HYPERICIN PHOTOSENSITIZATION IN AQUEOUS MODEL SYSTEMS

Abstract Photosensitization of lysozyme, liposomes, ghosts and intact red blood cells (RBC) was investigated for aqueous hypericin. The effects of azide ion, 1,4-diazabicyclo(2.2.2)octane, and superoxide dismutase on photosensitized inactivation of lysozyme in 0.5% Triton X-100 indicate that singlet oxygen is the major inactivating intermediate with a contribution from superoxide. The singlet oxygen quantum yield (Φ_Δ) scaled to methylene blue is 0.49 ± 0.06 at monochromatic wavelengths from 514 to 600 nm. Relative values of Φ_Δ based on lysozyme inactivation for different vehicles are: 0.5% Triton X-100 (1.13), human serum albumin (0.65), Cremophor-EL(0.76), Cremophor-RH40 (0.98), egg phosphatidylcholine (EPC) liposomes (0.04), hydrogenated soy phosphatidylcholine (HSPC) liposomes (<0.01). Hypericin photosensitized lipid peroxidation of EPC liposomes and RBC ghosts. Extensive cross-linking of ghost membrane proteins occurred during the initial stages of lipid peroxidation. Prompt photohemolysis was used as the assay of RBC membrane damage. The photohemolysis curves are modeled with multihit target theory based on the "hit number" (n) and the target cross section (v). The values of v and the conventional "1/t₅₀" parameter are equivalent determinants of the photohemolysis rate. The photohemolysis curves are in good agreement with n = 15 for incubation in phosphate-buffered saline at different hypericin concentrations and with additives. The measurements for other vehicles led to n = 19 for Cremophor-EL and n = 3 for EPC and HSPC liposomes, indicating that the kinetics of photohemolysis depend on the conditions of incubation.     

1,2,5-thiadiazole-1-oxides,IV, ring transformation to 1,2,3,5-thiatriazole- and 1,2,4,6-thiatriazene-1-oxide

2-Alkyl-1,2,5-thiadiazole-3-one-1-oxides were converted to 1,2,3,5-thiatriazole-1-oxides and 1,2,4,6-thiatriazene-1-oxides. The postulated intermediate of these rearrangements, a sulfinylamine, was isolated.     

Atmospheric absorption near 2400 cm-1

Theoretical atmospheric absorption spectra between 2385 and 2425 cm^-1 are shown to give excellent agreement with high resolution observations. Most of the atmospheric absorption in this region arises from continuum features due to absorption of N₂ and the wings of distant CO₂ lines. The treatment of each of these factors is discussed.     

Mannich base derivatives of bioactive benzyl-1,3-benzodioxo-5-ols

3,4-Methylenedioxyphenol (sesamol) reacts with equimolecular quantities of an aromatic aldehyde and morpholine or piperidine in methanol to give Mannich bases 7 and 8 , related to insect growth regulators and anti-leukemic and antimitotic benzyl-1,3-benzodioxole derivatives.     

Canonical quantization of 1+1 dimensional gravity

Based on Polyakov's evaluation of the Fadeev-Popov determinant for (1+1)-dimensional gravity in the conformal gauge we formulate a canonical quantization in the synchronous gauge. We find that the system is describable as a quantum mechanical system of one degree of freedom. The quantization can be carried out and solved when any number of gauge fields are included. Scalar and spinor fields lead to new difficulties. For positive cosmological constant the geometry collapses as suggested by the classical system. For negative cosmological constant a more interesting behavior involving exponentially expanding and contracting universes occurs.Supported in part by NSF Grant No. PHy 78-26847.On leave from Tel Aviv University. Supported in part by the Israel Commission for Basic Research.