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1

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Comparative analysis of various proposed models of the receptor-bound conformation of H-tyr-Tic-Phe OH related δ-opioid antagonists (1995)

Wilkes, Brian C. ; Schiller, Peter W.

New York : Wiley-Blackwell

Biopolymers 37 (1995), S. 391-400

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A molecular mechanics study (grid search and energy minimization) was performed with six δ opioid peptide antagonists containing a tetrahydroisoquinoline-3-carboxylic acid (Tic) residue in the 2-position of the peptide sequence. Compounds examined were the highly potent and selective T1P(P) peptides H-Tyr-Tic-Phe-OH (TIP). H-Tyr-TicΨ[CH2-NH]Phe-OH (TIP[Ψ]). H-Tyr-Tic-Phe-Phe-OH (TIPP). and H-Tyr-TicΨ[CH2-NH]Phe-Phe-OH (TlPP[Ψ]), and the weakly active analogues H-Tyr-Tic-NH2 and H-Tyr-Tic-Ala-OH. Low energy conformers of the peptides were examined for their compatibility with three proposed model of the δ receptor-bound conformation. Model 1, based on spatial overlap of the Tyr1 and Phe3 aromatic rings and N-terminal amino group of the peptides with the corresponding aromatic rings and nitrogen atom of the nonpeptide δ-antagonist naltrindole, was ruled out because of the demonstrated importance of the Tic2 aromatic ring for δ antagonism and because of the somewhat elevated energies of the conformers consistent with this model. Models of the receptor-bound conformation based on superimposition of the Tyr1 and Tic2 aromatic rings and N-terminal amino group of the peptides with the corresponding moieties in naltrindole included an all-trans peptide bond conformer [model 2, proposed by B. C. Wilkes and P. W. Schiller (1994) Biopolymers. Vol. 34. pp. 1213-1219] and a conformer with a cis peplide bond between the Tyr1 and Tic2 residues (model 3), originally proposed by P. A. Temussi et al. [(1994) Biochemical and Biophysical Research Communications. Vol. 198, pp. 933-939]. For all six peptides low energy conformers consistent with both model 2 and model 3 were identified: however, peptide conformers corresponding to model 2 showed better coplanarity of the Tyr1 aromatic ring and the phenol ring in naltrindole than peptide conformers corresponding to model 3. Both models remain plausible candidate structures for the receptor-bound conformation of δ antagonists of the TIP(P) class. TIP(P) analogues containing additional conformational constraints need to be developed in order to arrive at a unique model. © 1994 John Wiley & Sons, Inc.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bip.360370606

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2

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Influence of sample pH on the conformational backbone dynamics of a pseudotripeptide (H-Tyr-TicΨ[CH2-NH] Phe-OH) incorporating a reduced peptide bond: An NMR investigation (1995)

Carpenter, K. A. ; Wilkes, B. C. ; Schiller, P. W.

New York : Wiley-Blackwell

Biopolymers 36 (1995), S. 735-749

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: In the present paper we investigate the influence of sample pH on the conformational and dynamical properties of the pseudotripeptide H-Tyr-TicΨ[CH2NH]Phe-OH(TIP[Ψ]:Tic: l, 2, 3, 4,-tetrahydroisoquinoline-3-carboxylic acid) using various one- and two-dimensional nmt techniques in conjunction with molecular modeling. Studies were conducted at three different pH levels-corresponding to the zwitterionic peptide containing a formal positive charge(pH 3. 1).the deprotonated molecule(pH 9. 1), and a situation at neutral pH(pH 7. 2) involving both protonated and deprotonated states of the reduced peptide bond. Analysis of the one-dimensional1H-nmr spectra reveals that in solution TIP[Ψ]is in slow dynamic exchange between conformations containing cis and trans configurations of the Tyr-Tic bond. An nmr pH dependence study of the cis:trans ratio indicated that the exchange process was governed by the protonation state of the reduced bond amine. From the nmr data, reduced peptide bond pKavalues of 6. 5 and 7. 5 were determined for the cis and trans conformers, respectively. It was concluded that conformations containing a trans Tyr-Tic bond are stabilized at law pH by an intramolecular hydrogen bond between the Tyr carbonyl and the reduced peptide bond protonated amine. This observation was corroborated by molecular mechanics investigations that revealed low energy trans structures compatible with nmr structural data, and furthermore, were consistently characterized by the existence of a strong N+ H-O= C interaction closing a seven-membered cycle. The dynamics of cis-trans isomerization about the Tyr-Tic peptide bond were probed by nmr exchange experiments. The selective presaturation of exchanging resonances carried out at several temperatures between 50 and 70°C allowed the determination of isomerization rate constants as well as thermodynamic activation parameters. ΔG≠ values were in close agreement with the cis → trans energy barrier found in X-Pro peptide fragments (∼83 kJ/mol).A large entropic barrier determined for the trans → cis conversion of TIP[Ψ](5. 7 JK-1 mol-1 at pH 3. 1; 6. 5 JK-1 mol-1 at pH 9. 1) is discussed in terms of decreased solvent molecular ordering around the conformers possessing a trans Tyr-Tic bond. Evidence that the neutral form of the reduced peptide bond gains rigidity upon protonation was obtained from relaxation measurements in the rotating frame. TJp measurements of several protons in the vicinity of the reduced peptide bond were made as a function of spin-lock field. Quantitative analysis of the relaxation data indicated that chemical shift fluctuations in the 10-4-10-5s range were more pronounced in the case of deprotonated TIP[Ψ]. Results of molecular dynamics simulations in addition to 3Jαβ coupling constant measurements support the experimentally observed greater flexibility in the C-terminal region of TIP[Ψ]. © 1995 John Wiley & Sons, Inc.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bip.360360607

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3

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Hydrophobic forces are responsible for the folding of a highly potent natriuretic peptide analogue at a membrane mimetic surface: An NMR study (1997)

Carpenter, Katharine A. ; Wilkes, Brian C. ; De Léan, André ; [et al.]

New York : Wiley-Blackwell

Biopolymers 42 (1997), S. 37-48

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ISSN: 0006-3525

Keywords: nuclear Overhauser effect distance constraints ; torsional angles ; molecular dynamics calculations ; conformational model of lipid-bound atrial natriuretic peptide analogue ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A conformational study by nmr spectroscopy was performed with the highly active 28-residue hybrid natriuretic peptide analogue pBNP1 [M. Mimeault, A. De Léan, M. Lafleur, D. Bonenfant, and A. Fournier (1995) Biochemistry, Vol. 34, pp. 955-964], which consists of the cyclic peptide core of pBNP32 and the N- and C-terminal exocyclic segments of rANP(99-126). In purely aqueous solution pBNP1 exhibits random coil behavior as evidenced by the almost complete absence of structurally significant nmr observables. By contrast, elements of secondary structure emerged upon the addition of dodecylphosphocholine micelles to the aqueous sample. Nuclear Overhauser effect distance-restrained molecular dynamics simulations in conjunction with torsional angle determinations permitted the generation of a reasonable model of the lipid-bound conformation of pBNP1. According to this model, pBNP1 adopts turn-like features in the cyclic and C-terminal regions of the peptide, but remains quite flexible in the N-terminal segment. Two hydrophobic cores separated by a hydrophilic cleft were also evident in the generated structure. A mechanism is proposed whereby the hydrophobic interactions necessary to stabilize a folded structure of pBNP1 are facilitated by the presence of the membrane-like polar/apolar interface provided by the phospholipid micelles. © 1997 John Wiley & Sons, Biopoly 42: 37-48, 1997

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

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4

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Ceramic films and coatings. J. B. Wachtman und R. A. Haber (Herausgeber), Published by Noyes Publications, 447 Seiten, Park Ridge, New Jersey, USA 1993, US $ 78.00, ISBN 0-8155-1318-6 (1997)

Schiller, W.

Weinheim [u.a.] : Wiley-Blackwell

Materials and Corrosion/Werkstoffe und Korrosion 48 (1997), S. 71-71

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ISSN: 0947-5117

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/maco.19970480113

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5

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Self-assembling of chain molecules in low dimensions: A Monte Carlo study (1995)

Stettin, Heiko ; Wahab, Mirco ; Schiller, Peter ; [et al.]

Weinheim : Wiley-Blackwell

Macromolecular Theory and Simulations 4 (1995), S. 1015-1037

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ISSN: 1022-1344

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: We studied the self-assembling of linear chain molecules in insoluble monolayers due to attractive interactions. We used lattice Monte Carlo simulations in a two-dimensional system. The molecules consist of segments occupying adjacent lattice sites. The head segments are confined to move along a line whereas the chain segments can arrange in a plane above the heads. Only one interaction parameter is applied. At high densities and small interaction energy the system shows percolation behavior. At moderate and small densities it can be characterized by a monotonous cluster size distribution. Self-assembling occurs at small densities for strong attractive interactions. The corresponding cluster size distributions indicate preferred cluster sizes which depend upon density and interaction strength. With increasing density the clusters grow. The internal cluster structure depends on the cluster size and the interaction parameter. The clusters tend to minimize their total energy. Molecules at cluster margins contribute less to the cluster energy and are mainly disordered. They cause that the cluster properties strongly depend on the cluster size. Large clusters only have minimum energy if the molecules in the cluster are in stretched-out conformation. With decreasing interaction strength the clusters get disordered thereby producing less energy-minimized domain boundaries.

Additional Material: 20 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/mats.1995.040040602

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6

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Enkephalin analogs containing 4,4-difluoro-2-aminobutyric acid: Synthesis and fluorine effect on the biological activity (1998)

Winkler, Dirk ; Sewald, Norbert ; Burger, Klaus ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Peptide Science 4 (1998), S. 496-501

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ISSN: 1075-2617

Keywords: enkephalins ; DPDPE ; opioid agonists ; δ-receptor ; fluorine containing amino acid ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Analogs of Met-enkephalin and [d-Pen2, d-Pen5]enkephalin (DPDPE) containing the partially fluorinated amino acid 4,4-difluoro-2-aminobutyric acid (DFAB) in the 2- or 3-position of the peptide sequence were synthesized and their opioid activities and receptor selectivities were determined in vitro. The linear fluorinated [d-DFAB2, Met5-NH2]enkephalin showed μ and δ agonist potencies comparable to those of natural [Leu5]enkephalin. The partially fluorinated DPDPE analogs behaved differently as compared with their non-fluorinated correlates. While l-amino acid substitution in position 3 of DPDPE usually resulted in higher δ agonist potency than d-amino acid substitution, [d-DFAB3]DPDPE turned out to be a more potent δ agonist than [l-DFAB3]DPDPE. Furthermore, [d-DFAB3]DPDPE showed over 100-fold higher δ agonist potency than [d-Abu3]DPDPE (Abu=2-aminobutyric acid), indicating that the fluorine substituents interact favorably with a δ opioid receptor subsite. © 1998 European Peptide Society and John Wiley & Sons, Ltd.

Additional Material: 4 Ill.

Type of Medium: Electronic Resource

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7

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Highly potent side chain-main chain cyclized dermorphin-deltorphin analogues: An integrated approach including synthesis, bioassays, NMR spectroscopy and molecular modelling (1995)

Ro, Seonggu ; Zhu, Qin ; Lee, Chang-Woo ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Peptide Science 1 (1995), S. 157-174

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ISSN: 1075-2617

Keywords: Opioid bioactivities ; bioactive conformations ; NMR studies ; molecular modelling ; synthesis of cyclic opioids ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Our continuing efforts to study structure-activity relationships of peptide opioids have resulted in the synthesis of a series of cyclic opioids related to dermorphins and deltorphins. The biological activities of the compounds have been determined and the conformational analyses carried out using 1H-NMR spectroscopy and molecular modelling. The three compounds in the series Tyr-c[D-Orn-Phe-Ala], Tyr-c[D-Lys-Phe-Ala], and Tyr-c[A2Bu-Phe-Ala-Leu] are cyclized via a lactam bridge from the side-chain of the residue at the second position with the carboxyl terminus of each compound. The molecules incorporate 12-, 13- and 14-membered rings, respectively. They include a phenylalanine at the third position which is a distinguishing characteristic of dermorphins and deltorphins. The guinea pig ileum and mouse vas deferens assays show that the compounds are highly active at both μ- and δ-opioid receptors. The compounds are all highly effective antinociceptive agents as measured by the intrathecal rat hot plate test. Conformational analyses of the molecules indicate that they can adopt topochemical arrays required for bioactivity at both μ- and δ-receptors which explains their high activity in both guinea pig ileum and mouse vas deferens in vitro assays. The results support our models for μ- and δ-receptor activity for constrained peptide opioids.

Additional Material: 5 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/psc.310010303

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8

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Synthesis of a novel side-chain to side-chain cyclized enkephalin analogue containing a carbonyl bridge (1997)

Pawlak, Danuta ; Chung, Ngoc Nga ; Schiller, Peter W. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Peptide Science 3 (1997), S. 277-281

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ISSN: 1075-2617

Keywords: cyclic opioid peptide analogue ; side-chain to side-chain cyclized peptides ; solid-phase peptide synthesis ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A novel type of cyclic opiod peptide analogue, cyclo(N∊,N∊′-carbonyl- D-Lys2,Lys5)enkephalinamide, was prepared from a linear precursor peptide. The peptide was synthesized on the Merrifield resin and also by a combination of the solid-phase technique and the classical method in solution. In both cases the cyclization was performed by reaction of bis(4-nitrophenyl)carbonate with the free side-chain amino groups of the two lysine residues. The described method permits the convenient preparation of novel peptide analogues cyclized via a ureido group incorporating the side-chain amino groups of two α,ω-diamino acid residues. The cyclic enkephalin analogue containing a 21-membered ring structure showed preference for μ over δ opioid receptors in opioid bioassays in vitro. © 1997 European Peptide Society and John Wiley & Sons, Ltd.

Additional Material: 1 Ill.

Type of Medium: Electronic Resource

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9

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Synthesis and bioactivity studies of 1-adamantanamine derivatives of peptides (1995)

Horvat, Štefica ; Varga-Defterdarovič, Lidija ; Horvat, Jaroslav ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Peptide Science 1 (1995), S. 303-310

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ISSN: 1075-2617

Keywords: 1-Adamantanamine ; peptide synthesis ; opioid compounds ; antiviral agents ; HIV-1 ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Small enkephalin-related peptides containing a 1-adamantanamine moiety coupled through an amide linkage at the C-terminus were synthesized. Several of the compounds showed high μ opioid activity and μ receptor selectivity. The new adamantanamine derivatives were also examined for antiviral activity against HIV-1 in a cell culture system. Some of them inhibited syncytia formation even when the antigen assay gave evidence for viral replication.

Additional Material: 3 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/psc.310010505

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