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Volume 75, Issue 5
Displaying 1-3 of 3 articles from this issue
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Mayumi HAYASHI, Yumi NEGISHI, Akira HIRAO1999 Volume 75 Issue 5 Pages 93-96
Published: 1999
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSThe synthesis of new heteroarm A2B4, A2B8, A2B12, and ABC4 star-branched polymers with well-defined structures is described. Our method for these star polymer synthesis involves the three reaction steps: The first step is to prepare the polystyrenes with a definite number of methoxymethylphenyl groups as prepolymers. The methoxymethylphenyl groups thus introduced are quantitatively transformed into chloromethylphenyl groups by treating with BCl3 in the second reaction step. In the third step, poly-isoprenyllithium is reacted to link with the chlorinated prepolymers to afford the desired heteroarm star polymers. The resulting heteroarm star polymers were finally isolated in 80-85% by SEC fractionation. Their well-defined and controlled structures were demonstrated by SEC, 1H NMR, and light scattering measurements.View full abstractDownload PDF (626K) -
S. M. Abdul KARIM, Kittichote MUSIKABHUMMA, Ryoji NOMURA, Toshio MASUD ...1999 Volume 75 Issue 5 Pages 97-100
Published: 1999
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSSubstituted polyacetylenes with very wide main-chain conjugation were synthesized by the polymerization of 9-phenanthrylacetylene (9-PhnA) and 1-pyrenylacetylene (1-PyA). The polymerizations of 9-PhnA and 1-PyA with W catalysts resulted in polymers in good yields (67-95%), whereas only low yields were attainable with Mo and Rh catalysts (6-15%). The polymers obtained with W catalysts were deeply colored (dark purple), partly soluble in toluene and chloroform, and completely soluble in o-dichlorobenzene. On the other hand, those with Mo or Rh catalysts were light brown and insoluble, which means that W-based catalysts are able to produce the polymers with wider conjugation and higher solubility than do Mo and Rh catalysts. The absorption maxima and cutoff wavelengths of the polymers produced with W catalysts reached 580 and 800nm, respectively, which is a clear indication of the extremely wide conjugation of the main chain.View full abstractDownload PDF (545K) -
Hideaki KOIKE, Tsuyoshi KAWASHIMA, Masashi SUZUKI1999 Volume 75 Issue 5 Pages 101-106
Published: 1999
Released on J-STAGE: October 17, 2006
JOURNAL FREE ACCESSCentral metabolic pathways of four archaebacterial organisms, Pyrococcus sp. OT3, Methanococcus jannaschii, Archaeoglobus fulgidus, and Methanobacterium thermoautotrophicum, have been analyzed by using their genomic DNA sequences. Close to a full set of enzymes that are expected in the standard TCA cycle have been identified with the DNA sequence of A. fulgidus. However, with the other three sequences, enzymes expected in half the TCA cycle, connecting citrate to α-ketoglutarate through isocitrate, are not found. It is believed that the autotrophic methanogens, M. jannaschii and M. thermoautotrophicum, do not need the reduced form of co-enzymes for the production of ATP. A heterotroph, P. OT3, reduces co-enzymes mainly by degrading amino acids. These three organisms are not totally dependent on the TCA cycle. Another heterotroph, A. fulgidus seems to be dependent on the electron transfer chain and is likely to operate the TCA cycle in the standard clockwise direction for the reduction of co-enzymes, while the autotrophs are likely to operate the cycle in the anti-clockwise direction for biosynthesis only. The glycolytic pathways of the four organisms extend closely to glycogen, are used first for gluconeogensis and then for glycolysis. The glycolysic pathway of P. OT3 is best designed for amphibolic regulation by placing two alternative sets of enzymes at steps. The modified Embden-Meyerhof type is suggested for the pathways for glycolysis/gluconeogenesis of the four organisms.View full abstractDownload PDF (1011K)
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