Palmitoylation in Regulating Fyn Kinase Activity Based on FRET Imaging / 医用生物力学

Objective To investigate the molecular mechanism of palmitoylation modification in regulating the activity of non-receptor tyrosine kinase Fyn. Methods The intracellular Fyn activity was detected by applying fluorescence resonance energy transfer (FRET) technology, and the mechanism was investigated by combining with Fyn palmitoylation deficiency and C-terminal Src kinase ( CSK ) plasmid co-expression. ResultsExperimental data showed that single loss of either of ( C3, C6) palmitoylation sites resulted in higher Fyn activity, and C6 seemed more significant. It is known that CSK membrane translocation occurred after activation. FRET assay confirmed that CSK could down-regulate the activity of Fyn in cells, but could not effectively regulate the activity of Fyn(GSS) with the loss of palmitoylation sites. Conclusions The results in this study support the hypothesis on Fyn regulation by spatial localization, namely, non-palmitoylated Fyn (GSS) is less effective in the inhibitory regulation by CSK on cell membrane, thus promoting constitutive high activity expression

Progress in research on fluorescence resonance energy transfer technology based on upconversion nanomaterials for biological detection / 中国生物制品学杂志

@#Upconversion nanoparticles(UCNPs)doped with rare earth elements have advantages in biose-nsing because of their good fluorescence stability,biocompatibility and avoidance of background fluorescence. Therefore,fluorescence resonance energy transfer(FRET)system based on upconversion particles(UCNPs based FRET)has been widely used in biological detection. This paper reviews the application and prospect of UCNPs based FRET in biological detection of biotoxins,hormones,proteins,nucleic acids,bacteria,and so on.

Optimization of expression conditions of dengue virus NS2B-NS3 protease in E.coli and determination of enzyme activity / 中国生物制品学杂志

@#Objective To express dengue virus(DENV)NS2B-NS3 protease in E.coli,optimize the expression conditions and determine the enzyme activity,so as to lay a foundation of screening and discovering of lead compounds targeting DENV.Methods Codon-optimized NS2B-NS3 gene was inserted into pET-28a vector to construct recombinant prokaryotic expression plasmid pET-28a-NS2B-NS3,which was transformed E.coli Rosetta(DE3)competent cells and induced by IPTG to express NS2B-NS3 protease. The optimal expression conditions of NS2B-NS3 protease in E.coli were determined by optimizing induction length,induction temperature and IPTG concentration. NS2B-NS3 protease was isolated and purified by HisTrap~(TM) affinity chromatography column and measured for the protease activity by fluorescence resonance energy transfer(FRET)assay.Results The recombinant prokaryotic expression plasmid pET-28a-NS2B-NS3 was constructed correctly as identified by restriction analysis(NheⅠ/XhoⅠ)and sequencing. The optimal expression conditions of NS2BNS3 protease in E.coli were as follows:induction temperature of 20 ℃,induction length of 10 h and IPTG concentration of0. 2 mmol/L. The purified NS2B-NS3 protease showed a purity of more than 90% with a exhibited a of 20 mg/L,which bound to mouse monoclonal antibody against His-tag specifically and had good hydrolytic activity with a specific activity of 16. 111 U/mg,a K_m of 16. 46 μmol/L and a k_(cat) of 0. 028/s.Conclusion DENV NS2B-NS3 protease with high purity and activity was successfully prepared,which laid an experimental foundation of the establishment of high-throughput screening model for inhibitors targeting NS2B-NS3 protease.

Histone Variant H2A.Z Enhances the Stability of Nucleosomes under the Effect of Salt Ions / 中国生物化学与分子生物学报

In eukaryotes, the basic structural unit of chromatin is the nucleosome, and genomic DNA iscompressed in chromatin. The presence of nucleosomes usually inhibits the biological processes that occuron the DNA templates, such as transcription, replication, repair, and recombination,. The histonevariant H2A.Z can regulate the structure of chromatin and affect the transcription process of genes, but itsdetailed regulation mechanism remains unclear. In this paper, the method of Förster resonance energytransfer (FRET) was used to detect the influence of sodium chloride, potassium chloride, manganesechloride, calcium chloride and magnesium chloride on the dissociation of nucleosomes. Then, the stabilitydifferences between the nucleosomes containing the histone variant H2A. Z and the conventionalnucleosomes were compared under the action of salt ions. Widom 601 DNA sequence was labeled withdual fluorescence Cy3 and Cy5, and the dissociation of nucleosomes was reflected by the change offluorescence signal value. FRET results showed that the dissociation speed of nucleosomes containing thehistone variant H2A. Z under the action of sodium chloride, potassium chloride, manganese chloride, calcium chloride and magnesium chloride is slower than that of canonical nucleosomes, and the influenceof calcium chloride, manganese chloride and magnesium chloride on dissociation is more obvious thansodium chloride, potassium chloride. The results of electrophoresis analysis showed that the dissociationrate of nucleosomes containing histone variant H2A. Z was significantly lower than that of canonicalnucleosomes at 75℃. Fluorescence thermal shift (FTS) was used to further analyze the stability ofnucleosomes containing histone variant H2A.Z. It was found that the fluorescence signals of the two typesof nucleosomes showed two distinct growth periods, and the fluorescence signals generated in thedissociation process of the two types of nucleosomes showed two distinct growth periods. The temperaturecorresponding to the first increasing period of fluorescence signal in the dissociation process of H2A. Z-containing nucleosome is significantly higher than that in the dissociation process of the canonicalnucleosome, which indicated that the dissociation and denaturation temperature of the H2A.Z / H2B dimerin the nucleosome is higher than that of the canonical H2A / H2B dimer, and the H2A. Z-containingnucleosomes have high thermal stability. The results indicated that the structure of nucleosomes containingthe histone variant H2A.Z is more stable than that of canonical nucleosomes.

Optimization of expression conditions and determination the proteolytic activity of codon-optimized SARS-CoV-2 main protease in Escherichia coli / 生物工程学报

The main protease (Mpro) of SARS-CoV-2 is a highly conserved and mutation-resistant coronaviral enzyme, which plays a pivotal role in viral replication, making it an ideal target for the development of novel broad-spectrum anti-coronaviral drugs. In this study, a codon-optimized Mpro gene was cloned into pET-21a and pET-28a expression vectors. The recombinant plasmids were transformed into E. coli Rosetta(DE3) competent cells and the expression conditions were optimized. The highly expressed recombinant proteins, Mpro and Mpro-28, were purified by HisTrapTM chelating column and its proteolytic activity was determined by a fluorescence resonance energy transfer (FRET) assay. The FRET assay showed that Mpro exhibits a desirable proteolytic activity (25 000 U/mg), with Km and kcat values of 11.68 μmol/L and 0.037/s, respectively. The specific activity of Mpro is 25 times that of Mpro-28, a fusion protein carrying a polyhistidine tag at the N and C termini, indicating additional residues at the N terminus of Mpro, but not at the C terminus, are detrimental to its proteolytic activity. The preparation of active SARS-CoV-2 Mpro through codon-optimization strategy might facilitate the development of the rapid screening assays for the discovery of broad-spectrum anti-coronaviral drugs targeting Mpro.

A carbon nanoparticle-peptide fluorescent sensor custom-made for simple and sensitive detection of trypsin / 药物分析学报

Herein, we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles (CNPs) modified by acid oxidation. The fluorescence of the fluorescein-labelled peptide was quenched by CNPs. The sensor reacted with trypsin to cleave the peptide, resulting in the release of the dye moiety and a substantial increase in fluorescence intensity, which was dose-and time-dependent, and trypsin could be quantified accordingly. Correspondingly, the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity, with a detection limit of 0.7μg/mL. The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range, suitable for point-of-care testing. Furthermore, the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

A one-step specific assay for continuous detection of sirtuin 2 activity

Sirtuins (SIRTs) are nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases with diverse physiological functions. A variety of small molecules have been developed to interrogate the physiological function of SIRTs. Therefore, it is desirable to establish efficient and convenient assays to screen SIRTs modulators. In this study, we designed a series of fluorescent nonapeptide probes derived from substrates of SIRT1-SIRT3. Fluorescence increment of these probes is based on SIRT-mediated removal of the acyl side chain with fluorophore, which makes this system free of lysine-recognizing protease. Comparing the reaction of these fluorescent nonapeptide substrates with SIRT1-SIRT3 and SIRT6, it was confirmed that this assessment system was the most suitable for SIRT2 activity detection. Thus, SIRT2 was used to modify substrates by truncating the amino acids or lysine side chain of nonapeptide. Finally, two specific and efficient fluorescent probes for SIRT2, ne-D9 and ne-K4a, were developed. Evaluation of the results revealed that ne-K4a based assay was more suitable for modulators screening , while the other specific substrate ne-D9 was stable in cell lysate and could detect the activity of SIRT2 in the same. In summary, this study presents a novel strategy for detecting SIRT2 activity and in cell lysate.

Overview of the detection methods for equilibrium dissociation constant KD of drug-receptor interaction / 药物分析学报

Drug-receptor interaction plays an important role in a series of biological effects, such as cell pro-liferation, immune response, tumor metastasis, and drug delivery. Therefore, the research on drug-re-ceptor interaction is growing rapidly. The equilibrium dissociation constant (KD) is the basic parameter to evaluate the binding property of the drug-receptor. Thus, a variety of analytical methods have been established to determine the KD values, including radioligand binding assay, surface plasmon resonance method, fluorescence energy resonance transfer method, affinity chromatography, and isothermal ti-tration calorimetry. With the invention and innovation of new technology and analysis method, there is a deep exploration and comprehension about drug-receptor interaction. This review discusses the differ-ent methods of determining the KD values, and analyzes the applicability and the characteristic of each analytical method. Conclusively, the aim is to provide the guidance for researchers to utilize the most appropriate analytical tool to determine the KD values.

Insight into the interaction of inhaled corticosteroids with human serum albumin:A spectroscopic-based study / 药物分析学报

It is well known that the safety and efficacy profile of an inhaled cortocosteroid (ICS) is influenced by the pharmacokinetic properties and associated pharmacodynamic effects of the drug. Freely circulating, protein unbound, and active ICS can cause systemic adverse effects. Therefore, a detailed investigation of drug-protein interaction could be of great interest to understand the pharmacokinetic behaviour of corticosteroids and for the design of new analogues with effective pharmacological properties. In the present work, the interaction between some corticosteroids and human serum albumin (HSA) has been studied by spectroscopic approaches. UV–Vis spectroscopy confirmed that all the investigated corticos-teroids can bind to HSA forming a protein-drug complex. The intrinsic fluorescence of HSA was quenched by all the investigated drugs, which was rationalized in terms of a static quenching mechanism. The thermodynamic parameters determined by the Van't Hoff analysis of the binding constants (negativeΔH andΔS values) clearly indicate thathydrogen bonds and van der Waals forces play a major role in the binding process between albumin and betamethasone, flunisolide and prednisolone, while hydrophobic forces may play a major role in stabilizing albumin-triamcinolone complexes.

Effects of squalene on expression of LDLR in HepG2 cells and its mechanism / 中国药理学通报

Aim To investigate the effect of squalene on LDLR expression in HepG2 cells and its mechanism of down-regulated cholesterol. Methods The prolifer-ation of HepG2 cells exposed to squalene at different concentrations was measured by MTT assay. The effect of squalene on the expression of LDLR in HepG2 cells was measured by flow cytometry and fluorescence mi-croscopy. The effect of different concentrations of squa-lene on the interaction between SCAP and Insig2, two key protein molecules of SREBP pathway, was assayed by FRET technology. Results MTT results showed that squalene had inhibitory effect on the proliferation of HepG2 cells in a dose-dependent manner. Flow cy-tometry and fluorescence microscopy results showed that squalene enhanced LDLR expression in HepG2 cells compared with the control group. The results of FRET technology revealed that compared with model control group, the YFP fluorescence value in Squalene group dramatically declined, and the YFP fluorescence value of each drug group decreased with the range of 5~25 μmol·L-1 squalene concentration. Conclusions Squalene may promote the expression of LDLR in HepG2 cells through inhibiting the interaction between SCAP and Insig2 proteins in SREBP pathway, which may confirm that squalene is a potential novel drug for the down-regulation of cholesterol level.

Single Molecule Method for Molecular Biology

In order to understand biological phenomena accurately, single molecule techniques using a physical research approach to molecular interactions have been developed, and are now widely being used to study complex biological processes. In this review, we discuss some of the single molecule methods which are composed of two major parts: single molecule spectroscopy and manipulation. In particular, we explain how these techniques work and introduce the current research which uses them. Finally, we present the oral biology research using the single molecule methods.

Liposomes and lipid disks traverse the BBB and BBTB as intact forms as revealed by two-step Förster resonance energy transfer imaging

The blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB) prevent drug and nano-drug delivery systems from entering the brain. However, ligand-mediated nano-drug delivery systems have significantly enhanced the therapeutic treatment of glioma. In this study we investigated the mechanism especially the integrity of liposomes and lipid disks while traversing the BBB and BBTB both and . Fluorophores (DiO, DiI and DiD) were loaded into liposomes and lipid disks to form Förster resonance energy transfer (FRET) nano-drug delivery systems. Using brain capillary endothelial cells as a BBB model, we show that liposomes and disks are present in the cytoplasm as their intact forms and traverse the BBB with a ratio of 0.68‰ and 1.67‰, respectively. Using human umbilical vein endothelial cells as BBTB model, liposomes and disks remained intact and traversed the BBTB with a ratio of 2.31‰ and 8.32‰ at 3 h. imaging and immunohistochemical results revealed that liposomes and disks could traverse the BBB and BBTB as intact forms. In conclusion, these observations explain in part the mechanism by which nano-drug delivery systems increase the therapeutic treatment of glioma.

monitoring of the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET

Microemulsions are promising drug delivery systems for the oral administration of poorly water-soluble drugs. However, the evolution of microemulsions in the gastrointestinal tract is still poorly characterized, especially the structural change of microemulsions under the effect of lipase and mucus. To better understand the fate of microemulsions in the gastrointestinal tract, we applied small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET) to monitor the structural change of microemulsions under the effect of lipolysis and mucus. First, the effect of lipolysis on microemulsions was studied by SAXS, which found the generation of liquid crystalline phases. Meanwhile, FRET spectra indicated micelles with smaller particle sizes were generated during lipolysis, which could be affected by CaCl, bile salts and lecithin. Then, the effect of mucus on the structural change of lipolysed microemulsions was studied. The results of SAXS and FRET indicated that the liquid crystalline phases disappeared, and more micelles were generated. In summary, we studied the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET, and successfully monitored the appearance and disappearance of the liquid crystalline phases and micelles.

High-throughput screening for small molecule inhibitors of the type-I interferon signaling pathway

Interferons (IFNs) are cytokines with fundamental roles in resistance to infections, cancer and other diseases. Type-I IFNs, interferon (IFN-) and interferon (IFN-), act through a shared receptor complex (IFNAR) comprised of IFNAR1 and IFNAR2 subunits. Binding of type-I IFN to IFNAR1 will robustly activate Janus activated kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway. Aberrant activation of the type-I IFN response results in a spectrum of disorders called interferonopathies. The purpose of this research is to develop an assay for high-throughput screening (HTS) of small molecule inhibitors of the type-I IFN signaling pathway. Inhibition of type-I IFN signaling can be beneficial in terms of therapeutic use and understanding the underlying mechanism of action. We report here a HTS campaign with the secreted embryonic alkaline phosphatase (SEAP) reporter gene assay against 32,000 compounds which yielded 25 confirmed hits. These compounds were subsequently characterized for their cytotoxicity, effects on STAT phosphorylation and activities in IFN regulatory factor (IRF) transcription.

Diagnóstico clínico en saliva. Revisión

El odontólogo está llamado a convertirse en un elemento importante en el desarrollo de estudios de fenotipado de poblaciones para impulsar la aplicación de la medicina personalizada y la razón se debe a la saliva, que además de resultar un fluido imprescindible para la conservación de las funciones orales, se perfila con cualidades importantes para el diagnóstico clínico con base genética. Con el desarrollo de potentes técnicas de laboratorio, como el inmunoensayo, electroforesis, fluorescencia, cromatografía (HPLC y CG), espectrometría de masa (EM), la reacción en cadena de la polimerasa (PCR) y pruebas genéticas de fenotipado, se ha podido correlacionar la presencia de ciertos biomarcadores de daño tisular en la saliva con los niveles de esas especies en sangre. Estos biomarcadores constituyen señales del daño tisular o de respuestas del organismo a esas injurias, cuando aun no se pueden observar las evidencias clínicas del mismo. Esta aplicación de la saliva le confiere una importancia especial en lo referente al diagnóstico clínico. Al estudio de los biomarcadores orales se ha unido, de forma más reciente, el desarrollo de protocolos para la obtención de ADN genómico de la saliva que permite, por la viabilidad en la colección de muestras, su conservación y facilidades en su traslado, realizar estudios poblacionales para conocer la funcionalidad de ciertos genes que se relacionan con la biotransformación de los medicamentos, una causa importante de las variaciones interindividuales a los tratamientos farmacológicos. El conocimiento de polimorfismos en genes que expresan las enzimas que metabolizan fármacos específicos, permite realizar cambios en los principios activos o ajustes en las dosis de tratamientos individuales, que es el objetivo de la medicina personalizada o farmacogenética. Estos estudios también permiten conocer la predisposición genética de poblaciones al desarrollo de ciertas enfermedades, tanto orales como sistémicas, lo que propicia el establecimiento de nuevas políticas en la profilaxis y medicina preventiva. El uso de la saliva con estos fines abre nuevas perspectivas en la atención odontológica, y requiere de esfuerzos interdisciplinarios y cooperación en el equipo de salud.

The dentist is called to become an important element in the development of studies phenotyping of populations to advance the implementation of personalized medicine and the reason is because saliva, which besides being a prerequisite for the preservation of oral functions fluid , is emerging with important qualities for clinical diagnosis with genetic basis. With the development of powerful laboratory techniques, such as immunoassay, electrophoresis, fluorescence, chromatography (HPLC and GC), mass spectrometry (MS), polymerase chain reaction (PCR) and genetic testing phenotyping, it has been correlate the presence of certain biomarkers of tissue damage in saliva levels of these species in blood. These biomarkers are signs of tissue damage or agency responses to these injuries, when not even be seen clinical evidence of it. This application saliva attaches special importance with regard to clinical diagnosis. The study of oral biomarkers has joined, more recently, the development of protocols for obtaining genomic DNA from saliva that allows for viability in sample collection, preservation of the same and facilities during transport, conduct population studies to determine the function of certain genes that are related to biotransformation of drugs, a major cause of differences among individuals to drug treatments. Knowledge of polymorphisms in genes that express enzymes that metabolize specific drugs can make changes or adjustments active principles in doses of individual treatments, which is the goal of personalized medicine or pharmacogenetics. These studies also provide insight into the genetic predisposition of populations to the development of certain diseases, both oral and systemic, which favors the establishment of new policies in the prophylaxis and preventive medicine. The use of saliva for this purpose opens new perspectives in care dental and requires interdisciplinary efforts and cooperation in the health team.

FRET imaging of molecular hierarchy at subcellular levels in mechanotransduction / 医用生物力学

Cells in the body are exposed to physiological and pathophysiological stimuli that encompass both chemical and mechanical factors. It is important to understand how these factors modulate functions at cellular and organ levels. Compared to the large amount of information on cellular or organ responses to chemical factors, there is a paucity of knowledge on the effects of mechanical factors. Recent advances of fluorescence proteins and microscopy make it a very useful tool for elucidating the mechanotransduction processes; the state-of-the-art technologies for live-cell imaging of signaling is particularly valuable for investigating the spatial and temporal aspects of molecular mechanisms in mechanobiology. This review will cover the basic knowledge of fluorescence proteins and their application for biological research. In particular, the development and characterization of biosensors based on fluorescent resonance energy transfer (FRET) will be discussed. Genetically encoded FRET biosensors, which allows the imaging and quantification of tempo-spatial activation of molecules, will be introduced to demonstrate how the initiation and transmission of biochemical signals in response to local mechanical stimulation can be visualized in live cells. Specific emphasis will be on the elucidation of molecule hierarchy of signaling transduction in live cells upon the mechanical stimulation.

Comparison of activity of OsDmc1A recombinase of rice (Oryza sativa) in presence of Ca2+ and Mg2+ ions.

Recombinases are known to play an important role in the homology search and strand exchange during meiosis as well as homologous recombination (HR)-mediated DNA repair specifically require Mg2+ ion for their activity. The Ca2+ has been shown to stimulate the strand exchange activity of hDmc1 and ScDmc1 by forming the extended filaments on DNA. Oryza sativa disrupted meiotic cDNA1A (OsDmc1A), a homologue of yeast and human Dmc1 from rice shows the hallmark functions of recombinase. Here, we report the effects of Ca2+ and Mg2+ on OsDmc1A activity from rice (Oryza sativa). OsDmc1A showed a concentration-dependent binding with both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) substrates in presence of Mg2+ or Ca2+. The ssDNA and dsDNA binding activities, as well as renaturation activity of OsDmc1A were similar in the presence of Ca2+ or Mg2+. Increasing the Ca2+ or Mg2+ increased the DNA binding, renaturation and strand exchange of OsDmc1A. But, OsDmc1A showed only a slight stimulation of strand exchange activity in presence of Ca2+, when compared the activity in presence of Mg2+. Electron microscopy showed that OsDmc1A formed ring-like structures in presence of Mg2+ or Ca2+. However, OsDmc1A formed filament like structures with both ss and dsDNA in presence of Mg2+ or Ca2+. Taken together, Ca2+ did not affect OsDmc1A recombinase activity significantly.

Development of sandwich-form biosensor to detect Mycobacterium tuberculosis complex in clinical sputum specimens

Mycobacterium tuberculosis, the causing agent of tuberculosis, comes second only after HIV on the list of infectious agents slaughtering many worldwide. Due to the limitations behind the conventional detection methods, it is therefore critical to develop new sensitive sensing systems capable of quick detection of the infectious agent. In the present study, the surface modified cadmium-telluride quantum dots and gold nanoparticles conjunct with two specific oligonucleotides against early secretory antigenic target 6 were used to develop a sandwich-form fluorescence resonance energy transfer-based biosensor to detect M. tuberculosis complex and differentiate M. tuberculosis and M. bovis Bacille Calmette–Guerin simultaneously. The sensitivity and specificity of the newly developed biosensor were 94.2% and 86.6%, respectively, while the sensitivity and specificity of polymerase chain reaction and nested polymerase chain reaction were considerably lower, 74.2%, 73.3% and 82.8%, 80%, respectively. The detection limits of the sandwich-form fluorescence resonance energy transfer-based biosensor were far lower (10 fg) than those of the polymerase chain reaction and nested polymerase chain reaction (100 fg). Although the cost of the developed nanobiosensor was slightly higher than those of the polymerase chain reaction-based techniques, its unique advantages in terms of turnaround time, higher sensitivity and specificity, as well as a 10-fold lower detection limit would clearly recommend this test as a more appropriate and cost-effective tool for large scale operations.

2′-O-methyl nucleotide modified DNA substrates influence the cleavage efficiencies of BamHI and BglII.

Induction of endonucleolytic DNA cleavage is an essential event that links the initiating stimuli to the final effects of cells. The cleavage efficiency and thus the final yield could be affected by many factors, including structures of DNA substrates, composite structures of enzymes–substrates or enzymes–nucleic analogs and so on. However, it is not clear whether a nucleotide derivative-substituted in DNA substrates can influence the efficiency of enzymatic cleavage. To investigate the effect of sugar pucker conformation on DNA–protein interactions, we used 2′-O-methyl modified nucleotides (OMeN) to modify DNA substrates of isocaudemers BamHI and BglII in this study, and used FRET assay as an efficient method for analysis of enzyme cleavage. Experimental results demonstrated that OMeN-substituted recognition sequences influenced the cleavage rates significantly in a position-dependent manner. OMeN substitutions can reduce the cleavage as expected. Surprisingly, OMeN substitutions can also enhance the cleavage rates. The kinetics parameters of Vmax and Km have been obtained by fitting the Michaelis-Menten kinetic equation. These 2'- OMe nucleotides could behave as a regulatory element to modulate the enzymatic activity in vitro, and this property could enrich our understanding about the endonuclease cleavage mechanism and enhance our ability to regulate the enzymatic cleavage efficiency for applications in synthetic biology.

Establishment and optimization of a method for screening HIV-1 integrase 3′-processing inhibitor / 中国药理学通报

Aim To establish and optimize a method for screening HIV-1 integrase 3′-processing inhibitor. Methods Fluorescence resonance energy transfer ( FRET) was used to create an assay for screening in-tegrase 3′-processing inhibitors; wavelength was de-fined by DNaseⅠ; factors affecting IN activity were optimized, including buffer composition, substrate con-centration, enzyme concentration, metal ion concentra-tion. Results Integrase 3′-processing optimizing reac-tion conditions were buffer 1 , 500 nmol · L-1 sub-strate, 1 μmol·L-1 integrase, 20mmol·L-1 magne-sium ion. Positive drug raltegravir and myricetin could effectively inhibit integrase 3′-processing activity using this assay. Two integrase 3′-processing inhibitors were screened by this method. Conclusion The method for screening HIV-1 integrase 3′-processing inhibitor is successfully established and optimized.