Rapid oligosaccharide synthesis using a fluorous protective group

The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS.     

Application of 28Mg to the kinetic study of Mg uptake by rice plants

The time course of Mg uptake and release using intact rice plants and ²⁸Mg as a tracer is presented. Since there is no conventional Mg tracer available, ²⁸Mg was produced via ²⁷Al(α, 3p)²⁸Mg reaction using a cyclotron. Using the purified ²⁸Mg tracer, it was found that the uptake amount of ²⁸Mg by the rice plants increased linearly during 30 min of application. After ²⁸Mg treatment for 90 min, the roots were sequentially washed with iced solution for 120 min. Within about 10 min, almost all of the ²⁸Mg, that was thought to be weakly bound to the apoplast, was washed away.     

Synthesis of glycosaminoglycans via enzymatic polymerization

Hyaluronic acid and chondroitin were successfully synthesized as representative molecules of glucosaminoglycans and galactosaminoglycans found in a glycosaminoglycan family via enzymatic polymerization catalyzed by testicular hyaluronidases. A newly designed N-acetylhyalobiuronate oxazoline derivative with a β-D -glucuronyl-(1→3)-N-acetyl-D -glucosamine disaccharide structure served as a transition-state analogue substrate monomer for the enzyme, giving rise to artificial hyaluronic acid in 52% yields with a number-average molecular weight of 1.35 × 10⁴ through ring-opening polyaddition in a perfect regioselective and stereoselective manner. A novel N-acetylchondrosine oxazoline derivative with a β-D -glucuronyl-(1→3)-N-acetyl-D -galactosamine disaccharide structure also acted as a transition-state analogue substrate monomer for the enzyme, yielding artificial chondroitin in 35% yields with a number-average molecular weight of 2.5 × 10³. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3541–3548, 2003     

Synthesis of fluorinated chitin derivatives via enzymatic polymerization

Synthesis of fluorinated chitin derivatives has been achieved using chitinase from Bacillus sp. as a catalyst. 6'-Fluoro- (1a), 6-fluoro- (1b) and 6,6'-difluoro- (1c) chitobiose oxazoline derivatives were newly prepared as TSAS monomers for chitinase. Ring-opening polyaddition of these monomers proceeded effectively at pH 8.0-9.0 and 30-40 degrees C, giving rise to alternatingly 6-fluorinated chitin derivatives (2a and 2b) from 1a and 1b, and fully 6-fluorinated chitin derivative (2c) from 1c under total control of regioselectivity and stereochemistry. XRD measurements revealed that polysaccharides 2a and 2b had crystalline structures similar to that of alpha-chitin. [reaction: see text]     

Mineral composition of frozen taro for determination of geographic origin

The mineral composition of frozen food of taro [Colocasia esculenta (L.) Schott] was analyzed to categorize the geographical production place of taro. The concentrations of Co and H₂PO₄ ⁻ were found to be useful to separate the producing place between Japan and China. The analysis was performed by instrumental neutron activation analysis (INAA) and ion chromatography (IC). In the case of INAA, the samples were dried and sealed in a vinyl bag and irradiated with thermal neutrons from JRR3M, installed at Japan Atomic Energy Agency (JAEA). The activated samples were cooled down for a few weeks and the elements (Co, Cr, Fe, Rb, Zn) were determined. Cobalt concentration of frozen taro from China was higher than that from Japan. The tendency was the same in the fresh sample of taro. When concentration of H₂PO₄ ⁻ of frozen sample was measured, taro from Japanese product was higher than that of Chinese one, contrary to fresh sample. This result might be caused by the leakage of H₂PO₄ ⁻ during freezing process, indicating that we should be careful to apply the discrimination indicators. In addition to Co, there was a significant difference of Rb and Fe concentrations between frozen taro from Japan and China.     

Enzymatic synthesis of chondroitin and its derivatives catalyzed by hyaluronidase

The enzymatic polymerization to provide synthetic chondroitin and its derivatives is reported here, the first example of such in vitro synthesis to date. N-Acetylchondrosine (GlcAbeta(1-->3)GalNAc) oxazoline (1a) and its derivatives (1b-1f) were designed and synthesized as novel transition state analogue substrate monomers for catalysis by hyaluronidase. Hyaluronidase is a hydrolysis enzyme of chondroitin that also catalyzes the formation of repeated glycosidic bonds in in vitro synthesis, rather than in the catabolic direction. Monomers of 2-methyl (1a), 2-ethyl (1b), and 2-vinyl (1f) oxazoline derivatives were polymerized using this enzyme, via ring-opening polyaddition with total control of regioselectivity and stereochemistry. These reactions provided the corresponding synthetic chondroitin (natural type; N-acetyl, 2a) and the derivatives (unnatural type) with N-propionyl (2b) and N-acryloyl (2f) functional groups at the C2 position of all the galactosamine units, in good yields. Monomers of 2-n-propyl (1c) and 2-isopropyl (1d) oxazoline derivatives were polymerized to produce 2c and 2d in low yield. The 2-phenyl oxazoline derivative (1e) did not afford any enzyme-catalyzed products. M(n) values of 2a and 2b reached 4800 and 4000, respectively. The M(n) value of 2a corresponds to that of the naturally occurring chondroitin. Thus, hyaluronidase catalysis allows the in vitro production of not only natural type but also the formation of unnatural type chondroitins.     

Nondestructive real-time radioisotope imaging system for visualizing 14C-labeled chemicals supplied as CO2 in plants using Arabidopsis thaliana

We have developed a real-time radioisotope imaging system (RRIS) that can nondestructively trace ¹⁴C-labeled chemicals in plants. In an experiment, after feeding ¹⁴CO₂ to a plant, the plant was fixed inside a box where lighting was regulated, and beta rays emitted from the ¹⁴C in the plant were intermittently imaged using the developed system. As a first step, using a series of standard sources of ¹⁴C, the data depth and detection limits of the ¹⁴C images captured by the RRIS were evaluated for various integral times. As a result, the linearity between the ¹⁴C activity and signal intensity was determined for the range 10³. Next, the linearity was validated using plant (Arabidopsis thaliana) organs, resulting that the linearity was shown in the case of young leaf, but was not maintained in the thick organs, such as a flower, mature leaf, siliques, and stem. Considering the good correlation between the intensity by RRIS and the PSL value by an imaging plate (IP) as well as the relative low energy of beta rays emitted from ¹⁴C, the thickness of the organs would easily affect the quantitativity of the RRIS as well as an IP. Our findings prove that sequential images of ¹⁴C in a living plant sample in a regulated light and air environment can be nondestructively analyzed using the developed system, whose quantitativity is similar to that of an IP.     

A hyaluronidase supercatalyst for the enzymatic polymerization to synthesize glycosaminoglycans

Hyaluronidase (HAase) catalyzes multiple enzymatic polymerizations with controlling regio- and stereoselectivity perfectly. This behavior, that is, the single enzyme being effective for multireactions and retaining the enzyme catalytic specificity, is not usual, and hence, HAase is a supercatalyst. Various sugar oxazoline monomers prepared based on the concept "transition-state analogue substrate" were successfully polymerized and copolymerized with HAase catalysis, yielding natural and unnatural glycosaminoglycans.     

Contact angle hysteresis in carbon fibers studied by wetting force measurements

The surface free energy of polyacrylonitrile carbon fibers was investigated by using the Wilhelmy technique. The difference in surface free energy between immersion and emersion was observed for the carbon fiber pyrolyzed at 2500 °C.In contrast, the hysteresis disappeared with repyrolyzation of the carbon fibers at 3000 °C. Auger electron spectroscopic analysis indicated that the surface of the latter carbon fiber (repyrolyzed at 3000 °C) consisted of the basal planes of graphite. Rough surface topography of the carbon fiber repyrolyzed at 3000 °C, as observed by scanning electron microscope, did not affect the hysteresis. Therefore, the contact angle hysteresis was attributed to the chemical adsorbants on the activation sites of the fiber surfaces, as detected by Auger electron spectroscopy.     

Enzyme-catalyzed synthesis of natural and unnatural polysaccharides

Synthesis of natural and unnatural polysaccharide was achieved via “enzymatic polymerization” by utilizing a glycoside hydrolase as catalyst. Particularly, hyaluronan, chondroitin, and their derivatives belonging to glycosaminoglycans have been prepared using sugar oxazoline monomers designed on the basis of the concept “transition-state analogue substrate”. The oxazoline derivatives of N-acetylhyalobiuronate [GlcAβ(1→3)GlcNAc] and N-acetylchondrosine [GlcAβ(1→3)GalNAc], which have the repeating disaccharide structures of hyaluronan and chondroitin, respectively, were successfully polymerized by the catalysis of hyaluronidase, giving rise to synthetic hyaluronan and chondroitin. Their 2-substituted oxazoline derivatives were also polymerized to the corresponding N-acylated hyaluronan and chondroitin derivatives. Furthermore, N-acetylchondrosine oxazoline derivatives sulfated at the C4, the C6, and both the C4 and C6 of the GalNAc unit were catalyzed by hyaluronidase; the monomer sulfated at the C4 was polymerized to chondroitin 4-sulfate with well-defined structure, whereas the other two monomers were exclusively hydrolyzed to the corresponding disaccharides. These different kinds of natural and unnatural polysaccharides having relatively high molecular weights were produced in all cases by the catalysis of hyaluronidase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5014–5027, 2006