Self-Assembled Single-Walled Metal-Helical Nanotube (<b>M‑HN</b>): Creation of Efficient Supramolecular Catalysts for Asymmetric Reaction

Ever since the axial chiral catalysts were developed for asymmetric reactions with excellent chiral discrimination and high efficiencies, the interest in the supramolecular catalyst has also been extensively investigated. Here, with a hint from the typical molecular catalyst, we developed a series of metal-coordinated nanotube (M-helical nanotube, <b>M-HN</b>) catalysts for asymmetric reactions. The <b>M-HN</b> catalyst was fabricated on the basis of the self-assembly of an l-glutamic acid terminated bolaamphiphile, which formed a single-walled nanotube. On one hand, through the coordination of transition metal ions with the carboxylic acid groups on the nanotube surface, a wide variety of single-walled <b>M-HN</b> catalysts could be fabricated, in which the coordination sites could serve as the catalytic sites. On the other hand, using a slight amount of these catalysts, significant reactivity and enantioselectivity were realized for certain asymmetric reactions under mild conditions. Remarkably, <b>Bi­(III)-HN</b> could catalyze the asymmetric Mukaiyama aldol reaction with high enantioselectivity (up to 97% ee) in an aqueous system; <b>Cu­(II)-HN</b> catalyzed the asymmetric Diels–Alder reaction with up to 91% ee within 60 min. It was suggested that a synergetic effect of the aligned multicatalytic sites and stereochemical selectivity of the <b>M-HN</b> lead to an excellent catalytic performance. Through this work, we proposed a new concept of a single-walled nanotube as catalyst and showed the first example of nanotube catalysts presenting high reactivity and enantioselectivity that rivaled a chiral molecular catalyst

Identifying optimal reference genes for the normalization of microRNA expression in cucumber under viral stress

<div><p><i>Cucumber green mottle mosaic virus</i> (CGMMV) is an economically important pathogen and causes significant reduction of both yield and quality of cucumber (<i>Cucumis sativus</i>). Currently, there were no satisfied strategies for controlling the disease. A better understanding of microRNA (miRNA) expression related to the regulation of plant-virus interactions and virus resistance would be of great assistance when developing control strategies for CGMMV. However, accurate expression analysis is highly dependent on robust and reliable reference gene used as an internal control for normalization of miRNA expression. Most commonly used reference genes involved in CGMMV-infected cucumber are not universally expressed depending on tissue types and stages of plant development. It is therefore crucial to identify suitable reference genes in investigating the role of miRNA expression. In this study, seven reference genes, including <i>Actin</i>, <i>Tubulin</i>, <i>EF-1α</i>, <i>18S rRNA</i>, <i>Ubiquitin</i>, <i>GAPDH</i> and <i>Cyclophilin</i>, were evaluated for the most accurate results in analyses using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Gene expression was assayed on cucumber leaves, stems and roots that were collected at different days post inoculation with CGMMV. The expression data were analyzed using algorithms including delta-Ct, geNorm, NormFinder, and BestKeeper as well as the comparative tool RefFinder. The reference genes were subsequently validated using miR159. The results showed that <i>EF-1α</i> and <i>GAPDH</i> were the most reliable reference genes for normalizing miRNA expression in leaf, root and stem samples, while <i>Ubiquitin</i> and <i>EF-1α</i> were the most suitable combination overall.</p></div

RT-qPCR cycle threshold values of seven reference genes in cucumber leaf, stem and root samples at different time points post-inoculation with CGMMV.

<p>Error bars represent the mean of three technical replicates ± SD.</p

Most suitable combination of reference genes for normalizing expression in cucumber according to NormFinder analysis.

<p>Most suitable combination of reference genes for normalizing expression in cucumber according to NormFinder analysis.</p

Expression stability of seven reference genes in cucumber analyzed using the NormFinder algorithm.

<p>Expression stability of seven reference genes in cucumber analyzed using the NormFinder algorithm.</p

Expression profile of miR159 and validation of selected reference genes in different cucumber tissues infected with CGMMV.

<p>Error bars represent the mean of three technical replicates ± SD.</p

GeNorm data for 5 cucumber reference genes in cucumber leaf, stem and root samples at different time points post-inoculation with CGMMV.

<p>(A) to (D) Average expression stability values (M) of cucumber reference genes during stepwise exclusion of the least stable reference gene in different tissue samples. (A) leaf, (B) stem, (C) root, and (D) overall. (E) to (H) Optimal number of reference genes required for accurate normalization of expression based on pairwise variation (V_n/n+1) analysis of the normalization factors of the reference genes in different tissue samples. (E) leaf, (F) stem, (G) root, and (H) overall.</p

RefFinder ranking of seven reference genes in cucumber in descending order of expression stability from 1 to 7.

<p>RefFinder ranking of seven reference genes in cucumber in descending order of expression stability from 1 to 7.</p

Expression stability of five reference genes in cucumber analyzed using the BestKeeper algorithm.

<p>Expression stability of five reference genes in cucumber analyzed using the BestKeeper algorithm.</p

Additional file 2: of Comparative transcriptome reveal the potential adaptive evolutionary genes in Andrias davidianus

Table S1. Orthologs gene under positive selection among species. (DOCX 18 kb