1. Preparations of Boc-Cys(S-Pyr)-OH and Z-Cys(S-Pyr)-OH and their applications in orthogonal coupling of unprotected peptide segments
H Huang, R I Carey J Pept Res. 1998 Apr;51(4):290-6. doi: 10.1111/j.1399-3011.1998.tb00426.x.
Boc-Cys(S-Pyr)-OH and Z-Cys(S-Pyr)-OH were prepared by addition of their cysteine derivatives to 3 equiv of 2,2'-dipyridyldisulfide in one portion. 2-Mercaptopyridine was removed by addition of 0.1 M Cu(NO3)2 to the solution. Both derivatives are white solids and can be used to facilitate the formations of heterodisulfide bonds. Two methods of synthesizing peptides with N-terminal Cys(S-Pyr) were also provided. Two peptide thiocarboxylic acids H-Tyr-Ser-Ala-Glu-Leu-Val-SH and H-Tyr-Ser-Ala-Glu-Leu-Gly-SH were prepared on the thioester benzhydryl resin with the cleavage condition of 1.0 M TFMSA/TFA instead of HF. From the orthogonal couplings of these peptides with H-Cys(S-Pyr)-Tyr-Ser-Glu-Leu-Ala-NH2, both intramolecular acyl transfers finished at pH 7 at about 15 to 20 min. The intermediate acyl disulfide peptide was collected by high-performance liquid chromatography and identified by liquid chromatography-mass spectrometry.
2. Delta opioidmimetic antagonists: prototypes for designing a new generation of ultraselective opioid peptides
S Salvadori, M Attila, G Balboni, C Bianchi, S D Bryant, O Crescenzi, R Guerrini, D Picone, T Tancredi, P A Temussi Mol Med. 1995 Sep;1(6):678-89.
Background: Tyr-Tic (1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) and Tyr-Tic-Ala were the first peptides with delta opioid antagonist activity lacking Phe, considered essential for opioid activity based on the N-terminal tripeptide sequence (Tyr-D-Xaa-Phe) of amphibian skin opioids. Analogs were then designed to restrain the rotational flexibility of Tyr by the substitution of 2,6-dimethyl-L-tyrosine (Dmt). Materials and methods: Tyr and Dmt peptides were synthesized by solid phase and solution methods using Fmoc technology or condensing Boc-Dmt-OH or Boc-Tyr(But)-OH with H-L-Tic-OBut or H-D-Tic-OBut, respectively. Peptides were purified (> 99%) by HPLC and characteristics determined by 1H-NMR, FAB-MS, melting point, TLC, and amino acid analyses. Results: H-Dmt-Tic-OH had high affinity (Ki delta = 0.022 nM) and extraordinary selectivity (Ki mu/Ki delta = 150,000); H-Dmt-Tic-Ala-OH had a Ki delta = 0.29 nM and delta selectivity = 20,000. Affinity and selectivity increased 8700- and 1000-fold relative to H-Tyr-Tic-OH, respectively. H-Dmt-Tic-OH and H-Dmt-Tic-NH2 fitted one-site receptor binding models (eta = 0.939-0.987), while H-Dmt-Tic-ol, H-Dmt-Tic-Ala-OH and H-Dmt-Tic-Ala-NH2 best fitted two-site models (eta = 0.708-0.801, F 18.9-26.0, p < 0.0001). Amidation increased mu affinity by 10- to 100-fold and acted synergistically with D-Tic2 to reverse selectivity (delta-->mu). Dmt-Tic di- and tripeptides exhibited delta antagonist bioactivity (Ke = 4-66 nM) with mouse vas deferens and lacked agonist mu activity (> 10 microM) in guinea-pig ileum preparations. Dmt-Tic analogs weakly interacted with kappa receptors in the 1 to > 20 microM range. Conclusions: Dmt-Tic opioidmimetic peptides represent a highly potent class of opioid peptide antagonists with greater potency than the nonopioid delta antagonist naltrindole and have potential application as clinical and therapeutic compounds.
3. Cyclosporin H, Boc-MLF and Boc-FLFLF are antagonists that preferentially inhibit activity triggered through the formyl peptide receptor
Anna-Lena Stenfeldt, Jennie Karlsson, Christine Wennerås, Johan Bylund, Huamei Fu, Claes Dahlgren Inflammation. 2007 Dec;30(6):224-9. doi: 10.1007/s10753-007-9040-4. Epub 2007 Aug 9.
In order to properly interpret receptor inhibition experiments, the precise receptor specificities of the employed antagonists are of crucial importance. Lately, a great number of agonists for various formyl peptide receptors have been identified using a selection of antagonists. However, some confusion exists as to the precise receptor specificities of many of these antagonists. We have investigated the effects of formyl peptide receptor family antagonists on the neutrophil response induced by agonists for the formyl peptide receptor (FPR) and the formyl peptide receptor like 1 (FPRL1). To determine FPR- and FPRL1-specific interactions, these antagonists should not be used at used at concentrations above 10 microM. Signaling through FPR was inhibited by low concentrations of the antagonists cyclosporin H, Boc-MLF (also termed Boc-1), and Boc-FLFLFL (also termed Boc-2), while higher concentrations also partly inhibited the signaling through FPRL1. The antagonist WRWWWW (WRW(4)) specifically inhibited the signaling through FPRL1 at low concentrations but at high concentrations also partly the signaling through FPR. Based on the difference in potency of cyclosporin H and the two Boc-peptides, we suggest using cyclosporin H as a specific inhibitor for FPR. To specifically inhibit the FPRL1 response the antagonist WRW(4) should be used.
