Name: fluorescent silver staining of proteins in polyacrylamide gels
Uploaded: 2019-04-21T13:00:00
Description: Watch this Scientific Journal Video about Fluorescent Silver Staining of Proteins in Polyacrylamide Gels at JoVE.com

The authors would like to thank Patrick Chan at the Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, for his technical support. S. X. is grateful for the support from the Swedish Research Council (Grant No. 2017-06344).

1. Preparation of the Gel
Note: The demonstration follows a standard protocol to prepare the gel for staining shortly after SDS-PAGE12. In brief, the following steps describe the preparation of the samples and gel electrophoresis.
<ol>
	<li>Perform SDS-PAGE with 4% - 12% Bis-Tris protein gels (1 mm, 15-well) using a mini gel tank filled with 2-(N-morpholino)ethanesulfonic acid (MES) buffer.</li>
	<li>Dilute the samples with a mixture of distilled water, lithi...

<ol>
	<li>Chevalier, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highlights+on+the+capacities+of+&amp;#34;Gel-based&amp;#34;+proteomics.">Highlights on the capacities of &amp;#34;Gel-based&amp;#34; proteomics.</a> Proteome Science. 8 (1), (2010).</li><li>Harris, L. R., Churchward, M. A., Butt, R. H., Coorssen, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+detection+methods+for+gel-based+proteomic+analyses.">Assessing detection methods for gel-based proteomic analyses.</a> Journal of Proteome Research. 6 (4), 1418-1425 (2007).</li><li>Gauci, V. J., Wright, E. P., Coorssen, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+proteomics:+assessing+the+spectrum+of+in-gel+protein+detection+methods.">Quantitative proteomics: assessing the spectrum of in-gel protein detection methods.</a> Journal of Chemical Biology. 4 (1), 3-29 (2011).</li><li>Candiano, G., Bruschi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blue+silver:+A+very+sensitive+colloidal+Coomassie+G-250+staining+for+proteome+analysis.">Blue silver: A very sensitive colloidal Coomassie G-250 staining for proteome analysis.</a> Electrophoresis. 25 (9), 1327-1333 (2004).</li><li>Chevallet, M., Luche, S., Rabilloud, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver+staining+of+proteins+in+polyacrylamide+gels.">Silver staining of proteins in polyacrylamide gels.</a> Nature Protocols. 1 (4), 1852-1858 (2006).</li><li>Jin, L. T., Hwang, S. Y., Yoo, G. S., Choi, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensitive+silver+staining+of+protein+in+sodium+dodecyl+sulfate-polyacrylamide+gels+using+an+azo+dye,+calconcarboxylic+acid,+as+a+silver-ion+sensitizer.">Sensitive silver staining of protein in sodium dodecyl sulfate-polyacrylamide gels using an azo dye, calconcarboxylic acid, as a silver-ion sensitizer.</a> Electrophoresis. 25 (15), 2494-2500 (2004).</li><li>Celis, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cell Biology: A Laboratory Handbook. , (2006).</li><li>Bartsch, H., Arndt, C., Koristka, S., Cartellieri, M., Bachmann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver+Staining+Techniques+of+Polyacrylamide+Gels.">Silver Staining Techniques of Polyacrylamide Gels.</a> Methods in Molecular Biology. 869 (1), 481-486 (2012).</li><li>Rabilloud, T., Vuillard, L., Gilly, C., Lawrence, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver-staining+of+proteins+in+polyacrylamide+gels:+a+general+overview.">Silver-staining of proteins in polyacrylamide gels: a general overview.</a> Cellular and Molecular Biology. 40 (1), 57-75 (1994).</li><li>Zhou, M., Yu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+Analysis+by+Two-Dimensional+Polyacrylamide+Gel+Electrophoresis.">Proteomic Analysis by Two-Dimensional Polyacrylamide Gel Electrophoresis.</a> Advances in Protein Chemistry. 65 (1), 57-84 (2003).</li><li>Xie, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorogenic+Ag+-Tetrazolate+Aggregation+Enables+Efficient+Fluorescent+Biological+Silver+Staining.">Fluorogenic Ag+-Tetrazolate Aggregation Enables Efficient Fluorescent Biological Silver Staining.</a> Angewandte Chemie International Edition. 57 (20), 5750-5753 (2018).</li><li>. Protein gel electrophoresis technical handbook Available from: <a target="_blank" href="https://www.thermofisher.com/content/dam/LifeTech/global/Forms/PDF/protein-gel-electrophoresis-technical-handbook.pdf">https://www.thermofisher.com/content/dam/LifeTech/global/Forms/PDF/protein-gel-electrophoresis-technical-handbook.pdf</a> (2015)</li></ol>

Presented here is a novel fluorescent silver staining method for proteins in polyacrylamide gels. This strategy integrates conventional silver stains and fluorescent stains. The staining exploits the selective binding of silver ion to proteins as in other silver stains but employs a highly sensitive fluorogenic silver probe TPE-4TA to light up the silver bound proteins. Since the fluorogenic probe TPE-4TA can sense silver ions at a fairly low concentration in the nanomolar range<sup clas...

Many staining methods have been used to visualize proteins following gel electrophoresis, for example using colorimetric dyes such as Coomassie Brilliant Blue, silver stain, fluorescence, or radioactive labeling1,2,3,4. Silver staining is considered to be one of the most sensitive techniques for protein detection requiring simple and cheap reagents. It can be categorized into two major families: the ammoniacal silver stain and the silver nitrate stain5,6. In the alkaline ammoniacal silver method, the silver-diamine complex is produced with ammonia and sodium hydroxide and reduced to metallic silver during development using an acidic formaldehyde solution. The stain accommodates efficiently for basic proteins but shows a compromised performance for acidic and neutral proteins and is, furthermore, limited to classical glycine and taurine electrophoretic systems. In comparison, the silver nitrate stains exploit the high bio-affinity of silver ions to protein, primarily the sulfhydryl and carboxyl groups from the side chains, and tend to stain acidic proteins more efficiently7. After silver ion binding, a developing solution (typically made of a metal carbonate solution containing formaldehyde and sodium thiosulphate) is applied to reduce silver ions to metallic silver grains, which build up a brown-to-dark color to visualize the protein bands.
Although silver staining has been well known for its versatility and high sensitivity since its development in the 1970s8, the method is frequently regarded as tricky. Silver-staining methods have time-restricted steps and show low reproducibility. Since the color of silver stain is usually not uniform and dependent on the reduction step, which is hard to control, the silver stain is not a quantitative method and, thus, not recommended for gel comparison study and protein quantification9. Methods optimized in sensitivity may utilize aldehydes which can also provide a more uniform staining10. However, this is at the expense of further downstream analysis due to the crosslinking of proteins by aldehydes. Fast protocols mostly combine or shorten steps to reduce time, compromising the reproducibility and uniformity of the stain5. As a result, there are numerous silver staining variants within protein gel staining, each optimized to suit certain requirements; for example, simplicity, sensitivity, or peptide recovery rate for downstream analysis. These attributes may also have an impact on each other, and satisfying all requirements in one protocol can be difficult.
In this work, we introduce a new fluorescent silver staining method for protein detection in polyacrylamide gel. In this method, we use a fluorogenic probe for silver ions, TPE-4TA (Figure 1), to visualize the silver-impregnated proteins11. TPE-4TA is designed by the aggregation-induced emission (AIE) principle. It is non-emissive when dissolved in aqueous solution, but is highly emissive in the presence of silver ions. By replacing the chromogenic development in traditional silver stains with a fluorogenic developing step, the fluorescent silver method enables the robust staining of total proteins with a reduced background.
Furthermore, the fluorescent silver stain showed a good dynamic linear range for protein quantification, which is comparable with the widely-used SYPRO Ruby stain and not achievable with traditional silver stains. The gel can be imaged on commonly used gel documentation systems with an ultraviolet lamp (excitation wavelength: 302/365 nm channel; emission: ~490 - 530 nm) at many biological labs.

<table>
	<tbody>
		<tr>
			<td> 
			LDS Sample Buffer (4X)</td>
			<td>Thermo Fisher Scientific</td>
			<td>NP0007</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td> 
			4-12% Bis-Tris Protein Gels, 1.0 mm, 15-well</td>
			<td>Thermo Fisher Scientific</td>
			<td>NP0323BOX</td>
			<td>Precast gel</td>
		</tr>
		<tr>
			<td>Sample Reducing Agent (10X)</td>
			<td>Thermo Fisher Scientific</td>
			<td>NP0004</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>MES SDS Running Buffer (20X)</td>
			<td>Thermo Fisher Scientific</td>
			<td>NP0002</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Mini Gel Tank</td>
			<td>Thermo Fisher Scientific</td>
			<td>A25977</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>300W Power Supply (230 VAC)</td>
			<td>Thermo Fisher Scientific</td>
			<td>PS0301</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Unstained Protein Ladder</td>
			<td>Thermo Fisher Scientific</td>
			<td>26614</td>
			<td>Sample</td>
		</tr>
		<tr>
			<td>Silver nitrate</td>
			<td>Sigma-Aldrich</td>
			<td>31630-25G-R</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Bragg and co.</td>
			<td>42520J</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>J.T. Baker</td>
			<td>103201A</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Milli-Q Synthesis A10</td>
			<td>Merk</td>
			<td>-</td>
			<td>Provides 18.2 M&#937;.cm water</td>
		</tr>
		<tr>
			<td>gel documentation system (c600 model)</td>
			<td>Azure biosystems</td>
			<td>-</td>
			<td>Equipment</td>
		</tr>
	</tbody>
</table>

fluorescent silver staining of proteins in polyacrylamide gels

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The classic silver stains have certain drawbacks, such as high background staining, poor protein recovery, low reproducibility, a narrow linear dynamic range for quantification, and limited compatibility with mass spectrometry (MS). Now, with the use of a fluorogenic Ag+ probe, TPE-4TA, we developed a fluorescent silver staining method for the total protein visualization in polyacrylamide gels. This new stain avoids the troublesome silver reduction step in traditional silver stains. Moreover, the fluorescent silver stain demonstrates good reproducibility, sensitivity, and linear quantification in protein detection, making it a useful and practical protein gel stain.

The protein bands stained by the fluorescent silver stain exhibit an intense green fluorescence under a 365 nm UV lamp. All 14 protein bands (10 - 200 kDa), from top to bottom, were clearly visible, correlating well with the 14 red-colored ones stained by the SYPRO Ruby dye (Figure 2)10.
Regarding quantitative protein detection, the gels were imaged by a gel imaging system us...

Watch this Scientific Journal Video about Fluorescent Silver Staining of Proteins in Polyacrylamide Gels at JoVE.com

Fluorescent Silver Staining of Proteins in Polyacrylamide Gels

Here, we describe a detailed protocol outlining a new fluorescent staining technique for total protein detection in polyacrylamide gels. The protocol utilizes a silver ion-specific fluorescence turn-on probe, which detects Ag+-protein complexes, and eliminates certain limitations of traditional chromogenic silver stains.

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide ...

Research

JoVE Journal

Biochemistry

Characterization of Multi-subunit Protein Complexes of Human MxA Using Non-denaturing Polyacrylamide Gel-electrophoresis

The formation of oligomeric complexes is a crucial prerequisite for the proper structure and function of many proteins. The interferon-induced antiviral ...

Voltage-clamp Fluorometry in Xenopus Oocytes Using Fluorescent Unnatural Amino Acids

Voltage-clamp Fluorometry in Xenopus Oocytes Using Fluorescent Unnatural Amino Acids

Voltage-Clamp Fluorometry (VCF) has been the technique of choice to investigate the structure and function of electrogenic membrane proteins where ...

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Isolation of Glomeruli and In Vivo Labeling of Glomerular Cell Surface Proteins

Proteinuria results from the disruption of the glomerular filter that is composed of the fenestrated endothelium, glomerular basement membrane, and ...

How to Quantify the Fraction of Photoactivated Fluorescent Proteins in Bulk and in Live Cells

Photoactivatable and -convertible fluorescent proteins (PA-FPs) have been used in fluorescence live-cell microscopy for analyzing the dynamics of cells ...

Structure Solution of the Fluorescent Protein Cerulean Using MeshAndCollect

X-ray crystallography is the major technique used to obtain high resolution information concerning the 3-dimensional structures of biological ...

Use of Recombinant Fusion Proteins in a Fluorescent Protease Assay Platform and Their In-gel Renaturation

Proteases are intensively studied enzymes due to their essential roles in several biological pathways of living organisms and in pathogenesis; therefore, ...

Fluorescent Visualization of Mango-tagged RNA in Polyacrylamide Gels via a Poststaining Method

Native and denaturing polyacrylamide gels are routinely used to characterize ribonucleoprotein (RNP) complex mobility and to measure RNA size, ...

Localization of SUMO-modified Proteins Using Fluorescent Sumo-trapping Proteins

Here we are presenting a novel method to study the sumoylation of proteins and their sub-cellular localization in mammalian cells and nematode oocytes. ...

Characterizing Cellular Proteins with In-cell Fast Photochemical Oxidation of Proteins

Fast photochemical oxidation of proteins (FPOP) is a hydroxyl radical protein footprinting method used to characterize protein structure and interactions. ...

Transverse Sectioning of Mature Rice (Oryza sativa L.) Kernels for Scanning Electron Microscopy Imaging Using Pipette Tips as Immobilization Support