ABSTRACT
Lasing from zirconia inverse opal photonic crystal structures infiltrated by solutions of rhodamine dyes was found to exhibit single-mode lasing peaks with spectral width less than 1 nm and quality factor in excess of 4000. The lasing occurs within the approximate range of high-reflectance spectral region associated with photonic stop band along [111] crystallographic direction, but its wavelength is not fixed to the corresponding Bragg wavelength of the periodic structure, and depends on the spectral position of the gain band. This lasing regime can be useful for realizing tunable single-mode photonic crystal lasers.
Subject(s)
Computer-Aided Design , Crystallization/methods , Lasers , Models, Theoretical , Refractometry/instrumentation , Zirconium/chemistry , Computer Simulation , Equipment Design , Equipment Failure Analysis , PhotonsABSTRACT
Insulin is stored in pancreatic beta-cell as hexameric form with Zn2+ ions, while the hormonally active form is monomer. The hexamer requires the coordination of Zn2+ ions to the HisB10. In order to reveal the mechanism of the hexamerization of insulin, we investigated the Zn2+ free insulin at pD6.6 and pD9 by neutron crystallographic analyses. HisB10 is doubly protonated not only at pD6.6 but also at pD9, indicating an abnormal pK(a) of this histidine. It is suggested that HisB10 acts on a strong cation capture and contributes to the high stability of the hexameric form in pancreas.
Subject(s)
Histidine/chemistry , Insulin/chemistry , Neutron Diffraction , Animals , Swine , Zinc/chemistryABSTRACT
2-O-(beta-D-Glucopyranosyl)ascorbic acid (AA 2 beta G) isolated from a popular traditional Chinese food (Lycium fruit) was synthesized using cellulase derived from Trichoderma sp. with cellobiose as a glucose donor. 6-O-(beta-D-Glucopyranosyl)ascorbic acid as well as AA 2 beta G was also synthesized in this reaction. The vitamin C activity of AA 2 beta G was also evaluated using inherently scorbutic (osteogenic disorder Shionogi [ODS]) rats. The rats were fed vitamin C-deficient food and water containing AA 2 beta G for 21. AA 2 beta G supported their growth and the level of vitamin C in tissues was moderately maintained. The vitamin C level in some tissues depended on the hydrolytic activity of AA 2 beta G (beta-glucosidase activity) although the correlation was not statistically significant (P=0.08). The results indicate that AA 2 beta G has pro-vitamin C activity.
Subject(s)
Ascorbic Acid/analogs & derivatives , Body Weight/drug effects , Cellobiose/chemistry , Cellulase/chemistry , Trichoderma/enzymology , Administration, Oral , Animals , Ascorbic Acid/administration & dosage , Ascorbic Acid/chemistry , Dietary Supplements , Enzyme Activation , Male , RatsABSTRACT
Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins. High-resolution neutron diffractometers dedicated to biological macromolecules (BIX-type diffractometer) have been constructed at the Japan Atomic Energy Research Institute and they have been used in the 1.5A-resolution crystal structure analyses of several proteins. Interesting topics relevant to hydrogen and hydration in proteins, such as (1) the detailed geometry of hydrogen bonds; (2) information regarding hydrogen/deuterium exchange behavior; (3) the acidities of certain H atoms; (4) the role of hydrogen atoms in enzyme mechanisms and thermostability; (5) the location methyl hydrogen atoms; and (6) dynamical behavior of hydration structures that include H positions have been extracted from these structural results. In addition, a method for the systematic growth of large single crystals based on phase diagrams has been introduced and will be briefly described in this article.
Subject(s)
Proteins/chemistry , Crystallization , Crystallography, X-Ray , Deuterium , Drug Stability , Enzymes/chemistry , Histidine/chemistry , Hydrogen/chemistry , Hydrogen Bonding , Models, Molecular , Neutron Diffraction , Water/chemistryABSTRACT
A novel stable precursor of ascorbic acid (vitamin C), 2-O-(beta-D-glucopyranosyl)ascorbic acid, was isolated from both the ripe fresh fruit and dried fruit of Lycium barbarum L., a plant of the Solanaceae family. The chemical structure was inferred by instrumental analyses and confirmed by chemical synthesis. The dried fruit of Lycium barbarum L. contained ca. 0.5% of it, which is comparable to the ascorbic acid content of fresh lemons. It increased the blood ascorbic acid by oral administration to rats, and it was also detected in blood from the portal vein.
