談談實驗室離心機高速離心的工作原理和特點

通常情況下，制備型超高速（preparative super-speed）實驗室離心機高速離心的原理有差速離心（differential centrifugation）和密度梯度離心（density gradient centrifugation）兩種。其中，差速離心法是相對更為常用的方法。

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.

實驗室高速離心機差速離心是采用逐漸增大離心力的方法來達到使樣品溶液中的各種成分沉降分離的目的。具體操作步驟是：首先在離心管中盛滿同質均一的樣品溶液，設定一定速度一定時間離心后溶液會分成上清液和沉淀物兩部分；去掉*次離心的沉淀物，增大離心力繼續離心上清液以沉積所需的離子。值得注意的是，兩次離心的時間都必須選擇得當才能達到所需的分離純度。

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.

相對而言，差速離心的操作更為簡單，而密度梯度離心的分離純度更高。離心機密度梯度離心法能達到很好的分辨率，它能使溶液中所有的組份分離。密度梯度分離通常有速率區帶法（rate zonal）和等密度離心法（isopycnic）兩種。前者的依據是溶液中不同粒子的尺寸大小和沉積速度不一，而后者的依據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離心時，梯度形狀至關重要。線性梯度（linear gradient）是zui常用的。 它可以用來分離蛋白質、酶和植物病毒等，等速型梯度（constant speed gradient）適用于分離脂蛋白；分離整細胞和亞細胞采用的則是階梯型梯度（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離心后，區帶樣品的回收方法也是多樣可選的。常用的有以下四種：穿刺法、虹吸法、加壓法和切割法。

After centrifuging done by density gradient centrifugation, and zone sample can be collected in different methods, puncturing, siphonage, pressuring and cutting.