A computer method for the acquisition and analysis of patch-clamp single-channel currents.

The method we present instructs the computer to deliver sets of programmed membrane voltages and allows the acquisition of large amounts of digitized data, compact storage, ready identification of records and rapid, interactive analysis of channel current data. A typical cycle of analysis including amplitude determination and kinetic measurements for 10 s of continuous data digitized at 5 kHz requires 5-20 min depending on the complexity of the observed channel activity. This procedure is compatible with such storage protocols as that described by Bezanilla [Biophys.

Competition for binding to multiple sites of human serum albumin for cholecystographic agents and sulfobromophthalein.

The binding of two cholecystographic agents, iophenoxate and iopanoate, to human serum albumin was studied with 11 putative competitors; the results were qualitatively consistent with competitive binding to common sites. A more precise analysis of competition was achieved with four pairs of compounds for which the free and bound concentration of each was determined. The results were analyzed by a computer program and the dissociation constants calculated for both binder and competitor at specified sites on albumin.

Binding of iophenoxate and iopanoate to human serum albumin.

Determination of the binding affinities of 125I-labeled cholecystographic agents to human serum albumin by ultrafiltration techniques is complicated by the appearance of radiochemical impurities resulting from radiolysis of the parent compound. With labeled compounds purified daily by two extractions through chloroform, iophenoxic acid has an extremely high binding affinity. The dissociation constant (K) is 0.

Studies of impedance in cardiac tissue using sucrose gap and computer techniques. II. Circuit simulation of passive electrical properties and cell-to-cell transmission.

The impedance measured in a strip of heart tissue from the moth Hyalophora cecropia is fitted by circuit models of several configurations. The circuits include: (a) a single R-C circuit (b) a double R-C circuit (c) terminated transmission lines, and (d) a pattern of cells with cell-to-cell transmission paths. The last of these is found to give the best fit.

Studies of impedance in cardiac tissue using sucrose gap and computer techniques. I. The influence of sucrose and oil as insulating media.

Impedances of cardiac cells of an insect were determined as a function of time to test the effects of sucrose and oil as insulating media in a gap arrangement. Impedance values are shown to increase markedly with time when sucrose is used as the insulating agent. Although impedance values are steady when oil is used, it is suggested that a layer of trapped electrolyte provides a shunt pathway and seriously impairs the validity of the measurements.