DIADEM — A system for the interactive data acquisition and processing in an analytical laboratory

Peters, Frens; Teschner, Wolfgang

doi:10.1016/0010-468x(79)90059-x

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…The collapse of the electrical field of 1 kV/cm during the temperature jump was much too small to damage the membrane irreversibly (Teissie & Tsong, 1981;Stulen, 1981;Grell, 1981). The relaxation curves were processed on-line and analyzed as described by Peters & Teschner (1979). The fast temperature jumps were performed in parallel with the slow temperature jumps at the same time after sample preparation.…”

Section: Methodsmentioning

confidence: 99%

Kinetics of the subtransition of asymmetrically substituted phosphatidylcholines

Tümmler¹,

Herrmann²,

Maaß³

et al. 1984

Biochemistry

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The thermodynamics and kinetics of the subtransition L epsilon----P beta of sonicated unilamellar vesicles of 1-myristoyl-2-stearoylphosphatidylcholine (1M-2S-PC) and of 1-stearoyl-2-myristoylphosphatidylcholine (1S-2M-PC) were studied by equilibrium cooling curves and temperature-jump relaxation spectrometry with an anthracenophane cryptand as a mobile fluorescent probe. The unilamellar vesicles exhibit the midpoint temperature TsII of the subtransition about 10 degrees C below the respective main transition. The kinetics of the subtransition in the time range between 10(-4) and 10(3) s is characterized by a cooperative relaxation process in the range of milliseconds and a further noncooperative process in the range of seconds. The slow process is assigned to the rearrangement of lattice defects. The fast process is evaluated in terms of a cyclic reaction scheme that consists of two pathways for the biomolecular association of probe and vesicle coupled with the conformational change of the lipid matrix during the subtransition. The analysis reveals that the fast process comprises the nucleation and growth of cluster. The cooperative lattice transformation of the subtransition follows a first-order rate law. The rate constants at TsII are 70 s-1 for 1S-2M-PC and 170 s-1 for 1M-2S-PC. Since the plots of the relaxation time vs. the degree of transition are in accordance with the predictions of the linear Ising model, it is concluded that clusters are propagated anisotropically in a linear fashion; e.g., fluidlike P beta conformations grow along the ripple.

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Section: Methodsmentioning

confidence: 99%

Kinetics of the subtransition of asymmetrically substituted phosphatidylcholines

Tümmler¹,

Herrmann²,

Maaß³

et al. 1984

Biochemistry

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Equilibrium, kinetic and photoaffinity labeling studies of daunomycin binding to P‐glycoprotein‐containing membranes of multidrug‐resistant Chinese hamster ovary cells

Busche

Tümmler

Cano‐Gauci

et al. 1989

European Journal of Biochemistry

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The binding of daunomycin and its Bolton-Hunter derivative iodomycin to plasma membranes isolated from mukidrug-resistant Chinese hamster ovary cells (CHO B30) and their drug-sensitive parents (Bl) was investigated. The thermodynamics and kinetics of equilibrium binding monitored by fluorescence titrations and temperaturejump relaxation spectrometry were compared with the specificity of covalent photolabeling with [3H]daunomycin and [1251]iodomycin. The facts that the uptake of anthracycline from aqueous solution into the CHO membranes was not accompanied by any substantial increase of fluorescence anisotropy nor by any spectral shift of the fluorescence emission spectrum and that the partition ratio into the membrane was 20-30-fold higher when compared to a lecithin bilayer, provided evidence that the non-covalent drug binding sites are constituted by polar protein domains without any substantial contribution from the surrounding lipids. Photoaffinity labeling with nanomolar concentrations of anthracycline and equilibrium binding curves independently showed that a 1 SO -170-kDa plasma membrane glycoprotein (P-glycoprotein), whose overexpression is the major difference between B1 and B30 membranes, provides the binding sites of highest affinity for daunomycin and iodomycin ( K z 4 x lo7 M-'). Comparison of photolabeling and equilibrium data suggested that the same binding sites on P-glycoprotein were most probably being monitored. The photolabeling of P-glycoprotein by iodomycin was inhibited in a dosedependent manner by other compounds to which multidrug-resistant cells are either resistant or collaterally sensitive with the following orders of effectiveness : vinblastine > verapamil > nitrendipine > daunomycin $ colchicine. Temperature-jump experiments covering the time range of 1 ps to 1 s revealed a single concentrationdependent relaxation time of 10-30 ps. The association of daunomycin with its binding sites in the membranes was found to be a diffusion-controlled process with k,, rates of 2-4 x lo9 M -l s-' . Therefore, the selectivity of drug binding was entirely reflected in the dissociation rates.Multidrug resistance in mammalian cell lines is a complex phenotype of cross-resistance to a wide range of amphiphilic compounds which have no obvious structural or functional similarities [l -51. Mutant lines of Chinese hamster ovary cells (CHO), selected by exposure to a single cytotoxic agent like daunomycin or colchicine, acquired cross-resistance to Vinca alkaloids, anthracyclines, macrolides, taxol and puromycin and became collaterally sensitive to steroids, local anesthetics and certain calcium-channel blockers [6]. The multidrug-resistance phenotype results from a decreased intracellular accumulation of drug which probably involves a complex set of processes including drug uptake, drug efflux, drug metabolism, and binding to intracellular sites [4, 7 - and human cells, P-glycoprotein (mdr) genes comprise a small multigene family [l 5 , 17 -221. Transfection of a full-length cDNA for a single mouse mdr or...

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DIADEM — A system for the interactive data acquisition and processing in an analytical laboratory

Cited by 2 publications

References 11 publications

Kinetics of the subtransition of asymmetrically substituted phosphatidylcholines

Kinetics of the subtransition of asymmetrically substituted phosphatidylcholines

Equilibrium, kinetic and photoaffinity labeling studies of daunomycin binding to P‐glycoprotein‐containing membranes of multidrug‐resistant Chinese hamster ovary cells

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