Palladium adsorbing properties of UV-curable chitosan derivatives and surface analysis of chitosan-containing paint.

The results of X-ray photoelectron spectroscopy (XPS) analyses indicated that palladium chloride was adsorbed on a plastic surface coated with a chitosan-containing paint (C-Paint), and was completely reduced to Pd(0) after reduction with dimethylamine-borane. To improve the stability and hardening properties of C-Paint, UV-curable chitosan derivatives, such as N-[3-methoxy-4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]methylated chitosan and N-(3-methoxy-4-methacryloyloxyphenyl)methylated chitosan, were synthesized. The derivatives showed better affinity for organic solvents. After UV irradiation for 20s, an acidic solution of these derivatives was transformed to a gel, and the dried films exhibited good palladium(II) adsorption at pH 1.1.

Synthesis of D-xylopyranan by the ring-opening polymerization of 3-O-benzyl-alpha-D-xylopyranose 1,2,4-orthopivalate. Attempts to synthesize a stereoregular polymer.

3-O-Benzyl-alpha-D-xylopyranose 1,2,4-orthopivalate (1) was newly synthesized and polymerized under cationic polymerization reaction conditions in order to synthesize stereoregular (1-->4)-beta-D-xylopyranan. Although the polymerization of orthopivalate 1 was carried out under various reaction conditions, a non-stereoregular polymer, but mainly consisting of (1-->4)-beta-xylopyranose units, was obtained. Comparing these results with those of glucose 1,2,4-orthopivalates, it was revealed that not only the substituents in the C-2 and C-3 positions, but also the CH(2)OR group in glucose 1,2,4-orthopivalate, largely contribute to (1-->4)-beta-glucosidic bond formation by the ring-opening polymerization.

Binding nature and denaturation of protein during interaction with galloylglucose.

Analysis of insoluble complexes between tetragalloylglucose and proteins following a series of successive washes with buffer indicated (1) heterogeneity of binding between galloylglucose and protein and (2) irreversible denaturation of protein during interaction with galloylglucose. Relatively large amounts of tetragalloylglucose were removed by initial washes, indicating weak, low affinity binding, whereas smaller amounts removed by subsequent washes suggest bonds with a higher affinity. Although the maximum number of bindings sites, calculated per 10,000 M(r) of protein, was similar for BSA, myoglobin and lysozyme, the proportion of these sites that appeared to have high affinity, varied from 8 to 29%. The low proportion of strongly binding sites in lysozyme explains its relatively low tannin-complexing ability. Solubility decrease in protein during successive washing and decrease in the beta-glucosidase activity indicate that irreversible denaturation of protein occurs, which progresses with an increase in the incubation time with galloylglucose and galloylglucose/protein molar ratio in the mixture. Relative affinity of galloylglucose is directly related to the ability to cause irreversible denaturation.

First synthesis of cellooctaose by a convergent synthetic method.

The first chemical synthesis of cellooctaose by a convergent synthetic method is described. A challenging glycosylation between cellotetraosyl donor 5 and acceptor 7 proceeded in a one-step reaction using a high-vacuum system for anhydrous glycosylation and minimizing imidate side reactions such as hydrolysis and glycosyl fluoride formation. Pivaloyl, allyl, and benzyl protecting groups of cellooctaose derivative 8 were completely removed with SeO2-AcOH, NaOMe-MeOH, and H2/Pd(OH)2-C, respectively. The acetylation after each deprotection step finally led to cellooctaose hexacosaacetate (20), which is useful for purification and structural identification. Finally, the acetyl derivative 20 was deacetylated with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 20% MeOH-CH2Cl2 to give pure cellooctaose (21). The analogous synthetic route to the present convergent synthetic design of cellooctaose may be a most promising one that enables us to synthesize cellulose with a defined degree of polymerization (dp).

Stoichiometric studies of tannin-protein co-precipitation.

Co-precipitation of a series of galloylglucoses (hydrolysable tannins) with bovine serum albumin (BSA) was studied stoichiometrically by analysing both galloylglucoses and BSA in the precipitates using HPLC. BSA-precipitating ability increased mainly with an increase in the number of galloyl groups in a galloylglucose molecule but was also affected by the position of the galloyl group (penta- > tetra- > 2,3,6-tri- > 2,3,4-tri- >> di- >> monogalloylglucose). The precipitated BSA increased linearly with an increase in the number of galloyl groups bound to a BSA molecule. BSA-precipitating abilities of the galloylglucoses were closely related to their relative affinities for BSA. These results suggest a two-stage mechanism: initial complexation of galloylglucose with BSA and subsequent precipitation, as a mechanism of the co-precipitation.

Further study discounts role for singlet oxygen in fungal degradation of lignin model compounds.

This study reexamined our contention that singlet oxygen (1O2) plays a role in the fungal degradation of lignin (BBRC 102(1981)484). Cultures of Phanerochaete chrysosporium and a photochemical 1O2-generating system (riboflavin/light/O2) cleaved a lignin substructure model compound, 1,2-bis(4-methoxyphenyl)propane-1,3-diol (I), by indistinguishable mechanisms. However, the rate of cleavage of I in D2O was the same as in H2O in the photochemical 1O2-generating system, indicating that 1O2 was not involved. Furthermore, products formed from I in a chemical system for generating 1O2 (H2O2 + NaOCl) differed from those produced by cultures or the photochemical system. It is concluded that 1O2 is not responsible for cleavage of I or related compounds in the fungal cultures or in the photochemical system.