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We report photometric and spectroscopic observations of the eclipsing SU UMa-type dwarf nova ASASSN-18aan. We observed the 2018 superoutburst with 2.3 mag brightening and found the orbital period ($P_{\rm orb}$) to be 0.149454(3) d, or 3.59 hr. This is longward of the period gap, establishing ASASSN-18aan as one of a small number of long-$P_{\rm orb}$ SU UMa-type dwarf novae. The estimated mass ratio, ($q=M_2/M_1 = 0.278(1)$), is almost identical to the upper limit of tidal instability by the 3:1 resonance. From eclipses, we found that the accretion disk at the onset of the superoutburst may reach the 3:1 resonance radius, suggesting that the superoutburst of ASASSN-18aan results from the tidal instability. Considering the case of long-$P_{\rm orb}$ WZ Sge-type dwarf novae, we suggest that the tidal dissipation at the tidal truncation radius is enough to induce SU UMa-like behavior in relatively high-$q$ systems such as SU UMa-type dwarf novae, but that this is no longer effective in low-$q$ systems such as WZ Sge-type dwarf novae. The unusual nature of the system extends to the secondary star, for which we find a spectral type of G9, much earlier than typical for the orbital period, and a secondary mass $M_2$ of around 0.18 M$_{\odot}$, smaller than expected for the orbital period and the secondary's spectral type. We also see indications of enhanced sodium abundance in the secondary's spectrum. Anomalously hot secondaries are seen in a modest number of other CVs and related objects. These systems evidently underwent significant nuclear evolution before the onset of mass transfer. In the case of ASASSN-18aan, this apparently resulted in a mass ratio lower than typically found at the system's $P_{\rm orb}$, which may account for the occurrence of a superoutburst at this relatively long period., Comment: 17 pages, 14 figures, accepted for publication in PASJ

arXiv:2004.10508v1, et al., We report on photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9 mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the post-superoutburst stage showed Balmer, He I, and possible sodium doublet features. The mass ratio is derived as 0.0880(9) from the period of the superhump. During the third and fifth rebrightenings, growing superhumps and superoutbursts were observed, which have never been detected during a rebrightening phase among WZ Sge-type dwarf novae with multiple rebrightenings. To induce a superoutburst during the brightening phase, the accretion disk needs to have expanded beyond the 3 : 1 resonance radius of the system again after the main superoutburst. These peculiar phenomena can be explained by the enhanced viscosity and large radius of the accretion disk suggested by the higher luminosity and the presence of late-stage superhumps during the post-superoutburst stage, plus by more mass supply from the cool mass reservoir and/or from the secondary because of the enhanced mass transfer than those of other WZ Sge-type dwarf novae., N. Narita is supported by JSPS KAKENHI Grant Numbers JP18H01265 and JP18H05439, and JST PRESTO Grant Number JPMJPR1775. M. Tamura is supported by MEXT/JSPS KAKENHI Grant Nos. 18H05442, 15H02063, and 22000005. P. A. Dubovsky, T. Medulka, and I. Kudzej acknowledge support by NSF AST-1751874 and the Cottrell scholarship from the Research Corporation for Science Advancement and by the Slovak Research and Development Agency under the contract No. APVV-15-0458. A. Zubareva, A. Belinski, A. Dodin, M. Burlak, N. Ikonnikova, E. Mishin, and S. Potanin acknowledge the support from the Program of development of M.V. Lomonosov Moscow State University (Leading Scientific School “Physics of stars, relativistic objects and galaxies”). E. P. Pavlenko, O. I. Antonyuk, and Ju. V. Bbabina acknowledge support by the RSF grant 19-72-10063.

The glycosidic fraction from the dried roots of Panax notoginseng (Burk.) F.H.Chen exhibited an inhibitory effect on zoospore motility of Aphanomyces cochlioides . Further study on this fraction afforded fourteen dammarane-type saponins. Their structures were determined on the basis of spectroscopic and chemical methods. Eleven were known compounds, and the three new ones were 3- O -[β- d -glucopyranosyl (1→6)-β- d -glucopyranosyl]-20- O -β- d -glucopyranosyl 3β, 12β, 20 ( S )-trihydroxydammar-24-ene, 3- O -β- d -glucopyranosyl 20- O -[α- l -arabinopyranosyl (1→2)-β- d -glucopyranosyl] 3β, 12β, 20 ( S )-trihydroxydammar-24-ene and 6- O -β- d -glucopyranosyl 20- O -β- d -glucopyranosyl 3β, 6α, 12β, 20 ( S ), 25-pentahydroxydammar-23-ene, respectively. Each saponin displayed good inhibitory effects on zoospore motility.

A photo-sensitive amino acid analogue was introduced into an outer membrane lipoprotein, Pal, and then subjected to photo-crosslinking with the lipoprotein-specific ABC transporter LolCDE. Pal crosslinked to LolE but not LolC in vivo despite that both are structurally similar membrane subunits. LolCDE liganded with Pal containing the photo-sensitive amino acid analogue was isolated and subjected to in vitro photo-crosslinking. LolE was found to be the binding site for Pal. ATP binding to LolD decreased the LolE–Pal crosslinking by decreasing their hydrophobic interaction. ATP hydrolysis in the presence of LolA completely abolished the LolE–Pal crosslinking and, concomitantly, generated a new LolA–Pal crosslinked product. Structured summary of protein interactions LolE and Pal physically interact by cross-linking study ( View interaction ) LolE and Pal bind by cross-linking study ( View interaction ) Pal and Pal bind by cross-linking study ( View interaction ) Pal and LolA physically interact by competition binding ( View interaction )

In a survey of plant secondary metabolites regulating the behaviour of Aphanomyces cochlioides zoospores, we found that root extracts of Portulaca oleracea inhibited zoospore motility. Bioassay-directed fractionation of Portulaca constituents revealed that the inhibitory activity was dependent on the interaction of two chemically different factors. These were identified as a phenolic compound, N-trans-feruloyltyramine, which by itself was active as a zoospore stimulant, and an acidic compound, 1-linoleoyl-2-lysophosphatidic acid monomethyl ester, which had zoospore-repellent activity. When Chromosorb W AW particles coated with a mixture of these pure compounds were bioassayed in Petri dishes, the inhibitory effect on zoospore motility was identical with that caused by root tip or root extracts of P. oleracea. Inhibited zoospores rapidly settled to the bottom of the Petri dishes where they initially encysted, and then germinated within 1–2 h. This is the first report of factors which inhibit zoospore motility without killing or bursting the zoospores.