Supramolecular hydrogels containing inorganic salts and acids

l-Lysine-based hydrogelators can form supramolecular hydrogels over a wide pH range and contain inorganic salts and acids, especially, 3 forms hydrogels containing 1 M HCl and H₂SO₄ at 1 g/L.     

New oxindole alkaloids and iridoid from Carolina jasmine (Gelsemium sempervirens Ait. f.)

Three new gelsedine-type oxindole alkaloids, GS-1, GS-2, and GS-3, and one new iridoid, GSIR-1, were isolated from the stems and leaves of cultivated Carolina jasmine (Gelsemium sempervirens AIT. f.) and their structures were determined by spectroscopic analysis.     

Photodissociation of CO from [Ru3(mu3-O)(mu-OOCCH3)6(CO)L2] in acetonitrile, where L = pyridine, 4-cyanopyridine and methanol

Photodissociation of CO from oxo-centered trinuclear ruthenium clusters [Ru3(mu3-O)(mu-OOCCH3)6(CO)L2] (L = pyridine (py): 1; 4-cyanopyridine (cpy): 2; methanol: 3) dissolved in organic solvents has been examined. Upon photolysis (> or = 290 nm, a 450-W Xe lamp), an absorption peak at 585 nm observed for 1 in CH3CN decreases its intensity and a new absorption band appears and grows at 896 nm. This spectral change, presenting isosbestic points, corresponds to photosubstitution of CO in 1 to form [Ru3(mu3-O)(mu-OOCCH3)6(CH3CN)(py)2] 4. Photoexcitation of carbonyl complexes 2 and 3 in CH3CN also affords the corresponding CH3CN-coordinated complexes [Ru3(mu3-O)(mu-OOCCH3)6(CH3CN)(cpy)2] 6 and [Ru3(mu3-O)(mu-OOCCH3)6(CH3CN)3] 7, respectively. The photosubstitution reactions (excitation wavelength, > or = 290 nm) are well described by the first-order kinetics: k = 7.3 x 10(-4) s(-1) for 1, 4.9 x 10(-4) s(-1) for 2 and 5.1 x 10(-4) s(-1) for 3 (298 K). In the presence of a 100-fold excess of py, photolysis of 1 yields a tris(py) complex [Ru3(mu3-O)(mu-OOCCH3)6(py)3] 5 via photochemical loss of CO followed by coordination of py. The overall reaction (photochemical and thermal) is also confirmed by 1H NMR spectroscopy. The dissociative character of the photosubstitution is supported by negligible effects of the concentration of the entering pyridine molecule, the nature of solvents and the type of terminal monodentate ligands (other than CO) attached to the cluster. Quantum yield measurements with varied excitation wavelengths have shown that absorption bands located in the UV region (< 400 nm) play a principal role in photosubstitution, whereas an absorption band in the visible region (centered at approximately 580 nm), ascribed to an "intracluster" charge transfer, is not at all responsible for photosubstitution.     

In situ observation of molecular diffusion in solid supports using two-photon fluorescence microscopy

We demonstrate that two-photon fluorescence microscopy is a useful tool for monitoring the diffusion of molecules through polymeric solid supports. As a proof of principle, TentaGel beads were bound to a cover slip, and diffusion of Rhodamine 6G through single beads was observed in real time. Diffusion experiments performed in 40 different beads indicate that there is a considerable degree of heterogeneity in diffusion rates from bead to bead.     

Determination of radionuclides in human and environmental samples from the criticality accident in Tokai-mura, Japan

For three heavily exposed workers in the Tokai-mura criticality accident, the levels of ²⁴Na, ⁴²K and ⁸²Br were measured in blood, urine, vomit and hair. ²⁴Na showed the highest activity and was found to have a specific activity of 8.24·10⁴, 4.34·10⁴ and 1.23·10⁴ Bq ²⁴Na per g Na in blood of the three exposed workers. Based on these data the individual neutron fluences were calculated. Radionuclides were also measured in environmental samples from the JCO campus. The fission products ¹³¹I, ¹³³I, ¹⁴⁰Ba-¹⁴⁰La and ¹³⁷Cs were determined in plant samples and the activation products ⁵⁹Fe, ⁴⁶Sc, ⁶⁰Co and ¹⁵²Eu were identified in soil samples. ²³⁵U/²³⁸U ratios in soil and plant samples were measured by ICP-MS. This revised version was published online in July 2006 with corrections to the Cover Date.     

Swelled plastics in supercritical CO2 as media for stabilization of metal nanoparticles and for catalytic hydrogenation

Swelled plastics in supercritical carbon dioxide provide unique environments for stabilizing palladium and rhodium nanoparticles and for catalytic hydrogenation. Complete hydrogenation of benzene to cyclohexane can be achieved in 10 minutes using the plastic stabilized Rh nanoparticles at 50 degrees C in supercritical CO(2). High efficiency, reusability, and rapid separation of products are some advantages of the plastic stabilized metal nanoparticles for catalytic hydrogenation in supercritical CO(2).     

FUNCTIONAL ROLE OF CALCIUM IN PHOTORECEPTOR CELLS

Abstract— Ca-uptake by disc membranes prepared from frog rod photoreceptor outer segments was examined. Ca-uptake study revealed two affinity sites which were saturated with 10–⁵ M and 10–³ M of ATP. When disc membranes in 20 m M Tris-HCl buffer (pH 7.5) were stored at -20°C for 6 h, more than 95% of Ca-uptake activity was lost. Ca-uptake activity was, however, preserved if the disc membrane suspension was mixed with 1–10m M ATP and stored at -20°C. Furthermore the reactivation of Ca-uptake was observed if disc membranes, which had lost Ca-uptake ability by storing at 4°C for 3 h, were mixed with 10 m M ATP and then frozen at -20°C for 5 h or 28 h (ATP-induced ATP-dependent Ca-uptake). When the contents of ATP bound to disc membranes were measured during a brief aging at 37°C, the decrement of bound ATP content was correlated well with the decreasing of Ca-uptake activity. Carbonylcyanide m -chlorophenylhydrazone (CCCP), a conductor of protons, inhibited Ca-uptake activity and half maximal inhibition was achieved at 2 × 10–⁸ M. When 10–⁶ M of CCCP was added to the ⁴⁵Ca-accumulated disc membranes, rapid release of ⁴⁵Ca from the disc membranes was observed. These results suggest that ATP may play a role in the Ca-pump regulation in disc membranes and a [H⁺] gradient across disc membrane may be linked to Ca-uptake mechanism.     

New iridoids from Gelsemium species

Four new iridoids structurally related to gelsemide (5) were isolated from two Loganiaceous plants, Gelsemium elegans and G. rankinii. Among them, GEIR-1 (1) has a novel tetracyclic caged structure.     

Thermally stable and photoreactive polylactides by the terminal conjugation of bio-based caffeic acid

Caffeic acid terminally conjugated with polylactide showed high thermal stability and photoreactivity, and may be useful as a functional polylactide in the environmental and medical fields.