GC pairs are generally more stable than AT pairs; GC-rich genomes were proposed to be more adapted to high temperatures than AT-rich genomes. Previous studies consistently showed positive ...correlations between growth temperature and the GC contents of structural RNA genes. However, for the whole genome sequences and the silent sites of the codons in protein-coding genes, the relationship between GC content and growth temperature is in a long-lasting debate.
With a dataset much larger than previous studies (681 bacteria and 155 archaea with completely assembled genomes), our phylogenetic comparative analyses showed positive correlations between optimal growth temperature (Topt) and GC content both in bacterial and archaeal structural RNA genes and in bacterial whole genome sequences, chromosomal sequences, plasmid sequences, core genes, and accessory genes. However, in the 155 archaea, we did not observe a significant positive correlation of Topt with whole-genome GC content (GC
) or GC content at four-fold degenerate sites. We randomly drew 155 samples from the 681 bacteria for 1000 rounds. In most cases (> 95%), the positive correlations between Topt and genomic GC contents became statistically nonsignificant (P > 0.05). This result suggested that the small sample sizes might account for the lack of positive correlations between growth temperature and genomic GC content in the 155 archaea and the bacterial samples of previous studies. Comparing the GC content among four categories (psychrophiles/psychrotrophiles, mesophiles, thermophiles, and hyperthermophiles) also revealed a positive correlation between GC
and growth temperature in bacteria. By including the GC
of incompletely assembled genomes, we expanded the sample size of archaea to 303. Positive correlations between GC
and Topt appear especially after excluding the halophilic archaea whose GC contents might be strongly shaped by intense UV radiation.
This study explains the previous contradictory observations and ends a long debate. Prokaryotes growing in high temperatures have higher GC contents. Thermal adaptation is one possible explanation for the positive association. Meanwhile, we propose that the elevated efficiency of DNA repair in response to heat mutagenesis might have the by-product of increasing GC content like that happens in intracellular symbionts and marine bacterioplankton.
With tens of thousands of plant species on earth, we are endowed with an enormous wealth of medicinal remedies from Mother Nature. Natural products and their derivatives represent more than 50% of ...all the drugs in modern therapeutics. Because of the low success rate and huge capital investment need, the research and development of conventional drugs are very costly and difficult. Over the past few decades, researchers have focused on drug discovery from herbal medicines or botanical sources, an important group of complementary and alternative medicine (CAM) therapy. With a long history of herbal usage for the clinical management of a variety of diseases in indigenous cultures, the success rate of developing a new drug from herbal medicinal preparations should, in theory, be higher than that from chemical synthesis. While the endeavor for drug discovery from herbal medicines is “experience driven,” the search for a therapeutically useful synthetic drug, like “looking for a needle in a haystack,” is a daunting task. In this paper, we first illustrated various approaches of drug discovery from herbal medicines. Typical examples of successful drug discovery from botanical sources were given. In addition, problems in drug discovery from herbal medicines were described and possible solutions were proposed. The prospect of drug discovery from herbal medicines in the postgenomic era was made with the provision of future directions in this area of drug development.
Abstract
The photometric and spectroscopic investigations of ten contact binaries were presented for the first time. It is discovered that the mass ratios of all the ten targets are smaller than ...0.15, they are extremely low mass ratio contact binaries. Seven of them are deep contact binaries, two are medium contact binaries, while only one is a shallow contact system. Five of them show the O’Connell effect, and a dark spot on one of the two components can lead to a good fit of the asymmetric light curves. The orbital period studies of the ten binaries reveal that they all exhibit long-term period changes, six of them are increasing, while the others are shrinking. The LAMOST spectra were analyzed by the spectral subtraction method, and all the ten targets exhibit excess emissions in the H
α
line, indicating chromospheric activity. The evolutionary states of the two components of the ten binaries were studied, and it is found that their evolutionary states are identical to those of the other contact binaries. Based on the study of the relation between orbital angular momentum and total mass, we discovered the ten systems may be at the late evolutionary stage of a contact binary. The initial masses of the two components and the ages of them were obtained. By calculating the instability parameters, we found that the ten contact binaries are relatively stable at present.
Carbon fiber (CF) is a flexible shielding material with excellent electrical conductivity, thermal stability and mechanical properties, which is crucial to solve electromagnetic pollution problems. ...However, its application in green electromagnetic interference (EMI) shielding is hampered due to high secondary reflection. Herein, we proposed a method to selectively grow CNT cluster arrays on the CF surface for tunable green EMI shielding and microwave absorbing. The density of CNT cluster arrays can be manipulated by controlling of CF surface functional groups in the preparation route of metal-organic framework derived Co-doped CNTs. The CF/CNTs cluster array composites exhibit excellent electromagnetic wave absorbing performance, with an effective absorption bandwidth of 4.4 GHz with a matching thickness of 1.38 mm, which can be extended to full frequency band from 2 to 18 GHz through metastructure design. The green EM shielding index is greater than 12 in the whole frequency range from 2 to 18 GHz, with the maximum value up to 351. The strategy developed here provides a valuable guide for the preparation of electromagnetic functional materials with multilevel hierarchical structure.
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•A novel method to selectively grow CNT cluster arrays on CF surface is proposed.•The CF/CNT cluster arrays exhibits an ultrathin absorption with EAB of 4.4 GHz.•High-efficiency green EMI shielding is realized with gs > 12 covering full frequency band.
An ingenious strategy with the integration of a zwitterionic peptide into a two-photoelectrode system was reported to construct an advanced photoelectrochemical immunosensing platform. The strategy ...has endowed the platform with both excellent photoelectric properties and an antifouling ability, and was capable of accurate and sensitive detection of target biomarkers in biological specimens.
Taking the maximum fluorescence of an identical fluorophore as a reference, a DNAzyme-based normalized strategy is developed to unify the output signals under external interferences. This makes it ...possible to directly quantify endogenous zinc in living cells by
fluorescence imaging, implying promising potential in fundamental study and early disease diagnosis.
Broadband absorption is urgently desirable for microwave stealth or photothermal conversion, but is a significant challenge in thin layer applications. Impedance mismatch and undesired dielectric ...relaxation are the main obstacles to realizing simultaneous resonant absorption at multiple frequency bands. In this perspective, the key issues in broadband absorption are briefly reviewed, which must be addressed by the community to enable microwave absorption promoting and widening. Then, impedance matching coefficient used to identify microwave absorbing ability is highlighted. Finally, an ideal model of dielectric dispersion for carbon-based materials is proposed to be used to design broadband absorbing materials, after deducing the inner nature of the typical quarter-wave resonance absorption existing in absorbers.
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For SERS analysis in living cells, the inevitable desorption of Raman molecule on the substrate surface is a key challenge. To ensure high stability, SERS systems with Raman molecules protected ...inside the core–Raman molecule–shell (C–M–S) structures have been designed, but at the expense of sacrificed sensing performances. Here a shell-switchable SERS blocking strategy is developed for the reliable SERS analysis in living cells, relying on the shell blockers to regulate the SERS sensing signal without affecting the internal Raman molecules. After several C–M–S structures were investigated, the SERS blocking mechanism confirmed that thick shells (Au, Ag, ZnO, and MnO2) can cause a significant reduction in the internal SERS signal by obstructing the penetration of the laser or signal. The CAu–Mpy–SAu–SMnO2 nanoprobe is designed for the ratiometric SERS sensing in living cells, which retains sensing performances even though the Raman molecule is protected inside the nanostructure. This SERS strategy makes the turn-on sensing achievable in living cells with the MnO2 shell as a signal switch and a Raman reference. Additionally, it allows for accurate monitoring of the degradation of MnO2 carriers in living cells, even without fluorescent labels.
In recent years, increasing numbers of people have been choosing herbal medicines or products to improve their health conditions, either alone or in combination with others. Herbs are staging a ...comeback and herbal “renaissance” occurs all over the world. According to the World Health Organization, 75% of the world’s populations are using herbs for basic healthcare needs. Since the dawn of mankind, in fact, the use of herbs/plants has offered an effective medicine for the treatment of illnesses. Moreover, many conventional/pharmaceutical drugs are derived directly from both nature and traditional remedies distributed around the world. Up to now, the practice of herbal medicine entails the use of more than 53,000 species, and a number of these are facing the threat of extinction due to overexploitation. This paper aims to provide a review of the history and status quo of Chinese, Indian, and Arabic herbal medicines in terms of their significant contribution to the health promotion in present-day over-populated and aging societies. Attention will be focused on the depletion of plant resources on earth in meeting the increasing demand for herbs.
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