Membrane potential stabilizes the O intermediate in liposomes containing bacteriorhodopsin

AbstractIn the bacteriorhodopsin-containing proteoliposomes, a laser flash is found to induce formation of a bathointermediate decaying in several seconds, the difference spectrum being similar to the purple–blue transition. Different pH buffers do not affect the intermediate, whereas an uncoupler, gramicidin A, and lipophilic ions accelerate decay of the intermediate or inhibit its formation. In the liposomes containing E204Q bacteriorhodopsin mutant, formation of the intermediate is suppressed. In the wild-type bacteriorhodopsin liposomes, the bathointermediate formation is pH-independent within the pH 5–7 range. The efficiency of the long-lived O intermediate formation increases at a low pH. In the wild-type as well as in the E204Q mutant purple membrane, the O intermediate decay is slowed down at slightly higher pH values than that of the purple–blue transition. It is suggested that the membrane potential affects the equilibrium between the bacteriorhodopsin ground state (Glu-204 is protonated and Asp-85 is deprotonated) and the O intermediate (Asp-85 is protonated and Glu-204 is deprotonated), stabilizing the latter by changing the relative affinity of Asp-85 and Glu-204 to H+. At a low pH, protonation of a proton-releasing group (possibly Glu-194) in the bacteriorhodopsin ground state seems to prevent deprotonation of the Glu-204 during the photocycle. Thus, all protonatable residues of the outward proton pathway should be protonated in the O intermediate. Under such conditions, membrane potential stabilization of the O intermediate in the liposomes can be attributed to the direct effect of the potential on the pK value of Asp-85

Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

This article was made available through open access by the Brunel Open Access Publishing Fund.New palynological and ostracod data are presented from the Holocene Volga delta, obtained from short cores and surface samples collected in the Damchik region, near Astrakhan, Russian Federation in the northern Caspian Sea. Four phases of delta deposition are recognized and constrained by accelerated mass spectrometry (AMS) radiocarbon ages. Palynological records show that erosive channels, dunes (Baer hills) and inter-dune lakes were present during the period 11,500–8900 cal. BP at the time of the Mangyshlak Caspian lowstand. The period 8900–3770 cal. BP was characterized regionally by extensive steppe vegetation, with forest present at times with warmer, more humid climates, and with halophytic and xerophytic vegetation present at times of drought. The period 3770–2080 cal. BP was a time of active delta deposition, with forest or woodland close to the delta, indicating relatively warm and humid climates and variable Caspian Sea levels. From 2080 cal. BP to the present-day, aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals. Soils and incised valley sediments are associated with the regional Derbent regression and may be time-equivalent with the ‘Medieval Warm Period’. Fungal spores are an indicator of erosional or aeolian processes, whereas fungal hyphae are associated with soil formation. Freshwater algae, ostracods and dinocysts indicate mainly freshwater conditions during the Holocene with minor brackish influences. Dinocysts present include Spiniferites cruciformis, Caspidinium rugosum, Impagidinium caspienense and Pterocysta cruciformis, the latter a new record for the Caspian Sea. The Holocene Volga delta is a partial analogue for the much larger oil and gas bearing Mio-Pliocene palaeo-Volga delta.Funding for the data collection and field work was provided from the following sources: 1 – IGCP-UNESCO 2003–2008 (Project 481 CASPAGE, Dating Caspian Sea Level Change); 2 – NWO, Netherlands Science Foundation and RFFI, Russian Science Foundation 2005–2008 (Programme: ‘VHR Seismic Stratigraphy and Paleoecology of the Holocene Volga Delta’); and 3 – BP Exploration (Caspian Sea) Sea Ltd. (Azeri-Chirag-Gunashli) 2005–2008 (‘Unravelling the Small-Scale Stratigraphy and Sediment Dynamics of the Modern Volga Delta Using VHR Marine Geophysics’). The palynological work was funded jointly by BP Exploration (Caspian Sea) Ltd., Delft University of Technology and KrA Stratigraphic Ltd. Ostracod analyses were funded by StrataData Ltd. and funding for two additional radiocarbon dates provided by Deltares

ПРОЧНОСТЬ КОНТАКТНОГО СТЫКА СБОРНЫХ КОЛОНН С ДЕФОРМИРУЕМОЙ ЦЕНТРИРУЮЩЕЙ ПРОКЛАДКОЙ

Due to growth of number of storeys in a dwelling and public buildings for mass gatherings (up to 20-25 storeys) requirements of their construction industrialization necessitate designs of precast column joints which are capable to bear high loads (up to 10-12 МН and more). The paper presents an analysis of the known contact joint designs used in the columns of frame buildings and the analysis shows that the these design are rather efficient. However these joints are sensitive to accuracy of column butt end fabrication. Bearing capacity of joints can be significantly decreased in case of comparatively small ends out of square. It has been decided to introduce a deformable centering laying made of soft steel in a joint design in order to exclude the mentioned disadvantage. Due to its plastic deformation the laying ensures transformation of longitudinal effort occurring in it to the column axis. As a result of it we obtain the most advantageous position for joint design required for transfer of compressing force at column longitudinal axis.Experimental investigations of contact joints with a deformable centering laying have been carried with due account of the requirements to construction standards, results of the executed works and main results of the investigations are presented in the paper. Proposals for calculation and designing of these joints have been given on the basis of the obtained data and works. It has been shown that application of the centering laying with corresponding concrete confinement reinforcement at the joint make it possible to ensure the required bearing capacity and reliability.В связи с ростом этажности жилых и общественных зданий массового назначения (до 20-25 этажей) потребность индустриализации их строительства вызывает необходимость в конструкциях стыков сборных колонн, способных воспринимать повышенные нагрузки (до 10-12 МН и более). Выполненный в статье анализ известных конструкций контактных стыков колонн каркасных зданий показывает, что, в принципе, они являются достаточно эффективными. Однако эти стыки чувствительны к точности изготовления торцов колонн. При сравнительно небольших перекосах торцов несущая способность стыков может существенно уменьшиться. Чтобы исключить этот недостаток, было решено ввести в конструкцию стыка деформируемую центрирующую прокладку из мягкой стали. За счет пластического деформирования она обеспечивает перемещение к оси колонны действующего в ней продольного усилия. В результате обеспечивается наиболее выгодное для конструкции стыка положение места передачи сжимающего усилия у продольной оси колонны.Учитывая требования строительных норм и результаты многих работ, были выполнены экспериментальные исследования контактных стыков с деформируемой центрирующей прокладкой, основные результаты которых представлены в статье. На основании полученных данных сформулированы предложения по расчету и конструированию этих стыков. Показано, что применение центрирующей прокладки при соответствующем косвенном армировании бетона у стыка позволяет обеспечить требуемые несущую способность и надежность

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in oneelectron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (t,1.5 ms) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (t,16 ms). It returns from the b-hemes to heme d with t,180 ms. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (t,16 ms) yielding a transient hexacoordinate state (CO-Fe2+ -L). Then the ligand slowly (t,30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (t,20 ms), some heme b558 (t,0.2–3 ms), and finally migrates from heme d to heme b595 (t,24 ms) in ,5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions

О ВЛИЯНИИ РАБОЧЕЙ АРМАТУРЫ ЖЕЛЕЗОБЕТОННЫХ ПЛИТ НА ИХ СОПРОТИВЛЕНИЕ ПРОДАВЛИВАНИЮ

The paper presents experimental research results and their analysis in respect of flat reinforced concrete slabs resting on point supports or soil in case of concentrated punching force. However the conducted researches have shown a number of incompatibilities accepted in computational model standards that appear in the form of critical parameters in the punching zone and configuration of computational (critical) sections in comparison with an actual pattern of slab crack formation and their collapse in the places of concentrated force application. Moreover, the computational methods do not take into account at all an influence of longitudinal reinforcement on both principal axis of the building frame or take it into account this phenomenon by empirical dependence indirectly. In view of the above-mentioned facts an accumulation of new experimental data is considered as an expedient process with the purpose to identify a physical pattern of flat reinforced concrete slabs operation under concentrated punching force. The paper makes it possible to revise a calculative methodology and, preserving a high reliability, it also permits to improve efficiency of a floor construction of the whole framework. It has been determined that longitudinal reinforcement of reinforced concrete slabs is actively involved in their work under concentrated punching force and exerts a prominent influence on their resistance to punching force. The paper presents a possible approach pertaining to evaluation of a longitudinal reinforcement influence on resistance of reinforced concrete slabs to punching force with due account of regulations of the appropriate standardized documents. Представлены результаты экспериментальных исследований плоских железобетонных плит, опертых на точечные опоры или на грунт, при действии сосредоточенного продавливающего усилия и выполнен анализ результатов испытаний. Однако проведенные исследования показали ряд несоответствий, принятых в нормах расчетных моделей, выражающихся формой критических параметров зоны продавливания и конфигурацией расчетных (критических) сечений фактическим картинам трещинообразования в плитах и разрушения их в местах приложения сосредоточенных усилий. Кроме того, расчетными методами либо вовсе не учитывается влияние продольной по обеим главным осям каркаса здания рабочей арматуры плит, либо учитывается опосредованно эмпирическими зависимостями. С учетом сказанного накопление новых экспериментальных данных с целью выявления физической картины работы плоских железобетонных плит под действием сосредоточенного продавливающего усилия является целесообразным. Это позволит уточнить расчетную методику, а также, сохранив высокую надежность, повысить эффективность конструкции перекрытий всего каркаса. Установлено, что продольная рабочая арматура железобетонных плит активно включается в их работу при продавливании сосредоточенным усилием и оказывает заметное влияние на их сопротивление этому воздействию. Представлен возможный подход к оценке влияния продольной арматуры на сопротивление железобетонных плит продавливающему усилию с учетом положений нормативных документов

ПАРАНЕОПЛАСТИЧЕСКОЕ ПОРАЖЕНИЕ ЦЕНТРАЛЬНОЙ И ПЕРИФЕРИЧЕСКОЙ НЕРВНОЙ СИСТЕМЫ ПРИ РАКЕ МОЛОЧНОЙ ЖЕЛЕЗЫ. КЛИНИЧЕСКИЙ СЛУЧАЙ

Paraneoplastic neurological syndrome involves the concurrent development of cancer and neurologicaldiseases. Breast cancer is the second most common cancer associated with paraneoplastic damage to the central and peripheral nervous system. Autoimmune genesis of the disease is characterized by the presence of highly specific onconeural antibodies, which selectively affect neurons in the brain cord, spinal cord and spinal ganglia, and cause the onset of neurological symptoms within 2 years before cancer is detected. Six well-characterized onconeural antibodies detected in the blood serum of breast cancer patients can be used for the laboratory diagnosis of paraneoplastic neurological syndrome. Of them, anti-Hu, anti-CV2 and anti-amphiphysin antibodies cause polyneuropathy most often. Anti-Yo antibody is usually associated with cerebellar degeneration. Multiple neuronal autoantibodies can be simultaneously detected in a patient. Removal of the tumor may lead to stabilization and even partial regression of the neurological symptoms in 70 % of patients. Therefore, the surgical treatment of cancer should consider not only the tumor extension, but also the severity and progression of neurological deficit. We present a case of paraneoplastic cerebellar degeneration and paraneoplastic polyneuropathy in a 50-year-old woman with the neurological symptoms appeared 5 months before breast infiltrating ductal carcinoma was detected. The current approaches to the diagnosis of paraneoplastic neurological syndrome, as well as feasibility of radical removal of the tumor due to progression of neurological deficit were discussed.Паранеопластический неврологический синдром предполагает параллельное развитие рака и неврологической болезни. Рак молочной железы является второй по частоте встречаемости злокачественной опухолью после рака легкого, ассоциированной с паранеопластическим поражением центральной и периферической нервной системы. Аутоиммунный генез заболевания предполагает наличие в крови высокоспецифичных онконевральных антител, избирательно поражающих нейроны головного, спинного мозга, спинальных ганглиев и вызывающих дебют неврологических симптомов в среднем за 2 года до диагностики рака. Шесть хорошо охарактеризованных и используемых в настоящее время в лабораторной диагностике паранеопластического неврологического синдрома онконевральных антител детектируются в сыворотке крови пациентов, страдающих раком молочной железы. Из них полиневропатию чаще вызывают anti-Hu, anti-CV2 и anti-amphiphysin антитела, а при мозжечковой дегенерации встречаются еще и anti-Yo антитела. У одного пациента могут быть обнаружены одновременно несколько типов нейрональных аутоантител. С точки зрения выявления рака на более ранних стадиях очевидна целесообразность проведения направленного онкологического поиска у пациентов с неврологическими симптомами и обнаруженными в крови онконевральными антителами. После удаления злокачественной опухоли, являющейся прямым источником нейрональных антигенов, в 70 % случаев имеет место стабилизация неврологических симптомов и даже частичный их регресс. Поэтому вопрос, касающийся хирургического лечения рака, необходимо рассматривать не только с точки зрения распространенности опухолевого процесса, но и с учетом тяжести и темпов прогрессирования неврологического дефицита. В статье описан клинический случай паранеопластической мозжечковой дегенерации и паранеопластической полиневропатии у женщины 50 лет с возникновением неврологических симптомов за 5 мес до обнаружения инфильтрирующей протоковой карциномы молочной железы. Обсуждены современные подходы к диагностике паранеопластического неврологического синдрома, а также вопросы течения неврологического заболевания на фоне химиотерапии рака и целесообразности радикального удаления опухоли в связи с нарастанием неврологического дефицита

Cryo-EM structures of complex I from mouse heart mitochondria in two biochemically defined states.

Complex I (NADH:ubiquinone oxidoreductase) uses the reducing potential of NADH to drive protons across the energy-transducing inner membrane and power oxidative phosphorylation in mammalian mitochondria. Recent cryo-EM analyses have produced near-complete models of all 45 subunits in the bovine, ovine and porcine complexes and have identified two states relevant to complex I in ischemia-reperfusion injury. Here, we describe the 3.3-Å structure of complex I from mouse heart mitochondria, a biomedically relevant model system, in the 'active' state. We reveal a nucleotide bound in subunit NDUFA10, a nucleoside kinase homolog, and define mechanistically critical elements in the mammalian enzyme. By comparisons with a 3.9-Å structure of the 'deactive' state and with known bacterial structures, we identify differences in helical geometry in the membrane domain that occur upon activation or that alter the positions of catalytically important charged residues. Our results demonstrate the capability of cryo-EM analyses to challenge and develop mechanistic models for mammalian complex I