Publications by authors named "Jicun Ren"

Autophagy is a widely conserved and multistep cellular catabolic process and maintains cellular homeostasis and normal cellular functions the degradation of some harmful intracellular components. It was reported that high basal autophagic activity may be closely related to tumorigenesis. So far, the fluorescence imaging technique has been widely used to study autophagic processes, but this method is only suitable for distinguishing autophagosomes and autolysosomes.

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Protein phase separation plays a very important role in many biological processes and is closely related to the occurrence and development of some serious diseases. So far, the fluorescence imaging method and fluorescence correlation spectroscopy (FCS) have been frequently used to study the phase separation behavior of proteins. Due to the wide size distribution of protein condensates in phase separation from nano-scale to micro-scale in solution and living cells, it is difficult for the fluorescence imaging method and conventional FCS to fully reflect the real state of protein phase separation in the solution due to the low spatio-temporal resolution of the conventional fluorescence imaging method and the limited detection area of FCS.

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The detection of intrinsic protein fluorescence is a powerful tool for studying proteins in their native state. Thanks to its label-free and stain-free feature, intrinsic fluorescence detection has been introduced to polyacrylamide gel electrophoresis (PAGE), a fundamental and ubiquitous protein analysis technique, to avoid the tedious detection process. However, the reported methods of intrinsic fluorescence detection were incompatible with online PAGE detection or standard slab gel.

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Electrophoresis titration chip (ETC) is a versatile tool for onsite and point-of-care quantification analyses because it affords naked-eye detection and a straightforward quantification format. However, it is vulnerable to changes in environmental temperature, which regulates the electrophoretic migration by affecting the ion mobility and the target recognition by influencing the enzyme activity. Therefore, the quantification accuracy of the ETC tests was severely compromised.

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Liquid-liquid phase separation (LLPS) of fused in sarcoma (FUS) has emerged as a fundamental principle underpinning cellular function and malfunction. However, we know little about the FUS phase transition process from individual molecules to nanoscale condensates, which plays important roles in neurodegenerative diseases. Here, we propose the fluorescence correlation spectroscopy (FCS) method to quantitatively study the phase separation process of FUS protein with the fluorescent tag-enhanced green fluorescent protein (EGFP), from individual molecules to nanoscale condensates.

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Polyacrylamide gel electrophoresis (PAGE) is one of the most popular techniques for the separation and detection of nucleic acids. However, it requires a complicated detection procedure and offline detection format, which inevitably leads to band broadening and thus compromises the separation resolution. To overcome this problem, we developed an online PAGE (OPAGE) platform by integrating the gel electrophoresis apparatus with the gel imaging system, so as to obviate the need for the complicated detection procedure.

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The Coding Region Determinant-Binding Protein (CRDBP) is a carcinoembryonic protein, and it is overexpressed in various cancer cells in the form of granules. We speculated the formation of CRDBP granules possibly through liquid-liquid phase separation (LLPS) processes due to the existence of intrinsically disordered regions (IDRs) in CRDBP. So far, we did not know whether or how phase separation processes of CRDBP occur in single living cells due to the lack of methods for studying intracellular protein phase separation.

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Deubiquitination is a reverse post-translational modification of ubiquitination and plays significant roles in various signal transduction cascades and protein stability. The p53 is a very important tumor-suppressor protein and closely implicates more than 50% of human cancers. Although extracellular studies on the deubiquitination of p53 were reported, the process of p53 deubiquitination in living cells due to the shortage of an efficient in situ method for single living cells is still not clear.

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Resonance light-scattering correlation spectroscopy (RLSCS) is a new single-particle detection method with its working principle being like fluorescence correlation spectroscopy (FCS). RLSCS is obtained by autocorrelation function analysis on the measured fluctuation of the resonance light scattering (RLS) intensity occurring within a subfemtoliter volume when a single nanoparticle (such as gold nanoparticles (NPs) or silver (SNPs)) freely diffuses through the volume. The RLSCS technique can detect such parameters as concentration, diffusion coefficient (translation and rotation), etc.

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Isoelectric focusing (IEF) is a powerful tool for resolving complex protein samples, which generates IEF patterns consisting of multiplex analyte bands. However, the interpretation of IEF patterns requires the careful selection of isoelectric point (pI) markers for profiling the pH gradient and a trivial process of pI labeling, resulting in low IEF efficiency. Here, we for the first time proposed a marker-free IEF method for the efficient and accurate classification of IEF patterns by using a convolutional neural network (CNN) model.

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Newly synthesized proteins are closely related to a series of biological processes, including cell growth, differentiation, and signaling. The post-translational modifications (PTMs) of newly synthesized proteins help maintain normal cellular functions. Ubiquitination is one of the PTMs and plays a prominent role in regulating cellular functions.

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Autophagy is a fundamental and phylogenetically conserved self-degradation process and plays a very important role in the selective degradation of deleterious proteins, organelles, and other macromolecules. Although flow cytometry and fluorescence imaging techniques have been used to assess autophagic flux, we remain less able to monitor autophagic flux in a highly sensitive, robust, and well-quantified manner. Here, we reported a new method for real-time and quantitatively monitoring autophagosomes and assessing autophagic flux in living cells based on fluorescence correlation spectroscopy (FCS).

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Desalting of biosamples is crucial for analytical techniques intolerant to abundant salts. However, there is no simple tool to monitor the desalting of low-volume biosamples so far. Here we developed a handheld capacitively coupled contactless conductivity detector (hCD) as a miniaturized device to measure the conductivity of 75 μL biosamples.

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Cholesterol (CHO) in human blood is one of the most frequently and crucially quantified substances in diagnostic laboratories. However, visual and portable point of care testing (POCT) methods have been rarely developed for the bioassay of CHO in blood samples. Here, we developed an electrophoresis titration (ET) model, a chip device of ∼60 grams, and a quantification method for the POCT of CHO in blood serum based on a moving reaction boundary (MRB).

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Intrinsic fluorescence imaging (IFI) has been used for the stain-free detection of proteins in slab gel. However, complicated detection setups and small irradiation area limited the development of facile, online, and portable imaging of the whole slab gel. We here designed a quadruple UV LED array to produce even and powerful area light for direct irradiation of gel electrophoresis chip (GEC) at 275 nm.

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Matrix metalloproteinase-9 (MMP-9) plays an important role in tumor progression. It is of great significance to establish a sensitive assay strategy for MMP-9 activity in single living cells. Here a novel single molecule spectroscopy method based on the fluorescence correlation spectroscopy (FCS) technique was proposed for measuring the MMP-9 activity at different locations within single living cells, using a fluorescent specific peptide and a reference dye as dual probes.

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The protein corona of nanoparticles (NPs) plays a crucial role in determining NPs' biological fates. Here, a novel measurement strategy was proposed to in situ investigate the protein corona formed in the NPs with the home-built dual-wavelength laser-irradiated differenced resonance light scattering correlation spectroscopy (D-RLSCS) technique, combined with the modified generation method of the D-RLSCS curve. With the measurement strategy, the dissociation constants and the binding rates between proteins and gold nanoparticles (GNPs) were determined based on the binding-induced ratiometric diffusion change of NPs (the ratio of characteristic rotational diffusion time to translational one), using the formation of the protein corona of bovine serum albumin (BSA) or fibrinogen (FIB) on gold nanoparticles as a model.

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Photoluminescence (PL) intermittency (or "blinking") is a unique characteristic of single quantum dot (QD) emission. Here, we report a novel single-molecule detection strategy for the intracellular mRNA of interest using the mRNA-induced nonblinking QD dimers as probes. The working principle of the method is that the DNA hybrid of the target DNA (or mRNA) with a biotin-modified ssDNA probe can induce two blinking streptavidin-modified QDs (SAV-QDs) conjugated.

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For designing and constructing a highly efficient CRET system, it is extremely important to systematically study the effects of reactants and the catalysts on the efficiency. In this paper, we investigated the effects of reactants and the catalyst hemin/G-quadruplex DNAzyme concentration, donor-acceptor ratio and distance on the CRET efficiency by CL imaging. The CRET system was based on hemin/G-quadruplex DNAzyme catalyzed luminol analogue L012 and hydrogen peroxide CL system, taking luminol analogue L012 as the energy donor and a quenching dye DABCYL labelled on the catalyst hemin/G-quadruplex instead of the donor as the energy acceptor.

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quantitative analysis of enzymes such as phosphatase is important to understand a number of involved biological processes ranging from various metabolisms to signal transduction and cellular regulation. In this paper, a novel measurement strategy was proposed to detect alkaline phosphatase (ALP) activity in different locations within single living cells. The principle is based on the measurement of the resonance light scattering brightness ratio (SBR) per moving nanoparticle that forms in an ALP-related chemical reaction.

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The identification of molecular targets for achieving beneficial effects from small-molecule drugs is a crucial and currently unsolved challenge, which leads to high costs and long development cycles. Therefore, it is urgent to develop methods for easily and quickly acquiring information about protein-drug interaction at a molecular level. In this study, we propose a novel method for the study of protein-drug interaction by fluorescence correlation spectroscopy (FCS) based on organic solvent-induced protein aggregation.

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Protein phosphorylation is one of the most basic mechanisms for regulating and controlling protein biological activity and function, and it is also a very important posttranslational modification process. Protein phosphorylation participates in and regulates many life activities such as signal transduction, gene expression, cell cycle, and so on. In this paper, we propose a method for the determination of the protein phosphorylation combining capillary electrophoresis (CE) with ATP analog labeling technique.

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Scattering photon burst counting (SPBC) is a single-particle detection method, which is based on measuring scattering photon bursting of single nanoparticles through a detection volume of <1 fL. Although SPBC has been used for bioassays and analysis of nanoparticles, it is necessary to establish its theoretical model and develop a new detection mode in order to further enhance its sensitivity and enlarge its application fields. In this paper, we proposed a theoretical model for the confocal SPBC method and developed a novel SPBC detection mode using the fast objective scanning technique.

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Single-particle catalytic analysis plays an important role to understand the catalytic mechanism of nanocatalysts. Currently, some methods are used to study the relationship between single-particle catalytic activity and morphology. However, there is still lack of a simple and rapid analysis method for evaluating the catalytic activity of an individual nanocatalyst that freely moves in solution.

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Protein phosphorylation is a very important mechanism for regulating and controlling the activity and function of proteins, and is closely associated with signal transduction, gene expression, cell cycle and other life activities in organisms. In this paper, we proposed a new strategy for studying protein phosphorylation in living cells by combining fluorescence resonance energy transfer (FRET) with a small molecule adenosine 5'-triphosphate (ATP) analogue. We synthesized a new ATP analogue functionalized by norbornene (ATP-NB), and a tetrazine modified fluorescent probe Cyanine3 (TZ-Cy3).

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