Differences in the redistribution of concanavalin A and wheat germ agglutinin binding sites on mouse neuroblastoma cells.

Concanavalin A (Con A), wheat germ agglutinin (WGA), and Ricinus communis agglutinin (RCA) bound with either 125I, fluorescent dyes, or fluorescent polymeric microspheres were used to quantitate and visualize the distribution of lectin binding sites on mouse neuroblastoma cells. As viewed by fluorescent light and scanning electron microscopy, over 10(7) binding sites for Con A, WGA, and RCA appeared to be distributed randomly over the surface of differentiated and undifferentiated cells. An energy-dependent redistribution of labeled sites into a central spot occurred when the cells were labeled with a saturating dose of fluorescent lectin and maintained at 37 degrees C for 60 min. Reversible labeling using appropriate saccharide inhibitors indicated that the labeled sites had undergone endocytosis by the cell. A difference in the mode of redistribution of WGA or RCA and Con A binding sites was observed in double labeling experiments. When less than 10% of the WGA or RCA lectin binding sites were labeled, only these labeled sites appeared to be removed from the cell surface. In contrast, when less than 10% of the Con A sites were labeled, both labeled and unlabeled Con A binding sites were removed from the cell surface. Cytochalasin B uncoupled the coordinate redistribution of labeled and unlabeled Con A sites, suggesting the involvement of microfilaments. Finally, double labeling experiments employing fluorescein-tagged Con A and rhodamine-tagged WGA indicate that most Con A and WGA binding sites reside on different membrane components and redistribute independenty of each other.     

Ultraviolet Radiation in the Rhône River Lenses of Low Salinity and in Marine Waters of the Northwestern Mediterranean Sea: Attenuation and Effects on Bacterial Activities and Net Community Production

The high content in nutrients of freshwater outflows induces highly productive and buoyant plumes spreading over marine waters (MW). As a consequence, the growth of organisms developing in these low‐salinity waters (LSW) might be potentially affected by UV‐R (280–400 nm). This study investigated the penetration of UV‐R and its impact on net community production (NCP) and bacterial protein (B_PROTS) and DNA (B_DNAS) synthesis in mesotrophic‐LSW formed from the Rhône River and in oligotrophic MW of the Northwestern Mediterranean Sea (Gulf of Lions) in May 2006. High concentrations of chlorophyll a (up to 8 μg L^?1) measured in the LSW (<37.8 psu, 0–10 m) were the main factor influencing the diffuse attenuation coefficients (K_d) of both UV‐R and photosynthetically active radiation (PAR). The mean ratio of the K_d measured between the LSW and the MW increased with wavelength from 2.4 at 305 nm to 2.9 at 380 nm and 3.1 for PAR indicating more similarity in the UV region. NCP was severely inhibited by UV‐R at the surface of the LSW, whereas no effect was measured in the surrounding MW. In contrast, B_PROTS and B_DNAS were affected deeper by UV‐R in the MW (up to 8 m depth) compared to the LSW where inhibition was only observed at the surface. Differences in response of bacteria in LSW and MW are largely explained by differences in UV‐R transparency; however, transplant experiments indicate that bacterial assemblages from the MW were also more sensitive to UV‐R than those present in the LSW. We also observed that higher activity of bacteria after nutrient additions increased their sensitivity to UV‐R during the day, but favored their recovery during the night incubation period for both LSW and MW. Results suggest that riverine and nutrient inputs may alter the effects of UV‐R on microbial activity by attenuating the UV‐R penetration and by modifying the physiology of bacteria.     

Poly(3-methylthiophene)/palladium sub-micro-modified sensor electrode. Part II: Voltammetric and EIS studies, and analysis of catecholamine neurotransmitters, ascorbic acid and acetaminophen

Promising voltammetric sensors based on the modification of Pt and poly(3-methylthiophene) (PMT) electrodes with Pd nanoparticles were achieved for the determination of catecholamine neurotransmitters, ascorbic acid and acetaminophen. Electrochemistry of the indicated compounds was studied at these electrodes and interesting electrocatalytic effects were found. Furthermore, simple, easily prepared one electrochemical step Pd-modified Pt electrode (Pt/Pd) is reported for the first time. Cyclic voltammetry (CV) and chronocoulometry (CC) were used for the determination of the apparent diffusion coefficients in different electrolytes at these electrodes and the values are in the range from 10⁻⁴ to 10⁻⁵ cm² s⁻¹. Furthermore, it was found that the method of polymer formation had a substantial effect on the synergism between the polymer film and the loaded metal particles towards the oxidation of dopamine (DA) in different supporting electrolytes. This was confirmed by the CV, CC and EIS (electrochemical impedance spectroscopy) as well as SEM (Scanning Electron Microscopy) results. Pt and PMT electrodes modified with Pd nanoparticles showed excellent results for the simultaneous determination of tertiary and quaternary mixtures of the studied compounds.     

Emodin,A Naturally Occuring Anthraquinone: Its Isolation and Spectrophotometric Determination in Rumex Cyprius Plant

A new method for isolation and specrophotometric determination of emodin is presented. Emodin was isolated by thin layer chromatography (tlc) and column chromatography (cc) techniques, as an orange long crystalline substance. Emodin exhibits two absorption maxima, at 420 and 520 nm. Stability of the color and the effect of pH were studied. Beer's law is obeyed in the range 2–30 ppm.

The method is applied to the determination of emodin in roots, stems, and leaves of Rumex cyprius plant.     

Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their mixtures XIII. 4-(4-Substituted phenylazo)phenyl 4-alkoxybenzoates

Five homologous series of 4-(4-substituted phenylazo)phenyl 4-alkoxybenzoates (Ia-e) were prepared in which the substituent (X) was taken from CH₃O, CH₃, Cl, NO₂, and CN, while, within each homologous series, the length of the terminal alkoxy group varied between 6 and 16 carbon atoms. Compounds prepared were characterized by infrared spectroscopy, and their mesophase behaviour investigated by differential scanning calorimetry and polarizing optical microscopy. The results are discussed in terms of mesomeric and polarizability effects. In each group of compounds bearing the same alkoxy group, the mesophase - isotropic transition temperatures (T_c) were successfully correlated with the polarizability anisotropy of bonds to the substituent X.     

Hirshfeld Surface Analysis,Crystal Structure and Spectroscopic Studies of a New Cu(II) Halocuprate Salt with Protonated N-Amino-Ethyl-Piperazine

(C₆H₁₈N₃)₄[CuCl₅]₂[CuCl₄]₃·1.42H₂O is prepared and characterized by various physicochemical techniques. The single crystal X-ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with the space group Cmca. Its unit cell dimensions are: a = 24.286(2) Å, b = 14.3082(14) Å, c = 16.6160(16) Å, Z = 4, V = 5773.8(10) ų. Its crystal structure is determined and refined down to R = 0.024 and wR(F²) = 0.059. The structure contains three crystallographically independent Cu²⁺ ions coordinated to chlorine anions in various fashions. Cu1 is five-coordinated in a distorted square pyramidal fashion, while Cu2 and Cu3 are four-coordinated in square planar and distorted tetrahedral fashions, respectively. The entities are interconnected by means of the hydrogen bonding [O(W)–H…Cl, N–H…Cl, C–H…Cl and C–H…O(W)], forming a three-dimensional network. Intermolecular interactions are investigated by Hirshfeld surfaces and the contacts of the eight different chloride atoms are notably compared. The vibrational absorption bands are identified by infrared spectroscopy. The optical study is performed by UV-vis absorption.     

Equilibrium geometry and electronic structure of benzylidene,arylethylidene, and heterocyclic arylidene malononitriles

The equilibrium geometry of some benzylidene, arylethylidene, and heterocyclic arylidene malononitriles has been calculated within the framework of the MNDO –MO formalism. Various structural factors are analyzed and discussed in terms of localized and delocalized MOS and π-interaction between methylene malononitrile (MMN) and aryl moieties. The possibility of charge transfer (CT ) from aryl to MMN moieties has been examined. The presence of a heterocyclic ring introduces a small perturbation into the MMN nuclear frame. p-Substituents have a pronounced effect on the magnitude and direction of the dipole moment. The variation of ionization potentials and bond order with the Hammet σ p are examined and a straight-line relationship is obtained. The correlation between physiological activity and quantum mechanical properties is analyzed in terms of heat of formation, ionization potential, dipole moment, and charge density on the aryl ring. © 1994 John Wiley & Sons, Inc.     

Quantitative two-dimensional gel electrophoresis analysis of human fibroblasts transformed by ras oncogenes.

Quantitative two-dimensional gel electrophoresis was used to compare the cellular protein patterns of a normal foreskin-derived human fibroblasts cell line (LG1) and three immortal derivatives of LG1. One derivative, designated MSU-1.1 VO, was selected for its ability to grow in the absence of serum and is non-tumorigenic in athymic mice. The other two strains were selected for focus-formation following transfection with either Ha-ras or N-ras oncogenes and form high grade malignant tumors. Correspondence and cluster analysis provided a nonbiased estimate of the relative similarity of the different two-dimensional patterns. These techniques separated the gel patterns into three distinct classes: LG1, MSU-1.1 VO, and the ras transformed cell strains. The MSU-1.1 VO cells were more closely related to the parental LG1 than to the ras-transformed cells. The differences between the three classes were primarily quantitative in nature: 16% of the spots demonstrated statistically significant changes (P < 0.01, T test, mean ratio of intensity > 2) in the rate of incorporation of radioactive amino acids. The patterns from the two ras-transformed cell strains were similar, and variations in the expression of proteins that occurred between the separate experiments obscured consistent differences between the Ha-ras and N-ras transformed cells. However, while only 9 out of 758 spots were classified as different (1%), correspondence analysis could consistently separate the two ras transformants. One of these spots was five times more intense in the Ha-ras transformed cells than the N-ras.(ABSTRACT TRUNCATED AT 250 WORDS)     

Unsaturated bridgehead silicon intermediates. Dipolar character of unsaturated siliconnitrogen bonds in such intermediates

Photolysis of 1-azido-1-silabicyclo[2.2.1]heptane and 1-azido-1-silabicyclo[2.2.2.]octane give loss of nitrogen and rearrangement with ring enlargement yielding silaimine reaction intermediates which were trapped by reaction with methyltrimethoxysilane and triethoxysilane. Evidence is presented which indicates that the unsaturated siliconnitrogen bonds in the intermediates have considerable polar character and do not behave like triplet diradicals. The balance of the evidence favors, but does not completely prove, that the intermediates have significant π-bonding.