ATP-Dependent human erythrocyte glutathione-conjugate transporter. I. Purification, photoaffinity labeling, and kinetic characteristics of ATPase activity

Dinitrophenyl S-glutathione (DNP-SG) ATPase is a 38 kDa membrane protein expressed in erythrocytes and other tissues. Although stimulation of ATP hydrolysis catalyzed by DNP-SG ATPase has been demonstrated in the presence of several structurally unrelated amphiphilic ions, structural and functional properties of this protein have not been well-defined. In the present study, we have developed an improved protocol for the purification of DNP-SG ATPase and investigated its kinetic and substrate-binding properties. The purification procedure was based on highly specific elution of the 38 kDa protein from DNP-SG affinity resin in the presence of ATP. The protein could not be eluted using either ADP or adenosine-5'-[beta,gamma-methylene]triphosphate (methylene-ATP), a nonhydrolyzable analogue of ATP. Doxorubicin (DOX), a weakly basic anthracycline chemotherapy agent, was found to be the preferred activator for stimulation of ATP hydrolysis by the enzyme. ATP binding to the enzyme was demonstrated using 8-azido-ATP photoaffinity labeling and binding of trinitrophenyl (TNP)-ATP, a fluorescent analogue of ATP. The photoaffinity labeling of DNP-SG ATPase (38 kDa) was saturable with respect to 8-azido ATP (Kd = 2 microM), indicating that the enzyme was capable of specific and saturable binding to ATP. DNP-SG binding was evident from the purification procedure itself and was also demonstrable by quenching of tryptophan fluorescence. Results of quenching of tryptophan fluorescence as well as radioactive isotope-binding studies indicated that DOX was bound to the purified protein as well.     

Transmission parameters of a class of coupled distributed networks

It is shown how the equations of a class of coupled distributed networks can be decoupled, and their transmission parameters expressed in terms of those of an equivalent scalar system.     

M.O.S. switched-capacitor amplifiers

Switched-capacitor voltage gain elements, in which the gain is precisely controlled by the ratio of two capacitors, are presented. The voltage gain is obtained by means of a transconductance element operating into a switched-capacitor resistor. Circuit configurations use a single operational amplifier or a unity-gain buffer. In some of these configurations, the offset voltage of the operational amplifier or the buffer is not amplified.     

Application of spherical and other polymers in capillary zone electrophoresis: separation of antiviral drugs and deoxyribonucleoside phosphates by different principles

Soluble polymers of linear chains with limited branching and spherical polymers (limit dextrins and sucrose, such as Dextran and Ficoll (Pharmacia Chemicals), yielding lower viscosities, are examined here for the separation of different nucleotides and several anti-AIDS drugs by capillary zone electrophoresis (CZE). The linear polymer forms a network but spherical polymers appear to create a second pseudo-phase. In general, they tend to enhance the solute mobility and reduce peak width; thus, they improve the column efficiency. We observe that the beads of a spherical polymer produce a pseudo-phase even in a very low polymer concentration. The proposed method involving a spherical polymer yields the best separation for twelve deoxyribonucleoside mono-, di- and triphosphates in ca. 10 min. Common anti-AIDS drugs (ddA, ddC, ddI, d4T, AZT) and an AZT metabolite (AZT-glucuronate) are resolved by using conventional micellar electrokinetic capillary chromatography (MEKC). These results not only offer fast and highly sensitive detection techniques for the pharmacokinetics of nucleotides, drugs, and their metabolites, but they also demonstrate an application of the proposed second pseudo-phase involving spherical polymer beads in CZE separations.     

Direct electrochemical detection of purine- and pyrimidine-based nucleotides with sinusoidal voltammetry

Sinusoidal voltammetry was employed to detect both purine- and pyrimidine-based nucleic acids. Adenine and cytosine, representing these two classes of nucleic acids, could be measured with submicromolar detection limits at a copper electrode under these conditions, where the sensitivity for adenine was much higher than that for cytosine. Detection limits for purine-containing nucleotides [e.g., adenosine 5'-monophosphate (AMP), adenosine 5'-diphosphate (ADP), and adenosine 5'-triphosphate (ATP)] were on the order of 70-200 nM using this method. These detection limits are achieved for native nucleotides and are over 2 orders of magnitude lower than those found with UV absorbance detection. Submicromolar detection limits were also obtained for pyrimidine-based nucleotides, which could also be detected with high sensitivity due to the presence of a sugar backbone that is electroactive at the copper surface. This detector is not fouled by the nucleotides and may be used for the sensitive detection of analytes eluting continuously in a flowing stream, i.e., from a chromatography column or an electrophoresis capillary.     

Multi-channel local ternary pattern for content-based image retrieval

Pattern Analysis and Applications - A feature based on a single modality such as color or texture is not sufficient to investigate the appearance variation across multiple images. In this paper, a...     

Majorization Minimization Technique for Optimally Solving Deep Dictionary Learning

The concept of deep dictionary learning (DDL) has been recently proposed. Unlike shallow dictionary learning which learns single level of dictionary to represent the data, it uses multiple layers of dictionaries. So far, the problem could only be solved in a greedy fashion; this was achieved by learning a single layer of dictionary in each stage where the coefficients from the previous layer acted as inputs to the subsequent layer (only the first layer used the training samples as inputs). This was not optimal; there was feedback from shallower to deeper layers but not the other way. This work proposes an optimal solution to DDL whereby all the layers of dictionaries are solved simultaneously. We employ the Majorization Minimization approach. Experiments have been carried out on benchmark datasets; it shows that optimal learning indeed improves over greedy piecemeal learning. Comparison with other unsupervised deep learning tools (stacked denoising autoencoder, deep belief network, contractive autoencoder and K-sparse autoencoder) show that our method supersedes their performance both in accuracy and speed.     

Effect of heat treatment on dielectric relaxation of polyacrylonitrile: Reversible thermally induced structural change

The effect of heat treatment on the dielectric relaxation of polyacrylonitrile (PAN) was studied. Dielectric measurements, in the frequency range 0.1–100 kHz and temperature range 30–170°C, on PAN heat treated at two temperatures (120 and 160°C) and the untreated PAN are reported. The loss peak height, the dielectric relaxation strength, loss peak width, and the loss peak temperature were found to vary systematically with the temperature of the heat treatment. The changes in dielectric relaxation produced by heat treatment at the higher temperature (i.e., 160°C) were considerably less than those produced by heat treatment at 120°C. The results are discussed and attributed to the variation of the degree of bound nitrile groups (through their dipole–dipole interaction) with heat treatment temperature. Heat treatment of the higher temperature (160°C) results in lower degree of bound nitrile groups in the structure than heat treatment at the lower temperature (120°C).