Lys98 Substitution in Human AP Endonuclease 1 Affects the Kinetic Mechanism of Enzyme Action in Base Excision and Nucleotide Incision Repair Pathways

Human apurinic/apyrimidinic endonuclease 1 (APE1) is a key enzyme in the base excision repair (BER) and nucleotide incision repair (NIR) pathways. We recently analyzed the conformational dynamics and kinetic mechanism of wild-type (wt) protein, in a stopped-flow fluorescence study. In this study, we investigated the mutant enzyme APE1K98A using the same approach. Lys98 was known to hydrogen bond to the carboxyl group of Asp70, a residue implicated in binding the divalent metal ion. Our data suggested that the conformational selection and induced fit occur during the enzyme action. We expanded upon the evidence that APE1 can pre-exist in two conformations. The isomerization of an enzyme-product complex in the BER process and the additional isomerization stage of enzyme-substrate complex in the NIR process were established for APE1K98A. These stages had not been registered for the wtAPE1. We found that the K98A substitution resulted in a 12-fold reduction of catalytic constant of 5′-phosphodiester bond hydrolysis in (3-hydroxytetrahydrofuran-2-yl)methyl phosphate (F, tetrahydrofuran) containing substrate, and in 200-fold reduction in 5,6-dihydrouridine (DHU) containing substrate. Thus, the K98A substitution influenced NIR more than BER. We demonstrated that the K98A mutation influenced the formation of primary unspecific enzyme-substrate complex in a complicated manner, depending on the Mg2+ concentration and pH. This mutation obstructed the induced fit of enzyme in the complex with undamaged DNA and F-containing DNA and appreciably decreased the stability of primary complex upon interaction of enzyme with DNA, containing the natural apurinic/apyrimidinic (AP) site. Furthermore, it significantly delayed the activation of the less active form of enzyme during NIR and slowed down the conformational conversion of the complex of enzyme with the cleavage product of DHU-substrate. Our data revealed that APE1 uses the same active site to catalyze the cleavage of DHU- and AP-substrates

High-speed impact of the metal projectile on the barrier containing porous corundum-based ceramics with chemically active filler

The paper presents a calculation-experimental study on high-speed interaction of the metal projectile with a combined barrier made of porous corundum-based ceramics filled with chemically active composition (sulfur, nitrate of potash) in the wide range of speeds. A mathematical behavior model of porous corundum-based ceramics with chemically active filler is developed within the scope of mechanics of continuous media taking into account the energy embedding from a possible chemical reaction between a projectile metal and filler at high-speed impact. Essential embedding of inlet heat is not observed in the considered range of impact speeds (2.5 … 8 km/s)

METHOD OF MANUFACTURING INFRARED LIGHT FILTER

FIELD: light engineering. SUBSTANCE: method comprises using activated LiF:U crystals as a material for the infrared filter and irradiating the crystals by neutrons. The irradiated crystals are exposed to air at a room temperature for 10-12 months and then are roasted in air at a temperature of 200-300°C for 0.5-1.5 hours. EFFECT: enhanced thermal and radiation stability. 1 dwg.Изобретение относится к области светотехники и интегральной оптики, связанной с созданием инфракрасных светофильтров отрезающего и полосового типа, поглощающих видимое излучение и пропускающих коротковолновое и длинноволновое ближнее инфракрасное излучение и предназначенных для защиты инфракрасных датчиков видеоконтрольных устройств и приборов ночного видения от паразитных помех, связанных с воздействием света видимого диапазона, а также для использования в оптических системах контроля подлинности документов, в системах охранной и пожарной сигнализации, в том числе в системах контроля и разграничения доступа и охраны периметра объектов, в видеодомофонах, видеоглазках и подобных устройствах. Суть изобретения заключается в том, что в качестве материала для ИК-светофильтра используют предварительно активированные кристаллы LiF:U и облучают их нейтронами до флюенса 1,2·10¹⁶?3·10¹⁶ см⁻². Облученные кристаллы выдерживают на воздухе при комнатной температуре в течение 10-12 месяцев, а затем подвергают их отжигу на воздухе при температуре 200-300°С в течение 0,5-1,5 часов. Технический результат: обеспечение сплошного поглощения света в видимом диапазоне и повышение термической и радиационной устойчивости. 1 ил

Annama H chondrite-Mineralogy, physical properties, cosmic ray exposure, and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7-8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 +/- 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30-40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The Be-10 concentration indicates a recent (3-5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30-35 cm pre-entry radius.Peer reviewe

WORKING SUBSTANCE FOR THERMO-EXOELECTRONIC DOSIMETRY

FIELD: physics; measurements. SUBSTANCE: invention pertains to thermo-electronic dosimetry of electron beams, and can be used for controlling a radiation environment in places for testing and operating pulsed electron beams and in electron beam technology. In the working substance for thermo-exoelectronic dosimetry of an electron radiation, the oxide base used is an orthosilicate of gadolinium with additives of ceric oxide, with the following ratios of components, mol.%: Gd₂SiO₅ 97.0-99.9; Ce₂O₃ 0.1-3.0. The technical outcome is the lowering of the temperature of the base working TEE peak to 48°C with fluence of electrons of 10¹⁰-10¹³ cm⁻² and to 75-79°C with fluence of electrons of 10¹³-10¹⁵ cm⁻², and increased speed of recording dosimetry information when reading from the working substance for thermo-exoelectronic dosimetry and increased speed of bringing the working substance into a state where it is ready for use. EFFECT: increased speed of recording dosimetry information. 2 dwg.Изобретение относится к области термоэкзоэлектронной дозиметрии электронных пучков; может быть использовано для контроля радиационной обстановки в местах испытания и функционирования импульсных электронных пушек и электронно-лучевой техники. Сущность: рабочее вещество для термоэкзоэлектронной дозиметрии электронного излучения, в котором в качестве оксидной основы использован ортосиликат гадолиния с добавкой оксида церия, при следующем соотношении компонентов, мол.%: Gd₂SiO₅ 97,0-99,9; Се₂О₃ 0,1-3,0. Технический результат: понижение температуры основного рабочего пика ТЭЭ до 48°С при флюенсах электронов 10¹⁰-1013 см² и до 75-79°С при флюенсах электронов 1013-10¹⁵ см⁻², повышение скорости снятия дозиметрической информации при ее считывании с рабочего вещества для термоэкзоэлектронной дозиметрии и повышение скорости приведения рабочего вещества в состояние рабочей готовности. 2 ил., 1 табл

COMPLEX SILVER VANADATE AS LUMINOFOR IN RED AND NEAR-INFRARED REGION OF LUMINESCENCE AND METHOD OF ITS OBTAINING

FIELD: chemistry. SUBSTANCE: invention can be used in manufacturing of indicators and sensors of ionising and infrared radiation. Initial mixture of ingredients is prepared, wt %: AgNO₃ - 39.91?42.28; MCO₃ - 12.46?17.3; where M - Ca or Sr; V₂O₅ - 42.74?45.26; thoroughly mixing said components in presence of alcohol. Then it is heated to 300-350°C and expose at said temperature for 2-3 hours. After that it is heated again to 480-500°C and expose at said temperature for 95-105 hours. Powder is briquetted and thermally processed at 490-500°C during 38-42 hours. Complex silver vanadate which is obtained has composition Ag₂M(VO₃)4, where M - Ca or Sr, and luminesces in red and near-infrared region up to 840-850 nm. EFFECT: obtaining silver vanadate. 2 cl, 2 dwg, 2 ex.Изобретение может быть использовано при изготовлении индикаторов и сенсоров ионизирующего и инфракрасного излучения. Готовят исходную смесь ингредиентов, мас.%: AgNO₃ - 39,91?42,28; MCO₃ - 12,46?17,3; где М - Са или Sr; V₂O₅ - 42,74?45,26; тщательным перемешиванием указанных компонентов в присутствии спирта. Затем ее нагревают до 300-350°С с выдержкой при этой температуре 2-3 ч. После этого снова нагревают до 480-500°С с выдержкой при этой температуре 95-105 ч. Порошок брикетируют и термообрабатывают при 490-500°С в течение 38-42 ч. Полученный сложный ванадат серебра имеет состав Ag₂M(VO₃)₄, где М - Са или Sr, и люминесцирует в красной и ближней инфракрасной области вплоть до 840-850 нм. 2 н.п. ф-лы, 2 ил

METHOD FOR PRODUCING NEUTRINO-RECORDING SCINTILLATION COMPOUND

FIELD: nuclear physics; recording neutrino and anti-neutrino. SUBSTANCE: proposed method for producing scintillation compound for recording neutrino and anti-neutrino includes preparation of ytterbium activated and sodium fluoride based compound by mixing up ingredients in following proportion, mole percent: NaF, 99.97-99.6; YbF₃, 0.01-0.3; UO₂(NO₃)₂, 0.01-0.05; oxygen, 0.01-0.05. EFFECT: enhanced scintillation efficiency of proposed compound. 1 cl, 2 dwg, 1 tbl.Предложенное изобретение относится к области ядерной физики, а именно к области технологии регистрации нейтрино и антинейтрино. Задачей данного изобретения является повышение сцинтилляционной эффективности сцинтиллирующего состава для регистрации нейтрино. В предложенном изобретении реализован способ получения сцинтиллирующего состава для регистрации нейтрино на основе фторида натрия, активированного иттербием, который заключается в смешивании компонентов при следующем соотношении (мол.%): NaF 99,97-99,6; YbF₃ 0,01-0,3; UO₂(NO₃)₂ 0,01-0,05; кислород 0,01-0,05. 2 ил., 1 табл

Promoting effect of 4-dimethylaminopyridine on selective oxidation of benzyl alcohol over MoVTeNb mixed oxides

A liquid phase oxidation of benzyl alcohol with 1 atm molecular oxygen catalyzed by MoVTeNb mixed oxides has been investigated. It is demonstrated that 4-dimethylaminopyridine (DMAP) acting as a co-catalyst, notably accelerates the reaction, as well as influences the ratio of the reaction products (benzaldehyde, benzyl benzoate and benzoic acid). The findings can be interpreted in terms of the involvement of DMAP (a good enough N-nucleophile) in the process of chemo-desorption of oxygenates formed on the catalyst surface