Competitive studies, single labeling

Fig. 7.4 Time dependence of isotopic ratios in product during single label competitive KIE studies...

Adsorption of albumin, y-globulin, and fibrinogen from single solutions onto several hydrophobic polymers was studied using internal reflection IR spectroscopy. The adsorption isotherms have a Langmuir-type form. The calculated rate and amount of protein adsorbed was dependent on the polymer substrate and the flow rate of the solution. Competitive adsorption experiments were also investigated to determine the specific adsorption of each I-labelled protein from a mixture of proteins. Platelet adhesion to these proteinated surfaces is discussed in relation to a model previously proposed. 

Additional studies utilized spin-labeled analogs of PC, PE, PS, and SM, and the t for the translocation of these lipid analogs from the cytosolic face to the lumenal face of the microsomes was calculated to be 20 min. The transport process did not require ATP and the translocation of each class of lipid showed identical sensitivity to inhibition by N-ethylmaleimide. Furthermore, different species of lipid showed transport kinetics that were consistent with mutual competition for a single transporter. These results indicate that the ER has a relatively non-specific, ATP-independent transporter that is capable of translocating multiple species of lipid across the bilayer. Several attempts have been made to reconstitute the protein components of the ER necessary for ATP-independent transbilayer lipid movement within liposomes (J. Backer, 1987 S. Gummadi, 2002). These approaches have met with only limited success and thus far no specific proteins or genes have been directly implicated in the process. 

It will be noted from Table 13 that single temperature rate coefficients are listed and not Arrhenius parameters. The latter are not readily derived from the original type of experiments, which are not suitable for the measurement of temperature coefficients because of the difficulty of assessing the variations of quantities such as the diffusion coefficient and the limit of detectability of sodium atoms. An interesting competitive method has been developed to study Na and K atom reactions which overcomes these difficulties [146]. The alkali metal atoms were reacted in diffusion flame experiments with pairs of organic halides. By labelling one of the halides with Cl and by analysing for the total concentration and... 

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