Structure of Cu2(indomethacin)4 and the reaction with superoxide in aprotic systems

The copper complex of indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate), a common anti-inflammatory drug, was prepared and characterized. Crystal structure determination revealed the dimeric form of the 1:2 complex, namely Cu₂(indomethacin)₄ · L₂, in the unit cell. Suprisingly, the copper-copper distance (263 pm) was very close to metallic copper (256 pm). The two coordination sites in the copper-copper axis can be readily replaced by superoxide. An intriguing similarity to Cu₂(acetate)₄ was seen.Due to the lipophilic nature of the indomethacin ligand, this copper complex reacted with superoxide in aprotic solvents. The superoxide dismutating activity was successfully demonstrated in Me₂SO/water and acetonitrile/water mixtures using the nitro-blue tetrazolium assay and pulse radiolysis. The second-order rate constant of 6 · 10⁹ M^?1 · s^?1 in strictly aqueous systems dropped only slightly to 1.1 · 10⁹ M^?1 · s^?1 when aprotic solvents were used. This is the fastest rate constant ever observed for a copper-dependent dismutation of superoxide. The KO₂-induced lipid peroxidation in both erythrocytes and liver microsomes was suppressed by 70% in the presence of 1 · 10^?10 mol · ml^?1 of Cu₂(indomethacin)₄. The inhibitory action dropped to 25% when Cu₂Zn₂superoxide dismutase was employed. The formation of copper · indomethacin in rat serum after administration of indomethacin was shown in vitro and in vivo.     

Biological rhythms in birds — development, insights and perspectives

The aim of this review is to show that probably the internal clock of precocial birds is imprinted in the prenatal period by exogenous factors (zeitgeber). The activity of organ functions occurs early during embryonic development, before this function is ultimately necessary to ensure the survival of the embryo. Prenatal activation of some functional systems may have a training effect on the postnatal efficiency.The development of physiological control systems is influenced by endogenous and exogenous factors during the late prenatal and early postnatal period: epigenetic adaptation processes play an important role in the development of animals; they have acquired characteristics which are innated but not genetically fixed. As a rule, the actual value during the determination period has a very strong influence on the set-point of the system. This will be explained using the example of thermoregulation.It is shown in detail that it seems to be possible to imprint the prenatal development of circadian rhythms by periodic changes of the light-dark cycle but not by rhythmic influence of acoustic signals.Altogether, there are more questions open than solved concerning the perinatal genesis of circadian rhythms in birds. Topics are given for the future research.     

Correction for the inherent error in optical density readings.

Except at very low levels, uncorrected photometric determination of bacterial cell densities showed a decreasing proportionally to actual cell density or dry weight. A standard curve was prepared to convert photometric readings to truly proportional optical density values. With one dry weight determination, optical density values may be converted to absolute dry weight values.     

Two Agrobacterium tumefaciens genes for cytokinin biosynthesis: Ti plasmid-coded isopentenyltransferases adapted for function in prokaryotic or eukaryotic cells

Summary Tzs and ipt are two Ti plasmid genes coding for proteins with isopentenyltransferase (IPT) activity in vitro. We cloned both genes for protein expression in Escherichia coli and in Agrobacterium tumefaciens, and we investigated differences between the two genes by analysing the properties of the proteins in vitro and in vivo. In vitro, extracts with tzs or ipt-coded proteins had high IPT activity, and the enzymes were identical in most properties. The most important difference was detected in vivo: the tzs-encoded protein was very active in cytokinin production, while the ipt protein required overexpression in order to obtain measurable activity in bacteria. In both cases, rans-zeatin was the major product of the gene activity. Formation of this cytokinin requires a hydroxylase function in addition to the IPT reaction. No such activity could be ascribed to tzs or ipt-encoded proteins in vitro or in vivo, but cytokinin hydroxylase activity was detected in cells and extracts of E. coli, regardless of the presence or absence of the cytokinin genes. Based on these results it is proposed that both genes code for a single enzyme activity (isopentenyltransferase), that the genes and proteins are adapted for function either in bacteria (tzs) or in transformed plant cells (ipt), and that in both prokaryotic and eukaryotic cells hydroxylation to trans-zeatin is a function contributed by host enzymes.Abbreviations DMAPP dimethylallylpyrophosphate - iP isopentenyladenine - iPA isopentenyladenosine - iPMP isopentenyladenosine 5-monophosphate - IPT isopentenyltransferase - trans-Z trans-zeatin