Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged).Comment: 239 pages, 225 figures, PASJ accepte

Exploring dynamics of molybdate in living animal cells by a genetically encoded FRET nanosensor.

Molybdenum (Mo) is an essential trace element for almost all living organisms including animals. Mo is used as a catalytic center of molybdo-enzymes for oxidation/reduction reactions of carbon, nitrogen, and sulfur metabolism. Whilst living cells are known to import inorganic molybdate oxyanion from the surrounding environment, the in vivo dynamics of cytosolic molybdate remain poorly understood as no appropriate indicator is available for this trace anion. We here describe a genetically encoded Förester-resonance-energy-transfer (FRET)-based nanosensor composed of CFP, YFP and the bacterial molybdate-sensor protein ModE. The nanosensor MolyProbe containing an optimized peptide-linker responded to nanomolar-range molybdate selectively, and increased YFP:CFP fluorescence intensity ratio by up to 109%. By introduction of the nanosensor, we have been able to successfully demonstrate the real-time dynamics of molybdate in living animal cells. Furthermore, time course analyses of the dynamics suggest that novel oxalate-sensitive- and sulfate-resistant- transporter(s) uptake molybdate in a model culture cell

Effect of over-expression and knockdown of <i>Hs</i>MoT2/MFSD5 in molybdate uptake rate. A

<p>, Time course of R_F530:F480 in control cells (for Panel B). HEK-293T was co-transfected with MolyProbe and mock vector by the polyethyleneimine method. Fluorescence was measured after addition of molybdate, and R_F530:F480 calculated. <b>B</b>, Time course of <i>Hs</i>MoT2/MFSD5 over-expressing cells. mRNA level of <i>Hs</i>MoT2/MFSD5 was about sixty-fold compared to the control cell. <b>C</b>, Time course of R_F530:F480 in control cells (for Panel D) transfected with MolyProbe by X-tremeGENE siRNA reagent. <b>D</b>, Time course of R_F530:F480 in <i>Hs</i>MoT2/MFSD5 knockdown cells. mRNA level of <i>Hs</i>MoT2/MFSD5 was 11–35% compared to the control cell. Concentrations of molybdate in working medium are follows: 0 µM (closed circle), 0.1 µM (cross), 0.3 µM (closed triangle), 1 µM (open triangle), 3 µM (closed diamond), 10 µM (open diamond), 30 µM (closed square), 100 µM (open square). Averages and SDs from triplicate samples are shown. n = 3.</p

Sensitivity and specificity of MolyProbe. A

<p>, Titration curve of MolyProbe to molybdate. Emission spectrum was measured as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058175#pone-0058175-g001" target="_blank">Figure 1</a>. Emission intensity ratio (F530: F475) was calculated and plotted against molybdate concentration. The plot was fitted by the Hill equation. <b>B</b>, Titration curves for similar oxyanions. <b>C</b>, Inhibitory effect of chloride. Titration curves for molybdate were determined in the presence of 1–100 mM KCl. Apparent <i>K</i>_0.5 values for molybdate were calculated and plotted against concentrations of potassium chloride. <b>D</b>, Inhibitory effect of bicarbonate. <b>E</b>, Inhibitory effect of MolyProbe. Titration curves were determined at a concentration of 0.5–200 nM MolyProbe. Average data were obtained by triplicate assays. The SDs were small (<2% for A, B and <5% for C–E).</p

FRET-based genetically encoded nanosensor for molybdate. A

<p>, Primary structure of MolyProbe. CFP (Cerulean), two molybdate binding domains (MoBD) and YFP (cp157-Venus) are connected by optimized peptide linkers. MoBDs are from <i>E.coli</i> ModE factor. T272A/T444A is a loss-of-function mutant. <b>B</b>, Schematic representation of molybdate binding between two MoBDs, which increase FRET efficiency. <b>C</b>, Spectral property of MolyProbe <i>in vitro</i>. The emission spectrum of recombinant protein (20 nM) was measured at λ_Ex 430 nm (λ_max for CFP), with or without 10 µM molybdate. <b>D</b>, Emission spectral property of the T272A/T444A double mutant.</p

Real time imaging of molybdate level in living animal cells. A

<p>, Time course of R_F530:F475 in bulk HEK-293T cells transfected with MolyProbe after exposure to 1 mM molybdate at 37°C. <b>B</b>, Time course of R_F530:F475 in the bulk cells treated with 1 mM molybdate at 22°C. Averages and SDs from triplicate samples are shown. <b>C</b>, Confocal CFP(F475) and YFP(F535) images of the cells before and after treatment with 1 mM molybdate. <b>D</b>, Variation in expression levels of MolyProbe. A density image of MolyProbe (green) calculated from a pair of CFP and YFP image was merged with a transmission image (grey). Low-level expression cells (1), middle-level cells (2) and high-level cells (3) showed a different time course of the ratio change (Figure E). <b>E</b>, A series of ratio images of the cells accumulating molybdate. Ratio (F535:F475) images were calculated from pairs of CFP and YFP images taken every 15 sec, and the ratios are presented in pseudo-color. Intracellular molybdate increased by addition of 1 mM molybdate to the medium. Velocity of the molybdate increment in pseudopod was fast compared to the cell body (arrow), whereas nuclear space was slow (arrowhead).</p