A novel “trifunctional protease” with reducibility,hydrolysis, and localization used for wool anti-felting treatment

Proteases can cause unacceptable fiber damage when they are singly applied to wool anti-felting treatment which can make wool textiles machine-washable. Even if protease is attached by synthetic polymers, the modified protease plays a limited role in the degradation of keratin with dense structure consisting of disulfide bonds in the scales. Here, to obtain “machine-washable” wool textiles, a novel “trifunctional protease” with reducibility, hydrolysis, and localization is developed by means of covalent bonding of protease molecules with poly (ethylene glycol) bis (carboxymethyl) ether (HOOC-PEG-COOH) and l-cysteine using carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling, aiming at selectively degrading the scales on the surface of wool. The formation of polymer is confirmed with size exclusion chromatography (SEC) and Fourier transform infrared spectroscopy (FT-IR). Ellman’s test and fluorescence microscopy reveal that the modified protease can reduce disulfide bonds and restrict hydrolysis of peptide bonds on the wool scales. Furthermore, when applied to wool fabrics, the modified protease reach better treatment effects considering dimensional stability to felting (6.12%), strength loss (11.7%) and scale dislodgement proved by scanning electron microscopy (SEM), alkali solubility, wettability, and dyeability. This multifunctional enzyme is well-designed according to the requirement of the modification of wool surface, showing great potential for eco-friendly functionalization of keratin fibers rich in disulfide linkage.

     

Intrachain reactions of a pair of reactive groups attached to polymer ends. V. Formation of disulfide linkages in the air-oxidation of sulfhydryl groups attached to ends of polysarcosine chain

Polysarcosine having sulfhydryl groups attached to both ends was synthesized by the NCA method and its air-oxidation was investigated in aqueous solution with cupric-ion or ferric-ion catalysts. Air-oxidation was also conducted for a polysarcosine having one terminal sulfhydryl group. The product of the air-oxidation was fractionated by gel chromatography. The product analysis of the fully oxidized monofunctional polymer showed that the sulfhydryl groups were converted into disulfide bonds exclusively. There was no evidence for the interchange between two disulfide linkages or between a disulfide linkage and a sulfhydryl group during the air-oxidation. The analysis of the products from the bifunctional polysarcosine showed that they were composed of a series of cyclic “monomer,” “dimer,” “trimer,” and higher “oligomers.” The cyclic structure was characterized by the larger elution volume in the gel chromatogram than that for a linear homologue having the same molecular weight. The weight fraction of each cyclic oligomer was determined by gel chromatography. The fraction of cyclic monomer F₁ decreased monotonously with increasing the chain length. Smaller values of F₁ were observed with cupric-ion catalyst than with ferric-ion catalyst. The dependence of F₁ on the polymer concentration was much smaller than that expected from a simple competition mechanism between intra- and intermolecular reactions. These results indicate that the choice between intra- and intermolecular reactions is governed by the mode of the coordination of sulfhydryl groups to transition metal ions.     

Utilization of Soybean Products in Fish Paste Products

Large amounts of food-grade soybean products are consumed in fish product industries in Japan. To clarify the properties of soybean products desirable for fish processing, the kamaboko added with soybean products were evaluated by both sensory testing and instrumental measurements. The correlation between the suitability of soybean products for kamaboko and the basic chemical and functional properties of the soybean products was discussed. It was found that the “hardness” of the kamaboko added with soybean products correlated highly with the degree of denaturation of soy protein and with the amount of nitrogen of soybean products not dispersible in 3% sodium chloride aqueous solution.

It was also estimated that the textural properties of kamaboko added with soybean products could not be deduced from the textural properties of heat-coagulated gels of the corresponding soybean products.     

Mechanical properties of films and three-dimensional scaffolds made of fibroin and gelatin

Silk fibroin is a biocompatible and biodegradable material, which can be used in surgery and tissue engineering. To improve the cell adhesion on fibroin surface, gelatin can be added to the items made of fibroin. This work compares the mechanical properties of films and three-dimensional scaffolds made of fibroin and fibroin with gelatin. The addition of 30% gelatin to the fibroin scaffold does not change its microstructure or swelling. The addition of gelatin decreases the mechanical properties of films (decreases the Young’s modulus, the maximum strain and elongation) but increases the shear modulus of the scaffolds.     

The “Intrinsic” Thermal Conductivity of Some Wet Proteins in Relation to Their Hydrophobicity: Analysis on Gelatin Gel

Since the intrinsic thermal conductivity of protein cannot be measured directly, the apparent “intrinsic” thermal conductivity of gelatin was estimated on the basis of the most suitable heat conduction model. Among four models of heat conduction through heterogeneous material, the series layers model best described the experimental results for frozen gelatin gels of different concentrations. Then, the “intrinsic” thermal conductivity of frozen wet gelatin was estimated to be 0.61 [W/m·°C]. The “intrinsic” thermal conductivity of unfrozen wet gelatin was estimated on the basis of Filippov’s equation to be 0.38 [W/m·°C], since the unfrozen gelating gel seemed to be as homogeneous as the solution.     

The role of the cortex in indentation experiments of animal cells

We present a model useful for interpretation of indentation experiments on animal cells. We use finite element modeling for a thorough representation of the complex structure of an animal cell. In our model, the crucial constituent is the cell cortex—a rigid layer of cytoplasmic proteins present on the inner side of the cell membrane. It plays a vital role in the mechanical interactions between cells. The cell cortex is modeled by a three-dimensional solid to reflect its bending stiffness. This approach allows us to interpret the results of the indentation measurements and extract the mechanical properties of the individual elements of the cell structure. During the simulations, we scan a broad range of parameters such as cortex thickness and Young’s modulus, cytoplasm Young’s modulus, and indenter radius, which define cell properties and experimental conditions. Finally, we propose a simple closed-form formula that approximates the simulated results with satisfactory accuracy. Our formula is as easy to use as Hertz's function to extract cell properties from the measurement, yet it considers the cell’s inner structure, including cell cortex, cytoplasm, and nucleus.

     

Effects of Cellulose Nanofibers Filling and Palmitic Acid Emulsions Coating on the Physical Properties of Fish Gelatin Films

In this preliminary study, fish gelatin films with improved strength and water resistance were prepared from a dispersion of fish gelatin and carboxylated cellulose nanofibrils (CNF) by using the casting method, followed by subsequent coating with palmitic acid emulsion. The surface topography displayed a uniform distribution of the CNF particles in the gelatin films, but aggregation occurred at a CNF dosage of 4 wt% or higher. Due to the reinforcing effect of CNF, a dosage-dependent increase in the Young’s modulus and tensile strength was observed for the CNF-reinforced films. The addition of CNF also led to an obvious increase in thermal stability. Via surface coating, the emulsion at the 60:40 (w/w) ratio of palmitic acid to water showed excellent layer-forming and high adhesion properties, contributing to the significant improvement of water resistance. The enhanced properties of these fish gelatin films would promote their practical applications in edible packaging.     

Influence of altered geometry and material properties on tissue stress distribution under load in tendinopathic Achilles tendons – A subject-specific finite element analysis

Achilles tendon material properties and geometry are altered in Achilles tendinopathy. The purpose of this study was to determine the relative contributions of altered material properties and geometry to free Achilles tendon stress distribution during a sub-maximal contraction in tendinopathic relative to healthy tendons. Tendinopathic (n = 8) and healthy tendons (n = 8) were imaged at rest and during a sub-maximal voluntary isometric contraction using three-dimensional freehand ultrasound. Images were manually segmented and used to create subject-specific finite element models. The resting cross-sectional area of the free tendon was on average 31% greater for the tendinopathic compared to healthy tendons. Material properties for each tendon were determined using a numerical parameter optimisation approach that minimised the difference in experimentally measured longitudinal strain and the strain predicted by the finite element model under submaximal loading conditions for each tendon. The mean Young’s modulus for tendinopathic tendons was 53% lower than the corresponding control value. Finite element analyses revealed that tendinopathic tendons experience 24% less stress under the same submaximal external loading conditions compared to healthy tendons. The lower tendon stress in tendinopathy was due to a greater influence of tendon cross-sectional area, which alone reduced tendon stress by 30%, compared to a lower Young’s modulus, which alone increased tendon stress by 8%. These findings suggest that the greater tendon cross-sectional area observed in tendinopathy compensates for the substantially lower Young’s modulus, thereby protecting pathological tendon against excessive stress.     

Plasticizer Effects on Physical–Mechanical Properties of Solvent Cast Soluplus® Films

Soluplus® is a novel amphiphilic polymer that has been shown to enhance the solubility and drug dissolution rate of poorly soluble drugs. However, there still is a lack of information regarding the physical mechanical properties of Soluplus® with addition of the plasticizers. This study characterized the mechanical properties of Soluplus® with four different plasticizers. The plasticizers selected were polyethylene glycol 6, triethyl citrate, propylene glycol, and glycerin; they were studied at three different levels (15%, 20%, and 25% w/w). The effects of these plasticizers on the glass transition temperature, tensile strength, percent elongation, and Young’s modulus of free films made from Soluplus® were measured and the toughness and ratio of tensile strength to Young’s modulus were calculated. These results showed these four plasticizers are capable to plasticizing Soluplus® as indicated by the glass transition temperature lowering, tensile strength, and Young’s modulus while increasing the percent elongation and film toughness. Among the plasticizers tested, polyethylene glycol 6 showed greatest changed in the mechanical properties studied.     

Human annulus fibrosus material properties from biaxial testing and constitutive modeling are altered with degeneration

The annulus fibrosus (AF) of the intervertebral disk undergoes large and multidirectional stresses and strains. Uniaxial tensile tests are limited for measuring AF material properties, because freely contracting edges can prevent fiber stretch and are not representative of in situ boundary conditions. The objectives of this study were to measure human AF biaxial tensile mechanics and to apply and validate a constitutive model to determine material properties. Biaxial tensile tests were performed on samples oriented along the circumferential–axial and the radial–axial directions. Data were fit to a structurally motivated anisotropic hyperelastic model composed of isotropic extra-fibrillar matrix, nonlinear fibers, and fiber–matrix interactions (FMI) normal to the fibers. The validated model was used to simulate shear and uniaxial tensile behavior, to investigate AF structure–function, and to quantify the effect of degeneration. The biaxial stress–strain response was described well by the model (R ²?>?0.9). The model showed that the parameters for fiber nonlinearity and the normal FMI correlated with degeneration, resulting in an elongated toe-region and lower stiffness with degeneration. The model simulations in shear and uniaxial tension successfully matched previously published circumferential direction Young’s modulus, provided an explanation for the low values in previously published axial direction Young’s modulus, and was able to simulate shear mechanics. The normal FMI were important contributors to stress and changed with degeneration, therefore, their microstructural and compositional source should be investigated. Finally, the biaxial mechanical data and constitutive model can be incorporated into a disk finite element model to provide improved quantification of disk mechanics.     

Improving stress shielding following total hip arthroplasty by using a femoral stem made of β type Ti-33.6Nb-4Sn with a Young’s modulus gradation

Stress shielding-related bone loss occurs after total hip arthroplasty because the stiffness of metallic implants differs from that of the host femur. Although reducing stem stiffness can ameliorate the bone resorption, it increases stress at the bone–implant interface and can inhibit fixation. To overcome this complication, a novel cementless stem with a gradient in Young’s modulus was developed using Ti-33.6Nb-4Sn (TNS) alloy. Local heat treatment applied at the neck region for increasing its strength resulted in a gradual decrease in Young’s modulus from the proximal to the distal end, from 82.1 to 51.0 GPa as calculated by a heat transfer simulation. The Young’s modulus gradient did not induce the excessive interface stress which may cause the surface debonding. The main purpose of this study was to evaluate bone remodeling with the TNS stem using a strain-adaptive bone remodeling simulation based on finite element analysis. Our predictions showed that, for the TNS stem, bone reduction in the calcar region (Gruen zone 7) would be 13.6% at 2 years, 29.0% at 5 years, and 45.8% at 10 years postoperatively. At 10 years, the bone mineral density for the TNS stem would be 42.6% higher than that for the similar Ti-6Al-4V alloy stem. The stress–strength ratio would be lower for the TNS stem than for the Ti-6Al-4V stem. These results suggest that although proximal bone loss cannot be eliminated completely, the TNS stem with a Young’s modulus gradient may have bone-preserving effects and sufficient stem strength, without the excessive interface stress.     

"Big" human placental lactogen: disulfide-linked peptide chains.

“Big” human placental lactogen has been purified by affinity chromatography. On SDS¹-polyacrylamide disc gel electrophoresis, “big” hPL had a molecular weight of about 45,000. Following reduction with mercaptoethanol, a single band with a molecular weight of 23,000 was noted. These observations suggest that “big” hPL consists of two peptide chains linked by a disulfide bond.     

Dynamic mechanical and rheo-optical studies of collagen and gelatin

The frequency dependence of dynamic mechanical properties of rat tail tendon (RTT), enzyme-solubilized collagen membranes (ESC), AKM-23 dialysis membranes, and gelatin film have been measured at 110, 11, and 3.5 Hz from - 160 to 220°C. RTT and AKM-23 are devoid of a rubbery region; there are as many as six mechanical loss transitions. Gelatin and ESC membranes behave as rubbery materials above room temperature; only three tan δE peaks can be resolved for these materials. Strain birefringence was used to measure the crystalline and amorphous contribution of orientation induced by strain. Both the birefringence and the strain optical coefficient are sensitive to the amount of water in a sample. The effect of chemical swelling agents and of annealing on birefringence are described. Stress relaxation data on gelatin film were analyzed with the rubber elasticity theory to give the average number of chains per unit volume, the specific polarizability, the stress-birefringence ratio and the average molecular weight between hydrogen bonds were calculated. The intrinsic amorphous birefringence for “wet” gelatin film is 1.25 × 10^?2; it is estimated to be about 6 × 10^?2 for “dry” gelatin film.     

The role of disulfide bonds in maintaining the gel structure of bronchial mucus.

Solubilization of the gel phase of sputum by reduction with dithiothreitol and alkylation with iodoacetamide resulted in different gel filtration patterns when sputa from different patients were examined. Two extreme types of of behavior were identified; in one the glycoproteins were completely excluded from Sepharose 4B, and in the other all the glycoproteins penetrated the gel matrix to a certain extent. Pronase digestion of the products of reduction and alkylation of the former resulted in a gel filtration pattern similar to that obtained by reduction and alkylation alone in the latter. The disulfide bonds cleaved by dithiothreitol were labeled by reaction with [1-¹⁴C]iodoacetamide and the glycoproteins isolated. Pronase digestion of the labeled glycoproteins revealed that, although most of the cysteine residues occurred in peptide regions cleaved by Pronase, some were situated in resistant peptide regions. Structures are proposed for the bronchial glycoproteins isolated from the two extreme types of sputum. These structures consist of a glycoprotein subunit, resistant to Pronase and attached by covalent bonds to a “naked” peptide region. Whereas the glycoprotein subunits are similar in both types of sputum, the “naked” peptide is a continuous peptide chain in one type but a discontinuous peptide chain in the other.     

Limited Proteolysis and Reduction-carboxymethylation of Rye Seed Chitinase-a: Role of the Chitin-binding Domain in Its Chitinase Action

By a limited proteolysis with thermolysin, rye seed chitinase-a (RSC-a) was separated into a N-terminal cysteine-rich chitin-binding (CB-) domain (48 residues) and a catalytic (Cat-) domain (254 residues). The hydrolytic activity of the isolated Cat-domain toward soluble glycolchitin, was similar to that of RSC-a, but that toward insoluble colloidal chitin was 28% of that of RSC-a. Five disulfide bonds in the CB-domain were reduced with 2-mercaptoethanol (2-ME) in the absence of denaturing agents by an “all-or-none” process, that is, once the disulfide bond between Cysl5 and Cys42 in the CB-domain was cleaved, the remaining four disulfide bonds were reduced very easily. The reduced and carboxymethylated RSC-a completely lost the chitin-binding ability, but retained 50% of the hydrolytic activity toward colloidal chitin of RSC-a.

From these results, it was shown that RSC-a consists of a CB-domain and a Cat-domain connected by a flexible linker, and it was suggested that the CB-domain increases the hydrolytic action of Cat-domain toward insoluble chitin derivatives by binding to them.     

Effect of Crystallization State on the Gel Properties of Oleogels Based on β-sitosterol

Oleogels based on three different oils (sunflower oil, solid coconut oil and liquid coconut oil) were formulated using β-sitosterol. In general, an observed increase in crystallinity was correlated with an increase in the gel storage modulus and hardness. Addition of lecithin promoted the formation of needle-like crystals of β-sitosterol with a corresponding increase in strain tolerance and oil-trapping capacity for oleogels produced with liquid oils. However, the incorporation of β-sitosterol crystals with or without lecithin into oleogels containing solid coconut oil reduced its strain tolerance by interrupting the formation of continual radiolitic crystal structures. The use of sunflower oil (long chain fatty acids) was more favourable to the packing and growth of gelator crystals and the formation of an elastic gel, in comparison to liquid coconut oil (short chain fatty acids). Overall, the type and physical state of oil influence the formation of oil crystal network, thus affecting its gel properties. These findings allow the better understanding of β-sitosterol-based oleogels, providing opportunity to design for the application as a fat-replacer and lowering solid fat content.

     

Structural properties of starch-chitosan-gelatin foams and the impact of gelatin on MC3T3 mouse osteoblast cell viability

Background

This study examines the effects of adding gelatin to a starch-chitosan composite foam, focusing on the altered structural and biological properties. The compressive modulus of foams containing different gelatin concentrations was tested in dry, wet, and lyophilized states. MC3T3 mouse osteoblast cells were used to test the composite’s ability to support cell growth. The stability of the foams in α-MEM culture media with and without cells was also examined.

Results

It was found that for dry foams, the compressive modulus increased with increasing gelatin content. For foams tested in wet and lyophilized states, the compressive modulus peaked at a gelatin concentration of 2.5% and 5%, respectively. The growth of MC3T3 mouse osteoblast cells was tested on the foams with different gelatin concentrations. The addition of gelatin had a positive effect on the cell growth and proliferation.

Conclusion

The composite foam containing gelatin improved cell growth and is only dissolved by the growing cells at a rate influenced by the initial concentration of gelatin added to the foam.

     

First-principles study of phase stability and elastic properties in metastable Ti-Mo alloys with cluster structure

This paper provided a novel approach for evaluating phase stability and elastic properties in metastable Ti–Mo alloys with low Mo content by first-principles combined with cluster structure. In 54-atom body-centered-cubic supercell by substituting Ti atoms with 2–7 Mo atoms (7.1–23.0?wt% Mo), individual cluster structure of β-phase was constructed by ‘-Mo-Ti-Mo-’ cluster unit having the lowest cohesive energy. The distorted supercell was more stable than undistorted one at a low Mo content. With increasing Mo content, the density of state at Fermi level decreased, and bonding electron number increased, indicating β-phase stability was gradually promoted. Tetragonal shear elastic constant (C′?=?(C₁₁?–?C₁₂)/2), shear modulus (G₁₁₁) and anisotropy factor (A?=?C₄₄/C′) exhibited a fluctuation with Mo addition, while the change trend of A was opposite to C′ and G₁₁₁. Calculated Young’s modulus exhibited similar changing trend to the C′, implying that the softening of C′ resulted in low Young’s modulus of β-phase. Measured Young’s modulus exhibited significant difference from calculated one, which was mainly caused by formation of α″-martensite and ω-phase. The values of C′, G₁₁₁ and A were considered to associate with not only elastic properties of β-phase itself but also transition from β-phase to α″-martensite and/or ω-phase.     

Nanomechanical properties of wing membrane layers in the house cricket (Acheta domesticus Linnaeus)

Many insect wings change shape dynamically during the wingbeat cycle, and these deformations have the potential to confer energetic and aerodynamic benefits during flight. Due to the lack of musculature within the wing itself, the changing form of the wing is determined primarily by its passive response to inertial and aerodynamic forces. This response is in part controlled by the wing’s mechanical properties, which vary across the membrane to produce regions of differing stiffness. Previous studies of wing mechanical properties have largely focused on surface or bulk measurements, but this ignores the layered nature of the wing. In our work, we investigated the mechanical properties of the wings of the house cricket (Acheta domesticus) with the aim of determining differences between layers within the wing. Nanoindentation was performed on both the surface and the interior layers of cross-sectioned samples of the wing to measure the Young’s modulus and hardness of the outer- and innermost layers. The results demonstrate that the interior of the wing is stiffer than the surface, and both properties vary across the wing.