This work was supported by Fondo Nacional de Desarrollo Cient&#237;fico y Tecnol&#243;gico (Fondecyt), Chile, Project 11130263 (to CW), Project CONICYT + NERC + Programa de Colaboraci&#243;n Internacional PCI-PII20150073 (to CW) and U-inicia from the Vicerrector&#237;a de Investigaci&#243;n Universidad de Chile (to CW). 
Thanks to Tatiana Naranjo-Palma for the help in the initial stage of this Project, Dr. Jorge Babul and Diego Quiroga-Roger for helpful discussion, Robert Lesch for revising the manuscript and Direcci&#243;n de extensi&#243;n de la Facultad de Ciencias Qu&#237;micas y Farmac&#233;uticas from Universidad de Chile. Thanks too to Marcelo P&#233;rez for editing the video and Neil Stevens for correcting the text and Errol Watson for providing the voice-over.

1. Preparing and Running the Gel
<ol>
	<li>Prepare the non-denaturing 12% polyacrylamide gel gels using the Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) recipe found in Sambrook and Russell14 but using water instead of SDS.
	<ol>
		<li>To prepare 5 mL of resolving gel, use 1.7 mL of distilled water, 2 mL of acrylamide/bis acrylamide (30/0.8% w/v), 1.3 mL of 1.5 M Tris pH 8.8, 0.05 mL of 10% ammonium persulfate, and 0.002 mL of TEMED.</li>
		<li>To prepare 2 mL of stacking...

<ol>
	<li>LePecq, J. B., Paoletti, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fluorescent+complex+between+ethidium+bromide+and+nucleic+acids:+physical-chemical+characterization.">A fluorescent complex between ethidium bromide and nucleic acids: physical-chemical characterization.</a> J. Mol. Biol. 27 (1), 87-106 (1967).</li><li>Singer, V. L., Lawlor, T. E., Yue, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+SYBR+Green+I+nucleic+acid+gel+stain+mutagenicity+and+ethidium+bromide+mutagenicity+in+the+Salmonella/mammalian+microsome+reverse+mutation+assay+(Ames+test).">Comparison of SYBR Green I nucleic acid gel stain mutagenicity and ethidium bromide mutagenicity in the Salmonella/mammalian microsome reverse mutation assay (Ames test).</a> Mutat Res. 439 (1), 37-47 (1999).</li><li>Xin, X., Yue, S., Wells, K. S., Singer, V. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SYBR+Green-I:+a+new+fluorescent+dye+optimized+for+detection+picogram+amounts+of+DNA+in+gels.">SYBR Green-I: a new fluorescent dye optimized for detection picogram amounts of DNA in gels.</a> Biophys. J. 66 (A150), (1994).</li><li>Flores, N., Valle, F., Bolivar, F., Merino, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recovery+of+DNA+from+agarose+gels+stained+with+methylene+blue.">Recovery of DNA from agarose gels stained with methylene blue.</a> Biotechniques. 13 (2), 203-205 (1992).</li><li>Yang, Y. I., Jung, D. W., Bai, D. G., 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=Counterion-dye+staining+method+for+DNA+in+agarose+gels+using+crystal+violet+and+methyl+orange.">Counterion-dye staining method for DNA in agarose gels using crystal violet and methyl orange.</a> Electrophoresis. 22 (5), 855-859 (2001).</li><li>Yang, Y. I., 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=Detection+of+DNA+using+a+visible+dye,+Nile+blue,+in+electrophoresed+gels.">Detection of DNA using a visible dye, Nile blue, in electrophoresed gels.</a> Anal. Biochem. 280 (2), 322-324 (2000).</li><li>Santill&#225;n-Torres, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+stain+for+DNA+in+agarose+gels.">A novel stain for DNA in agarose gels.</a> Trends Genet. 9 (2), 40 (1993).</li><li>Adkins, S., Burmeister, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+DNA+in+agarose+gels+as+migrating+colored+bands:+applications+for+preparative+gels+and+educational+demonstrations.">Visualization of DNA in agarose gels as migrating colored bands: applications for preparative gels and educational demonstrations.</a> Anal. Biochem. 240 (1), 17-23 (1996).</li><li>Cong, W. T., 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+visible+dye-based+staining+method+for+DNA+in+polyacrylamide+gels+by+ethyl+violet.">A visible dye-based staining method for DNA in polyacrylamide gels by ethyl violet.</a> Anal. Biochem. 402 (1), 99-101 (2010).</li><li>Altman, F. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tetrazolium+salts+and+formazans.">Tetrazolium salts and formazans.</a> Prog. Histochem. Cytochem. 9 (3), 1-56 (1976).</li><li>Nineham, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chemistry+of+formazans+and+tetrazolium+salts.">The chemistry of formazans and tetrazolium salts.</a> Chem. Rev. 55 (2), 355-483 (1955).</li><li>Crandall, I. E., Zhao, B., Vlahakis, J. Z., Szarek, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+interaction+of+imidazole-,+imidazolium,+and+tetrazolium-containing+compounds+with+DNA.">The interaction of imidazole-, imidazolium, and tetrazolium-containing compounds with DNA.</a> Bioorg. Med. Chem. Lett. 23 (5), 1522-1528 (2013).</li><li>Paredes, A. J., 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=New+visible+and+selective+DNA+staining+method+in+gels+with+tetrazolium+salts.">New visible and selective DNA staining method in gels with tetrazolium salts.</a> Anal. Biochem. 517, 31-35 (2017).</li><li>Green, M. R., Sambrook, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Cloning: a Laboratory Manual. , (2012).</li><li>Hansen, W., Garcia, P. D., Walter, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+protein+translocation+across+the+yeast+endoplasmic+reticulum:+ATP-dependent+post-translational+translocation+of+the+prepro-&#945;-factor.">In vitro protein translocation across the yeast endoplasmic reticulum: ATP-dependent post-translational translocation of the prepro-&#945;-factor.</a> Cell. 45 (3), 397-406 (1986).</li><li>Inoue, H., Nojima, H., Okayama, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+efficiency+transformation+of+Escherichia+coli+with+plasmids.">High efficiency transformation of Escherichia coli with plasmids.</a> Gene. 96 (1), 23-28 (1990).</li><li>Madigan, M., Martinko, J., Parker, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Brock biology of microorganisms. , (2003).</li></ol>

The authors have nothing to disclose.

A sensitive and novel DNA staining method based on the reduction of NBT and the use of SG I was presented in this article. The critical step in this protocol is the incubation time of the gel in the NBT-SG I solution and the concentration of NBT. The staining time for agarose gels is longer than for acrylamide gels because of the greater thickness of agarose gels. This method does not work well in the presence of SDS as NBT precipitates in contact with it. If the gel obtains a purple background, we recommend that another...

With the advances in biochemistry and molecular biology, the studies involving DNA have required better techniques to analyze DNA. The first method for DNA staining was silver staining, which is very sensitive but lacks selectivity and does not allow sample recovery. Later, the development of fluorescent DNA staining allowed the selective quantification of DNA with the possibility of sample recovery. One of the first fluorescent dyes used for DNA quantification was ethidium bromide1, which is mutagenic2. However, now there are improved fluorescent dyes that are safer and more sensitive, such as GelRed and SYBR Green I (SG I)3; but all of these fluorescent dyes require the use of an ultraviolet (UV) transilluminator or fluorimeter.
There are other techniques for visibly staining DNA, such as methylene blue4 and crystal violet5,6,7,8,9, but all of these suffer from reduced sensitivity and selectivity.The tetrazolium salts are organic compounds susceptible to reduction, and when this happens they form an insoluble and colored formazan precipitate10,11. Recently, some bivalent tetrazolium salts have been shown to bind to DNA due to their positive tetrazolium rings12.
In a recent publication13, a new visible technique to stain and quantify DNA in polyacrylamide gels was proposed, using the reduction of a bivalent tetrazolium salt called nitro blue tetrazolium (NBT) and fluorescent dyes like ethidium bromide, GelRed, SYBR Green I and SYBR Gold. This reaction worked in the presence of blue light or sunlight and allowed sample recovery with improved quality compared to the use of SG I with a UV transilluminator.The objective of this paper is to provide a detailed protocol of the staining technique using tetrazolium salts.

<table border="0" cellpadding="0" cellspacing="0" width="785">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">Nitro blue tetrazolium</td>
			<td style="width:227px;">Gold Biotechnology</td>
			<td style="width:307px;">298-83-9</td>
			<td style="width:64px;">reagent used in the staining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">SYBR Green I 10000X</td>
			<td style="width:227px;">Thermo-Fisher</td>
			<td style="width:307px;">S7563</td>
			<td>reagent used in the staining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">Gel extraction kit</td>
			<td style="width:227px;">QIAGEN</td>
			<td style="width:307px;">28704</td>
			<td>used to extract plasmid from the gel in integrity assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">DNA ladder</td>
			<td style="width:227px;">Thermo-Fisher</td>
			<td style="width:307px;">SM 1331</td>
			<td>used to make calibration curves and as reference to cut band in integrity assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">Agar Agar</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;"></td>
			<td>used to make LB-ampicillin culture plates&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">sodium chloride</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">1064045000</td>
			<td>used to make LB-ampicillin culture plates&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">yeast extract</td>
			<td style="width:227px;">Becton, Dickinson and Company</td>
			<td style="width:307px;">212750</td>
			<td>used to make LB-ampicillin culture plates&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">peptone</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">72161000</td>
			<td>used to make LB-ampicillin culture plates&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">TEMED</td>
			<td style="width:227px;">AMRESCO</td>
			<td style="width:307px;">761</td>
			<td>used to make polyacrylamide gels</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">ammonium persulfate</td>
			<td style="width:227px;">Calbiochem</td>
			<td style="width:307px;">2310</td>
			<td>used to make polyacrylamide gels</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">acrylamide</td>
			<td style="width:227px;">invitrogen</td>
			<td style="width:307px;">15512-023</td>
			<td>used to make polyacrylamide gels</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">bisacrylamide</td>
			<td style="width:227px;">SIGMA</td>
			<td style="width:307px;">146072</td>
			<td>used to make polyacrylamide gels</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">Tris-base</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">1083821000</td>
			<td>used to make TAE buffer and non-denaturing polyacrylamide gel tris-HCl buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">EDTA</td>
			<td style="width:227px;">J.T. Baker</td>
			<td style="width:307px;">8993-01</td>
			<td>used to make TAE buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">Acetic acid</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">1,000,632,500</td>
			<td>used to make TAE buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">agarose</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">16802</td>
			<td>used to make TAE buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">spectrophotometer</td>
			<td style="width:227px;">Tecan</td>
			<td style="width:307px;">infinite 200 pro</td>
			<td>used to quantify DNA plasmid</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">water purificatiom unit</td>
			<td style="width:227px;">Merck</td>
			<td style="width:307px;">Elix 100</td>
			<td>use to make water type 1 (ASTM) used in spectrophotometry and DNA dilutions\</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">distilled water</td>
			<td style="width:227px;"></td>
			<td style="width:307px;">-</td>
			<td>used in gels, culture medium, stainings and general solutions</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">HCl</td>
			<td style="width:227px;">J.T. Baker</td>
			<td>9535-03</td>
			<td>used to make non-denaturing polyacrylamide gel tris-HCl buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">6X DNA loading dye</td>
			<td style="width:227px;">Thermo-Fisher</td>
			<td style="width:307px;">R0610</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">5 mm Blue LED</td>
			<td style="width:227px;">Jinyuan electronics</td>
			<td style="width:307px;">SP-021</td>
			<td>light source used in integrity assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">protoboard</td>
			<td style="width:227px;">KANDH</td>
			<td style="width:307px;">KH102</td>
			<td>light source support and circuit&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">9 V battery</td>
			<td style="width:227px;">Duracell</td>
			<td style="width:307px;">-</td>
			<td>used to power the LED&#39;s</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:187px;">horizontal electrophoresis chamber</td>
			<td style="width:227px;">Biorad</td>
			<td style="width:307px;">1704486EDU</td>
			<td>used to make and run agarose gel in integrity assay</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">vertical electrophoresis kit</td>
			<td style="width:227px;">Biorad</td>
			<td style="width:307px;">1658002EDU</td>
			<td>used to run polyacrylamide gels in calibration curves</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:187px;">power supply</td>
			<td style="width:227px;">Biorad</td>
			<td style="width:307px;">1645050&#160;</td>
			<td>used to power the electrophoresis</td>
		</tr>
	</tbody>
</table>

dna staining method based on formazan precipitation induced by blue light exposure

DNA staining methods are very important for biomedical research. We designed a simple method that allows DNA visualization to the naked eye by the formation of a colored precipitate. It works by soaking the acrylamide or agarose DNA gel in a solution of 1x (equivalent to 2.0 &#181;M) SYBR Green I (SG I) and 0.20 mM nitro blue tetrazolium that produces a purple precipitate of formazan when exposed to sunlight or specifically blue light. Also, DNA recovery tests were performed using an ampicillin resistant plasmid in an agarose gel stained with our method. A larger number of colonies was obtained with our method than with traditional staining using SG I with ultraviolet illumination. The described method is fast, specific, and non-toxic for DNA detection, allowing visualization of biomolecules to the "naked eye" without a transilluminator, and is inexpensive and appropriate for field use. For these reasons, our new DNA staining method has potential benefits to both research and industry.

A purple formazan precipitate appears where the DNA is located (verified by mass spectrometry13). In the experiment, a DNA ladder was loaded to make a calibration curve (Figure 3). The protocol works for both acrylamide and agarose gels, but it has a lower intensity and takes a longer time in agarose. However, the use of agarose gels allows the recovery of the sample using a commercially available kit, and it does not interfere with th...

Watch this Scientific Journal Video about DNA Staining Method Based on Formazan Precipitation Induced by Blue Light Exposure at JoVE.com

DNA Staining Method Based on Formazan Precipitation Induced by Blue Light Exposure

This method allows selective staining and quantification of DNA in gels by soaking the gel in a SYBR Green I/Nitro Blue Tetrazolium solution and then exposing it to sunlight or a blue light source. This produces a visible precipitate and requires almost no equipment, making it ideal for field use.

DNA staining methods are very important for biomedical research. We designed a simple method that allows DNA visualization to the naked eye by the ...

The DNA staining protocol has three general steps. The first is to put the gel in a solution of SYBR Green I and nitro blue tetrazolium, also known as NBT. The gel is then stirred for 25 minutes if it is a polyacrylamide gel and an hour if it is an agarose gel.The last step is to expose the gel to a blue light source such as blue LEDs or sunlight. During this step some precipitate bands appears. These bands have a direct correlation with the DNA concentration and the gel then can be digitalized in an office scanner in order to quantify the DNA.For the polyacrylamide gel, a non-denaturing polyacrylamide gel is prepared. The gel is then loaded with the samples and the electrophoresis process starts. SYBR Green I being diluted to 1.2X and the NBT 20 millimolar solutions are now prepared.The gel is put into a plastic container and 16.75 mils of the diluted SYBR Green I and 325 mils of the NBT at 20 millimolar are added. Then the container is covered with Parafilm and aluminum foil and stirred at 60 rpm for 25 minutes. Finally the aluminum foil and a Parafilm is removed and the gel is exposed to sunlight or a blue light source.For band quantification and calibration curves, the gel is put into an office scanner, then the image is analyzed using an image analysis software. Finally, a graft of normalized signal versus concentration is made. An agarose gel is made.The wells are loaded with a plasmid that has ampicillin resistance and the gel is cut into two pieces, each of which is stained with a different stain. Then the plasmid band is extracted and transformed via chemical transformation into competent cells with media that contains ampicillin. A 1%agarose gel is prepared in TAE 1X buffer and loaded with four microliters of plasmid at around 100 nanograms per microliter.The gel in the electrophoresis chamber is then run at 100 volts for one hour. Half the gel is stained with SYBR Green I and NBT method and the other half with SYBR Green I UV method. For agarose gel, the SYBR Green I NBT method is performed using SBYR Green I at a concentration of 1.2X and NBT at 2 millimolar.The gel is put into a plastic container and the solution volume is scaled to cover the gel and the stirring time is extended to one hour. For agarose gels, the commonly used SYBR Green I method is performed by covering the gel with 1X SYBR Green I solution and stirring for an hour. Then the gel is exposed to a UV transilluminator for band visualization for two minutes.Once the gel is stained, the plasmid band is cut with a scalpel and the plasmid extracted with a commercial extraction kit. The DNA is normalized to 9.1 nanograms per microliter for transforming chemical competent Escherichia coli XL 10 bacteria. Finally, the colonies are counted.The colony-forming units are calculated. The result is grafted and the results obtained from SYBR Green I NBT and SYBR Green I UV compared. A purple formazan precipitate appears where the DNA is located.In the experiment a DNA ladder was loaded to make a calibration curve with a detection limit of 192 picograms at 1, 500 base pairs. The use of agarose gels allows the sample recovery using commercially available kit and does not interfere with the extraction. Some recovery using this method with blue LED results in better quality compared to the SYBR Green I using transilluminator.

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Biochemistry

9.3K visualizações.  Universidad de Chile. The DNA staining protocol has three general steps. The first is to put the gel in a solution of SYBR Green I and nitro blue tetrazolium, also known as NBT. The gel is then stirred for 25 minutes if it is a polyacrylamide gel and an hour if it is an agarose gel.The last step is to expose the gel to a blue light source such as blue LEDs or sunlight. During this step some precipitate bands appears. These bands have a direct correlation with the DNA concentration and the gel then can be di...