The transport activity of purified Na+K+‐ATPase was investigated by measuring the electrical pump current induced on black lipid membranes. Discs containing purified Na+K+‐ATPase from pig kidney were attached to planar lipid bilayers in a sandwich‐like structure. After the addition of only microM concentrations of an inactive photolabile ATP derivative [P3‐1‐(2‐nitro)phenylethyladenosine 5′‐triphosphate, caged ATP] ATP was released after illumination with u.v.‐light, which led to a transient current in the system. The transient photoresponse indicates that the discs and the underlying membrane are capacitatively coupled. Stationary pump currents were obtained after the addition of the H+, Na+ exchanging agent monensin together with valinomycin to the membrane system, which increased the permeability of the black lipid membrane for the pumped ions. In the absence of ADP and Pi the half saturation for the maximal photoeffect was obtained at 6.5 microM released ATP. The addition of ADP decreased the pump activity. Pump activity was obtained only in the presence of Mg2+ together with Na+ and Na+ and K+. No pump current was obtained in the presence of Mg2+ together with K+. The electrical response was blocked completely by the Na+K+‐ATPase‐specific inhibitors vanadate and ouabain. No pump currents were observed with a chemically modified protein, which was labelled on the ATP binding site with fluoresceine isothiocyanate. The method described offers the possibility of investigating by direct electrical measurements ion transport of Na+K+‐ATPase with a large variety of different parameters.

The synthesis of hyperbranched-linear-hyperbranched ABA triblock copolymers based on a linear poly(oxymethylene) (POM) block and hyperbranched poly-(glycerol) (hbPG) blocks is described. The polymers containing a polyacetal polyether structure were prepared from linear bishydroxy-functional POM macroinitiators, obtained by cationic ring-opening polymerization of trioxane and 1,3-dioxolane as a comonomer with formic acid as a transfer agent and subsequent hydrolysis of the formate group. Partial deprotonation of the resulting hydroxyl groups permitted "hypergrafting" of glycidol by anionic ring-opening multibranching polymerization (ROMBP). With respect to the hyperbranched blocks, the obtained polymers show the expected, moderate molecular weight distributions in the range of 1.31 to 2.01 and molecular weights between 6100 and 22900 g mol −1 . Both the degree of polymerization of the linear POM segments as well as the molecular weight of the hbPG blocks have been varied. Key properties, such as thermal behavior and thermal stability, degree of crystallization and surface properties were investigated, showing an adjustable degree of crystallization and enhanced hydrophilicity depending on the hbPG content.

Photosensitive Monoschichten und Liposomen können aus amphiphilen Pyridinioamidaten wie 1 hergestellt werden (die „Doppelkette”︁ symbolisiert den Rest N(CH2CH2OCOC15H31)2). Oberflächeneigenschaften und Stabilität lassen sich durch UV‐Bestrahlung stark verändern; beispielsweise gehen stabile Liposomen aus 1 dabei in metastabile Liposomen aus 1,2‐Diazepinen 2 über.magnified image

Photosensitive monolayers and liposomes can be prepared from amphiphilic pyridinioamidates such as 1 (the “double chain” symbolizes the N(CH2CH2OCOC15H31)2 residue). Their surface properties and stability can be significantly modified by UV radiation. For example, stable liposomes formed from 1 are thereby converted into metastable liposomes consisting of 1,2‐diazepines 2.

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