Solubilization of Myofibrils and Inhibition of Autolysis of Squid Mantle Muscle by Sodium Citrate

ABSTRACT:  The effects of organic salts (sodium (Na)-citrate, Na-gluconate, and Na-succinate) on the solubilization of myofibrillar proteins and the inhibition of autolysis of squid mantle muscle were investigated. All of the organic compounds dissolved myofibrils as NaCl did. Na-citrate showed the strongest ability with half dissolving at 0.06 M. Half dissolving by Na-gluconate, Na-succinate, and NaCl were 0.27, 0.21, and 0.27 M, respectively. Dissolving myofibrils by Na-citrate was not accompanied by the acceleration of autolysis. Na-citrate above 0.25 M almost completely inhibited the autolysis. The inhibition of autolysis by Na-gluconate and Na-succinate was much less than that of Na-citrate. Consequently, it was concluded that Na-citrate was the organic salt to dissolve squid myofibrils without inducing autolysis.     

A Rapid and Simple Method for the Determination of 2-Alkylcyclobutanones in Irradiated Meat and Processed Foods

A rapid and simple method has been developed for the determination of 2-alkylcyclobutanone, 2-dodecylcyclobutanone (DCB), and 2-tetradecylcyclobutanone (TCB) in irradiated meat and processed foods. The procedure consists of extraction with n-hexane, following defatting and cleanup with a silica gel mini-column before gas chromatograph–mass spectrometry analysis. The method was evaluated using samples of beef, pork, Parmesan cheese, fried chicken, hamburger, gyoza (Chinese dumplings), and gyudon (boiled beef and onion seasoned with soy sauce and sugar). The recoveries of spiked DCB were 67–88 %, and those of TCB were 70–86 %. Furthermore, the method could detect DCB and TCB from samples irradiated at 1.0 and 2.6 kGy at levels dependent on dose; DCB and TCB were not detected in any nonirradiated samples. The method did not require special equipment, such as Soxhlet extraction, accelerated solvent extraction, or supercritical fluid extraction, for sample preparation. Thus, this method would be useful for determining DCB and TCB levels in irradiated meat and processed foods.     

The Calcium Phosphate Matrix of FGF-2-Apatite Composite Layers Contributes to Their Biological Effects

The purpose of the present study was to fabricate fibroblast growth factor (FGF)-2-apatite composite layers on titanium (Ti) pins in one step at 25 °C using a supersaturated calcium phosphate (CaP) solution, and to evaluate the physicochemical characteristics and biological effects of the coated Ti pins compared with coated Ti pins fabricated at 37 °C. Ti pins were immersed in a supersaturated CaP solution containing 0.5, 1.0, or 2.0 µg/mL FGF-2 at 25 °C for 24 h (25F0.5, 25F1.0, and 25F2.0) or containing 4.0 µg/mL FGF-2 at 37 °C for 48 h (37F4.0). Except for the 25F0.5, the chemical compositions and the mitogenic activity levels of FGF-2 of the composite layers formed by these two methods were similar, except for the Ca/P molar ratio, which was markedly smaller at 25 °C (1.55–1.56 ± 0.01–0.02, p = 0.0008–0.0045) than at 37 °C (1.67 ± 0.11). Thus, either the apatite was less mature or the amount of amorphous calcium phosphate was higher in the composite layer formed at 25 °C. In vivo, the pin tract infection rate by visual inspection for 37F4.0 (45%) was lower than that for 25F1.0 (80%, p = 0.0213), and the rate of osteomyelitis for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0341). The extraction torque for 37F4.0 (0.276 ± 0.117 Nm) was higher than that for 25F0.5 (0.192 ± 0.117 Nm, p = 0.0142) and that for 25F1.0 (0.176 ± 0.133 Nm, p = 0.0079). The invasion rate of S. aureus for 37F4.0 (35%) was lower than that for 25F0.5 (75%, p = 0.0110). On the whole, the FGF-2-apatite composite layer formed at 25 °C tended to be less effective at improving fixation strength in the bone-pin interface and resisting pin tract infections. These results suggest that the chemistry of the calcium phosphate matrix that embeds FGF-2, in addition to FGF-2 content and activity, has a significant impact on composite infection resistance and fixation strength.     

采用圆二色谱法研究冬夏鲢鱼鳞胶原蛋白的稳定性

采用圆二色谱法,研究比较了冬夏季鲢鱼鳞胶原蛋白的热稳定性。结果表明,对胶原蛋白溶液于30℃,33℃加热时,冬季鱼鳞胶原蛋白发生解螺旋现象,而夏季鱼鳞胶原仍保持完整的三螺旋结构;变性温度曲线显示,夏季样品的变性温度为36℃,而冬季样品出现2个峰值,分别为30℃和34℃。结果表明,夏季鲢鱼鳞胶原蛋白的热稳定性高于冬季胶原蛋白,这种不同可能与冬夏季鲢鱼生长环境温度的差异有关。     

X-ray absorption of gold nanoparticles with thin silica shell

Silica-coated gold (Au) nanoparticles were prepared and their morphological and X-ray absorption properties were investigated. These core-shell type nanoparticles are very stable in aqueous media and may be suitable for an X-ray contrast agent in biological systems. Transmission electron micrographs confirmed well-separated and relatively homogeneous morphology of the nanoparticles in highly concentrated colloids. Peak position for Au plasmon resonance was red-shifted with increasing shell thickness. X-ray absorption by the colloids of silica-coated Au nanoparticles was stronger than that by those of silica-coated Agl nanoparticles, a recently investigated X-ray contrast agent, at similar experimental conditions.     

Enumeration of fungi in fruits by the most probable number method

In this study, enumeration methods for fungi in foods were evaluated using fruits that are often contaminated by fungi in the field and rot because of fungal contaminants. As the test methods, we used the standard most probable number (MPN) method with liquid medium in test tubes, which is traditionally used as the enumeration method for bacteria, and the plate-MPN method with agar plate media, in addition to the surface plating method as the traditional enumeration method for fungi. We tested 27 samples of 9 commercial domestic fruits using their surface skin. The results indicated that the standard MPN method showed slow recovery of fungi in test tubes and lower counts than the surface plating method and the plate-MPN method in almost all samples. The fungal count on the 4th d of incubation was approximately the same as on the 10th d by the surface plating method or the plate-MPN method, indicating no significant differences between the fungal counts by these 2 methods. This result indicated that the plate-MPN method had a number agreement with the traditional enumeration method. Moreover, the plate-MPN method has a little laborious without counting colonies, because fungal counts are estimated based on the number of plates with growing colonies. These advantages demonstrated that the plate-MPN method is a comparatively superior and rapid method for enumeration of fungi.     

Film-forming amphiphilic silsesquioxane hybrids prepared by hydrolytic co-condensation of hydroxyl-functionalized and fluorinated triethoxysilanes

Amphiphilic silsesquioxanes-based hybrids were synthesized by hydrolytic co-condensation of a hydroxyl-functionalized triethoxysilane precursor derived from 2-hydroxyethyl acrylate (HEA) and fluorinated triethoxysilane precursors derived from 1H,1H,5H-octafluoropentyl acrylate (OFPA) and 2,2,2-trifluoroethyl acrylate (TFEA). Hydrolytic co-condensations of two functionalized triethoxysilane precursors proceeded as homogeneous systems in N,N-dimethylformamide (DMF) to afford amphiphilic silsesquioxanes hybrids, which were soluble in a variety of solvents, depending on the composition. The structure of the constitutional unit of the hybrids was confirmed by the results of NMR and FT-IR measurements. Scanning force microscope (SFM) measurements indicated the formation of spherical hybrids having relatively narrow size distributions (average particle diameter < 3.0 nm) without aggregation. The sizes of the hybrids were also confirmed by X-ray diffraction (XRD). Flexible semitransparent films were obtained from the amphiphilic silsesquioxane hybrids prepared by hydrolytic co-condensations at suitable feed ratios. The organic-inorganic amphiphilites exhibited a high density of chemically bonded peripheral fluoroalkyl and hydroxyalkyl groups, in which various characteristic properties involving amphiphilicity, film-forming property, refractive index, responsive surface, nanometer size, and narrow size distribution can be manipulated by varying the composition in the feed.     

High-throughput screening of improved protease inhibitors using a yeast cell surface display system and a yeast cell chip

Protease-targeted inhibitors have been promising pharmaceuticals. Here, we combined a yeast cell surface display system with a yeast cell chip for the high-throughput screening of protease inhibitors, and succeeded in improving the activity of a protease inhibitor.     

Optical hydrogen sensing method using temperature-sensitive luminophore on porous palladium

A new hydrogen sensing method of luminescence-based hydrogen sensors is presented. This method uses a porous palladium and temperature-sensitive luminophores of europium(III)thenoyltrifluoacetonate to selectively adsorbs hydrogen molecules that generates heat on the palladium surface. The luminophores translate this heat to the luminescent signal. This hydrogen sensing mechanism combines processes of hydrogen adsorption, thermal quenching, and excitation. The sensitivity of the resultant system is over 60 times better than that of the reflectance-based sensing system using a bulk palladium. The change in the luminescent signal increases as increasing the hydrogen concentration of the gas as well as the injection time.