This work was supported by the Sogang University Research Grant of 201410036.

1. DNA Biotinylation
<ol>
	<li>Biotinylation of blunt ended DNA using Terminal Transferase (TdT) 
	Note: Use T4 DNA (166 kbp), which is a blunt ended DNA.
	<ol>
		<li>Add 5 &#181;l of 2.5 mM CoCl2, 5 &#181;l of 10&#215; reaction buffer, 0.5 &#181;l of 10 mM biotin-11-dUTP, 0.5 &#181;l of terminal transferase (10 units), and 0.5 &#181;l of T4 DNA (0.5 &#181;g/&#181;l) to the reaction mixture. Make to a final volume of 50 &#181;l by adding 38.5 &#181;l of water.</li>
		<li>Incubate the re...

<ol>
	<li>Smith, S. B., Finzi, L., Bustamante, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+Mechanical+Measurements+of+the+Elasticity+of+Single+DNA-Molecules+by+Using+Magnetic+Beads.">Direct Mechanical Measurements of the Elasticity of Single DNA-Molecules by Using Magnetic Beads.</a> Science. 258 (5085), 1122-1126 (1992).</li><li>Finkelstein, I. J., Visnapuu, M. -. L., Greene, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-molecule+imaging+reveals+mechanisms+of+protein+disruption+by+a+DNA+translocase.">Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase.</a> Nature. 468 (7326), 983-987 (2010).</li><li>Doyle, P. S., Ladoux, B., Viovy, 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=Dynamics+of+a+tethered+polymer+in+shear+flow.">Dynamics of a tethered polymer in shear flow.</a> Phys. Rev. Lett. 84 (20), 4769-4772 (2000).</li><li>Perkins, T. T., Quake, S. R., Smith, D. E., Chu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relaxation+of+a+Single+DNA+Molecule+Observed+by+Optical+Microscopy.">Relaxation of a Single DNA Molecule Observed by Optical Microscopy.</a> Science. 264 (5160), 822-826 (1994).</li><li>Cai, W., 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=Ordered+restriction+endonuclease+maps+of+yeast+artificial+chromosomes+created+by+optical+mapping+on+surfaces.">Ordered restriction endonuclease maps of yeast artificial chromosomes created by optical mapping on surfaces.</a> Proc. Natl. Acad. Sci. U.S.A. 92 (11), 5164-5168 (1995).</li><li>Kim, Y., Jo, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutravidin+coated+surfaces+for+single+DNA+molecule+analysis.">Neutravidin coated surfaces for single DNA molecule analysis.</a> Chem. Comm. 47 (22), 6248-6250 (2011).</li><li>Kim, Y., 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=Nanochannel+confinement:+DNA+stretch+approaching+full+contour+length.">Nanochannel confinement: DNA stretch approaching full contour length.</a> Lab on a Chip. 11 (10), 1721-1729 (2011).</li><li>Glazer, A. N., Rye, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+dye-DNA+intercalation+complexes+as+reagents+for+high-sensitivity+fluorescence+detection.">Stable dye-DNA intercalation complexes as reagents for high-sensitivity fluorescence detection.</a> Nature. 359 (6398), 859-861 (1992).</li><li>Graneli, A., Yeykal, C. C., Prasad, T. K., Greene, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organized+arrays+of+individual+DNA+molecules+tethered+to+supported+lipid+bilayers.">Organized arrays of individual DNA molecules tethered to supported lipid bilayers.</a> Langmuir. 22 (1), 292-299 (2006).</li><li>Lee, 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=DNA+binding+fluorescent+proteins+for+the+direct+visualization+of+large+DNA+molecules.">DNA binding fluorescent proteins for the direct visualization of large DNA molecules.</a> Nucleic Acids Res. , (2015).</li><li>Roy, R., Hohng, S., Ha, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+single-molecule+FRET.">A practical guide to single-molecule FRET.</a> Nat Methods. 5 (6), 507-516 (2008).</li><li>Chandradoss, S. D., 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=Surface+passivation+for+single-molecule+protein+studies.">Surface passivation for single-molecule protein studies.</a> J. Vis. Exp. (86), e50549 (2014).</li></ol>

The authors have nothing to disclose.

Here we present a platform for visualizing long DNA molecules biotinylated for anchoring on surfaces. We have reported an approach for DNA molecules tethered on an avidin protein coated surface with biotinylated bovine serum albumin.6 In the earlier approach, we found a crucial issue of DNA photo-cleavage caused by bis-intercalation dyes that stain DNA molecules tethered on the surface. As these continually excited fluorophores have a high probability to attack a DNA phosphate backbone,9 the excitat...

Visualization of large DNA molecules tethered on glass or bead surfaces has been utilized for investigating DNA-protein interactions, protein dynamics on DNA substrate,1,2 and polymer physics.3,4 A platform for single-tethered large DNA molecules has a few distinct advantages compared to other DNA immobilization methods.5 First, a large DNA molecule tethered on the surface has a natural random-coil conformation without a shear flow, which is critically important for a DNA-binding protein to recognize its binding site. Second, it is very easy to change the chemical environment around DNA molecules for a series of enzymatic reactions in a flow chamber. Third, a microfluidic shear flow induces DNA molecular stretching up to 100% of the full contour length, which is very difficult to achieve using alternative DNA elongation approaches such as surface immobilization6 and nanochannel confinement.7 A fully stretched DNA molecule also provides positional information that can be useful for monitoring enzymatic movements on the genomic map.
Nevertheless, the DNA tethering approach has a critical shortcoming in that the intercalating dye such as YOYO-1 generally causes tethered DNA molecules to be readily broken by fluorescence excitation light. Generally, large DNA molecules have to be stained with a fluorescent dye for visualization under a fluorescent microscope. For this purpose, YOYO-1 or other TOTO series dyes are primarily used because these dyes fluoresce only when they intercalate double-stranded DNA.8 However, it is well-known that bis-intercalating dye causes light-induced DNA photo-cleavage because of the intercalation of fluorophores.9 Further, fluorescently stained DNA molecules tethered on the surface are more fragile since shear flows can exert breaking forces on freely moving DNA molecules. Therefore, we developed FP-DBP as a novel DNA-staining protein dye for imaging large DNA molecules tethered on the surface. The advantage of using FP-DBP is that it does not cause photo-cleavage of the DNA molecules to which it binds.10 In addition, FP-DBP does not increase the contour length of DNA, while bis-intercalating dyes increase the contour length by about 33%.
This video method introduces the experimental approach for tethering large DNA molecules to a PEG-biotin surface. Figure 1 illustrates different approaches of tethering DNA with blunt ends and sticky ends. Thus, this staining method can be applied to any type of DNA molecule. Figure 2 depicts a schematic representation of the flow chamber assembly that can be controlled by a syringe pump to generate shear flows to stretch DNA molecules as well as to load chemical and enzyme solutions. Figure 3 demonstrates micrographs of fully stretched DNA molecules tethered on the PEGylated surface11 and stained with FP-DBP.

<table border="0" cellpadding="0" cellspacing="0" width="925">
	<tbody>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">1. DNA Biotinylation</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">1.1) Biotinylation of blunt-end DNA using Terminal Transferase (TdT)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Terminal Transferase</td>
			<td style="width:167px;">New England Biolabs</td>
			<td style="width:133px;">M0315S</td>
			<td>Provided with 10x reaction buffer, 2.5 mM Cobalt chloride</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Biotin-11-dUTP</td>
			<td style="width:167px;">Invitrogen</td>
			<td style="width:133px;">R0081</td>
			<td>Biotin-ddNTP is also available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">T4GT7 Phage DNA</td>
			<td style="width:167px;">Nippon Gene</td>
			<td style="width:133px;">318-03971</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Ethylenediaminetetraacetic acid</td>
			<td style="width:167px;">Sigma-Aldrich</td>
			<td style="width:133px;">E6758</td>
			<td>EDTA</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">1.2) Biotinylation of sticky end DNA Using DNA Ligase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">T4 DNA Ligase</td>
			<td style="width:167px;">New England Biolabs</td>
			<td style="width:133px;">M0202S</td>
			<td>Provided with 10x reaction buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:287px;">Lambda Phage DNA</td>
			<td style="width:167px;">Bioneer</td>
			<td style="width:133px;">D-2510</td>
			<td>Also available at New England Biolabs</td>
		</tr>
		<tr height="20">
			<td colspan="4" height="20" style="height:20px;width:925px;">2. Functionalized Surface Derivatization</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">2.1) Piranha Cleaning</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Coverslip</td>
			<td style="width:167px;">Marienfeld-Superior</td>
			<td style="width:133px;">0101050</td>
			<td>22x22 mm, No. 1 Thickness</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Teflon rack</td>
			<td style="width:167px;"></td>
			<td style="width:133px;"></td>
			<td>Custom Fabrication</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">PTFE Thread Seal Tape</td>
			<td style="width:167px;">Han Yang Chemical Co. Ltd.</td>
			<td style="width:133px;">3032292</td>
			<td>Teflon&#8482; tape</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Sulferic acid</td>
			<td style="width:167px;">Jin Chemical Co. Ltd.</td>
			<td style="width:133px;">S280823</td>
			<td>H2SO4, 95 % Purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Hydrogen peroxide</td>
			<td style="width:167px;">Jin Chemical Co. Ltd.</td>
			<td style="width:133px;">H290423</td>
			<td>H2O2, 35 % in water</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Sonicator</td>
			<td style="width:167px;">Daihan Scientific Co. Ltd.</td>
			<td style="width:133px;">WUC-A02H</td>
			<td>Table-top Ultrasonic Cleaner</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">2.2) Aminosilanization on Glass Surface</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">N-[3-(Trimethoxysilyl)propyl] 
			ethylenediamine</td>
			<td style="width:167px;">Sigma-Aldrich</td>
			<td style="width:133px;">104884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Glacial Acetic Acid</td>
			<td style="width:167px;">Duksan Chemicals</td>
			<td style="width:133px;">414</td>
			<td>99 % Purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Methyl Alcohol</td>
			<td style="width:167px;">Jin Chemical Co. Ltd.</td>
			<td style="width:133px;">M300318</td>
			<td>99.9 % Purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Polypropylene Container</td>
			<td style="width:167px;">Qorpak</td>
			<td style="width:133px;">PLC-04907</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Ethyl Alcohol</td>
			<td style="width:167px;">Jin Chemical Co. Ltd.</td>
			<td style="width:133px;">A300202</td>
			<td>99.9 % Purity</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">2.3) PEGylation of the coverslip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Sodium Bicarbonate</td>
			<td style="width:167px;">Sigma-Aldrich</td>
			<td style="width:133px;">S5761</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Syringe Filter</td>
			<td style="width:167px;">Sartorius</td>
			<td style="width:133px;">16534----------K</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Biotin-PEG-SC</td>
			<td style="width:167px;">Laysan Bio</td>
			<td style="width:133px;">Biotin-PEG-SC-5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">mPEG-SVG</td>
			<td style="width:167px;">Laysan Bio</td>
			<td style="width:133px;">MPEG-SVA-5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Acetone</td>
			<td style="width:167px;">Jin Chemical Co. Ltd.</td>
			<td style="width:133px;">A300129</td>
			<td>99 % Purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Microscope Slides</td>
			<td style="width:167px;">Marienfeld-Superior</td>
			<td style="width:133px;">1000612</td>
			<td>~76x26x1 mm</td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">3. Assembling a Flow Chamber</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Acrylic Support</td>
			<td style="width:167px;"></td>
			<td style="width:133px;"></td>
			<td>Custom Fabrication</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Double-sided Tape</td>
			<td style="width:167px;">3M</td>
			<td style="width:133px;"></td>
			<td>Transparent type</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Quick-dry Epoxy</td>
			<td style="width:167px;">3M</td>
			<td style="width:133px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Polyethylene Tubing</td>
			<td style="width:167px;">Cole-Parmer</td>
			<td style="width:133px;">06417-11, 06417-21</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Gas Tight 250 &#181;l Syringe</td>
			<td style="width:167px;">Hamilton</td>
			<td style="width:133px;">81165</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Syringe Pump</td>
			<td style="width:167px;">New Era Pump Systems Inc.</td>
			<td style="width:133px;">NE-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:925px;">4. Sample Loading into Flow Chamber</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Neutravidin</td>
			<td style="width:167px;">Thermo Scientific</td>
			<td style="width:133px;">31000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Tris base</td>
			<td style="width:167px;">Sigma-Aldrich</td>
			<td style="width:133px;">T1503-5KG</td>
			<td>Trizma base</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Microscope</td>
			<td style="width:167px;">Olympus</td>
			<td style="width:133px;">IX70</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">EMCCD Camera</td>
			<td style="width:167px;">Q Imaging</td>
			<td style="width:133px;">Rolera EM-C2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Solid-state Laser (488 nm)</td>
			<td style="width:167px;">Oxxius</td>
			<td style="width:133px;">LBX488</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Alconox</td>
			<td style="width:167px;">Alconox Inc.</td>
			<td style="width:133px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

visualization of surface-tethered large dna molecules with a fluorescent protein dna binding peptide

Large DNA molecules tethered on the functionalized glass surface have been utilized in polymer physics and biochemistry particularly for investigating interactions between DNA and its binding proteins. Here, we report a method that uses fluorescent microscopy for visualizing large DNA molecules tethered on the surface. First, glass coverslips are biotinylated and passivated by coating with biotinylated polyethylene glycol, which specifically binds biotinylated DNA via avidin protein linkers and significantly reduces undesirable binding from non-specific interactions of proteins or DNA molecules on the surface. Second, the DNA molecules are biotinylated by two different methods depending on their terminals. The blunt ended DNA is tagged with biotinylated dUTP at its 3' hydroxyl terminus, by terminal transferase, while the sticky ended DNA is hybridized with biotinylated complimentary oligonucleotides by DNA ligase. Finally, a microfluidic shear flow makes single DNA molecules stretch to their full contour lengths after being stained with fluorescent protein-DNA binding peptide (FP-DBP).

Figure 1 shows two different DNA tethering methods depending on terminal structures of the DNA molecule. Figure 1a illustrates how the sticky ended DNA molecules are hybridized with complementary biotinylated oligonucleotides, which are immobilized on the avidin-coated PEG surface. Figure 1b shows the addition of biotinylated ddNTP or dNTP to the 3&#39; hydroxyl group of a blunt ended DNA by terminal transferase. We added flexible linkers...

Watch this Scientific Journal Video about Visualization of Surface-tethered Large DNA Molecules with a Fluorescent Protein DNA Binding Peptide at JoVE.com

Visualization of Surface-tethered Large DNA Molecules with a Fluorescent Protein DNA Binding Peptide

We present an approach for visualizing fluorescent protein DNA binding peptide (FP-DBP)-stained large DNA molecules tethered on the polyethylene glycol (PEG) and avidin-coated glass surface and stretched with microfluidic shear flows.

Large DNA molecules tethered on the functionalized glass surface have been utilized in polymer physics and biochemistry particularly for investigating ...

The overall goal of this procedure, is to make a convenient DNA analysis system for an epifluorescent microscope, to manipulate single molecule DNA on modified glass surfaces. This method can help answer key questions in DNA visualization field. When examining DNA self, as well as DNA binding proteins and other small molecules.The main advantage of this technique is the ability to observe and analyze moving DNA with ease. To begin, place glass coverslips on a PTFE rack and secure them in place, using a piece of PTFE thread seal tape. After wrapping the coverslips, leave a five centimeter long piece of the tape to be used for handling the rack during the cleaning procedure.In a fume hood, combine 350 millileters of sulfuric acid and 150 milliliters of hydrogen peroxide in a one liter glass beaker to make a piranha etching solution. Then, place the rack of coverslips into the solution. After two hours, empty the beaker and rinse the coverslips thoroughly with deionized water.Continue rinsing the coverslips until the PH of water in the beaker, reaches a neutral PH.Then, sonicate the racks of coverslips in a beaker contaning water for 30 minutes, to clean and derivative the glass substrates. Empty water from the beaker, just before aminosilanization. To begin, prepare the aminosilanization solution, by adding two milliliters of alkoxysilane, and 10 milliliters glacial acetic acid to 200 milliliters of methyl alcohol in a clean, polypropylene container.Followed by placing the clean coverslips into the solution. Then, place the cleaned coverslips in the prepared solution and shake them at room temperature and 100 rpm's for 30 minutes. Next, sonicate the container with the derivatized coverslips for 15 minutes at 75 watts.Then, shake them again at room temperature and 100 rpm's for at least 30 minutes. Once finished, empty the solution from the beaker and rinse the coverslips three times, carefully. Once with methyl alcohol and twice with ethyl alcohol.Following the final rinse, store the coverslips in ethyl alcohol and use them within two weeks. First, make 10 milliliters of a 0.1 molars sodium bicarbonate solution and filter it through a 0.22 micron syringe filter. Then, dissolve two milligrams of biotin PEG succinimidyl carbonate and 80 milligrams of PEG succinimidyl valerate into 350 micro liters of the filtered sodium bicarbonate solution.Protect the solution from light using a light protection tube. Vortex the tube vigorously, for 10 seconds and then, centrifuge it at 10, 000 x g for one minute to remove any bubbles. Next, rinse a glass slide with acetone followed by ethyl alcohol.Once rinsed, allow the slide to air dry completely. Place a 50 microliter drop of the PEG solution onto the clean, glass slide. Slowly lower an amino silanized coverslip onto the droplet at a slight angle, so as to not generate any air bubbles under the coverslip.Then, place the slides into a level, dark and humidified chamber for at least three hours to overnight, at room temperature. When finished, seal the residual PEG solution in the light protection tube, and keep it at four degrees Celsius. Following incubation, rinse the PEGylated coverslips thoroughly with deionized water and then store them in a dark and dry place until they are used.In order to create the flow chamber, place double-sided, sticky tape strips on an acrylic holder, so that it is aligned perpendicularly to inlet and outlet holes and does not perturb any of the channel holes. Then, rub the tape, using a pipet tip, to seal the channels. Next, place a PEGylated coverslip, with the PEGylated side face down, on the top of the tape to make flow chambers.To prevent any solution from leaking, press the top of a coverslip over the area where double-sided tape is placed. Then, add a quick dry, epoxy glue to the edges of the chambers, to secure it in place. Next, connect a 2.5 centimeter long piece of tubing to a gas tight syringe and seal the joint with epoxy glue.Then, connect a long, flexible tube to the tubing coming from the syringe. And again, seal the joint with epoxy glue. Fill the tubing that is linked to the syringe with deionized water, making sure there are no air bubbles.Next, insert the tubing into the hole of the flow chamber that is sealed with epoxy glue. And place a 200 microliter pipet tip on the other hole, to be used as a reservoir. Set the flow rate of a syringe pump to 50 microliters per minute.Then, flow 20 microliters of an avidin protein solution into the chamber and keep it there for 10 minutes. Next, load 20 microliters of biotinylated oligo deoxy nucleotides, into a syringe. Flow it into the chamber, and keep it there for 10 minutes.If a terminal transferase is used, skip the loading of oligo deoxy nucleotides. Then, load 20 microliters of a DNA solution into a syringe, flow it into the chamber at a rate of 10 microliters per minute and keep it there for 30 minutes. Following the 30 minute incubation, wash the flow chamber with 40 microliters of 1X TE buffer at 50 microliters per minute.Once washed, load the chamber with 40 microliters of the same FP-DBP at a concentration of 80 nano-molar, in the 1X TE.To see the full stretch range of DNA molecules, apply different flow rates according to the DNA lengths used. Observe the DNA under a 60X objective lens, using a fluorescent microscope. Here is a fluorescent microscope video showing bacteriophage lambda DNA molecules, tethered to the surface, being stretched by flow after ligation with biotinylated complimentary oligo nucleotides.Under flow, the fully elongated DNA molecules, measure 16.5 microns in length. In contrast, the bacteriophage T4 DNA momlecules, elongated to a length of 56.4 microns, under flow. This elongation is reversible, and the DNA can be extended and relaxed multiple times.After watching this video, you should have a good understanding of how to use FP-DBP in larger DNA analysis as well as demonstrate stretching and relaxation of DNA polymer.

visualization-surface-tethered-large-dna-molecules-with-fluorescent

Research

JoVE Journal

Biology

10.6K Views.  Sogang University. The overall goal of this procedure, is to make a convenient DNA analysis system for an epifluorescent microscope, to manipulate single molecule DNA on modified glass surfaces. This method can help answer key questions in DNA visualization field. When examining DNA self, as well as DNA binding proteins and other small molecules.The main advantage of this technique is the ability to observe and analyze moving DNA with ease. To begin, place glass coverslips on a PTFE rack and secure them ...