The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
A series of 13 enantiopure aryl benzyl sulfoxides (1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m) with different substituents on the two aromatic rings has been previously analyzed by means of electronic circular dichroism (CD) spectroscopy. Most of these compounds are crystalline and their X‐ray structure is established. For almost one‐half of the series, CD spectra measured in the solid state...
Linear electrogyration (electric field‐induced optical activity) and electro‐optic effects in x‐cut and z‐cut right‐handed (RH) α‐quartz were measured using a complete Mueller matrix polarimeter. The polarimeter used in the analysis was equipped with four photoelastic modulators operating at different frequencies. This configuration is especially sensitive due to the fidelity of the modulators and...
Here we present for the first time the experimental and theoretical (DFT/B3LYP/6‐311++G**) Raman optical activity (ROA) spectra of (−)‐R‐mevalonic acid as the δ‐lactone form in neat liquid and in the aqueous solution. Quantum chemical calculations show the conformational diversity of (−)‐R‐mevalonolactone originated from small energy differences between the various conformation of the six‐membered...
A chiral tetralin norsesquiterpenoid, ligukangtinol, was isolated from the plant Ligularia kangtingensis. Its planar structure was determined by extensive analysis of spectroscopic data (MS, IR, and NMR), and (1S,3R) absolute configuration of the tetralin ring was established by TDDFT‐ECD calculations of the solution conformers. Conformational analysis and ECD calculations proved that the semiempirical...
We present a detailed analysis of the molecular origin of the chiral sum frequency generation (SFG) signals of proteins and peptides at interfaces in the N‐H stretching vibrational region. The N‐H stretching can be a probe for investigating structural and functional properties of proteins, but remains technically difficult to analyze due to the overlapping with the O‐H stretching of water molecules...
Changes in vibrational circular dichroism (VCD) were recorded on‐line during a chemical reaction. The chiral complex nickel‐(–)‐sparteine chloride was hydrolyzed to free (–)‐sparteine base in a biphasic system of sodium hydroxide solution and chloroform (CHCl3). Infrared (IR) and VCD spectra were iteratively recorded after pumping a sample from the CHCl3 phase through a lab‐built VCD spectrometer...
For nuclear magnetic resonance (NMR)‐based protein structure determinations, the random coil chemical shifts are very important because the secondary and tertiary protein structure predictions become possible by examining deviations of measured chemical shifts from those reference chemical shift values. In addition, neighboring residue effects on chemical shifts and J‐coupling constants are crucial...
For three different chiroptical spectroscopic methods, namely, vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and Raman optical activity (ROA), the measures of similarity of the experimental spectra to the corresponding spectra predicted using quantum chemical theories are summarized. In determining the absolute configuration and/or predominant conformations of chiral molecules,...
Recent Raman and Raman optical activity (ROA) results have demonstrated that dimethyl sulfoxide (DMSO) induces the selective conversion of α‐helix motifs into the poly(L‐proline) II (PPII) helix conformation in an array of proteins, while β‐sheets remain mostly unaffected. Human serum albumin (HSA), a highly α‐helical protein, underwent the most dramatic changes and, therefore, was selected as a model...
The versatility and applicability of a time‐perturbed density functional method implemented within the SIESTA program package to calculate electronic circular dichroism of diverse nanoparticles is discussed. Results for nanostructures, such as fullerenes, single‐wall carbon nanotubes, as well as metallic nanoparticles composed of up to hundreds of atoms were examined by comparison with previously...
The chirality of stacked weakly interacting π‐systems was interpreted in terms of Frenkel exciton states and the formation of excitonic circular dichroism (CD) bands was monitored for ethylene stacks of varying sizes. Convergence of CD bands with respect to the system size was observed for stacks involving around 10 molecules. By means of rotation around the C–C double bond in ethylene, chirality...
An unprecedented complementarity of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectroscopic techniques is demonstrated by showing that each technique reveals the structure of a different molecular segment. Using a flexible molecule of biological significance we show that the synergetic use of ECD and VCD yields more complete structural characterization as it provides...
Chirality of amyloid fibrils‐linear beta‐sheet‐rich aggregates of misfolded protein chains‐often manifests in morphological traits such as helical twist visible in atomic force microscopy and in chiroptical properties accessible to vibrational circular dichroism (VCD). According to recent studies the relationship between molecular chirality of polypeptide building blocks and superstructural chirality...
Collecting circular dichroism (CD) spectra for protein solutions is a simple experiment, yet reliable extraction of secondary structure content is dependent on knowledge of the concentration of the protein—which is not always available with accuracy. We previously developed a self‐organizing map (SOM), called Secondary Structure Neural Network (SSNN), to cluster a database of CD spectra and use that...
We report in this work detailed measurements of the chiral and achiral sum‐frequency vibrational spectra in the C‐H stretching vibration region (2800–3050 cm‐1) of the air/liquid interfaces of R‐(+)‐limonene and S‐(−)‐limonene, using the recently developed high‐resolution broadband sum‐frequency generation vibrational spectroscopy (HR‐BB‐SFG‐VS). The achiral SFG spectra of R‐limonene and S‐limonene...
The enantiomeric separation ability of the newly prepared chiral stationary phases containing acridino‐18‐crown‐6 ether selectors was studied by high‐performance liquid chromatography (HPLC). The chiral stationary phases separated the enantiomers of selected protonated primary aralkylamines efficiently. The best results were found for the separation of the mixtures of enantiomers of NO2‐PEA. Chirality 26:651–654, 2014....
Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN1‐type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be...
A novel method was developed for the simultaneous determination of guaifenesin (GUA) and ketorolac tromethamine (KET) enantiomers in plasma samples. Since GUA probably increases the absorption of coadministered drugs (e.g., KET), it would be extremely important to monitor KET plasma levels for the purpose of dose adjustment with a subsequent decrease in the side effects. Enantiomeric resolution was...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.