The interaction of multiply charged intercalating heterocycles with DNA

The interaction with DNA of two aromatic nitrogen heterocycles, 1 and 2 , which at pH 6 have two positive charges on their ring systems and two cationic side chains, have been determined. A third similar compound, 3 , with a single side chain and reduced ring charge, was analyzed as a control. Viscometric titrations with sonicated DNA indicated that all three compounds bind to DNA by intercalation. Spectrophotometric binding studies as a function of ionic strength indicated that both 1 and 2 bind to DNA as tetracations at pH 6. These are the first examples of intercalators with two charges directly on the intercalating ring system. Dissociation kinetics experiments as a function of ionic strength confirmed that 1 and 2 bind to DNA as tetracations. Compound 1 has a G · C base-pair binding preference, 2 seems to prefer binding to alternating pyrimidine–purine sequences regardless of the composition, and 3 has no significant binding specificity.     

The fruits available as food to small rodents in two woodland ecosystems

The fruit fall from the canopy and the understorey in an oak Quercus petraea (Mattushka) Liebl. wood and in a yew Taxus baccata L. wood at Killarney, Ireland, were measured over a period of approximately 13 months; this included two complete fruit crops in each wood. Fruit represents the great bulk of the food of the small rodents present: wood mice Apodemus sylvaticus (L.) and bank voles Clethrionomys glareolus Schreber. From a knowledge of the particular fruits or their parts eaten, the amounts of available food, in kcal ha^-1 were derived. In each ecosystem the food potentially available to small rodents in one crop was five times that in the other.