Wir bedanken uns herzlich bei der Unterstützung der Nationalen Naturwissenschaftlichen Stiftung von China (Nr. 21205078) und des Forschungsfonds für das Doktoratsstudium für Hochschulbildung in China (No.20123120110002). Diese Arbeit wurde teilweise durch das nationale Schlüsselforschungs- und Entwicklungsprogramm von China (2016YFB1102303), das nationale grundlegende Forschungsprogramm von China (973Programm 2015CB352001) und die nationale natürliche Wissenschafts-Grundlage von China (61378060) unterstützt.

1. Grunddesign des SGE-Chips <ol><li> Verwenden Sie jeden transparenten Kunststoff, wie Polymethylmethacrylat (PMMA) oder Polycarbonat. Hinweis: Der SGE-Chip ist in Abbildung 1B dargestellt. Der SGE-Chip besteht aus zylindrischen Löchern für den TBE-Puffer, Kanäle für die DNA-Trennung und zwei Bahnen, die entlang der Löcher für die Elektrode eingebettet sind. </li><li> Fertigungsarrays von SGE-Kanälen im PMMA-Block mit einer Lasergravurmaschine. Anmerkung: Die geometrischen Parameter des Chips hängen von der Größe der zu trennenden DNA ab. Zum Beispiel sind die optimalen Kanalparameter für den SGE-Chip 2,5 mm x 4,0 mm x 90 mm (Breite x Tiefe x Länge), wenn das DNA-Fragment kleiner als 1000 bp ist. </li><li> Basierend auf dem SGE-Design, fertigen Kämme, um die Brunnen im Chip zum Laden der DNA-Probe zu erstellen. </li></ol> 2. Vorbereitung des Agarosegels <ol><li> Vorbereiten von 0,5 × TBE durch Mischen von 10 × TBE (1 × TBE =89 mM Tris, 89 mM Borsäure und 2 mM EDTA; PH 8,4) und destilliertem Wasser im Verhältnis 1:19 </li><li> Vorbereitung 1,0% Agarose Gel für die Trennung von 100-bp DNA-Leitern. Anmerkung: Die Konzentration der Agarose in 0,5x TBE-Puffer hängt von den Größen der zu trennenden DNA-Fragmente ab. </li><li> Setzen Sie 0,1 g Agarose in einen Kolben und fügen Sie 10 ml 0,5x TBE-Puffer hinzu. Hinweis: Das Volumen der vorbereiteten Lösung sollte weniger als 1/3 der Kapazität des Kolbens betragen. </li><li> Den Kolben mit Konservierungsfilm abdichten und dann die Agarose / Puffermischung in einer Mikrowelle (Medium, 1,0 min) erhitzen. Vor dem Einsetzen der Flasche in die Mikrowelle, machen einige Löcher in der Konservierungsfolie im Falle einer Explosion. </li><li> Gießen Sie 2,7 ml geschmolzene Agarose-Lösung in 4 Kanäle des SGE-Chips. Legen Sie den Kamm in die Agarose-Lösung, um die Brunnen zu schaffen. Hinweis: Die geschmolzene Agarose-Lösung wird bei Raumtemperatur 3 min später auf den Gelzustand abkühlen gelassen. </li><li> Den Kamm aus der G entfernenEls und füge 0,9 ml 0,5x TBE-Puffer hinzu, um das Gel zu bedecken. </li></ol> 3. Die Elektrophorese im SGE-Chip durchführen <ol><li> Schalten Sie die LED-Lichtquelle ein und legen Sie einen 425 bis 505 nm Bandpassfilter über die Lichtquelle. </li><li> Mischen Sie 14,4 μl einer 100 bp DNA-Leiter und 1,6 μl SYBR Green mit einem Vortexer. </li><li> 4 μl Mischung in jede Vertiefung des Agarosegels im SGE-Chip geben ( Abbildung 2 ). </li><li> Setzen Sie die Elektrode in die beiden Bahnen des SGE-Chips. </li><li> Legen Sie einen 550 bis 700 nm Bandpassfilter über den SGE-Chip. </li><li> Schalten Sie die Stromquelle ein. Stellen Sie die elektrische Spannung auf 180 V (20 V / cm) ein. Schalte das Smartphone ein, um den DNA-Fragment-Trennprozess aufzuzeichnen (Abbildung 3 ). </li><li> Wenn die Elektrophorese 10 min später beendet ist, schalten Sie die Stromquelle und das LED-Licht aus. </li><li> Reinigen Sie den SGE-Chip. </li></ol>

<ol>
	<li>Carle, G. F., Olson, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+chromosomal+DNA+molecules+from+yeast+by+orthogonal-field-alternation+gel+electrophoresis.">Separation of chromosomal DNA molecules from yeast by orthogonal-field-alternation gel electrophoresis.</a> Nucleic. Acids. Res. 12 (14), 5647-5664 (1984).</li><li>McDonell, M. W., Simon, M. N., Studier, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+restriction+fragments+of+T7+DNA+and+determination+of+molecular+weights+by+electrophoresis+in+neutral+and+alkaline+gels.">Analysis of restriction fragments of T7 DNA and determination of molecular weights by electrophoresis in neutral and alkaline gels.</a> J. Mol. Biol. 110 (1), 119-146 (1977).</li><li>Fangman, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+very+large+DNA+molecules+by+gel+electrophoresis.">Separation of very large DNA molecules by gel electrophoresis.</a> Nucleic. Acids. Res. 5 (3), 653-665 (1978).</li><li>Blum, H., Beier, H., Gross, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+silver+staining+of+plant+proteins,+RNA+and+DNA+in+polyacrylamide+gels.">Improved silver staining of plant proteins, RNA and DNA in polyacrylamide gels.</a> Electrophoresis. 8 (2), 93-99 (1987).</li><li>G&#246;dde, R., 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=Electrophoresis+of+DNA+in+human+genetic+diagnostics-state-of-the-art,+alternatives+and+future+prospects.">Electrophoresis of DNA in human genetic diagnostics-state-of-the-art, alternatives and future prospects.</a> Electrophoresis. 27 (5-6), 939-946 (2006).</li><li>Studier, F. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+bacteriophage+T7+early+RNAs+and+proteins+on+slab+gels.">Analysis of bacteriophage T7 early RNAs and proteins on slab gels.</a> J. Mol. Biol. 79 (2), 237-248 (1973).</li><li>Sugden, B., De Troy, B., Roberts, R. J., 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=Agarose+slab-gel+electrophoresis+equipment.">Agarose slab-gel electrophoresis equipment.</a> Anal. Biochem. 68 (1), 36-46 (1975).</li><li>Rabilloud, T., Chevallet, M., Luche, S., Lelong, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+gel+electrophoresis+in+proteomics:+Past,+present+and+future.">Two-dimensional gel electrophoresis in proteomics: Past, present and future.</a> J. Proteomics. 73 (11), 2064-2077 (2010).</li><li>Lee, P. Y., Costumbrado, J., Hsu, C. Y., Kim, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agarose+gel+electrophoresis+for+the+separation+of+DNA+fragments.">Agarose gel electrophoresis for the separation of DNA fragments.</a> J. Vis. Exp. (62), e3923 (2012).</li><li>Gasser, R. B., 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=Single-strand+conformation+polymorphism+(SSCP)+for+the+analysis+of+genetic+variation.">Single-strand conformation polymorphism (SSCP) for the analysis of genetic variation.</a> Nat. Protoc. 1 (6), 3121-3128 (2006).</li><li>Matselyukh, B. P., Yarmoluk, S. M., Matselyukh, A. B., Kovalska, V. B., Kocheshev, I. O., Kryvorotenko, D. V., Lukashov, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+of+cyanine+dyes+with+nucleic+acids:+XXXI.+Using+of+polymethine+cyanine+dyes+for+the+visualization+of+DNA+in+agarose+gels.">Interaction of cyanine dyes with nucleic acids: XXXI. Using of polymethine cyanine dyes for the visualization of DNA in agarose gels.</a> J. Biochem. Biophys. Methods. 57 (1), 35-43 (2003).</li><li>Lunn, G., Sansone, E. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ethidium+bromide:+destruction+and+decontamination+of+solutions.">Ethidium bromide: destruction and decontamination of solutions.</a> Anal. Biochem. 162 (2), 453-458 (1987).</li><li>Li, Z., Liu, C., Zhang, D., Luo, S., Yamaguchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capillary+electrophoresis+of+RNA+in+hydroxyethylcellulose+polymer+with+various+molecular+weights.">Capillary electrophoresis of RNA in hydroxyethylcellulose polymer with various molecular weights.</a> J. Chormatogr. B. 1011, 114-120 (2016).</li><li>Li, Z., Liu, C., Ma, S., Zhang, D., Yamaguchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+inhibition+of+nucleic+acid+dyes+on+polymerase+chain+reaction+by+capillary+electrophoresis.">Analysis of the inhibition of nucleic acid dyes on polymerase chain reaction by capillary electrophoresis.</a> Anal. Methods-UK. 8 (11), 2330-2334 (2016).</li><li>Liu, F., 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=Developing+a+fluorescence-coupled+capillary+electrophoresis+based+method+to+probe+interactions+between+QDs+and+colorectal+cancer+targeting+peptides.">Developing a fluorescence-coupled capillary electrophoresis based method to probe interactions between QDs and colorectal cancer targeting peptides.</a> Electrophoresis. 37 (15-16), 2170-2174 (2016).</li><li>Wang, 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=A+capillary+electrophoresis+method+to+explore+the+self-assembly+of+a+novel+polypeptide+ligand+with+quantum+dots.">A capillary electrophoresis method to explore the self-assembly of a novel polypeptide ligand with quantum dots.</a> Electrophoresis. 37 (15-16), 2156-2162 (2016).</li><li>Miao, P., 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=Nuclease+assisted+target+recycling+and+spherical+nucleic+acids+gold+nanoparticles+recruitment+for+ultrasensitive+detection+of+microRNA.">Nuclease assisted target recycling and spherical nucleic acids gold nanoparticles recruitment for ultrasensitive detection of microRNA.</a> Electrochim. Acta. 190, 396-401 (2016).</li><li>Heller, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Principles+of+DNA+separation+with+capillary+electrophoresis.">Principles of DNA separation with capillary electrophoresis.</a> Electrophoresis. 22 (4), 629-643 (2001).</li></ol>

Es werden keine Interessenkonflikte deklariert.

Agarose-Gelelektrophorese wird weithin für die Trennung von DNA, RNA und Protein eingesetzt. Diese Arbeit schlägt eine neue Methode vor, um das traditionelle Gelelektrophoreseprotokoll zu ersetzen. Die Ergebnisse zeigen, dass 50, 100 und 1000 bp DNA-Leitern in einer so kleinen zusammengebauten Vorrichtung gut getrennt werden können. Der große Vorteil dieser Methode ist, dass man nicht nur die Nukleinsäuren mit wenig chemischem Verbrauch trennen kann, sondern auch den Trennprozess aufzeichnen kann. Obwohl die DNA-Fragmente in Fig. 2 breit aussehen, können die Ergebnisse verbessert werden, indem die Parameter des SGE-Chips und die Konzentration des Agarosegels optimiert werden. Weiterhin dauert der gesamte SGE-Prozess nicht mehr als 10 min, wenn im Chip vorgefertigte Gele verwendet werden. Die Trennleistung der DNA-Leiter ist ganz anders, wenn die Kanalbreite im Chip geändert wird. Zum Beispiel, wenn eine 1000-bp-DNA-Leiter getrennt ist, sieht die DNA-Band breiter aus, wennDie Breite des Kanals ist klein. Dies liegt möglicherweise daran, dass die Joule-Erwärmung im Agarosegel sehr hoch ist, was die Trennleistung beeinflusst. Die hier vorgeschlagene SGE-Methode ist sehr einfach. Ein portables Mini-SGE-Gerät kann entwickelt werden, wenn das System optimiert ist. Ein solches Gerät kann auf Point-of-Care Laboruntersuchungen angewendet werden.

<html> Die Plattengelelektrophorese (SGE) ist die effektivste Methode für die DNA-Fragmenttrennung 1 , 2 , 3 , 4 , 5 und gilt somit als vielseitiges Werkzeug in biochemischen und biologischen Analysen 6 , 7 , 8 . Allerdings zeigen viele Experimente, dass SGE durch die folgenden vier Probleme eingeschränkt wird: (1) die Trennungen dauern viele Stunden und sogar Tage; (2) der chemische verbrauch ist sehr hoch; (3) es erfordert eine komplizierte Apparatur ( z. B. 2D-Elektrophoresezelle, Elektrophorese-Stromversorgung und Gelbildgebungssystem); (4) Das Gelbildgebungssystem kann nur die abgetrennten DNA-Fragmente beobachten, wenn das Experiment beendet ist. Weiterhin wird Ethidiumbromid (EtBr), das üblicherweise in SGE 9 verwendet wird ,Ass = &quot;xref&quot;&gt; 10, ist mutagen und krebserregend 11 , 12 . So sollten Handschuhe bei der Übergabe von Gele mit EtBr getragen werden. Die Kapillarelektrophorese (CE) hat zahlreiche Vorteile 13 , 14 , 15 , 16 , 17 im Vergleich zu SGE, wie z. B. automatischer Betrieb, kurze Trennzeit und geringeren Verbrauch. Allerdings ist das CE-Instrument ziemlich teuer. Um diese Einschränkungen zu überwinden, wurde daher ein System entwickelt (Abbildung 1 ) für die Trennung von DNA. Ein solches System kann den Chemikalienverbrauch nicht nur stark reduzieren und die SGE-Experimentierzeit (&lt;8 min) speichern, sondern auch eine Echtzeit-Verfolgung des DNA-Trennprozesses im Agarosegel durch Smartphone durchführen. Durch die folgenden Verfahren in diesem Protokoll, Studenten schreienLd in der Lage sein, den SGE-Chip zu entwerfen und zu fertigen, das Agarosegel im Chip vorzubereiten, ein einfaches SGE-System mit einem Smartphone aufzustellen und den DNA-Migrationsprozess im Agarosegel aufzuzeichnen.

<table border="0" cellpadding="0" cellspacing="0" width="683">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">10&#215;TBE</td>
			<td style="width:287px;">Beijing Solarbio Science &#38; Technology Co., Ltd.</td>
			<td style="width:181px;">T1051</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">50bp DNA ladder</td>
			<td style="width:287px;">Takara Bio Inc.</td>
			<td style="width:181px;">3421A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">100bp DNA ladder</td>
			<td style="width:287px;">Takara Bio Inc.</td>
			<td style="width:181px;">3422A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">1kbp DNA ladder</td>
			<td style="width:287px;">Takara Bio Inc.</td>
			<td style="width:181px;">3426A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SYBR GREEN</td>
			<td style="width:287px;">Takara Bio Inc.</td>
			<td style="width:181px;">5760A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Agarose</td>
			<td style="width:287px;">Sigma-Aldrich Corporate</td>
			<td style="width:181px;">V900510</td>
		</tr>
	</tbody>
</table>

real-time tracking of dna fragment separation by smartphone

Die Plattengelelektrophorese (SGE) ist die häufigste Methode zur Trennung von DNA-Fragmenten; So wird es weitgehend auf das Gebiet der Biologie und andere angewendet. Allerdings ist das traditionelle SGE-Protokoll ziemlich langweilig, und das Experiment dauert lange. Darüber hinaus ist der Chemikalienverbrauch bei SGE-Experimenten sehr hoch. Diese Arbeit schlägt eine einfache Methode zur Trennung von DNA-Fragmenten auf Basis eines SGE-Chips vor. Der Chip wird von einer Graviermaschine hergestellt. Für die Anregungs- und Emissionswellenlängen des optischen Signals werden zwei Kunststoffplatten verwendet. Das Fluoreszenzsignal der DNA-Banden wird vom Smartphone gesammelt. Um diese Methode zu validieren, wurden 50, 100 und 1000 bp DNA-Leitern getrennt. Die Ergebnisse zeigen, dass eine DNA-Leiter kleiner als 5.000 bp innerhalb von 12 min aufgelöst werden kann und mit hoher Auflösung bei der Verwendung dieser Methode, was darauf hinweist, dass es ein idealer Ersatz für die traditionelle SGE-Methode ist.

<html> Fig. 4 , Fig. 5 und Fig. 6 stellen ein typisches Ergebnis nach der Gelelektrophorese von 50, 100 und 1000 bp DNA-Leitern dar. Nach dem Experiment waren die DNA-Fragmente gut getrennt. Weiterhin wurden die gleichen Proben in den 4 Kanälen des SGE-Chips getrennt, was zeigt, dass DNA-Fragmente gleicher Größe in jedem Experiment den gleichen Abstand bewegen. Die Trennleistung der DNA-Leiter kann durch Analysieren der Beziehung der Migrationsdistanz und des Logarithmus der DNA-Größe ausgewertet werden; Somit kann SGE auf die Berechnung der Grße unbekannter DNA-Fragmente angewendet werden. In Fig. 3 wurde festgestellt, daß der Migrationsabstand linear mit dem Logarithmus der DNA-Grße zusammenhängt, wenn die DNA-Grße kleiner als 700 bp ist. <html> Jpg &quot;/&gt; Abbildung 1 : Schematische und Bilder. ( A ) Ein schematisches Diagramm des Echtzeit-Tracking-DNA-Trennsystems. Es enthält das LED-Array als Lichtquelle, das optische Filter und den CGE-Chip. Das Smartphone kann den DNA-Migrationsprozess aufzeichnen. ( B ) Der SGE-Chip ( C ) Das Gerät für die Elektrophorese zusammengebaut. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig1large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a> <img alt="Figur 2" class="xfigimg" src="/files/ftp_upload/55926/55926fig2.jpg" /> Abbildung 2 : Ein Schüler lädt das Gel. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig2large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a> 5926fig3.jpg &quot;/&gt; Abbildung 3 : Ein Schüler, der die Migration auf einem Smartphone aufzeichnet. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig3large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a> <img alt="Abbildung 4" class="xfigimg" src="/files/ftp_upload/55926/55926fig4.jpg" /> Abbildung 4 : Trennung von 50-bp-DNA-Leitern auf den SGE-Chip. Die geometrischen Parameter für den Kanal im SGE-Chip sind 2,5 mm x 4,0 mm x 90 mm (Breite x Tiefe x Länge). Die Trennspannung beträgt 120 V. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig4large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a> <img alt="Abbildung 5" class="xfigimg" src="/files/ftp_upload/55926/55926fig5.jpg" /> Abbildung 5 : Trennung von 100-bp-DNA-Leitern auf den SGE-Chip. Die gEometrische Parameter für den Kanal im SGE-Chip sind 2,5 mm x 4,0 mm x 90 mm (Breite x Tiefe x Länge). Die Trennspannung beträgt 120 V. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig5large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a> <img alt="Abbildung 6" class="xfigimg" src="/files/ftp_upload/55926/55926fig6.jpg" /> Abbildung 6 : Trennung von 1000-bp-DNA-Leitern auf den SGE-Chip Die geometrischen Parameter für den Kanal im SGE-Chip sind 3,6 mm x 4,0 mm x 90 mm (Breite x Tiefe x Länge). Die Trennspannung beträgt 180 V. <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/55926/55926fig6large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieser Figur zu sehen.</a>

Watch this Scientific Journal Video about Real-time Tracking of DNA Fragment Separation by Smartphone at JoVE.com

Real-time Tracking of DNA Fragment Separation by Smartphone

Echtzeit-Tracking der DNA-Fragment-Trennung durch Smartphone

Traditionelle Plattengelelektrophorese (SGE) Experimente erfordern eine komplizierte Apparatur und einen hohen chemischen Verbrauch. Diese Arbeit stellt ein Protokoll vor, das eine kostengünstige Methode zur Trennung von DNA-Fragmenten innerhalb eines kurzen Zeitrahmens beschreibt.

Slab gel electrophoresis (SGE) is the most common method for the separation of DNA fragments; thus, it is broadly applied to the field of biology and ...

real-time-tracking-of-dna-fragment-separation-by-smartphone

Nanyang Technological University

Research

JoVE Journal

Biochemistry

14.4K Aufrufe.  University of Shanghai for Science and Technology.  Traditionelle Plattengelelektrophorese (SGE) Experimente erfordern eine komplizierte Apparatur und einen hohen chemischen Verbrauch. Diese Arbeit stellt ein Protokoll vor, das eine kostengünstige Methode zur Trennung von DNA-Fragmenten innerhalb eines kurzen Zeitrahmens beschreibt. 

Serie: Real-time Tracking of DNA Fragment Separation by Smartphone

DNA Polymerase Activity Assay Using Near-infrared Fluorescent Labeled DNA Visualized by Acrylamide Gel Electrophoresis

For any enzyme, robust, quantitative methods are required for characterization of both native and engineered enzymes. For DNA polymerases, DNA synthesis can be characterized using an in vitro DNA synthesis assay followed by polyacrylamide gel electrophoresis. The goal of this assay is to quantify synthesis of both natural DNA and modified DNA (M-DNA). These approaches are particularly useful for resolving oligonucleotides with single nucleotide resolution, enabling observation of individual steps during enzymatic oligonucleotide synthesis. These methods have been applied to the evaluation of an array of biochemical and biophysical properties such as the measurement of steady-state rate constants of individual steps of DNA synthesis, the error rate of DNA synthesis, and DNA binding affinity. By using modified components including, but not limited to, modified nucleoside triphosphates (NTP), M-DNA, and/or mutant DNA polymerases, the relative utility of substrate-DNA polymerase pairs can be effectively evaluated. Here, we detail the assay itself, including the changes that must be made to accommodate nontraditional primer DNA labeling strategies such as near-infrared fluorescently labeled DNA. Additionally, we have detailed crucial technical steps for acrylamide gel pouring and running, which can often be technically challenging.

This protocol describes the characterization of DNA polymerase synthesis of modified DNA through observation of changes to near-infrared fluorescently labeled DNA using gel electrophoresis and gel imaging. Acrylamide gels are used for high resolution imaging of the separation of short nucleic acids, which migrate at different rates depending on size.

DNA-Polymerase-Aktivität Assay mit Nahinfrarot-Leuchtstoff beschrifteten DNA durch Acrylamid Gelelektrophorese sichtbar gemacht

For any enzyme, robust, quantitative methods are required for characterization of both native and engineered enzymes. For DNA polymerases, DNA synthesis ...

Forschung

Biochemie

Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability to provide more dynamic information about cells under physiological conditions than classical biochemical assays, this label-free real-time cell assay based on the electric impedance principle is attracting more attention during the past decade. However, its practical utilization may be limited due to the relatively expensive cost of measurement, in which costly consumable disposable gold microchips are used for the cell analyzer. In this protocol, we have developed a general strategy to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step. The proposed method has been tested and shown to be effective for the regeneration and repeated usage of commercial electronic plates at least three times, which will help researchers save on the high running cost of real-time cell assays.

This protocol describes a general strategy to regenerate commercial arrayed gold microelectrodes equipped for a label-free cell analyzer aimed at saving on the high running costs ofmicrochip-based assays. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step, which enables repeated usage of microchips.

Regeneration der angeordneten Gold Mikroelektroden ausgestattet für eine Echtzeit-Zelle-Analyzer

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability ...

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

The DNA strand exchange reaction mediated by Rad51 is a critical step of homologous recombination. In this reaction, Rad51 forms a nucleoprotein filament on single-stranded DNA (ssDNA) and captures double-stranded DNA (dsDNA) non-specifically to interrogate it for a homologous sequence. After encountering homology, Rad51 catalyzes DNA strand exchange to mediate pairing of the ssDNA with the complementary strand of the dsDNA. This reaction is highly regulated by numerous accessary proteins in vivo. Although conventional biochemical assays have been successfully employed to examine the role of such accessory protein in vitro, kinetic analysis of intermediate formation and its progression into a final product has proven challenging due to the unstable and transient nature of the reaction intermediates. To observe these reaction steps directly in solution, fluorescence resonance energy transfer (FRET)-based real-time observation systems of this reaction were established. Kinetic analysis of real-time observations shows that the DNA strand exchange reaction mediated by Rad51 obeys a three-step reaction model involving the formation of a three-strand DNA intermediate, maturation of this intermediate, and the release of ssDNA from the mature intermediate. The Swi5-Sfr1 complex, an accessary protein conserved in eukaryotes, strongly enhances the second and third steps of this reaction. The FRET-based assays presented here enable us to uncover the molecular mechanisms through which recombination accessary proteins stimulate the DNA strand exchange activity of Rad51. The primary goal of this protocol is to enhance the repertoire of techniques available to researchers in the field of homologous recombination, particularly those working with proteins from species other than Schizosaccharomyces pombe, so that the evolutionary conservation of the findings presented herein can be determined.

Fluorescence resonance energy transfer-based real-time observation systems of the DNA strand exchange reaction mediated by Rad51 were developed. Using the protocols presented here, we are able to detect the formation of reaction intermediates and their conversion into products, while also analyzing the enzymatic kinetics of the reaction.

Echtzeit-Beobachtung der DNA-Strang Exchange Reaktion vermittelt durch Rad51

The DNA strand exchange reaction mediated by Rad51 is a critical step of homologous recombination. In this reaction, Rad51 forms a nucleoprotein filament ...

DNA Sequence Recognition by DNA Primase Using High-Throughput Primase Profiling

DNA primase synthesizes short RNA primers that initiate DNA synthesis of Okazaki fragments on the lagging strand by DNA polymerase during DNA replication. The binding of prokaryotic DnaG-like primases to DNA occurs at a specific trinucleotide recognition sequence. It is a pivotal step in the formation of Okazaki fragments. Conventional biochemical tools that are used to determine the DNA recognition sequence of DNA primase provide only limited information. Using a high-throughput microarray-based binding assay and consecutive biochemical analyses, it has been shown that 1) the specific binding context (flanking sequences of the recognition site) influences the binding strength of the DNA primase to its template DNA, and 2) stronger binding of primase to the DNA yields longer RNA primers, indicating higher processivity of the enzyme. This method combines PBM and primase activity assay and is designated as high-throughput primase profiling (HTPP), and it allows characterization of specific sequence recognition by DNA primase in unprecedented time and scalability.&#160;

Protein binding microarray (PBM) experiments combined with biochemical assays link the binding and catalytic properties of DNA primase, an enzyme that synthesizes RNA primers on template DNA. This method, designated as high-throughput primase profiling (HTPP), can be used to reveal DNA-binding patterns of a variety of enzymes.

DNA-Sequenzerkennung durch DNA-Primase mit High-Throughput Primase Profiling

DNA primase synthesizes short RNA primers that initiate DNA synthesis of Okazaki fragments on the lagging strand by DNA polymerase during DNA replication. ...

Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells

In recent years, the importance of mucosal surface pH in the airways has been highlighted by its ability to regulate airway surface liquid (ASL) hydration, mucus viscosity and activity of antimicrobial peptides, key parameters involved in innate defense of the lungs. This is of primary relevance in the field of chronic respiratory diseases such as cystic fibrosis (CF) where these parameters are dysregulated. While different groups have studied ASL pH both in vivo and in vitro, their methods report a relatively wide range of ASL pH values and even contradictory findings regarding any pH differences between non-CF and CF cells. Furthermore, their protocols do not always provide enough details in order to ensure reproducibility, most are low throughput and require expensive equipment or specialized knowledge to implement, making them difficult to establish in most labs. Here we describe a semi-automated fluorescent plate reader assay that enables the real-time measurement of ASL pH under thin film conditions that more closely resemble the in vivo situation. This technique allows for stable measurements for many hours from multiple airway cultures simultaneously and, importantly, dynamic changes in ASL pH in response to agonists and inhibitors can be monitored. To achieve this, the ASL of fully differentiated primary human airway epithelial cells (hAECs) are stained overnight with a pH-sensitive dye in order to allow for the reabsorption of the excess fluid to ensure thin film conditions. After fluorescence is monitored in the presence or absence of agonists, pH calibration is performed in situ to correct for volume and dye concentration. The method described provides the required controls to make stable and reproducible ASL pH measurements, which ultimately could be used as a drug discovery platform for personalized medicine, as well as adapted to other epithelial tissues and experimental conditions, such as inflammatory and/or host-pathogen models.

We present a protocol to make dynamic measurements of the airway surface liquid pH under thin film conditions using a plate-reader.

Real-Time, halbautomatisierte Fluoreszenzmessung der Luftbogenoberfläche Liquid pH der primären menschlichen Luftweg-Epithelzellen

In recent years, the importance of mucosal surface pH in the airways has been highlighted by its ability to regulate airway surface liquid (ASL) ...

Monitoring GPCR-&#946;-arrestin1/2 Interactions in Real Time Living Systems to Accelerate Drug Discovery

Interactions between G-protein coupled receptors (GPCRs) and &#946;-arrestins are vital processes with physiological implications of great importance. Currently, the characterization of novel drugs towards their interactions with &#946;-arrestins and other cytosolic proteins is extremely valuable in the field of GPCR drug discovery particularly during the study of GPCR biased agonism. Here, we show the application of a novel structural complementation assay to accurately monitor receptor-&#946;-arrestin interactions in real time living systems. This method is simple, accurate and can be easily extended to any GPCR of interest and also it has the advantage that it overcomes unspecific interactions due to the presence of a low expression promoter present in each vector system. This structural complementation assay provides key features that allow an accurate and precise monitoring of receptor-&#946;-arrestin interactions, making it suitable in the study of biased agonism of any GPCR system as well as GPCR c-terminus &#8216;phosphorylation codes&#8217; written by different GPCR-kinases (GRKs) and post-translational modifications of arrestins that stabilize or destabilize the receptor-&#946;-arrestin complex.

GPCR-&#946;-arrestin interactions are an emerging field in GPCR drug discovery. Accurate, precise and easy to set up methods are necessary to monitor such interactions in living systems. We show a structural complementation assay to monitor GPCR-&#946;-arrestin interactions in real time living cells, and it can be extended to any GPCR.

Überwachung von GPCR---Arrestin1/2-Interaktionen in Echtzeit-Lebenssystemen zur Beschleunigung der Arzneimittelentdeckung

Interactions between G-protein coupled receptors (GPCRs) and &#946;-arrestins are vital processes with physiological implications of great importance. ...

Measuring Nucleotide Binding to Intact, Functional Membrane Proteins in Real Time

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. This method combines expression of proteins tagged with the fluorescent non-canonical amino acid ANAP, and FRET between ANAP and fluorescent (trinitrophenyl) nucleotide derivatives. We present examples of nucleotide binding to ANAP-tagged KATP ion channels measured in unroofed plasma membranes and excised, inside-out membrane patches under voltage clamp. The latter allows for simultaneous measurements of ligand binding and channel current, a direct readout of protein function. Data treatment and analysis are discussed extensively, along with potential pitfalls and artefacts. This method provides rich mechanistic insights into the ligand-dependent gating of KATP channels and can readily be adapted to the study of other nucleotide-regulated proteins or any receptor for which a suitable fluorescent ligand can be identified.

This protocol presents a method for measuring adenine nucleotide binding to receptors in real time in a cellular environment. Binding is measured as F&#246;rster resonance energy transfer (FRET) between trinitrophenyl nucleotide derivatives and protein labeled with a non-canonical, fluorescent amino acid.

Messung der Nukleotidbindung an intakte, funktionelle Membranproteine in Echtzeit

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. ...

Enabling Real-Time Compensation in Fast Photochemical Oxidations of Proteins for the Determination of Protein Topography Changes

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area of proteins. This technique relies on the reaction of amino acid side chains with hydroxyl radicals freely diffusing in solution. FPOP generates these radicals in situ by laser photolysis of hydrogen peroxide, creating a burst of hydroxyl radicals that is depleted on the order of a microsecond. When these hydroxyl radicals react with a solvent-accessible amino acid side chain, the reaction products exhibit a mass shift that can be measured and quantified by mass spectrometry. Since the rate of reaction of an amino acid depends in part on the average solvent accessible surface of that amino acid, measured changes in the amount of oxidation of a given region of a protein can be directly correlated to changes in the solvent accessibility of that region between different conformations (e.g., ligand-bound versus ligand-free, monomer vs. aggregate, etc.) FPOP has been applied in a number of problems in biology, including protein-protein interactions, protein conformational changes, and protein-ligand binding. As the available concentration of hydroxyl radicals varies based on many experimental conditions in the FPOP experiment, it is important to monitor the effective radical dose to which the protein analyte is exposed. This monitoring is efficiently achieved by incorporating an inline dosimeter to measure the signal from the FPOP reaction, with laser fluence adjusted in real-time to achieve the desired amount of oxidation. With this compensation, changes in protein topography reflecting conformational changes, ligand-binding surfaces, and/or protein-protein interaction interfaces can be determined in heterogeneous samples using relatively low sample amounts.

Fast photochemical oxidation of proteins is an emerging technique for the structural characterization of proteins. Different solvent additives and ligands have varied hydroxyl radical scavenging properties. To compare the protein structure in different conditions, real-time compensation of hydroxyl radicals generated in the reaction is required to normalize reaction conditions.

Ermöglicht Echtzeitkompensation bei schnellen photochemischen Oxidationen von Proteinen zur Bestimmung von Proteintopographie-Änderungen

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area ...

Workflow and Tools for Crystallographic Fragment Screening at the Helmholtz-Zentrum Berlin

Fragment screening is a technique that helps to identify promising starting points for ligand design. Given that crystals of the target protein are available and display reproducibly high-resolution X-ray diffraction properties, crystallography is among the most preferred methods for fragment screening because of its sensitivity. Additionally, it is the only method providing detailed 3D information of the binding mode of the fragment, which is vital for subsequent rational compound evolution. The routine use of the method depends on the availability of suitable fragment libraries, dedicated means to handle large numbers of samples, state-of-the-art synchrotron beamlines for fast diffraction measurements and largely automated solutions for the analysis of the results.
Here, the complete practical workflow and the included tools on how to conduct crystallographic fragment screening (CFS) at the Helmholtz-Zentrum Berlin (HZB) are presented. Preceding this workflow, crystal soaking conditions as well as data collection strategies are optimized for reproducible crystallographic experiments. Then, typically in a one to two-day procedure, a 96-membered CFS-focused library provided as dried ready-to-use plates is employed to soak 192 crystals, which are then flash-cooled individually. The final diffraction experiments can be performed within one day at the robot-mounting supported beamlines BL14.1 and BL14.2 at the BESSY&#160; II electron storage ring operated by the HZB in Berlin-Adlershof (Germany). Processing of the crystallographic data, refinement of the protein structures, and hit identification is fast and largely automated using specialized software pipelines on dedicated servers, requiring little user input.
Using the CFS workflow at the HZB enables routine screening experiments. It increases the chances for successful identification of fragment hits as starting points to develop more potent binders, useful for pharmacological or biochemical applications.

Crystallographic fragment screening at the Helmholtz-Zentrum Berlin is performed using a workflow with dedicated compound libraries, crystal handling tools, fast data collection facilities&#160;and largely automated data analysis. The presented protocol intends to maximize the output of such experiments to provide promising starting points for downstream structure-based ligand design.

Workflow und Tools für das kristallographische Fragmentscreening am Helmholtz-Zentrum Berlin

Fragment screening is a technique that helps to identify promising starting points for ligand design. Given that crystals of the target protein are ...

Deciphering Molecular Mechanism of Histone Assembly by DNA Curtain Technique

Chromatin is a higher-order structure that packages eukaryotic DNA. Chromatin undergoes dynamic alterations according to the cell cycle phase and in response to environmental stimuli. These changes are essential for genomic integrity, epigenetic regulation, and DNA metabolic reactions such as replication, transcription, and repair. Chromatin assembly is crucial for chromatin dynamics and is catalyzed by histone chaperones. Despite extensive studies, the mechanisms by which histone chaperones enable chromatin assembly remains elusive. Moreover, the global features of nucleosomes organized by histone chaperones are poorly understood. To address these problems, this work describes a unique single-molecule imaging technique named DNA curtain, which facilitates the investigation of the molecular details of nucleosome assembly by histone chaperones. DNA curtain is a hybrid technique that combines lipid fluidity, microfluidics, and total internal reflection fluorescence microscopy (TIRFM) to provide a universal platform for real-time imaging of diverse protein-DNA interactions.Using DNA curtain, the histone chaperone function of Abo1, the Schizosaccharomyces pombe bromodomain-containing AAA+ ATPase, is investigated, and the molecular mechanism underlying histone assembly of Abo1 is revealed. DNA curtain provides a unique approach for studying chromatin dynamics.

DNA curtain, a high-throughput single-molecule imaging technique, provides a platform for real-time visualization of diverse protein-DNA interactions. The present protocol utilizes the DNA curtain technique to investigate the biological role and molecular mechanism of Abo1, a Schizosaccharomyces pombe bromodomain-containing AAA+ ATPase.

Entschlüsselung des molekularen Mechanismus der Histonassemblierung mittels DNA-Vorhangtechnik

Chromatin is a higher-order structure that packages eukaryotic DNA. Chromatin undergoes dynamic alterations according to the cell cycle phase and in ...