这项工作得到了国家卫生研究院内脏研究司、国家心脏、肺和血液研究所的支持。S.H.得到日本公私合作学生出国留学计划的支持，H.N.和K.Y.获得Valor和V药物海外培训奖学金。

1. SDS-PAGE 并传输到 PVDF 膜
<ol><li>执行 SDS-PAGE，根据相对大小分离蛋白质。 注意:任何商业或自制凝胶系统都没问题。请遵守制造商的协议。</li>
	<li>将分离的蛋白质从凝胶转移到PVDF膜上。 注意:常见的转移方法（半干或湿转移）是合适的。请遵守制造商的协议。</li>
</ol>2. 阻塞PVDF膜
<ol><li>在室温下搅拌时，将膜浸泡在适当的阻塞缓冲区中1小时。 注:根据主要抗体和检测系统，应选择适当的阻塞缓冲区。例如，最典型的阻滞剂是 BSA、脱脂干牛奶、箱蛋白和商用合成聚合物。PBS 和/或 TBS 与 0.1% Tween20 是最常用的缓冲区。此阻塞步骤可在 4 °C 下过夜完成。</li>
</ol>3. 原发性抗体孵化
<ol><li>用蒸馏水准备10%的免疫反应增强剂-1溶液（IRE-1）。漩涡很好。</li>
	<li>用 10% IRE-1 准备稀释的原发抗体。轻轻地和彻底地混合。</li>
	<li>如果使用较大的膜（4 厘米 x 8 厘米 - 8 厘米 x 8 厘米），将 8 mL 的抗体溶液添加到 50 mL 圆锥形离心管中。如果使用较小的膜（2 厘米 x 8 厘米 - 4 厘米 x 8 厘米），将 3 mL 的抗体溶液添加到 14 mL 圆底聚丙烯管（材料表）中。</li>
	<li>用钳子拾取PVDF膜，并短暂地排出阻塞溶液。用戴手套的手指将PVDF膜插入此管中，并确保整个膜粘附在管壁上。当PVDF膜插入管子时，面对最初与凝胶内侧接触的膜的"蛋白质侧"。紧紧地关上帽子。</li>
	<li>将 50 mL 管插入混合烤箱的玻璃瓶中。 注:当 14 mL 管用于此孵化时，将 14 mL 管插入 50 mL 管中，使用一对塑料环架将内管保持在 50 mL 管的中心。</li>
	<li>打开混合烤箱。</li>
	<li>用 6 rpm 旋转孵化膜至少 5 分钟。 注意:确保膜始终粘附在墙壁上，并且（内部）管水平覆盖膜，均匀地覆盖抗体溶液。在实际实验之前校准抗体的稀释和潜伏时间。</li>
</ol>4. 膜洗涤
<ol><li>停止旋转。</li>
	<li>小心地用钳子从管子中取出PVDF膜，并将膜放入一个装有50 mL PBS-T的容器中。</li>
	<li>用 PBS-T 短暂地冲洗膜。</li>
	<li>用蒸馏水冲洗容器中的膜，直到没有气泡出现。这是为了去除大部分抗体。</li>
	<li>将PVDF膜从容器转移到含有250 mL PBS-T的沙拉微调器。</li>
	<li>将过滤器篮放入微调器中。确保盖子安全放置。</li>
	<li>激活微调器并运行大约 20-30 s。</li>
	<li>丢弃溶液，用蒸馏水短暂冲洗微调器内部。</li>
	<li>再次将 250 mL 的 PBS-T 添加到微调器中。</li>
	<li>重复步骤 4.6 和 4.7。</li>
</ol>5. 与二次抗体一起孵育
<ol><li>用蒸馏水准备10%的免疫反应增强剂-2溶液（IRE-2）。漩涡很好。</li>
	<li>用 10% IRE-2 准备稀释的次要抗体。轻轻地和彻底地混合。</li>
	<li>选择第 3.3 步中注述的抗体溶液和管的体积。</li>
	<li>用钳子拾取PVDF膜，并短暂地排干溶液。将 PVDF 膜插入第 3.4 步所述的管子中。</li>
	<li>将 50 mL 管插入混合烤箱的玻璃瓶中。</li>
	<li>打开混合烤箱。</li>
	<li>用 6 rpm 旋转孵化膜至少 5 分钟。确保膜始终粘附在墙壁上，并且（内部）管水平，以便用抗体溶液均匀地覆盖膜。 注:在实际实验之前校准孵化时间。当次要抗体被荧光结合时，在黑暗中进行孵化。</li>
</ol>6. 膜洗涤
<ol><li>按照步骤 4.1 到 4.10。</li>
</ol>7. 图像采集
<ol><li>化学发光检测<ol>
<li>将一块半移植柔性薄膜（10厘米×15厘米）放在平坦的表面上。</li>
		<li>在 5 mL 管中混合化疗基板的 2 个组件。</li>
		<li>立即将混合基板的1.5 mL转移到半移植柔性薄膜上，并将PVDF膜放在它身上。然后，将基板溶液的其余部分转移到膜上。</li>
		<li>在半透明柔性薄膜上用混合基板孵化PVDF膜1分钟。</li>
		<li>用钳子拾取PVDF膜，并短暂地排出基板溶液。</li>
		<li>将膜夹在一对透明胶片之间。</li>
		<li>在化学发光模式下获取图像。</li>
	</ol>
</li>
	<li>荧光检测<ol>
<li>用钳子拾取PVDF膜，并短暂地排干溶液。</li>
		<li>将膜夹在一对透明胶片之间。</li>
		<li>在荧光模式下获取图像。 注:步骤 7.1 和 7.2 应在成像机附近执行，以确保最大灵敏度。</li>
		<li>当背景信号高时，在装有 80-100 mL PBS-T 的容器中执行洗涤步骤:10 分钟冲洗 3 次用于原发抗体，5 分钟冲洗 6 次用于次要抗体。 注:用10%IRE溶液稀释的原辅抗体可使用8-10次，而不会失去灵敏度6。解决方案应保持在4°C长达1个月。</li>
	</ol>
</li>
</ol>

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作者已宣布没有与本文内容直接相关的相互竞争的利益。

西方污点是一种广泛使用的分析技术，用于检测40年前7、8年前开发的特定蛋白质。此后，该技术不断发展，随后的创新提高了技术2、9、10、11、12、13的灵敏度、速度和定量。此处介绍的增强型超高速西?...

西方的污点（也称为免疫虫）是一种强大而基本的技术，跨越广泛的科学和临床学科。该技术用于检查蛋白质1的存在、相对丰度、相对分子质量和转化后修饰。结合数字图像分析，该方法可以可靠地分析蛋白质的丰度和蛋白质的修饰2。虽然西方的污点是例行公事，但它是一种耗时和劳动密集型的方法。需要用膜长期培养抗体。在这里，我们描述了对孵化方法的修改，该方法克服了这一限制，而不会牺牲灵敏度。
在膜的孵化过程中，抗体漂浮在溶液中，而抗原则固定在膜上。由于其亲和力高，抗体与抗原结合的速度比抗体从散装溶液扩散到膜的速度要快。这会产生低浓度的"消耗层"（图 1）。较远的抗体可能需要数小时才能通过被动扩散到达膜，而被动扩散是导致该技术长期潜伏的主要因素。此效果称为大众运输限制 （MTL）3。有人提出，重复排空和补充含抗体溶液可能会破坏耗竭层，克服MTL4。在这里，我们设计了一种独特的技术，实现这种循环排水和补充 （CDR） 概念，以减少 MTL 在传统的西方印迹协议中的影响，并显著缩短所需的潜伏期。
为了在短的潜伏时间内保持检测灵敏度，我们采用了提高免疫力增强技术，加速抗原抗体反应，从而提高了信号噪声比5。许多市售的免疫增强剂 （IRE） 由 2 个组件组成（解决方案 1 和 2，见 材料表）。IRE的专有成分或作用机制尚未披露，但我们先前发现，IRE在固体相绑定检测中减少了抗原和抗体之间的分离常数，表明亲和力的增强至少部分地对IRE6的增强作用负有责任。CDR 与 IRE 的结合产生了一种超高速的西方印迹处理方案，可在不牺牲灵敏度的情况下缩短整个过程时间。

<table><tbody><tr><td>14 mL Round Bottom High Clarity PP Test Tube, Graduated, with Snap Cap</td><td>Falcon</td><td>352059</td><td></td></tr><tr><td>Apollo Transparency Film for Laser Printers</td><td>N/A</td><td>N/A</td><td>Any kinds of Laser Printer Transparency Film are fine.</td></tr><tr><td>Azure Imaging System 600</td><td>Azure Biosystems</td><td>Azure 600</td><td>Any kind of Image Acquiring Sytem is fine for chemiluminescent and/or fluorescent detection.</td></tr><tr><td>Can Get Signal Immunoreaction Enhancer Solution</td><td>TOYOBO</td><td>NKB-101</td><td></td></tr><tr><td>CARNATION Instant Nonfat Dry Milk</td><td>Carnation</td><td>N/A</td><td></td></tr><tr><td>ECL anti-mouse IgG, Horseradish peroxidase linked F(ab&amp;rsquo;)2 fragment from sheep</td><td>GE Healthcare</td><td>NA9310V</td><td></td></tr><tr><td>ECL anti-rabbit IgG, Horseradish peroxidase linked F(ab&amp;rsquo;)2 fragment from donkey</td><td>GE Healthcare</td><td>NA9340V</td><td></td></tr><tr><td>HYBAID Micro-4</td><td>N/A</td><td>N/A</td><td>Any hybridization oven is fine as long as the tubes are rotated evenly at a horizontal position.</td></tr><tr><td>Immobilon-P PVDF Membrane, 0.45 &amp;micro;m pore size</td><td>Millipore Sigma</td><td>IPVH304F0</td><td></td></tr><tr><td>IRDye 680RD Goat anti-Mouse IgG Secondary Antibody</td><td>LICOR</td><td>926-68070</td><td></td></tr><tr><td>IRDye 800CW Goat anti-Rabbit IgG Secondary Antibody</td><td>LICOR</td><td>926-32211</td><td></td></tr><tr><td>KPL LumiGLO Reserve Chemiluminescent Substrate</td><td>seracare</td><td>5430-0049</td><td></td></tr><tr><td>Mouse anti-&amp;szlig; actin antibody</td><td>Millipore Sigma</td><td>A5316</td><td></td></tr><tr><td>Odyssey Blocking Buffer (PBS)</td><td>LICOR</td><td>927-40100</td><td>Blocking Buffer for fluorescent detection</td></tr><tr><td>OXO Salad Spinner</td><td>OXO</td><td>32480V2B</td><td>Any salad spinner is fine as long as the PVDF membranes are rinsed vigorously without tear.</td></tr><tr><td>Parafilm Sealing Film</td><td>Bemis</td><td>Parafilm M PM996</td><td>semi-transparent flexible film</td></tr><tr><td>Polyethylene Flat-Top Screw Caps for 50 mL Conical Bottom Centrifuge Tubes</td><td>Falcon</td><td>352070</td><td></td></tr><tr><td>Rings to hold 14 ml tube in the center of 50 ml tube</td><td>N/A</td><td>N/A</td><td>Prepared in a machine shop</td></tr><tr><td>Rabbit anti-6X His tag antibody</td><td>Abcam</td><td>ab9108</td><td></td></tr><tr><td>Tween20</td><td>Millipore Sigma</td><td>P2287</td><td></td></tr></tbody></table>

ultra-high-speed western blot using immunoreaction enhancing technology

西方的污点（也称为免疫虫）是生物医学研究的规范方法。它通常用于确定特定蛋白质的相对大小和丰度以及转化后蛋白质的修饰。这种技术具有丰富的历史，由于其简单性，仍然被广泛使用。然而，西方的印迹程序著名的需要几个小时，甚至几天，完成，一个关键的瓶颈是长期的潜伏时间，限制其吞吐量。由于抗体从散装溶液缓慢扩散到膜上的固定抗原，因此需要这些培养步骤:膜附近的抗体浓度远远低于散装浓度。在这里，我们提出了一项创新，通过循环排空和补充抗体溶液 （CDR） 来改善抗原结合，从而显著缩短这些潜伏间隔。我们还利用了增强免疫力的技术来保持检测的灵敏度。CDR方法与商业免疫增强剂相结合，提高了输出信号，大大缩短了抗体潜伏时间。由此产生的超高速西部污点可以在20分钟内完成，而不会失去任何灵敏度。该方法可同时使用化学发光和荧光检测方法应用于西方污点。这种简单的协议使研究人员能够更好地探索许多样本中蛋白质表达的分析。

这个例子说明了CDR方法以及免疫增强技术对西方污点的有效性。静态孵化是在半透明的柔性薄膜上进行的，其中PVDF膜与抗体溶液一起孵育，而CDR孵化则通过含有膜和抗体溶液（电影）的旋转管在混合烤箱中。 图2 显示的抗原和抗体数量分别为西斑化学发光检测所必需的。在静态和 CDR 孵化中，使用 IRE 溶液提高了灵敏度:IRE 将检测 é actin 所需的最低细胞溶解物 （抗原） 数量...

Watch this Scientific Journal Video about Ultra-High-Speed Western Blot using Immunoreaction Enhancing Technology at JoVE.com

Ultra-High-Speed Western Blot using Immunoreaction Enhancing Technology

通过循环排泄和补充 （CDR） 技术与免疫增异剂一起改进抗原抗体结合的动能，开发出一种超高速西方印迹技术。

使用免疫增强技术的超高速西布洛特

A western blot (also known as an immunoblot) is a canonical method for biomedical research. It is commonly used to determine the relative size and ...

ultra-high-speed-western-blot-using-immunoreaction-enhancing

Research

JoVE Journal

Biochemistry

5.9K 次观看.  National Institutes of Health. 通过循环排泄和补充 （CDR） 技术与免疫增异剂一起改进抗原抗体结合的动能，开发出一种超高速西方印迹技术。

视频: Ultra-High-Speed Western Blot using Immunoreaction Enhancing Technology

An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. Radioactivity has been the predominant method of DNA labeling in EMSAs. However, recent advances in fluorescent dyes and scanning methods have prompted the use of fluorescent tagging of DNA as an alternative to radioactivity for the advantages of easy handling, saving time, reducing cost, and improving safety. We have recently used fluorescent EMSA (fEMSA) to successfully address an important biological question. Our fEMSA analysis provides mechanistic insight into the effect of a missense mutation, G73E, in the highly conserved HMG transcription factor SOX-2 on olfactory neuron type diversification. We found that mutant SOX-2G73E protein alters specific DNA binding activity, thereby causing olfactory neuron identity transformation. Here, we present an optimized and cost-effective step-by-step protocol for fEMSA using infrared fluorescent dye-labeled oligonucleotides containing the LIM-4/SOX-2 adjacent target sites and purified SOX-2 proteins (WT and mutant SOX-2G73E proteins) as a biological example.

We describe here an optimized protocol of fluorescent Electrophoretic Mobility Shift Assays (fEMSA) using purified SOX-2 proteins together with infrared fluorescent dye-labeled DNA probes as a case study to tackle an important biological question.

一种优化的协议电泳迁移分析使用红外荧光染料标记的寡核苷酸

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. ...

科研

生物化学

Western Blotting Using the Invitrogen NuPage Novex Bis Tris MiniGels

Western Blotting (or immunoblotting) is a standard laboratory procedure allowing investigators to verify the expression of a protein, determine the relative amount of the protein present in different samples, and analyze the results of co-immunoprecipitation experiments. In this method, a target protein is detected with a specific primary antibody in a given sample of tissue homogenate or extract. Protein separation according to molecular weight is achieved using denaturing SDS-PAGE. After transfer to a membrane, the target protein is probed with a specific primary antibody and detected by chemiluminescence.
Since its first description, the western-blotting technique has undergone several improvements, including pre-cast gels and user-friendly equipment. In our laboratory, we have chosen to use the commercially available NuPAGE electrophoresis system from Invitrogen. It is an innovative neutral pH, discontinuous SDS-PAGE, pre-cast mini-gel system. This system presents several advantages over the traditional Laemmli technique including: i) a longer shelf life of the pre-cast gels ranging from 8 months to 1 year; ii) a broad separation range of molecular weights from 1 to 400 kDa depending of the type of gel used; and iii) greater versatility (range of acrylamide percentage, the type of gel, and the ionic composition of the running buffer).
The procedure described in this video article utilizes the Bis-Tris discontinuous buffer system with 4-12% Bis-Tris gradient gels and MES running buffer, as an illustration of how to perform a western-blot using the Invitrogen NuPAGE electrophoresis system. In our laboratory, we have obtained good and reproducible results for various biochemical applications using this western-blotting method.

This technical article describes a standard western-blotting procedure using the commercially available NuPAGE electrophoresis Mini-Gel system from Invitrogen.

免疫印迹使用Invitrogen公司NuPage NOVEX双三MiniGels

Western Blotting (or immunoblotting) is a standard laboratory procedure allowing investigators to verify the expression of a protein, determine the ...

生物学

Highly Sensitive and Quantitative Detection of Proteins and Their Isoforms by Capillary Isoelectric Focusing Method

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides an alternative strategy, capillary isoelectric focusing (cIEF), with many advantages compared to conventional immunoblotting. This is an antibody-based, automated, rapid, and quantitative method in which a complete western blotting procedure takes place inside an ultrathin capillary. This technique does not require a gel to transfer to a membrane, stripping of blots, or x-ray films, which are typically required for conventional immunoblotting. Here, proteins are separated according to their charge (isoelectric point; pI), using less than a microliter (400 nL) of total protein lysate. After electrophoresis, proteins are immobilized onto the capillary walls by ultraviolet light treatment, followed by primary and secondary (horseradish peroxidase (HRP) conjugated) antibody incubation, whose binding is detected through enhanced chemiluminescence (ECL), generating a light signal that can be captured and recorded by a charge-coupled device (CCD) camera. The digital image can be analyzed and quantified (peak area) using software. This high throughput procedure can handle 96 samples at a time; is highly sensitive, with protein detection in the picogram range; and produces highly reproducible results because of automation. All of these aspects are extremely valuable when the quantity of samples (e.g., tissue samples and biopsies) is a limiting factor. The technique has wider applications as well, including screening of drugs or antibodies, biomarker discovery, and diagnostic purposes.

Capillary isoelectric focusing is an antibody-based, ultrasensitive, high throughput technique, enabling detailed characterization of proteins and their isoforms from extremely small biological samples. The following describes a protocol for detection and quantification of specific proteins and their isoforms in an automated and robotized manner.

毛细管电聚焦法对蛋白质及其亚型的高灵敏度和定量检测

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides ...

Immunoblot Analysis

Immunoblotting (western blotting) is a rapid and sensitive assay for the detection and characterization of proteins that works by exploiting the specificity inherent in antigen-antibody recognition. It involves the solubilization and electrophoretic separation of proteins, glycoproteins, or lipopolysaccharides by gel electrophoresis, followed by quantitative transfer and irreversible binding to nitrocellulose, PVDF, or nylon. The immunoblotting technique has been useful in identifying specific antigens recognized by polyclonal or monoclonal antibodies and is highly sensitive (1 ng of antigen can be detected). This unit provides protocols for protein separation, blotting proteins onto membranes, immunoprobing, and visualization using chromogenic or chemiluminescent substrates.

Immunoblotting (western blotting) is a rapid and sensitive assay for the detection and characterization of proteins that works by exploiting the specificity inherent in antigen-antibody recognition. This video provides protocols for protein separation, blotting proteins onto membranes, immunoprobing, and visualization using chromogenic or chemiluminescent substrates.

免疫印迹分析

Immunoblotting (western blotting) is a rapid and sensitive assay for the detection and characterization of proteins that works by exploiting the ...

Western Blotting: Sample Preparation to Detection

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native or denatured proteins by the length of the polypeptide (denaturing conditions) or by the 3-D structure of the protein (native/ non-denaturing conditions). The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are probed (detected) using antibodies specific to the target protein.

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract.

免疫印迹检测样品制备

Western blotting is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract. It uses gel ...

The Fastest Western in Town: A Contemporary Twist on the Classic Western Blot Analysis

The Western blot techniques that were originally established in the late 1970s are still actively utilized today. However, this traditional method of Western blotting has several drawbacks that include low quality resolution, spurious bands, decreased sensitivity, and poor protein integrity. Recent advances have drastically improved numerous aspects of the standard Western blot protocol to produce higher qualitative and quantitative data. The Bis-Tris gel system, an alternative to the conventional Laemmli system, generates better protein separation and resolution, maintains protein integrity, and reduces electrophoresis to a 35 min run time. Moreover, the iBlot dry blotting system, dramatically improves the efficacy and speed of protein transfer to the membrane in 7 min, which is in contrast to the traditional protein transfer methods that are often more inefficient with lengthy transfer times. In combination with these highly innovative modifications, protein detection using infrared fluorescent imaging results in higher-quality, more accurate and consistent data compared to the standard Western blotting technique of chemiluminescence. This technology can simultaneously detect two different antigens on the same membrane by utilizing two-color near-infrared dyes that are visualized in different fluorescent channels. Furthermore, the linearity and broad dynamic range of fluorescent imaging allows for the precise quantification of both strong and weak protein bands. Thus, this protocol describes the key improvements to the classic Western blotting method, in which these advancements significantly increase the quality of data while greatly reducing the performance time of this experiment.

This protocol explores the latest advancements in performing Western blot analyses.&#160;These novel modifications employ a Bis-Tris gel system with a 35&#160;min electrophoresis run time, a 7&#160;min dry blotting transfer system, and infrared fluorescent protein detection and imaging that generates higher resolution, quality, sensitivity, and improved accuracy of Western data.

最快在西镇：对经典蛋白质印迹分析现代风味

The Western blot techniques that were originally established in the late 1970s are still actively utilized today. However, this traditional method of ...

A Guide to Modern Quantitative Fluorescent Western Blotting with Troubleshooting Strategies

The late 1970s saw the first publicly reported use of the western blot, a technique for assessing the presence and relative abundance of specific proteins within complex biological samples. Since then, western blotting methodology has become a common component of the molecular biologists experimental repertoire. A cursory search of PubMed using the term &#8220;western blot&#8221; suggests that in excess of two hundred and twenty thousand published manuscripts have made use of this technique by the year 2014. Importantly, the last ten years have seen technical imaging advances coupled with the development of sensitive fluorescent labels which have improved sensitivity and yielded even greater ranges of linear detection. The result is a now truly Quantifiable Fluorescence based Western Blot (QFWB) that allows biologists to carry out comparative expression analysis with greater sensitivity and accuracy than ever before. Many &#8220;optimized&#8221; western blotting methodologies exist and are utilized in different laboratories. These often prove difficult to implement due to the requirement of subtle but undocumented procedural amendments. This protocol provides a comprehensive description of an established and robust QFWB method, complete with troubleshooting strategies.

The advancement of western blotting using fluorescence has allowed detection of subtle changes in protein expression enabling quantitative analyses. Here we describe a robust methodology for detection of a range of proteins across a variety of species and tissue types. A strategy to overcome common technical problems is also provided.

指南现代荧光定量免疫印迹与故障排除策略

The late 1970s saw the first publicly reported use of the western blot, a technique for assessing the presence and relative abundance of specific proteins ...

Immunoprecipitation-Based Techniques: Purification of Endogenous Proteins Using Agarose Beads

Source: Susannah C. Shissler1, Tonya J. Webb1 
1 Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201
Immunoprecipitation (IP, also known as a &#39;pull-down&#39; assay) is a widely used technique that has applications in a variety of fields. First conceived in 1984, it was refined in 1988 (1, 2). The fundamental goal of IP is purification and isolation of a specific protein using an antibody against that protein. The word &#34;immuno&#34; refers to the use of an antibody while the word &#34;precipitation&#34; refers to pulling down a specific substance from a solution. The target protein might be endogenous or recombinant. Most recombinant proteins have an epitope tag (i.e. myc or flag) attached to them to simplify subsequent purification. Typically, it is easier to optimize recombinant protein IP because the antibodies against recombinant epitope tags are very strong and effective. Antibodies against endogenous proteins have extremely variable efficacy - making it much more difficult to optimize these IPs. A necessary step after immunoprecipitation is verification of purification. The isolated protein is resolved using SDS-PAGE and subsequently probed for purity by western blots (Figure 1). An important control is the use of a different antibody during the Western blot to verify pull down of the correct protein. The combination of IP with subsequent techniques is a powerful analysis tool. The goal after purification may be characterization of the protein itself by NMR, mass spectrometry, and in vitro assays, or analysis of the protein&#39;s interacting partners (i.e. protein, DNA, RNA) (3, 4, 5).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/10502/10502fig1.jpg" /> 
Figure 1: Overview of Immunoprecipitation Procedure. Immunoprecipitation is the isolation of a specific protein using an antibody. After production of lysate from cells, there are two major steps- pre-clearing and pull down. During pre-clearing step, the cell-lysates are pre-cleared of proteins that bind to antibodies non-specifically using an isotype control antibody. In pull down step, the target protein is pulled down using a protein-specific antibody. The isolated protein is then analyzed by Western blot. Isotype antibodies and protein specific antibodies have the same constant domain, but different antigen binding domains. A key component of this protocol is Protein A/G agarose beads that bind the constant domain of antibodies- allowing immunoprecipitation of the target protein. <a href="https://www.jove.com/files/ftp_upload/10502/10502fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Antibodies are the key component of an immunoprecipitation that differentiate it from other forms of protein purification (i.e. nickel affinity column purification). Antibodies are molecules made by B cells that can recognize specific protein epitopes. Antibodies have two domains: constant (Fc) and antigen binding (Fab) (Figure 1). The constant domain identifies the type of antibody and dictates function in vivo. Usually, the constant domains of antibodies used for IP are mouse, rat, or rabbit IgG. The antigen binding portion of the antibody recognizes a specific epitope of a specific protein. Antibodies can recognize epitopes on folded proteins that may not exist when the protein is denatured and vice versa. Therefore, the availability of the epitope depends on protein folding - identifying an important factor to consider when choosing antibodies and conditions for IP.
Both prokaryotic and eukaryotic systems have antibody-binding proteins. In eukaryotic systems, the purpose is immune protection from bacteria while in prokaryotic systems, the purpose is protection from the immune system. Antibody-binding proteins affect IP methodology in two ways. First, there is a necessary pre-clearing step (Figure 1) to rid the lysate of proteins that bind antibodies - thereby reducing non-specific binding in the final product. This step uses an isotype antibody that has the same constant domain as but a different antibody binding domain than your protein-specific antibody. Bacterial antibody-binding proteins are the second key component of this method. After the protein-specific antibody binds the target protein, the antibody: protein complex must be pulled down (Figure 1). Proteins A, G, and L are bacterial proteins that bind the constant domain of antibodies. While bacteria use this to subvert the immune system, researchers have co-opted this system for easy antibody purification, and it is used during both the pre-clearing and pull-down steps. These proteins have different binding affinities for different species and different constant domain subtypes - another factor to consider when choosing conditions for IP. Many companies sell Protein A/G labeled agarose beads (Figure 1), pre-made spin columns, or resins to make columns. In general, beads and spin columns are used for smaller sample sizes while resins are used for bulk purification.
In this lab exercise, we demonstrate how to purify the endogenous protein c-myc, from primary murine thymocytes, using Protein A/G Plus agarose beads based basic immunoprecipitation technique. The protocol starts from cell lysate preparation and ends with the with verification of successful protein pull down using Western blot analysis.

Immunoprecipitation Techniques: Purification of Proteins

基于免疫沉淀的技术:使用阿加玫瑰珠纯化内源性蛋白质

Source: Susannah C. Shissler1, Tonya J. Webb1
1 Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201
Immunoprecipitation ...

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高级生物学

免疫学

The Western Blot

Western Blotting is used to identify the presence of specific proteins in electrophoretically separated samples. Following separation by a technique known as sodium dodecyl sulfate polyacrylamide gel electrophoresis, or SDS-PAGE, western transfer is used to move proteins from a polyacrylamide gel onto a piece of membrane which traps the proteins in their respective locations. Next, the membranes are probed with antibodies in a process called immunboblotting. Immunoblotting uses antibody-protein and antibody-antibody binding through specific recognition sites, providing the high specificity required for identifying a single protein. The detection of antibodies takes place using reporter systems which includes the use of enzymes. Enzymes can be attached to the end of an antibody and react with substrates to produce changes in color or light. These signals can then be imaged and quantified using a process called densitometry.
This video-article presents an overview of the western blot technique by describing western transfer, the use of antibody detection, and image analysis. The steps involved with western transfer such as the assembly of the transfer sandwich and transfer conditions are discussed in detail as well as the theory behind antibody binding and detection of those antibodies. The broad applications of this technique are described through several examples including the detection of protein-protein interactions and identification of individual proteins within protein complexes.

Western Blotting: Western Transfer, Antibody Detection, and Image Analysis

蛋白免疫印迹杂交

Western Blotting is used to identify the presence of specific proteins in electrophoretically separated samples.  Following separation by a technique ...

基础生物学

细胞分子生物学中的基本方法

Chemiluminescent Western Blot Assay for Protein Processing

Source: Hillert-Richter, L. K. et al., <a href="https://app.jove.com/v/62842">Measuring Composition of CD95 Death-Inducing Signaling Complex and Processing of Procaspase-8 in this Complex.</a> J. Vis. Exp. (2021).
This video describes the chemiluminescence-based western blotting of immunoprecipitated lysates. The technique helps determine protein processing and activation. The chemiluminescent signal detected is proportional to the level of protein processing during its activation.

用于蛋白质加工的化学发光 Western Blot 检测

Source: Hillert-Richter, L. K. et al., Measuring Composition of CD95 Death-Inducing Signaling Complex and Processing of Procaspase-8 in this Complex. J. ...