The comparative analysis of prebiological evolution models

Several models of prebiological systems are described and analyzed. The following models are characterized: a quasispecies model, a hypercycle model, a syser model (the term "syser" is an abbreviation of SYstem of SElf-Reproduction), a stochastic corrector model, a model of the origin of a primordial genome through spontaneous symmetry breaking. The quasispecies model analyzes the Darwinian evolution of information chains; this evolution is similar to the evolution of RNA molecules. Rather general estimates of the speed and efficiency of evolutionary processes can be obtained in the framework of the quasispecies model. We briefly describe the method for obtaining these estimates and the corresponding results. The hypercycle model considers the interaction of RNA chains and enzymes. The syser model characterizes a rather general scheme of the self-reproducing system, which is similar to the self-reproducing systems of biological cells. Syser includes a polynucleotide sequence, a replication enzyme, a translation enzyme, and other enzymes; these macromolecules are located inside the protocell. The stochastic corrector model describes the process of using a relatively small number of molecules of competing and cooperating replicators in protocells. The model of the origin of a primordial genome through spontaneous symmetry breaking characterizes an interesting and important process of the appearance of genotypes in protocells. This model was proposed and investigated by Takeuchi, Hogeweg, and Kaneko in 2017; we call it further “the THK model.” The current article characterizes and compares all these models.     

Colorimetric determination of thrombin by exploiting a triple enzyme-mimetic activity and dual-aptamer strategy

The article describes a colorimetric assay for the determination of thrombin. It is based on the application of a triple enzyme-mimetic activity and a dual aptamer binding strategy. The triple signal amplification relies on oxidation of the chromogenic enzyme substrate 3,3,5,5-tetramethylbenzidine (TMB) that is catalyzed by composites consisting of graphene oxide (GO), gold/platinum nanoparticles (AuPtNP), and aptamer (Apt15), a G-quadruplex/hemin conjugate. The dual-aptamer target binding strategy is based on the fact that thrombin has two active sites to be recognized by its aptamers (Apt15 and Apt29). Magnetic beads (MBs) were modified with Apt29 (Apt29-MB) and then are bound by the GO-AuPtNP-Apt15/G-quadruplex/hemin composites. In the presence of thrombin, Apt29-MB and the GO-AuPtNP-Apt15/G-quadruplex/hemin composites form a sandwich-like superstructure. Thus, the absorbance increases due to the formation of TMB oxide produced by catalysis of the composites. Under optimized conditions, the absorbance at 450 nm increases linearly in the 0.30 to 100 nM thrombin concentration range, and the limit of detection is 0.15 nM. The method is simple, rapid, and does not require complicated instrumentation. Bovine serum albumin, human serum albumin and other proteins were found not to interfere.

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Graphical abstract Schematic presentation of the photometric thrombin assay based on a triple enzyme-mimetic activity of combined nanomaterials (consisting of GO, AuPtNPs and the G-quadruplex/hemin DNAzyme) and two aptamers TMB: 3,3,5,5-tetramethylbenzidine, TMB_ox: 3,3,5,5-tetramethylbenzidine oxide, AuPtNP: gold/platinum nanoparticles).

     

一维p-Laplacian方程奇异边值问题的正解

本文讨论了一维p-Laplacian方程奇异边值问题的正解的存在性,其中函数f(t,x)可能在t=0,1都有奇点     

一类Banach空间中的分析性质及反例

本文对具有Schauder基的无穷维Banach空间上的映射定义偏导数,并讨论f的可徽性与偏导数存在并连续的关系;同时,本文还时论象所在空间为具有Schauder基的空间时,映射f与坐标映射f_i在可微性、连续性方面的关系.     

The structure of the thermal explosion limit with variable pre-exponential factor

An approximate critical explosion parameter, which separates the slow and explosive reactions is determined with respect to the initial data, using the asymptotic technique to analyze a one step reaction mechanism with temperature dependent pre-exponential factor. We obtained and analysed the effect of the variable pre-exponential factor on the critical temperature, critical parameter for thermal explosion and the first order approximation of the slow curve. By introducing a new coordinate and using the Method of Invariant Manifold (MIM), we obtained corrections on the critical temperature. The results obtained are not only general; they also reveal some salient properties of the system hitherto unknown.     

天登烟挥发性香气成分的聚类分析

为更为系统的了解天登烟的品质特点,采用同时蒸馏萃取-气相色谱/质谱法分析了烟叶样品中挥发性香气成分,并结合DSP软件对18个烟叶样品中13个成分峰按欧式距离类平均法进行了聚类分析。结果表明,各天登烟样品可以有效地聚为一类,特别是2003年的样品差异非常小,进一步说明,天登烟自身的香气特征风格突出,在烟草主要特征香气成分含量与组成方面同国产香料烟与烤烟较为接近,而与白肋烟、晒黄烟之间的差异均较大。     

A simplified and reliable LC–tandem mass spectrometry method for determination of ulipristal acetate in human plasma and its application to a pharmacokinetic study in healthy Chinese volunteers

In this study, a simplified, sensitive and reliable LC–tandem mass spectrometry method was established and validated for the quantification of ulipristal acetate (UPA) in human plasma and for the investigation of pharmacokinetic profile of UPA following a single oral administration of ella (UPA 30-mg tablet) in healthy Chinese volunteers. Plasma samples were analyzed after being processed by protein precipitation with methanol. Chromatographic separation was performed on a Kinetex EVO C₁₈ column (2.1 × 50 mm, 2.6 μm) using gradient elution with a mobile phase composed of methanol and water containing 2 mm ammonium acetate and 0.3% formic acid at a flow rate of 0.3 mL/min. The chromatographic running time was 4.0 min per sample. The MS detection was performed via an LC system with the positive ion electrospray ionization interface in multiple reaction monitoring mode using the transition of m/z 476.2 → 134.1 for UPA and m/z 479.3 → 416.2 for UPA-d3 [internal standard (IS)], respectively. UPA and IS were monitored without severe interference from the biological matrices. The method was linear over the wide concentration range of 0.300–300 ng/mL. The intra- and inter-day precision and accuracy were well within the limits required for bioanalytical assays. The method was first used to describe the pharmacokinetic characteristic of UPA after a single oral administration of ella in healthy Chinese volunteers. Based on a between-study comparison, there were statistically significant differences (p < .05) between Chinese and Caucasian volunteers for the systemic exposure of UPA, suggesting that race seems to significantly impact the systemic exposure of UPA.