Cross-linking Reagent Research Articles

The Efficiency of Polyester-Polysulfone Membranes, Coated with Crosslinked PVA Layers, in the Water Desalination by Pervaporation.

Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)-using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‱, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm3/h while the membrane area was 0.005 m2. The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method.

Cell fixation improves performance of in situ crosslinking mass spectrometry while preserving cellular ultrastructure

Crosslinking mass spectrometry (XL-MS) has the potential to map the interactome of the cell with high resolution and depth of coverage. However, current in vivo XL-MS methods are hampered by crosslinkers that demonstrate low cell permeability and require long reaction times. Consequently, interactome sampling is not high and long incubation times can distort the cell, bringing into question the validity any protein interactions identified by the method. We address these issues with a fast formaldehyde-based fixation method applied prior to the introduction of secondary crosslinkers. Using human A549 cells and a range of reagents, we show that 4% formaldehyde fixation with membrane permeabilization preserves cellular ultrastructure and simultaneously improves reaction conditions for in situ XL-MS. Protein labeling yields can be increased even for nominally membrane-permeable reagents, and surprisingly, high-concentration formaldehyde does not compete with conventional amine-reactive crosslinking reagents. Prefixation with permeabilization uncouples cellular dynamics from crosslinker dynamics, enhancing control over crosslinking yield and permitting the use of any chemical crosslinker.

Isolation of chitosan-melanin complex from black soldier fly adults and obtaining nanofibrous materials based on it

The article presents the results of studying the viscosity of chitosan-melanin complex solutions from the larvae of the insect Hermetia illucens and the process of gelation in these solutions in the presence of crosslinking reagents. Chemically cross-linked nanofibers were obtained from solutions of the chitosan-melanin complex in dilute solutions of acetic acid by the method of spinneretless electrospinning. The presence of 14% melanin made it possible to reduce the concentration of acetic acid in the spinning composition.

Examining NF-κB genomic interactions by ChIP-seq and CUT&Tag.

An understanding of the mechanisms and logic by which transcription factors coordinate gene regulation requires delineation of their genomic interactions at a genome-wide scale. Chromatin immunoprecipitation-sequencing (ChIP-seq) and more recent techniques, including CUT&Tag, typically reveal thousands of genomic interactions by transcription factors, but without insight into their functional roles. Due to cost and time considerations, optimization of ChIP experimental conditions is typically carried out only with representative interaction sites rather than through genome-wide analyses. Here, we describe insights gained from the titration of two chemical crosslinking reagents in genome-wide ChIP-seq experiments examining two members of the NF-κB family of transcription factors: RelA and c-Rel. We also describe a comparison of ChIP-seq and CUT&Tag. Our results highlight the large impact of ChIP-seq experimental conditions on the number of interactions detected, on the enrichment of consensus and non-consensus DNA motifs for the factor, and on the frequency with which the genomic interactions detected are located near potential target genes. We also found considerable consistency between ChIP-seq and CUT&Tag results, but with a substantial fraction of genomic interactions detected with only one of the two techniques. Together, the results demonstrate the dramatic impact of experimental conditions on the results obtained in a genome-wide analysis of transcription factor binding, highlighting the need for further scrutiny of the functional significance of these condition-dependent differences.

Trioxane-based MS-cleavable Cross-linking Mass Spectrometry for Profiling Multimeric Interactions of Cellular Networks.

Cross-linking mass spectrometry (XL-MS) is a powerful technology for mapping protein-protein interactions (PPIs) at the systems-level. By covalently connecting pairs of proximal residues, cross-linking reagents provide distance restraints to infer protein conformations and interaction interfaces. While binary cross-links have been remarkably informative, multimeric cross-links can offer enhanced spatial resolution to facilitate the characterization of dynamic and heterogeneous protein complexes. However, the identification of multimeric cross-links remains extremely challenging due to fragmentation complexity and the vast expansion of database search space. Here, we present a novel trioxane-based MS-cleavable homotrifunctional cross-linker TSTO, which can target three proximal lysine residues simultaneously. Owing to its unique structure and MS-cleavability, TSTO enables fast and unambiguous identification of cross-linked peptides using LC-MS n analysis. Importantly, we have demonstrated that the TSTO-based XL-MS platform is effective for mapping PPIs of protein complexes and cellular networks. The trimeric interactions captured by TSTO have uncovered new structural details that cannot be easily revealed by existing reagents, allowing in-depth description of PPIs to facilitate structural modeling. This development not only advances XL-MS technologies for global PPI profiling from living cells, but also offers a new direction for creating multifunctional MS-cleavable cross-linkers to further push structural systems biology forward in the future.

Injectable Dual Fenton/Enzymatically Cross-Linked Double-Network Hydrogels Based on Acrylic/Phenolic Polymers with Highly Reinforced and Tunable Mechanical Properties.

Injectable hydrogels have been extensively used as promising therapeutic scaffolds for a wide range of biomedical applications, such as tissue regeneration and drug delivery. However, their low fracture toughness and brittleness often limit their scope of application. Double-network (DN) hydrogel, which is composed of independently cross-linked rigid and ductile polymer networks, has been proposed as an alternative technique to compensate for the weak mechanical properties of hydrogels. Nevertheless, some challenges still remain, such as the complicated and time-consuming process for DN formation, and the difficulty in controlling the mechanical properties of DN hydrogels. In this study, we introduce a simple, rapid, and controllable method to prepare in situ cross-linkable injectable DN hydrogels composed of acrylamide (AAm) and 4-arm-PPO-PEO-tyramine (TTA) via dual Fenton- and enzyme-mediated reactions. By varying the concentration of Fenton's reagent, the DN hydrogels were rapidly formed with controllable gelation rate. Importantly, the DN hydrogels showed a 13-fold increase in compressive strength and a 14-fold increase in tensile strength, compared to the single network hydrogels. The mechanical properties, elasticity, and plasticity of DN hydrogels could also be modulated by simply varying the preparation conditions, including the cross-linking density and reagent concentrations. At low cross-linker concentration (<0.05 wt %), the plastic DN hydrogel stretched to over 6,500%, whereas high cross-linker concentration (≥0.05 wt %) induced fully elastic hydrogels, without hysteresis. Besides, DN hydrogels were endowed with rapid self-recovery and highly enhanced adhesion, which can be further applied to wearable devices. Moreover, human dermal fibroblasts treated with DN hydrogels retained viability, demonstrating the biocompatibility of the cross-linking system. Therefore, we expect that the dual Fenton-/enzyme-mediated cross-linkable DN hydrogels offer great potential as advanced biomaterials applied for hard tissue regeneration and replacement.

Interpenetrating Polymer Network Capturing FRET-Sensitive Polymers Available for an Enzyme Assay.

Fluorogenic glycomonomers have been used for biological evaluations, and water-soluble and Förster resonance energy transfer (FRET)-sensitive glycopolymers have also been reported. A FRET-sensitive polymer was conveniently prepared from a fluorogenic donor monomer and a fluorogenic acceptor monomer by means of simple radical polymerization in high yield. Continuous fluorospectroscopic monitoring of the polymer in the presence of an enzyme was performed, and the results showed the possible application of the FRET-sensitive glycopolymer for practical use. In addition to the use of aqueous solution phase, the water-soluble and FRET-sensitive glycopolymer was completely captured into an interpenetrating polymer network (IPN) by means of radical polymerization with a combination of acrylamide and bis-acrylamide as used for the cross-linking reagent system. The IPN including the FRET-sensitive glycopolymer was allowed to react with amylases in an aqueous buffer solution at 37 °C, and the enzymatic reaction was continuously and conveniently monitored by means of fluorometric spectroscopy.

Salt-responsive polyamide thin-film nanocomposite membrane based on zwitterionic polymeric nanoparticles for high-efficient dye desalination

To simultaneously improve the water permeability, selectivity, and antifouling properties of polyamide nanofiltration (NF) membranes in textile wastewater treatment, we fabricated a salt-responsive thin-film nanocomposite (TFN) membrane with the incorporation of zwitterionic polymeric nanoparticles (ZNPs) into polyamide selective layer. Herein, the ZNPs were synthesized via an inverse miniemulsion polymerization with zwitterionic monomer, amino monomer, and cross-linker reagent. The salt-responsive property of ZNPs rendered their resultant membranes TFN-ZNPs with adjustable microstructure and separation performance via varying the sodium chloride (NaCl) concentration in water. The water permeance of TFN-ZNPs was enhanced to be 1.7 times that of its pure water permeance with the 10 g L−1 NaCl solution, and the salt-responsive behavior was reversible. Moreover, this salt-responsive property endowed the membrane with outstanding separation performance for the salt/dye or dye/dye mixtures. The selectivity of TFN-ZNPs to NaCl/congo red and methyl orange/neutral blue was enhanced to ∼104 and ∼127, respectively. The TFN-ZNPs with salt-responsive property also exhibited an improved antifouling performance, i.e., the flux recovery ratio was enhanced from 85.6 % to 96.5 % by washing with NaCl solution instead of deionized water. Thus, this work provided a paradigm shift in the fabrication of salt-responsive TFN membranes for the highly efficient separation of organic molecules and inorganic salts and wastewater treatment.

Silk fibroin-graphene oxide composite membranes for selective separation of ions and molecules from water

Nanofiltration membranes with controlled pores are useful in many fields, such as pharmaceuticals, desalination, petroleum, and food processing. Recently, graphene oxide has emerged as a promising candidate for the fabrication of highly efficient and pressure-resistant nanofiltration membranes with excellent water permeability and solute rejection. However, it remains difficult to achieve increased permeability while maintaining excellent separation ability. Herein, we report a novel silk fibroin-graphene oxide (FGO) composite membrane prepared by using fibroin as a cross-link reagent, which is extracted from natural Bombyx mori silkworm cocoons. Such a FGO membrane shows a pure water permeance of ∼280 L m−2 h−1 bar−1, which is five times greater than previously reported GO-based membranes. Further, such a membrane also exhibits excellent separation efficiency (> 99 %) for different feed molecules. Additionally, these membranes exhibit high chemical stability in water, acidic and basic solutions for several days compared to pristine GO membranes.

High-Performance Workflow for Identifying Site-Specific Crosslinks Originating from a Genetically Incorporated, Photoreactive Amino Acid.

In conventional crosslinking mass spectrometry, proteins are crosslinked using a highly selective, bifunctional chemical reagent, which limits crosslinks to residues that are accessible and reactive to the reagent. Genetically incorporating a photoreactive amino acid offers two key advantages: any site can be targeted, including those that are inaccessible to conventional crosslinking reagents, and photoreactive amino acids can potentially react with a broad range of interaction partners. However, broad reactivity imposes additional challenges for crosslink identification. In this study, we incorporate benzoylphenylalanine (BPA), a photoreactive amino acid, at selected sites in an intrinsically disordered region of the human protein HSPB5. We report and characterize a workflow for identifying and visualizing residue-level interactions originating from BPA. We routinely identify 30 to 300 crosslinked peptide spectral matches with this workflow, which is up to ten times more than existing tools for residue-level BPA crosslink identification. Most identified crosslinks are assigned to a precision of one or two residues, which is supported by a high degree of overlap between replicate analyses. Based on these results, we anticipate that this workflow will support the more general use of genetically incorporated, photoreactive amino acids for characterizing the structures of proteins that have resisted high-resolution characterization.

Effects of Laccase and Transglutaminase on the Physicochemical and Functional Properties of Hybrid Lupin and Whey Protein Powder.

Plant-based protein is considered a sustainable protein source and has increased in demand recently. However, products containing plant-based proteins require further modification to achieve the desired functionalities akin to those present in animal protein products. This study aimed to investigate the effects of enzymes as cross-linking reagents on the physicochemical and functional properties of hybrid plant- and animal-based proteins in which lupin and whey proteins were chosen as representatives, respectively. They were hybridised through enzymatic cross-linking using two laccases (laccase R, derived from Rhus vernicifera and laccase T, derived from Trametes versicolor) and transglutaminase (TG). The cross-linking experiments were conducted by mixing aqueous solutions of lupin flour and whey protein concentrate powder in a ratio of 1:1 of protein content under the conditions of pH 7, 40 °C for 20 h and in the presence of laccase T, laccase R, or TG. The cross-linked mixtures were freeze-dried, and the powders obtained were assessed for their cross-linking pattern, colour, charge distribution (ζ-potential), particle size, thermal stability, morphology, solubility, foaming and emulsifying properties, and total amino acid content. The findings showed that cross-linking with laccase R significantly improved the protein solubility, emulsion stability and foaming ability of the mixture, whereas these functionalities were lower in the TG-treated mixture due to extensive cross-linking. Furthermore, the mixture treated with laccase T turned brownish in colour and showed a decrease in total amino acid content which could be due to the enzyme's oxidative cross-linking mechanism. Also, the occurrence of cross-linking in the lupin and whey mixture was indicated by changes in other investigated parameters such as particle size, ζ-potential, etc., as compared to the control samples. The obtained results suggested that enzymatic cross-linking, depending on the type of enzyme used, could impact the physicochemical and functional properties of hybrid plant- and animal-based proteins, potentially influencing their applications in food.

Satisfactory Tensile Strength and Strain of Recyclable Polyurethane with a Trimaleimide Structure for Thermal Self-Healing and Anticorrosive Coatings.

Bismaleimide (BMI) is often used as the cross-linking reagent in Diels-Alder (D-A)-type intrinsic self-healing materials (DISMs) to promote the connectivity of damaged surfaces based on reversible D-A bond formation on the molecular scale. Until now, although DISMs have exhibited great potential in the applications of various sensors, electronic skin, and artificial muscles, it is still difficult to prepare DISMs with satisfactory self-healing abilities and high tensile strengths and strains at the same time, thus largely limiting their applications in self-healing anticorrosive coatings. Herein, symmetrical trimaleimide (TMI) was successfully synthesized, and trimaleimide-structured D-A self-healing polyurethane (TMI-DA-PU) was prepared via the reversible D-A reaction (cycloaddition of furan and maleimide). As a DISM, TMI-DA-PU exhibits apparently higher self-healing efficiency (98.7%), tensile strength (25.4 MPa), and strain (1378%) compared to bismaleimide-structured D-A self-healing polyurethane (BMI-DA-PU) (self-healing efficiency, 90.2%; tensile strength, 19.3 MPa; strain, 1174%). In addition, TMI-DA-PU shows a high recycling efficiency (>95%) after 4 cycles of recycling. A series of characterizations indicate that TMI provides more monoene rings as the self-healing sites, forms denser cross-linked structures compared to BMI, and is, thus, more appropriate to be used for DISM applications. Moreover, the barrier abilities of coatings can be semi-quantitatively expressed by the impedance value at 0.01 Hz (|Z|0.01Hz). The |Z|0.01 Hz value of the TMI-DA-PU coating is 3.93 × 109 Ω cm2 on day 0, which is significantly higher than that of the BMI-DA-PU coating (6.76 × 108 Ω cm2 on day 0), indicating that the denser rigid cross-linked structure of TMI results in the small porosity in the TMI-DA-PU coating, thus effectively improving the anticorrosion performance. The construction of DISMs with the structure of TMI demonstrates immense potential in self-healing anticorrosive coatings.

Droplet Microfluidics-Assisted Fabrication of Shape Controllable Iron-Alginate Microgels with Fluorescent Property.

Droplet-based microfluidics-assisted fabrication of alginate microgels has extensive applications in biomaterials, biomedicines, and related fields. This approach is typically achieved by crosslinking droplets of an aqueous solution of sodium alginate with various divalent and trivalent ions, such as Ca2+, Ba2+, Sr2+, etc. Despite the exceptional features exhibited by bulk alginate hydrogels when using iron ions as the crosslinking reagent, including stimulus responsiveness and complex chemistry, no attention has been given to studying the fabrication of Fe-alginate microgels through droplet microfluidics. In this work, a facile method is presented for fabricating Fe-alginate microgels using single emulsion droplets as templates and an off-chip crosslinking technique to solidify the droplets. The morphologies of the resulting microgels can be systematically adjusted by manipulating different parameters such as viscosities and ionic strength of the collecting solutions. It should be noted that these resulting microgels undergo a color change from light brown to dark brown due to presumed self-oxidation of iron ions within their skeleton structure. Furthermore, these Fe-alginate microgels are functionalized by decorating them with a positively charged linear polymer via electrostatic interactions to impart them with stable fluorescent property. These functionalized Fe-alginate microgels may find potential applications in drug delivery carriers and biomimetic structures.

Biogenic crocetin-crosslinked chitosan nanoparticles with high stability and drug loading for efficient radioprotection

The risk of radiation exposure increases with the development of nuclear energy and technology, and radiation protection receives more and more attention from public health and safety. However, the numerous adverse effects and low drug utilization limit the practical applications of radioprotective agents. In this study, we developed a biogenic crocetin-crosslinked chitosan nanoparticle with high stability and drug loading for efficient radioprotection. In detail, the nanoparticles were prepared using the natural antioxidant crocetin as a cross-linking reagent in amidation reactions of chitosan and mPEG-COOH. The nanoparticles exhibit a quick scavenging ability for common reactive oxygen species and reactive nitrogen in vitro. Meanwhile, cellular experiments demonstrate the good biocompatibility of the nanoparticles and the alleviation of radiation damage by scavenging reactive oxygen species, reducing apoptosis, and inhibiting DNA damage, etc. Importantly, the nanoparticles are effective in mitigating oxidative damage in major organs and maintaining peripheral blood cell content. In addition, they perform better radioprotective properties than free drug due to the significant extension of the blood half-life of crocetin in vivo from 10 min to 5 h. This work proposes a drug-crosslinking strategy for the design of a highly efficient radioprotective agent, which exhibits a promising prospect in the fields of nuclear emergency and public health.

A Transparent and Injectable Biomaterial Prepared by Mixing Collagen and Anti-Cancer Platinum Derivatives.

This study presents the synthesis of a cross-linked collagen material, named platinum-containing collagen gel (PCG), which is achieved by simply mixing collagen and derivatives of an anti-cancer platinum complex. The cross-linking reagents are derivatives of cisplatin or transplatin, generated through a ligand exchange with dimethyl sulfoxide. PCG exhibits superior physical strength and transparency compared with the native collagen gel formed through spontaneous fibril formation. The versatility of PCG as a cell culture scaffold, applicable to both 2D and 3D models, with low cytotoxicity is demonstrated. Furthermore, PCG exhibits pH-responsive gel-forming properties. This enables the removal of free cross-linker by dialysis in an acidic solution and subsequent gel formation upon neutralization. This material holds promise for application in cell culture scaffolds and medical injections.

Enzymatic Protein Immobilization for Nanobody Array.

Antibody arrays play a pivotal role in the detection and quantification of biomolecules, with their effectiveness largely dependent on efficient protein immobilization. Traditional methods often use heterobifunctional cross-linking reagents for attaching functional residues in proteins to corresponding chemical groups on the substrate surface. However, this method does not control the antibody's anchoring point and orientation, potentially leading to reduced binding efficiency and overall performance. Another method using anti-antibodies as intermediate molecules to control the orientation can be used but it demonstrates lower efficiency. Here, we demonstrate a site-specific protein immobilization strategy utilizing OaAEP1 (asparaginyl endopeptidase) for building a nanobody array. Moreover, we used a nanobody-targeting enhanced green fluorescent protein (eGFP) as the model system to validate the protein immobilization method for building a nanobody array. Finally, by rapidly enriching eGFP, this method further highlights its potential for rapid diagnostic applications. This approach, characterized by its simplicity, high efficiency, and specificity, offers an advancement in the development of surface-modified protein arrays. It promises to enhance the sensitivity and accuracy of biomolecule detection, paving the way for broader applications in various research and diagnostic fields.

Efficacy and tolerability of Profhilo® Structura intended to restore lateral cheek fat compartment: An observational pilot study.

Hyaluronic acid (HA)-based injections are used worldwide to improve skin defects associated with aging and ultraviolet light/environmental exposure. HA formulations developed according to molecular weight or with additional components, for example, cross-linking reagents, are limited by their low biological activity and concentration limit. NAHYCO™ technology has enabled the production of hybrid cooperative complexes (HCCs) of low and high molecular weight HA. Developed for injection into the fat compartments of the face and previously demonstrating potential benefits for adipose tissue restoration, Profhilo Structura® is a new 2 mL HCC formulation comprising low molecular weight HA (45 mg/mL) and high molecular weight HA (45 mg/mL). To evaluate the efficacy and tolerability of Profhilo Structura® to restore adipose tissue compartments in the lateral cheek fat compartment. Fifty healthy enrolled subjects received two injections, 1 month apart, and were evaluated 3 months posttreatment. Investigators performed clinical evaluations (Facial Volume Loss Scale [FVLS] and Wrinkle Severity Rating Scale [WSRS]) at different time points. Subjects also completed self-evaluation assessments following treatment. A significant improvement in FVLS and WSRS clinical scores after the first treatment was observed; treatment benefit was maintained 3 months after treatment completion and confirmed by subject self-assessment. Most participants reported an improvement, particularly a marked reduction of wrinkles and increased skin firmness. No serious adverse events were reported, confirming the excellent safety profile of HCC injectable devices. Overall, the study highlighted the efficacy and tolerability of the studied medical device proving its effect on adipose tissue.

Fabrication of a surface molecularly imprinted polymer membrane based on a single template and its application in the separation and extraction of phenytoin, phenobarbital and lamotrigine.

An innovative molecularly imprinted polymer membrane (MIPM) was prepared with polyvinylidene difluoride (PVDF) as the support, phenytoin (PHT) as the single template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linking reagent, azobisisobutyronitrile as the initiator, and acetonitrile-dimethylformamide (1 : 1.5, v/v) as the porogen. These materials were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller measurements and X-ray photoelectron spectroscopy. Their adsorption performances were evaluated through a series of experiments including isothermal adsorption, kinetic adsorption, selective adsorption, adsorption-desorption, reusability, and preparation reproducibility. Additionally, the application was explored by investigating the extraction recovery of MIPMs towards PHT, phenobarbital (PHB) and lamotrigine (LTG) in different matrices including methanol, normal saline (NS), phosphate buffer solution (PBS) and plasma. The results showed that MIPMs with rough and porous surfaces were successfully constructed, which offered good preparation reproducibility, reusability and selectivity. The adsorption capacities of MIPMs towards PHT, PHB and LTG were 2.312, 2.485 and 2.303 mg g-1, respectively, while their corresponding imprinting factors were 8.538, 12.122 and 4.562, respectively. The adsorption equilibrium of MIPMs was achieved within 20 min at room temperature without stirring or ultrasonication. The extraction recoveries of MIPMs for PHT, PHB or LTG in methanol, NS and PBS were more than 80% with an RSD% value of less than 3.64. In the case of plasma, the extraction recovery of MIPMs for PHT and PHB was more than 80% with an RSD% value of less than 2.41, while that of MIPMs for LTG was more than 65% with an RSD% value of less than 0.99. All the results indicated that the preparation method for MIPMs was simple, stable, and reliable, and the prepared MIPMs possessed excellent properties to meet the extraction application of PHT, PHB and LTG in different matrices.

Advances in crosslinking chemistry and proximity-enabled strategies: deciphering protein complexes and interactions.

Mass spectrometry, coupled with innovative crosslinking techniques to decode protein conformations and interactions through uninterrupted signal connections, has undergone remarkable progress in recent years. It is crucial to develop selective crosslinking reagents that minimally disrupt protein structure and dynamics, providing insights into protein network regulation and biological functions. Compared to traditional crosslinkers, new bifunctional chemical crosslinkers exhibit high selectivity and specificity in connecting proximal amino acid residues, resulting in stable molecular crosslinked products. The conjugation with specific amino acid residues like lysine, cysteine, arginine and tyrosine expands the XL-MS toolbox, enabling more precise modeling of target substrates and leading to improved data quality and reliability. Another emerging crosslinking method utilizes unnatural amino acids (UAAs) derived from proximity-enabled reactivity with specific amino acids or sulfur-fluoride exchange (SuFEx) reactions with nucleophilic residues. These UAAs are genetically encoded into proteins for the formation of specific covalent bonds. This technique combines the benefits of genetic encoding for live cell compatibility with chemical crosslinking, providing a valuable method for capturing transient and weak protein-protein interactions (PPIs) for mapping PPI coordinates and improving the pharmacological properties of proteins. With continued advancements in technology and applications, crosslinking mass spectrometry is poised to play an increasingly significant role in guiding our understanding of protein dynamics and function in the future.

Highly efficient mica-incorporated graphene oxide-based membranes for water purification and desalination.

Graphene oxide (GO) has become the most attractive material for membrane technology owing to its potential application as a nanofiller in water treatment, purification, and desalination. In this study, we incorporated mica as a cross-linking reagent to increase the interlayer spacing and stability of GO sheets and fabricated a mica/GO (MGO) membrane for the first time. The MGO membrane (260 ± 10 nm) exhibits 100% rejection for biomolecules such as tannic acid (TA) and bovine serum albumin (BSA) and >99% rejection for multiple probe molecules, such as methylene blue, methyl orange, congo red, and rhodamine B. The high rejection of membranes can be attributed to the surface interaction of mica with GO nanosheets through covalent interaction, which enhances the stability and separation efficiency of the membranes for probe ions and molecules. This ultrathin MGO membrane also exhibits much better water permeability at 870 ± 5 L m-2 h-1 bar-1, which is 10-100 times greater than that reported for pure GO and GO-based composite membranes. Additionally, the membrane shows high rejection for salt ions (70%). Furthermore, the stability of the MGO membranes was evaluated under various conditions, and the membranes demonstrated remarkable stability for up to 60 days in a neutral environment.