Synthesis and structure/property relationships of regioselective 2-O-, 3-O- and 6-O-ethyl celluloses.

Regioselectively ethylated celluloses, 2-O- (1), 3-O- (2), and 6-O-ethyl- (3) celluloses were synthesized via ring-opening polymerization of glucopyranose orthopivalate derivatives. The number-average degrees of polymerization (DP(n)s) of compounds 1 and 2 were calculated to be 10.6 and 49.4, respectively. Three kinds of compound 3 with different DP(n)s were prepared: DP(n)s = 12.9 (3-1), 60.3 (3-2), and 36.1 (3-3). The 2-O-, 3-O-, and 6-O-ethylcelluloses were soluble in water, confirmed by NMR analysis. Furthermore, the 3-O- (2), and 6-O-ethyl- (3-2) celluloses showed thermo-responsive aggregation behavior and had a lower critical solution temperature (LCST) at about 40 degrees C and 70 degrees C, respectively, based on the results from turbidity tests and DSC measurements. The 6-O-ethyl-cellulose (3-3) with DP(n) = 36.1 and DP(w) = 54.6 showed gelation behavior over approx 70 degrees C, whereas the 6-O-ethyl-celluloses 3-1 and 3-2 with lower and higher molecular weight, such as DP(n)s 12.9 and 60.3, did not show gelation behavior at this temperature. It was revealed that the position of ethyl group affected the phase transition temperature. According to our experiments, the 3-O-ethyl and 6-O-ethyl groups along the cellulose chains caused the thermo-responsive property of their aqueous solutions. The appropriate DP of the regioselective 6-O-ethyl-cellulose existed for gelation of the aqueous solution.

Preparation and characterization of monolayer and multilayer Langmuir-Blodgett films of a series of 6-O-alkylcelluloses.

Monolayer and multilayer Langmuir-Blodgett (LB) films of 6-O-alkylcelluloses with various chain lengths were prepared and studied. The surface pressure (pi)-area (A) isotherms of 6-O-alkylcelluloses exhibited characteristic behaviors depending on the length of the alkyl chain and temperature. 6-O-Stearylcellulose on the subphase formed a homogeneous monolayer at 10 mN m(-1). By transfer ratio, FT-IR, and contact angle measurements, it was proved that the monolayer of 6-O-stearylcellulose on the water surface was transferred successfully onto a substrate by a vertical dipping method to form a Z-type LB film. The transmission and reflection absorption IR spectrum indicated that the hydrocarbon chains had all-trans rotamers and were oriented nearly perpendicular to the surface in the film. AFM section analysis revealed that the thickness per layer was calculated to be 2.35 nm. These results suggested that the hydrocarbon chains were inclined at an angle of about 25.3 degrees to have high packing density in the alkyl region.

Involvement of hepatic glucocorticoid receptor-mediated functions in steroid-induced cataract formation.

Determination of whether the steroid-induced cataract formation is caused through glucocorticoid (GC) receptor-mediated process was conducted by using GC antagonist (RU486) and anti-GC receptor antibody, and by sucrose density gradient ultracentrifugation analysis. (1) When 15 day-old chick embryos were treated with dexamethasone (DEX, 0.025 micromol per egg), their lenses started to form an opaque ring around the peri-nuclear region (stage II-III) after 12 hr and developed into nuclear-like cataract (stage IV-V) after 44 hr. The cataract formation examined at the 44 hr could be effectively prevented by administration of RU486 (0.2 micromol per egg) ranging from 2 hr before to 12 hr after the DEX administration. (2) GC receptor was present in liver, but could not be determined in lens by western blot analysis using monoclonal anti-GC receptor antibody. (3) Sucrose gradient ultracentrifugation analysis indicated that the receptor (9S) in the liver could be transformed to the 4S form after 0.4M NaCl treatment. Combined with our previous data, this suggests that changes in hepatic functions mediated by the GC receptor after the GC administration may be involved in the process of the cataract formation.