乙醇沉淀法是一种常用的技术集中的盐在水溶液中的核酸（DNA或RNA）准备。 The basic procedure is that salt and ethanol are added to the aqueous solution, which forces the nucleic acid to precipitate out of solution.其基本做法是，加入盐和乙醇水溶液，这迫使核酸沉淀出的解决方案。 The precipitated nucleic acid can then be parated from the rest of the solution by centrifugation.然后可以休息的解决方案，通过离心分离沉淀核酸。 The pellet is washed in cold 70% ethanol then after a further centrifugation step the ethanol is removed, and the nucleic acid pellet is allowed to dry before being resuspended in clean aqueous buffer.在寒冷的70％乙醇洗涤沉淀，然后再经过离心步骤乙醇被删除，并允许核酸颗粒干燥，然后在干净的缓冲溶液中悬浮。 So how does this work?那么如何工作的呢？
A bit about solubility… 关于溶解度的位...
First we need to know why nucleic acids are soluble in water.首先，我们需要知道为什么核酸是易溶于水。 Water is a polar molecule – it has a partial negative charge near the oxygen atom due the unshared pairs of electrons, and partial positive charges near the hydrogen atoms (e the diagram on the right).水是极性分子 - 它有一个部分负电荷的氧原子附近，由于共用电子对，部分正电荷的氢原子（见右图）附近。
法语歌曲Becau of the charges, polar molecules, like DNA or RNA, can interact electrostatically with the water molecules, allowing them to easily dissolve in water.极性分子，如DNA或RNA，因为这些费用，可以与水分子的静电相互作用，使他们能够很容
易溶解于水。 嘻哈帮街舞Polar molecules can therefore be described as hydrophilic and non-polar molecules, which can't easily interact with water molecules, are hydrophobic.极性分子，因此可以被描述为亲水性和非极性分子，不能轻易与水分子相互作用，疏水。 Nucleic acids are hydrophilic due to the negatively charged phosphate (PO3-) groups along the sugar phosphate backbone.核酸是亲水性由于带负电荷的磷（PO3-居里夫人笔记辐射）组沿糖磷酸骨架。
The role of the salt… 盐的作用...
Ok, so back to the protocol.好吧，这样的协议。 The role of the salt in the protocol is to neutralize the charges on the sugar phosphate backbone.盐在协议中的作用是消除糖磷酸骨架上的收费。 A commonly ud salt is sodium acetate.一种常用的盐是醋酸钠。 In solution, sodium acetate breaks up into Na+ and [CH3COO]-.在溶液中，分解成Na +和[醋酸 - 醋酸钠。 The positively charged sodium ions neutralize the negative charge on the PO3- groups on the nucleic acids, making the molecule far less hydrophilic, and therefore much less soluble in water.带正电的钠离子中和负电荷的核酸PO3组，分子远低于亲水性，因此多不溶于水。mosa
The role of the ethanol… 乙醇的作用...
The electrostatic attraction between the Na+ ions in solution and the PO3- ions are dictated by Coulomb's Law , which is affected by the dielectric constant of the solution.钠离子在溶液中和PO3-离子之间的静电吸引力， 库仑定律 ，这是解决方案的电介质常数的影响决定。 Water has a high dielectric constant, which makes it fairly difficult for the Na+ and PO3- to come together.水具有较高的介电常数，这使得它相当困难Na +和PO3-走到一起。 Ethanol on the other hand has a much lower dielectric constant, making it much easier for Na+ to interact with the PO3-, shield it's charge and make the nucleic acid less hydrophilic, causing it to drop out of solution.另一方面乙醇低得多的介电常数，使得它的Na +更容易互动，PO3-，它的电荷屏蔽，使核酸的亲水性，使其下降了解决方案。
The role of temperature… 温度的作用...山木教育
Incubation of the nucleic acid/salt/ethanol mixture at low temperatures (eg -20 or -80C) is commonly cited in protocols as necessary in protocols.
vac作为必要的协议，在协议中普遍提及的核酸/盐/乙醇的混合物在低温（如-20或-80C）的孵化。 However, according to Maniatis et al (Molecular Cloning, A Laboratory Manual 2nd Edition… 2nd edition?? – I need to get a newer version!), this is not required, as nucleic acids at concentrations as low as 20ng/mL will precipitate at 0-4C so incubation for 15-30 minutes on ice is sufficient.然而，根据，曼尼阿蒂斯等 （分子克隆实验手册第二版...第二版- ？！我需要得到一个新的版本），这是不是必需的，因为20ng/mL低浓度核酸沉淀在0-4C，所以在冰上潜伏期为15-30分钟就足够了。
广州化妆
The wash step with 70% ethanol… 用70％乙醇洗涤步骤...
This step is to wash any residual salt away from the pelleted DNA.这一步是洗任何剩余的盐颗粒的DNA。
A few tips on nucleic acid precipitation… 核酸沉淀的一些技巧...
▪ Choice of salt 盐的选择
▪ U Sodium acetate (0.3M final conc, pH 5.2) for routine DNA precipitations使用常规的DNA沉淀醋酸钠 （0.3M终浓度，pH值5.2）
▪ U Sodium chloride (0,2M final conc) for DNA samples containing SDS since NaCl keeps SDS soluble in 70% ethanol so it won't precipitate with the DNA.使用DNA含有SDS自氯化钠保持SDS在70英文伤感网名％乙醇中易溶，所以它不会沉淀的DNA样本， 氯化钠 （0,2米决赛浓度）。
▪ U Lithium Chloride (0.8M final conc) for RNA.使用氯化锂 （0.8M终浓度）的RNA。 This is becau 2.5-3 volumes of ethanol should be ud for RNA precipitation and LiCl is more soluble in ethanol than NaAc so will not precipitate, but beware – chloride ions will inhibit protein synthesis and DNA polymera so LiCl is no good for RNA preps for in vitro translation or rever transcription.这是因为2.5-3乙醇卷应该被用于RNA沉淀和LiCl
是比乙酸钠溶于乙醇，所以不会沉淀，但要小心 - 氯离子会抑制蛋白质的合成和DNA聚合酶，使氯化锂的RNA PREPS没有好的在体外翻译或反转录。 In the cas, u NaAc.在这种情况下，使用醋酸钠。
▪ U Ammonium acetate (2M final conc) for the removal of dNTPs, but do not u for preparation of DNA for T4 polynucleotide kina reactions as ammonium ions inhibit the enzyme.用于去除dNTPs浓度的醋酸铵 （pantiho2M终浓度），但不使用T4聚核苷酸激酶反应制备的DNA铵离子抑制酶。
▪ To increa the yield in precipitations of low concentration or small nucleic acid pieces (less than 100 nucleotides) 在低浓度或小核酸件（少于100个核苷酸）的降水以增加产量好学的英文歌
▪ Add MgCl2 to a final concentration of 0.01M氯化镁的终浓度为0.01M
▪ Increa the time of incubation ice before centrifugation to 1 hour.潜伏期冰离心前的时间增加至1小时。
Phenol/Chloroform Extraction酚/氯仿抽提
and Ethanol Precipitation和乙醇沉淀
DESCRIPTION描述
Phenol/Chloroform Extraction酚/氯仿抽提
One of the most commonly ud and uful methods for isolation and concentration of DNA and RNA from aqueous solutions is phenol/chloroform extraction followed by ethanol precipitation.最常用的和有益的，从水溶液中的DNA和RNA的分离和浓度的方法之一是酚/氯仿抽提，乙醇沉淀。 During organic extraction, protein contaminants are denatured and partition either with the organic pha or at the interface between organic and aqueous phas, while nucleic acids remain in the aqueous pha.在有机萃取，蛋白质污染物变性和分区与有机相或有机相和水相之间的界面，而留在水相中的核酸。 Phenol ud in this protocol is buffered to prevent oxidized products in the phenol from damaging the nucleic acids.在这个协议中使用的苯酚缓冲，以防止破坏核酸在苯酚氧化的产品。 Be aware that phenol can cau vere chemical burns on skin and will damage clothing.要知道，酚可引起严重的化学烧伤，皮肤上，会损伤衣物。 Wear gloves, safety glass, and a laboratory coat when working with phenol.与苯酚工作时戴手套，安全眼镜，实验室大衣。 In the method prented here, phenol/chloroform (50%/50%; v/v) is recommended for extraction.建议在这里提出的方法，酚/氯仿（50％/ 50％V / V） 提取 。 In most cas, this mixture provide在大多数情况下，这种混合物提供 good protein denaturation and a tighter interpha between the aqueous and organic phas. 良好的蛋白质变性和水相和有机相之间的更紧密相间。 If there is a problem with excessive foaming during the extraction, isoamyl alcohol can be added to obtain an organic composition of phenol/chloroform (50%/49%)/isoamyl alcohol (I%). 提取过程中过多的泡沫如果有一个问题，异戊醇可以增加获得的酚/氯仿（50％/ 49％）/异戊醇（％）的有机组成。
