The crystal structure of the conformationally constrained peptide Z-(Aib)6-OBut

Vlassi, Metaxia; Brueckner, Hans; Kokkinidis, Michael

doi:10.1524/zkri.1992.202.1-2.89

Cited by 8 publications

(11 citation statements)

References 2 publications

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“…Hexapeptide Z-(Aib) 6 -COO t Bu was crystallized from pentane/ethyl acetate, and the crystal structure, shown in Figure c as top and side views, indicates the expected 3 10 -helical structure and is consistent with the crystal structure of the same identical compound reported by others …”

Section: Resultssupporting

confidence: 85%

“…Hexapeptide Z-(Aib) 6 -COO t Bu was crystallized from pentane/ethyl acetate, and the crystal structure, shown in Figure 3c as top and side views, indicates the expected 3 10helical structure and is consistent with the crystal structure of the same identical compound reported by others. 45 The helical structure was persistent in organic solvents, as shown by the intramolecular H-bonding interactions in solution FTIR spectra of Z-(Aib) n -COO t Bu with n = 2, 3, and 6. The H-bonding interactions are expected to increase with the number of residues.…”

Section: ■ Introductionmentioning

confidence: 99%

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Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

et al. 2020

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The use of helical hexapeptides to establish a surface dipole layer on a TiO2 substrate, with the goal of influencing the energy levels of a coadsorbed chromophore, is explored. Two helical hexapeptides, synthesized from 2-amino isobutyric acid (Aib) residues, were protected at the N-terminus with a carboxybenzyl group (Z) and at the C-terminus carried either a carboxylic acid or an isophthalic acid (Ipa) anchor group to form Z-(Aib)6-COOH or Z-(Aib)6-Ipa, respectively. Using a combination of vibrational and photoemission spectroscopies, bonding of the two peptides to TiO2 surfaces (either nanostructured or single-crystal TiO2(110)) was found to be highly dependent on the anchor group, with Ipa establishing a monolayer much more efficiently than COOH. Furthermore, a monolayer of Z-(Aib)6-Ipa on TiO2(110) was exposed for different binding times to a solution of a zinc tetraphenylporphyrin (ZnTPP) derivative terminated with an Ipa anchor group (ZnTPP-P-Ipa). Photoemission spectroscopy revealed that ZnTPP-P-Ipa partly displaced Z-(Aib)6-Ipa, forming a coadsorbed monolayer on the oxide surface. The presence of the peptide molecular dipole shifted the HOMO levels of the ZnTPP group to lower energy by ∼300 meV, in accordance with a simple parallel plate capacitor model. These results suggest that a mixed-layer approach, involving coadsorption of a strong molecular dipole compound with a chromophore, is a versatile method to shift the energy levels of such chromophores with respect to the band edges of the substrate.

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Section: Resultssupporting

confidence: 85%

Section: ■ Introductionmentioning

confidence: 99%

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

et al. 2020

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“…This peptide possesses three complete turns, which seems to stabilize the internal structure. This is confirmed by thin layer chromatography experiments: in ethyl acetate (100%) and butyl acetate-methanol (98 : 2) the homopeptides with full turns (n = 5, 8,11) and N-terminal Z protection and C-terminal OtBu protection show relatively higher retention factor values compared with the homopeptides, which have one residue more or less [15]. In agreement, their melting point also shows higher values than the neighbouring peptides.…”

Section: Resultsmentioning

confidence: 57%

“…Peptides consisting of only Aib residues show a clear preference for left‐handed and right‐handed 3 10 ‐helices in solution and crystal structures. All crystal structures of Aib homopeptides known to date show the following common properties: centrosymmetric space group, regular 3 10 ‐helices with the maximum number of hydrogen bonds involving also the N ‐terminal protecting group, head‐to‐tail hydrogen‐bonded columns and a reversal of the helical sense at the C‐terminal residue. The latter was not observed for Z‐(Aib) 3 ‐OH anhydrate and monohydrate .…”

Section: Introductionmentioning

confidence: 99%

The crystal structure of Z‐(Aib)₁₀‐OH at 0.65 Å resolution: three complete turns of 3₁₀‐helix

Geßmann

Brückner

Petratos

2015

Journal of Peptide Science

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The synthetic peptide Z-(Aib)10-OH was crystallized from hot methanol by slow evaporation. The crystal used for data collection reflected synchrotron radiation to sub-atomic resolution, where the bonding electron density becomes visible between the non-hydrogen atoms. Crystals belong to the centrosymmetric space group P1. Both molecules in the asymmetric unit form regular 310 -helices. All residues in each molecule possess the same handedness, which is in contrast to all other crystal structure determined to date of longer Aib-homopeptides. These other peptides are C-terminal protected by OtBu or OMe. In these cases, because of the missing ability of the C-terminal protection group to form a hydrogen bond to the residue i-3, the sense of the helix is reversed in the last residue. Here, the C-terminal OH-groups form hydrogen bonds to the residues i-3, in part mediated by water molecules. This makes Z-(Aib)10-OH an Aib-homopeptide with three complete 310-helical turns in spite of the shorter length it has compared with Z-(Aib)11-OtBu, the only homopeptide to date with three complete turns.

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“…The two methyl groups attached to C~ are staggered with the methyl groups of residue n + 3 and N--H...O=C main-chain-main-chain hydrogen bonds are formed between residue n + 3 and n. The helical backbone shows the form of a regular triangular rod. In fact, all crystal structures of Aib homopeptides have common properties: centrosymmetric space group, one molecule in the asymmetric unit, a regular 310-helix with the maximum number of hydrogen bonds, including the N-terminal protection group, a reversal of the helical sense at the C-terminal residue and crystal packing in the form of head-to-tail hydrogen-bonded helical columns, most of which pack in an antiparallel fashion (Benedetti et al, 1982;Vlassi et al, 1992;Di Blasio et aL, 1991;Pavone et al, 1991;Vlassi et aL, 1993;Bavoso et al, 1986;Pavone et aL, 1990).…”

Section: Introductionmentioning

confidence: 99%

Structure of Z-(Aib)₉OBu^t

Geßmann¹,

Brückner²,

Kokkinidis³

1998

Acta Crystallogr Sect B

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The structure of the synthetic protected oligopeptide Z-(Aib)9OBu/, tert-butoxynona(ot-aminoisobutyric acid), which contains the unusual ct-aminoisobutyric acid (Aib), was determined by X-ray crystallography. The two independent molecules in the asymmetric unit fold into 310-helices, each stabilized by seven intramolecular hydrogen bonds. The C terminus of one of the molecules is disordered and adopts a semi-extended conformation, which is rather unusual for Aib residues. This is the first observation of such a conformation involved in a disorder in Aib-containing oligopeptides. The existence of a second conformation for the Cterminal residue might explain the difficulties in crystallizing the title compound and a different behaviour of the title compound in thin layer chromatography compared with the other homopeptides.

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The crystal structure of the conformationally constrained peptide Z-(Aib)₆-OBu^t

Cited by 8 publications

References 2 publications

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

The crystal structure of Z‐(Aib)₁₀‐OH at 0.65 Å resolution: three complete turns of 3₁₀‐helix

Structure of Z-(Aib)₉OBu^t

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The crystal structure of the conformationally constrained peptide Z-(Aib)6-OBut

Cited by 8 publications

References 2 publications

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides

The crystal structure of Z‐(Aib)10‐OH at 0.65 Å resolution: three complete turns of 310‐helix

Structure of Z-(Aib)9OBu t

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The crystal structure of the conformationally constrained peptide Z-(Aib)₆-OBu^t

The crystal structure of Z‐(Aib)₁₀‐OH at 0.65 Å resolution: three complete turns of 3₁₀‐helix

Structure of Z-(Aib)₉OBu^t