Deprotonation Processes of Ellagic Acid in Solution and Solid States

Monatshefte für Chemie - Chemical Monthly - ?The electronic absorption and polarized absorption spectra were measured at various pH conditions for ellagic acid. Comparison of these...     

Adsorption behavior of cytochrome c, myoglobin and hemoglobin in a quartz surface probed using slab optical waveguide (SOWG) spectroscopy.

Slab optical waveguide (SOWG) spectroscopy was used to observe the adsorption behavior of three important heme proteins, namely cytochrome c, myoglobin and hemoglobin, in a quartz surface. Using prism-coupled polychromatic visible light propagated into a quartz waveguide by internal total reflection, the real-time monitoring of evanescent wave absorption revealed a strong dependence of the protein-surface interaction on the protein concentration, the solution pH and the ionic strength. For the three proteins studied, the absorbance-bulk concentration ratio was higher at low bulk concentrations, and decreased at higher concentrations. For cytochrome c and myoglobin, the absorbance approached a limiting value, but buffered hemoglobin surprisingly did not show any indication of forming a signal plateau. Moreover, the slow introduction of protein into the solution lessened the total adsorbed amount per unit area. These observations suggested a possible conformational transition of the protein molecules at the quartz surface after adsorption. For a bulkier protein, hemoglobin, adsorption onto the quartz surface was enhanced in the presence of a phosphate buffer, while the opposite effect was observed for the smaller cytochrome c and myoglobin molecules. The results of pH studies concurred with the electrostatic interactions predicted from the isoelectric data of proteins and the quartz surface.     

Low-temperature heat capacity of TMS monolayers adsorbed on graphite and MgO+

The heat capacity obtained below 30 K for the tetramethylsilane monolayers, which are adsorbed either on graphite or on the (100) surface of MgO, is analyzed to investigate the vibrational properties. The 2-D Debye temperatures are approximately 60% of the Debye temperature of the bulk solid (γ -phase), reflecting the dimensionality of lattice vibrations. The contributions from the vibrations perpendicular to the surface as well as the librational motions are determined by fitting the experimental heat capacities. All the results are consistent with those obtained from the incoherent inelastic neutron scattering and the molecular dynamics simulation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of sulfur‐containing hyperbranched polymers by the bisthiolation polymerization of diethynyl disulfide derivatives

The reaction of phenyl propynyl ether and diphenyl disulfide in the presence of 1 mol % tetrakis(triphenylphosphine)palladium as a model reaction of the polymerization of bis(4‐prop‐2‐ynyloxyphenyl) disulfide ( 1a ) gave a Z‐substituted dithioalkene. No E‐substituted dithioalkene was formed in this reaction. The palladium‐catalyzed bisthiolation polymerization of a diethynyl disulfide derivative, 1a , in benzene, was carried out to give a hyperbranched polymer ( 5a ) containing a Z‐substituted dithioalkene unit after reaction for 4 h at 70 °C. From the gel permeation chromatography analysis (chloroform, PSt standards), the number‐average and weight‐average molecular weights of 5a were found to be 8,100 and 57,000, respectively. The structure of 5a was confirmed by ¹H and ¹³C NMR spectra. The obtained polymer was soluble in common organic solvents such as benzene, acetone, and CHCl₃. Polymerization for more than 5 h gave insoluble products. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3580–3587, 2007     

Method performance study of the determination of total nitrogen in soy sauce by the Kjeldahl method.

The objective of this collaborative study was to evaluate the proposed method for determining the total nitrogen in soy sauce by the Kjeldahl method submitted to the Codex Alimentarius Commission for endorsement in accordance with the protocol for the design, conduct, and interpretation of method-performance studies. The digestive conditions of the proposed method are the addition of 10 mL of H2SO4, 10 g (8 g by using a block digester) of K2SO4, and 1 mL of 20% CuSO4 x 5H2O and 80 min boiling period after the liquid is cleared by a heating device. Seventeen laboratories participated, analyzing five soy sauce samples as blind duplicates. Since the volume sampling method used in the JAS (Japanese Agricultural Standard) method showed lower accuracy of data because of the density of soy sauce, the method of sampling by weight was adopted as the proposed method. The total amount of outlier data was within acceptable limits for method-performance studies (< or = 22.2%). Lysine and ammonium sulfate recoveries for all laboratories were > or = 98% and > or = 99% respectively. The RSDr (repeatability relative standard deviation) values ranged from 0.4 to 1.3%, and the RSDR (reproducibility relative standard deviation) values were from 0.8 to 1.9%. HORRAT (RSDR/predicted RSDR) for the reproducibility showed 0.2 to 0.4, indicating acceptable precision of the method and excellent analytical performance.     

Squalene‐Derived Triterpene Polyethers from the Red Alga Laurencia omaezakiana

In our continuing search on halogenated metabolites from species of the red algal genus Laurencia, a novel squalene‐derived triterpene polyether, named omaezakianol ( 2 ), was isolated from Laurencia omaezakiana Masuda along with 15,16‐anhydrothyrsiferol ( 3 ). Their structures were determined by spectral and chemical methods.     

UV protection and singlet oxygen quenching activity of aloesaponarin I

The UV protection and singlet oxygen quenching of aloesaponarin I have been studied by means of laser spectroscopy. The excited-state intramolecular proton transfer that provides the UV protection takes place along only one of the molecule's two intramolecular hydrogen bonds, and this can be understood by considering the nodal pattern of the wave function. The functional groups participating in the excited-state intramolecular proton transfer also play important roles in the singlet oxygen quenching. Aloesaponarin I has a quenching rate constant larger than that of vitamin E and has a long duration of action due to its resistance to UV degradation and chemical attacks by singlet oxygen and free radicals.     

Single laser pulse induced aggregation of gold nanoparticles

Gold nanoparticles with an average diameter of 11 nm (Au(39000)) were prepared in an SDS aqueous solution. A 80-microm liquid droplet (microdroplet) of the solution was ejected into the atmosphere from a microdroplet nozzle. Structural changes of the gold nanoparticles in the microdroplet, after they were irradiated with a focused single-nanosecond laser pulse at the wavelength of 532 nm, were studied by transmission electron microscopy (TEM) and optical absorption spectroscopy. It was revealed that the gold nanoparticles are fragmented into small particles and then the small fragments aggregate with each other. The aggregation was found to be terminated 100 micros after the laser-pulse excitation.     

Wavelength-dependent fragmentation and clustering observed after femtosecond laser ablation of solid C60

We report here the resonance effect in femtosecond laser ablation of solid C60 by investigating wavelength and fluence dependence of product ion species. When the ablation laser wavelength is far from the molecular absorption band of C60, we observe both C60-2n+ fragment ions and C60+2n+ cluster ions as well as C60+ parent ion. Delayed ionization of C60 is not significant. When the ablation laser wavelength is near resonant with the molecular absorption, we observe C60+ and some amount of C60-2n+ fragment ions depending on the laser fluence. Delayed ionization of C60 is significant in this case, which indicates high internal energy of C60 molecule. From the observations, we confirm the strong coupling of femtosecond laser energy with C60 molecule when the molecular absorption is high at the ablation laser wavelength.