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1
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DALDA analogues containing α-hydroxymethylamino acids.

100%
Olma A., Chung N. N., Schiller P. W., Zabrocki J.
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2001
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vol. 48
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issue 4
1121-1124
EN
To evaluate the role of aromatic amino-acids residues, four analogues of the μ-selec-tive opioid peptide agonist DALDA (H-Tyr-D-Arg-Phe-Lys-NH2) containing the amphiphilic, α,α-disubstituted amino acid (R)- or (S)-α-hydroxymethyltyrosine (HmTyr) in position 1 and (R)- or (S)-α-hydroxymethylphenylalanine (HmPhe) in position 3 of the peptide sequence were synthesized. Only the [(R)-HmPhe3)]DALDA analogue displayed full agonistic activity in both the guinea pig ileum and the mouse vas deferens assays and turned out to be a δ receptor-selective opioid agonist.
2
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Cyclic dermorphin tetrapeptide analogues obtained via ring-closing metathesis

100%
Berezowska I., Chung N. N., Lemieux C., Wilkes B. C., Schiller P. W.
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2006
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vol. 53
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issue 1
73-76
EN
The dermorphin-derived cyclic tetrapeptide analogues H-Tyr-c[d-Cys-Phe-Cys]NH2 and H-Tyr-c[d-Cys-Phe-D-Cys]NH2 are opioid agonists at the µ and δ receptor. To enhance the metabolic stability of these peptides, we replaced the disulfide bridge with a bis-methylene moiety. This was achieved by solid-phase synthesis of the linear precursor peptide containing allylglycine residues in place of the Cys residues, followed by ring-closing metathesis. In the case of the peptide with L-configuration in the 4-position both the cis and the trans isomer of the resulting olefinic peptides were formed, whereas the cis isomer only was obtained with the peptide having the d-configuration in position 4. Catalytic hydrogenation yielded the saturated -CH2-CH2- bridged peptides. In comparison with the cystine-containing parent peptides, all olefinic peptides showed significantly reduced µ and δ agonist potencies in the guinea pig ileum and mouse vas deferens assays. The -CH2-CH2-bridged peptide with l-configuration in the 4-position was equipotent with its cystine-containing parent in both assays, whereas the bis-methylene analogue with d-configuration in position 4 was 10-27-fold less potent compared to its parent. The effect of the disulfide replacements with the -CH=CH- and-CH2-CH2- moieties on the conformational behavior of these peptides was examined by theoretical conformational analysis which provided plausible explanations in terms of structural parameters for the observed changes in opioid activity.
3
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Variation in the analgesic activity of opioid peptide fragments in correlation with the amino acidic sequence

100%
Jaba I., Tamba B., Manolidis G., Mungiu O.
Open Medicine
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2007
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vol. 2
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issue 4
417-429
EN
Short fragments of typical or atypical opioid peptides, lacking the whole four amino acid sequence of the enkephalin motif, can preserve a significant percentage of the analgesic activity of the original peptides. This paper investigates the importance of the amino-acidic sequence of minimum structure typical opioid peptides for the analgesic activity. Different groups of rats were treated with 1) Gly-Tyr, 0.5 mg/rat i.t., 2) Tyr-Gly, 0.5 mg/rat i.t., 3) Tyr-Gly-Gly, 0.5 mg/rat i.t., 4) Gly-Gly-Phe-Leu, 0.5 mg/rat i.t., 5) Leu-enkephalin, 0.5 mg/rat i.t.. The analgesic effect of the tested substances was appreciated through the nociceptive threshold for thermal (plantar test) and mechanical nociception (algesimetric test). Fragments of typical opioid peptides elicited antinociceptive activity only when a tyrosine residue was present at the N-terminal end of the amino-acidic sequence. The presence of Nterminal tyrosine provides affinity for the opioid receptors and significant analgesic activity. The intensity of the antinociceptive effect was directly proportional with the length of the amino-acidic sequence. The inhibition of the analgesic effect by previous administration of naloxone proves that this effect is mediated through the opioid system.
4
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Synthesis and binding properties of deltorphin I analogues containing (R) and (S)-α-hydroxymethylnaphtylalanine.

86%
Olma A., Gniadzik A., Lipkowski A. W., Łachwa M.
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2001
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vol. 48
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issue 4
1165-1168
EN
New analogues of deltorphin I (DT I), in which the phenylalanine residue in position 3 is substituted with amphiphilic α,α-disubstituted amino acid enantiomers, (R) and (S)-α-hydroxymethylnaphtylalanine, were synthesized and tested for μ and δ opioid receptor affinity and selectivity. Although both analogues have lower affinity to δ receptors than DT I, they both expressed specificity to δreceptors.
5
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Dansylated analogues of the opioid peptide [Dmt1]DALDA: in vitro activity profiles and fluorescence parameters.

86%
Berezowska I., Lemieux C., Chung N. N., Zelent B., Schiller P. W.
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vol. 51
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issue 1
107-113
EN
Dansylated analogues of the potent and selective μ opioid peptide agonist [Dmt1]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2; Dmt = 2',6'-dimethyltyrosine) were prepared either by substitution of Nβ-dansyl-α,β-diaminopropionic acid or Nε-dansyllysine for Lys4, or by attachment of a dansyl group to the C-terminal carboxamide function via a linker. All three analogues displayed high μ agonist potency in vitro and the C-terminally dansylated one retained significant μ receptor selectivity. The three analogues showed interesting differences in their fluorescence emission maxima and quantum yields, indicating that the dansyl group in two of them was engaged in intramolecular hydrophobic interactions. These dansylated [Dmt1]DALDA analogues represent valuable tools for binding studies, cellular uptake and intracellular distribution studies, and tissue distribution studies.
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