圆二色谱原理与应用备课讲稿.ppt

从 CD 谱分析准确性 对全 a 、 a / b 和变性蛋白质的准确度 90-100% 对 a + b 的准确度为 85% 对全 b 的准确度为 75% Applications of CD in structural biology ? Determination of secondary structure of proteins that cannot be crystallised ? Investigation of the effect of e.g. drug binding on protein secondary structure ? Dynamic processes, e.g. protein folding ? Studies of the effects of environment on protein structure ? Secondary structure and super-secondary structure of membrane proteins ? Study of ligand-induced conformational changes ? Carbohydrate conformation ? Investigations of protein-protein and protein-nucleic acid interactions ? Fold recognition CD 实验要点 仪器操作及参数 : Nitrogen flushing Flushing the optics with dry nitrogen is a must: ? Xe lamp has a quartz envelope , so if operated in air itll develop a lot of ozone, harmful for the mirrors ? below 195nm oxygen will absorb radiation 氮气流量 15-20 for 180nm 20 for 180nm 温度 : 圆二信号同紫外和荧光一样对温度十分敏感 实验平行体系温度要保持一致 房间空调 , 同时仪器控温 HT plot ? The HT plot is very important, since readings above 600-650V mean that not enough light is reaching the detector so a sample dilution or the use of shorter path cell are required. ? Furthermore the HT plot is in realty a single beam spectra of our sample, since there is a direct relation between HT and sample absorbance. By data manipulation HT conversion into absorbance and buffer baseline subtraction is possible. Alternatively single beam absorbance scale can be used already in CH2 during data collection, loosing however a bit the alerting functions of this channel. 圆二色谱 Circular Dichroism (CD) 原理与应用 光的性质：波粒二象性诞生 人类对光的研究起源很早，但对光本质的认识经历了一个较漫长 的过程。光究竟是波还是粒子？光的波动说与微粒说之争从十七世纪 初开始， 其间 牛顿、惠更斯、托马斯．杨、菲涅耳、爱因斯坦、波尔 等多位著名的科学家努力揭开了遮盖在“光的本质”外面那层扑朔迷离的 面纱，至二十世纪初以光的波粒 二象性告终，前后共三百多年的时间。 粒子性：光是某种粒子即光量子，具有粒子的性质 如 反射，散射等现象。 波动性：即光具有波动性，有衍射、干涉等性质 墨子和他的学生做了世界上最早的“小孔成像”实验， 并对实验结果作出了光沿直线传播的科学解释， 并用此原理解释了物体和投影的关系。 爱因斯坦提出了光量子论，解释了光电现象， 揭示了微观客体的波粒二重性 光源发射光量子 从演示中可以看出：光源发射的单个光量子的运动轨迹是一个轨迹为余弦 函数的简谐振动 轨迹方程为 x ＝ Acos （ ωt ＋ φ