低聚壳聚糖几何结构和物理化学属性的理论研究

运用密度泛函B3LYP/6-31G+(d)方法对gg构象的低聚壳聚糖进行了结构优化、频率计算和电子结构,并用更高精度的WB97XD/6-311+G(d,p)方法计算了平均结合能及零点能校正,分析了热力学性质.结果表明,由于低聚壳聚糖中的氢键作用,使其形成螺旋结构;聚合度的增加,使平均结合能随之下降,结构的稳定性增强;在降解过程中,均为放热反应,验证了利用降温来提高降解产率的实验的可行性;此外,聚合度的增加,使能隙减小且快速收敛于聚合度为7的6.99 eV,稳定的反应活性与实验相符;HOMO、LUMO的电子密度分布表明,化学活性集中在C2位的氨基、C6位的羟基以及链的两端位置.该结果对低聚壳聚糖模型的建立和低聚壳聚糖降解过程、活性位置以及物理化学属性的尺寸依赖等现象的研究有着指导意义.     

高效液相色谱-电化学(库仑电极)阵列检测技术用于植物内源激素等小分子物质的差异显示

以壳寡糖为诱导物处理烟草植株,利用高效液相色谱-电化学(库仑电极)阵列检测技术检测不同处理时间植物体内内源激素的变化情况及其他小分子物质的差异显示。所用色谱柱为Hypersil BDS C18 柱(4.6 mm i.d.×200 mm, 5 μm),八通道电化学阵列检测器(八个电极)的检测电势依次为-200,300,400,500,600,700,800,850 mV。结果表明,茉莉酸(JA)和赤霉酸(GA)含量在用壳寡糖处理6 h时达到高峰,吲哚乙酸(IAA)含量在处理8 h时达到高峰。处理后烟草植株产     

Oligochitosan-modified three-dimensional graphene free-standing electrode for electrochemical detection of imidacloprid insecticide

A simple sensor based on an oligosaccharide-modified three-dimensional graphene (OCS-3D-G) free-standing electrode was developed for the electrochemical determination of the insecticide imidacloprid (IDP). OCS can interact with graphene oxide sheets by π–π and electrostatic interactions, leading to graphene oxide sheets arranged as regular and dense porous structures. T herefore, compared with other modifier carbohydrates, OCS-3D-G is more suitable for electrochemical sensing. OCS-3D-G was synthesized by a hydrothermal method and then fabricated as an electrochemical sensor, and its characterization was done and electrochemical behavior studied in detail. T he optimized sensor showed good reproducibility, selectivity, and stability, and responded linearly over a wide concentration range (1.0–50.0 μM) w ith a limit of detection (LOD) of 0.51 μM. F inally, the proposed sensor was used for the determination of IDP in brown rice, and the results were in line with those obtained from high-performance liquid chromatography (HPLC). It is thereby shown that the developed free-standing electrode is simple and cheap and can be used as a disposable electrode.     

Effect of Soft Preheating of Bovine Serum Albumin on the Complexation with Oligochitosan: Structure and Conformation of BSA in the Complex

Phase analysis, spectroscopic, and light scattering methods are applied to investigate the peculiarities of the interaction of oligochitosan (OCHI) with native and preheated bovine serum albumin (BSA) as well as the conformational and structural changes of BSA in BSA/OCHI complex. As shown, untreated BSA binds with OCHI mainly forming soluble electrostatic nanocomplexes, with the binding causing an increase in BSA helicity without a change in the local tertiary structure and thermal stability of BSA. In contrast, soft preheating at 56 °C enhances the complexation of BSA with OCHI and slightly destabilizes the secondary and local tertiary structures of BSA within the complex particles. Preheating at 64 °C (below the irreversible stage of BSA thermodenaturation) leads to further enhancement in the complexation and formation of insoluble complexes stabilized by both Coulomb forces and hydrophobic interactions. The finding can be promising for the preparation of biodegradable BSA/chitosan-based drug delivery systems.