Biosynthetic study of amphidinolide B

The biosynthetic origins of amphidinoide B (1) were investigated on the basis of 13C-NMR data of 13C-enriched samples obtained by feeding experiments with [1-(13)C], [2-(13)C], and [1,2-(13)C2] sodium acetates in cultures of a dinoflagellate Amphidinium sp. These incorporation patterns suggested that 1 was generated from three successive polyketide chains, an isolated C1 unit from C-2 of acetates, six branched C1 units from C-2 of acetates, and an "m-m" and an "m-m-m" unit derived only from C-2 of acetates. The labeling patterns of amphidinolide B (1) were different from those of amphidinolide H (2), a 26-membered macrolide closely related to 1.     

Determination of salicylate in blood serum using an amperometric biosensor based on salicylate hydroxylase immobilized in a polypyrrole-glutaraldehyde matrix

The use of an amperometric biosensor for the salicylate determination in blood serum is described. The biosensor is based on salicylate hydroxylase (EC 1.14.13.1) electropolymerized onto a glassy carbon-working electrode with polypyrrole and glutaraldehyde, to improve the biosensor lifetime. The hexacyanoferrate (II) was also incorporated to work as a redox mediator to minimize possible interferences. The salicylate is enzymatically converted to catechol, which is monitored amperometrically by its electrooxidation at+0.170 V versus SCE (saturated calomel electrode). Salicylate determination was carried out maintaining the ratio between beta-NADH and salicylate at 4:1 (30 degrees C). The amperometric response of the biosensor was linearly proportional to the salicylate concentration between 2.3x10(-6) and 1.4x10(-5) mol l(-1), in 0.1 mol l(-1) phosphate buffer (pH 7.8), containing 0.1 mol l(-1) KCl and 5.0x10(-4) mol l(-1) Na(2)H(2)EDTA, as supporting electrolyte. The recovery studies, in the presence of several interfering compounds, showed recoveries between 96.4 and 104.8%. The useful lifetime of the biosensor in the concentration range evaluated was at least 40 days, in continuous use. Blood serum samples analyzed by this biosensor showed a good correlation compared to the spectrophotometric method (Trinder) used as reference, presenting relative deviations lower than 7.0%.     

Wild ginseng grows in Myanmar

Ginseng, the underground parts of plants of Panax species, has been used in oriental traditional medicine for centuries. Unfortunately, because of extensive exploitation over thousands of years, the natural source of these species has been almost exhausted. Recently, we have found a wild ginseng growing in Myanmar. Here, by a combination of chemical composition study and gene sequence analysis, we unambiguously demonstrate that the wild ginseng is actually P. zingiberensis, commonly known as ginger ginseng. This ginseng was an indigenous to the southwestern China. However, now it is seriously threatened to brink of extinction and is put on the highest level of protection in China. Therefore, an appropriate protection measure is highly recommended to preserve this valuable resource, since this Myanmar ginseng might turn out to be the last P. zingiberensis, which could ever be seen in the planet.     

Crystal structure of poly(p-benzamide)

Redetermination of the crystal structure of poly(p-benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the N? C bond of the amide group and about the virtual bond of N-phenyl-C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P2₁2₁2₁-D. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc.     

Effects of solvent in photo-induced graft copolymerization of vinyl monomers on cellulose

The effects of swelling of the sample and polymerization solvents were studied for photo-induced graft copolymerization of vinyl monomers on cellulose. The graft copolymerization of methyl methacrylate (MMA) was activated by swelling of the sample or organic solvent-water solutions within a certain range of their concentrations. Though each organic solvent gave a maximum in per cent grafting and the number of grafts at about 25 vol-% concentration, the initiation reaction scarcely took place at 100% concentration; thus, the solvent itself is considered to have a negative effect. The solvents used in the experiments were all hydrophilic, such as methanol, acetone, and dioxane. The average molecular weight of the grafted PMMA differed in each solvent, indicating a different characteristic effect of solvent on the growing grafted polymer radicals. The presence of ferric ion as a sensitizer stimulated further the contributions of the sample swelling and the organic solvents to the copolymerization reaction. A similar effect was observed for styrene as for MMA, but not for acrylic acid and methacrylic acid.     

Aromatic polyesters obtained directly from hydroxybenzoic acids by hexachlorocyclotriphosphatriazene (PNC) in pyridine

Polyaryl esters of moderate molecular weights were prepared by the direct polycondensation reaction of hydroxybenzoic acids and its derivatives with hexachlorocyclotriphosphatriazene (also known as phosphonitrilic chloride trimer, PNC) as a condensing agent in pyridine. Copolymerization of p-hydroxybenzoic acid with several hydroxybenzic acid derivatives was carried out to improve the processability of the polymer of p-hydroxybenzoic acid, which yields fusible and soluble copolymers of high inherent viscosities. Polymer solubility and thermal behavior were examined.