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  • 1985-1989  (3)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The binding properties of opioid receptors on isolated nerve terminals (neurosecretosomes) from bovine posterior pituitaries were characterized. Both [3H]etorphine and [3H]ethylketocyclazocine ([3H]EKC) showed high-affinity binding with complex binding isotherms, consistent with the presence of multiple classes of binding sites. [D-Ala2,D-Leu5]enkephalin showed no specific binding and failed to displace [3H]etorphine at high concentrations, indicating the absence of μ, δ, or benzomorphan (K2) sites. Mathematical modelling of the data suggested the presence of three classes of binding sites. The first was of high affinity with Kd values of 0.9 and 2.0 nM for etorphine and EKC, respectively. The second class of sites appeared to bindetorphine with a KD of 150 nM, and EKC with extremely low affinity (unmeasurable binding). The third class of sites was characterized by KD values of 7 and 2 μM for etorphine and EKC, respectively. These results indicate that the nerve terminals of bovine posterior pituitary contain opioid binding sites of the K type. Futhermore, these binding sites appear heterogeneous, consisting of at least two and possibly more subtypes or states.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Binding activity of the enkephalin dimer [d-Ala2, Leu5-NH-CH2--]2 (DPE2) to NG108–15 hybrid cells was compared to that of the monomer [d-Ala2, Leu5]enkephalin amide (DALEA). At 25°C, the values of the apparent affinity constant for DPE2, measured to intact and lysed cells and membranes, was 5.0 (±0.09) × 109M−1 for n = 28 experiments, as compared to 0.9 (±0.08) × 109M−1 (n = 16) for DALEA. At 4°C, the binding affinity of DPE2 decreased by 43% and that of DALEA by 33%. An important difference between the binding of DPE2 and DALEA was that, after necessary corrections for difference in maximal “bindability” of the respective tritiated enkephalins, the molar binding capacity for DALEA was twofold higher than for DPE2, although mutual cross-displacement studies indicated that binding occurred to one class of noninteracting homogeneous receptors. The binding capacity for intact and lysed cells and membranes was 20 (±2) × 10−-11M for DPE2 and 43 (±2) × 10−-11M for DALEA. The enkephalin monomers [d-Ala2, d-Leu5]enkephalin (DADLE) and [d-Ala2, Met5]enkephalin amide (DAMEA) showed binding characteristics similar to those of DALEA.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0952-3499
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The N-terminal tripeptide enkephalin analogue, Tyr-D-Ala-Gly, was dimerized at the C-terminus systematically with a series of α,ω-diaminoalkanes, NH2—(CH2)n—NH2 (n = 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, and 22). The binding affinities of dimers for δ opiate receptors in rat brain were evaluated and compared with those for δ receptors in NG108-15 cells. Although the monomeric tripeptide amide was almost inactive, dimers showed a dramatic increase in binding affinity (8-900 times). The enhancement of affinity was apparently related to the number of methylene chains in the crosslinking spacer moiety, and it was maximal at n = 14-18 in the rat brain. In NG cells the activity increased progressively from n = 2 to n = 22 without reaching any apparent peak. These results suggest that δ receptors in rat brain and NG cells may have slight structural differences.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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