L. F. Galiullina

Structure of pravastatin and its complex with sodium dodecyl sulfate micelles studied by NMR spectroscopy

The aim of this work was to study the mechanisms of interaction between pravastatin and cell membranes using model membranes (sodium dodecyl sulfate micelles) by nuclear magnetic resonance spectroscopy methods. On the basis of the nuclear magnetic resonance experiments, it was established that pravastatin can form intermolecular complexes with sodium dodecyl sulfate micelles by the interaction of its hydrophilic groups with the polar surface of the micelle. Conformational features of pravastatin molecule were also studied. Copyright

Dynamic NMR study of cyclic derivatives of pyridoxine.

A series of pyridoxine derivatives was investigated by 1H and 2D nuclear overhauser enhancement spectroscopy (NOESY) NMR. The free energies of activation for the pyridyl‐oxygen rotation of the 2,4‐dinitrophenyl ether of the seven‐membered acetals of pyridoxine were measured by dynamic NMR. A conformational exchange between the chair and twist forms of the seven‐membered acetal ring was confirmed by dynamic NMR and STO3G computations. Copyright

Dynamic NMR study of dinitrophenyl derivatives of seven-membered cyclic ketals of pyridoxine

Two pyridoxine derivatives containing a dinitrophenyl moiety were investigated by 1H NMR spectroscopy. Conformational dynamics in solution were studied for each compound using dynamic NMR experiments. It was shown that both compounds studied are involved into two conformational exchange processes. The first process is a transformation of the seven‐membered cycle conformation between the enantiomeric P‐twist and M‐twist forms, and the second is a rotation of the dinitrophenyl fragment of the molecules around the C–O bond. Energy barriers of both conformational transitions were determined. Copyright

Interaction of different statins with model membranes by NMR data

Hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors or statins reduce the amount of low-density lipoprotein (LDL) cholesterol, which is known as a well-established risk factor for atherosclerosis. Despite the fact that statins have a common pharmacologic target essential to sterol biosynthesis, their efficacy, safety, and potential non-LDL actions vary significantly for different statins. There is a hypothesis that pharmacological features of statins depend on their location in cell membrane, but to the present day there is a lack of information in literature on interactions of statins with the surface of the cell membrane in liquid media. The results of NMR experiments showed that all studied statins form intermolecular complexes with models of cell membranes (dodecylphosphocholine micelles) in water solution. Locations of pravastatin, simvastatin, fluvastatin and cerivastatin on model membranes were established by NOESY NMR data. Distinctions in their positions can explain differences in pharmacological properties of studied compounds.

Stereodynamics of some pyridoxine derivatives.

The conformational properties of three pyridoxine derivatives were studied by 1H dynamic NMR spectroscopy. Conformational exchange caused by a rotation of 2‐nytrophenyl group around one single C–C bond, of 2,4‐dinitrophenyl substituent around two single C–O bonds, and twist‐twist transformations of the seven‐membered ketal cycle was observed by NMR experiments at low temperatures. Meanwhile, the conformational exchange of the acetal ring remains fast in the NMR timescale even at 198 K. The energy barriers for all observed conformational exchange processes were determined by the lineshape analysis of dynamic NMR spectra. The activation barriers of the 2‐nitrophenyl group rotation were almost the same for all studied compounds, about 40–41 kJ/mol. The energy barriers of the conformational exchange processes of the 2,4‐nitrophenyl group and the ketal cycle increased significantly up to 10 kJ/mol in comparison with previously studied compounds with similar structure. Copyright

Sulfur-Containing Monoterpenoids as Potential Antithrombotic Drugs: Research in the Molecular Mechanism of Coagulation Activity Using Pinanyl Sulfoxide as an Example

In this article we present the synthesis of enantiomerically pure sulfoxide and study the influence of this compound on hemostasis. Detailed NMR studies and molecular dynamics simulations using sodium dodecyl sulfate (SDS) membrane models indicated that the bicyclic fragment of sulfoxide was embedded into the SDS micelle whereas the -SO(CH2)2OH fragment remained on the surface of the micelle and was in contact with the solvent. We also found that the pro-coagulative activity of sulfoxide was due to its ability to inhibit platelet activation and inhibited the catalytic activity of phospholipid surface which was involved in formation of coagulation clotting factor complexes.

STATINS AND THEIR INTERACTION WITH MODEL CELL MEMBRANES ACCORDING TO THE DATA OF NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

Aim. To study the location of pravastatin, simvastatin, fluvastatin and cerivastatin in molecular complexes with model cell membranes based on dodecylphosphocholine, and also to calculate the average interatomic distances between the atoms of statins and micelles. Material and methods. Nuclear magnetic resonance (NMR) spectroscopy was chosen as a method of study. NMR spectroscopy of the Overhauser nuclear effect (NOESY) is one of the most effective methods in the study of intermolecular interactions, in particular, in studies of drugs. Information on the spatial structure of the molecular complex, as well as on the fragments of molecules responsible for the effective interaction leading to complex formation, was obtained by NOESY spectroscopy. All NMR experiments were performed on a Bruker Avance II 500 spectrometer with a 5 mm zgradient inverse sensor with the TOPSPIN software. The calculation of the interatomic distances was made with an accuracy of 0.1 A. Results. The location of pravastatin, simvastatin, fluvastatin and cerivastatin in molecular complexes with model cell membranes based on dodecylphosphocholine was determined based on NMR NOESY experiments. The average interatomic distances between the atoms of statins and micelles were also calculated. Pravastatin weakly binds to the polar surface of the model membrane, while simvastatin penetrates into the space between the hydrocarbon chains of the micelle. Fluvastatin interacts mainly with model membranes by penetration of its aromatic fragments into the surface of the micelle. Cerivastatin has a unique arrangement in the model membrane. It is located deep in the hydrophobic nucleus of the micelle close to the terminal methylene group. Conclusion: Even minor differences in the chemical structure of statins lead to different patterns of interaction with model membranes. These differences can explain the characteristics of the pharmacological properties of these substances.

A quantum chemical study of an interaction between collagen fragments and calcium ions using calculations of model complexes

Quantum chemical calculations revealed that the complexation between proline-containing collagen fragments and calcium ions involves a preferential interaction between Ca2+ ions and the oxygen and nitrogen atoms of proline in the glycine—proline—alanine fragment of the amino acid sequence of collagen.