Though the ''RNA world'' hypothesis has gained a central role in ideas concerning the origin of life, the scenario concerning its emergence remains uncertain. It has been speculated that the first scene may have been the emergence of a template-dependent RNA synthetase ribozyme, which catalyzed its own replication: thus, ''RNA replicase.'' However, the speculation remains uncertain, primarily because of the large sequence length requirement of such a replicase and the lack of a convincing mechanism to ensure its self-favoring features. Instead, we propose a nucleotide synthetase ribozyme as an alternative candidate, especially considering recent experimental evidence suggesting the possibility of effective nonenzymatic templatedirected synthesis of RNA. A computer simulation was conducted to support our proposal. The conditions for the emergence of the nucleotide synthetase ribozyme are discussed, based on dynamic analysis on a computer. We suggest the templatedependent RNA synthetase ribozyme emerged later, perhaps after the emergence of protocells.

It is very likely that life began with some RNA (or RNA-like) molecules, self-replicating by base-pairing and exhibiting enzyme-like functions that favored the self-replication. Different functional molecules may have emerged by favoring their own self-replication at different aspects. Then, a direct route towards complexity/efficiency may have been through the coexistence/cooperation of these molecules. However, the likelihood of this route remains quite unclear, especially because the molecules would be competing for limited common resources. By computer simulation using a Monte-Carlo model (with “micro-resolution” at the level of nucleotides and membrane components), we show that the coexistence/cooperation of these molecules can occur naturally, both in a naked form and in a protocell form. The results of the computer simulation also lead to quite a few deductions concerning the environment and history in the scenario. First, a naked stage (with functional molecules catalyzing template-replication and metabolism) may have occurred early in evolution but required high concentration and limited dispersal of the system (e.g., on some mineral surface); the emergence of protocells enabled a “habitat-shift” into bulk water. Second, the protocell stage started with a substage of “pseudo-protocells”, with functional molecules catalyzing template-replication and metabolism, but still missing the function involved in the synthesis of membrane components, the emergence of which would lead to a subsequent “true-protocell” substage. Third, the initial unstable membrane, composed of prebiotically available fatty acids, should have been superseded quite early by a more stable membrane (e.g., composed of phospholipids, like modern cells). Additionally, the membrane-takeover probably occurred at the transition of the two substages of the protocells. The scenario described in the present study should correspond to an episode in early evolution, after the emergence of single “genes”, but before the appearance of a “chromosome” with linked genes.

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The "RNA world" hypothesis has offered a framework for both experimental and theoretical work in the field of the origin of life. An important concern about the hypothesis is how the RNA world could originate. It has long been speculated that a template-dependent RNA synthetase ribozyme, which catalyzed its own replication (thus, an "RNA replicase"), should have emerged first. However, experimental searches for such a replicase have so far been unsuccessful. This is primarily because of the large sequence length of candidate ribozymes, which mainly work in a polymerase-like way. Here, we propose that the replicase that emerged first would be a simple template-dependent ligase ribozyme, which loosely binds to template RNA and has a relatively low efficiency of catalyzing the formation of phosphodiester bonds between adjacently aligned nucleotides or oligonucleotides. We conducted a computer simulation to support this proposal and considered the factors that might affect the emergence of the ribozyme based on the parameter analysis in the simulation. We conclude that (1) a template-dependent ligase may be more likely than a template-dependent polymerase as an early replicase in the emergence of RNA-based replication; (2) such a ligase ribozyme could emerge and be stable against parasites under a broad range of parameters in our model; (3) the conditions shown to favor the initial appearance of a template-dependent ligase ribozyme do not favor its spread.

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Extraction of genomic DNA using a new amino silica monolithic column A new amino silica monolithic column was developed for DNA extraction in a miniaturized format. The monolithic column was prepared in situ by polymerization of tetraethoxysilane (TEOS) and N-(b-aminoethyl)-c-aminopropylmethyldimethoxysilane (AEAPMDMS). DNA was loaded in 50 mM tris(hydroxylmethyl)aminomethane -EDTA buffer at pH 7.0 and eluted with 300 mM potassium phosphate solution at pH 10.0. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 56 ng DNA with an extraction efficiency of 71 l 5.2% (X l RSD). When the amino silica monolithic column was applied to extract genomic DNA from the whole blood of crucian carp, an extraction efficiency of 52 l 5.6% (X l RSD) was obtained by three extractions. Since the chaotropic-based sample loading and organic solvent wash steps were avoided in this procedure, the purified DNA was suitable for downstream processes such as PCR. This amino silica monolithic column was demonstrated to allow rapid and efficient DNA purification in microscale.

The low-affinity interaction between human serum albumin (HSA) and Diclofenac sodium (DCF) was studied using NMR techniques. Both

Background During the coronavirus disease 2019 (COVID-19) pandemic, exploring factors influencing nosocomial infection among frontline nurses may provide evidence to optimize prevention strategies in hospitals. Method A large-scale online questionnaire survey of nurses’ state-trait anxiety, job burnout, risk perception, workplace safety perception, knowledge about nosocomial infection, and preventive practices was conducted with 2795 frontline nurses working in the COVID-19 wards of six hospitals in Hubei Province, China, from February 1 to April 1, 2020. The questionnaire data were analyzed using the structural equation modeling (SEM) method to reveal the mechanisms influencing nurses’ risk perception and preventive practices related to nosocomial COVID-19 infection. Results A model of the factors that influence nurses’ risk perception and preventive practices regarding nosocomial COVID-19 infection was established. The model verified hypotheses regarding the impact of nurses’ risk perception and preventive practices. Notably, the hypothesis that risk perception has an impact on nurses’ preventive practices regarding nosocomial infection is not valid. Moreover, different marital and educational conditions are associated with significant differences in the impact of state anxiety on the execution of preventive practices, the impact of workplace safety perceptions on risk perception, and the impact of workplace safety perceptions on the execution of preventive practices. The effect of state anxiety on preventive practices differed significantly with different durations of work experience. Conclusions According to the results of the influencing factor model, promoting the quality of training on nosocomial infection, meliorating workplace safety, and conducting timely and effective psychological interventions would aid in improving nurses’ preventive practices. Meliorating workplace safety and easing state anxiety would be beneficial to reduce nurses’ risk perception. These strategies are conducive to the optimization of policies for preventing nosocomial COVID-19 infections and similar infectious diseases.