pH-induced structural changes of surface immobilized poly(L-lysine) by two-dimensional (2D) infrared correlation study

This paper reports the pH-induced structural changes in the surface immobilized poly(L-lysine)(PLL)film.Two-dimensional(2D) correlation analysis was applied to the Fourier transform infrared(FTIR)spectra of the surface-immobilized PLL film to examine the spectral changes induced by the alternations of the protonation state of the amino group in the side chain.Significant spectral changes in the FTIR spectra of the PLL film were observed between pH 7 and 8.The decrease in the protonation state of the amino group in the side chain induced spectral changes in the amino group as well as conformational changes in the alky]group in the side chain.From pH 1-8,the spectral changes in the amino and alkyl groups in the side chain occurred before those of the amide group in the main chain of the surface immobilized PLL film.     

Carbon isotope geochemistry in the Yalujiang estuary

The distribution of particulate organic carbon (POC) along the lower reaches is similar between the dry season and the flood season in the Yalujiang Estuary, North China. However, the values of particulate organic carbon of the upperstream in the dry season are one magnitude lower than the concentrations in the flood season. Stable carbon isotope ratios have been used to study the sources of particulate organic carbon in the Yalujiang Estuary. The isotopic composition of POC shows a range from -23.1‰ to -29.4‰ with a little seasonal variation. The isotopic evidence indicates that the POC in the Yalujiang Estuary is predominantly of terrestrial origin rather than a result of in situ plankton. The study of the ratio of POC: Chla shows that the turbidity maximum plays an important role in POC cycle in the Yalujiang Estuary. Organic detritus and soil erosion are the main contributions to POC in the turbidity maximum, especially in the flood season.     

BINOCULAR RESPONSES IN THE SUPERIOR COLLICULUS OF THE ALBINO RAT

The retinotopic map for the contralateral eye is similar to that found in the pigmentedrats and in other rodents. Cells which had ipsilateral responses were recorded in a fairlylarge area in tale rostral portion of the tectum. Their receptive fields lay from about 40°in the contralateral hemifield to about 40°in the ipsilateral hemifield. The ipsilateral re-sponse of a binocular cell is similar in almost every respect to its counterpart in the oppositeeye except being very weak and that the receptive field is usually smaller. Most binocularcells are distributed in the Stratmn grisemn superfieiale (SGS) and the Stratum optieum (SO).Less binocular cells recorded in the Stratum griseum intermediale (SGI) have moro scatter-ed distribution both in the size and in the position of the receptive field.     

五羰基合铁分子化学键特性的研究

We have found from experimental data that, in the iron pentacarbonyl molecule, the length of Fe-C bond in axial is shorter than that in planar, but the bond is weaker; the bond distances of C-O of both planar and axial are equal, while the bond strengths are different. This is against the traditional view of “the shorter the bond is, the stronger the bond will be”. We have got through calculation and research, that the main cause of such difference is that the effects of the backdonor of Fe atom′s electrons to C-O bonds in axial and planar are different. The shorter the Fe-C bond is, the more effective the backdonor (or transfer) of electrons is. So that the population between Fe and C in axial are less than those in planar, so the bond is weaker, and the C-O bonds have gained more backdonor electrons than those in planar, thus the bond is stronger.     

Mpro-C蛋白三维结构域交换的机理:来自分子模拟的线索

SARS coronavirus main protease (Mpro) is a key enzyme involved in the extensive proteolytic processing of the virus? polyproteins. The crystal structure of Mpro reveals that the enzyme exists in two different homo-dimeric forms: a three-dimensional (3D) domain-swapped form; and a non-3D domain-swapped form. The isolated C-terminal domain (Mpro-C) also forms a 3D domain-swapped structure similar to the ful-length protein. Unlike conventional 3D domain-swapped structures, in which the swapped regions are located on the surface, Mpro-C swaps a helix at the core of a folded domain. In this work, we used molecular dynamics simulations and 3D domain-swapping predictions to investigate how a highly buried core helix in the helix bundle structure of Mpro-C can be swapped. We found that both structure-and sequence-based methods failed to predict the location of the hinge loop in Mpro-C and Mpro. Extensive molecular dynamics simulations were performed to investigate the structural properties of the unfolded monomer and the 3D domain-swapped dimer of Mpro-C. We found that, although the swapped region was buried in the native state, it was exposed in the unfolded monomer. Our results suggest that the opening of the swapped region in the ful y or partial y unfolded state may promote interactions between monomers and the formation of domain-swapped dimers.     

The Numerical Simulation of the Climatic Change Caused by CO_2 Doubling

The IAP two-level atmospheric general circulation model was coupled to a 60-m-deep mixed layer ocean model and a zero-layer thermodynamic model to simulate the climatic effects induced by a doubling of CO_2 concentration in the atmosphere.The global surface temperature is 1.75℃ when CO_2 is doubled. This value is lower than most of other results in the world, such as those of GFDL, NCAR, UKMO, GISS and OSU models.There are large regional and seasonal differences in the climatic change. Great warming is found in the Northern Hemisphere's high-latitude region anti the Antarctica; and the warming in land areas is greater than in ocean areas, while the precipitation increases in high latitudes and tropical regions but decreases in subtropical regions. In both hemispheres, the warming is greater in winter than in other seasons. As for the changes in China, we find that the precipitation in southwestern and northern China greatly decreases in summer but increases in winter.     

ANNUAL VARIATIONS OF E-P CROSS SECTION AND TROPOSPHERIC WESTERLY ACCELERATION

This is one part of the series study on the forcing of waves on basic flow, in which theannual variations of E- P cross section are used to compare the wave- mean flow interactionsin the Northern and Southern Hemispheres. Results show that in either hemisphere, wave-meanflow interaction is very strong in winter, and very weak in summer. External forcing sourcefor planetary waves in the Southern Hemisphere appears to be rather weak not only in summer,but also in winter. It is pointed out that in the troposphere. since the mass circulation isstrong, and since the static stability is small, in the dynamic equation, the inertial effect ofthe residual circulation becomes important in balancing that of the E- P flux divergence.Therefore, when the westerly acceleration in the troposphere is studied, both terms of E-Pflux and residual circulation should be considered. It turns out to be more convenient to usethe conventional Euler system to investigate the direct contribution of eddies to the meanflow.     

A COMPARATIVE STUDY ON THE STEM LEAF ANATOMY OF THE THREE WILD RICE SPECIES IN CHINA

The results of study on the anatomy of the stem leaf of Oryza sativa L. f. spontanea Roschev.,O. officinalis Wall. and O. meyeriana Baill. in China indicated that O. sativa L. f. spontanea had full lysigenous space in the internodes,large lysigenous space in the mid rib of the leaf,and the lysigenous path in the large vascular bundles of the leaf.Its mesophyll cells were arranged compactly and its cell walls were much inwardly folded.In the lysigenous space in the internodes of O. officinalis remained some membranes. O. meyeriana had neither large lysigenous space in the internodes and leaf mid rib nor the lysigenous path in the large vascular bundles of the leaf.The results mentioned above showed that the three wild rice species having different anatomical structures adapted to growing in the water-grown and high solar-radiation ecotype of the swamp-land, the wet and little-sunlight ecological conditions of the mountain valley and the xerophilous and shady ecological environment, respectively.The autho     

Characteristics and source of black carbon aerosol over Taklimakan Desert

Black carbon(BC) and PM10 in the center of the Taklimakan Desert were online monitored in the whole year of 2007.In addi-tion,TSP samples were also synchronously daily collected by medium-volume samplers with Whatman41 filters in the spring of 2007.BC in the dust aerosol was up to 1.14%of the total mass of PM10.A remarkable seasonal variation of BC in the aerosol was observed in the order of winter>spring>autumn>summer.The peak value of BC appeared at midnight while the lowest one in the evening each day,w...     

Specific features of the detection of hydrogen chloride in air with semiconductor sensors

The donor and acceptor character of the change in the resistance of semiconductor sensors in the presence of hydrogen chloride in air was elucidated. Conditions controlling the character of the sensor signal were revealed. The donor signal of the sensor increases with increasing temperature of the sensor, increasing air humidity, and decreasing concentration of hydrogen chloride. On the contrary, a decrease in the temperature of the sensor, a decrease in humidity, and an increase in the concentration of hydrogen chloride enhance the acceptor signal of the sensor. Air humidity has the decisive effect on the character of the sensor signal. It was demonstrated that semiconductor sensors allow the determination of hydrogen chloride in air at a level of the maximum permissible concentration (MPC) in the sanitary zone (0.2 mg/m³). Original Russian Text ￠ L.A. Obvintseva, E.A. Oksengoit-Gruzman, V.L. Kuchaev, A.K. Avetisov, F.Kh. Chibirova, M.P. Dmitrieva, 2008, published in Zhurnal Analiticheskoi Khimii, 2008, Vol. 63, No. 3, pp. 308–313.     

Calibration methods for microdialysis sampling in vivo: muscle and adipose tissue

Calibration methods for microdialysis sampling were studied in the muscle and adipose tissue of rats. Both the delivery method and the no-net-flux method were used to determine the extraction efficiency (EE) of acetaminophen and caffeine in both tissues. There was no concentration dependence of the EE either in vitro or in vivo for either acetaminophen or caffeine. The EEs determined by the delivery and no-net-flux methods were not different. However, the EEs of both caffeine and acetaminophen determined in vitro were significantly higher than those determined in the muscle and adipose. This indicates that mass transfer in the tissue is the rate-determining factor for the EE in vivo. The relative difference between the EE in vitro and the EE in the muscle was smaller than the difference between the EE in vitro and the EE in the adipose. In addition, the EE in the muscle decreased more than the EE in the adipose after the animal was euthanized. This indicated that exchange between the extracellular fluid and plasma is the rate-determining step in mass transport relative to microdialysis sampling. This has a more significant effect on the EE in the muscle than the EE in the adipose. Both the delivery and no-net-flux methods can be used to calibrate microdialysis probes in the muscle and adipose.     

Alteration in photosystem II photochemistry of thylakoids isolated from senescing leaves of wheat seedlings

Wheat seedlings, grown for 7 days in the light, were allowed to senesce in the light or dark, and the change in the photosystem II (PS II) photochemistry of chloroplasts isolated from the primary leaves of these seedlings was investigated. The decrease in oxygen evolution and the fast fluorescence results indicated that the impairment of PS II in the leaves of seedlings senescing in the light was different from that in the leaves of seedlings senescing in the dark. Thermoluminescence studies showed a structural modification in the Q_B protein of chloroplasts isolated from leaves senescing in the light and an alteration in the S state transition of chloroplasts isolated from leaves senescing in the dark.     

ESR方法检测竹红菌素的半醌负离子自由基

从顺磁共振波谱检测到通过竹红菌素的光诱导还原和基态竹红菌素跟脂肪胺的电子转移两条途径所得到的自由基信号, 并由电化学还原得到同一自由基, 确认它为半醌负离子自由基。竹红菌素溶液中加入芳香胺观察不到ESR信号。它的3,10位上与醌基相邻近的羟基离解以后, 无论在基态还是在激发态都观察不到ESR信号。此外, 还从吸收光谱观察到半醌负离子自由基吸收以及竹红菌素跟脂肪胺之间的相互作用。     

Analytical strategies to determine antibiotic residues in fish

The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised.     

The Behavior of Trivalent and Pentavalent Methylarsenicals in Lake Biwa

Seasonal changes in the distribution of arsenic species were observed in a dredged area in the southern basin of Lake Biwa, Japan. The concentrations of dimethylarsenic acid [DMAA(V)] became comparable with those of inorganic forms during a stratification period. DMAA(V) increased not only in the photic zone but also in the hypolimnion. In the photic zone, an increase in DMAA(V) was observed with the yearly maximum of water temperature. In the hypolimnion, the seasonal changes in methylarsenicals differed from those in surface waters. DMAA(V) maxima appeared seasonally under sub-anoxic conditions and developed regionally at the redox boundary and above the sediment surface. The DMAA(V) concentrations increased in the initial period of oxygen depletion and just after the disappearance of anoxia, while they diminished in the anoxic hypolimnion by midsummer. The seasonal behavior of trivalent methylarsenicals, which are readily oxidized in oxic environments, was similar to that of DMAA(V). The total arsenic concentration in the surface layer rose to a maximum in late summer. Methylarsenicals did not increase in such a way that the total arsenic concentration increased during summer. © 1997 by John Wiley & Sons, Ltd.     

An Evidence-Based Review of Application Devices for Nitric Oxide Concentration Determination from Exhaled Air in the Diagnosis of Inflammation and Treatment Monitoring

The measurement of nitric oxide (NO) in exhaled air is used in diagnostics and monitoring the pathologies not only in the respiratory system but also in the oral cavity. It has shown a huge increase in its level in asthma and diseases of the oral cavity. It seems reasonable to undertake research on the impact of inflammation on the level of NO in exhaled air. The aim of the study is to make an evidence-based review of the application of NO levels in exhaled air in the diagnosis of inflammation and treatment monitoring on the basis of selected measuring devices. Methods and Results: This paper presents an example of the application of NO measurement in exhaled air in individual human systems. Selected measuring devices, their non-invasiveness, and their advantages are described. Discussion: The usefulness of this diagnostic method in pathologies of the oral cavity was noted. Conclusions: Measuring the level of NO in exhaled air seems to be a useful diagnostic method.     

Changes in wine volatile compounds of varietal wines during ageing in wood barrels

Twelve single-variety wines were aged in new American oak barrels. A control wine of each variety without ageing in wood was also studied. The volatile aroma composition of these wines was analysed after the following combinations of time in wood and time in bottle: 0 months in wood plus 18 months in bottle, 4 months in wood plus 14 months in bottle, 9 months in wood plus 12 months in barrel and 12 months in barrel plus 6 months in bottle.The data obtained were studied by two different multivariate methods: factor analysis by principal components and stepwise linear discriminant analysis. The results obtained showed that the capacity of wine to extract the volatile compounds from the wood depended on the variety of grape used. Furthermore, it was also found that the changes in the volatile composition of the wines induced by the wood ageing were more important during the first 4 months. In addition, the volatile compounds studied allowed to differentiate and correctly classify the wines according to the time they had been in contact with the wood.     

煤烘玉米和饮水为介质地氟病区骨畸形病人全血尿多元素含量的分析

采集了贵族个煤烘玉米为主要介质和河北２个饮水为介质氟病区内骨畸形病人的全血、尿、检测了其中８种元素含量,结果表明,贵州各氟病区少儿骨软化与成年骨硬化畸形病人的全血铝、钙、磷、铁和尿氟、铝均显著高于同龄对照组,尿磷均低于同龄对照组。少儿骨软化病人全血锌均下降,尿锌多下降。某水型氟病区骨软化经产妇尿氟、全血铜升高;骨软化少年全血铝显著升高,锌、铁下降,尿氟升高,尿锌,磷下降。海边的典型氟骨症病人全血、     

Radial structure and property relationship in the thermal stabilization of PAN precursor fibres

Here we report on the role of oxygen in the evolution of radial heterogeneity in the fibre structure and properties of PAN fibres stabilized in air and vacuum at different temperatures. Modulus mapping by Nano-indentation showed heterogeneous modulus distribution in the fibres treated in air, while no variation in modulus was observed in fibres processed in vacuum. Raman spectroscopy and elemental analysis revealed that the temperature dependent oxygen diffusion from skin to core of the fibres assisted in the evolution of higher extent of sp²-hybridized carbons in the skin compared to core of the air treated samples. Conversely, no radial structure variations were observed in the vacuum treated fibres. Higher modulus in the skin of air-treated fibres was due to the formation of compact structures which was associated with the enhanced intermolecular interactions facilitated by the formation of C=C bonds within the polymer backbone, promoted by oxidative-dehydrogenation reaction. Supporting these observations, the fracture morphology examined by SEM showed a brittle fracture in the skin and ductile fracture in the core.     

Effect of the displacement reaction on the composition of the magnetic layer in electrodeposited layered nanostructures Co-Cu/Cu and Ni-Cu/Cu

Methods of stripping voltammetry, quartz microgravimetry, and x-ray-fluorescence analysis are employed to explore the copper displacement process on thin electrodeposited layers of pure cobalt and nickel and on deposits of these metals with inclusions of copper. The displacement reaction proceeds at a considerable rate on cobalt in the sulfate and sulfosalicylate solutions and virtually does not proceed on nickel in both the sulfate or sulfate-chloride solutions. An estimate of the rate of the copper displacement reaction following a change in the concentration of copper ions in the solution and in the pH of the sulfosalicylate solution is given. A decrease in the contact exchange rate is facilitated by a decrease in the concentration of copper ions in solution and their participation in the formation of complexes.