磁响应交联糖化酶聚集体的制备及催化特性

提出了一种采用羧基磁性纳米粒子制备杂化磁响应交联酶聚集体(M-CLEAs)的方法。表面羧基修饰的约10 nm的磁性纳米粒子与酶分子表面的氨基位点通过静电相互作用,形成复合物,在磁场作用下可将磁性纳米粒子-酶复合物从溶液中分离,经戊二醛交联即形成M-CLEAs。传统的表面氨基修饰的磁性纳米粒子与酶需在沉淀剂作用下,从溶液中分离,而后采用戊二醛共交联,而本方法无须沉淀剂,过程更为简化。以糖化酶为对象,对该过程的影响因素(交联时间、pH、酶浓度、戊二醛浓度等条件)进行了探索,并对制得的M-CLEAs的酶学性质进行了较为详细考察。结果表明,最优制备条件为:酶浓度1 mg·ml-1,磁流体浓度10 mg·ml-1,戊二醛浓度0.25%(质量体积比),在pH 6.0下交联反应6 h,最终载酶量可达80 mg·g^(-1)、比活为50 U·mg^(-1)。制得的固定化酶pH稳定性、热稳定性和储存稳定性均显著改善,可实现糖化酶重复使用10次,仍保留接近60%的酶活。

磁流体结构的Lattice-Boltzmann方法模拟

本文运用Lattice-Boltzmann(LB)方法建立了宏观静止磁流体模型,提出磁性聚集体概念,充分考虑了磁性颗粒受到的各种内力与外力包括重力、布朗力、vanderWaals相互作用及静磁相互作用,对无外加磁场及外加竖直均匀磁场时磁流体的结构进行了模拟,并分析了磁能与热能之比对磁流体系统中粒子分布形态的影响。模拟结果表明:无外加磁场时磁流体结构易失去稳定性,外加均匀磁场时磁流体粒子沿外磁场方向排列,随着磁热能比例的增大,外磁场对粒子分布的影响逐渐明显。

Rapid, cost-effective DNA quantification via a visuallydetectable aggregation of superparamagnetic silicamagnetite nanoparticles

DNA and silica-coated magnetic particles entangle and form visible aggregates under chaotropic conditions with a rotating magnetic field, in a manner that enables quantification of DNA by image analysis. As a means of exploring the mechanism of this DNA quantitation assay, nanoscale SiO2-coated Fe304 （Fe3O4@SiO2） particles are synthesized via a solvothermal method. Characterization of the particles defines them to be -200 nm in diameter with a large surface area （141.89 m2/g）, possessing superparamagnetic properties and exhibiting high saturation magnetization （38 emu/g）. The synthesized Fe3O4@SiO2 nanoparticles are exploited in the DNA quantification assay and, as predicted, the nanoparticles provide better sensitivity than commercial microscale Dynabeads for quantifying DNA, with a detection limit of 4 kilobase-pair fragments of human DNA. Their utility is proven using nanoparticle DNA quantification to guide efficient polymerase chain reaction （PCR） amplification of short tandem repeat loci for human identification.