Protein Phosphatase 1 (PP1) Is a Post-Translational Regulator of the Mammalian Circadian Clock

Circadian clocks coordinate the timing of important biological processes. Interconnected transcriptional and post-translational feedback loops based on a set of clock genes generate and maintain these rhythms with a period of about 24 hours. Many clock proteins undergo circadian cycles of post-translational modifications. Among these modifications, protein phosphorylation plays an important role in regulating activity, stability and intracellular localization of clock components. Several protein kinases were characterized as regulators of the circadian clock. However, the function of protein phosphatases, which balance phosphorylation events, in the mammalian clock mechanism is less well understood. Here, we identify protein phosphatase 1 (PP1) as regulator of period and light-induced resetting of the mammalian circadian clock. Down-regulation of PP1 activity in cells by RNA interference and in vivo by expression of a specific inhibitor in the brain of mice tended to lengthen circadian period. Moreover, reduction of PP1 activity in the brain altered light-mediated clock resetting behavior in mice, enhancing the phase shifts in either direction. At the molecular level, diminished PP1 activity increased nuclear accumulation of the clock component PER2 in neurons. Hence, PP1, may reduce PER2 phosphorylation thereby influencing nuclear localization of this protein. This may at least partially influence period and phase shifting properties of the mammalian circadian clock

Heteropoly compounds - From proton conductors to biomedical agents

Heteropoly compounds (HPCs) have been a matter of interest in basic and applied science for more than a century. From their first synthesis, many advances have been made to promote the use of HPCs in different ways in science and technology. The aim of this article is to review the main structural characteristics of heteropoly compounds of the Keggin type (12-tungstophosphoric, 12-molybdophosphoric, 12-tungstosilicic acids; alkaline and alkaline earth salts of 12-tungstophosphoric acid and gels doped with HPCs) to understand and explain their different activities, such as high proton conductivity, and catalytic, biochemical and biomedical activities. (c) 2005 Elsevier B.V. All rights reserved.12th International Conference on Solid State Proton Conductors (SSPC-12), Aug 15-19, 2004, Uppsala Univ, Angstrom Lab, Uppsala, Swede

A study of the IR spectra of the copigments of malvin chloride with organic acids

The infrared spectra of the copigments of malvin with several organic acids: caffeic, ferulic, sinapic, chlorogenic, and tannic, were analyzed in order to elucidate the bonding of the molecules in the copigments. It was established that copigmentation is realized through hydrogen bonding between malvin molecules and the acids under study. The infrared spectra reveal that two groups of hydrogen bonds are formed, which include interactions of different molecular structures: hydroxy groups (bands around 3500 cm1) and oxonium ions of the molecules (bands below 3000 cm1). The formed hydrogen bonds were found to be of different strengths. The strengths of the hydrogen bonds were tentatively correlated with thermodynamic properties of the corresponding copigmentation reactions

Conductivity of grains and grain boundaries in polycrystalline heteropoly acid salts

In our previous work we investigated the conductivity and dielectric relaxation phenomena in heteropoly acids and their salts. In this work, we have studied the conductivity of grains and grain boundaries in compressed powders of 12-tungstophosphoric acid (WPA) salts with univalent and bivalent ions. The method of impedance spectroscopy has been employed in the frequency range from 5 Hz to 500 kHz. We obtained grains and grain boundaries conductivities as well as corresponding activation energies. Grain conductivity in all investigated salts is always higher than the grain boundary conductivity.Current Research in Advanced Materials and Processes, 6th Conference of the Yugoslav-Materials-Research-Society, Sep 13-17, 2004, Herceg Novi, Montenegr

Structure and proton conductivity of 12-tungstophosphoric acid doped silica

Sol-gel syntheses offer a wide range of possibilities for introduction of materials with specific properties (electronic, optic and ion-conductive, etc.) into optically clear matrices. Preparation of silica gel bulk, containing 12-tungstophosphoric acid (WPA) in mesopores, as well as its structural and conduction characteristics are reported. Characteristics of the obtained doped gels depend on the gel preparation, gelation process and the WPA content. According to the obtained results, especially for the high conductivity (sigma similar to 0.1 S/cm), WPA doped silica gel is a promising material for solid electrolytes.VIII International Conference on Solid State Protonic Conductors, Aug 18-23, 1996, Gol, Norwa

Dielectric properties of metal salts of heteropolyacid hydrates

Heteropolyacids hydrates as superionic conductors have been intensely investigated during the last fifteen years. By using various experimental techniques such as IR and Raman spectroscopy, neutron scattering, impedance measurements, X-ray diffraction and others, informations have been obtained on the properties of protonic entities and conductivity mechanisms. The salts of heteropolyacids have been less investigated although there is a steady growth of activities in this field too. In this work the results of permittivity measurements are presented on copper and calcium salts of 12-tungstophosphoric acid hydrates (CuHPW12O40. 15H(2)O and CaHPW12O40. 13H(2)O). Measurements have been done in the region of microwaves, at room temperature and in a room ambient. The aim of this work was to study the influence of copper and calcium ions on dielectric relaxation processes in these salts. Dielectric relaxations have been found for both salts. Contributions of fast reorientations of H2O molecules and oxonium ions (H3O+) to these relaxations are discussed as well as, their influence on dynamic conductivity