Designed β-hairpin peptides with defined tight turn stereochemistry

The conformational analysis of two synthetic octapeptides, Boc-Leu-Val-Val-D-Pro-L-Ala-Leu-Val-Val-OMe (1) and Boc-Leu-Val-Val-D-Pro-D-Ala-Leu-Val-Val-OMe (2) has been carried out in order to investigate the effect of β-turn stereochemistry on designed β-hairpin structures. Five hundred megahertz 1H NMR studies establish that both peptides 1 and 2 adopt predominantly β-hairpin conformations in methanol solution. Specific nuclear Overhauser effects provide evidence for a type II′ β-turn conformation for the D-Pro-L-Ala segment in 1, while the NMR data suggest that the type I D-Pro-D-Ala β-turn conformation predominates in peptide 2. Evidence for a minor conformation in peptide 2, in slow exchange on the NMR time scale, is also presented. Interstrand registry is demonstrated in both peptides 1 and 2. The crystal structure of 1 reveals two independent molecules in the crystallographic asymmetric unit, both of which adopt β-hairpin conformations nucleated by D-Pro-L-Ala type II′ β-turns and are stabilized by three cross-strand hydrogen bonds. CD spectra for peptides 1 and 2 show marked differences, presumably as a consequence of the superposition of spectral bands arising from both β-turn and β-strand conformations

Synthesis and characterization of dioxouranium (VI) complexes of schiff bases derived from isatin, isovanillin and <i>o</i>-vanillin

66-68Three schiff bases viz. isatin semicarbazone, isovanillin thiosemicarbazone, o-vanillin para-anisidineand their dioxouranium(VI) complexes have been synthesised and characterized by elemental analysis, IR and NMR spectral studies

De novo design of a five-stranded β-sheet anchoring a metal-ion binding site

A five-stranded β-sheet bearing two histidine residues as part of a metal-binding site has been designed, synthesised and characterised using NMR and electrospray ionization mass spectrometry techniques

Studies on arylfuran derivatives: Part IX-Synthesis and characterization of some fluorine containing arylfurylvinylquinazolinones as possible antibacterial agents

343-34

Fully Deuterated Magnetically Oriented System Based on Fatty Acid Direct Hexagonal Phases

There is strong demand in the field of NMR for simple oriented lipid supramolecular assemblies, the constituents of which can be fully deuterated, for specifically studying the structure of host protonated molecules (e.g., peptides, proteins...) in a lipid environment. Also, small-angle neutron scattering (SANS) in fully deuterated oriented systems is powerful for gaining information on protonated host molecules in a lipid environment by using the contrast proton/deuterium method. Here we report on a very simple system made of fatty acids (dodecanoic and tetradecanoic) and ethanolamine in water. All components of this system can be obtained commercially as perdeuterated. Depending on the molar ratio and the concentration, the system self-assembles at room temperature into a direct hexagonal phase that is oriented by moderate magnetic fields of a few tesla. The orientation occurs within the magnetic field upon cooling the system from its higher-temperature isotropic phase: the lipid cylinders of the hexagonal phase become oriented parallel to the field. This is shown by solid-state NMR using either perdeuterated fatty acids or ethanolamine. This system bears strong interest for studying host protonated molecules but also in materials chemistry for building oriented solid materials