Indolyl-naphthyl-maleimides as potent and selective inhibitors of protein kinase C-α/β

The indolyl-naphthyl maleimide 7 is a potent inhibitor of the classical PKC isotypes α,β and shows excellent selectivity over the novel PKC isotypes δ,ε,η,θ and other kinases belonging to the AGC family. The SAR around 7 as well as the physico-chemical characteristics of selected derivatives and their activity in T and B cell activation and proliferation assays are discussed.     

Phospholipids, free sterols and adenosine triphosphatase of plasma membrane-enriched preparations from roots of citrus genotypes differing in chloride exclusion ability

Plasma membrane-enriched preparations from fibrous roots of three citrus genotypes differing in their abilities for chloride exclusion, and grown in the presence of 0,50 or 100 mM NaCl for 4 weeks, were analysed for phospholipid and free sterol content and vanadate-sensitive adenosine triphosphatase (ATPase) activity over a range of temperatures. The best chloride excluder, Rangpur lime (Citrus reticulaia Blanco var. austera hyb.?), had significantly higher maximal ATPase activity than both the moderate chloride excluder. Kharna khatta (Citrus kharna Raf.), and the worst chloride excluder, Etrog citron (Citrus medico L.), at all assay temperatures below 28°C. Salt treatment had no effect on maximal ATPase activity of either Rangpur lime or Etrog citron but resulted in increased activity of the enzyme in Kharna khatta at temperatures below 28°C. Arrhenius plots of ATPase activity from the three citrus genotypes showed that, in controls, the activation energy (E.,) of Rangpur lime ATPase was significantly lower than that of both Kharna khatta and Etrog citron. The thermotropic phase transition temperature (T_f) for Rangpur lime (27°C) was also lower than for the other citrus genotypes (31°C). Salt treatment resulted in increases in both Ea and T, for Rangpur lime, decreases in both parameters for Kharna khatta and no change of either parameter for Etrog citron. An inverse relationship between E_a and the phospholipid to free sterol ratio was evident for plasma membrane preparations from all three citrus genotypes in the presence and absence of salt treatment suggesting that changes in membrane fluidity, particularly those induced by free sterols, have the potential to influence active as well as passive ion transport processes and thus may play a significant role in the chloride exclusion mechanism.     

Elevation in Plasma Abeta42 in Geriatric Depression: A Pilot Study

Elevated plasma amyloid beta 1–42 (Aβ42) level has been linked to increased risk for incident AD in cognitively-intact elderly. However, plasma Aβ levels in individuals with late-life depression (LLMD), especially those with a late age of onset of first depressive episode, who are at a particularly increased risk for Alzheimer’s disease, have not been studied. We compared plasma Aβ in 47 elderly with LLMD with 35 controls and examined its relationships to age of onset of first depressive episode, antidepressant treatment (paroxetine or nortriptyline), and indices of platelet activation (platelet factor 4 and beta-thromboglobulin) and brain abnormalities. Results indicated that plasma Aβ42 levels and the Aβ42/40 ratio were elevated in the LLMD group relative to controls in the overall group analyses and in the age- and gender-matched groups. MRI data indicated that higher Aβ42/40 ratio was associated with greater severity of total white matter hyperintensity burden in LLMD. Plasma Aβ levels in LLMD were not influenced by age of onset of first depressive episode or antidepressant treatment and were not related to indices of platelet activation. Our preliminary results suggest that increased plasma Aβ42 and Aβ42/40 ratio are present in geriatric depression, and future studies should be done to confirm these findings and to determine their relationship to cognitive decline and brain abnormalities associated with LLMD.Presented at the 43rd Annual Meeting, American College of Neuropsychopharmacology, San Juan, Puerto Rico, December 12–16, 2004.     

Transport of ions across peritoneal membrane

The electrical conductance of ions across the peritoneal membrane of young buffalo (approximately 18-24 months old) has been recorded. Aqueous solutions of NaF, NaNO₃, NaCl, Na₂SO₄, KF, KNO₃, KCl, K₂SO₄, MgCl₂, CaCl₂, CrCl₃, MnCl₂, FeCl₃, CoCl₂, and CuCl₂ were used. The conductance values have been found to increase with increase in concentration as well as with temperature (15 to 35 °C) in these cases. The slope of plots of specific conductance, κ, versus concentration exhibits a decrease in its values at relatively higher concentrations compared to those in extremely dilute solutions. Also, such slopes keep on increasing with increase in temperature. In addition, the conductance also attains a maximum limiting value at higher concentrations in the said cases. This may be attributed to a progressive accumulation of ionic species within the membrane. The κ values of electrolytes follow the sequence for the anions: SO₄²⁻>Cl⁻>NO₃⁻>F⁻ while that for the cations: K⁺>Na⁺>Ca²⁺>Mn²⁺>Co²⁺>Cu²⁺>Mg²⁺>Cr³⁺>Fe³⁺. In addition, the diffusion of ions depends upon the charge on the membrane and its porosity. The membrane porosity in relation to the size of the hydrated species diffusing through the membrane appears to determine the above sequence. As the diffusional paths in the membrane become more difficult in aqueous solutions, the mobility of large hydrated ions gets impeded by the membrane framework and the interaction with the fixed charge groups on the membrane matrix. Consequently, the membrane pores reduce the conductance of small ions, which are much hydrated. An increase in conductance with increase in temperature may be due to the state of hydration, which implies that the energy of activation for the ionic transport across the membrane follows the sequence of crystallographic radii of ions accordingly. The Eyring's equation, κ=(RT/Nh)exp[−ΔH*/RT]exp[ΔS*/R], has been found suitable for explaining the temperature dependence of conductance in the said cases. This is apparent from the linear plots of log[κNh/RT] versus 1/T. The results indicate that the permeation of ions through the membrane giving negative values of ΔS* suggest that there may be formation of either covalent linkage between the penetrating ions and the membrane material or else the permeation may not be the rate-determining step. On the one hand, a high ΔS* value associated with the high value of energy of activation, E_a, for diffusion may suggest the existence of either a large zone of activation or loosening of more chain segments of the membrane. On the other hand, low value of ΔS* implies that converse is true in such cases, i.e., either a small zone of activation or no loosening of the membrane structure upon permeation.     

Misclassification of ELF occupational exposure resulting from spatial variation of the magnetic field

The adequacy of a single hip- or chest-worn magnetic field dosimeter to reliably classify subjects with respect to their occupational ELF magnetic field exposure is investigated. Hip-worn dosimeters consistently underestimate both whole-body average exposure and head exposure, tentatively regarded here as two possible definitions of the “true” exposure measurement. The approximate resulting bias in the relative risk estimate in hypothetical case-control studies is evaluated. A chest-worn dosimeter is found to be generally superior to a hip-worn one in assessing exposure during the occupational tasks considered here. © 1993 Wiley-Liss. Inc.     

What is the Binding Energy of a Charge Transfer State in an Organic Solar Cell?

The high efficiencies reported for organic solar cells and an almost negligible thermal activation measured for the photogeneration of charge carriers have called into question whether photoinduced interfacial charge transfer states are bound by a significant coulomb attraction, and how this can be reconciled with very low activation energies. Here, this question is addressed in a combined experimental and theoretical approach. The interfacial binding energy of a charge‐transfer state in a blend of MeLPPP:PCBM is determined by using energy resolved electrochemical impedance spectroscopy and is found to be about 0.5 eV. Temperature‐dependent photocurrent measurements on the same films, however, give an activation energy that is about one order of magnitude lower. Using analytical calculations and Monte Carlo simulation the authors illustrate how i) interfacial energetics and ii) transport topology reduce the activation energy required to separate the interfacial electron–hole pair, with about equal contributions from both effects. The activation energy, however, is not reduced by entropy, although entropy increases the overall photodissociation yield.     

Das Gesetz der absoluten Geschwindigkeiten biologischer Prozesse

The dependency of the velocity of biological processes from the temperature is described by the “Law of absolute velocity of biological processes”, which has only the individual parameters energy of activation ΔE, and the universal constant C. The law holds for all biological processes and is expressed by the equation: where C is: .     

Functional signaling of membrane-bound TL1A induces IFN-γ expression

TL1A, a TNF member implicated in autoimmune diseases, is a transmembrane protein that is processed to release soluble TL1A (TL1A-S). TL1A-S induces a Th1 response, although the functional significance of membrane-bound TL1A (TL1A-M) remains unknown. We generated TL1A-M expression in HEK-293 cells capable of binding DR3-Fc. Co-incubating IL-12/IL-18-primed CD4⁺ T cells with HEK-293 cells expressing TL1A-M induced 3-fold increase in IFN-γ that was blocked by anti-TL1A Ab. These results demonstrate that TL1A-M can bind death domain receptor 3 (DR3) through cell-cell contact to induce downstream IFN-γ secretion enhancement. Anti-TL1A antibodies designed to treat immune diseases should be verified to block both endogenous TL1A forms.     

Role of the protein's low dielectric constant in the functioning of the photosynthetic reaction center

The high efficiency of the energy storage in the photosynthetic reaction center (RC) is determined by a successful competition of electron transfer from bacteriopheophytin to quinone, as compared to backward recombination of the primary charge-separated state. This relationship is caused by a fine matching of the reorganization energy and the free energy gap making the forward processes activationless, and hence very fast, and mismatching of these two quantities for the backreaction, therefore retarding it strongly. In this study, we show that this matching is due to a low dielectric constant of the RC's protein core because a low dielectric affects strongly electrostatic polarization components of both the reorganization energy and the equilibrium free energy of reaction. If the protein and membrane were replaced by a homogeneous medium with a high dielectric constant, the effective energy storage would be impractical.     

Activation of the alternative complement pathway and generation of stimulating factors for granulocytes by glass fibers

Continuous-filament glass fibers coated with organic agents, candidate asbestos substitutes, were assessed for their ability to elicit from normal human serum complement-derived cleavage products which are able to stimulate the chemotaxis and the respiratory burst of polymorphonuclear leukocytes. Glass fibers generated chemoattracting and respiratory stimulating factors for polymorphonuclears from human serum. The effect was dose related for chemotaxis from the serum fiber concentration of 75 g/ml to 1,250 g/ml. The serum chemoattracting activity, as well the respiratory stimulation, were dramatically impaired when serum had been preliminarily absorbed with antiC5 antiserum. Since the impairment of chemotactic activity occurred also in the presence of EDTA, but not in the presence of EGTA, we assumed an activation of the alternative complement pathway.Glass fibers were studied in comparison to a UICC sample of Canadian chrysotile asbestos, which is able to activate in vitro the alternative complement pathway.Glass fibers exhibited less ability than asbestos fibers to generate complement cleavage products with chemotactic activity for polymorphonuclears; however, they produced an activity about equal to 80% of a chemotactic standard stimulus such as zymosan-activated plasma.Abbreviations AF asbestos fibers - antiCS-abs-S NHS absorbed with antiserum against C5 - EDTA-CH-S NHS treated with EDTA - EGTA-Ch-S NHS treated with EGTA - GF continuous filament glass fibers coated with a binder of organic substances - NHP normal human plasma - NHS normal human serum - PMN polymorphonuclear luekocytes - ZAP zymosan-activated plasma     

Behavior of Aromatic Molecules in Silicalite by the Direct Integration of the Configurational Integral

Abstract

Adsorption data of aromatic molecules adsorbed in silicalite show highly unusual characteristics which were attributed to structural effects caused by the comparable size of molecules and pores. In this study, the interaction of aromatic compounds with silicalite are examined on the molecular level. The interactions are calculated by atom-atom approximation using Lennard-Jones potentials. The constants are calculated, without fitting, from Kirkwood-Muller formulas. Benzene and p-xylene are represented as a rigid structure of 12 and 18 atom centers. The model is anisotropic.

The diffusional behavior of molecules is examined by minimizing the potential energy in the channels which requires less computational time than Molecular Dynamics. The activation energy for the diffusion of benzene, 27.6 kJ/mol, is in excellent agreement with data, 28.8 kJ/mol. The results indicate that both molecules can enter the smaller zig-zag channels. The energetically most favorable location in the main channels is the mid-point between intersections. All rotations are restricted in the channels but the molecules can rotate in any direction (with some movement of the center) at intersections.

The Henry's law constant and internal energy of adsorption at zero coverage are calculated by direct integration of the configurational integral. Direct integration is more efficient than Monte Carlo and Molecular Dynamics simulations since the molecules are highly restricted in the pores. The predicted internal energy of adsorption, ? 54.86 and ? 75.30 kJ/mol for benzene and p-xylene is in good agreement with data of ? 50.92 and ? 62.15 kJ/mol respectively. There is appreciable difference between the predicted and experimental Henry's law constants. The agreement can be improved by fitting the Lennard-Jones constants which has not been attempted.

Although the calculations are performed at infinite dilution and entropy effects are not included, the results bring insight to the behavior of molecules in highly restricted environments such as in tight pores. Similar simplified calculations can be used to close the gap between highly idealized molecular simulations and complicated systems common in real applications.     

Amyloid formation by recombinant full-length prion proteins in phospholipid bicelle solutions

A soluble, oligomeric beta-sheet-rich conformational variant of recombinant full-length prion protein, PrP beta, was generated that aggregates into amyloid fibrils, PrP betaf. These fibrils have physico-chemical and structural properties closely similar to those of pathogenic PrP Sc in scrapie-associated fibrils and prion rods, including a closely similar proteinase K digestion pattern and Congo red birefringence. The conformational transition from PrP C to PrP beta occurs at pH 5.0 in bicellar solutions containing equimolar mixtures of dihexanoyl-phosphocholine and dimyristoyl-phospholipids, and a small percentage of negatively charged dimyristoyl-phosphoserine. The same protocol was applicable to human, cow, elk, pig, dog and mouse PrP. Comparison of full-length hPrP 23-230 with the N-terminally truncated human PrP fragments hPrP 90-230, hPrP 96-230, hPrP 105-230 and hPrP 121-230 showed that the flexible peptide segment 105-120 must be present for the generation of PrP beta. Dimerization of PrP C represents the rate-limiting step of the PrP C-to-PrP beta conformational transition, which is dependent on the amino acid sequence. The activation enthalpy of dimerization is about 130 kJ/mol for the recombinant full-length human and bovine prion proteins, and between 260 and 320 kJ/mol for the other species investigated. The in vitro conversion assay described here permits direct molecular characterization of processes that might be closely related to conformational transitions of the prion protein in transmissible spongiform encephalopathies.     

Plant distribution and the temperature coefficient of metabolism

The spatial distribution of a plant species is limited by the range of climatic conditions to which the species can adapt. Temperature is one of the most significant determinants of plant distribution, but except for the effects of lethal limits, little is known about physiological changes in responses to differences in environmental temperature. In this study, temperature coefficients of non-photosynthetic metabolism have been determined in the normal environmental temperature range for selected annual and perennial plants. Distinct differences were found in the temperature coefficient of metabolism of woody perennial plants from high latitudes and high elevations and closely related low-latitude and low-elevation plants. Low-latitude and low-elevation woody perennials have Arrhenius temperature coefficients for metabolism that are larger than those for congeneric high-latitude and high-elevation plants. The Arrhenius temperature coefficient is not rapidly adapted to new environments. A simple function was developed relating Arrhenius temperature coefficient to latitude and elevation for accessions of three, woody, perennial species complexes of plants collected from a wide geographic range but grown in common gardens. Within these taxa, plants that experience broader ranges of temperature during growth in their native habitat have smaller temperature coefficients. Temperature coefficients also varied with growth stage or season. No similar relationship was found for annuals and herbaceous perennials. For the plants tested, Arrhenius temperature coefficients are high during early spring growth, but shift to lower values later in the season. The shift in Arrhenius temperature coefficients occurs early in the season for southern and low-elevation plants and progressively later for plants from further north or higher elevation. The changes in Arrhenius temperature coefficients result largely from increases in plant metabolic rates at lower temperatures while little change occurs in the rates at higher temperatures. Altering the temperature dependence of the control of metabolic rate is apparently an important means of response to climate change.     

固定化硝化细菌耐低温机理的研究

氨随污水排入水体．不但能诱发“富营养化”,造成水生生态系统紊乱,而且还有如下危害：(1)消耗溶解氧,导致水体缺氧;(2)影响鱼鳃的氧传递,严重时使鱼类死亡;(3)与氯气作用生成氯胺,妨碍氯化消毒处理^[1]。对于氨污染的控制．目前国内外主要采用生物脱氮技术。即硝化．反硝化工艺^[2]。由于硝化细菌生长缓慢(在低温下则生长更慢)．一些学者作了固定化细胞的尝试．以期持留足量的生物体,改瞢生物反应器的运作性能^[3,4]。研究发现,固定化硝化细菌具有较强的耐低温能力^[4]。这对含氨废水的冬季生物处理十分有益。本文拟就固定化细胞的耐低温机理作一探讨。