[Spectra analyses of chitosans degraded by hydrogen peroxide under optimal conditions].

Chitosans with different average molecular weight (1,500-156 kDa) were prepared under optimal conditions based on our previous research by the depolymerization of initial chitosan using hydrogen peroxide, with maintaining the native structure of natural chitosan as principal consideration. Nitrogen and Carbon components of initial chitosan and degraded products were analyzed by BUCHI fully automatic nitrogen determination system and Liquid total organic carbon (TOC) analyzer respectively. Fourier transform infrared (FTIR), 13C nuclear magnetic resonance (13C NMR), X-ray diffraction and circular dichroism (CD) analyses were used to characterize the structure properties of samples. The results indicated that the maximum standard deviations of carbon content and nitrogen content and the degree of deacetylation (DD) of degraded products with the corresponding values of the initial chitosan are 2.4%, 2.3% and 6.9% respectively. Besides, the differentiations of the nitrogen content and DD value of the degraded product with the corresponding values of the initial chitosan are narrowed with the increase in the reaction time. FTIR spectra of resulting products are similar to that of initial chitosan in terms of peak number and position, indicating that there are no other functional groups formed during the degradation. 13C-NMR analyses of initial chitosan and degraded products revealed that the chemical structures of resulting chitosans are not changed to any noticeable extent. X-ray diffraction patterns of initial chitosan and degraded chitosans are alike and show characteristic peaks at 2theta = 10. 4 degrees and 19.8 degrees under the condition that the initial chitosan was disposed as degraded chitosans. Circular dichroism analyses showed that all the samples exhibit a broad negative band located at about 210 nm assigned to n --> pi* electronic transition of the --NH--CO-- chromophore on a glycosidic ring in acidic media, which demonstrated that degraded chitosans maintain their natural conformation in liquid state substantially. All these confirmed that the degraded chtiosans maintain their natural structure and conformation, and the breakage of beta-1,4-glucoside bonds in macromolecule is the basic process under optimal degradation conditions.

[Synthesis, characterization and antimicrobial activity of konjac glucomannan derivative with quaternary ammonium salts].

Methacryloxylethyl tetradecyl dimethyl ammonium bromide was grafted onto konjac glucomannan using ceric ammonium nitrate as an initiator, and the konjac glucomannan derivative with quaternary ammonium salts was obtained. The konjac glucomannan derivative was investigated by hydrogen nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), and Zeta sizer nano series. The antimicrobial properties of the konjac glucomannan derivative against selected microorganisms were tested by the quantitative suspension method. The results revealed that (1) methacryloxylethyl tetradecyl dimethyl ammonium bromide can be grafted onto the surface of the konjac glucomannan, and the percentage grafting increases with increasing the amount of methacryloxylethyl tetradecyl dimethyl ammonium bromide. (2) The Zeta potential showed that the isoelectric point of the konjac glucomannan and the modified konjac glucomannan is pH 4. 5 and pH 9. 9, respectively. The shift of the isoelectric point is due to the quaternary ammonium groups. (3) The obtained konjac glucomannan derivative has significant inhibition effect on the growth of microorganisms, and the bactericidal rates in 15 min for E. coil (8099), S. aureus (ATCC 6538) and C. albicans (ATCC10231) were 99.99%, 99.99% and 98.13%, respectively.

[Synthesis, characterization and antimicrobial activity of nano-fumed silica derivative with quaternary ammonium salts].

Nano-fumed silica reacted with gamma-chlopropyltrimethoxysilane as a coupling agent, and then by quaternization with N,N-dimethyl-n-tetradecylamine, finally the nano-fumed silica derivative with quaternary ammonium salts was obtained. The nano-fumed silica derivative was investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), and Zeta sizer nano series. The antimicrobial properties of the nano-fumed silica derivative against selected microorganisms were tested by the quantitative suspension method. The results revealed that (1) gamma-chlopropyltrimethoxysilane can be bound to the surface of the nano-fumed silica With increasing the amount of gamma-chlopropyltrimethoxysilane, the amount of surface hydroxyl groups of nano-fumed silica decreases. (2) The Zeta potential showed that the isoelectric point of the nano-fumed silica and the modified nano-fumed silica is pH 4.8 and pH 10.5, respectively. The shift of the isoelectric point is due to the quaternary ammonium groups. (3) The obtained nano-fumed silica derivative has significant inhibition effect on the growth of microorganisms, and the bactericidal rates in 15 min for E. coil (8099), S. aureus (ATCC6538) and C. albicans(ATCC10231) were 99.99%,, 99.99% and 94.12%, respectively.