C. M. Zhang

The correlations between the twin kHz quasi-periodic oscillation frequencies of low-mass X-ray binaries

We analyzed the recently published kHz QPO data in the neutron star low-mass X-ray binaries (LMXBs), in order to investigate the different correlations of the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z sources and in the less luminous Atoll sources. We find that a power-law relation

Integrated omics study delineates the dynamics of lipid droplets in Rhodococcus opacus PD630

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Dynamics of the Lipid Droplet Proteome of the Oleaginous Yeast Rhodosporidium toruloides

between the upper and the lower kHz QPOs with different indices:

Turbulent convection and pulsation stability of stars – II. Theoretical instability strip for δ Scuti and γ Doradus stars

b\simeq

Microorganism lipid droplets and biofuel development

1.5 for the Atoll source 4U 1728-34 and

Bacterial lipid droplets bind to DNA via an intermediary protein that enhances survival under stress

b\simeq

Turbulent convection and pulsation stability of stars - I. Basic equations for calculations of stellar structure and oscillations

1.9 for the Z source Sco X-1. The implications of our results for the theoretical models for kHz QPOs are discussed.

Does Submillisecond Pulsar XTE J1739−285 Contain a Weak Magnetic Neutron Star or Quark Star?

Rhodococcus opacus strain PD630 (R. opacus PD630), is an oleaginous bacterium, and also is one of few prokaryotic organisms that contain lipid droplets (LDs). LD is an important organelle for lipid storage but also intercellular communication regarding energy metabolism, and yet is a poorly understood cellular organelle. To understand the dynamics of LD using a simple model organism, we conducted a series of comprehensive omics studies of R. opacus PD630 including complete genome, transcriptome and proteome analysis. The genome of R. opacus PD630 encodes 8947 genes that are significantly enriched in the lipid transport, synthesis and metabolic, indicating a super ability of carbon source biosynthesis and catabolism. The comparative transcriptome analysis from three culture conditions revealed the landscape of gene-altered expressions responsible for lipid accumulation. The LD proteomes further identified the proteins that mediate lipid synthesis, storage and other biological functions. Integrating these three omics uncovered 177 proteins that may be involved in lipid metabolism and LD dynamics. A LD structure-like protein LPD06283 was further verified to affect the LD morphology. Our omics studies provide not only a first integrated omics study of prokaryotic LD organelle, but also a systematic platform for facilitating further prokaryotic LD research and biofuel development.

Tracing Evolutionary Footprints to Identify Novel Gene Functional Linkages

ABSTRACT Lipid droplets (LDs) are ubiquitous organelles that serve as a neutral lipid reservoir and a hub for lipid metabolism. Manipulating LD formation, evolution, and mobilization in oleaginous species may lead to the production of fatty acid-derived biofuels and chemicals. However, key factors regulating LD dynamics remain poorly characterized. Here we purified the LDs and identified LD-associated proteins from cells of the lipid-producing yeast Rhodosporidium toruloides cultured under nutrient-rich, nitrogen-limited, and phosphorus-limited conditions. The LD proteome consisted of 226 proteins, many of which are involved in lipid metabolism and LD formation and evolution. Further analysis of our previous comparative transcriptome and proteome data sets indicated that the transcription level of 85 genes and protein abundance of 77 proteins changed under nutrient-limited conditions. Such changes were highly relevant to lipid accumulation and partially confirmed by reverse transcription-quantitative PCR. We demonstrated that the major LD structure protein Ldp1 is an LD marker protein being upregulated in lipid-rich cells. When overexpressed in Saccharomyces cerevisiae, Ldp1 localized on the LD surface and facilitated giant LD formation, suggesting that Ldp1 plays an important role in controlling LD dynamics. Our results significantly advance the understanding of the molecular basis of lipid overproduction and storage in oleaginous yeasts and will be valuable for the development of superior lipid producers.

Turbulent convection and pulsation stability of stars – III. Non-adiabatic oscillations of red giants

By using a non-local and time-dependent convection theory, we have calculated radial and low-degree non-radial oscillations for stellar evolutionary models with M = 1.4-3.0 M-circle dot. The results of our study predict theoretical instability strips for delta Scuti and gamma Doradus stars, which overlap with each other. The strip of gamma Doradus is slightly redder in colour than that of delta Scuti. We have paid great attention to the excitation and stabilization mechanisms for these two types of oscillations, and we conclude that radiative K mechanism plays a major role in the excitation of warm delta Scuti and gamma Doradus stars, while the coupling between convection and oscillations is responsible for excitation and stabilization in cool stars. Generally speaking, turbulent pressure is an excitation of oscillations, especially in cool delta Scuti and gamma Doradus stars and all cool Cepheid- and Mira-like stars. Turbulent thermal convection, on the other hand, is a damping mechanism against oscillations that actually plays the major role in giving rise to the red edge of the instability strip. Our study shows that oscillations of delta Scuti and gamma Doradus stars are both due to the combination of kappa mechanism and the coupling between convection and oscillations, and they belong to the same class of variables at the low-luminosity part of the Cepheid instability strip. Within the delta Scuti-gamma Doradus instability strip, most of the pulsating variables are very likely hybrids that are excited in both p and g modes.