The Effect of Nitroxyalkyl Succinimides on Activity of Cyclic Guanosine Monophosphate Phosphodiesterase.

The effect of N-nitroxymethyl succinimide (1), N-(2-nitroxyethyl) succinimide (2) and N-(3-nitroxypropyl) succinimide (3) on enzymatic activity of cyclic guanosine monophosphate (cGMP) phosphodiesterase was studied and crystal structure of compound (2) was determined. It was shown that all studied N-nitroxy succinimides inhibited cGMP phosphodiesterase in a concentration range of 0.1-0.001 mM. Compound (2) noncompetitively and reversibly inhibited hydrolytic function of enzyme with Ki=1.7×10-5 М. Inhibition constant for the reference compound N-(2-nitroethyl) nicotinamide (nicorandil) was 3×10-5 М.

Membranotropic and Antiradical Properties of 2-Nitroxysuccinate 3-Hydroxy-6-Methyl-2-Ethylpyridine.

We studied membranotropic properties of NO donor 2-nitroxysuccinate 3-hydroxy-6-methyl-2-ethylpyridine and its structural analog succinate 3-hydroxy-6-methyl-2-ethylpyridine (Mexidol). It was shown that the compounds under study are incorporated into modeled membranes and form long-living complexes with pyrene in the region of fatty acid tails of phospholipids. Luminol-amplified chemiluminescence analysis showed that both compounds exhibited antiradical activity and in a concentration of 0.1 mM reduced chemiluminescence intensity by more than 70%. 2-Nitroxysuccinate 3-hydroxy-6-methyl-2-ethylpyridine inhibited catalytic activity of monoamine oxidase A more efficiently than its structural analogue Mexidol.

[Prediction of Protein Conformational Mobility and Evaluation of Its Reliability Using Small-Angle X-ray Scattering].

The "coarse-grained" model of protein conformational mobility is presented. We compared the trajectories of conformational motions predicted for five proteins using this model with the motion obtained by the method of the "nearest neighbor", based on small-angle X-ray scattering data. It is shown that for all studied proteins the sequence of conformations calculated on the basis of "coarse-grained" model and on the basis of the "nearest neighbor", coincides well, although there are exceptions. Some separate consideration should be given to each protein to discern the causes of these exceptions.

[Efficacy and safety of rivastigmine (exelon) in the confusion syndrome in the acute phase of ischemic stroke].

There is ample evidence that the poststroke confusion syndrome or delirium is a manifestation of cholinergic deficit. Given this conception, we conducted a controlled study of efficacy and safety of acetylcholinesterase inhibitor rivastigmine in patients developed a delirium in the acute phase of ischemic stroke. The study included 224 consecutive stroke patients: 68 patients developed a delirium in the acute phase of disease. Severity of delirium was scored with the Delirium Rating Scale (DRS). A main group included 21 patients with delirium treated with rivastigmine in individually tailored doses. A control group included 47 patients with delirium who received only vascular and anticoagulant treatment, i.e. haloperidol. Cognitive functions were tested 3 and 6 months after stroke with the MMSE, the FAB, the Luria 10 point verbal test. The Zarit Burden Interview (ZBI) was used after 3 and 6 months to measure caregiver burden. In patients treated with rivastigmine, the delirium phase was significantly shorter (p<0,001) compared to the control group. In patients without delirium in the acute phase of stroke, the results of neuropsychological study were better (p<0,001) than in patients with delirium. Total ZBI scores were more favorable in the rivastigmine group than in the control one (p<0,05). To the end of the study, 5 patients died in the rivastigmine group, 17 patients in the control group and 3 patients in the group without delirium. Rivastigmine was safe in the acute phase of stroke patients even after the rapid titration.

[Modulation of reactivity of cyclic adenosine monophosphate phosphodiesterase under the effect of pyridinecarboxylic acid derivatives and Pt(IV) metal complexes on their basis].

The effect of substituted nicotinamides and isonicotinamides and Pt(IV) metal complexes based on the substituted nicotinamides and isonicotinamides on the activity of cAMP phosphodiesterase was studied. Isonicotinamide derivatives are efficient enzyme activators, whereas substituted nicotine amides are inhibitors of enzymatic cAMP phosphodiesterase activity; their inhibitory potency is comparable to that of theophylline used as a reference drug.

[Inhibition of active transport of calcium ions by PT(IV) and PD(II) metal complexes. Correlation between the process and antimetastatic action of drugs].

Newly synthesized compounds, namely, platinum and palladium metal complexes based on substituted pyridinecarboxylic acids inhibit both active transport of Ca ions and hydrolysis of ATP, catalyzed by sarcoplasmic reticulum Ca(2+)-ATPase. The degree of active transport of Ca ions to vesicles correlated to the inhibition of metastases of experimental melanoma B16 by compounds studied. We suggest that the mechanism responsible for inhibition of metastases by newly synthesized compounds consists in change of normal ratio of extra- and intracellular content of Ca2+ ions that influences platelet aggregation, required for adhesion of metastasizing tumor cells to vascular walls.

DNA-phospholipid recognition: modulation by metal ion and lipid nature. Complexes structure and stability calculated by molecular mechanics.

The structures and formation energies of nucleic acid-phospholipid complexes both in the absence and in the presence of Mg(2+) ions were calculated taking double-stranded trinucleoside diphosphates NpNpN or heptanucleotides ApAp(NpNpN)pApA, composed of 64 possible combinations of genetic code, and phosphatidylcholine (PC) and sphingomyelin (SM) as model compounds. The dependence of intramolecular interactions on the primary structure of nucleic acid molecules and on the presence of a cationic bridge was revealed. The formation energies and structure of oligonucleotides were found by molecular mechanics calculations with the AMBER force field. The structures of phospholipid and MgCl(2) molecules were calculated by the semiempirical PM3 method, while the energies of phospholipid-oligonucleotide complexes were calculated by the molecular mechanics method. Calculations of complexes were carried out with consideration of solvation effects. Considerable gain in the formation energy of triple complexes is achieved due to the presence of the electroneutral metal bridge. A tendency toward increasing the stability of "triple" PC complexes (but not SM ones), containing guanosine- and cytidine-enriched triplets was revealed. Depending on the structure of NpNpN trinucleotides, the formation energy values of NpNpN-MgCl(2)-PC and ApAp(NpNpN)pApA-MgCl(2)-PC complexes differ by 1.7-2.6 kcal mol(-1), which can be considered as the atomic-scale manifestation of the recognition phenomenon. Presence of metal (II) ion bridge results in a greater stabilization of the phospholipid-nucleic acid complexes for SM in comparison to PC (the total energy difference equals to 4-16 kcal mol(-1)). Depending on the structure of NpNpN trinucleotides, the formation energies of NpNpN-MgCl(2)-SM and ApAp(NpNpN)pApA-MgCl(2)-SM complexes differ by 1.7-2.1 kcal.mol(-1), which is essential at physiological conditions and can also be considered as the recognition effect.

Closed mitral commissurotomy in Archangel, Northern Russia, 1965-1993. Operative assessment of 367 patients operated on for rheumatic mitral stenosis.

OBJECTIVE: Preoperative and operative assessment of the 367 patients operated on for rheumatic mitral stenosis with closed mitral commissurotomy (CMC) at the regional hospital in Archangel, northwest Russia, between 1965 and 1993. DESIGN: Retrospective survey. RESULTS: Mean age at first attack of rheumatic fever was 15 years +/- 1.09 years. Mean age at time of surgery was 33.4 years +/- 0.92. Preoperatively, most patients (67%, n = 245) were in New York Heart Association stage III; 29% (n = 107) in stage IV. Digital commissurotomy alone was performed in 16% (n = 57) and a transventricular dilator was used in 84% (n = 310). Operative blood loss was average (384.4 ml +/- 34 ml); 20% (n = 73) developed wound infection, 21% (n = 77) pericarditis. In-hospital stay was above 50 days for both sexes. In-hospital mortality was 1.6% (n = 6). CONCLUSION: Rheumatic heart disease developed rapidly in these patients. CMC has a place as a low cost treatment of mitral stenosis when a heart lung machine is not available.

Stress under normal conditions, hypokinesia simulating weightlessness, and during flights in space.

Stress due to intensive mental work under normal conditions was compared to stress under a sharp limitation of motor activity (hypokinesia), simulating weightlessness on the human body. Mental stress causes typical alterations of cerebral circulation under normal conditions: increase of blood flow in the supramarginal and angular gyri of the parietal lobe, in the frontal lobe, and in the superior temporal gyrus of the left hemisphere, and changes in cardiac activity and in the tonus of vessels. Dynamics of human stress reactions, among other features of this process, is best reflected in the parameters of a electrocardiogram, a rheoencephalogram, and total peripheric vascular resistance. An increase in the latter is an informative index of stress development. Human reaction to stress under hypokinesia and during flights in space have specific features. Prolonged hypokinesia causes an imbalance in an organism's control systems, specifically depressor reactions are distorted. In the context of hypokinesia, anxiety and mental stress lose their adaptive nature to a large extent. They provoke disturbances of the heartbeat and hypertensive reactions. A whole complex of factors affects the living organism during space flights. An imbalance of the body's control systems, emotional and physical overloads, which arise episodically, changes in electrolyte and energetic metabolism, and alterations in the head vessels increase the probability of reactions to stress and reinforce their effect. Stress can be retarded by using on elaborated system of preventive measures which includes physical training, psychological support of astronauts and, to some degree, reduction of the hypothalamus adrenergic centers' tonus through muscle relaxation. Astronauts' reactions to being in space occur during flights under heavy loading tests and in emergency situations. Weightlessness does not generate stress when one has adapted to it. Returning from weightlessness to the Earth's gravitation causes stress. After prolonged flights, stress associated with readaptation to the Earth's gravitation is atypical in character (increase of sympatoadrenalic system activity against the background of a reduction in hypothalamo-hypophysial system activity). We explain the voltage decrease of the T-wave of the electrocardiogram, the phenomenon repeatedly occurring both during prolonged space flights and under hypokinesia, by a lowering of cardiomyocytes, energetic potential due to hypokalemia, insufficient glucose usage, and a decrease in the coupling of oxidative phosphorylation processes. [Translated from Fiziologiya Cheloveka, vol. 22, no. 2, 1996, p. 10-19]

Artificial protein vaccines with predetermined tertiary structure: application to anti-HIV-1 vaccine design.

A successful approach to the development of a safe and effective synthetic vaccine requires that different B and T cell epitopes of the infectious agent be included in the vaccine construction. In this paper we suggest a new approach to vaccine design in the form of an artificial protein with a predetermined tertiary structure (PTS vaccines). Based on B and T cell epitope properties, we substantiate the possible use for vaccine construction of one well-known protein spatial motif--the four-alpha-helix bundle. Antigenic determinants of cellular immunity (amphipathic alpha-helices) and humoral immunity (flexible hydrophilic loop regions) are used as blocks for vaccine design. General principles of PTS vaccine construction have been applied to anti-HIV-1 vaccine design.

[The effect of fixed water molecules on fractal properties of globular protein surfaces]. / Vliianie fiksirovannykh molekul body na fraktal'nye svoistva poverkhnostei globuliarnykh belkov.

On the base of the technique developed by the authors together with Schmidt the fractal properties of the 17 globular proteins have been analysed using the crystal structure data at high resolution. For all the proteins there are the coordinates of fixed water molecules in the protein data bank. For each protein the fractal dimension of its surface D has been calculated with and without taking into account the fixed water molecules located inside a 3-Angstrom hydrated layer. Small but systematic decrease of the DS values for the proteins with the fixed water molecules has been demonstrated. It means that the fixed water molecules tend to fill gaps on the protein surfaces and in that way to smooth the surfaces. The volumes and the molecular surfaces of the proteins have been also calculated on the base of the cube technique. The molecular surfaces of the proteins with the fixed water molecules prove to decrease. This fact can be considered as the indirect evidence that the protein surfaces become to be smoother.

Comparative study of thermostability and structure of close homologues--barnase and binase.

Parameters of heat denaturation and intrinsic fluorescence of barnase and its close homologue, binase in the pH region 2-6 have been determined. The barnase heat denaturation (pH 2.8-5.5) proceeds according to the "all-or-none" principle. Barnase denaturation temperature is lower than that of binase and this difference increases from 2.5 degrees C at pH 5 to 7 degrees C at pH 3. Enthalpy values of barnase and binase denaturation coincide only at pH 4.5-5.5, but as far as pH decreases the barnase denaturation enthalpy decreases significantly and in this respect it differs from binase. The fluorescence and CD techniques do not reveal any distinctions in the local environment of aromatic residues in the two proteins, and the obtained difference in the parameters of intrinsic fluorescence is due to fluorescence quenching of the barnase Trp94 by the His 18 residue, absent in binase. Secondary structures of both native and denaturated proteins also do not differ. Some differences in the barnase and binase electrostatic characteristics, revealed in the character of the dipole moments distribution, have been found.

[Comparison of the heat stability and structure close homologs--Bacillus amyloliquefaciens ribonuclease and Bacillus intermedius 7P ribonuclease]. / Sravneniee termostabil'nosti i struktury blizkikh gomologov-- ribonukleazy Bacillus amyloliquefaciens i ribonukleazy Bacillus intermedius 7P.

Parameters of heat denaturation and intrinsic fluorescence of barnase and its close homologue, binase, in the pH region 2-6 have been determined. Barnase heat denaturation (pH 2.8-5.5) proceeds according to the "all-or-none" principle. Barnase denaturation temperature is lower than that of binase and this difference increases from 2.5 degrees C at pH 5 to 7 degrees C at pH 3. Enthalpy values of barnase and binase denaturation coincide only at pH 4.5-5.5, but as the pH decreases the barnase denaturation enthalpy decreases significantly and in this respect it differs from binase. The fluorescence and CD techniques do not reveal any distinctions in the local environment of aromatic residues in the two proteins, and the obtained difference in the parameters of intrinsic fluorescence is due to fluorescence quenching of the barnase Trp-94 by the His-18 residue, which is absent in binase. Secondary structures of both native and denaturated proteins also do not differ. Some differences have been found in the barnase and binase electrostatic characteristics, revealed in the character of the dipole moment distribution.