Copper Extraction Kinetics by Beta-Diketone Derivatives (Acylpyrazolones and Acylisoxazolones) in Water/Chloroform Biphasic System

Abstract

Copper(II) extraction and back-extraction rates were determined in a water/chloroform system using a bell-shaped transport cell. Various 1-phenyl-3-methyl-4-acyl-pyrazol-5-ones (with acyl = benzoyl, 2-thenoyl, octadecanoyl, p-tert-butylbenzoyl, 3-phenyl-propanoyl, and iso-nonanoyl) and 3-phenyl-4-acylisoxazol-5-ones (with acyl = benzoyl and p-tert-butylbenzoyl) were considered. The back-extraction rate is shown to be limited by the diffusion of the complex in the organic unstirred layer, whatever the stirring speed and whatever the ligand considered. At low stirring speed, the extraction rate appears to be limited by the diffusion of either a complex or a ligand species in the unstirred layers, depending on the pH. At high stirring speed, the extraction rate is limited by the interfacial complexation. The extraction rate dependence on side-group variation cannot be correlated with hydrophobicity or acidity of the extractants and may be explained by structural differences of the CO vicinal group of the acyl.     

Phe496 and Leu497 are essential for receptor binding and cytotoxic action of the murine interleukin-4 receptor targeted fusion toxin DAB389-mIL-4

DAB₃₈₉-mIL-4 is a murine interleukin-4 (mIL-4) diphtheria toxin-relatedfusion protein which has been shown to be selectively toxicto cells expressing the mIL-4 receptor. In this report, we haveused site-directed and in-frame deletion mutagenesis to studythe role of the putative C-terminal -helix (helix E) of themIL-4 component of DAB₃₈₉-mIL-4 in the intoxication process.We demonstrate that deletion of the C-terminal 15 amino acidsof the fusion toxin leads to loss of cytotoxicity. The substitutionof Phe496 with either Pro, Ala or Tyr, results in a > 20-folddecrease in cytotoxic activity of the respective mutant fusiontoxins. In addition, substitution of Leu497 with either Alaor Glu results in a similar loss of cytotoxic activity. Allof these mutant forms of the mIL-4 fusion toxin demonstratea significant decrease in binding affinity (K_i) to the mIL-4receptor in a competitive radioligand binding assay. In markedcontrast, however, the substitution of Asp495 with Asn resultsin a 4-fold increase in cytotoxic potency and binding affinityto mIL-4 receptor bearing cells in vitro.     

Enhancing the super exponential method of blind equalisation withthe fast RLS Kalman algorithm

A method for efficiently implementing super exponential (SE) blind equalisation is proposed. The method, based on fast Kalman filtering theory, is recursive in order and in time, and leads to a significant reduction in the number of arithmetic operations. Using the order update by partitioning the covariance matrix of the first hundred data in a specific form, a fast initialisation is implemented. The resulting algorithm achieves the same theoretical fast convergence characteristics as the original SE algorithm but with a significant reduction in arithmetic operations     

An approach to radar imaging using the spherical projection density concept*

High resolution radar imaging is used to perform target signature analysis. In this paper, we present a comparative study of diverse 2- D imaging methods on spherical waves, such as sar processing and its modes, ssar and isar as well as holography, whose mathematical formulation is identical by using the spherical projection density function, although the measurement technique are quite different. We show that azimuth processing is unified, and under some conditions range processing can be unified. In order to reconstruct the fixed target side looking radar image, we have developed an idea based on the transformation of antenna lateral displacement as a function of equivalent angular displacement, and then the 1- D images coherent summation algorithm of classical holography can be used.     

Seroprevalence of Norwalk virus and Mexico virus in Chilean individuals: assessment of independent risk factors for antibody acquisition

Norwalk virus (NV) and Mexico (MX) virus represent distinct genetic clusters within the same genus of human caliciviruses (CVs), a major cause of diarrhea in adults. The magnitude and potential risk factors of human CV infection in populations from Santiago and Punta Arenas, Chile, were assessed. Individuals (n = 1,864) gave a blood sample and answered a questionnaire during a household survey. Sera were tested for antibody to NV and MX virus with use of recombinant capsid antigens. Overall, NV and MX virus seroprevalence rates were 83% and 91% in Santiago vs. 67% and 90% in Punta Arenas, respectively (P < .001 for NV virus). Lower socioeconomic status and increasing age were risk factors for infection with both viruses (P < .001). Consumption of seafood, consumption of vegetables, and child care center attendance were population risk factors for infection, but the association of a factor with a virus depended on the city. Prevention of human CV infections will require individual assessment in different communities.     

The catalytic properties of murine carbonic anhydrase VII

Carbonic anhydrase VII (CA VII) appears to be the most highly conserved of the active mammalian carbonic anhydrases. We have characterized the catalytic activity and inhibition properties of a recombinant murine CA VII. CA VII has steady-state constants similar to two of the most active isozymes of carbonic anhydrase, CA II and IV; also, it is very strongly inhibited by the sulfonamides ethoxzolamide and acetazolamide, yielding the lowest Ki values measured by the exchange of 18O between CO2 and water for any of the mammalian isozymes of carbonic anhydrase. The catalytic measurements of the hydration of CO2 and the dehydration of HCO3- were made by stopped-flow spectrophotometry and the exchange of 18O using mass spectrometry. Unlike the other isozymes of this class of CA, for which Kcat/K(m) is described by the single ionization of zinc-bound water, CA VII exhibits a pH profile for Kcat/K(m) for CO2 hydration described by two ionizations at pKa 6.2 and 7.5, with a maximum approaching 8 x 10(7) M-1 s-1. The pH dependence of kcat/K(m) for the hydrolysis of 4-nitrophenyl acetate could also be described by these two ionizations, yielding a maximum of 71 M-1 s-1 at pH > 9. Using a novel method that compares rates of 18O exchange and dehydration of HCO3-, we assigned values for the apparent pKa at 6.2 to the zinc-bound water and the pKa of 7.5 to His 64. The magnitude of Kcat, its pH profile, 18O-exchange data for both wild-type and a H64A mutant, and inhibition by CuSO4 and acrolein suggest that the histidine at position 64 is functioning as a proton-transfer group and is responsible for one of the observed ionizations. A truncation mutant of CA VII, in which 23 residues from the amino-terminal end were deleted, has its rate constant for intramolecular proton transfer decreased by an order of magnitude with no change in Kcat/K(m). This suggests a role for the amino-terminal end in enhancing proton transfer in catalysis by carbonic anhydrase.     

On the stability of the troposphere/lower stratosphere and its relationships with cirrus clouds and three mandatory levels over Buenos Aires

An unrotated principal components analysis was carried out to establish the most representative modes for the joint variability between the heights of the upper and lower boundaries of cirrus clouds and three different mandatory levels (850, 500, and 100 hPa), and the associated stability of the troposphere over Buenos Aires. Discussion is limited to the first three most representative structures found, which consists of spatial patterns (or empirical orthogonal functions, EOFs) and their time-evolving coefficients (or principal components, PCs). EOF₁ shows a direct (indirect) mode that encompasses the cirrus slightly below (above) its mean position, with 500 and 100 hPa exhibiting a similar behaviour and 850 hPa acting the opposite way. EOF₁ is associated with above-normal stability (instability) for direct (indirect) modes (i.e. positive (negative) values of PC₁). On a monthly average, this occurs in the austral winter (summer) months. Regarding EOF₂, all three mandatory levels experience positive (negative) height anomalies in direct (indirect) modes and cirrus goes up (down) under mild stability (instability). Monthly averages show that PC₂ is approximately positive in summer and in early fall and negative the rest of the year. As to EOF₃, it is characterized by a stability similar to that of EOF₂, with direct (indirect) modes showing lowered (raised) cirrus and all three mandatory levels above (below) normal conditions; on a monthly basis, PC₃ is best described as having a semi-annual evolution, with maxima (minima) in March and October (January and August). Overall, EOF₁ has the highest stability or instability, depending upon the sign of PC₁. These results are the first of their kind worldwide.     

Microfluidic transistors for analog microflows amplification and control

Two microfluidic transistors for analog flow control and amplification for lab-on-a-chip applications are presented. The transistors are based on the elastic membrane microchannel, where the flow in the microchannel between the substrate and the membrane is controlled by the pressure differences along the channel and across the membrane. Reduced-order models that capture the low-inertia dynamic behavior of the coupled fluid–structure interaction were developed to enable fast small-signal analysis of large circuits. The accuracy of the models is assessed by comparing to numerical simulations of the coupled fluid–structure interaction problem. Analog behavior (based on analytical modeling and numerical simulation) of the two devices is characterized in terms of dependence of the volume flow rate on the source–drain and gate–source pressure differences, analogous to the characterization of MOSFET operation. The characteristic curves are then used to extract the small-signal parameters (transconductance and intrinsic output resistance), characterizing the dynamic response to small time-varying pressures at the gate and/or drain. The characterization enabled identification of the various static and dynamic operation regimes of the devices, including the transistive regime where the device operates as amplifier, and the capacitive (positive and negative) regimes. Finally, the dual-membrane transistor is used to showcase its use as a diode and a common-source amplifier in the design of a micropump that, in turn, is used for mixing of two species using pulsating flows.