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  • 5-Hydroxytryptophan  (2)
  • dopamine  (2)
  • 1
    Digitale Medien
    Digitale Medien
    5-Hydroxytryptophan: An absorption and fluorescence probe which is a conservative replacement for [A14 tyrosine] in insulin (1995)
    Springer
    The protein journal 14 (1995), S. 225-232 
    Details
    ISSN: 1573-4943
    Schlagwort(e): 5-Hydroxytryptophan ; tryptophan ; insulin analogs ; fluorescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Use of insulin's intrinsic tyrosine absorption and fluorescence to monitor its interaction with the insulin receptor is limited because the spectral properties of the receptor tryptophan residues mask the spectral properties of the hormone tyrosine residues. We describe the synthesis of an insulin analog where A14 tyrosine is replaced by a tryptophan analog, 5-hydroxytryptophan. This insulin is spectrally enhanced since 5-hydroxytryptophan has an absorption band above 300 nm which is at lower energies than the absorption of tryptophan. Steady-state and time-resolved fluorescence parameters indicate that 5-hydroxytryptophan reports the same information about the environment of the A14 side chain as does the corresponding tryptophan-containing insulin. The synthetic hormone is a full agonist compared to porcine insulin, but has slightly reduced specific activity. Consequently, this spectrally enhanced insulin analog will be useful for hormone-receptor interaction studies since it can be observed by both absorption and fluorescence even in the presence of the tryptophan-containing receptor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01886763
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  • 2
    Digitale Medien
    Digitale Medien
    Effects on protein structure and function of replacing tryptophan with 5-hydroxytryptophan: Single-tryptophan mutants of the N-terminal domain of the bacteriophage λ repressor (1996)
    Springer
    The protein journal 15 (1996), S. 77-86 
    Details
    ISSN: 1573-4943
    Schlagwort(e): 5-Hydroxytryptophan ; tryptophan ; conformational energy computations ; λ-repressor mutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Conformational energy computations have been carried out on the N-acetyl-N′-methylamide of 5-hydroxytryptophan (5OH-Trp) using ECEPP/3. As observed with tryptophan (Trp), the most preferred conformation about theC α −C β bond of the side chain isg + ort. This preference is reduced to only thet conformational state when 5-hydroxyTrp is in the middle of a right-handed poly(l-alanine)α-helix. A similar result has been obtained with Trp [Pielaet al. (1987),Biopolymers 1987, 1273–1286]. These results suggest that replacement of Trp by its analog 5-hydroxyTrp may be tolerated in anα-helix. To test this hypothesis, we have replaced Trp by 5OH-Trp in the fifth helices of two functionally active mutants of the N-terminal domain of the bacteriophage λ repressor. Computations on the packing of these helices have shown that no significant structural changes result from the replacement of Trp by 5OH-Trp. The DNA-binding activity of these mutants, as assessed indirectly through geometrical parameters, is also unaltered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01886813
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  • 3
    Digitale Medien
    Digitale Medien
    Release of3H-dopamine and Analogous monoamines from rat striatal tissue (1988)
    Springer
    Cellular and molecular neurobiology 8 (1988), S. 205-216 
    Details
    ISSN: 1573-6830
    Schlagwort(e): amphetamines ; dopamine ; false transmitters ; lithium ; release ; striatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. The release of previously accumulated3H-dopamine (DA) from minces of striatal tissue prepared from the brains of pargyline-pretreated rats was evaluated by superfusion with a physiological buffer solution in a six-chamber apparatus with silver toroid electrodes to provide electrical field stimuli. The identity of released tritium as3H-DA was demonstrated chromatographically and3H-DA taken up was found in a synaptosomal subcellular fraction. 2. Release of3H-DA previously accumulated at 0.3µM was found to be linearly dependent on stimulus intensity between 1 and 10 V (for 60 sec); 5 V was selected as a standard stimulus. 3. Release of3H-DA did not occur from minces of rat liver, nor was there release of previously accumulated labeled urea or leucine from striatal tissue by electrical stimulation, 50 mM KCL, or 0.1 mM (+)-amphetamine. When3H-DA was taken up in the presence of cocaine (1 mM) or benztropine (100µM), electrically induced release of3H-DA was markedly reduced, while spontaneous efflux was much less altered. 4. Release of3H-DA was also induced by depolarizing concentrations of K+, as well as by Rb+ or NH 4 + , and by veratridine. Electrical release and that induced by 50 mM K+ or 100µM veratridine was blocked by the omission of Ca2+ (with EDTA added) and that induced by veratridine was blocked by tetrodotoxin (30µM). 5. While Mg2+ and Mn2+ had little effect on electrical release of3H-DA, Li+ had a clearly inhibitory effect (IC50, ca. 0.3 mM). 6. Other monoamines induced significant efflux of3H-DA from unstimulated tissue, in descending rank order of effectiveness:p-tyramine 〉 (+)-α-methyl-tyramine (p-hydroxyamphetamine) ⩾ (+)-amphetamine 〉 (−)-amphetamine = 5-hydroxytryptamine (serotonin) = (±)-p-hydroxynorephedrine. 7. Other tritiated monoamines, previously accumulated at 0.3–0.7µM, were also released by electrical stimulation in the following descending rank order: (±)-octopamine ⩾ tyramine ⩾ (±)-norepinephrine = dopamine = (±)-metaraminol = (±)-α-methyltryamine » (±)-normetanephrine = 3-methoxytyramine. 8. Electrical release of3H-DA was largely unaffected by reserpine pretreatment [in the presence of a monamine oxidase (MAO) inhibitor]; release of tritiated tyramine, metaraminol, norepinephrine, and especially octopamine, was somewhat more reserpine sensitive. 9. These results indicate that3H-DA, previously accumulated by highaffinity uptake, can be released by electrical, ionic, or other depolarizing stimuli, and its efflux increased by monoamines [such as (+)-amphetamine] that also compete for uptake. Depolarization-induced release was highly calcium dependent, was inhibited by tetrodotoxin, and was strongly inhibited by lithium. Severalp-hydroxy analogues of DA or amphetamine (but not their 3-methoxy congeners) also were released by electrical-field stimulation, suggesting that they may be able to act as alternative or “false” transmitters in DA nerve terminals of the mammalian brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00711246
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  • 4
    Digitale Medien
    Digitale Medien
    S-(+)-aporphines are not selective for human D3 dopamine receptors (1994)
    Springer
    Cellular and molecular neurobiology 14 (1994), S. 185-191 
    Details
    ISSN: 1573-6830
    Schlagwort(e): aminoergolines ; aminotetralins ; aporphines ; dopamine ; D2 ; D3 ; receptors ; striatum ; transfection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. Our aim was to test the hypothesis that selectivity for D3 dopamine (DA) receptors may contribute to limbic anti-DA selectivity ofS-(+)-aporphine DA partial agonists. 2. Affinity was tested with3H-emonapride, using human D3 receptors in mouse fibroblasts and D2 receptors in rat striatal tissue. 3. D3 receptors showed a picomolar affinity for3H-emonapride, Na+ dependence, and reversible saturability, as well as stereoselectivity. Confirmatory or novel D3/D2 pharmacologic selectivity was found with several benzamides, thioxanthenes, buspirone, GBR-12909, and DA agonists including hydroxyaminotetralins [ADTN, (+)-7-OH-DPAT, (−)-PPHT and its fluorescein derivative], (−)-N-propylnorapomorphine, (−)-3-PPP, (−)-quinpirole, and SDZ-205-502, but neither aminoergoline nor (+)-aporphine partial agonists. 4. The results extend pharmacologic characterization of D3-transfected cell membranes but fail to account for the high limbic anti-DA selectivity ofS-(+)-aporphines.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02090784
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