【作者】 郭青青；

【导师】 刘继锋；

【作者基本信息】 聊城大学 ， 分析化学， 2010， 硕士

【摘要】 人体及食品中的氧化反应是人们广泛关注的研究课题,氧化代谢产生的能量对于细胞的存活具有十分重要的意义,但是氧化过程会产生一系列的氧化自由基。如果生物体内产生过量的自由基,打破自由基与抗氧化剂的平衡,那么自由基的破坏能力就会超过体内抗氧化剂（如超氧化物歧化酶、过氧化氢酶、过氧化物酶等等）的保护能力并且会通过氧化细胞膜、损伤DNA或者酶等阻碍细胞本身的自我修复功能,导致生物大分子功能和结构损伤、细胞破坏、凋亡或死亡。在食品科学领域,这种氧化反应也会引起食物变质（如营养价值、颜色、气味、质地以及食品安全性的改变）,据统计,世界上大约有一半的水果蔬菜存放期间发生腐败变质反应。因此,建立快速、有效的抗氧化剂分析方法对于生命科学和食品科学分析具有很好的理论和应用研究价值。本文具体工作如下:1. Fe-DTPA,血红素,血红蛋白/TiO₂纳米颗粒修饰的抗氧化剂传感器检测技术首先将铟锡氧化物玻璃用二氧化钛纳米颗粒涂覆好,然后用来吸附含铁化合物或蛋白质。当加负电位的时候电极表面的溶解氧就会还原成过氧化氢,体系中产生的过氧化氢又可以将Fe^Ⅱ氧化成Fe^Ⅲ,继而Fe^Ⅲ的电化学还原就会使催化电流增加。在抗氧化剂存在的情况下,过氧化氢被淬灭,催化电流就会减小,电流的减小程度与抗氧化剂的量呈正比关系。并且提出了抗氧化剂对过氧化氢清除能力的动力学模型。这种电极的使用使得抗氧化剂检测变得非常简单:将传感器浸入样品溶液（空气饱和的溶液就可以）,进行阴极极化扫描,读出抗氧化能力的值就可以了。本研究工作可以作为以前基于羟基自由基和超氧阴离子自由基清除能力检测的一种补充方法,但是这种传感器非常易于制造和使用。2.羟基自由基在DNA上传递距离的研究基于DNA的电子传递原理,制备了可受磁场调节的ds-DNA-Fe₃O₄@TiO₂电极。首先制备好巯基DNA修饰电极,然后将目标DNA末端的氨基进行氨羧络合反应,接着进行DNA杂交反应,当加入嵌入剂AQMS或MB时,用方波伏安法检测,得到AQMS或MB嵌入DNA双链的经典图形,说明DNA双链形成。最后再将杂交完成的ds-DNA与磁性纳米颗粒结合起来,当用紫外照射的时候,产生的羟基自由基就会损伤DNA。为研究羟基自由基在DNA上的传递距离,加上外界磁场进行调节,观察磁场对不同长度的DNA受紫外照射损伤的调节情况,巧妙地运用DNA的双链部分作为参照,以DNA的单链部分作为羟基自由基在DNA单链上传递距离的标尺,计算了羟基自由基在DNA上的扩散作用距离。更多还原

【Abstract】 Oxidation in vivo or in the diet has aroused widespread concern.Oxidative metabolism is of great importance for the survival of cell. But also has its negative side, side effect is it can led to oxidant caused by free radicals or other reactive oxidant species, which produced during the metabolism process. More and more evidence can prove that, these species are able to form a control mechanism in a variety of organisms. The destructive power of excess radicals usually exceed protection mechanisms（such as superoxide dismutase, catalase, peroxidase, etc.） and will prevent self-healing capabilities of cell through oxidant membrane or damage DNA, eventually lead to cell damage or death （eg apoptosis）.However, the mechanism of the reactive oxygen species has not yet been solved. The oxidation reaction is one of the factors, which causing food spoilage（such as changes in the nutritional value, color, odor, texture, as well as food safety）. It is estimated that, there are about half of the fruits and vegetables spoiled due to expired harvest time. Thus,it is very necessary to establish a good defense mechanism and an efficient method to detect it. The main works are as follows:1. Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed ElectrodesAntioxidant amperometric sensors based on iron-containing complexes and protein modified electrodes were developed. Indium tin oxide glass was printed with TiO₂ nanoparticles, onto which iron-containing compounds and protein were adsorbed. When applied with negative potentials, the dissolved oxygen is reduced to H₂O₂ at the electrode surface, and the H₂O₂ generated in situ oxidizes Fe^II to Fe^III, and then electrochemical reduction of Fe^III therefore gives rise to a catalytic current. In the presence of antioxidants, H₂O₂ was scavenged, the catalytic current was reduced, and the decreased current signal was proportional to the quantity of existing antioxidants. A kinetic model was proposed to quantify the H₂O₂ scavenging capacities of the antioxidants. With the use of the sensor developed here, antioxidant measurements can be done quite simply: put the sensor into the sample solutions （in aerobic atmosphere）, perform a cathodic polarization scan, and then read the antioxidant activity values. The present work can be complementary to the previous studies of antioxidant sensor techniques based on OH radicals and superoxide ions scavenging methods, but the sensor developed here is much easier to fabricate and use.2. How far can hydroxl radical translate on DNA helix?Based on the principles of DNA charge transfer, we made a kind of electrode that can be regulated by the magnetic field, which was denoted as ds-DNA-Fe₃O₄@TiO₂. First prepare SH-DNA modified electrode, then prepare target DNA （with amino on the terminal）solution ,and carry on amino-carboxyl complex reaction. In order to remove DNA which is non-specific adsorpted on the electrode surface ,put the SH-DNA modified electrode in to MCH solution for a period of time. When perform hybridization reaction, add intercalator AQMS or MB, then test with OSW voltammograms. Put the electrode under Uv illumination, OH radicals produced during this process will damage DNA. In order to study the transmission distance of hydroxyl radical on DNA , we add a magnet to adjust the level of DNA damage.更多还原