Specific Protein Recognition Research Articles

Analyte-induced hindrance in the RCA-assisted CRISPR/Cas12a system for homogeneous protein assays

Heterogeneous assays, such as enzyme-linked immunosorbent assays, have become indispensable for in vitro diagnostics. However, the simple, sensitive, and accurate detection is limited by their multiple washing and incubation steps, and limited amplification methods. In this study, we design a novel approach utilizing analyte-induced hindrance within the rolling circle amplification (RCA)-assisted CRISPR/Cas12a system for simple and highly sensitive homogenous protein detection. Streptavidin (SA) and digoxin antibody (anti-Dig) are employed as representative detection models. The specific recognition of target proteins using primers modified with small molecules hinders the RCA process, preventing the activation of Cas12a′s trans-cleavage activity, thereby leading to a reduction in fluorescence intensity. Our developed platform exhibites exceptional detection performance characterized by high sensitivity, robust specificity, and significant potential for application in complex samples. By expanding the recognition elements, this platform can evolve into a versatile clinical diagnostic tool with universal applicability. In addition, this platform provides a novel direction for quantifying ultralow-concentration disease biomarkers in clinical practice.

A Bacterial Platform for Studying Ubiquitination Cascades Anchored by SCF-Type E3 Ubiquitin Ligases.

Ubiquitination is one of the most important post-translational modifications in eukaryotes. The ubiquitination cascade includes ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin ligases (E3). The E3 ligases, responsible for substrate recognition, are the most abundant and varied proteins in the cascade and the most studied. SKP1-CUL1-F-Box (SCF)-type E3 ubiquitin ligases are multi-subunit RING (Really Interesting New Gene) E3 ubiquitin ligases, composed of CUL1 (Cullin 1), RBX1 (RING BOX 1), SKP1 (S-phase Kinase-associated Protein 1), and F-box proteins. In vitro ubiquitination assays, used for studying the specific recognition of substrate proteins by E3 ubiquitin ligases, require the purification of all components involved in the cascade, and for assays with SCF-type E3 ligases, additional proteins (several SCF complex subunits). Here, the Duet expression system was used to co-express E1, E2, ubiquitin, ubiquitylation target (substrate), and the four subunits of a SCF-type E3 ligase in E. coli. When these proteins co-exist in bacterial cells, ubiquitination occurs and can be detected by Western Blot. The effectiveness of this bacterial system for detecting ubiquitination cascade activity was demonstrated by replicating both AtSCFTIR1-mediated and human SCFFBXO28-mediated ubiquitylation in bacteria. This system provides a basic but adaptable platform for the study of SCF-type E3 ubiquitin ligases.

Dual-Aptamer Recognition of DNA Logic Gate Sensor-Based Specific Exosomal Proteins for Ovarian Cancer Diagnosis.

Clinical diagnosis of ovarian cancer lacks high accuracy due to the weak selection of specific biomarkers along with the circumstance biomarkers localization. Clustering analysis of proteins transported on exosomes enables a more precise screening of effective biomarkers. Herein, through bioinformatics analysis of ovarian cancer and exosome proteomes, two coexpressed proteins, EpCAM and CD24, specifically enriched, were identified, together with the development of an as-derived dual-aptamer targeted exosome-based strategy for ovarian cancer screening. In brief, a DNA ternary polymer with aptamers targeting EpCAM and CD24 was designed to present a logic gate reaction upon recognizing ovarian cancer exosomes, triggering a rolling circle amplification chemiluminescent signal. A dynamic detection range of 6 orders of magnitude was achieved by quantifying exosomes. Moreover, for clinical samples, this strategy could accurately differentiate exosomes from healthy persons, other cancer patients, and ovarian cancer patients, enabling promising in situ detection. By accurately selecting biomarkers and constructing a dual-targeted exosomal protein detection strategy, the limitation of insufficient specificity of traditional protein markers was circumvented. This work contributed to the development of exosome-based prognosis monitoring in ovarian cancer through the identification of disease-specific exosome protein markers.

Binding equations for the lipid composition dependence of peripheral membrane-binding proteins

The specific recognition of peripheral membrane-binding proteins for their target membranes is mediated by a complex constellation of various lipid contacts. Despite the inherent complexities of the heterogeneous protein-membrane interface, the binding dependence of such proteins is, surprisingly, often reliably described by simple models such as the Langmuir Adsorption Isotherm or the Hill equation. However, these models were not developed to describe associations with two-dimensional, highly concentrated heterogeneous ligands such as lipid membranes. In particular, these models fail to capture the dependence on the lipid composition, a significant determinant of binding that distinguishes target from non-target membranes. In this work, we present a model that describes the dependence of peripheral proteins on lipid composition through an analytic expression for their association. The resulting membrane-binding equation retains the features of these simple models but completely describes the binding dependence on multiple relevant variables in addition to the lipid composition, such as protein and vesicle concentration. Implicit in this lipid composition dependence is a new form of membrane-based cooperativity that significantly differs from traditional solution-based cooperativity. We introduce the Membrane-Hill number as a measure of this cooperativity and describe its unique properties. We illustrate the utility and interpretational power of our model by analyzing previously published data on two peripheral proteins that associate with phosphatidylserine-containing membranes: The transmembrane immunoglobulin and mucin domain-containing protein 3 (TIM3) that employs calcium in its association, and milk fat globulin epidermal growth factor VIII (MFG-E8) which is completely insensitive to calcium. We also provide binding equations for systems that exhibit more complexity in their membrane-binding.

Effect of maleylation and denaturation of human serum albumin on its interaction with scavenger receptors.

The specific recognition of serum proteins by scavenger receptors is critical and fundamental in many biological processes. However, the underlying mechanism of scavenger receptor-serum protein interaction remains elusive. In this work, taking scavenger receptors class A1 (SR-A1) as an example, we systematically investigate its interaction with human serum albumin (HSA) at different states through a combination of molecular docking and all-atom molecular dynamics simulations. It is found that native HSA can moderately bind to collagen-like (CL) region or scavenger receptor cysteine-rich (SRCR) region, with both electrostatic (ELE) and van der Waals (VDW) interactions, playing important roles. After maleylation, the binding energy, particularly the ELE energy, between HSA and CL region is significantly enhanced, while the binding energy between HSA and SRCR region remains nearly unchanged. Additionally, we also observe that unfolding of the secondary structures in HSA leads to a larger contact surface area between denatured HSA and CL region, but has little impact on the HSA-SRCR region interaction. Therefore, similar to maleylated HSA, denatured HSA is also more likely to bind to the CL region of SR-A1.

Abstract 6350: Monoclonal antibody against BST2 isoform: potential tool for diagnostic and cancer therapy

Abstract BST2, a raft-associated type II transmembrane protein, functions as a restriction factor and inhibits HIV release by cross-linking virions onto infected cell surfaces. It also engages ILT7, a specific inhibitory receptor on plasmacytoid dendritic cells, which are associated with poor prognosis when infiltrate patients’ breast tumors. Two groups have identified BST2 isoforms of different lengths, generated by post-transcriptional modification. Based on these findings and our work on protein interaction of ILT7-BST2, we hypothesized that the expression of BST2 isoforms differed in normal and cancer tissues. To demonstrate that, we generated and characterized anti-long BST2 isoform monoclonal antibodies (mAbs). Results were compared with our previously developed mAb anti-BST2 full length molecule, 26F8, that recognizes a common epitope to all BST2 isoforms. By comparing the amino acid sequences of different isoforms of BST2, we identified a region of 24 residues on the extracellular domain of BST2, restricted to its long isoform. We then generated mAbs by hybridoma technology, immunizing BALB/c mice with the 24 mers peptide-KLH conjugated. Screening and positive selection of several clones were performed following our lab SOP. One of the mAbs, LA5, was selected based on positive ELISA against the immunogen and FACS staining of recombinant HEK293 cells expressing full-length BST2 protein. Pharmacokinetic determined using OCTET platform, revealed a KD of 4.61+/- 0.074 × 10−9 M for LA5. Epitope mapping of LA5 on BST2 overlapping peptides, confirmed specific recognition of full-length BST2 protein and the peptide used as immunogen. LA5 heavy and light chains were sequenced and analysis was performed by IgBlast and IMGTV. Binding of LA5 and 26F8 to the myeloma cell lines MM1 (B-lymphoblast) and U266 (B-lymphocyte) by flow cytometry, indicated 97-100% positive cells with both mAbs, with higher MFI values observed for clone 26F8: 5.8 and 1.8-fold-increase in MM1 and U266 cells respectively. IHC on formalin-fixed paraffin embedded tissues of human ductal breast carcinoma, revealed that LA5 staining was able to identify infiltrating carcinoma cells but not the normal surrounding acinar cells. In contrast, 26F8 staining did not discriminate between BST2+ malignant and surrounding normal acinar cells. Currently, we are analyzing a panel of >105 breast cancer tissue samples of different molecular classifications. Initial data revealed a high-level of expression of BST2 (by 26F8) on the epithelial area of the tumors, lower in the TME (tumor microenvironment-infiltrating immune cells) and almost negative expression in the surrounding fibroblasts rich stroma. Evaluation of IHC staining by LA5 is being processed and yet to be established. These IHC findings indicate a potential diagnostic value of LA5 to distinct between tumor and normal cells in patients’ specimens. Treatment prospects may arise during the process. Citation Format: Laura C. Bover, Ahmed Muhsin, Long T. Vien, Felipe Amaya Manzanares, Zhuang Wu, Janis D. Johnson, Diego Castro Reyes, Myrthala Moreno-Smith, Estefania Labanca, Irene Sorin, Silvia Saucedo, Silvina Gazzaniga, Alicia I. Bravo. Monoclonal antibody against BST2 isoform: potential tool for diagnostic and cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6350.

Role and Regulation of Clp Proteases: A Target against Gram-Positive Bacteria

Bacterial proteases participate in the proteolytic elimination of misfolded or aggregated proteins, carried out by members of the AAA+ protein superfamily such as Hsp100/Clp, Lon, and FtsH. It is estimated that the Clp and Lon families perform around 80% of cellular proteolysis in bacteria. These functions are regulated, in part, through the spatial and/or temporal use of adapter proteins, which participate in the recognition and delivery of specific substrate proteins to proteases. The proteolysis plays an important role in maintaining and controlling the quality of the proteins, avoiding the accumulation and aggregation of unfolded or truncated proteins. However, this is not their only function, since they play an important role in the formation of virulent phenotypes and in the response to different types of stress faced when entering the host or that occur in the environment. This review summarizes the structural and functional aspects of the Clp proteases and their role in Gram-positive microorganisms.

A Lambda-Exonuclease SELEX Method for Generating Aptamers to Bacterial Targets.

Nucleic acid aptamers are short sequences of single-stranded (ss) DNA or RNA that fold into a three-dimensional shape with useful binding properties. Traditionally, these properties have included specific recognition and binding of ions, small-molecules, proteins, and enzyme targets. Increasingly though, aptamers are being raised against complex subcellular or cellular targets. These broader-affinity aptamers can be usefully employed for detection, labeling, or therapeutic targeting of intact/living cells, whether prokaryotic or eukaryotic. Aptamers are usually developed from a random-sequence oligonucleotide library by repeated rounds of selection and amplification, a process named "systematic evolution of ligands by exponential enrichment" (SELEX). We describe here a widely applicable cell-SELEX method for raising aptamers against bacteria, using Escherichia coli strain HB101 as an example. Our cell-SELEX method uses a cycle of four stages: (1) incubation of a fluorescently labeled random-sequence ssDNA library with bacterial cells; (2) separation of cell-associated ssDNA from free ssDNA; (3) amplification of bound ssDNA by PCR, and (4) use of lambda-exonuclease to selectively regenerate ssDNA for further rounds of selection.

Calcium-Bound S100P Protein Is a Promiscuous Binding Partner of the Four-Helical Cytokines.

S100 proteins are multifunctional calcium-binding proteins of vertebrates that act intracellularly, extracellularly, or both, and are engaged in the progression of many socially significant diseases. Their extracellular action is typically mediated by the recognition of specific receptor proteins. Recent studies indicate the ability of some S100 proteins to affect cytokine signaling through direct interaction with cytokines. S100P was shown to be the S100 protein most actively involved in interactions with some four-helical cytokines. To assess the selectivity of the S100P protein binding to four-helical cytokines, we have probed the interaction of Ca2+-bound recombinant human S100P with a panel of 32 four-helical human cytokines covering all structural families of this fold, using surface plasmon resonance spectroscopy. A total of 22 cytokines from all families of four-helical cytokines are S100P binders with the equilibrium dissociation constants, Kd, ranging from 1 nM to 3 µM (below the Kd value for the S100P complex with the V domain of its conventional receptor, receptor for advanced glycation end products, RAGE). Molecular docking and mutagenesis studies revealed the presence in the S100P molecule of a cytokine-binding site, which overlaps with the RAGE-binding site. Since S100 binding to four-helical cytokines inhibits their signaling in some cases, the revealed ability of the S100P protein to interact with ca. 71% of the four-helical cytokines indicates that S100P may serve as a poorly selective inhibitor of their action.

Simple synthesis of PtRu nanoassemblies as signal amplifiers for electrochemical immunoassay of carbohydrate antigen 19–9

In clinical analysis, carbohydrate antigen 19–9 (CA199) is a gold standard for pancreatic cancer diagnosis. Herein, PtRu nanoassemblies (NAs) were synthesized via a facile one-step solvothermal approach, with the help of octylphenoxypolye thoxyethanol (NP-40) acted as a growth-directing molecule, and triethylene glycol (TEG) worked as a reductant and solvent. During the assembly process of small particles, a large number of voids were formed, which significantly increase the specific surface area of the PtRu NAs exhibiting excellent electrocatalytic performance. Incorporating the PtRu NAs as signal amplifiers for potassium ferrocyanide oxidation into the specific molecular recognition of proteins, a facile signal-enhanced electrochemical (EC) immunosensor was developed. Verified by a series of experiments, the proposed immunosensor presented a wide linear range (10−4–70 U mL−1) and a low detection limit (3.3 × 10−5 U mL−1), accompanied by good reproducibility, selectivity, and stability, which could be applied in human serum samples for the determination of CA199, and was comparable to commercial electrochemiluminescence (ECL) immunoassay. Feasibility of batch fabrication of PtRu NAs makes nanomaterial-based EC immunoassay promising for the determination of similar cancer markers in future.

Portable chemiluminescence optical fiber aptamer-based biosensors for analysis of multiple mycotoxins

Multiple mycotoxin contamination in foodstuffs causes significant threat to human health especially considering their synergistic effects. Herein, we present a novel chemiluminescence optical fiber aptamer-based biosensors for ultrasensitive on-site assay of multiplex mycotoxins in food samples. The optical fiber aptasensor is developed based on the specific recognition of single-stranded binding protein (SSB) and mycotoxin aptamers for the selective analysis. Optical fibers are utilized not only as the carrier to immobilize SSB to prepare the sensing region, but also as the transducer of the chemiluminescent emission to detect the sensor response. Multiple-channel fiber sensors are coupled together toward the detector and a compact and portable design of the chemiluminescence optical fiber aptasensor system is proposed, allowing four mycotoxins (AFB1, FB1, OTA or ZEN) to be simultaneously determined from one run without any tedious operation procedure. The optical fiber aptasensor system can perform sensitive analysis with a wide detection range from pg/mL to 105 pg/mL and low limit-of-detection in the range of 0.015 pg/mL-0.423 pg/mL for different target mycotoxins. The method is successfully applied for simultaneous and sensitive detection of multiple mycotoxins in infant cereals, showing its practical application in on-site analysis of real food samples.

Novel Ultrasensitive Photoelectrochemical Cytosensor Based on Hollow CdIn2S4/In2S3 Heterostructured Microspheres for HepG2 Cells Detection and Inhibitor Screening.

Hepatocellular carcinoma is a life-threatening malignant tumor found around the world for its high morbidity and mortality. Therefore, it is of great importance for sensitive analysis of liver cancer cells (HepG2 cells) in clinical diagnosis and biomedical research. To fulfill this demand, hollow CdIn2S4/In2S3 heterostructured microspheres (termed CdIn2S4/In2S3 for clarity) were prepared by a two-step hydrothermal strategy and applied for building a novel photoelectrochemical (PEC) cytosensor for ultrasensitive and accurate detection of HepG2 cells through specific recognition of CD133 protein on the cell surface with the respective aptamer. The optical properties of CdIn2S4/In2S3 were investigated by UV-vis diffuse reflectance spectroscopy (DRS) and PEC technology. By virtue of their appealing PEC characteristics, the resultant PEC sensor exhibited a wider dynamic linear range from 1 × 102 to 2 × 105 cells mL-1 with a lower limit of detection (LOD, 23 cells mL-1), combined by evaluating the expression level of CD133 protein stimulated by metformin as a benchmarked inhibitor. This work opens a valuable and feasible avenue for sensitive detection of diverse tumor cells, holding great potential in early clinical diagnosis and treatment coupled by screening inhibitors.

Theoretical insights into water network of B-DNA duplex with Watson-Crick and Hoogsteen base pairing geometries

Solvation is essential for the proper structure and functioning of biomolecules. It has a major role in establishing the B-form as the dominant structure of DNA and strongly affects its biological functions. In our genome, two modes of base pairing (Watson-Crick (WC) and Hoogsteen (HG)) exist in equilibrium and are related to the functional properties of the DNA including ligand recognition and gene regulation. Here, we use molecular dynamics simulation along with topological analysis of the H-bond network to investigate the hydration patterns of DNA structure with WC and HG base pairings. We showed that DNA most significantly disturbs the H-bonding properties of the first hydration shell and slightly the second shell compared to bulk water and that the water network is considerably different in the minor and major grooves. We found that HG base pairing leads to increased solvation of the major groove and a less ordered water structure in the minor groove accompanied with increasing hydrophobicity of the minor groove which could also contribute to the site recognition of specific DNA binding proteins. Our newly developed method to selectively study the solvation of the minor and major grooves opens the door to study in finer details the binding between various form of DNA and different ligands such drugs, RNA and proteins.

Hyperbranched Tetraphenylethylene Derivatives with Low Non-specific Aggregation-Induced Emission for Fluorescence Recognition of Proteins with Hydrophobic Pockets.

Proteins play an important role in the physiological process of many organisms, and their abnormal level often indicates the occurrence of some diseases. Therefore, protein analysis has important reference value and clinical significance for early diagnosis and therapy of disease. Using human serum albumin (HSA) as a model protein, a series of super-branched tetraphenylethylene (TPE) derivatives with different branching structures and terminal groups are reported herein for highly sensitive and specific recognition of proteins with hydrophobic cages. Benefiting from the hyperbranched structures, these probes showed much higher critical micelle concentrations (CMCs) than most linear TPE-based amphiphilic molecules since the hyperbranched structure not only improved their solubility but also amplified the steric hindrance effect and electrostatic repulsive force to prevent their aggregation. Dynamic light scattering experiments proved that these probes formed dense aggregates at CMC, and such aggregate structures would lead to a higher background fluorescence noise. Hence, a higher CMC is more conducive to the detection of the target with low backgrounds. Among them, P3-COOH with -COOH as the terminal unit and a relatively longer branch showed the highest CMC and the best signal to background ratio (S/N). Mechanism studies showed that P3-COOH was bound to HSA mainly through a hydrophobic force, resulting in a limited P3-COOH molecular movement and less attack from quenchers in solutions, thus leading to greatly enhanced fluorescence intensity. In addition, P3-COOH was also applied to the determination of HSA content in actual human serum samples.

One-Step Synthesis of Sustainable Montmorillonite-Supported, Copper-Doped Magnetic Nanoparticles for Highly Specific Separation of His-Rich Proteins

Immobilized metal affinity (IMA) magnetic adsorbents exhibit an exciting preference for histidine (His)-rich proteins, whereas their application was limited due to the leaching of copper ions and poor dispersibility, greatly influencing their sustainability and adsorption performance. Herein, we propose a novel IMA adsorbent based on montmorillonite (MMT)-supported, copper-doped magnetic nanoparticles (Fe3O4−Cu/MMT) for highly specific recognition and separation of His-rich proteins. In the process, Fe3O4−Cu/MMT nanomaterials were synthesized by a one-step solvothermal method. The obtained adsorbents exhibit enhanced adsorption capacity (758.7 mg g–1) and selectivity (SF < 0.2) toward bovine hemoglobin (BHb) as a model derived from good dispersity, making more anchor sites exposed. Also, the adsorbent can be facilely regenerated with negligible leakage of copper ions and no need for re-incubation in a metal salt solution, maintaining high performance for six cycles. Furthermore, bovine blood was opted as a realistic specimen for evaluating the adsorption capability of the proposed adsorbent, emphasizing its good practicality for His-rich protein separation.

A graphdiyne-based protein molecularly imprinted biosensor for highly sensitive human C-reactive protein detection in human serum

• A graphdiyne-based protein molecularly imprinted biosensor was developed. • The biosensor achieved a highly sensitive detection towards C-reactive protein. • Graphdiyne with high conductivity and biocompatibility was utilized for biosensor. • Developed biosensor achieved target recognition in complex biological samples. • The biosensor exhibited excellent antifouling capability. Traditional protein molecularly imprinted polymers (MIPs) are used to develop biosensors for highly specific protein recognition based on generated three-dimensional cavities that are completely complementary to the imprinted template molecules. As a new generation of artificial identification probes, protein MIPs can realize the recognition specificity, but the analytical sensitivity and limit of detection (LOD) are not optimal. Here, a highly sensitive protein MIPs biosensor was constructed, in which conductive and biocompatible graphdiyne (GDY) nanosheets, antifouling and specific MIPs were combined, to achieve the highly sensitive and selective recognition of human C-reactive protein. Dopamine, owing to its simple polymerization procedure and the verified low fouling property of polydopamine, was used as the functional monomer to form steady complex with the template molecule through hydrogen bonding and multipoint electrostatic attraction. GDY with high biocompatibility and conductivity was independently synthesized and initially introduced into the C reactive protein imprinted polymers (C-MIPs) to enhance the electrochemical response and provide a suitable microenvironment for the bioactive protein molecules. In addition to the highly specific MIPs, antifouling material was also utilized to further improve the recognition selectivity. Herein, our developed C-MIPs biosensor performed with a wider linear detection range from 10 −5 to 10 3 ng/mL and the LOD was found to be 0.41 × 10 −5 ng/mL. Moreover, the C-MIPs biosensor showed excellent selectivity, reversibility and reusability, a short rebinding time, and long-term stability. Notably, the developed C-MIPs biosensor performed well even in complex serum samples without discernible signal suppression, indicating its good antifouling ability, as well as high sensitivity and selectivity. The developed C-MIPs biosensor behaved well in human blood samples, declaring its potential practical application capability.

Sequence Does Not Matter: The Biomedical Applications of DNA-Based Coatings and Cores.

Biomedical applications of DNA are diverse but are usually associated with specific recognition of target nucleotide sequences or proteins and with gene delivery for therapeutic or biotechnological purposes. However, other aspects of DNA functionalities, like its nontoxicity, biodegradability, polyelectrolyte nature, stability, thermo-responsivity and charge transfer ability that are rather independent of its sequence, have recently become highly appreciated in material science and biomedicine. Whereas the latest achievements in structural DNA nanotechnology associated with DNA sequence recognition and Watson–Crick base pairing between complementary nucleotides are regularly reviewed, the recent uses of DNA as a raw material in biomedicine have not been summarized. This review paper describes the main biomedical applications of DNA that do not involve any synthesis or extraction of oligo- or polynucleotides with specified sequences. These sequence-independent applications currently include some types of drug delivery systems, biocompatible coatings, fire retardant and antimicrobial coatings and biosensors. The reinforcement of DNA properties by DNA complexation with nanoparticles is also described as a field of further research.

Nanozyme Sensor Array Plus Solvent-Mediated Signal Amplification Strategy for Ultrasensitive Ratiometric Fluorescence Detection of Exosomal Proteins and Cancer Identification.

Tumor exosomes with molecular marker-proteins inherited from their parent cells have emerged as a promising liquid biopsy biomarker for cancer diagnosis. However, facile, robust, and sensitive detection of exosomal proteins remains challenging. Therefore, a nanozyme sensor array is constructed by using aptamer-modified C3N4 nanosheets (Apt/C3N4 NSs) together with a solvent-mediated signal amplification strategy for ratiometric fluorescence detection of exosomal proteins. Three aptamers specific to exosomal proteins are selected to construct Apt/C3N4 NSs for high specific recognition of exosomal proteins. The adsorption of aptamers enhances the catalytic activity of C3N4 NSs as a nanozyme for oxidation of o-phenylenediamine (oPD) to 2,3-diaminophenazine (DAP). In the presence of target exosomes, the strong affinity between aptamer and exosome leads to the disintegration of Apt/C3N4 NSs, resulting in a decrease of catalytic activity, thereby reducing the production of DAP. The ratiometric fluorescence signal based on a photoinduced electron transfer (PET) effect between DAP and C3N4 NSs is dependent on the concentration of DAP generated, thus achieving highly facile and robust detection of exosomal proteins. Remarkably, the addition of organic solvent-1,4-dioxane can sensitize the luminescence of DAP without affecting the intrinsic fluorescence of C3N4 NSs, achieving the amplification of the aptamer-exosome recognition events. The detection limit for exosome is 2.5 × 103 particles/mL. In addition, the accurate identification of cancer can be achieved by machine learning algorithms to analyze the difference of exosomal proteins from different patients' blood. We hope that this facile, robust, sensitive, and versatile nanozyme sensor array would become a promising tool in the field of cancer diagnosis.

Specific recognition of protein by deep eutectic solvent-based magnetic β-cyclodextrin molecularly imprinted polymer.

Amagnetic β-cyclodextrin (MCD) surface molecularly imprinted polymer (MIP) based on deep eutectic solvents (DESs) as cross-linker and functional monomer (MCD@DES-MIP) was successfully synthesized for the specific recognition of bovine hemoglobin (BHb). The adsorption behavior of MCD@DES-MIP for BHb was investigated by adsorption thermodynamics, adsorption kinetics, and pH control experiments. The maximum adsorption capacity of MCD@DES-MIP for BHb under the optimized conditions was 195.94mgg-1 and the imprinting factor was 4.68. In addition, the competitive adsorption experiments demonstrated that MCD@DES-MIP showed excellent selective extraction ability for BHb in the binary mixture of BHb and bovine serum albumin (BSA). The actual sample analysis manifested that MCD@DES-MIP effectively separated BHb from complex samples. The results of circular dichroism spectra proved that the secondary structure of BHb did not change during elution. The result indicated that MCD@DES-MIP can be used as a new imprinting material for the separation and purification of BHb.Graphical abstract Magnetic imprinted microspheres (MCD@DES-MIP) were prepared by free radical polymerization using magnetic β-cyclodextrin (MCD) as carrier, deep eutectic solvents (DESs) as functional monomer and cross-linker. MCD@DES-MIP show high adsorption capacity and excellent selectivity for BHb.

Recent insight into the role of RING-finger E3 ligases in glioma.

The ubiquitin proteasome system (UPS) serves as the major posttranslational modification system for the maintenance of protein homeostasis. The ubiquitin ligases (E3s) are responsible for the recognition and recruitment of specific substrate proteins for polyubiquitination. Really interesting new gene (RING) finger E3s account for the majority of E3s. The human genome encodes more than 600 RING E3s, which are divided into three subclasses: single polypeptide E3s, cullin-RING ligases (CRLs) and other multisubunit E3s. The abnormal regulation of RING E3s has been reported to disrupt normal biological processes and induce the occurrence of many human malignancies. Glioma is the most common type of malignant primary brain tumor. In the last few decades, patient prognosis has improved as novel targeted therapeutic agents have developed. In this review, we will summarize the current knowledge about the dysregulation of RING E3s and the altered stability of their substrates in glioma. We will further introduce and discuss the current status and future perspectives of the application of small inhibitors and proteolysis-targeting chimeric molecules (PROTACs) interfering with RING E3s as potential anticancer agents for glioma.