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Herein, we prepared silver nanopentagons as colorimetric sensor to detect Cr3+ ions in aqueous solution in the presence of citrate and polyvinylpyrrolidone. Citrate and polyvinylpyrrolidone as stabilizer were utilized to anti-aggregate the silver nanopentagons. The non-functionalized silver nanopentagons provided a high-selective detection system for Cr3+ ions in aqueous solution. The result showed that Cr3+ ions could induce silver nanopentagons change to nanoparticles and aggregate, resulting in the color change from lime-green to pink. Therefore, the proposed detection system offered an effective visualizing monitor for Cr3+ ions by naked eye and quantitative detection by UV–Vis absorption spectroscopy. The detection for Cr3+ ions could be rapidly completed within 30 min, and the limit of detection could be up to 50 × 10–6 M (S/N = 3). The ratio of the absorbance (A550 nm and A392 nm) was linear to the concentration of Cr3+ ions from 80 µM to 10 mM. The result also illustrated the proposed system would specifically recognize Cr3+ ions from other tested heavy metal ions without the shielding reagent of metal ions. Silver nanopentagons as colorimetric sensor exhibited a great promising potential for Cr3+ ions in aqueous solution.

Group II introns are the putative progenitors of nuclear spliceosomal introns and use the same two-step splicing pathway. In the cell, the intron RNA forms a ribonucleoprotein (RNP) complex with the intron-encoded protein (IEP), which is essential for splicing. Although structures of spliced group II intron RNAs and RNP complexes have been characterized, structural insights into the splicing process remain enigmatic due to lack of pre-catalytic structural models. Here, we report two cryo-EM structures of endogenously produced group II intron RNPs trapped in their pre-catalytic state. Comparison of the catalytically activated precursor RNP to its previously reported spliced counterpart allowed identification of key structural rearrangements accompanying splicing, including a remodeled active site and engagement of the exons. Importantly, altered RNA–protein interactions were observed upon splicing among the RNP complexes. Furthermore, analysis of the catalytically inert precursor RNP demonstrated the structural impact of the formation of the active site on RNP architecture. Taken together, our results not only fill a gap in understanding the structural basis of IEP-assisted group II intron splicing, but also provide parallels to evolutionarily related spliceosomal splicing.

Nucleic acids containing genetic information are used as biomarkers for the diagnosis of genetic diseases. Herein, silver nanoparticles were utilized as probes to detect single stranded nucleic aci...

Rift Valley fever virus (RVFV) belongs to the order Bunyavirales and is the type species of genus Phlebovirus, which accounts for over 50% of family Phenuiviridae species. RVFV is mosquito-borne and causes severe diseases in both humans and livestock, and consists of three segments (S, M, L) in the genome. The L segment encodes an RNA-dependent RNA polymerase (RdRp, L protein) that is responsible for facilitating the replication and transcription of the virus. It is essential for the virus and has multiple drug targets. Here, we established an expression system and purification procedures for full-length L protein, which is composed of an endonuclease domain, RdRp domain, and cap-binding domain. A cryo-EM L protein structure was reported at 3.6 Å resolution. In this first L protein structure of genus Phlebovirus, the priming loop of RVFV L protein is distinctly different from those of other L proteins and undergoes large movements related to its replication role. Structural and biochemical analyses indicate that a single template can induce initiation of RNA synthesis, which is notably enhanced by 5′ viral RNA. These findings help advance our understanding of the mechanism of RNA synthesis and provide an important basis for developing antiviral inhibitors. IMPORTANCE The zoonosis RVF virus (RVFV) is one of the most serious arbovirus threats to both human and animal health. RNA-dependent RNA polymerase (RdRp) is a multifunctional enzyme catalyzing genome replication as well as viral transcription, so the RdRp is essential for studying the virus and has multiple drug targets. In our study, we report the structure of RVFV L protein at 3.6 Å resolution by cryo-EM. This is the first L protein structure of genus Phlebovirus. Strikingly, a single template can initiate RNA replication. The structure and assays provide a comprehensive and in-depth understanding of the catalytic and substrate recognition mechanism of RdRp.

Objective. To evaluate LEARNS model as a perioperative strategy for health education and nursing supervision of patients with laryngeal tumors. Methods. LEARNS scheme based on the best practice guidelines was applied to patients in the observation group: (1) analyze the needs of patients (Listen_L); (2) establish therapeutic partnership (Establish_E); (3) adopt intentional intervention (Adopt_A); (4) reinforce health awareness (Reinforce_R); (5) implement feedback assessment of knowledge (Name_N); (6) strengthen self-management based on community resources (Strengthen_S). In the control group, traditional medical care instructions were provided to the patients by medical staff. Parameters such as anxiety status, treatment compliance, nursing satisfaction, self-care ability, and life quality were compared between the observation and control groups. Results. Upon admission, there was no significant difference in self-care ability and anxiety level between two groups. However, the anxiety level of observation group was significantly lower than that of the control group 1 day before operation and 7 days after operation. Postoperative treatment compliance and nursing satisfaction were also improved in the observation group. In addition, self-care ability and life quality in the observation group were significantly enhanced as compared to the control group. Conclusion. As a mutual learning process between nurses and patients, LEARNS model motivates nurses to assess the needs of patients voluntarily. Furthermore, evidence-based education reinforces the self-care ability and health awareness of the patients. Our data suggests that LEARNS model is of great value in improving the life quality of the patients with laryngeal tumors and nursing satisfaction.

L-Histidine (L-His) is an essential amino acid, which is used to synthesize proteins and enzymes. The concentration of L-His in the body is controlled to regulate tissue growth and repair of tissues. In this study, a rapid and sensitive method was developed for colorimetric L-his detection using Cu2+ ions to inhibit the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system. H2O2 can oxidize TMB to oxTMB in the presence of copper, and the change in color from colorless (TMB) to blue (oxTMB) is similar to that observed in the presence of peroxidase. However, because the imidazole ring and carboxyl group of L-His can coordinate with Cu2+ ions to form stable L-His–Cu2+ complexes, the color of the TMB–H2O2 solution remains unchanged after the addition of L-His. Therefore, because L-His effectively hinders the colorimetric reaction of TMB with H2O2, this assay can be used to quantitatively determine the concentration of L-His in samples. Under optimized conditions, our colorimetric sensor exhibited two linear ranges of 60 nM to 1 μM and 1 μM to 1 mM for L-His detection and a detection limit of 50 nM (S/N = 3); furthermore, the assay can be performed within 20 min. Moreover, the proposed assay was used to determine the concentration of L-His in urine samples, suggesting that this convenient and label-free colorimetric method presents promising applications in bioanalytical chemistry and clinical diagnosis.

Rift Valley fever virus (RVFV) belongs to the order Bunyavirales and is the type species of genus Phlebovirus, which accounts for over 50% of family Phenuiviridae species. RNA-dependent RNA polymerase (L protein) is responsible for facilitating the replication and transcription of the virus. We report two cryo-EM RVFV L protein structures at 3.6 Å and 3.8 Å resolution in the presence and absence of RNA, respectively. In this first L protein structure of genus Phlebovirus, viral RNA induces considerable conformational changes of the polymerase. The RVFV L protein priming loop is distinctly different from those of other L proteins and undergoes large movements related to its replication elongation role. Structural and biochemical analyses indicate that a single template can initiate RNA replication, which is notably enhanced by 5’ viral RNA. These findings advance our understanding of RNA synthesis mechanism and provide a basis for antiviral inhibitor development.

Although single-particle cryogenic electron microscopy (cryo-EM) has been applied extensively for elucidating many crucial biological mechanisms at the molecular level, this technique still faces critical challenges, the major one of which is to prepare the high-quality cryo-EM specimen. Aiming to achieve a more reproducible and efficient cryo-EM specimen preparation, novel supporting films including graphene-based two-dimensional materials have been explored in recent years. Here we report a robust and simple method to fabricate EM grids coated with single- or few-layer reduced graphene oxide (RGO) membrane in large batch for high-resolution cryo-EM structural determination. The RGO membrane has decreased interlayer space and enhanced electrical conductivity in comparison to regular graphene oxide (GO) membrane. Moreover, we found that the RGO supporting film exhibited nice particle-absorption ability, thus avoiding the air-water interface problem. More importantly, we found that the RGO supporting film is particularly useful in cryo-EM reconstruction of sub-100 kDa biomolecules at near-atomic resolution, as exemplified by the study of RBD-ACE2 complex and other small protein molecules. We envision that the RGO membranes can be used as a robust graphene-based supporting film in cryo-EM specimen preparation.

Nucleic acids detection has significant meanings in disease diagnosis, monitoring of environment and so on. However, only trace concentration of nucleic acids exists in specimen. Ultrasensitive nucleic acids detection is required based on the strategies of signal amplification. Currently, DNA nanotechnologies are employed to amplify the detecting signal, mainly including DNA hybridization-based sensors and DNA circuits-based sensors. DNA circuits-based sensors have higher sensitive than that of DNA hybridization-based sensors, which attract the attention of researchers. With this view, we present an overview of DNA circuits-based amplification strategies for nucleic acids detection with fluorescent sensors and electrochemical sensors, respectively. It mainly contains duplex specific nuclease (DSN)-based DNA circuits and strand displace reaction (SDR)-based DNA circuits, which enable nucleic acids to trigger DNA circuits without consumption. The strategies can multiply the increase of the signal of nucleic acids with simple operation. Meanwhile, this review discusses the current challenges and future outlook of DNA circuits in sensors. We envision that our review provides implications to promote the development of DNA circuits-based biosensors for nucleic acids detection.

Nucleic acid detection is becoming increasingly important in the diagnostics of genetic diseases for biological analysis. We herein propose gold nanoparticles as probe for colorimetric detection of nucleic acids with branched DNA nanostructures, which enables a novel and simple colorimetric biosensor. In our system, the target DNA specifically triggered two short-chain ssDNA probes to generate branched DNA nanostructures (Y-shape DNA), which prevent AuNPs from aggregation in aqueous NaCl solution. On the contrary, when the target DNA did not exist, gold nanoparticles were unstable and aggregated easily because there is no anti-aggregation function from Y-shape DNA. Sensor response was found to be proportional to the target DNA concentration from 5 to 100[Formula: see text]nM, with detection limits determined as 5[Formula: see text]nM. The developed platform is for colorimetric nucleic acid detection without enzymes, label and modification holds great promise for practical applications.