谈谈实验室离心机高速离心的工作原理和特点
通常情况下，制备型超高速（preparative super-speed）实验室离心机高速离心的原理有差速离心（differential centrifugation）和密度梯度离心（density gradient centrifugation）两种。其中，差速离心法是相对更为常用的方法。
Usually preparative super speed laboratory centrifuge's working principle is known as either differential centrifugation or density gradient centrifugation, among which, the differential centrifugation is more commonly used.
实验室高速离心机差速离心是采用逐渐增大离心力的方法来达到使样品溶液中的各种成分沉降分离的目的。具体操作步骤是：首先在离心管中盛满同质均一的样品溶液，设定一定速度一定时间离心后溶液会分成上清液和沉淀物两部分；去掉*次离心的沉淀物，增大离心力继续离心上清液以沉积所需的离子。值得注意的是，两次离心的时间都必须选择得当才能达到所需的分离纯度。
The differential centrifugation method used in lab high speed centrifuge works in this way, separating different elements of the sample solution via multi-centrifuge powered gradually differently. Following is the detail operation, firstly fill the centrifuge tube with uniform solution and centrifuge it for a certain time to divide which into liquid supernatant and precipitate; next get rid of the precipitate and centrifuge the liquid supernatant with an increased power so as to get whatever you need. What worth mentioning is that the two centrifugation period must be carefully set to get the needed centrifugation fineness.
相对而言，差速离心的操作更为简单，而密度梯度离心的分离纯度更高。离心机密度梯度离心法能达到很好的分辨率，它能使溶液中所有的组份分离。密度梯度分离通常有速率区带法（rate zonal）和等密度离心法（isopycnic）两种。前者的依据是溶液中不同粒子的尺寸大小和沉积速度不一，而后者的依据是不同粒子的密度不同。
Comparatively speaking, the differential centrifugation operates much easier, yet the density gradient centrifugation method comes up with much higher fineness. That is to say, the density gradient centrifugation can separate all element from each up tide and clean. It usually works in two ways, rate zonal and isopycnic. Rate zonal works because that different elements in the solution has different sizes and thus deposition rate while the isopycnic works because of the different density of different elements in the solution.
采用密度梯度分析法离心时，梯度形状至关重要。线性梯度（linear gradient）是zui常用的。 它可以用来分离蛋白质、酶和植物病毒等，等速型梯度（constant speed gradient）适用于分离脂蛋白；分离整细胞和亚细胞采用的则是阶梯型梯度（stage-wise gradient）。
The gradient shape plays a key role when using density gradient centrifugation. The linear gradient is the most commonly used shape. It can be used to centrifuge protein, enzyme and plant virus, the constant speed gradient shape can be used to centrifuge lipoprotein and the stage-wise gradient can be used to centrifuge whole cell and subcellular.
采用密度梯度分析法离心后，区带样品的回收方法也是多样可选的。常用的有以下四种：穿刺法、虹吸法、加压法和切割法。
After centrifuging done by density gradient centrifugation, and zone sample can be collected in different methods, puncturing, siphonage, pressuring and cutting.
