Novel glycosylated mycosporine-like amino acids with radical scavenging activity from the cyanobacterium Nostoc commune

Mycosporine-like amino acids (MAAs) are UV absorbing pigments, and structurally distinct MAAs have been identified in taxonomically diverse organisms. Two novel MAAs were purified from the cyanobacterium Nostoc commune, and their chemical structures were characterized. An MAA with an absorption maximum at 335 nm was identified as a pentose-bound porphyra-334 derivative with a molecular mass of 478 Da. Another identified MAA had double absorption maxima at 312 and 340 nm and a molecular mass of 1,050 Da. Its unique structure consisted of two distinct chromophores of 3-aminocyclohexen-1-one and 1,3-diaminocyclohexen and two pentose and hexose sugars. These MAAs had radical scavenging activity in vitro; the 1050-Da MAA contributed approximately 27% of the total radical scavenging activities in a water extract of N. commune. These results suggest that these glycosylated MAAs have multiple roles as a UV protectant and an antioxidant relevant to anhydrobiosis in N. commune.     

Synthesis of uronic-noeurostegine--a potent bacterial β-glucuronidase inhibitor

Inhibition of β-glucuronidases has recently been shown to be useful in alleviating drug toxicity for common colon cancer chemotherapeutic CPT-11 (also called Irinotecan). We have prepared a new compound of the nortropane-type, uronic-Noeurostegine, and demonstrated that this is a competitive and potent E. coli β-glucuronidase inhibitor, while inhibition of the mammalian β-glucuronidase from bovine liver was found to be less significant. Although not intended, two other compounds having N-ethyl and N-(4-hydroxybutyl) substituents were also prepared in this study due to the sluggish debenzylation in the final step. The N-substituents are believed to come from reaction with the solvents used being ethanol and THF, respectively. These compounds also inhibited the two β-glucuronidases albeit to a lesser extent compared to the parent compound. Noeurostegine and the three uronic-noeurostegines were additionally evaluated as inhibitors against a wide panel of glycosidases with the former showing potent inhibition of rat intestinal lactase and trehalase, whereas the latter was found to be inactive.     

Maedamide,a novel chymotrypsin inhibitor from a marine cyanobacterial assemblage of Lyngbya sp.

Maedamide, a novel chymotrypsin-inhibiting depsipeptide, was isolated from a cyanobacterial assemblage that mostly consisted of Lyngbya sp. Its structure was elucidated by spectroscopic analyses and chiral HPLC analyses of hydrolysis products. Maedamide selectively inhibited chymotrypsin but not elastase and trypsin. In addition, Maedamide strongly inhibited the growth of HeLa cells and HL60 cells.     

Bias-corrected AIC for selecting variables in multinomial logistic regression models

In this paper, we consider the bias correction of Akaike’s information criterion (AIC) for selecting variables in multinomial logistic regression models. For simplifying a formula of the bias-corrected AIC, we calculate the bias of the AIC to a risk function through the expectations of partial derivatives of the negative log-likelihood function. As a result, we can express the bias correction term of the bias-corrected AIC with only three matrices consisting of the second, third, and fourth derivatives of the negative log-likelihood function. By conducting numerical studies, we verify that the proposed bias-corrected AIC performs better than the crude AIC.     

Competitive Trapping of Nitric Oxide (NO) Between Fe(III)-dithiocarbamate Complex and Liposome-encapsulated Trimethylammonio-PTIO: Effects of Ligand Structure, Charge on Liposome Surface, and External Pressure on NO-trapping Rates

Using a competitive nitric oxide (NO)-trapping method between Fe–dithiocarbamate (DTC) complexes and liposome-encapsulated 2-[4-trimethylammonio]-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (TMAPTIO), NO-trapping rates of Fe–DTC complexes in the presence of phosphatidylcholine liposomes were quantified for five kinds of Fe–DTC complexes. We investigated how the DTC ligand structure influences the NO-trapping rates of Fe–DTC complexes. The negatively charged liposomes give a higher NO-trapping rate of Fe–DTC complexes than do the positively charged ones, suggesting that the presence of a charge on the liposome surface affects the NO-trapping rate processes of Fe–DTC complexes. In addition, on the basis of the pressure dependence experiments for the competitive reaction, we evaluated the difference in activation volumes between the NO-trapping reactions by Fe–DTC complexes and TMA-PTIO, which allowed us to consider possible reaction mechanisms for the NO-trapping processes.     

AFM observation of cation complexation of dibenzocrown ethers adsorbed on highly oriented pyrolytic graphite

The cation complexation behavior of dibenzocrown ethers adsorbed on highly oriented pyrolytic graphite substrates was investigated by means of atomic force microscopy using probe tips modified chemically with ammonium ion by silane coupling. The specific adhesion force based on the intermolecular force between dibenzocrown ether and ammonium ion was observed via force curve measurements in ethanol at the interface between the substrate and tip. The observed specific force decreased in the presence of the alkali metal ion in solution, indicating that the cation in solution interferes with the complexation of the crown ethers adsorbed on the substrate with the ammonium ion immobilized on the tip. The blocking effect of metal ions in solution on the observed force depended on the sizes of both the blocking cation and crown ether ring, suggesting that the surface-adsorbed dibenzocrown ethers possess a selective cation-complexing ability similar to that in their bulk state and that the adhesion force measurements using cation-modified tips allow evaluation of the cation-complexing ability of crown ethers under cation-competitive conditions.     

Low temperature solventless synthesis and characterization of Ni and Fe magnetic nanoparticles

We have successfully implemented a facile, one-pot solventless synthesis procedure starting from acetylacetonate salts and CaH(2) to obtain carbon-coated ferromagnetic metallic Ni and Fe nanoparticles at low temperature. The use of CaH(2) as a reductant drastically reduces reaction temperature down to 140 °C.     

Fabrication of a Kagomé-type MOF Membrane by Seeded Growth on Amino-functionalized Porous Al2O3 Substrate

In this study, we report an efficient fabrication method for the membrane of a metal-organic framework (MOF) (Kgm−OEt) which is one kind of kagomé-type MOF with a two-dimensional (2D) sheet structure having one-dimensional (1D) channels suitable for separation of H₂ from other larger gases. The Kgm−OEt seed layer was created on an Al₂O₃ substrate using layer-by-layer (LBL) growth, then a membrane was fabricated by secondary growth. The membrane on a 3-aminopropyltriethoxysilane (APTEs)-treated substrate obtained in this method was continuous and defect-free with the crystal orientation suitable for gas transportation, while the membrane grown on an unmodified substrate was loosely packed with unfavorable crystal orientation.     

Changes in biochemical properties of ovomucoid by radiation

Radiation effects on biochemical properties of ovomucoid, a protease inhibitor which is a typical allergenic protein of egg, were investigated. Trypsin inhibiting activity of ovomucoid decreased exponentially and the inactivation was larger in N₂ than in O₂. The antigenicity of ovomucoid measured by ELISA was decreased exponentially and the inactivation curves were almost the same as that of trypsin inhibiting activity. These results show that the oxygen protects the inactivation and destruction of antigenicity of ovomucoid while it enhances the reaction with ovalbumin. The effect of radiolytically generated radical anions; a pronounced protective action of (CNS)₂⁻ and a slight accelerate action of Br₂⁻ were the same both on decrease in trypsin inhibiting activity and antigenicity. SDS-PAGE showed that the change in protein structure was also protected by (CNS)₂⁻. These results suggest that the changes by radiation were not mainly due to the destruction of essential amino acid residues but to the conformational change.