Este trabajo fue apoyado por el Proyecto Estratégico de Subvenciones y descubrimiento de JDN de las Ciencias Naturales e Ingeniería de Investigación de Canadá (NSERC).

<ol>
	<li>Neufeld, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+stable-isotope+probing.">DNA stable-isotope probing.</a> Nat. Protocols. 2, 860-866 (2007).</li><li>Neufeld, J. D., Boden, R., Moussard, H., Sch&#228;fer, H., Murrell, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Substrate-specific+clades+of+active+marine+methylotrophs+associated+with+a+phytoplankton+bloom+in+a+temperate+coastal+environment.">Substrate-specific clades of active marine methylotrophs associated with a phytoplankton bloom in a temperate coastal environment.</a> Appl. Environ. Microbiol. 74, 7321-7328 (2009).</li><li>Nercessian, O., Noyes, E., Kalyuzhnaya, M. G., Lidstrom, M. E., Chistoserdova, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+populations+active+in+metabolism+of+C1+compounds+in+the+sediment+of+Lake+Washington,+a+freshwater+lake.">Bacterial populations active in metabolism of C1 compounds in the sediment of Lake Washington, a freshwater lake.</a> Appl. Environ. Microbiol. 71, 6885-6899 (2005).</li><li>Padmanabhan, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Respiration+of+13C-labelled+substrates+added+to+soil+in+the+field+and+subsequent+16S+rRNA+gene+analysis+of+13C-labelled+soil+DNA.">Respiration of 13C-labelled substrates added to soil in the field and subsequent 16S rRNA gene analysis of 13C-labelled soil DNA.</a> Appl. Environ. Microbiol. 69, 1614-1622 (2003).</li><li>Bernard, 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+and+identification+of+soil+microbial+populations+actively+assimilating+carbon+from+13C-labelled+wheat+residue+as+estimated+by+DNA-+and+RNA-SIP+techniques.">Dynamics and identification of soil microbial populations actively assimilating carbon from 13C-labelled wheat residue as estimated by DNA- and RNA-SIP techniques.</a> Environ. Microbiol. 9, 752-764 (2007).</li><li>Haichar, e. l. Z. a. h. a. r., F, . <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+cellulolytic+bacteria+in+soil+by+stable+isotope+probing.">Identification of cellulolytic bacteria in soil by stable isotope probing.</a> Environ. Microbiol. 9, 625-634 (2007).</li><li>Addison, S., McDonald, I., Lloyd-Jones, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+isotope+probing:+Technical+considerations+when+resolving+15N-labelled+RNA+in+gradients.">Stable isotope probing: Technical considerations when resolving 15N-labelled RNA in gradients.</a> J. Microbiol. Meth. 80, 70-75 (2009).</li><li>Buckley, D. H., Huangyutitham, V., Hsu, S. -. F., Nelson, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+isotope+probing+with+15N+achieved+by+disentangling+the+effects+of+genome+G+++C+content+and+isotope+enrichment+on+DNA+density.">Stable isotope probing with 15N achieved by disentangling the effects of genome G + C content and isotope enrichment on DNA density.</a> Appl. Environ. Microbiol. 73, 3189-3195 (2007).</li><li>Schwartz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+growing+microorganisms+in+soil+by+stable+isotope+probing+with+H218O.">Characterization of growing microorganisms in soil by stable isotope probing with H218O.</a> Appl. Environ. Microbiol. 73, 2541-2546 (2007).</li><li>Neufeld, J. D., Dumont, M. G., Vohra, J., Murrell, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methodological+considerations+for+the+use+of+stable+isotope+probing+in+microbial+ecology.">Methodological considerations for the use of stable isotope probing in microbial ecology.</a> Microb. Ecol. 53, 435-442 (2007).</li><li>Martineau, C., Whyte, L., Greer, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+SYBR+safe+technique+for+the+sensitive+detection+of+DNA+in+cesium+chloride+density+gradients+for+stable+isotope+probing+assays.">Development of a SYBR safe technique for the sensitive detection of DNA in cesium chloride density gradients for stable isotope probing assays.</a> J. Microbiol. Meth. 73, 199-202 (2008).</li><li>Bartram, A. K., Poon, C., Neufeld, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleic+acid+contamination+of+glycogen+used+in+nucleic+acid+precipitation+and+assessment+of+linear+polyacrylamide+as+an+alternative+co-precipitant.">Nucleic acid contamination of glycogen used in nucleic acid precipitation and assessment of linear polyacrylamide as an alternative co-precipitant.</a> Biotechniques. 47, 1019-1022 (2009).</li><li>Chen, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Revealing+the+uncultivated+majority:+combining+DNA+stable-isotope+probing,+multiple+displacement+amplification+and+metagenomic+analyses+of+uncultivated+Methylocystis+in+acidic+peatlands.">Revealing the uncultivated majority: combining DNA stable-isotope probing, multiple displacement amplification and metagenomic analyses of uncultivated Methylocystis in acidic peatlands.</a> Environ. Microbiol. 10, 2609-2622 (2008).</li><li>Neufeld, J. D., Chen, Y., Dumont, M. G., Murrell, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Marine+methylotrophs+revealed+by+stable-isotope+probing,+multiple+displacement+amplification+and+metagenomics.">Marine methylotrophs revealed by stable-isotope probing, multiple displacement amplification and metagenomics.</a> Environ. Microbiol. 10, 1526-1535 (2008).</li><li>Kalyuzhnaya, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+metagenomics+targets+specific+functional+types+in+complex+microbial+communities.">High-resolution metagenomics targets specific functional types in complex microbial communities.</a> Nat. Biotechnol. 26, 1029-1034 (2008).</li><li>Binga, E. K., Lasken, R. S., Neufeld, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Something+from+(almost)+nothing:+the+impact+of+multiple+displacement+amplification+on+microbial+ecology.">Something from (almost) nothing: the impact of multiple displacement amplification on microbial ecology.</a> ISME J. 2, 233-241 (2008).</li><li>Green, S. J., Leigh, M. B., Neufeld, J. D., Timmis, K. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Microbiology of Hydrocarbon and Lipid Microbiology. , 4137-4158 (2010).</li><li>Neufeld, J. D., Wagner, M., Murrell, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Who+eats+what,+where+and+when?+Isotope-labelling+experiments+are+coming+of+age.">Who eats what, where and when? Isotope-labelling experiments are coming of age.</a> ISME J. 1, 103-110 (2007).</li><li>Gallagher, E., McGuinness, L., Phelps, C., Young, L. Y., Kerkhof, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+shortens+the+incubation+time+needed+to+detect+benzoate-utilizing+denitrifying+bacteria+by+stable-isotope+probing.">DNA shortens the incubation time needed to detect benzoate-utilizing denitrifying bacteria by stable-isotope probing.</a> Appl. Environ. Microbiol. 71, 5192-5196 .</li></ol>

El diseño apropiado de isótopos estables experimentos de sondeo es de importancia crítica para la obtención de ADN marcado por encima de la comunidad de fondo sin etiquetar. Consideraciones relacionadas con la muestra de los tiempos de incubación, las concentraciones de sustrato, las condiciones de incubación (por ejemplo nutrientes, contenido de humedad del suelo), cruzar la alimentación y la replicación se han discutido en otros lugares 10,18 y se recomienda al lector consultar estas publicaciones e...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Bromophenol Blue</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>BP115-25</td>
<td>&nbsp;</td>
<tr>
<td>Cesium chloride</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>BP210-500</td>
<td>&nbsp;</td>
<tr>
<td>Ethanol, reagent grade</td>
<td>Reagent</td>
<td>Sigma-Aldrich</td>
<td>652261</td>
<td>&nbsp;</td>
<tr>
<td>Ethidium bromide</td>
<td>Reagent</td>
<td>Sigma-Aldrich</td>
<td>E1510</td>
<td>&nbsp;</td>
<tr>
<td>Hydrochloric acid</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>351285212</td>
<td>&nbsp;</td>
<tr>
<td>Linear polyacrylamide</td>
<td>Reagent</td>
<td>Applichem</td>
<td>A6587</td>
<td>&nbsp;</td>
<tr>
<td>Polyethylene Glycol 6000</td>
<td>Reagent</td>
<td>VWR</td>
<td>CAPX1286L-4</td>
<td>&nbsp;</td>
<tr>
<td>Potassium Chloride</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>AC42409-0010</td>
<td>&nbsp;</td>
<tr>
<td>Sodium Chloride</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>S2711</td>
<td>&nbsp;</td>
<tr>
<td>Sodium Hydroxide pellets</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>S3181</td>
<td>&nbsp;</td>
<tr>
<td>Tris base</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>BP1521</td>
<td>&nbsp;</td>
<tr>
<td>Dark Reader</td>
<td>Equipment</td>
<td>Clare Chemical</td>
<td>DR46B</td>
<td>&nbsp;</td>
<tr>
<td>Microcentrifuge</td>
<td>Equipment</td>
<td>Eppendorf</td>
<td>5424 000.410</td>
<td>&nbsp;</td>
<tr>
<td>Nanodrop 2000</td>
<td>Equipment</td>
<td>Fisher Scientific</td>
<td>361013650</td>
<td>&nbsp;</td>
<tr>
<td>Infusion pump</td>
<td>Equipment</td>
<td>Braintree Scientific</td>
<td>N/A</td>
<td>Model Number: BSP 
See <a href="http://www.braintreesci.com">www.braintreesci.com</a> for ordering details.</td>
</tr>
<tr>
<td>Tube sealer</td>
<td>Equipment</td>
<td>Beckman-Coulter</td>
<td>358312</td>
<td>&nbsp;</td>
<tr>
<td>Ultracentrifuge</td>
<td>Equipment</td>
<td>Beckman-Coulter</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Ultracentrifuge rotor</td>
<td>Equipment</td>
<td>Beckman-Coulter</td>
<td>362754</td>
<td>&nbsp;</td>
<tr>
<td>Ultraviolet light source</td>
<td>Equipment</td>
<td>UVP Inc. </td>
<td>95-0017-09</td>
<td>Any UV source will suffice</td>
</tr>
<tr>
<td>Ultraviolet light face shield</td>
<td>Equipment</td>
<td>Fisher Scientific</td>
<td>114051C</td>
<td>&nbsp;</td>
<tr>
<td>Butyl rubber stoppers, gray</td>
<td>Material</td>
<td>Sigma-Aldrich</td>
<td>27232</td>
<td>&nbsp;</td>
<tr>
<td>Centrifuge tubes</td>
<td>Material</td>
<td>Beckman-Coulter</td>
<td>342412</td>
<td>&nbsp;</td>
<tr>
<td>Hypodermic needle, 23 gauge, 2&#x201D; length</td>
<td>Material</td>
<td>BD</td>
<td>305145</td>
<td>&nbsp;</td>
<tr>
<td>Microfuge tubes, 1.5 mL</td>
<td>Material</td>
<td>DiaMed</td>
<td>AD151-N500</td>
<td>&nbsp;</td>
<tr>
<td>Open center seals, 20 mm diameter</td>
<td>Material</td>
<td>Sigma-Aldrich</td>
<td>27230-U</td>
<td>&nbsp;</td>
<tr>
<td>Pasteur pipettes, glass</td>
<td>Material</td>
<td>Fisher Scientific</td>
<td>13-678-6C</td>
<td>&nbsp;</td>
<tr>
<td>Pipet tips</td>
<td>Material</td>
<td>DiaMed</td>
<td>BPS340-1000 </td>
<td>Catalogue number is for 200 &mu;l tips. 10 or 20 &mu;l tips may be purchased from the same source</td>
</tr>
<tr>
<td>Pump tubing 1.5 mm bore x 1.5 mm wall</td>
<td>Material</td>
<td>Appleton Woods</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Screw-cap tubes, 15 mL</td>
<td>Material</td>
<td>DiaMed</td>
<td>AD15MLP-S </td>
<td>&nbsp;</td>
<tr>
<td>Serum vials, 125 mL volume</td>
<td>Material</td>
<td>Sigma-Aldrich</td>
<td>Z114014</td>
<td>&nbsp;</td>
<tr>
<td>Syringe, 60 mL</td>
<td>Material</td>
<td>BD</td>
<td>309653</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

dna stable-isotope probing (dna-sip)

ADN de isótopos estables de sondeo (ADN-SIP) es una poderosa técnica para la identificación de microorganismos activos que asimilar ciertos sustratos de carbono y nutrientes en la biomasa celular. Como tal, esta técnica de cultivo-independiente ha sido una importante metodología para la asignación de la función metabólica de las diversas comunidades que habitan en una amplia gama de ambientes terrestres y acuáticos. Después de la incubación de una muestra ambiental con isótopos estables compuestos marcados, el ácido nucleico extraído se somete a ultracentrifugación en gradiente de densidad y el fraccionamiento del gradiente posteriores para separar los ácidos nucleicos de diferentes densidades. La purificación del ADN a partir de cloruro de cesio recupera no marcado y marcado de ADN para posterior caracterización molecular (por ejemplo, huellas dactilares, microarrays, bibliotecas clon, la metagenómica). Este protocolo de vídeo JoVe proporciona visuales paso a paso las explicaciones del protocolo de gradiente de densidad gradiente de fraccionamiento de ultracentrifugación, y la recuperación de ADN marcado. El protocolo también incluye la muestra de datos SIP y pone de relieve importantes consejos y precauciones que se deben considerar para asegurar el éxito de ADN-SIP análisis.

Watch this Scientific Journal Video about DNA Stable-Isotope Probing DNA-SIP at JoVE.com

DNA Stable-Isotope Probing DNA-SIP

ADN de isótopos estables de sondeo es un método de cultivo independiente para identificar y caracterizar las comunidades activas de microorganismos que son capaces de utilizar sustratos específicos. Asimilación de sustrato enriquecido en los isótopos pesados ​​lleva a la incorporación de los átomos marcados en la biomasa microbiana. Ultracentrifugación en gradiente de densidad recupera la etiqueta de ADN para posterior análisis molecular.

ADN de isótopos estables de palpado (ADN-SIP)

DNA stable-isotope probing (DNA-SIP) is a powerful technique for identifying active microorganisms that assimilate particular carbon substrates and ...

Research

JoVE Journal

Biology

DNA Stable-Isotope Probing (DNA-SIP)

43.9K vistas.  University of Waterloo. ADN de isótopos estables de sondeo es un método de cultivo independiente para identificar y caracterizar las comunidades activas de microorganismos que son capaces de utilizar sustratos específicos. Asimilación de sustrato enriquecido en los isótopos pesados ​​lleva a la incorporación de los átomos marcados en la biomasa microbiana. Ultracentrifugación en gradiente de densidad recupera la etiqueta de ADN para posterior análisis molecular.

Video: DNA Stable-Isotope Probing DNA-SIP

Probing for Mitochondrial Complex Activity in Human Embryonic Stem Cells

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and programmed cell death. Mitochondria produce ATP, regulate the cytoplasmic redox state and Ca2+ balance, catabolize fatty acids, synthesize heme, nucleotides, steroid hormones, amino acids, and help assemble iron-sulfur clusters in proteins. Mitochondria also have an essential role in heat production. Mutations of the mitochondrial genome cause several types of human disorder. The accumulation of mtDNA mutations correlates with aging and is suspected to have an important role in the development of cancer. Due to their vitally important role in all cell types, the function of mitochondria must also be critical for stem cells. Key advances have been made in our understanding of stem cell viability, proliferation, and differentiation capacity. But the functional activity of stem cells, in particular their energy status, was not yet been studied in detail. Almost nothing is known about the mitochondrial properties of human embryonic stem cells (hESCs) and their differentiated precursor progeny. One way to understand and evaluate the role of mitochondria in hESC function and developmental potential is to directly measure the activity of mitochondrial respiratory complexes. Here, we describe high resolution clear native gel electrophoresis and subsequent in gel activity visualization as a method for analyzing the five respiratory chain complexes of hESCs.

In this video, we will show you how the mitochondrial respiratory chain complexes of human embryonic stem cells can be analyzed using in gel activity assays.

Sondeo de la actividad mitocondrial complejo en células estaminales embrionarias humanas

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and ...

Investigación

Biología

Methylated DNA Immunoprecipitation

The identification of DNA methylation patterns is a common procedure in the study of epigenetics, as methylation is known to have significant effects on gene expression, and is involved with normal development as well as disease 1-4. Thus, the ability to discriminate between methylated DNA and non-methylated DNA is essential for generating methylation profiles for such studies. Methylated DNA immunoprecipitation (MeDIP) is an efficient technique for the extraction of methylated DNA from a sample of interest 5-7. A sample of as little as 200 ng of DNA is sufficient for the antibody, or immunoprecipitation (IP), reaction. DNA is sonicated into fragments ranging in size from 300-1000 bp, and is divided into immunoprecipitated (IP) and input (IN) portions. IP DNA is subsequently heat denatured and then incubated with anti-5'mC, allowing the monoclonal antibody to bind methylated DNA. After this, magnetic beads containing a secondary antibody with affinity for the primary antibody are added, and incubated. These bead-linked antibodies will bind the monoclonal antibody used in the first step. DNA bound to the antibody complex (methylated DNA) is separated from the rest of the DNA by using a magnet to pull the complexes out of solution. Several washes using IP buffer are then performed to remove the unbound, non-methylated DNA. The methylated DNA/antibody complexes are then digested with Proteinase K to digest the antibodies leaving only the methylated DNA intact. The enriched DNA is purified by phenol:chloroform extraction to remove the protein matter and then precipitated and resuspended in water for later use. PCR techniques can be used to validate the efficiency of the MeDIP procedure by analyzing the amplification products of IP and IN DNA for regions known to lack and known to contain methylated sequences. The purified methylated DNA can then be used for locus-specific (PCR) or genome-wide (microarray and sequencing) methylation studies, and is particularly useful when applied in conjunction with other research tools such as gene expression profiling and array comparative genome hybridization (CGH) 8. Further investigation into DNA methylation will lead to the discovery of new epigenetic targets, which in turn, may be useful in developing new therapeutic or prognostic research tools for diseases such as cancer that are characterized by aberrantly methylated DNA 2, 4, 9-11.

This video demonstrates the protocol for methylated DNA immunoprecipitation (MeDIP). MeDIP is a two day procedure that selectively extracts methylated DNA fragments from a genomic DNA sample using antibodies with specificity for 5 -methylcytosine (anti-5 mC).

Inmunoprecipitación de ADN metilado

The identification of DNA methylation patterns is a common procedure in the study of epigenetics, as methylation is known to have significant effects on ...

Direct Observation of Enzymes Replicating DNA Using a Single-molecule DNA Stretching Assay

We describe a method for observing real time replication of individual DNA molecules mediated by proteins of the bacteriophage replication system. Linearized &lambda; DNA is modified to have a biotin on the end of one strand, and a digoxigenin moiety on the other end of the same strand. The biotinylated end is attached to a functionalized glass coverslip and the digoxigeninated end to a small bead. The assembly of these DNA-bead tethers on the surface of a flow cell allows a laminar flow to be applied to exert a drag force on the bead. As a result, the DNA is stretched close to and parallel to the surface of the coverslip at a force that is determined by the flow rate (Figure 1). The length of the DNA is measured by monitoring the position of the bead. Length differences between single- and double-stranded DNA are utilized to obtain real-time information on the activity of the replication proteins at the fork. Measuring the position of the bead allows precise determination of the rates and processivities of DNA unwinding and polymerization (Figure 2).

We describe a method for observing real time replication of individual DNA molecules mediated by proteins of the bacteriophage replication system.

La observación directa de ADN Enzimas Replicar El uso de un ADN de una sola molécula de estiramiento de ensayo

We describe a method for observing real time replication of individual DNA molecules mediated by proteins of the bacteriophage replication system. ...

Electroeluting DNA Fragments

Purified DNA fragments are used for different purposes in Molecular Biology and they can be prepared by several procedures. Most of them require a previous electrophoresis of the DNA fragments in order to separate the band of interest. Then, this band is excised out from an agarose or acrylamide gel and purified by using either: binding and elution from glass or silica particles, DEAE-cellulose membranes, "crush and soak method", electroelution or very often expensive commercial purification kits. Thus, selecting a method will depend mostly of what is available in the laboratory. The electroelution procedure allows one to purify very clean DNA to be used in a large number of applications (sequencing, radiolabeling, enzymatic restriction, enzymatic modification, cloning etc). This procedure consists in placing DNA band-containing agarose or acrylamide slices into sample wells of the electroeluter, then applying current will make the DNA fragment to leave the agarose and thus be trapped in a cushion salt to be recovered later by ethanol precipitation.

This procedure allows the purification of DNA fragments with high yield.

Electroeluting fragmentos de ADN

Purified DNA fragments are used for different purposes in Molecular Biology and they can be prepared by several procedures. Most of them require a ...

Generation of RNA/DNA Hybrids in Genomic DNA by Transformation using RNA-containing Oligonucleotides

Synthetic short nucleic acid polymers, oligonucleotides (oligos), are the most functional and widespread tools of molecular biology. Oligos can be produced to contain any desired DNA or RNA sequence and can be prepared to include a wide variety of base and sugar modifications. Moreover, oligos can be designed to mimic specific nucleic acid alterations and thus, can serve as important tools to investigate effects of DNA damage and mechanisms of repair. We found that Thermo Scientific Dharmacon RNA-containing oligos with a length between 50 and 80 nucleotides can be particularly suitable to study, in vivo, functions and consequences of chromosomal RNA/DNA hybrids and of ribonucleotides embedded into DNA. RNA/DNA hybrids can readily form during DNA replication, repair and transcription, however, very little is known about the stability of RNA/DNA hybrids in cells and to which extent these hybrids can affect the genetic integrity of cells. RNA-containing oligos, therefore, represent a perfect vector to introduce ribonucleotides into chromosomal DNA and generate RNA/DNA hybrids of chosen length and base composition. Here we present the protocol for the incorporation of ribonucleotides into the genome of the eukaryotic model system yeast /Saccharomyces cerevisiae/. Yet, our lab has utilized Thermo Scientific Dharmacon RNA-containing oligos to generate RNA/DNA hybrids at the chromosomal level in different cell systems, from bacteria to human cells.

This work shows how to form an RNA/DNA hybrid at the chromosomal level and reveal transfer of genetic information from RNA to genomic DNA in yeast cells.

Generación de ADN / ARN híbridos en el ADN genómico de transformación utilizando oligonucleótidos de ARN que contiene

Synthetic short nucleic acid polymers, oligonucleotides (oligos), are the most functional and widespread tools of molecular biology. Oligos can be ...

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Maintenance of replication fork stability is of utmost importance for dividing cells to preserve viability and prevent disease. The processes involved not only ensure faithful genome duplication in the face of endogenous and exogenous DNA damage but also prevent genomic instability, a recognized causative factor in tumor development.
Here, we describe a simple and cost-effective fluorescence microscopy-based method to visualize DNA replication in the avian B-cell line DT40. This cell line provides a powerful tool to investigate protein function in vivo by reverse genetics in vertebrate cells1. DNA fiber fluorography in DT40 cells lacking a specific gene allows one to elucidate the function of this gene product in DNA replication and genome stability. Traditional methods to analyze replication fork dynamics in vertebrate cells rely on measuring the overall rate of DNA synthesis in a population of pulse-labeled cells. This is a quantitative approach and does not allow for qualitative analysis of parameters that influence DNA synthesis. In contrast, the rate of movement of active forks can be followed directly when using the DNA fiber technique2-4. In this approach, nascent DNA is labeled in vivo by incorporation of halogenated nucleotides (Fig 1A). Subsequently, individual fibers are stretched onto a microscope slide, and the labeled DNA replication tracts are stained with specific antibodies and visualized by fluorescence microscopy (Fig 1B). Initiation of replication as well as fork directionality is determined by the consecutive use of two differently modified analogues. Furthermore, the dual-labeling approach allows for quantitative analysis of parameters that influence DNA synthesis during the S-phase, i.e. replication structures such as ongoing and stalled forks, replication origin density as well as fork terminations. Finally, the experimental procedure can be accomplished within a day, and requires only general laboratory equipment and a fluorescence microscope.

DT40, a model vertebrate genetic system, provides a powerful tool to analyze protein function. Here we describe a simple method that allows qualitative analysis of parameters that influence DNA synthesis during the S-phase in DT40 cells at the single molecule level.

Visualización de la replicación del ADN en el DT40 modelo de sistema de vertebrados que utilizan la técnica de fibra de ADN

Maintenance of replication fork stability is of utmost importance for dividing cells to preserve viability and prevent disease. The processes involved not ...

Iterative Optimization of DNA Duplexes for Crystallization of SeqA-DNA Complexes

Escherichia coli SeqA is a negative regulator of DNA replication that prevents premature reinitiation events by sequestering hemimethylated GATC clusters within the origin of replication1. Beyond the origin, SeqA is found at the replication forks, where it organizes newly replicated DNA into higher ordered structures2. SeqA associates only weakly with single GATC sequences, but it forms high affinity complexes with DNA duplexes containing multiple GATC sites. The minimal functional and structural unit of SeqA is a dimer, thereby explaining the requirement of at least two GATC sequences to form a high-affinity complex with hemimethylated DNA3. Additionally, the SeqA architecture, with the oligomerization and DNA-binding domains separated by a flexible linker, allows binding to GATC repeats separated by up to three helical turns. Therefore, understanding the function of SeqA at a molecular level requires the structural analysis of SeqA bound to multiple GATC sequences. In protein-DNA crystallization, DNA can have none to an exceptional effect on the packing interactions depending on the relative sizes and architecture of the protein and the DNA. If the protein is larger than the DNA or footprints most of the DNA, the crystal packing is primarily mediated by protein-protein interactions. Conversely, when the protein is the same size or smaller than the DNA or it only covers a fraction of the DNA, DNA-DNA and DNA-protein interactions dominate crystal packing. Therefore, crystallization of protein-DNA complexes requires the systematic screening of DNA length4 and DNA ends (blunt or overhang)5-7. In this report, we describe how to design, optimize, purify and crystallize hemimethylated DNA duplexes containing tandem GATC repeats in complex with a dimeric variant of SeqA (SeqA&Delta;(41-59)-A25R) to obtain crystals suitable for structure determination.

Crystal structure of protein&#x2013;DNA complexes can provide insight into protein function, mechanism, as well as, the nature of the specific interaction. Here, we report how to optimize the length, sequence and ends of duplex DNA for co-crystallization with Escherichia coli SeqA, a negative regulator of replication initiation.

Iterativo de optimización de dúplex de ADN para la cristalización de SEQA-ADN complejos

Escherichia coli SeqA is a negative regulator of DNA replication that prevents premature reinitiation events by sequestering hemimethylated GATC clusters ...

Identification of Metabolically Active Bacteria in the Gut of the Generalist Spodoptera littoralis via DNA Stable Isotope Probing Using 13C-Glucose

Guts of most insects are inhabited by complex communities of symbiotic nonpathogenic bacteria. Within such microbial communities it is possible to identify commensal or mutualistic bacteria species. The latter ones, have been observed to serve multiple functions to the insect, i.e. helping in insect reproduction1, boosting the immune response2, pheromone production3, as well as nutrition, including the synthesis of essential amino acids4, among others. &#160; &#160;
Due to the importance of these associations, many efforts have been made to characterize the communities down to the individual members. However, most of these efforts were either based on cultivation methods or relied on the generation of 16S rRNA gene fragments which were sequenced for final identification. Unfortunately, these approaches only identified the bacterial species present in the gut and provided no information on the metabolic activity of the microorganisms.
To characterize the metabolically active bacterial species in the gut of an insect, we used stable isotope probing (SIP) in vivo employing 13C-glucose as a universal substrate. This is a promising culture-free technique that allows the linkage of microbial phylogenies to their particular metabolic activity. This is possible by tracking stable, isotope labeled atoms from substrates into microbial biomarkers, such as DNA and RNA5. The incorporation of 13C isotopes into DNA increases the density of the labeled DNA compared to the unlabeled (12C) one. In the end, the 13C-labeled DNA or RNA is separated by density-gradient ultracentrifugation from the 12C-unlabeled similar one6. Subsequent molecular analysis of the separated nucleic acid isotopomers provides the connection between metabolic activity and identity of the species.
Here, we present the protocol used to characterize the metabolically active bacteria in the gut of a generalist insect (our model system), Spodoptera littoralis (Lepidoptera, Noctuidae). The phylogenetic analysis of the DNA was done using pyrosequencing, which allowed high resolution and precision in the identification of insect gut bacterial community. As main substrate, 13C-labeled glucose was used in the experiments. The substrate was fed to the insects using an artificial diet.

Identification of Metabolically Active Bacteria in the Gut of the Generalist Spodoptera littoralis via DNA Stable Isotope Probing Using 13C-Glucose

The active bacterial community associated with the gut of Spodoptera littoralis, was determined by stable-isotope-probing (SIP) coupled to pyrosequencing. Using this methodology, identification of the metabolically active bacteria species within the community was done with high resolution and precision.

La identificación de bacterias metabólicamente activas en el intestino de la Generalista<em&gt; Spodoptera littoralis</em&gt; Vía ADN isótopos estables Uso<sup&gt; 13</sup&gt; C-glucosa

Guts of most insects are inhabited by complex communities of symbiotic nonpathogenic bacteria. Within such microbial communities it is possible to ...

Preparation of DNA-crosslinked Polyacrylamide Hydrogels

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, the effect of tissue elasticity on cell function is a major area of mechanobiology research because tissue stiffness modulates with disease, development, and injury. Static tissue-mimicking materials, or materials that cannot alter stiffness once cells are plated, are predominately used to investigate the effects of tissue stiffness on cell functions. While information gathered from static studies is valuable, these studies are not indicative of the dynamic nature of the cellular microenvironment in vivo. To better address the effects of dynamic stiffness on cell function, we developed a DNA-crosslinked polyacrylamide hydrogel system (DNA gels). Unlike other dynamic substrates, DNA gels have the ability to decrease or increase in stiffness after fabrication without stimuli. DNA gels consist of DNA crosslinks that are polymerized into a polyacrylamide backbone. Adding and removing crosslinks via delivery of single-stranded DNA allows temporal, spatial, and reversible control of gel elasticity. We have shown in previous reports that dynamic modulation of DNA gel elasticity influences fibroblast and neuron behavior. In this report and video, we provide a schematic that describes the DNA gel crosslinking mechanisms and step-by-step instructions on the preparation DNA gels.

Our laboratory has developed DNA-crosslinked polyacrylamide hydrogels, a dynamic hydrogel system, to better understand the effects of modulating tissue stiffness on cell function. Here, we provide schematics, descriptions, and protocols to prepare these hydrogels.

Preparación de ADN-poliacrilamida reticulada hidrogeles

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, ...

Real-time Imaging of Single Engineered RNA Transcripts in Living Cells Using Ratiometric Bimolecular Beacons

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the development of diverse techniques to visualize individual RNA transcripts in single living cells. One promising technique that has recently been described utilizes an oligonucleotide-based optical probe, ratiometric bimolecular beacon (RBMB), to detect RNA transcripts that were engineered to contain at least four tandem repeats of the RBMB target sequence in the 3&#8217;-untranslated region. RBMBs are specifically designed to emit a bright fluorescent signal upon hybridization to complementary RNA, but otherwise remain quenched. The use of a synthetic probe in this approach allows photostable, red-shifted, and highly emissive organic dyes to be used for imaging. Binding of multiple RBMBs to the engineered RNA transcripts results in discrete fluorescence spots when viewed under a wide-field fluorescent microscope. Consequently, the movement of individual RNA transcripts can be readily visualized in real-time by taking a time series of fluorescent images. Here we describe the preparation and purification of RBMBs, delivery into cells by microporation and live-cell imaging of single RNA transcripts.

Ratiometric bimolecular beacons (RBMBs) can be used to image single engineered RNA transcripts in living cells. Here, we describe the preparation and purification of RBMBs, delivery of RBMBs into cells by microporation and fluorescent imaging of single RNA transcripts in real-time.

Imágenes en tiempo real de Soltero Engineered ARN transcritos en células vivas utilizando Ratiometric bimoleculares Balizas

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the ...