I--Lactalbumin (I--La) and lysozyme (LZM) each contain four disulfide bonds but no free SH group, whereas myoglobin (Mb) possesses no disulfide bond or free SH group. In this work, the ...pressure-induced gelation of I--La, LZM and Mb in the absence and in the presence of I2-lactoglobulin (I2-Lg) was studied. Solutions of I--La, LZM and Mb (1a24%, w/v) did not form a gel when subjected to a pressure of 800 MPa and circular dichroism analysis revealed that both I--La and LZM are pressure-resistant proteins. In the presence of I2-Lg (5%, w/v), however, a pressure-induced gel formed for I--La and LZM (each 15%, w/v) but not for Mb (15%, w/v). One- and two-dimensional SDS-PAGE demonstrated the disulfide cross-linking of proteins was responsible for the gelation. Although I--La and LZM are homologous and have the same disulfide bond arrangement, the texture and appearance of the gels formed from I--La/I2-Lg and LZM/I2-Lg were markedly different even when induced under the same experimental conditions. Microscopic analysis indicated that phase separation occurs during the gelation of LZM/I2-Lg but not during the gelation of I--La/I2-Lg. NMR relaxation measurement revealed that the association of water molecules with the protein matrix in the I--La/I2-Lg gel is tighter compared to that in the LZM/I2-Lg gel. These results indicate that the gel-forming ability of a globular protein under high pressure is related to the primary structure of the protein, and that the gel properties depend on the cross-linking reaction and on the phase behavior of protein dispersion under high pressure.
Noncanonical amino acids (ncAAs) for photo‐ and chemical crosslinking are powerful biochemical tools for studying and manipulating interactions between proteins both in vitro and in intact cells. ...Since the first crosslinking ncAAs were genetically encoded about 20 years ago, the technology has now ripened beyond the proof‐of‐principle demonstrations and is contributing to the study of relevant biological questions in the frame of modern integrative approaches. Here, we provide an overview of available photo‐activatable ncAAs for photo‐crosslinking and electrophilic ncAAs for genetically encoded chemical crosslinking (GECX), with a major focus on the most recent entries such as ncAAs for SuFEx click chemistry and photo‐activatable ncAAs for chemical crosslinking. We present recent examples of the application of genetically encoded crosslinkers to capture protein–protein interactions and identify interaction partners in live cells, to investigate molecular mechanisms of protein function, to stabilize protein complexes for structural studies, to derive structural information about protein complexes from the physiological cell environment, up to perspective applications of GECX‐ncAAs for the development of covalent drugs.
There is continuing interest in the synthesis of polyhydroxy-terminated molecular species for diverse applications ranging from photolithographic materials to intermediates in the synthesis of ...porous, crosslinked polymers as media for molecular separations, drug delivery etc. We describe here the use of vinylSiO sub(1.5) sub(8) and vinylSiO sub(1.5) sub(10/12) mixtures to synthesize first- and second-generation acetoxyphenyl compounds via metathesis with p-acetoxystyrene (generation 1, GEN1) or metathesis with p-bromostyrene followed by Heck coupling with p-acetoxystyrene (generation 2, GEN2). The resulting acetoxy compounds were then hydrolyzed to produce octa-, deca- and dodecahydroxy GEN1 and GEN2 compounds. These compounds were purified and then reacted with adipic acid chloride to form the first examples of highly crosslinked polyesters based on silsesquioxanes. The coupling products, their hydrolyzed products and the crosslinked polymers were characterized using a variety of spectroscopic methods. In general, the observed specific surface areas were less than 5m super(2)g super(-1) ; however, the T sub(8) GEN1 derivative gave a surface area of 25m super(2)g super(-1) and was the only crosslinked polymer with a TGA ceramic yield that matched theory for 'perfect' crosslinking. This crosslinked polyester has the shortest organic linker between cages and despite the highly flexible C sub(6) linker provides continuing evidence that it is possible to use the cubic symmetry in these materials to build well-ordered 3-D nanocomposite structures. Copyright copy 2013 John Wiley & Sons, Ltd. Synthesis of Acetoxy and Hydroxy Phenyl Terminated Polyfunctional T sub(8), T sub(10), T sub(12) Silsesquioxanes and Initial Studies on Their Use in the Formation of Highly Crosslinked Polyesters.
Crosslinking is the process of forming tridimensional networks by linking polymer chains by covalent or noncovalent bonds. It is useful for polysaccharide- and protein-based films and coatings to be ...applied to food surfaces, enhancing their water resistance as well as mechanical and barrier properties. Crosslinkers intended to be used for food contact materials must present low toxicity.
This review is a summary of the main crosslinking agents which have been used for protein and polysaccharide films and coatings, and which may be applied as food contact materials. The study emphasizes the mechanisms of crosslinking agents, the chemical groups involved, conditions for application, advantages and drawbacks, as well as examples of applications for food contact materials.
Crosslinking is a promising technique to improve the performance and applicability of protein- and polysaccharide-based food contact materials, especially concerning their water sensitivity, which hinders many of their potential applications as food contact materials. Some aldehydes are very effective as crosslinkers, but they have been avoided in food contact materials because of possible migration of aldehyde residues to food, and less toxic compounds have been studied for those applications, such as phenolic acids, oxidized polysaccharides, and enzymes. Crosslinking techniques may help make protein- and polysaccharide-based materials more suitable for large-scale processing and applications in the future.
•Polysaccharide and protein films have limited physical properties.•Crosslinking enhances film performance, notably water resistance.•Some crosslinkers may leave toxic residues which might migrate to food.•Less toxic chemical and physical crosslinkers have been studied.•Mechanisms, effects, and applications of crosslinking agents are summarized.
High‐performance bio‐based fibers have unique advantages in biocompatibility for biomedical applications, such as sutures, hernia patches, and blood vessels. Herein, strong and tough biofibers based ...on regenerated silk fibroins (RSFs) are designed by a dual‐crosslinking strategy and prepared continuously in situ via a single‐channel microfluidic device. During the wet spinning process, covalent bonds between tyrosines are introduced by photo crosslinking and coordination interactions of Zn2+ ions with serines are built between RSFs, forming a dual‐crosslinked, and inter‐connected network and effectively improving the mechanical performances of RSF fibers. By optimizing the wet spinning parameters and applying an optimal post‐stretching treatment, dual‐crosslinked RSF fibers exhibit an excellent tensile strength of 891 MPa, a remarkable Young's modulus of 15.0 GPa, a large tensile strain of 20.1%, and an outstanding toughness of 114 MJ m−3, which are superior to other regenerated biofibers. In addition to the outstanding mechanical performances, dual‐crosslinked RSF fibers also possess excellent temperature adaptability, fatigue resistance, biocompatibility, and biodegradability, making them ideal candidates for biomedical applications. In vivo tests of dual‐crosslinked RSF fibers as sutures demonstrate a good wound healing performance with smaller scar and lower inflammation.
Strong and tough biofibers based on regenerated silk fibroins (RSFs) are designed by a dual‐crosslinking strategy. Covalent bonds between tyrosines are introduced by photo crosslinking and coordination interactions of Zn2+ ions with serines are built between RSFs, forming a dual‐crosslinked network. Dual‐crosslinked RSF fibers exhibit excellent mechanical performances, temperature adaptability, fatigue resistance, biocompatibility and biodegradability, making them ideal candidates for sutures.
An in situ crosslinking strategy is used for 3D bioprinting of nonviscous photo‐crosslinkable hydrogels. This method can be generalized to various photo‐crosslinkable formulations, maintaining high ...embedded cell viability and tunable cell behavior. Heterogeneous and hollow filaments can be printed using this strategy, allowing fabrication of complex engineered cell‐laden constructs.
A one‐pot reaction of the A1/A2‐thiopyridyl pillar5arene L with silver(I) trifluoroacetate in the presence of the linear dinitrile guest C8, CN(CH2)nCN, n=8, afforded the first example of a ...two‐dimensional (2D) poly‐pseudo‐rotaxane {(μ4‐Ag)2(C8@L)2(μ‐C8)(CF3CO2)2}n. Surprisingly, in this structure the C8 guest not only threads into the pillar5arene unit but also crosslinks the 1D coordinative polymeric arrays. The formation of the 2D poly‐pseudo‐rotaxane is driven by an adaptive rearrangement of the components that minimizes the steric clashes not only between the threaded guests but also between the threaded and crosslinked guests where crosslinking occurs. A pathway for the formation of the 2D poly‐pseudo‐rotaxane is proposed.
Pure tetragonal phase Ba sub(0.96)Sr sub(0.04)Zr sub(0.04)Y sub(0.005)Ti sub(0.955)O sub(2.9975) nano-powders were synthesized via a simple, fast and low cost method: polyacrylamide gel (PAG) method. ...The effects of processing parameters on the polymerization reaction and the sizes of as-prepared powder were investigated. The results reveal that the critical value of monomer / cross-linking agent ratio is 4.5:1 for the tightest network structure and the smallest average particle size of nano-powder correspondingly due to the smallest grid of gel. The monomer/cross-linking agent ratio and the concentration of cross-linking agent have significant influence on the gel quality and particle. In the investigation range we have probed into, the nano-dispersed BSZYT powders is obtained. The average native grain size of as-prepared powder is similar to 27 and similar to 45 nm after calcined at 900 degree C and 1200 degree C, respectively.
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•A hybrid hydrogel with chemical and physical crosslinking exhibited excellent mechanical behaviors.•The hydrogel can be inflated into a big balloon and the membrane can quickly ...restore to its original state.•The relationship between chemical and physical crosslinking points in the various deformation stages of hydrogel.
Hybrid crosslinking hydrogels have exhibited excellent mechanical properties, however, the relationship between chemical and physical crosslinking in the various deformation stages is still indistinct. Here, a hybrid hydrogel was explored by inducing low density of chemical crosslinking into latex particle hydrogels (LP-Gel), in which latex particles act as physical crosslinking centers for inducing efficient aggregation of hydrophobic chains. The resulting hybrid hydrogel exhibited extraordinary mechanical performance. It is found that the role of chemical and physical crosslinking was different during different deformation levels. The synergistic effects of chemical and physical crosslinking allow hydrogels to dissipate a large number of energy, significantly enhancing the mechanical strength of hydrogels. Moreover, the hybrid hydrogel exhibited puncture resistant, excellent ductility and rapid recovery.
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