Some Textile Applications of Finite-element Analysis Part II: Finite Elements for Yarn Mechanics

The concepts of modal decomposition developed in an earlier paper are used to produce a three-dimensional element for aligned fibre assemblies. The element degrees of freedom are introduced and the chosen mode shapes of the element demonstrated. The finite element is tested by using simple material-property assumptions, and the element is verified against a theoretical model of the twisting of a single fibre about a solid core. The element is then verified qualitatively by modelling realistic yarn situations, and the resultant deformation plots are presented.     

Covalent attachment of single-stranded DNA to carbon paste electrode modified by activated carboxyl groups

A new method of the electrode modification and DNA immobilization for a biosensor is reported. Outer layer of a conventional carbon paste electrode (CPE) was modified with carboxyl groups by mixing stearic acid with the paste. Single-stranded deoxyribonucleic acid was attached to the modified electrode through a linker - ethylenediamine. Immobilization process was performed in the presence of activators - water soluble 1-ethyl-3(3′-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS). Stearic acid concentration and other experimental parameters of the procedure were optimized. Covalent immobilization of DNA on the electrode surface exhibits some advantages as compared to simple adsorption mainly due to the fact that nucleic acid chains are bound to an electrode surface by one end only and it ensures structural flexibility and increases hybridization without DNA leakage. Modified electrode with immobilized (21-mer) oligonucleotide as a specific probe was successfully applied in preliminary investigations for the detection of bar gene commonly used in genetically modified food.     

Immobilization of a nonspecific chitosan hydrolytic enzyme for application in preparation of water‐soluble low‐molecular‐weight chitosan

A nonspecific chitosan hydrolytic enzyme, cellulase, was immobilized onto magnetic chitosan microspheres, which was prepared in a well spherical shape by the suspension crosslinking technique. The morphology characterization of the microspheres was carried out with scanning electron microscope and the homogeneity of the magnetic materials (Fe₃O₄) in the microspheres was determined from optical micrograph. Factors affecting the immobilization, and the properties and stabilities of the immobilized enzyme were studied. The optimum concentration of the crosslinker and cellulase solution for the immobilization was 4% (v/v) and 6 mg/mL, respectively. The immobilized enzyme had a broader pH range of high activity and the loss of the activity of immobilized cellulase was lower than that of the free cellulase at high temperatures. This immobilized cellulase has higher apparent Michaelis–Menten constant K_m (1.28 mg/mL) than that of free cellulase (0.78 mg/mL), and the maximum apparent initial catalytic rate V_max of immobilized cellulase (0.39 mg mL^?1 h^?1) was lower than free enzyme (0.48 mg mL^?1 h^?1). Storage stability was enhanced after immobilization. The residual activity of the immobilized enzyme was 78% of original after 10 batch hydrolytic cycles, and the morphology of carrier was not changed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1334–1339, 2006     

树脂固定脂肪酶技术的研究

采用大孔树脂D3520作载体以载体涂布法来固定化脂肪酶,对固定化条件进行了优化并分析固定化酶的性能,在水分含量为3%~5%,pH 9.0,反应温度为40℃条件下,固定化酶具有最佳的催化活力(91.49 U/g).与游离酶相比,固定化酶具有更好的性能.     

A Temperature‐Controllable Microelectrode and Its Application to Protein Immobilization

This letter presents a smart integrated microfluidic device which can be applied to actively immobilize proteins on demand. The active component in the device is a temperature‐controllable microelectrode array with a smart polymer film, poly(N‐isopropylacrylamide) (PNIPAAm) which can be thermally switched between hydrophilic and hydrophobic states. It is integrated into a micro hot diaphragm having an integrated micro heater and temperature sensors on a 2‐micrometer‐thick silicon oxide/silicon nitride/silicon oxide (O/N/O) template. Only 36 mW is required to heat the large template area of 2 mm×16 mm to 40°C within 1 second. To relay the stimulus‐response activity to the microelectrode surface, the interface is modified with a smart polymer. For a model biomolecular affinity test, an anti‐6‐(2, 4‐dinitrophenyl) aminohexanoic acid (DNP) antibody protein immobilization on the microelectrodes is demonstrated by fluorescence patterns.     

Electrical Current Signatures of DNA Base Modifications in Single Molecules Immobilized in the α-Hemolysin Ion Channel

Nanopore technology holds high potential for next-generation DNA sequencing. This method operates by drawing an individual single-stranded DNA molecule through a nanoscale pore, while monitoring the current deflections that occur as the DNA passes through. Individual current levels for the four DNA nucleotides have been established by immobilization of an end biotinylated strand in the pore, in which the nucleotide of interest is suspended at the most sensitive region of the ion channel. Due to the inherent reactivity of DNA bases, many modified nucleotides in the genome exist as a result of oxidative and UV insults, among others. Herein, the current levels for common DNA damage lesions 8-oxo-7,8-dihydroguanine, spiroiminodihydantoin, guanidinohydantoin, uridine, abasic sites, thymine dimers, thymine glycol, and 5-iodocytosine were assessed through immobilization experiments. In some cases, the current difference between the damaged and canonical nucleotides was not well resolved; therefore, we took advantage of the chemical reactivity of the new functional groups present to make amine adducts that shifted the current levels outside the range of the native nucleotides. Among the adducts studied, only the 2-aminomethyl-18-crown-6 adduct was able to give a large current shift in the immobilization experiment, as well as being observed in a translocation experiment. The results show potential in providing current-level modulators for identification of some types of DNA damage. In principle, any DNA base modification that can be converted chemically or enzymatically into an abasic site could be identified in this way.     

天然蒙脱石/植酸酶复合载体制备及其植酸磷水解活性研究

通过吸附过程制备了天然蒙脱石/植酸酶复合载体并系统探讨其催化水解植酸磷活性。结果表明,天然蒙脱石固载植酸酶符合Elovich动力学模型,固载等温曲线满足Langmuir方程,植酸酶最大固载容量为1.48 mg/mg;天然蒙脱石/植酸酶复合载体作为微型固定化酶反应器催化水解植酸磷,同自由植酸酶相比较,温度耐受性、抗蛋白酶水解能力均有效改善;适宜的pH值适用范围为4.0~4.5;重复利用5次后酶活保留40%以上。天然蒙脱石/植酸酶复合载体作为饲料添加剂可有效减少植酸酶制剂投加量,提高植酸磷有效利用率,溯源性降低畜禽养殖业"磷"污染排放。