The labour pains of biochemical selenology: the history of selenoprotein biosynthesis.

The serendipitous discoveries leading to the present knowledge on selenium's role in biology are reviewed. Detected in 1818 as by-product of sulphuric acid production, selenium first attracted medical attention as an industrial hazard. In parallel selenium intoxication was recognized as cause of life stock diseases. Reports on teratogenic effects and carcinogenicity of selenium followed since the middle of the past century. In 1954 first hints towards specific biological functions of selenium were contributed from microbiology, and its essentiality for mammalian life was discovered in 1957. Independent and unrelated studies led to the identification of selenium as an integral constituent of one mammalian and two bacterial enzymes in the early 70ies followed by the identification of selenocysteine in these proteins. In the 80ies, independent sequencing of selenoproteins and cloned DNAs revealed that the selenocysteine of selenoproteins is encoded by the termination codon TGA (UGA). Recoding of TGA as selenocysteine codon by secondary mRNA structures was first elucidated by molecular genetics in bacteria and later in mammals. During the 90ies, finally, the basic principles of selenoprotein synthesis were worked out by molecular biology tools. The article closes with spotlight comments on proven and potential biomedical benefits of selenium and related research deficits.

Hunting for electrophiles that harm human DNA: Frits Sobels Award Lecture.

This lecture is dedicated to Frits Sobels and his farsighted vision on research directions in genetic toxicology. Some accomplishments by the author's research group in the area of cancer etiology research and pre-clinical drug safety evaluation are presented. Praziquantel, an antischistosomal drug, was found to be devoid of any genetic effects which determined the drug companies to proceed with further safety evaluation and marketing. This highly efficient life-saving drug is now in use world wide. Biomonitoring methods have been developed to quantitate carcinogens, their metabolites or DNA adducts in humans exposed environmentally and endogenously to genotoxic agents. The methods were applied in ecological and case-control studies aimed at establishing causal relationships between exposure and disease. Results from both field studies in Iran and laboratory investigations supported the hypothesis that opium use, in particular ingestion of its pyrolysates, may be a risk factor for esophageal cancer in this region, probably acting together with nutritional deficiencies and thermal injury. By applying the nitrosoproline (NPRO) test in ecological studies on esophageal cancer causation in China some support was obtained for the involvement of N-nitroso compounds. In inhabitants of high risk areas endogenous nitrosamine synthesis could be markedly reduced by ingestion of vitamin C. Ultrasensitive detection methods for etheno-DNA adducts, which are formed by lipid peroxidation products resulting from increased oxidative stress, have been developed. Known cancer risk factors such as metal storage, chronic inflammatory processes and a high omega-6 PUFA fat diet increased the background level of these miscoding DNA adducts many times. They were found to increase progressively in premalignant lesions of cancer-prone tissues of humans and rodents, probably contributing to the genetic instability that drives cells to malignancy. Etheno-DNA adducts are thus promising markers to verify the efficiency of chemopreventive measures in humans.

The potential of LC-NMR in phytochemical analysis.

The coupling of high performance liquid chromatography with nuclear magnetic resonance spectroscopy (LC-NMR) is one of the most powerful methods for the separation and structural elucidation of unknown compounds in mixtures. The recent progress in pulse field gradients and solvent suppression, the improvement in probe technology, and the construction of high field magnets have given a new stimulus to this technique, which has emerged since the mid 1990s as a very efficient method for the on-line identification of organic molecules. LC-NMR thus represents a potentially interesting complementary technique to LC-UV-MS in phytochemical analysis for the detailed on-line structural analysis of natural products. Recent applications have fully demonstrated the usefulness of this technique. A brief review of the applications of LC-NMR in natural product chemistry is presented in this paper, and a summary of the basic principles and modes of operation of LC-NMR is provided. Selected examples of LC-NMR analyses of plant metabolites in crude extracts or in enriched fractions are outlined and used to illustrate the different strategies for employing the technique. The practical possibilities and limitations of LC-NMR in its application to the analysis of crude plant extracts are discussed by means of several examples. Analytical strategies involving LC multi-coupled (hyphenated) techniques for the chemical screening and dereplication of crude plant extracts are presented. An analysis of the future development of the technique with respect to its application in phytochemical analysis is also given.