A number of antimicrobial peptides have been isolated in the animal kingdom, serving as defensive or offensive weapons. The mechanisms of their action are considered to be the permeability of bacterial membranes, although the details are not yet clarified. I have studied the interactions of several antibiotic peptides with both artificial lipid bilayers and biomembranes to elucidate the molecular mechanisms of the action and to find out the rationale for their membrane specificity. Magainin 2 from the Xenopus skin was found to form a peptide-lipid supramolecular complex pore in the membrane, followed by peptide internalization, simultaneously dissipating the transmembrane potential and the lipid asymmetry. This novel mechanism also works for a wasp bee venom, mastoparan X. Tachyplesin I from Tachypleus and a bee venom, melittin, also translocate across the membrane by forming a pore. The membrane selectivity of these peptides is closely related to their affinity for the lipids constituting the membrane surface. A strategy for developing a potent antibiotic was discussed based on these results.
Capillary electrophoretic systems equipped with a multi-color detectable laser-induced fluorescent DNA detector (CE-LIF) were developed. We examined the efficiency and the performance of the CE-LIF systems for the high-speed DNA sequencing and DNA diagnosis for human diseases. The effect of the gel composition, electric field strength, and capillary length on the separation of DNA sequencing reaction product was investigated in order to achieve high-speed DNA sequencing for large-scale sequencing in the Human Genome Project. The CE-LIF system is successfully applied to ultrafast cDNA sequencing for human and yeast genomes. Under optimum separation conditions, only 10 min is required to sequence 300 base DNA. A polymer solution of cellulose derivative was utilized as a sieving medium for the CE-LIF system and gave excellent resolution of polymerase chain reaction (PCR) amplified polymorphic loci on the human genome. The CE-LIF system is successfully applied to the DNA diagnosis for cancers through CA repeat analysis of human D8S 1218 locus, heart diseases through VNTR (variable number of tandem repeat) analysis of human apolipoprotein B gene and Alzheimer's disease through RFLP (restriction fragment length polymorphism) analysis of human apolipoprotein E gene with high-speed and high resolution. Capillary affinity gel electrophoresis was developed as a new technique for the recognition of the specific DNA base and/or sequence. This technology is also applicable to the characterization of binding properties of DNA based drugs. The principle, the theory, and the methods of capillary affinity gel electrophoresis are presented. This technique is applied to the determination of association constants between an affinity ligand and oligonucleotides. The great potential of capillary affinity gel electrophoresis for the detection of the mutation on DNA is illustrated.
The Pummerer rearrangement of sulfoxides with acid anhydrides is a useful method for the synthesis of α-substituted sulfides and has attracted considerable attention from both synthetic and mechanistic points of view. In recent years, we have developed two novel and significant Pummerer-type reactions ; i) an asymmetric Pummerer-type reaction of chiral, non-racemic sulfoxides with a highly enantiomeric excess, and ii) the first successful Pummerer-type reaction of the aromatic ring. In this review, we describe 1) the asymmetric Pummerer-type rearrangement induced by an O-silylated ketene acetal, 2) the asymmetric Pummerer-type rearrangement induced by an ethoxy vinyl acetate, 3) the additive-Pummerer-type reaction, 4) the asymmetric Pummerer-type cyclization induced by an O-silylated ketene acetal, and 5) the aromatic Pummerer-type reaction of p-sulfinyl phenol derivatives leading to peri-hydroxy dihydroquinone derivatives.
In order to find dual antagonists against both thromboxane A2 (TXA2) and leukotriene D4 (LTD4) receptors for a new antiasthmatic agent, various benzenesulfonamide derivatives were synthesized and evaluated for those pharmacological effects. TXA2 and LTD4 antagonistic activities in vitro were evaluated by the inhibitory effects on LTD4-induced and U-46619-induced contraction of guinea-pig trachea. Furthermore, TXA2 and LTD4 antagonistic activities in vivo were evaluated by the inhibitory effects on LTD4-induced and U-46619-induced bronchoconstriction of guinea-pig after oral administration of test compounds. It was found that 4-[5-[1-(4-chlorobenzenesulfonamido)-5-methylhexyl]-2-thienyl] butyric acid (12i) and 4-[5-[1-(4-fluorobenzenesulfonamido)-5-methylhexyl]-2-thienyl] butyric acid (12j) possess good anti-LTD4 and anti-TXA2 activities by oral administration.