Topological distribution of atropine in dipalmitoylphosphatidylcholine liposomes.

The topography of atropine entrapped in sn-3-(dipalmitoyl)phosphatidylcholine (DPPC) liposomes was determined by the electron spin resonance (ESR) technique using 5-, 7-, and 16-nitroxy-stearic acid probes. The liposome preparations, with or without entrapped atropine, were passed through a Sepharose-4B column; the entrapment efficiency and lipid recovery were determined using [3H]-atropine and [14C]-DPPC as tracers. It was found that approximately 31 per cent of the added atropine was entrapped in the liposomes. The ESR results established that the temperature range of the gel-to-liquid crystalline transition of DPPC liposomes was not altered significantly by the encapsulation of atropine. The entrapped atropine also caused no significant change in the order of hydrocarbon chains of DPPC vesicles. These results were confirmed by data obtained from differential scanning calorimetry. On the basis of these experiments, it was concluded that atropine does not interact with the hydrophobic region of the lipid bilayers but is exclusively localized within the entrapped aqueous compartment of DPPC liposomes.

Synthesis and study of spin-labeled nitrosoureas.

For the first time we have synthesized spin-labeled nitrosoureas and have studied their properties--reduction of the iminoxyl group by vitamin C leading to the formation of the corresponding hydroxylamine derivatives and degradation in the presence of an aminoradical, leading to biradicals. The ESR spectra of biradicals in methanol have nine hyperfine resonance lines. The spin-labeled nitrosoureas have shown a high antitumor activity against the L 1210 lymphoid leukemia and P 388 lymphocytic leukemia in BDF1 mice. A study of a broad range of transplantable tumors is in progress.

[Effect of temperature on the photo-induced pH gradient in isolated chloroplasts]. / Vliianie temperatury na fotoindutsirovannyi gradient pH v izolirovannykh khloroplastakh.

Experimental data are presented on the change of photoinduced proton transport and velocity of electron transport (according to photoreduction of K3Fe(CN)6) in chloroplasts during heating within the temperature range 25-50 degrees C for 3 and 5 min. Preliminary heating of chloroplasts irreverssibly supresses the ability of chloroplasts membrane to bind the protons. The velocity of electron transport decreases with the increase of heating temperature, the value of photoinduced change of pH also decreases. Heating is suggested to affect the electron transport chain. The velocity of electron transport decreases and induces the inhibition of proton transport. Presence of detergents, such as digitonin and triton X-100 in chloroplast suspension in concentrations not higher then 0.02% supresses the process of photoinduced change of pH.