Protein Blotting Guide
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Electrophoresis and Blotting Protein Blotting Guide BEGIN Protein Blotting Guide Theory and Products Part 1 Theory and Products 5 Chapter 5 Detection and Imaging 29 Total Protein Detection 31 Transfer Buffer Formulations 58 5 Chapter 1 Overview of Protein Blotting Anionic Dyes 31 Towbin Buffer 58 Towbin Buffer with SDS 58 Transfer 6 Fluorescent Protein Stains 31 Stain-Free Technology 32 Bjerrum Schafer-Nielsen Buffer 58 Detection 6 Colloidal Gold 32 Bjerrum Schafer-Nielsen Buffer with SDS 58 CAPS Buffer 58 General Considerations and Workflow 6 Immunodetection 32 Dunn Carbonate Buffer 58 Immunodetection Workflow 33 0.7% Acetic Acid 58 Chapter 2 Methods and Instrumentation 9 Blocking 33 Protein Blotting Methods 10 Antibody Incubations 33 Detection Buffer Formulations 58 Electrophoretic Transfer 10 Washes 33 General Detection Buffers 58 Tank Blotting 10 Antibody Selection and Dilution 34 Total Protein Staining Buffers and Solutions 59 Semi-Dry Blotting 11 Primary Antibodies 34 Substrate Buffers and Solutions 60 Microfiltration (Dot Blotting) Species-Specific Secondary Antibodies 34 Stripping Buffer 60 Antibody-Specific Ligands 34 Blotting Systems and Power Supplies 12 Detection Methods 35 Tank Blotting Cells 12 Colorimetric Detection 36 Part 3 Troubleshooting 63 Mini Trans-Blot® Cell and Criterion™ Blotter 12 Premixed and Individual Colorimetric Substrates 38 Transfer 64 Trans-Blot® Cell 12 Immun-Blot® Assay Kits 38 Electrophoretic Transfer 64 Trans-Blot® Plus Cell 13 Immun-Blot Amplified AP Kit 38 Microfiltration 65 Semi-Dry Blotting Cells 13 Opti-4CN™ and Amplified Opti-4CN Substrate Trans-Blot® SD Semi-Dry Cell 14 and Detection Kits 38 Detection 66 Trans-Blot® Turbo™ System 14 Chemiluminescence Detection 38 Immunodetection 66 ™ ™ ™ Microfiltration Apparatus 14 Immun-Star AP Kits, Clarity and Clarity Max Multiscreen Apparatus 68 ® ® Bio-Dot and Bio-Dot SF Apparatus 14 Western ECL Substrates 40 Total Protein Detection 68 Power Supplies for Electrophoretic Transfers 15 Fluorescence Detection 40 PowerPac™ HC Power Supply 15 Other Detection Methods 41 PowerPac™ Universal Power Supply 15 Bioluminescence 41 Appendix 70 Chemifluorescence 42 Chapter 3 Membranes and Transfer Buffers 17 Autoradiography 42 Protein Standards for Blotting 70 Immunogold Labeling 42 Unstained Standards for Protein Blotting 71 Membranes and Blotting Papers 18 Stripping and Reprobing 42 Precision Plus Protein Unstained Standards 71 Nitrocellulose and Supported Nitrocellulose 18 Prestained Standards for Western Blotting 72 Polyvinylidene Difluoride (PVDF) 18 Imaging — Analysis and Documentation 43 Precision Plus Protein Prestained Standards 72 Immun-Blot® and Immun-Blot LF PVDF for Western Blotting 18 Luminescence Detection 43 Precision Plus Protein™ WesternC™ Standards 73 Sequi-Blot™ PVDF for Protein Sequencing 18 Digital Imaging for Fluorescence, Chemifluorescence, Blotting Filter Papers 19 and Colorimetric Detection 44 Glossary 74 Membrane/Filter Paper Sandwiches 19 Autoradiography 44 Analysis Software 44 References and Related Reading 78 Transfer Buffers 19 Towbin and Bjerrum Schafer-Nielsen Buffers Ordering Information 80 (Tris/Glycine Buffers) 20 Part 2 Methods 47 CAPS Buffer 20 Discontinuous Tris-CAPS Buffer System Protocols 48 (for Semi-Dry Transfer) 20 Electrophoretic Transfers 48 Dunn Carbonate Buffer 21 Reagent and Materials Preparation 48 Other Buffers 21 Tank Blotting Procedure 49 Prepare the Gel and Membrane Sandwich 49 Chapter 4 Transfer Conditions 23 Assemble the Tank and Program the Power Supply 50 General Workflow – Electrophoretic Transfer 24 Semi-Dry Blotting Procedure 51 Trans-Blot® Turbo™ Blotting Procedure 52 Power Conditions 24 Microfiltration 53 Useful Equations 24 Blot Stripping and Reprobing 54 Joule Heating and Other Factors Affecting Transfer 24 Total Protein Detection 55 Relationship Between Power Settings and Transfer Times 24 SYPRO Ruby Stain 55 High-Intensity Field Transfers 24 Ponceau S Stain 55 Standard Field Transfers 26 Colloidal Gold Total Protein Stain 55 Selecting Power Supply Settings 26 Immunodetection 56 Transfers Under Constant Voltage 26 Notes for Multiplex Detection 56 Transfers Under Constant Current 26 Notes for Chemiluminescence Detection 57 Transfers Under Constant Power 26 Notes for Fluorescence Detection 57 General Guidelines for Transfer Buffers and Note for Protein G-HRP Detection 57 Transfer Conditions 26 Notes for Amplified Opti-4CN™ Detection 57 Notes for Amplified AP Detection 57 2 3 Protein Blotting Guide Theory and Products PART 1 Theory and Products CHAPTER 1 Overview of Protein Blotting Protein blotting, the transfer of proteins to solid-phase membrane supports, is a powerful and popular technique for the visualization and identification of proteins. When bound to membranes, proteins are readily accessible for immunological or biochemical analyses, quantitative staining, or demonstration of protein- protein or protein-ligand interactions. This chapter provides an overview of the methods and workflow of protein blotting, which involves two phases: transfer and detection. 4 5 Protein Blotting Guide Theory and Products Transfer a result of the need to probe for proteins that were The first phase of protein blotting is the transfer step, inaccessible to antibodies while in polyacrylamide Protein Blotting Workflow which involves moving the proteins from a solution or gels. Western blotting involves the transfer of proteins gel and immobilizing them on a synthetic membrane that have been separated by gel electrophoresis onto support (blot). Proteins can be transferred to a membrane, followed by immunological detection membranes using a number of methods but the most of these proteins. Western blotting combines the Select the method common are electrophoretic transfer and microfiltration resolution of gel electrophoresis with the specificity of (dot blotting). Though diffusion or capillary blotting immunoassays, allowing individual proteins in mixtures methods may also be used to transfer proteins from to be identified and analyzed. Method selection depends largely on the starting sample gels, generally electrophoretic transfer is used to Since the development of immunoblotting techniques, (liquid protein sample or gel) transfer proteins following electrophoretic separation other probing and detection techniques have been by native or SDS-polyacrylamide gel electrophoresis developed for functional protein characterization (for (SDS-PAGE) and microfiltration is used to transfer a review, see Kurien and Scofield 2003). This manual proteins that are in solution. summarizes the most commonly used techniques, Detection provides information about the wide selection of blotting apparatus and detection reagents available from Bio-Rad, The second phase, detection, entails probing the Select the equipment and offers troubleshooting tips and technical advice. membrane with either a total protein stain or primary antibody specific to the protein of interest and General Considerations and Workflow Consider the experimental approach, sample subsequent visualization of the labeled proteins. The protein blotting workflow involves selection of the format, and desired resolution and throughput This involves a number of steps, including the appropriate method, apparatus, membrane, buffer, selection of the appropriate method, reagents, and and transfer conditions. Once proteins are immobilized imaging equipment. on a membrane, they are available for visualization, The most commonly used protein blotting technique, detection, and analysis. western blotting (immunoblotting), was developed as Prepare the reagent Selecting the appropriate membrane and transfer buffer is critical to successful protein transfer. Consider the size and charge of the proteins, the transfer method, and the binding properties of the membrane Perform the transfer Set up the transfer apparatus. For electrophoretic transfer, select the transfer conditions; use the highest electric field strength (V/cm) possible within the heat dissipation capabilities of the system Detect and image the protein The choice of staining or detection technique is determined by sensitivity requirements and the imaging equipment available 6 7 Protein Blotting Guide Theory and Products CHAPTER 2 Methods and Instrumentation The initial step in any blotting experiment is the selection of transfer method and appropriate transfer instrumentation. Method selection depends largely on the starting sample (liquid protein sample or gel); the instrumentation depends on the sample format and desired resolution and throughput. This chapter describes a number of the most common techniques and systems used today. 8 9 Protein Blotting Guide Theory and Products Protein Blotting Methods transfer or may cause the transfer buffer to lose its The two most common methods for protein buffering capacity. In addition, excessive heat may + – transfer are (Fig. 2.1): cause the gel to deteriorate and stick to the membrane. The major limitation of any electrophoretic transfer n Electrophoretic transfer — for proteins already method is the ability of the chamber to dissipate heat. separated in gels (for example, following + – polyacrylamide gel electrophoresis, or PAGE), There are two main types of electrophoretic blotting + ++ + ++ - electrophoretic transfer preserves the high- apparatus and transfer procedures (Table 2.1): – – resolution separation of proteins by PAGE n Tank transfer systems — gels and membranes are n Microfiltration — for proteins in solution, submerged under transfer buffer in