation, with the base, sugar, and phosphate components available for interactions with the protein. Nucleotide 1 (5′-end) was associated exclusively with the heavy chain, nucleotide 2 was shared by both heavy and light chains, and nucleotide 3 was bound by the light chain. The orientation of phosphate 1 was stabilized by hydrogen bonds with serine H52a and asparagine H53. Phosphate 2 formed an ion pair with arginine H52, but no other charge-charge interactions were observed. Insertion of the side chain of histidine L27d between nucleotides 2 and 3 resulted in a bend in the sugar-phosphate chain. The most dominant contacts with the protein involved the central thymine base, which was immobilized by cooperative stacking and hydrogen bonding interactions. This base was intercalated between a tryptophan ring (no. H100a) from the heavy chain and a tyrosine ring (no. L32) from the light chain. The resulting orientation of thymine was favorable for the simultaneous formation of two hydrogen bonds with the backbone carbonyl oxygen and the side chain hydroxyl group of serine L91 (the thymine atoms were the hydrogen on nitrogen 3 and keto oxygen 4).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340110302
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    Paper (German National Licenses)
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