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We study the electrical conductivity problem of DNA, applying the Holstein's polaron model to a double strand of DNA. We show that the Holstein's polarons act as donors and acceptors in DNA and that the existence of such donors and acceptors provides us the extrinsic semiconductor character of DNA. This character of DNA may explain with a unified point of… (More)
A new bisabolane-type sesquiterpenoid, (E)-3-isocyanobisabolane-7,10-diene (1), and a new epidioxyergostane-type steroid, 9(11)-dehydroaxinysterol (2), were isolated from the Okinawan sponge of the genus Axinyssa. Their structures were elucidated based on the results of spectroscopic analysis and chemical conversion. Epidioxysterol 2 was found to show… (More)
Six new marine steroids, yonarasterols A through F, were isolated from the Okinawan soft coral, Clavularia viridis. Their structures were determined based on the results of spectroscopic analysis.
We revisit the problem of the electronic properties of a single strand of DNA, formulating the Hückel approximation for π-electrons in both the sugar-phosphate backbone chain and the π-stacking of nitrogenous bases in a single strand of DNA where the nitrogenous bases are adenine (A), guanine (G), cytosine (C) and thymine (T), respectively. We calculate the… (More)
Three new chlorinated marine steroids, yonarasterols G, H and I, were isolated from the Okinawan soft coral, Clavularia viridis. Their structures including the absolute configuration were determined based on the results of spectroscopic analysis and chemical conversion.
I study the conceptual framework of protein folding considering an exactly solvable model — the Rubik's magic snake model. I discuss the mathematical representation of the model, the model Levinthal paradox, the non-unique compact folded structure, the function of the chain, the ground state energy, the commensurability between the folded structure and the… (More)
A toy model is introduced in order to understand the conceptual framework of the protein folding problem. Denaturation of proteins has been of strong interest for both biological and theoretical physicists for a long time. 1 A denatured protein can fold into a native three-dimensional structure which is coded by the amino acid sequence in the primary… (More)
A new sterol (axinysterol) was isolated from the Okinawan marine sponge of the genus Axinyssa. The structure of axinysterol was assigned as 5 alpha,8 alpha-epidioxyergosta- 6,22,25-trien-3 beta-ol based on spectroscopic analysis and chemical transformation.
Eight new marine steroids were isolated from the Okinawan soft coral Clavularia viridis Quoy and Gaimard. Their structures were determined based on spectroscopic analysis, chemical conversion, and X-ray crystallographic analysis. Steroids 5 and 6 showed growth inhibition activity toward HeLa S3 cells and human diploid cells in vitro.