19F electron nuclear double resonance (ENDOR) spectroscopy for distance measurements using trityl spin labels in DNA duplexes.

The combination of fluorine labeling and pulsed electron-nuclear double resonance (ENDOR) is emerging as a powerful technique for obtaining structural information about proteins and nucleic acids. In this work, we explored the capability of Mims 19F ENDOR experiments on reporting intermolecular distances in trityl- and 19F-labeled DNA duplexes at three electron paramagnetic resonance (EPR) frequencies (34, 94, and 263 GHz). For spin labeling, we used the hydrophobic Finland trityl radical and hydrophilic OX063 trityl radical. Fluorine labels were introduced into two positions of a DNA oligonucleotide. The results indicated that hyperfine splittings visible in the ENDOR spectra are consistent with the most populated interspin distances between 19F and the trityl radical predicted from molecular dynamic (MD) simulations. Moreover, for some cases, ENDOR spectral simulations based on MD results were able to reproduce the conformational distribution reflected in the experimental ENDOR line broadening. Additionally, MD simulations provided more detailed information about the melting of terminal base pairs of the oligonucleotides and about the configuration of the trityls relative to a DNA end.

Application of W-band 19F electron nuclear double resonance (ENDOR) spectroscopy to distance measurement using a trityl spin probe and a fluorine label.

Recently, Marina Bennati and coworkers (M. Bennati et al., Angew. Chem., Int. Ed., 2020, 59, 373-379., M. Bennati et al., J. Magn. Reson., 2021, 333, 107091) proposed to use electron nuclear double resonance (ENDOR) spectroscopy in the W-band for a pair of labels, nitroxide and 19F, for measurements of short (0.5-1.0 nm) distances in biomolecules. In our paper, we investigated the suitability of high-field ENDOR spectroscopy in the W-band for pairs of triarylmethyl and fluorine labels using five newly synthesized model compounds. It is shown that the application of strong magnetic fields allows distinguishing nuclear frequencies of 19F and protons with sufficient resolution. On the one hand, in contrast to nitroxides, for triarylmethyl radicals, it is not necessary to obtain spectra in different orientations owing to low g-factor anisotropic and long electron spin relaxation times of triarylmethyls. On the other hand, the size of the triarylmethyl radical is substantially larger than that of nitroxide and comparable with measured distances. We theoretically analyzed the suitability of the dipole-dipole approach for triarylmethyl to be used in a 19F ENDOR experiment and determined limitations of this approach. Finally, for comparison, we performed paramagnetic relaxation enhancement (PRE) NMR on the same compounds. In addition, we applied this approach to study the process of a thiol exchange between molecules of triarylmethyl-labeled and 19F-labeled human serum albumin (HSA).

Crystal environment of impurity Nd3+ ion in yttrium and scandium orthosilicate crystals.

The ESEEM spectroscopy was used to determine positions of the 143Nd3+ impurity ions in Y2SiO5 single crystal. It is established that neodymium ions substitute yttrium ions in the Y2 positions with seven nearest oxygen ions. Crystal field parameters of 143Nd3+ impurity centers in isotopically pure Y228SiO5 and Sc228SiO5 single crystals were determined using data of CW EPR spectroscopy and the known energy level schemes.

Structure and magnetic properties of nanostructured Pd-Fe thin films produced by pulse electrodeposition.

Nanostructured Pd-Fe thin films with varied Fe content were prepared by electrodeposition technique from organic electrolytes on Cu and brass substrates. The structure and the magnetic properties of the films were investigated prior to post-deposition annealing. The structure of the Pd1-xFe(x) thin film with x = 0.14, 0.24, and 0.52 was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) as a solid solution of iron in palladium face-centered cubic lattice with the (111) orientation of nanograins relatively to the substrate surface. The films with higher iron concentration, x = 0.74, 0.91, have structure of a solid solution based on the body-centered cubic lattice. The average grain size determined by the scanning electron microscopy (SEM) for the first two alloys is 7-10 nm, and for the latter ones it is about 120 nm. The saturation magnetization of the films has linear dependence on the iron content, but coercivity has non-monotonic dependence on x, i.e., the films with x = 0.68 show highest coercivity. The magnetic anisotropy of the samples is studied by ferromagnetic resonance (FMR) spectroscopy.

[Myofibrillar creatine kinase: reversible binding to contractile proteins, stoichiometric ratio to myosin and its functional role]. / Miofibrilliarnaia kreatinkinaza: obratimoe sviazyvanie s sokratitel'nymi belkami, stekhiometricheskoe otnoshenie s miozinom i funktsional'noe znachenie.

Rat heart myofibrils were isolated and purified in three different media: sucrose medium; EGTA medium; EGTA+ATP medium. All preparations were characterized by similar Ca2+-sensitive ATPase activities and were practically free of mitochondrial and sarcolemmal contaminations. However, they contained different amounts of creatine kinase. In preparations which showed the most intact ultrastructure, the activity of creatine kinase was 0.99 +/- 0.12 IU/mg. It was found that creatine kinase can be bound to myofibrils in a reversible manner with Kd = 0.16 mg/ml = 1.8 X 10(-6) M; the creatine kinase/myosin ratio was estimated to be approximately 1:10. The localization of creatine kinase was found to be a basis for the high turnover rate of ATP in the coupled creatine kinase and ATPase reactions occurring in cardiac myofibrils.

[Synthesis and secretion of immunoglobulins in the small intestine of the rat immunized with horseradish peroxidase]. / Sintez i sekretsiia immunoglobulinov v tonkoi kishke krys, immunizirovannykh peroksidazoi khrena.

Fifty mature female rats of August strain are immunized with three intraperitoneal injections of horseradish peroxidase (HP) on the 1st, 14th and 28th days of the experiment. On the 42nd day of the experiment a resolution dose of HP is injected through the gastric catheter. The distal Peyer's patch with the adjoining area of the intestine and the proximal part of the jejunum are taken every two days after injecting the resolution dose of the antigen. After fixation in 8% solution of paraformaldehyde and washing, the sections 15 mcm thick are incubated in antigen solution. The complex antigen-antibody is determined by visualization of HP activity using R. C. Graham and M. J. Karnovsky method (1966). The first plasma cells with a positive intracellular reaction in the lamina propria of the small intestine appear on the 4th day after the oral immunization. Immunoglobulins in antibody-synthesizing cells fill the canals of the granular endoplasmic reticulum, as well as the Golgi complex cisterns and the perinuclear space. The anti-HP antibodies are revealed in the interepithelial spaces of the small intestine tunica mucosa and in numerous micropinocytic vesicles of enterocytes. A suggestion is made on a possible diffuse transmission of antibodies via microvilli of enterocytes.

[Secretory immunoglobulins (IgA) in the development of the immunologic reaction to horseradish peroxidase]. / Sekretornye immunoglobuliny (IgA) pri razvitii immunologicheskoi reaktsii k peroksidaze khrena.

The aim of the investigation was to visualize transport of antibodies produced in the small intestine of the preliminarily sensibilized rats. Horseradish peroxidase (HP) was used as an antigen. Visualization of antibodies was performed by means of determining HP activity (R.S. Graham and M.G. Karnovsky method, 1966). In the lamina propria of the tunica mucosa of the sensibilized rat small intestine, plasmocytes synthesizing antibodies appeared on the 4th day after a challenge dose of the antigen had been injected. The synthesized immunoglobulins were transported in two directions: via epithelium in the intestinal lumen and into the vessels of the lamina propria of the small intestine tunica mucosa. These both processes occur by means of micropinocytosis. Out of the intestinal vessels the antibodies get into the system of the hepatic portal vein and are detected in the sinusoid capillaries and further they get into the perisinusoid space (Disse). Besides, the reaction product is revealed in micropinocytic vesicles situating in cytoplasm of hepatocytes and in bile capillaries. Thus, antibodies synthesized in the lamina propria of the small intestine tunica mucosa get into the intestinal lumen not only through epithelium, but also through biliary system of the liver.

[Pharmacological correction of myocardial ischemia and arrhythmias in reversible coronary blood flow disorders and experimental myocardial infarct in dogs]. / Farmakologicheskaia korrektsiia ishemii miokarda i aritmii pri obratimykh narusheniiakh koronarnogo krovotoka i éksperimental'nom infarkte miokarda u sobak.

The efficacy of the sum of alkaloids of the common fumitory in temporary disorders of the coronary blood flow in the circumflex artery was studied in chronic experiments on 8 dogs. Occlusion of the vessel was caused by means of a remote-controlled loop implanted into the thoracic wall. The arrest of circulation in the artery was attended by the appearance of pathological signs on the ECG in the form of tachycardia, growth of the T wave amplitude, and displacement of the RS-T interval. Preliminary injection of the drug in a dose of 1--2 mg/kg prevented completely or reduced to a great measure the ischemic shifts. In experiments on 6 dogs, 5.2 mg/kg dose of the drug relieved for 20 to 87 min the disorders of rhythm induced by ligation of the interventricular branch of the left coronary artery.

[Certain pathogenetic mechanisms of development of atherosclerosis in dogs, induced without the use of cholesterol]. / O nekotorykh patogeneticheskikh mekhanizmakh razvitiia ateroskleroza u sabak pri ego vosproizvedenii bez primeneniia kholesterina

Chronic investigations (up to 3 years) conducted in dogs have evidenced that periodic disturbances of vascular permeability produced by using dicoumarin with a long-term blocking of the thyroid function greatly aggravate pathological manifestations induced by the action of 6-methylthiouracil. They result in the development in the animals of endogenous hypercholesterinemia, elevated content in the blood of beta-lipoproteins and in a periodic rise of the arterial pressure. These changes were particularly spectacular at the final stage of the experiment in animals with marked manifestations of atherosclerosis and were accompanied by reduced stand-by potentialities of the adrenal gland, disruption of metabolic processes in the myocardium along with the slowed down resorption of NaI131 from the heart muscle. The sensitivity of the heart to adrenalin was down too.