Chemical Cross-linking Research Articles

Kinetic principles of chemical cross-link formation for protein–protein interactions

Proteins play a central role in most biological processes within the cell, and deciphering how they interact is key to understand their function. Cross-linking coupled with mass spectrometry is an essential tool for elucidating protein-protein interactions (PPIs). Despite its importance, we still know surprisingly little about the principles that underlie the process of chemical cross-link formation itself and how it is influenced by different physicochemical factors. To understand the molecular details of cross-link formation, we have set up a comprehensive kinetic model and carried out simulations of protein cross-linking on large protein complexes. We dissect the contribution on the cross-link yield of parameters such as amino acid reactivity, cross-linker concentration, and hydrolysis rate. Our model can compute cross-link formation based solely on the structure of a protein complex, thereby enabling realistic predictions for a diverse set of systems. We quantitatively show how cross-links and mono-links are in direct competition and how the hydrolysis rate and abundance of cross-linker and proteins directly influence their relative formation. We show how cross-links and mono-links exist in an "all-against-all" competition due to their simultaneous formation, resulting in a nonintuitive network of interdependence. We show that this interdependence is locally confined and mainly limited to direct neighbors or residues in direct vicinity. These results enable us to identify the optimal cross-linker concentration at which the maximal number of cross-links is formed. Taken together, our study establishes a comprehensive kinetic model to quantitatively describe cross-link formation for PPIs.

Thermal and radiation effects on the cross-linking and mechanical properties of HNBR elastomers

This study investigates the enhancement of the properties of mixtures based on hydrogenated butadiene nitrile rubber (HNBR) under thermal, radiation and thermo-radiation effects by introducing into them the composition of chlorine-containing triazine and peroxide compounds (HCPX and ABTST) into the composition. It has been shown that radiation-chemical cross-linking and the formation of effective chemical cross-links in HNBR depend both on the absorbed dose of radiation and on the addition of vulcanizing agents. It has been established that the activity of hexachloroparaxylene (HCPX), dicumyl peroxide (DP) and triazine (ABTST) is not the same; the content of the gel increases markedly with increasing absorbed dose. A higher crosslinking density is observed for images subjected to thermo-radiation crosslinking. The change in the molecular structure of HNBR, observed both during heating and irradiation, has the same nature. It has been shown that the physical and mechanical properties of saturated radiation and thermal vulcanizates are practically inferior to thermo-radiation ones in strength.

Measurement of Covalent Bond Formation in Light-Curing Hydrogels Predicts Physical Stability under Flow.

Photo-crosslinking hydrogels are promising for tissue engineering and regenerative medicine, but challenges in reaction monitoring often leave their optimization subject to trial and error. The stability of crosslinked gels under fluid flow, as in the case of a microfluidic device, is particularly challenging to predict, both because of obstacles inherent to solid-state macromolecular analysis that prevent accurate chemical monitoring and because stability is dependent on size of the patterned features. To solve both problems, we obtained 1H NMR spectra of cured hydrogels which were enzymatically degraded. This allowed us to take advantage of the high-resolution that solution NMR provides. This unique approach enabled the measurement of degree of cross-linking (DoC) and prediction of material stability under physiological fluid flow. We showed that NMR spectra of enzyme-digested gels successfully reported on DoC as a function of light exposure and wavelength within two classes of photo-cross-linkable hydrogels: methacryloyl-modified gelatin and a composite of thiol-modified gelatin and norbornene-terminated polyethylene glycol. This approach revealed that a threshold DoC was required for patterned features in each material to become stable and that smaller features required a higher DoC for stability. Finally, we demonstrated that DoC was predictive of the stability of architecturally complex features when photopatterning, underscoring the value of monitoring DoC when using light-reactive gels. We anticipate that the ability to quantify chemical cross-links will accelerate the design of advanced hydrogel materials for structurally demanding applications such as photopatterning and bioprinting.

Simultaneous processing of both handheld biomixing and biowriting of kombucha cultured pre-crosslinked nanocellulose bioink for regeneration of irregular and multi-layered tissue defects

The nanocellulosic pellicle derived from the symbiotic culture of bacteria and yeast (Kombucha SCOBY) is an important biomaterial for 3D bioprinting in tissue engineering. However, this nanocellulosic hydrogel has a highly entangled gel network. This needs to be partially modified to improve its processability and extrusion ability for its applications in the 3D bioprinting area. To control its mechanical and biological properties for direct 3D bioprinting applications, uniform reinforcement of nanocellulose-interacting polymers and nanoparticles in such a prefabricated gel network is essential. In this study, the hydrogel network is partially hydrolyzed with organic acid and subsequently transformed into a 3D bioprintable polyelectrolyte complex with chitosan and kaolin nanoparticles without any chemical crosslinker using a handheld 3D bioprinter. This handheld bioprinter ensures homogeneity in both biomixing and bioprinting of chitosan and kaolin within the modified nanocellulose network for multi-layered bioprinted scaffolds through an extensional shear mechanism. The biomixing simulation, mechanical (static, dynamic, and cyclic), 3D bioprinting, and cellular studies confirm the homogeneous biomixing of kaolin nanoparticles and live cells in this nanocellulose-chitosan polyelectrolyte hydrogel. The combination of SCOBY-derived nanocellulose-chitosan bioink with kaolin nanoparticles and a screw-driven handheld extrusion bioprinter demonstrates a promising platform for layer-by-layer regeneration of complex tissues with homogeneous cell/particle distribution with high cell viability.

High-performance bio-based foam from agricultural waste luffa seed oil polyols

The present study aimed to develop eco-friendly polyurethane viscoelastic foam (PVF) with enhanced tear strength while preserving softness, comfort, and safety by utilizing bio-based polyols derived from luffa seed oil (LSO). Two types of bio-based polyols (PLSO-D and PLSO-M) were synthesized through the epoxidation process using diethylene glycol (DEG) and methanol (MeOH), respectively, for the production of LSO-based polyurethane viscoelastic foams (LSO-PVFs). The analyses revealed that these polyols exhibited high dispersion, appropriate hydroxyl values, and contained by-products such as oligomeric esters of fatty acids that facilitated physical and chemical crosslinking. LSO-PVFs demonstrated a uniform and fine cell structure with abundant open-cells, thick cell walls (55.5–76.6µm), and high apparent density (48.7–50.7kg/m3). Moreover, they exhibited enhanced tensile and tear strength (increasing up to 200% compared to petroleum-based PVFs), lower water absorption, excellent mildew resistance at 10% PLSO substitution. Additionally, these factors endowed LSO-PVFs with low indentation hardness and good bottom support performance, characterized by a compressive deflection coefficient of 2.30–3.54. This approach presents a sustainable alternative for foam production that offers comfort, durability while promoting the value-added utilization of agricultural waste.

Preparation of energy-efficient, environmentally friendly and high-strength biocomposites from wood fibre ultramicro self-composite cellulose matrices

Considering the diminishing forest as a natural resource, the efficient use of small-diameter shrubs is crucial for global sustainable development. This approach has significant potential to prevent wasting forest resources and reduce carbon emissions. However, small-diameter timber has inherent drawbacks, such as the looseness of this material, susceptibility to cracking and deformation, and low strength, all of which significantly impact its range of applications. In this study, an efficient, green method was developed to prepare adhesive-free biocomposites from discarded small-diameter shrubs via ultrasonic pretreatment and thermoforming. After the ultrasonic pretreatment, the flexural and tensile strengths of the biocomposites increased by 145% and 132%, respectively. Ultrasonic pretreatment separated and destroyed chemical bonds among the lignocellulosic biomass macromolecules through high-speed shear and microjets. This process significantly increased the amount of binding sites on the cellulose fibres, and further densified the cell walls through hot pressing. Moreover, the ultrasonic pretreatment may remove components of the wood flour that act as fillers or density enhancers, resulting in a reduction in the density of the biocomposite. Simultaneously, lignin acted as a binder and improved fibre bonding through both physical and chemical cross-linking, resulting in a dense cellulose structure with a three-dimensional lattice structure and a less hydrophilic surface, as evidenced by a water contact angle of 81.72°. In addition, the high-quality, binder-free biocomposites did not emit harmful gases such as formaldehyde. Hence, they are expected to become sustainable materials for building decoration and furniture applications in the future.

Treatment of ulcerative colitis via the in situ restoration of local immune and microbial homeostasis by oral administration of Tremella polysaccharide drug-carrying hydrogel

Ulcerative colitis (UC) is a prevalent inflammatory bowel disease, and conventional treatments, such as anti-inflammatory medications and surgery, often prove inadequate due to frequent recurrences and various complications. To alleviate patient suffering, there is an urgent need for a therapeutic system that specifically delivers drugs to the colon for wound healing, inflammation relief, and restoration of microbial homeostasis. In this paper, we developed a Tremella polysaccharide drug-carrying hydrogel that adheres to the inflamed colonic mucosa, forming an effective artificial barrier and releasing the drug in situ to restore local immune and microbial balance. The hydrogel backbone was synthesized through the chemical cross-linking of Tremella polysaccharide with 1,4-butanediol diglycidyl ether in an alkaline environment. During this process, Soluplus® and TPGS-encapsulated ginsenoside compound K adhered to the hydrogel backbone due to electrostatic attraction. The enhanced adhesion following cross-linking enables the hydrogel to stably attach to the inflamed colonic mucosa, releasing mixed micelles that improve drug penetration and absorption by inhibiting the cellular efflux protein P-glycoprotein. This mechanism promotes local immune recovery and eliminates harmful intestinal flora, providing significant relief from UC symptoms. This natural polysaccharide-based hydrogel represents a highly effective oral treatment for UC.

Enhanced chemical stability and H+/V4+ selectivity of microporous sulfonated polyimide via a triptycene-based crosslinker

Long durability of sulfonated polyimide in vanadium redox flow battery (VRFB) is urgently required to be solved. Herein, we synthesize a triptycene-based crosslinker and use it as chemical crosslinking point to modify a linear sulfonated polyimide for promoting its antioxidative stability. The novel triptycene-based cross-linked sulfonated polyimide (TCSPI-X) membranes featuring covalently crosslinked network display lower water uptake and swelling ratio than the commercial perfluorinated ionomer membrane (Nafion 117) membrane. More importantly, unnoticeable proton conductivity loss is appeared. We speculate this is because of the covalently crosslinking structure provides stable proton transportation channels, and the formation of micropores induced by rigid triptycene unit decrease proton migration resistance. In which, the TCSPI-5 (with 5 % molar triptycene unit) exhibit higher voltage efficiency as compared with the pristine membrane TCSPI-0. Combined with the excellent vanadium ions resistance, the TCSPI-5 reaches energy efficiency of 78 % at the current density of 140 mA cm−2. In addition, TCSPI-5 also shows high oxidation resistance even under strong acid and pentavalent vanadium ions (V5+) conditions. The above results suggest the potential of TCSPI-X membranes in VRFB application.

Development of starch-based films with enhanced hydrophobicity and antimicrobial activity by incorporating alkyl ketene dimers and chitosan for fruit preservation

Using hydrophobic antimicrobial food packaging films offers significant opportunities to extend the shelf life of food. This study developed a hydrophobically modified starch-based film incorporating alkyl ketene dimers (AKDs) and chitosan (CS) for mango preservation. The film's physicochemical properties and structural characteristics were comprehensively analyzed. The successful integration of AKDs into the starch (ST) matrix was confirmed through FT-IR, XRD, XPS, and SEM techniques, which revealed the establishment of β-ketoester linkages via esterification. The addition of AKDs significantly enhanced the film's hydrophobicity and mechanical properties, attributed to chemical cross-linking and the formation of intermolecular hydrogen bonds. In an eight-day room temperature storage test, the ST-AKD/CS films effectively extended the shelf life of mangoes by four days compared to the control and ST groups. As all components of the film are environmentally friendly and biodegradable, these hydrophobic films offer a promising solution for prolonging the freshness of mangoes while maintaining sustainability.

Beeswax-based nanoconstructs enriched dual responsive hydrogel for diabetic foot ulcers in streptozotocin-induced diabetic rats.

Diabetic foot ulcer (DFU) is a complicated pathophysiological process, and there is now no recognized treatment. Hyperglycemia, neuropathy, impaired angiogenesis, reactive oxygen species, and advanced glycation end products construct the distinctive wound environment of diabetic wounds. This study aimed to develop naringenin-ferulic acid beeswax-based nanoconstructs enriched dual-responsive hydrogel (NAR-FA NLC HG) for topical application for DFU. The pH- and temperature-responsive hydrogel was formulated via a chemical cross-linking reaction of carboxymethyl chitosan and poloxamer 407 and loaded with NAR-FA NLC using the swelling-loading method. SEM, FTIR, and XRD observed the morphology and characterization of the prepared hydrogel. The in vitro release study showed controlled release during 48 h. Antibacterial activity significantly inhibits B. subtilis and E. coli compared to NLC and control groups (p < 0.05). Cell line studies show that hydrogel is compatible with HaCaT cells and 92.4 ± 4.9 % of wound contraction after 48 h of scratch wound assay. The wound closure rate with NAR FA NLC HG in STZ-induced diabetic rats reached 93.2 ± 3.4 % by day 15 with significant (p < 0.001) increases in the VEGF level and decreasing ICAM-1 level. Hence, the smart hydrogel established in this study has the potential to serve as a promising topical therapy for DFU with inherent antimicrobial activity components, including beeswax, NAR, and FA.

Facile Preparation of Polymerizable Deep Eutectic Solvents Under Mild Conditions for Multisensory Ionic Skins

AbstractPolymerizable deep eutectic solvents (PDESs) have emerged as promising building blocks for next‐generation eutectic gels, offering new opportunities for the development of advanced electronic devices. Traditional PDES fabrication typically involves heating and extended processing time. In this study, a facile method where a solid‐solid mixture of lithium bis(trifluoromethane) sulfonimide (LiTFSI) and acrylamide (AAm) rapidly forms a PDES at room temperature, significantly simplifying the ionogel preparation is presented. By combining this PDES with another system, comprising 3‐[dimethyl‐[2‐(2‐methylprop‐2‐enoyloxy)ethyl]azaniumyl]propane‐1‐sulfonate (SBMA) and ethylene glycol (EG), an eutectic gel is successfully fabricated with exceptional mechanical and conductive properties. This gel exhibits a fracture stress of 0.8 MPa, fracture energy of 3.7 kJ m−2, adhesion strength of 60 kPa, transmittance over 90%, high conductivity (0.113 S m−1), and an outstanding temperature tolerance ranged from ‐50 to 50 °C. Notably, the absence of chemical crosslinkers and the presence of reversible interactions such as hydrogen bonding and ion‐dipole electrostatic forces impart excellent self‐healing capabilities. These combined features position the gel a promising candidate for multisensory ionic skins, capable of detecting pressure, temperature, humidity, and sweat. This work pioneers the rapid, mild‐condition synthesis of PDESs, paving the way for new techniques in ionic skin development.

Active polyvinyl alcohol films with enhanced strength, antioxidant and antibacterial properties by incorporating nanocellulose and tannin

There is an increasing demand of food packaging materials from sustainable bio- polymers. In this study, tannin-cellulose nanocrystal (TCNCs) fillers were first prepared using dialdehyde cellulose nanocrystal (DACNCs) and tannin through the nucleophilic addition reaction, and then added to PVA matrix as reinforcement fillers to fabricate active food packaging films. FT-IR analysis confirmed the successful reaction between PVA and TCNCs. The incorporation of TCNCs imparted high antibacterial, UV blocking and antioxidant capabilities to the composite films, maximumly achieving a 75 % DPPH free radical scavenging rate while blocking all UV rays. The addition of TCNCs resulted in an increase in water contact angle, alongside decreases in swelling ratio and solubility, indicating the enhanced water resistance. The composite films exhibited a 66.7 % decrease in oxygen permeability (OP) compared to the PVA film, with a slight increase observed in water vapor permeability (WVP). The tensile strength increased from 49.65 MPa to 74.17 MPa by adding 15 % of TCNCs due to the chemical crosslinking between PVA and TCNCs. Wrapping cherry tomatoes with these films prolonged the postharvest life compared to using polyethylene (PE) and pure PVA films. Films derived from sustainable biopolymers show great potential for use in fresh produce packaging.

Mechanical and thermo-oxidative resistance properties of natural rubber film reinforced by orange peel-based carbon dots

Bio-based carbon dots (CDs) have a wide range of precursor sources, abundant chemical functional groups, and good free radical scavenging ability. This makes them an excellent candidate for modifying natural rubber (NR). In this work, CDs were synthesized from orange peels using a hydrothermal process and were utilized to reinforce NR latex. The structure and properties of both the CDs (including morphology, functional groups and fluorescence emission spectra) and NR/CDs films (including crosslinking density, morphology, functional groups, and mechanical properties) were comprehensively investigated. The results indicate that the inclusion of CDs led to improvements in tensile and tear strength while maintaining undamaged elongation at break. The tube model results indicate that the Ge (the elastic modulus brought by entangled chains) is significantly higher than the Gc (the elastic modulus contributed by chemical crosslinking) in this system, suggesting that the physical entangled network play a more significant role than chemical cross-linking; and the trend of Gc+Ge with the amount of CDs aligns completely with the cross-linking density measured by swelling method. Additionally, it was observed that CDs exhibited excellent thermo-oxidative resistance properties for NR. After 24 hours of thermal aging, the aging coefficient increased from 20.7% (NR-0) to 65.8% (NR-7). Furthermore, with an increase in thermal aging time, the tensile strength and crosslinking density of NR-0 decreased at a faster rate compared with NR-5. At an aging time of 40 hours, the tensile strength of NR-0 was reduced to 0.53 MPa and almost completely failed; whereas the tensile strength of NR-5 was still maintained at 8.2 MPa. Overall, the addition of CDs dramatically improved the thermo-oxidative resistance and mechanical properties of the NR film. Simultaneously, a novel way involving the utilization of orange peel with high value is being proposed.

Synthesis, characterization, and application potential of chitosan/acrylamide composite hydrogels as skin expanders

Hydrogels are currently widely used in regenerative medicine and wound repair due to their superior biocompatibility, reliable mechanical strength, and good morphological memory. We aimed to prepare a self-expanding hydrogel that can be used as a skin expander for the repair of large soft skin tissue defects. Self-expanding hydrogels were prepared by chemical cross-linking, which consisted of water-soluble chitosan (CS), acrylamide (AM), methylene bisacrylamide (NMBA), etc. Five groups of in vitro experiments, including (CS-AM) of 0% (pure AM group), 13.9%, 27.8%, 41.7%, and 55.6%, were conducted to determine mechanical properties, swelling properties, cytotoxicity, etc. In the rat model, both a tight skin area (neck) and a loose skin area (back) were selected for expansion with hydrogels. A total of 27.8% of the CS-AM samples expanded stably under the skin of the rats, achieving 370% expansion in the tight zone and 490% expansion in the flaccid zone. Subcutaneous histopathological examination suggested that the inflammation index of the pericolloid tissue was lower in the CS-AM group than in the pure AM group. Our results demonstrate that self-expanding CS-AM hydrogels have great potential for application as skin expanders.Graphical

One-Step Digital Light Processing 3D Printing of Robust, Conductive, Shape-Memory Hydrogel for Customizing High-Performance Soft Devices.

Mechanically robust and electrically conductive hydrogels hold significant promise for flexible device applications. However, conventional fabrication methods such as casting or injection molding meet challenges in delivering hydrogel objects with complex geometric structures and multicustomized functionalities. Herein, a 3D printable hydrogel with excellent mechanical properties and electrical conductivity is implemented via a facile one-step preparation strategy. With vat polymerization 3D printing technology, the hydrogel can be solidified based on a hybrid double-network mechanism involving in situ chemical and physical dual cross-linking. The hydrogel consists of two chemical networks including covalently cross-linked poly(acrylamide-co-acrylic acid) and chitosan, and zirconium ions are induced to form physically cross-linked metal-coordination bonds across both chemical networks. The 3D-printed hydrogel exhibits multiple excellent functionalities including enhanced mechanical properties (680% stretchability, 15.1 MJ/m3 toughness, and 7.30 MPa tensile strength), rapid printing speed (0.7-3 s/100 μm), high transparency (91%), favorable ionic conductivity (0.75 S/m), large strain gauge factor (≥7), and fast solvent transfer induced phase separation (in ∼3 s), which enable the development of high-performance flexible wearable sensors, shape memory actuators, and soft pneumatic robotics. The 3D printable multifunctional hydrogel provides a novel path for customizing next-generation intelligent soft devices.

A superwetting rough structured nanofibrous membrane with enhancing anti-fouling performance for oil–water separation

Oily wastewater generated from many industries has become a tremendous potential threat to ecological balance and human health. However, severely hindered by interfacial wettability, the present oil/water separation membranes are subjected to a serious oil fouling problem during long-term oily wastewater separation. Herein, we construct superwetting rough structured nanofibrous membrane (SRSNM) composed of superhydrophilic PVA/SA bead-on-string nanofibrous functional layer and PVA nanofibrous substrate by two step electrospinning together with chemical crosslinking. Benefitting from the inherent hydrophilic properties of SA and PVA combined with the rough structure endowed by the bead-on-string nanofibers, the SRSNMs exhibited fascinating superhydrophilicity and underwater superoleophobicity. Meanwhile, thanks to the submicron pores and high porosity, the SRSNM could separate submicron oil-in-water emulsions with robust permeation flux of 1319 L m-2h−1 and high separation efficiency of 99.9 % under the gravity driving (∼1 kPa). More importantly, this SRSNM showed excellent anti-oil-fouling performance with high flux recovery of 99 %, negligible irreversible oil fouling rate of 1 %, and intriguing reusability for the long-term separation. The design of such superwetting rough structured nanofibrous membrane may provide an efficacious strategy for synthesizing high-performance separation membranes.

A new PVA-κCA double-network hydrogel comprising conductive polyaniline nanofibers for strain sensing applications

AbstractWearable and flexible materials are replacing the conventional solid-state sensors in diffident biomedical applications. Hydrogel-based sensing elements offer several appealing inherent properties such as tissue resembling elasticity, accessibility for modification and robust mechanical performance. Their widely available and affordable raw components in-addition to straightforward synthesis and modification approach make hydrogels appealing material for flexible and wearable sensors in biomedical applications. This work demonstrates the development of new and sensitive material for strain sensing using polyvinyl alcohol (PVA) and κ-carrageenan (κCA) hydrogel comprising conductive polyaniline nanofibers (PANI NFs). The double-network hydrogel was produced via chemical crosslinking of PVA with Glutaraldehyde (GA) and physical crosslinking of κCA with potassium ions in a binary solvent system of deionized water and glycerol. The PANI NFs were then embedded in the hydrogel via the interfacial polymerization (IP) method of polyaniline nanofibers to significantly enhance the material properties and strain sensitivity of the pristine hydrogel. The obtained hydrogel has been involved in rigorous material characterization and sensing capability evaluation. The produced hydrogel demonstrated a high-water content (86.6%), high swelling percentage in acidic solutions, mechanical compressibility up to 60% at 400 kPa, high electrical conductivity of 2.11 S/m, and thermal stability ranging from − 26.9 to 120 oC. The hydrogel resulted in a linear response in its sensing performance of the applied stress (R2 = 0.99). Also, the developed composite demonstrated a sensitivity of 1.5 mV/kPa in stress range from zero up to 170 kPa with response and recovery times of ~ 300 ms and 500 ms, respectively.

Fabrication of Ionic Supramolecular Oleogel Lubricants Enhanced with Liquid Metal Nanodroplets for Superior Tribological Performance.

Supramolecular Oleogel lubricants provide a versatile and reliable strategy for optimizing the long-term dispersion stability of nanoadditives in the base oils. In this work, GLM-based ionic gelators constructing supramolecular oleogels were prepared by adding ultrasonically treated gallium-based liquid metal (GLM) nanodroplets carrying free radicals and vinyl-containing ionic liquids (ILs) directly to a free radical polymerization system of polymer gelators. The electrostatic interactions between the ionic liquids and GLM nanodroplets enhanced the cross-linking degree of supramolecular gels and formed denser self-assembled structures. The as-prepared GLM-based ionic oleogels as thermoreversible gels exhibit exceptional thixotropic properties. Compared to the base oil PAO10, the coefficient of friction (COF) for both GLM@IGel-1 and GLM@IGel-2 decreased significantly from 0.192 to 0.097, while the wear volume dropped from 100.10 × 104 μm3 to 13.28 × 104 μm3 for GLM@IGel-1, and to 9.69 × 104 μm3 for GLM@IGel-2. In addition, GLM@IGel-2 demonstrates a higher load-bearing capacity of 550 N due to further chemical cross-linking by ionic liquids. The outstanding lubrication performance of GLM-based ionic oleogels is achieved by the synergy of GLM nanodroplets and gel lubricants, promoting the formation of a stable tribo-chemical reaction film.

Large-Scale Quantitative Cross-Linking and Mass Spectrometry Provides New Insight on Protein Conformational Plasticity within Organelles, Cells, and Tissues.

Many proteins can exist in multiple conformational states in vivo to achieve distinct functional roles. These states include alternative conformations, variable PTMs, and association with interacting protein, nucleotide, and ligand partners. Quantitative chemical cross-linking of live cells, organelles, or tissues together with mass spectrometry provides the relative abundance of cross-link levels formed in two or more compared samples, which depends both on the relative levels of existent protein conformational states in the compared samples as well as the relative likelihood of the cross-link originating from each. Because cross-link conformational state preferences can vary widely, one expects intra-protein cross-link levels from proteins with high conformational plasticity to display divergent quantitation among samples with differing conformational ensembles. Here we use the large volume of quantitative cross-linking data available on the public XLinkDB database to cluster intra-protein cross-links according to their quantitation in many diverse compared samples to provide the first widescale glimpse of cross-links grouped according to the protein conformational state(s) from which they predominantly originate. We further demonstrate how cluster cross-links can be aligned with any protein structure to assess the likelihood that they were derived from it.

Anionic surfactant effect on the structural and thermal insulation properties of crosslinked-cellulose nanofiber foam and its superhydrophobic treatment

Sustainable and environmentally friendly cellulose nanofiber (CNF) has unique advantages and properties for preparing porous materials for various applications. This study reports a CNF foam developed via an environmentally friendly, expeditious and cost-effective process using sodium dodecyl sulfate (SDS) and citric acid (CA) as an anionic surfactant and a bio-based green crosslinker. Incorporating 0.5 wt% SDS into CA-crosslinked CNF foam significantly enhances its porous structure, indicating the highest porosity (>99.24 %) and a very low density (18.59 mg/cm3). The performance improvement is attributed to the formation of robust ester bonds through chemical crosslinking, which stabilizes the foam's microstructure and enhances its mechanical strength. Additionally, the SDS facilitates better foaming and reduces surface tension, promoting uniform distribution of pores. The foam shows better mechanical properties and antioxidant behavior than the neat CNF foam. Moreover, adding SDS into the CA-crosslinked NC foam exhibits lower thermal conductivity (0.029 W/mK) and diffusivity than commercial insulation foams, including polyurethane foam. Finally, a superhydrophobic CA-crosslinked CNF foam is made by a water-based hydrophobic treatment (water contact angle = 150°), indicating its waterproof behavior.