Synthesis of ZnS, CdS and Core-Shell Mixed CdS/ZnS, ZnS/CdS Nanocrystals in Tapioca Starch Matrix

Gel of tapioca starch (TS) is a suitable matrix for the formation of ZnS, CdS and core-shell ZnS/CdS as well as CdS/ZnS quantum dots (QDs). These QDs reside in the matrix as non-agglomerating 3 - 10 nm nanocrystals. It is demonstrated that amylopectin is responsible for the QDs formation rather than amylose. Combination of ZnS with CdS in the core-shell QDs results in the increase in the intensity of emission without any shift of its wavelength.

Silver and Gold Nanoparticles Embedded in Potato Starch Gel Films

Facile and environmentally friendly method of the preparation of silver and gold nanoparticles embedded in potato starch matrix (Sp) was developed. UVVIS spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectra confirmed formation of ball shaped Ag and Au nanoparticles situated within the polysaccharide template. EDS spectra confirm presence of silver and gold nanocrystals in the obtained composites. Differential scanning calorimetry (DSC) showed that Sp/Au composite started to decompose earlier. The decomposition is slower and two-step, in contrast to Sp and Sp/Ag. NanoAg accelerates carbonization. Molecular weights of polysaccharide chains of the matrix were estimated with the size exclusion chromatography coupled with multiangle laser light scattering and refractometric detectors (HPSEC-MALLS-RI). Formation of nanosilver containing composites led to partial depolymerisation of polysaccharides from the amylose fraction. In the case of nanogold we observed depolymerisation of polysaccharide chains from both fractions.

Stimulation of Selected Cellulases from Trichoderma reesei with White Linearly Polarized Light

The impact of the illumination with white linearly polarized light (WLPL) of two commercially available cellulases from Trichoderma reesei on their activity in hydrolysis of microcrystalline cellulose was studied. Enzymes were illuminated with WLPL for 60 min and 120 min and for each native and illuminated enzyme sample specific activity and kinetics of enzyme catalyzed hydrolysis of microcrystalline cellulose were established. Molecular weight Mw and radii if gyration Rg of protein chains of native and illuminated enzymes were measured by means of high pressure size exclu-sion chromatography coupled with multiangle laser light scattering and refractometric detectors (HPSEC-MALLS-RI). Conformations of protein chains of native and illuminated enzymes were evaluated on the basis of their circular dichroism (CD) spectra. Additionally, molecular weight Mw and radii of gyration Rg of polysaccharide chains of microcrystalline cellulose native and digested for 10 min, 480 min and 1440 min with original and WLPL stimulated enzymes WT and TR were taken. Illumination with WLPL of both cellulases studied did not change secondary structures of protein molecules of native enzyme. Molecular weight Mw and radii of gyration Rg of illuminated enzymes differed greatly from those found for native enzymes. Illumination of enzymes led to increase of specific activity and rate constants of reaction of hydrolysis microcrystalline cellulose catalyzed by illuminated enzymes as compared with native enzymes.

Radioprotective thermally generated free-radical dextrins

Effect of doses of the X-ray radiation from 0 to 400 Gy upon granular cornstarch and dextrins (British gums, BG) thermally generated from it at 230-300℃ was recognized with quantitative EPR and IR ab-sorption spectroscopy, molecular mass distribution in the depolymerization products, Scanning Elec-tron Microscopy, and X-ray diffractometry. Fractal analysis of the profiles of molecular mass distribu-tion showed that the depolymerization involved debranching of amylopectin. Roasting of cornstarch produced BG which differed in concentration and EPR parameters of stable free radicals from BG generated by X-ray radiation. Two types of stable free radicals, with Gaussian and Lorentzian shapes of EPR signals, were recognized. The shapes of the signals and temperature dependence on free radical intensity indicated exchanging interactions of the antiferromagnetic type, causing partial quenching of the spins at-196℃ (77K). Upon X-ray irradiation, new radicals were generated, the number and stability of which strongly depended on the types of radicals present before irradiation. These radicals slowly ceased because of a repolymerization of BG on storage.