PAGE膠濃度交聯(lián)度與分子大小.docx

產(chǎn)品信息產(chǎn)品名稱產(chǎn)品編號規(guī)格價格（元）40% Acr-Bis (19:1)20303ES76500ml220.0040% Acr-Bis (29:1)20304ES76500ml220.0040% Acr-Bis (37.5:1)20305ES76500ml220.00產(chǎn)品描述Acr-Bis常用于配制丙烯酰胺凝膠(PAGE膠)，包括SDS-PAGE膠等，可以用于蛋白或核酸的分離。聚丙烯酰胺凝膠是由丙烯酰胺（acrylamide，簡稱Acr）和交聯(lián)劑甲叉雙丙烯酰胺（N，N-methylene bisacrylamide，簡稱Bis ）在催化劑的作用下，通過自由基引發(fā)聚合反應(yīng)，形成不帶電荷、且具有分子篩性質(zhì)的網(wǎng)狀結(jié)構(gòu)。其孔徑大小由聚合鏈的長度和交聯(lián)度（交叉連接的程度）所決定。聚合鏈的長度與丙烯酰胺的濃度有關(guān)，交聯(lián)度由Acr 與Bis的相對比例決定，調(diào)節(jié)單體丙烯酰胺與交聯(lián)劑（Bis）的濃度比例，可形成具有不同交聯(lián)度的網(wǎng)狀聚合物。其中Bis的濃度愈低，凝膠的孔徑愈大，適用于分離較大的分子；Bis的濃度愈高，網(wǎng)孔越小，分辨率越高，越有利于分離較小的分子。40% Acr-Bis(19:1)即為含40% acrylamide-bisacrylamide的水溶液，其中acrylamide和bisacrylamide的比例為19:1。40% Acr-Bis(29:1)即為含40% acrylamide-bisacrylamide的水溶液，其中acrylamide和bisacrylamide的比例為29:1。40% Acr-Bis(37.5:1)即為含40% acrylamide-bisacrylamide的水溶液，其中acrylamide和bisacrylamide的比例為37.5:1。運輸與保存方法冰袋（wet ice）運輸。4避光保存。注意事項1) Acr-Bis具有一定神經(jīng)毒性，使用時請注意適當防護。2) 為了您的安全和健康，請穿實驗服并戴一次性手套操作。The Polyacrylamide MatrixThe polymerization of a polyacrylamide matrix with methylenebisacrylamide cross-linking.Polyacrylamide gels are formed by the polymerization of acrylamide in aqueous solution in the presence of small amounts of a bifunctional crosslinker. The crosslinker is usually methylene:bisacrylamide (bis, or MBA). The copolymerization of acrylamide with methylenebisacrylamide produces a mesh-like network in three dimensions, consisting of acrylamide chains with interconnections formed from the methylenebisacrylamide. A variety of crosslinkers are available in addition to bis. These include piperazine diacrylate (PDA), N,N-bisacrylylcystamine (BAC), and N,N-diallyltartardiamide (DATD). PDA is used to reduce silver stain backgrounds in SDS-PAGE gels. BAC and DATD are both disruptable cross-linkers which enable gels to be solubilized.BAC,DATD, and Piperazine diacrylate are sometimes used as the cross-linkers in polyacrylamide gels to vary the physical or chemical properties of the gel.For discussions of the composition of polyacrylamide gels, a standard nomenclature has been widely adopted. In this nomenclature, T represents the total percentage concentration (w/v) of monomer (acrylamide plus crosslinker) in the gel. The term C refers to the percentage of the total monomer represented by the crosslinker. For example,an 8%, 19:1 (acrylamide/bisacrylamide) gelwould have a T value of 8% and a C value of 5%.Upon the introduction of catalyst, the polymerization of acrylamide and methylene bisacrylamide proceeds via a free-radical mechanism. The most common system of catalytic initiation involves the production of free oxygen radicals byammonium persulfatein the presence of the tertiary aliphatic amineN,N,N,N-tetramethylethylenediamine (TEMED). Another catalytic system involves the generation of free radicals via a photochemical process using a very small amount ofriboflavinin the presence of TEMED. In both catalytic systems, the presence of excess oxygen will inhibit the polymerization elongation process and can lead to shorter average chain length. For this reason, if the casting solution has been excessively agitated, deaeration under vacuum with a magnetic stirrer is suggested prior to addition of initiators.For certain applications, polyacrylamide has definite advantages compared to agarose. In an agarose gel, the pore size is large, so molecular sieving, i.e. separation by size, will not occur for smaller DNA fragments and most proteins. Additionally, by altering the total concentration of monomer in the gel and the ratio of acrylamide to bis, the pore size with a polyacrylamide gel can be altered in a reproducible manner. The small and reproducible pore size in polyacrylamide gels results in superior resolution: a 0.1% difference in size (1 base difference in a 1kb molecule) can be detected. Also, because acrylamide and bis are synthetic chemicals, there are virtually no batch to batch differences (It should be mentioned that batch to batch differences with agarose are overcome with the highest quality agaroses, such as National Diagnostics AquaPor agaroses).Control of the pore size of a polyacrylamide gel is accomplished by changing the T and C values. With increasing T, the pore size decreases in a nearly linear relationship. Higher percentage gels (higher T), with smaller pores, are used to separate smaller molecules. The relationship of C to pore size is more complex. Generally, the minimum pore size occurs when C is about 5% (a 19:1 gel). Decreasing C results in a more open pore structure because there are fewer crosslinker molecules. Increasing C beyond 5% also increases the pore size. This appears to be because of nonhomogeneous bundling of strands in the gel.Researchers have settled on C values of 5.0% (19:1 acrylamide/bis) for most forms ofdenaturing DNA and RNA electrophoresisand 3.3% (29:1) for mostnative DNA and RNA gels. ForSDS-PAGE electrophoresis of proteins, the standard C value that has been adopted is 2.6% (37.5:1). The table below gives recommended acrylamide/bis ratios and gel percentages for different molecular size ranges.Polyacrylamide Gel SolutionsRecommended appplications for each for each formulations shown in boldAcrylamide:MBARatioGel %NativeDNA/RNA (bp)DenaturedDNA/RNA (bp)Protein (kp)19:14100-150070-50010