A Step toward Molecular Evolution of RNA: Ribose Binds to Prebiotic Fatty Acid Membranes,and Nucleosides Bind Better than Individual Bases Do

A major challenge in understanding how biological cells arose on the early Earth is explaining how RNA and membranes originally colocalized. We propose that the building blocks of RNA (nucleobases and ribose) bound to self-assembled prebiotic membranes. We have previously demonstrated that the bases bind to membranes composed of a prebiotic fatty acid, but evidence for the binding of sugars has remained a technical challenge. Here, we used pulsed-field gradient NMR spectroscopy to demonstrate that ribose and other sugars bind to membranes of decanoic acid. Moreover, the binding of some bases is strongly enhanced when they are linked to ribose to form a nucleoside or – with the addition of phosphate – a nucleotide. This enhanced binding could have played a role in the molecular evolution leading to the production of RNA.     

Formation of RNA Phosphodiester Bond by Histidine‐Containing Dipeptides

A new scenario for prebiotic formation of nucleic acid oligomers is presented. Peptide catalysis is applied to achieve condensation of activated RNA monomers into short RNA chains. As catalysts, L ‐dipeptides containing a histidine residue, primarily Ser‐His, were used. Reactions were carried out in selforganised environment, a water‐ice eutectic phase, with low concentrations of reactants. Incubation periods up to 30 days resulted in the formation of short oligomers of RNA. During the oligomerisation, an active intermediate (dipeptide–mononucleotide) is produced, which is the reactive species. Details of the mechanism and kinetics, which were elucidated with a set of control experiments, further establish that the imidazole side chain of a histidine at the carboxyl end of the dipeptide plays a crucial role in the catalysis. These results suggest that this oligomerisation catalysis occurs by a transamination mechanism. Because peptides are much more likely products of spontaneous condensation than nucleotide chains, their potential as catalysts for the formation of RNA is interesting from the origin‐of‐life perspective. Finally, the formation of the dipeptide–mononucleotide intermediate and its significance for catalysis might also be viewed as the tell‐tale signs of a new example of organocatalysis.     

Prebiotic Membranes and Micelles Do Not Inhibit Peptide Formation During Dehydration

Cycles of dehydration and rehydration could have enabled formation of peptides and RNA in otherwise unfavorable conditions on the early Earth. Development of the first protocells would have hinged upon colocalization of these biopolymers with fatty acid membranes. Using atomic force microscopy, we find that a prebiotic fatty acid (decanoic acid) forms stacks of membranes after dehydration. Using LC-MS-MS (liquid chromatography-tandem mass spectrometry) with isotope internal standards, we measure the rate of formation of serine dipeptides. We find that dipeptides form during dehydration at moderate temperatures (55 °C) at least as fast in the presence of decanoic acid membranes as in the absence of membranes. Our results are consistent with the hypothesis that protocells could have formed within evaporating environments on the early Earth.     

间二氯苯水解制备间苯二酚

以间二氯苯为原料、La2O3为催化剂,在KOH水溶液中水解生成间苯二酚.在高压反应釜中考察了反应温度、催化剂、pH、物料配比及搅拌速率对反应结果的影响.实验结果表明,间二氯苯水解的适宜工艺条件为:反应温度260℃、反应体系pH为13.4、V(水)∶V(间二氯苯)=15∶1、搅拌速率为400 r/min.在上述工艺条件下,间二氯苯转化率>70%,间苯二酚收率>20%.     

Formation versus Hydrolysis of the Peptide Bond from a Quantum-mechanical Viewpoint: The Role of Mineral Surfaces and Implications for the Origin of Life

The condensation (polymerization by water elimination) of molecular building blocks to yield the first active biopolymers (e.g. of amino acids to form peptides) during primitive Earth is an intriguing question that nowadays still remains open since these processes are thermodynamically disfavoured in highly dilute water solutions. In the present contribution, formation and hydrolysis of glycine oligopeptides occurring on a cluster model of sanidine feldspar (001) surface have been simulated by quantum mechanical methods. Results indicate that the catalytic interplay between Lewis and Brønsted sites both present at the sanidine surface, in cooperation with the London forces acting between the biomolecules and the inorganic surface, plays a crucial role to: i) favour the condensation of glycine to yield oligopeptides as reaction products; ii) inhibit the hydrolysis of the newly formed oligopeptides. Both facts suggest that mineral surfaces may have helped in catalyzing, stabilizing and protecting from hydration the oligopeptides formed in the prebiotic era.     

Synthesis of Potassium Niobate from Metal Alkoxides

Preparation of potassium niobate from metal alkoxides was investigated. Potassium-niobium ethoxide, KNb(OC₂H₅)₆, and potassium-niobium propoxide, KNb(OC₃H₇)₆, were synthesized and subsequently hydrolyzed using several water concentrations (0.75 to 6.0 mol of water/(mol of alkoxide)). Rapid precipitation of potassium-deficient particles occurred when higher concentrations of water were used. This resulted in the formation of a multiphase material after calcination, as X-ray diffraction showed the presence of both KNbO₃ and potassium-deficient oxide phases(s). Single-phase KNbO₃ could be prepared by two methods: (1) hydrolysis of KNb(OC₃H₇)₆/propanol solutions using 1 mol of water (per mole of propoxide) added as a water/propanol solution and (2) hydrolysis of KNb(OC₂H₅)₆/ethanol solutions using 1 mol of water (per mole of ethoxide) added as a water/methanol solution. The latter method provided advantages of low calcination temperature for the formation of single-phase KNbO₃ and low weight loss after calcination.     

石油焦制备活性炭成孔机理的探讨

论述了以炼厂石油焦为原料,采用以KOH为活化剂的化学活化法制备活性炭的成孔机理,同时根据成孔机理,对影响活性炭孔结构的因素进行了分析。     

A Possible Path to Prebiotic Peptides Involving Silica and Hydroxy Acid‐Mediated Amide Bond Formation

The formation of alanine and glycine oligomers in films produced by drying aqueous mixtures of lactic acid and silica nanoparticles has been studied as a model prebiotic reaction. The addition of silica results in alanine or glycine enrichment in the polymers. Oligomerization proceeds through ester‐mediated peptide bond formation in an acidic and evaporative environment at temperatures as low as 85 °C. For both amino acids, the dominant species produced in the presence of silica and lactic acid are rich in amide bonds and deficient in ester linkages. At higher temperatures, glycine and alanine oligomers contain only a single hydroxy acid residue conjugated to the peptide N terminus. Similar product distributions occur with silica particles prereacted with lactic acid, which suggests the catalytic role of a functionalized surface. This work highlights the role minerals might have served in transitioning from oligomers with both ester and amide linkages (depsipeptides) to peptides in a prebiotic context.     

无水对甲基苯磺酸的固态生成焓

用精密转动氧弹燃烧热量计和衬铂氧弹测量了含一定结晶水的对甲基苯磺酸样品的固态燃烧焓值，用两种方法估算了无水对甲基苯磺酸（ＴＳＡ）的固态生成焓值。其平均值和总误差为５００±２４ｋＪ／ｍｏ     

利用煤的形成过程提质褐煤

褐煤的高水分量几乎影响褐煤利用的每一方面。为了实现褐煤资源的高效利用,本文中利用煤的形成过程设计了一套褐煤提质工艺,主要是模拟一个高压、高温的环境加速褐煤转变。工艺中要求合适的压力和温度,可以明显提高脱水率。     

Aptamer to ribozyme: the intrinsic catalytic potential of a small RNA

The discovery of RNA-based catalysis 23 years ago dramatically changed the way biologists and biochemists thought of RNA. In the recent past, several ribozymes structures have provided some answers as to how catalysis is accomplished and how it relates to RNA structure and folding. However, there is still little information as to how catalytic activity evolved. Here we show that the small malachite green-binding aptamer has intrinsic catalytic potential that can be realized by designing the proper substrate. The charge distribution within the RNA binding pocket stabilizes the transition state of an ester hydrolysis reaction and thus accelerates the overall reaction. The results suggest that electrostatic forces can contribute significantly to RNA-based catalysis. Moreover, even simple RNA structures that have not been selected for catalytic properties can have a basic catalytic potential if they encounter the right substrate. This provides a possible starting point for the molecular evolution of more complex ribozymes.     

Genome-Wide Analysis Indicates a Complete Prostaglandin Pathway from Synthesis to Inactivation in Pacific White Shrimp,Litopenaeus vannamei

Prostaglandins (PGs) play many essential roles in the development, immunity, metabolism, and reproduction of animals. In vertebrates, arachidonic acid (ARA) is generally converted to prostaglandin G₂ (PGG₂) and H₂ (PGH₂) by cyclooxygenase (COX); then, various biologically active PGs are produced through different downstream prostaglandin synthases (PGSs), while PGs are inactivated by 15-hydroxyprostaglandin dehydrogenase (PGDH). However, there is very limited knowledge of the PG biochemical pathways in invertebrates, particularly for crustaceans. In this study, nine genes involved in the prostaglandin pathway, including a COX, seven PGSs (PGES, PGES2, PGDS1/2, PGFS, AKR1C3, and TXA2S), and a PGDH were identified based on the Pacific white shrimp (Litopenaeus vannamei) genome, indicating a more complete PG pathway from synthesis to inactivation in crustaceans than in insects and mollusks. The homologous genes are conserved in amino acid sequences and structural domains, similar to those of related species. The expression patterns of these genes were further analyzed in a variety of tissues and developmental processes by RNA sequencing and quantitative real-time PCR. The mRNA expression of PGES was relatively stable in various tissues, while other genes were specifically expressed in distant tissues. During embryo development to post-larvae, COX, PGDS1, GDS2, and AKR1C3 expressions increased significantly, and increasing trends were also observed on PGES, PGDS2, and AKR1C3 at the post-molting stage. During the ovarian maturation, decreasing trends were found on PGES1, PGDS2, and PGDH in the hepatopancreas, but all gene expressions remained relatively stable in ovaries. In conclusion, this study provides basic knowledge for the synthesis and inactivation pathway of PG in crustaceans, which may contribute to the understanding of their regulatory mechanism in ontogenetic development and reproduction.     

热敏性及易结垢性物料加热技术新进展

论述了热敏性及易结垢性能物料的加热技术及其新进展。     

Experimental Investigations of Regimes of Bubble Formation on Submerged Orifices Under Constant Flow Condition

Regimes of bubble formation on a submerged orifice under constant flow conditions were investigated experimentally. The effects of orifice diameter, surface characteristics (contact angle and roughness) and surface tension on the regimes of bubble formation were studied for a wide range of gas flow rates. In particular, the transitions of period‐1 to period‐2 bubbling regime, with pairing or with coalescence at the orifice, and period‐2 to chaotic bubbling were investigated in detail. An attempt is made to provide a generalized bubble formation regime map constructed using appropriate dimensionless numbers. The physical understanding of various bubbling regimes and the experimental data on the effects of various system parameters are expected to contribute to the development and validation of analytical and CFD models     

含镍配合物的合成、表征及其对尿素水解的影响

报道了对称六齿配体N,N,N′,N′, 四(2′ 苯并咪唑甲基)乙二胺(EDTB)的一种含镍(II)配合物[Ni(EDTB)·C6H5COO(OH)]·ClO4·CH3CH2OH·H2O的合成、表征及其对尿素水解的影响。根据配合物元素分析、摩尔电导、紫外 可见、红外、ESR谱和循环伏安(CV)等性质,与已测X 射线单晶结构的同种配体含铜(Ⅱ)单核配合物比较,推测此配合物中的Ni(Ⅱ)离子被配体EDTB的4个苯并咪唑氮和1个烷胺氮与水杨酸根的1个羧基氧配位,形成一种畸变八面体几何构型,并用气相色谱法观测了此配合物对尿素水解的影响,结果表明,它具有催化尿素水解的活性。     

Formation of methyl methacrylate from methyl propionate and methanol

The formation of methyl methacrylate (MMA) was studied in a vapor-phase reaction between methyl propionate (MP) and methanol without using any sources of formaldehyde. Silica-supported CsOH doped with a small amount of silver Ag was found to be the best catalyst. The optimum Ag/Cs/Si atomic ratio was 4–10/20–25/1000. When the reaction was performed in the absence of oxygen in the feed, the main product was methyl isobutyrate (MIB) at the beginning of the reaction; MMA was not obtained. As the time-on-stream increased, the formation of MIB fell, while that of MMA increased, showed a maximum, and then decreased gradually. In the case of the reaction performed in the presence of oxygen, the catalytic activity was stable. As the amount of oxygen increased, the yield of MMA increased, while the selectivity fell. The performances were further improved by the combination of a small amount of Ag–Cs/SiO₂ catalyst and a large amount of Cs/SiO₂ catalyst.     

化学-酶法合成普瑞巴林的研究进展

综述了近年来将酶催化拆分与传统的有机合成相结合制备普瑞巴林的研究新进展,重点介绍酶在普瑞巴林手性中间体制备中的应用,并对生物催化应用于普瑞巴林合成的意义及存在的问题进行了分析.     

Formation of Mullite from Pyrophyllite by Mechanical and Thermal Treatments

When pyrophyllite is submitted to mechanical and thermal treatments, significant changes take place, according to XRD and DTA results. With grinding, the DTA endothermic peak is shifted to 540°C and becomes sharper and similar to kaolinite. A sharp exothermic peak is also produced at 1000°C, which is not present in the unground material. Increasing the mullite is associated with the formation of the latter peak. Thermal treatment causes the formation of mullite at higher temperatures.