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This paper compares the DNA interactions of a bis 9‐aminomethylanthracene dye (2) vs. a mono‐anthracene (4) under high ionic strength conditions similar to those in the cell nucleus (∼150 mM NaCl and 260 mM KCl). The chloride salts triggered an enhancement in anthracene‐sensitized DNA photocleavage, where bis‐anthracene 2 exhibited superior DNA binding affinity, faster reaction kinetics, and higher levels of DNA damage at low‐ to sub‐micro molar dye concentrations (350 nm hν, pH 7.0). While spectroscopic and viscometric data suggested that the chloride salts reduced DNA intercalation in favor of a non‐intercalative binding mode in which 2 and 4 were better able to generate hydroxyl radicals, there was evidence of persistent intercalation of the second anthracene ring of 2. We propose that such an interaction anchored the bis‐anthracene to DNA under the high ionic strength conditions, increasing its binding affinity and photocleaving capabilities relative to the mono analog (4).

A large number of microorganisms including various microalgal strains are able to convert steroid compounds into useful metabolites. In the present study, the ability of Microchaete tenera, a rice paddy field-isolated microalga, was investigated for biotransformation of progesterone. The incubation was carried out at 25°C under continuous illumination in the present of 0.25 gL −1 of progesterone. After 5 days incubation of the microalga in BG-11 liquid medium, the broth was extracted and the products were purified by the aid of chromatographic methods. Structure elucidation of the metabolites was performed by spectral data ( 13 C NMR, 1 H NMR, FTIR, and MS) and physical constants (melting points and optical rotations). Eventually, four major steroids including 20β-hydroxypregn-4-en-3-one, 20α-hydroxypregn-4-en-3-one, 6β-hydroxypregn-4-en-3,20-dione and 6α-hydroxypregn-4-en-3,20-dione were the results of this biotransformation. The study also showed that the best concentration of starting material, temperature, photoregime, and the influence of CO 2 partial pressure on the production of bioconverted metabolites were 0.25 gL −1 , 25°C, continuous light and 2.0±0.1% (v/v), respectively. Highest concentrations of all biotransformed metabolites were obtained in the 5th day.