Search results for "circular"

Characterization of gramicidin A in an inverted micellar environment. A combined high-performance liquid chromatographic and spectroscopic study

1992

We have investigated the conformational adaptability of gramicidin A incorporated into reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water, a so far unexplored "host" membrane-mimetic model system for this peptide. A high-performance liquid chromatographic strategy previously developed for the study of gramicidin in phospholipid vesicles and normal micelles [Bañó et al. (1989) FEBS Lett. 250, 67; Bañó et al. (1991) Biochemistry 30, 886] has been successfully extended to this system. The method has permitted the separation of peptide conformational species, namely, double-stranded dimers and monomers, and an accurate quantitation of their proportion in the invert…

Optical studies on interaction of biliary contrast agents with native and modified human serum albumin.

1981

The interaction of two homologous series of biliary contrast agents with native human and bovine serum albumin and with modified human serum albumin was investigated using circular dichroism and equilibrium dialysis. For most derivatives, extrinsic Cotton effects were observed for the interaction with both albumins. In some cases, these effects were strongly affected by only small changes in the chemical structure of the drugs. These large differences in extrinsic Cotton effects can be explained by definite effects of the chemical structures on the binding site selectivity of some drugs. For example, iopodate preferentially binds to the warfarin binding site of human Scrum albumin, while an…

Optical studies on the specific interaction of dipyridamole with alpha 1-acid glycoprotein (orosomucoid).

1982

Abstract The interaction of dipyridamole with α1-acid glycoprotein was investigated by circular dichroism and ultraviolet absorbance measurements as well as by equilibrium dialysis experiments. Dipyridamole is bound to the protein via one site of extremely high affinity and by at least one site of considerably lower affinity. Only the association of dipyridamole with the high affinity site produces typical extrinsic Cotton effects. As a result of experimental observations it is concluded that the high affinity site is located in a hydrophobic protein structure of the glycoprotein.

Design of Self-Assembling Peptides as Catalyst Mimetics Using Synthetic Combinatorial Libraries

2005

Sarcoehrenbergilides D–F: cytotoxic cembrene diterpenoids from the soft coral Sarcophyton ehrenbergi

2019

A solvent extract of the soft coral Sarcophyton ehrenbergi afforded cembrene diterpenoids, sarcoehrenbergilid D–F (1–3). Chemical structures were established by modern spectroscopic techniques with absolute stereochemistries determined by circular dichroism (CD) and time-dependent density functional theory electronic CD calculations (TDDFT-ECD). Cytotoxicity activities for 1–3 were evaluated against three human cancer cell lines: lung (A549), colon (Caco-2) and liver (HepG2).

Acid–base behaviour and binding to double stranded DNA/RNA of benzo[g]phthalazine-based ligands

2019

The affinity and the binding mode of two benzo[g]phthalazine compounds, functionalized with one or two 2-(imidazole-4-yl)-ethylamine groups, to DNA and RNA models have been evaluated by means of UV-Vis, fluorescence and circular dichroism (CD) spectroscopies in combination with viscometry and molecular dynamics. Both organic molecules bind strongly to all nucleic acid models via the intercalation mode in the duplex structure, especially compound 1. Intriguingly, 1 exhibits different emission responses depending on the base composition of duplex DNA/RNAs, which points out the possibility of using it as a base selective nucleic acid probe. Moreover, the acid-base behaviour of both compounds h…

Secondary structure conformation of hydroperoxide lyase from green bell pepper, cloned in Yarrowia lipolytica, and its activity in selected media

2008

International audience; Circular dichroism (CD) spectroscopy of secondary structure conformation of the purified green bell pepper hydroperoxide lyase (HPL), cloned in the yeast Yarrowia lipolytica, was investigated. The CD spectra of HPL in iso-octane, obtained at 60 °C, in the presence of the reducing agent dithiothreitol showed dramatic increase in α-helix content. The enzyme conformation remained unchanged over a range of pH values of 5.0–7.0. Using 13-hydroperoxide of linoleic acid (13-HPOD) as substrate, the biocatalysis of HPL in organic solvent media, including chloroform, dichloromethane, hexane, iso-octane, octane and toluene, was investigated. The results indicated an increase in…

Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment.

1991

We have investigated the conformation of gramicidin A reconstituted in different phospholipid environments, small unilamellar vesicles, extensive bilayers, and micelles by exploiting a recently proposed experimental approach based on high-performance liquid chromatography [Bano et al. (1988) J. Chromatogr. 458, 105; Bano et al. (1989) FEBS Lett. 250, 67]. The method allows the separation of conformational species of the peptide namely, antiparallel double-stranded (APDS) dimers and β 6.3 -helical monomers, and quantitation of their proportions in the lipid environment. Various experimental parameters (e.g., nature of organic solvent, time of incubation in organic solvent, lipid-to-peptide m…

Direct optical resolution of trans-dihydrodiol enantiomers of fjord-region polycyclic aromatic hydrocarbons by high-performance liquid chromatography…

1998

Abstract Enantioselective separation of trans -dihydrodiol metabolites of a series of fjord-region polycyclic aromatic hydrocarbons (PAHs), such as benzo[ c ]phenanthrene and dibenzo[ a , l ]pyrene, was evaluated by HPLC using commercially available cellulose-based CSPs as chiral columns. A baseline separation ( R s ≥1.6) with sharp, well-defined peaks of individual enantiomers was attained using cellulose-tris-( N -3,5-dimethylphenylcarbamate) and n -heptane-ethanol (9:1, v/v) as mobile phase. These chromatographic conditions permit a direct, simple and rapid (mostly within 30 min) enantiomeric resolution of PAH dihydrodiols. CD spectra were obtained for all optically pure enantiomers and …

The Interaction of Intravenous and Oral Biliary Contrast Agents with Serum Albumins

1978

The binding of two homologous series of oral and intravenous biliary contrast agents to human and bovine serum albumin was investigated using the gel filtration technique and circular dichroism measurements.