【作者】 苏晓霞；

【导师】 陈忠秀； 邓少平；

【作者基本信息】 浙江工商大学 ， 食品科学与工程， 2011， 硕士

【摘要】 食品安全问题是关系到国计民生和社会稳定的重大公共安全问题,近年来,食品质量安全问题日益突出,一直倍受世人的关注。因此,加快开发快速、灵敏、稳定的食品安全检测技术及产品势在必行。目前,农药、兽药和食品添加剂残留的检测广泛使用的方法是色谱质谱联用技术或生物免疫检测方法,这势必存在设备昂贵、样品前处理麻烦、样品检测数量有限、使用技能要求较高等问题,远远满足不了食品安全保障的需求。本课题提出基于分子识别原理,探索快速检测技术的新思路。以三聚氰胺这个食品安全的热点问题为切入点,设计合成了一个能与三聚氰胺发生相互作用的识别分子,探索了三聚氰胺与识别分子之间的相互作用过程,并借助可变色的聚联乙炔囊泡,构建了一个三聚氰胺可视化感受元件并对其初步应用进行了研究,为后期基于分子识别原理的快速检测技术方法的研究奠定了基础。本课题研究的内容有：(1)识别分子的合成及性质表征采用乳清酸作为亲水基,1,12-二氨基十二烷作为疏水链合成带有识别基团的bola型两亲分子——1,12-二乳清酸基十二烷基二胺盐(1,12-diaminododecane diorotate,简称DDO),通过傅里叶变换红外光谱(FT-IR)和核磁共振波谱(NMR)鉴定了产物的结构,用动态光散射技术(DLS)、荧光探针技术、等温滴定量热技术(ITC)、透射显微技术(TEM)、电化学工作站等详细研究了DDO分子的性质及其在水溶液中发生自聚集行为的机制,实验结果表明这种带有识别基团的DDO分子在水溶液中能自发形成囊泡结构。同时,研究了DDO分子与异电性传统表面活性剂混合体系形成囊泡的情况,ITC和TEM等结果表明上述混合体系在很宽的混和比例下都有囊泡存在,说明DDO与异电性传统表面活性剂混合体系有较强的形成囊泡的能力,尤其是SDS/DDO混合体系。另外,NaBr可以诱导SDS/DDO混合体系表现出较为丰富的聚集行为,包括囊泡,丝状,网状等结构,说明DDO聚集体的尺寸和形态具有可操控性。因此,DDO分子带有的分子识别基团使其具备作为识别分子的潜力,DDO分子的两亲性使其在溶液中聚集为囊泡,为分子识别提供更大的界面,为实现三聚氰胺的检测奠定了基础。(2)DDO与三聚氰胺识别过程的研究本研究发现三聚氰胺具有荧光特性,三维荧光光谱中,当激发波长为250nm时,发射波长为360 nm附近有较强的荧光信号。同时,由于DDO的亲水部分既是氢键的供体又是氢键的受体,可以和三聚氰胺形成氢键,这种分子间的相互作用使三聚氰胺的荧光猝灭。研究还发现,DDO分子聚集形成囊泡后与其单体分子相比对三聚氰胺的荧光猝灭效率更高。DDO使三聚氰胺的荧光发生猝灭涉及两种机制,当三聚氰胺浓度较低时(5×10-5 mol/L),发生静态猝灭,当三聚氰胺浓度较高时(2×10-3mol/L),同时发生动态猝灭和静态猝灭。ITC测定的三聚氰胺与DDO相互作用的热力学参数显示吉布斯自由能(△G)是负值,说明两者之间的相互作用是自发进行的。低场脉冲核磁测定三聚氰胺与DDO混合体系的横向驰豫时间T2,表明DDO分子降低了三聚氰胺和水的结合度,DDO和三聚氰胺之间形成了稳定的氢键。因此,DDO可以作为检测三聚氰胺的识别分子。(3)三聚氰胺可视化感受元件的初步应用研究以聚联乙炔变色囊泡作为DDO分子检测三聚氰胺的载体,构建了一个三聚氰胺可视化感受元件。通过DDO的疏水链与变色囊泡的疏水链之间的吸引力将其锚定于囊泡中,构造一种将检测与显示集为一体的聚联乙炔变色囊泡,分子识别的过程通过变色囊泡的颜色改变而反映,由此初步实现三聚氰胺的可视化检测。为食品中三聚氰胺的检测提供了快速、高效、绿色的新方法和途径,更重要的是可以藉此构建基于分子识别原理的快速检测平台。更多还原

【Abstract】 Food safety is an important social problem, which directly influences national economy, people’s livelihood and social stability. Recent years, the high incidence of food safety events attracts much attention. Therefore, it is imperative to accelerate the exploitation of rapid, sensitive and stable detection technologies and products of food safety.In recent years, detection and analysis technique for pesticide, veterinary drug and additive rudimental are chromatograph/mass spectrum tandem detecting technique, immunology and biological method. But they are greatly constrained by high price of instrument, long time of experiment, complex pretreatment, limited units of test sample, high level of skill and other factors, so they could not meet the food safety requirements. The paper explored new ideas of rapid detection technique based on molecular recognition. The article taken the hot issues of food safety——melamine as key point and designed and synthesised a molecular probes to interact with melamine. The paper also explored the recognition process of intermolecular interaction.The preliminary visualization sensor was designed and constructed, and several tests were performed to detect the concentration of melamine in solution. All these settled the foundation for the further rapid detection methodology based on molecular recognition.The main research work is as follows:(1) The design, synthesis and characterization of host molecules for recognition.1,12-diorotate diaminododecane (DDO) was synthesized by L-orotic acid and 1,12-dodecanediamine and the structure of DDO was characterized by fourier transform infrared spectrometer (FTIR) and nuclear magnetic resonance (NMR). The properties and self-aggregation behavior of DDO in water were determined by dynamic light scattering (DLS), fluorescence spectroscopy, isothermal titration calorimetry (ITC), transmission electron microscope (TEM) and electrochemical workstation. The experiment results showed that DDO itself could form vesicles easily in aqueous solutions with molecular recognition function moieties. Meanwhile, vesicles formation in DDO/conventional surfactant mixed systems was studied. ITC and TEM results revealed that vesicles existing in the above mixed systems, indicating the strong vesicle formation ability in DDO/conventional surfactant mixed systems, especially in SDS/DDO mixed system. Moreover, it was identified that sodium bromide could induce the transition from vesicle to abundant aggregation behaviors, including filiform texture, reticular formation and so on. Therefore, the size and shape of vesicles could be controled by varying conditions. In conclusion, DDO had great potential as a host molecular for detecting melamine. These settled the foundation for the further application study. (2) The interaction of melamine and DDO during the recognition process.It was found that melamine had favorable fluorescence property which exaion wavelengthλex=250 nm and the emission wavelengthλem=360 nm. Meanwhile, DDO interacts with melamine though complementary hydrogen bonding easily based on its proton acceptors and donors characters in hydrophilic group. Intermolecular interaction between DDO and melamine lead to fuorescence quenching of melamine. It was also found that the fluorescence of melamine was quenched more effectively by the spontaneously formed vesicles than by the monomers of the surfactant. Two mechanisms were involved in the fluorescence quench process. At lower concentration (5×10-5 mol/L), the fluorescence of melamine was found to be quenched by static complex formation. While at higher concentration (2×10-3mol/L), both static and dynamic quenching mechanisms coexisted in interaction process. Thermodynamic parameters measured by ITC showed that the free energy (ΔG) was negative, indicating that binding of DDO molecules with melamine was favorable energetically.Transverse relaxation T2 measured by low field pulsed NMR showed that a loose bonding between melamine and water, implying hydrogen bond formation between DDO and melamine. All of the results evidenced the molecular recognition taking place between DDO and melamine.(3) Application research of melamine visualization sensor preliminary.Polydiacetylene vesicles were selected as carrier of DDO dectecting melamine. The functional molecules DDO were successfully incorporated into the polydiacetylene vesicles by interaction between hydrophobic chains, therefrom, constructing a vesicle which set detection and discoloration as one. The process of molecular recognition could be reflected by the color change of polydiacetylene vesicles. Thus, DDO molecular already realised detecting melamine preliminary. These provided a fast, efficient, green way to detect melamine in food system and constructed a new platform to comprehensive, rapid, accurate food safety testing.更多还原