Name: proofreading and dna repair assay using single nucleotide extension and maldi-tof mass spectrometry analysis
Uploaded: 2018-06-19T14:45:00
Description: Watch this Scientific Journal Video about Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis at JoVE.com

We thank the NCFPB Integrated Core Facility for Functional Genomics (Taipei, Taiwan) and the NRPB Pharmacogenomics Lab (Taipei, Taiwan) for their technical support. This work was supported by research grants from the Taiwan Health Foundation (L-I.L.) and the Ministry of Science and Technology, Taipei, Taiwan, ROC [MOST 105-2320-B-002-047] for Woei-horng Fang, [MOST 105-2628-B-002 -051-MY3] for Kang-Yi Su, and [MOST-105-2320-B-002-051-MY3] for Liang-In Lin.

1. Primer/template Preparation
<ol>
	<li>Design primers/templates with a balanced G+C content between 40% and 60% as in a sequencing or PCR primer design. Use primers of 18 to 21 nt for an appropriate annealing and better MS signals.</li>
	<li>Design the template by setting 50 &#176;C as the minimum melting temperature for the duplex region with at least 7 nt of 5&#39;-overhang to separate the signals between the primer and the template. 
	NOTE: For example, for the substrate P21/T28 in Table 1, t...

<ol>
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H., 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+highly+sensitive+G-quadruplex-based+luminescent+switch-on+probe+for+the+detection+of+polymerase+3'-5'+proofreading+activity.">A highly sensitive G-quadruplex-based luminescent switch-on probe for the detection of polymerase 3'-5' proofreading activity.</a> Methods. 64 (3), 224-228 (2013).</li><li>Song, C., Zhang, C., Zhao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+and+sensitive+detection+of+DNA+polymerase+fidelity+by+singly+labeled+smart+fluorescent+probes.">Rapid and sensitive detection of DNA polymerase fidelity by singly labeled smart fluorescent probes.</a> Biosensors and Bioelectronics. 26 (5), 2699-2702 (2011).</li><li>Haff, L. A., Smirnov, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-nucleotide+polymorphism+identification+assays+using+a+thermostable+DNA+polymerase+and+delayed+extraction+MALDI-TOF+mass+spectrometry.">Single-nucleotide polymorphism identification assays using a thermostable DNA polymerase and delayed extraction MALDI-TOF mass spectrometry.</a> Genome Research. 7 (4), 378-388 (1997).</li><li>Haff, L. A., Smirnov, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplex+genotyping+of+PCR+products+with+MassTag-labeled+primers.">Multiplex genotyping of PCR products with MassTag-labeled primers.</a> Nucleic Acids Research. 25 (18), 3749-3750 (1997).</li><li>Blondal, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+MALDI-TOF+based+methodology+for+genotyping+single+nucleotide+polymorphisms.">A novel MALDI-TOF based methodology for genotyping single nucleotide polymorphisms.</a> Nucleic Acids Research. 31 (24), e155 (2003).</li><li>Su, K. 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=Pretreatment+Epidermal+Growth+Factor+Receptor+(EGFR)+T790M+mutation+predicts+shorter+EGFR+tyrosine+kinase+inhibitor+response+duration+in+patients+with+non-small-cell+lung+cancer.">Pretreatment Epidermal Growth Factor Receptor (EGFR) T790M mutation predicts shorter EGFR tyrosine kinase inhibitor response duration in patients with non-small-cell lung cancer.</a> Journal of Clinical Oncology. 30 (4), 433-440 (2012).</li><li>Lee, C. C., 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=Endonuclease+V-mediated+deoxyinosine+excision+repair+in+vitro.">Endonuclease V-mediated deoxyinosine excision repair in vitro.</a> DNA Repair. 9, 1073-1079 (2010).</li><li>Lee, C. C., 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=The+excision+of+3'+penultimate+errors+by+DNA+polymerase+I+and+its+role+in+endonuclease+V-mediated+DNA+repair.">The excision of 3' penultimate errors by DNA polymerase I and its role in endonuclease V-mediated DNA repair.</a> DNA Repair. 12 (11), 899-911 (2013).</li><li>Kucera, R. B., Nichols, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA-Dependent+DNA+Polymerases.">DNA-Dependent DNA Polymerases.</a> Current Protocols in Molecular Biology. 84 (1), 3.5.1-3.5.19 (2008).</li><li>Tabor, S., Richardson, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+residue+in+DNA+polymerases+of+the+Escherichia+coli+DNA+polymerase+I+family+is+critical+for+distinguishing+between+deoxy-+and+dideoxyribonucleotides.">A single residue in DNA polymerases of the Escherichia coli DNA polymerase I family is critical for distinguishing between deoxy- and dideoxyribonucleotides.</a> Proceedings of the National Academy of Sciences of the United States of America. 92 (14), 6339-6343 (1995).</li><li>Weiss, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Removal+of+deoxyinosine+from+the+Escherichia+coli+chromosome+as+studied+by+oligonucleotide+transformation.">Removal of deoxyinosine from the Escherichia coli chromosome as studied by oligonucleotide transformation.</a> DNA Repair. 7 (2), 205-212 (2008).</li><li>Cao, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endonuclease+V:+an+unusual+enzyme+for+repair+of+DNA+deamination.">Endonuclease V: an unusual enzyme for repair of DNA deamination.</a> Cellular and Molecular Life Sciences. 70 (17), 3145-3156 (2013).</li><li>Su, K. 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This study described a step-by-step proofreading activity assay analyzed by the chosen commercial instrument (see the Table of Materials) using MALDI-TOF MS. The major advantages include that the primer and template are label free and easy to perform, allowing for greater flexibility in designing experiments. A stream-lime complete processing of 30 proofreading tests would take 4 h, including 3 h for manually performing the proofreading reactions and their cleanup, while the MALDI-TOF MS analyses using t...

The proofreading functions of DNA polymerases during DNA replication are essential to ensure the high fidelity of genetic information that needs to be transferred to progeny1,2,3,4,5,6,7. Being able to assess the contributions of polymerase proofreading exonucleases would clarify the mechanisms safeguarding genetic stability.
Radioisotope labeling and gel-based assays in combination with densitometric analyses of the autoradiograms or phosphor imaging8,9,10 have traditionally been used to detect proofreading activity of DNA polymerases. While functional, these assays are laborious, expensive, and not amenable to high-throughput formats. In addition, radioisotopes suffer safety issues including waste disposal. Alternatively, proofreading activities have been analyzed by fluorometric techniques. For example, 2-aminopurine (2-AP) can be incorporated into extension products during in vitro polymerase proofreading assays to produce a fluorescent signal11,12. Unfortunately, these approaches suffer from a low specificity, since 2-AP can pair with both thymine and cytosine. More recent approaches include a sensitive G-quadruplex-based luminescent switch-on probe for a polymerase 3&#39;-5&#39; exonuclease assay13 as well as a singly-labeled fluorescent probe for a polymerase proofreading assay that overcomes some of the aforementioned drawbacks14. Enthusiasm for these fluorometric methods is diminished due to the need for the specific labeling of DNA substrates.
In contrast, a MALDI-TOF MS for DNA analysis has been employed in the PinPoint assay, where the primer extension reactions with unlabeled 4 ddNTPs can be used to identify polymorphisms at a given locus15,16,17 and has been widely adopted in clinical applications for mutation detections and cancer diagnoses18. Using these basic principles, we have created a label-free assay for the in vitro determination of DNA polymerase proofreading activity exploiting the high resolution, high specificity, and high-throughput potential of MALDI-TOF MS. Using the E. coli DNA polymerase I Klenow fragment as a model enzyme, dideoxyribonucleotide triphosphates (ddNTPs) as substrates can take a &#34;snapshot&#34; of proofreading products after a single nucleotide extension via MALDI-TOF MS (Figure 1).
Likewise, this method was also developed for a DNA repair assay where primers containing 3&#39; penultimate dI lesions are subjected to a pol I repair assay which mimics endo V nicked repair intermediates. While not fully understood, the endo V repair pathway is the only repair system known to employ the pol I proofreading exonuclease activity for lesion excision19,20. Using MALDI-TOF MS, we show a clearly defined repair patch where dI can be excised by pol I when occurring in the last 2 nt of the primer before adding the correct complemented nucleotide.
For the study of proofreading and DNA repair, this method is faster and less laborious than previous methods and provides additional information towards mechanism and function.

<table border="0" cellpadding="0" cellspacing="0" style="width:1124px;" width="1125">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:331px;">Oligonucleotides</td>
			<td style="width:283px;">Mission Biotech (Taiwan)&#160;</td>
			<td style="width:344px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">phosphorothioate modified oligonucleotides</td>
			<td>&#160;Integrated DNA Technologies (Taiwan)</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">DNA polymerase I, Large (Klenow) Fragment</td>
			<td>New England Biolabs, MA</td>
			<td>M0210L</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Klenow fragment (3&#39;&#8594;5&#39; exo-)</td>
			<td>New England Biolabs, MA</td>
			<td>M0212L</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">NEBuffer 2.1 (10X)</td>
			<td>New England Biolabs, MA</td>
			<td>B7202S</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">2&#39;, 3&#39; ddATP</td>
			<td>Trilink Biotechnologies, CA</td>
			<td>N4001</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">2&#39;, 3&#39; ddGTP</td>
			<td>Trilink Biotechnologies, CA</td>
			<td>N4002</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">2&#39;, 3&#39; ddTTP</td>
			<td>Trilink Biotechnologies, CA</td>
			<td>N4004</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">2&#39;, 3&#39; ddCTP</td>
			<td>Trilink Biotechnologies, CA</td>
			<td>N4005</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">dATP, dGTP, dCTP, dTTP set</td>
			<td>Clubio, Taiwan</td>
			<td>CB-R0315</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">SpectroCHIP array</td>
			<td>&#160;Agena Bioscience, CA</td>
			<td>#01509</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">MassARRAY&#160;</td>
			<td>&#160;Agena Bioscience, CA</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Typer 4.0 software</td>
			<td>&#160;Agena Bioscience, CA</td>
			<td>#10145</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Clean Resin Tool Kit&#160;</td>
			<td>&#160;Agena Bioscience, CA</td>
			<td>#08040</td>
			<td></td>
		</tr>
	</tbody>
</table>

proofreading and dna repair assay using single nucleotide extension and maldi-tof mass spectrometry analysis

The maintenance of the genome and its faithful replication is paramount for conserving genetic information. To assess high fidelity replication, we have developed a simple non-labeled and non-radio-isotopic method using a matrix-assisted laser desorption ionization with time-of-flight (MALDI-TOF) mass spectrometry (MS) analysis for a proofreading study. Here, a DNA polymerase [e.g., the Klenow fragment (KF) of Escherichia coli DNA polymerase I (pol I) in this study] in the presence of all four dideoxyribonucleotide triphosphates is used to process a mismatched primer-template duplex. The mismatched primer is then proofread/extended and subjected to MALDI-TOF MS. The products are distinguished by the mass change of the primer down to single nucleotide variations. Importantly, a proofreading can also be determined for internal single mismatches, albeit at different efficiencies. Mismatches located at 2-4-nucleotides (nt) from the 3' end were efficiently proofread by pol I, and a mismatch at 5 nt from the primer terminus showed only a partial correction. No proofreading occurred for internal mismatches located at 6 - 9 nt from the primer 3' end. This method can also be applied to DNA repair assays (e.g., assessing a base-lesion repair of substrates for the endo V repair pathway). Primers containing 3' penultimate deoxyinosine (dI) lesions could be corrected by pol I. Indeed, penultimate T-I, G-I, and A-I substrates had their last 2 dI-containing nucleotides excised by pol I before adding a correct ddN 5'-monophosphate (ddNMP) while penultimate C-I mismatches were tolerated by pol I, allowing the primer to be extended without repair, demonstrating the sensitivity and resolution of the MS assay to measure DNA repair.

Templates and primers:
Using the procedure presented here, equal molar synthetic oligonucleotide templates and primers of relevant sequences obtained from commercial sources were checked for their purity and quality (Figure&#160;3A; note the signals matched the designated mass and the low background) as well as for the relationship between the peak intensity and the analyte mass (<s...

Watch this Scientific Journal Video about Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis at JoVE.com

Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis

A non-labeled, non-radio-isotopic method for DNA polymerase proofreading and a DNA repair assay was developed by using high-resolution MALDI-TOF mass spectrometry and a single nucleotide extension strategy. The assay proved to be very specific, simple, rapid, and easy to perform for proofreading and repair patches shorter than 9-nucleotides.

The maintenance of the genome and its faithful replication is paramount for conserving genetic information. To assess high fidelity replication, we have ...

This method can help answer key questions in the field of DNA polymers fidelity and DNA repair such as proofreading methods and analysis and in defining the DNA repair patch. The main advantage of this technique is that it is very specific, simple, rapid, and easy to perform. Generally, individuals new to this method will struggle because of still they in DNA replication and the repair field may be not familiar with the mass spectrometry instrumentation and the data interpretation.I think the most important is the visual demonstration is very critical as we can show how our commercially developed mass spectrometry for clinical applications such as mutation and deputation can be conveniently adapted for DNA proofreading and the repair study. Demonstrating the procedure will be Rong-Syuan and Kuei-Ching graduate students from my lab. Begin this procedure with primer and template preparation as described in the text protocol.As an example, use a TG mismatch of substrate P21 with T28 for the proofreading. Dilute the P21 primer and the T28 template to 12.5 picomoles per microliter with water. Then, transfer 12 microliters of the diluted primer and 12 microliters of the diluted template to a 1.5 milliliter sterilized micro centrifuge tube.After closing the tube tightly, incubate the tube for 30 minutes in a covered 65 degree Celsius water bath. Then, incubate for 30 minutes in a 37 degree Celsius water bath. And, finally, place the tube on ice to ensure a proper annealing.To a 1.5 milliliter sterilized micro centrifuge tube, add eight microliters of primer and template mix, two microliters of 10x proofreading reaction buffer, four microliters of 4ddNTPs mix, and water up to 18 microliters. Flick the tube to mix. Dilute the DNA polymerase in ice cold 1x proofreading reaction buffer to the desired concentration.Store the diluted enzyme on ice at all times. Pre-warm the micro centrifuge tube with the substrate mix to the desired reaction temperature. Then, transfer two microliters of the diluted DNA polymerase to the pre-warmed substrate mixture and flick the tube to mix its contents.Centrifuge the tubes with enzyme and substrate for a few seconds at 3200 times gravity at ambient temperature to spin down the components of the reactions. Immediately transfer the reaction to a heating block or a water bath at the desired incubation temperature. To terminate the reaction, add an equal volume of buffered phenol and mix the reaction by vortexing for a few seconds.Then, centrifuge the reaction in a micro-centrifuge at 3200 times gravity at ambient temperature for five minutes. Transfer the aqueous phase to a clean micro-centrifuge tube and add an equal volume of chloroform. After mixing it by vortexing for a few seconds, centrifuge the sample in a microcentrifuge at 3200 times gravity at ambient temperature for three minutes.Transfer the aqueous phase to a clean micro-centrifuge tube. After incubating the reaction at 95 degrees Celsius for five minutes, place the tube on ice. Next, perform resin addition to eliminate salt contamination in a 384 well plate as detailed in the text protocol.Set the sample plates in the nanoliter dispenser. Place the matrix chip and the prepared 384 well plate in the corresponding tray. Operate the nano-dispenser to spot the reaction products to the chip.Push the run button on the touch screen of the nano-dispenser to start. Check the automated captured image of the sample spots containing saturation information on the screen to ensure the overall spotted volume on the chip is around five to 10 nanoliters. Repeat the sample spotting if the volume is insufficient.Prepare a file in Excel format containing the anticipated signal information for importing. Create and define a new assay in the application program by right-clicking import assay group in designer format and select the Excel file. Establish the target assay plate via the customer project plate option tree on the left side of the screen by right-clicking the top of the tree and giving it a file name.Select the 384 well plate type and press OK.A blank plate will appear. Select the appropriate assay on the left side of the screen. Assign the selected assay for each spotted sample position on the chip by highlighting the well and right-clicking to select add plex.Next, prepare a working list of all the tests on the chip in Excel format with no header. Import the working list via the add new sample project option. Assign the test and the working list to each position of the P21T28 assay and choose by right-clicking.Link the mass spectrometer to the chip using the application program. Select the default setting at the right side of the screen. Fill in the assay name and the chip ID at the corner of the chip.Save the settings and start the MS control program. Press the in/out button and take out the scout plate. Place the spotted chip onto the scout plate and press the in/out button for the spotted chip to enter the mass spectrometer.Click the acquire button of the application program to start the mass spectrometry and acquire the data. Open the program for the data analysis. Browse the tree of the database at the upper left corner and select the chip ID.Open the data file on the right side of the screen.Click the spectrum icon to display the mass spectrum. To crop a specific range of mass over charge, right-click to select customization dialogue. In the new window, click on x-axis and set the desired upper and lower limit and press OK to show the specified range of the spectrum.Export the spectrum for record keeping by right-clicking export. Select the JPEG file type, click on destination, select browse disc, type the file name, and then click on export. For data quantitation, use the cursor and click on the peak to show the peak height at the upper left hand corner.In MALDI-TOF MS there is an inverse relationship between peak intensity in Oligonucleotide mass. Oligonucleotides from 17 to 24 nucleotides were subjected to an MS analysis. The relative signal intensities were calculated and could be used for quantification of the proofreading or repair assay.Both template and primer signals could be found in the mass spectrum. Because of size differences, signals from templates and their non-specific partial degradation products were well separated from the mismatched primers and proofread products. Shown here is a proofreading of a three prime terminal TG.At five minutes, the corrected product was 23%versus 17%for the excision product.This difference continued to increase to 69%versus 14%at 20 minutes. Note the high resolution of MS clearly separating the sub-straight and product signals with a mass overcharge difference of only 32. Also easily resolvable were two forms of excision products for a pen ultimate TG proofreading.The one nucleotide excision intermediate and two nucleotide excision products. Proofreading of internal mismatches showed a clear trend in proofreading efficiency. As evidenced by a large proofread product speak, increased efficiency was observed when substraights had mismatches at the last, penultimate, third, and fourth nucleotides from the three prime end, as compared to mismatches at other positions.Once mastered, this technique can be done in four hours if it is performed properly. Following this procedure, other applications like polymerous proofreading heapiter screening can be performed to discover and invent new drug for pharmaceutical research. This technique also paves the way for researchers in the field of DNA replication and repair to gain more insight into the medicine of the gnome and it's faithful replication for all living organisms.After watching this video, you should have a good understanding of how to perform DNA proofreading and the repair assay using MADI-TOF mass spectrometry analysis. Don't forget that working with spheno-chloroform can be hazardous and the precautions, such as wearing personal protection gear, should always be taken while performing the procedure. The alternative protocol in the text could be considered as a safer substitute.

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Unit 1

DNA Replication

DNA Replication and Repair

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Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological processes. Affinity purification coupled to mass spectrometry (AP-MS) has become the method of choice for identifying protein-protein interactions. However, conventional AP-MS studies provide information on protein interactions, but the organizational information is lost. To address this issue, we developed a strategy to unravel the distinct functional assemblies a protein might be involved in, by resolving affinity-purified protein complexes prior to their characterization by mass spectrometry. Protein complexes isolated through affinity purification of a bait protein using an epitope tag and competitive elution are separated through blue native electrophoresis. Comparison of protein migration profiles through correlation profiling using quantitative mass spectrometry allows assignment of interacting proteins to distinct molecular entities. This method is able to resolve protein complexes of close molecular weights that might not be resolved by traditional chromatographic techniques such as gel filtration. With little more work than conventional AP-geLC-MS/MS, we demonstrate this strategy may in many cases be adequate for obtaining protein complex topological information concomitantly to identifying protein interactions.

Here we present protocols for affinity purification of protein complexes and their separation by blue native PAGE, followed by protein correlation profiling using label free quantitative mass spectrometry. This method is useful to resolve interactomes into distinct protein complexes.

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological ...

Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of virion morphogenesis. Quantitative lipid droplet proteome analysis can be used to identify proteins that localize to or are displaced from lipid droplets under conditions such as virus infections. Here, we describe a protocol that has been successfully used to characterize the changes in the lipid droplet proteome following infection with HCV. We use Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) and thus label the complete proteome of one population of cells with &#34;heavy&#34; amino acids to quantitate the proteins by mass spectrometry. For lipid droplet isolation, the two cell populations (i.e.&#160;HCV-infected/&#34;light&#34; amino acids and uninfected control/&#34;heavy&#34; amino acids) are mixed 1:1 and lysed mechanically in hypotonic buffer. After removing the nuclei and cell debris by low speed centrifugation, lipid droplet-associated proteins are enriched by two subsequent ultracentrifugation steps followed by three washing steps in isotonic buffer. The purity of the lipid droplet fractions is analyzed by western blotting with antibodies recognizing different subcellular compartments. Lipid droplet-associated proteins are then separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Coomassie staining. After tryptic digest, the peptides are quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Using this method, we identified proteins recruited to lipid droplets upon HCV infection that might represent pro- or antiviral host factors. Our method can be applied to a variety of different cells and culture conditions, such as infection with pathogens, environmental stress, or drug treatment.

Lipid droplets are important organelles for the replication of several pathogens, including the Hepatitis C Virus (HCV). We describe a method to isolate lipid droplets for quantitative mass spectrometry of associated proteins; it can be used under a variety of conditions, such as virus infection, environmental stress, or drug treatment.

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of ...

The Determination of Protease Specificity in Mouse Tissue Extracts by MALDI-TOF Mass Spectrometry: Manipulating PH to Cause Specificity Changes

Proteases have several biological functions, including protein activation/inactivation and food digestion. Identifying protease specificity is important for revealing protease function. The method proposed in this study determines protease specificity by measuring the molecular weight of unique substrates using Matrix-assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry. The substrates contain iminobiotin, while the cleaved site consists of amino acids, and the spacer consists of polyethylene glycol. The cleaved substrate will generate a unique molecular weight using a cleaved amino acid. One of the merits of this method is that it may be carried out in one pot using crude samples, and it is also suitable for assessing multiple samples. In this article, we describe a simple experimental method optimized with samples extracted from mouse lung tissue, including tissue extraction, placement of digestive substrates into samples, purification of digestive substrates under different pH conditions, and measurement of the substrates&#39; molecular weight using MALDI-TOF mass spectrometry. In summary, this technique allows for the identification of protease specificity in crude samples derived from tissue extracts using MALDI-TOF mass spectrometry, which may easily be scaled up for multiple sample processing.

Here, we present a protocol to determine protease specificity in crude mouse tissue extracts using MALDI-TOF spectrometry.

Proteases have several biological functions, including protein activation/inactivation and food digestion. Identifying protease specificity is important ...

Using the Open-Source MALDI TOF-MS IDBac Pipeline for Analysis of Microbial Protein and Specialized Metabolite Data

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, we developed IDBac&#8212;a low-cost and high-throughput matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bioinformatics pipeline. IDBac software is designed for non-experts, is freely available, and capable of analyzing a few to thousands of bacterial colonies. Here, we present procedures for the preparation of bacterial colonies for MALDI-TOF MS analysis, MS instrument operation, and data processing and visualization in IDBac. In particular, we instruct users how to cluster bacteria into dendrograms based on protein MS fingerprints and interactively create Metabolite Association Networks (MANs) from specialized metabolite data.

IDBac is an open-source mass spectrometry-based bioinformatics pipeline that integrates data from both intact protein and specialized metabolite spectra, collected on cell material scraped from bacterial colonies. The pipeline allows researchers to rapidly organize hundreds to thousands of bacterial colonies into putative taxonomic groups, and further differentiate them based on specialized metabolite production.

In order to visualize the relationship between bacterial phylogeny and specialized metabolite production of bacterial colonies growing on nutrient agar, ...

Nitropeptide Profiling and Identification Illustrated by Angiotensin II

Protein nitration is one of the most important post-translational modifications (PTM) on tyrosine residues and it can be induced by chemical actions of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in eukaryotic cells. Precise identification of nitration sites on proteins is crucial for understanding the physiological and pathological processes related to protein nitration, such as inflammation, aging, and cancer. Since the nitrated proteins are of low abundance in cells even under induced conditions, no universal and efficient methods have been developed for the profiling and identification of protein nitration sites. Here we describe a protocol for nitropeptide enrichment by using a chemical reduction reaction and biotin labeling, followed by high resolution mass spectrometry. In our method, nitropeptide derivatives can be identified with high accuracy. Our method exhibits two advantages compared to the previously reported methods. First, dimethyl labeling is used to block the primary amine on nitropeptides, which can be used to generate quantitative results. Second, a disulfide bond containing NHS-biotin reagent is used for the enrichment, which can be further reduced and alkylated to enhance the detection signal on a mass spectrometer. This protocol has been successfully applied to the model peptide Angiotensin II in the current paper.

Proteomic profiling of tyrosine-nitrated proteins has been a challenging technique due to the low abundance of the 3-nitrotyrosine modification. Here we describe a novel approach for nitropeptide enrichment and profiling by using Angiotensin II as the model. This method can be extended for other in vitro or in vivo systems.

Protein nitration is one of the most important post-translational modifications (PTM) on tyrosine residues and it can be induced by chemical actions of ...

Dual DNA Rulers to Study the Mechanism of Ribosome Translocation with Single-Nucleotide Resolution

The ribosome translocation refers to the ribosomal movement on the mRNA by exactly three nucleotides (nt), which is the central step in protein synthesis. To investigate its mechanism, there are two essential technical requirements. First is single-nt resolution that can resolve normal translocation from frameshifting, during which the ribosome moves by other than 3 nt. The second is the capability to probe both the entrance and exit sides of mRNA in order to elucidate the whole picture of translocation. We report the dual DNA ruler assay that is based on the critical dissociation forces of DNA-mRNA duplexes, obtained by force-induced remnant magnetization spectroscopy (FIRMS).&#160; With 2-4 pN force resolution, the dual ruler assay is sufficient to distinguish different translocation steps. By implementing a long linker on the probing DNAs, they can reach the mRNA on the opposite side of the ribosome, so that the mRNA position can be determined for both sides. Therefore, the dual ruler assay is uniquely suited to investigate the ribosome translocation, and nucleic acid motion in general. We show representative results which indicated a looped mRNA conformation and resolved normal translocation from frameshifting.

Dual DNA ruler assay is developed to determine the mRNA position during ribosome translocation, which relies on the dissociation forces of the formed DNA-mRNA duplexes. With single-nucleotide resolution and capability of reaching both ends of mRNA, it can provide mechanistic insights for ribosome translocation and probe other nucleic acid displacements.

The ribosome translocation refers to the ribosomal movement on the mRNA by exactly three nucleotides (nt), which is the central step in protein synthesis. ...

An Integrated Raman Spectroscopy and Mass Spectrometry Platform to Study Single-Cell Drug Uptake, Metabolism, and Effects

Cells are known to be inherently heterogeneous in their responses to drugs. Therefore, it is essential that single-cell heterogeneity is accounted for in drug discovery studies. This can be achieved by accurately measuring the plethora of cellular interactions between a cell and drug at the single-cell level (i.e., drug uptake, metabolism, and effect). This paper describes a single-cell Raman spectroscopy and mass spectrometry (MS) platform to monitor metabolic changes of cells in response to drugs. Using this platform, metabolic changes in response to the drug can be measured by Raman spectroscopy, while the drug and its metabolite can be quantified using mass spectrometry in the same cell. The results suggest that it is possible to access information about drug uptake, metabolism, and response at a single-cell level.

This protocol presents an integrated Raman spectroscopy-mass spectrometry (MS) platform that is capable of achieving single-cell resolution. Raman spectroscopy can be used to study cellular response to drugs, while MS can be used for targeted and quantitative analysis of drug uptake and metabolism.

Cells are known to be inherently heterogeneous in their responses to drugs. Therefore, it is essential that single-cell heterogeneity is accounted for in ...

Quantitative Analysis of the Cellular Lipidome of Saccharomyces Cerevisiae Using Liquid Chromatography Coupled with Tandem Mass Spectrometry

Lipids are structurally diverse amphipathic molecules that are insoluble in water. Lipids are essential contributors to the organization and function of biological membranes, energy storage and production, cellular signaling, vesicular transport of proteins, organelle biogenesis, and regulated cell death. Because the budding yeast Saccharomyces cerevisiae is a unicellular eukaryote amenable to thorough molecular analyses, its use as a model organism helped uncover mechanisms linking lipid metabolism and intracellular transport to complex biological processes within eukaryotic cells. The availability of a versatile analytical method for the robust, sensitive, and accurate quantitative assessment of major classes of lipids within a yeast cell is crucial for getting deep insights into these mechanisms. Here we present a protocol to use liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for the quantitative analysis of major cellular lipids of S. cerevisiae. The LC-MS/MS method described is versatile and robust. It enables the identification and quantification of numerous species (including different isobaric or isomeric forms) within each of the 10 lipid classes. This method is sensitive and allows identification and quantitation of some lipid species at concentrations as low as 0.2 pmol/&#181;L. The method has been successfully applied to assessing lipidomes of whole yeast cells and their purified organelles. The use of alternative mobile phase additives for electrospray ionization mass spectrometry in this method can increase the efficiency of ionization for some lipid species and can be therefore used to improve their identification and quantitation.

Quantitative Analysis of the Cellular Lipidome of Saccharomyces Cerevisiae Using Liquid Chromatography Coupled with Tandem Mass Spectrometry

We present a protocol using liquid chromatography coupled with tandem mass spectrometry to identify and quantify major cellular lipids in Saccharomyces cerevisiae. The described method for a quantitative assessment of major lipid classes within a yeast cell is versatile, robust, and sensitive.

Lipids are structurally diverse amphipathic molecules that are insoluble in water. Lipids are essential contributors to the organization and function of ...

Untargeted Liquid Chromatography-Mass Spectrometry-Based Metabolomics Analysis of Wheat Grain

Understanding the interactions between genes, the environment and management in agricultural practice could allow more accurate prediction and management of product yield and quality. Metabolomics data provides a read-out of these interactions at a given moment in time and is informative of an organism&#39;s biochemical status. Further, individual metabolites or panels of metabolites can be used as precise biomarkers for yield and quality prediction and management. The plant metabolome is predicted to contain thousands of small molecules with varied physicochemical properties that provide an opportunity for a biochemical insight into physiological traits and biomarker discovery. To exploit this, a key aim for metabolomics researchers is to capture as much of the physicochemical diversity as possible within a single analysis. Here we present a liquid chromatography-mass spectrometry-based untargeted metabolomics method for the analysis of field-grown wheat grain. The method uses the liquid chromatograph quaternary solvent manager to introduce a third mobile phase and combines a traditional reversed-phase gradient with a lipid-amenable gradient. Grain preparation, metabolite extraction, instrumental analysis and data processing workflows are described in detail. Good mass accuracy and signal reproducibility were observed, and the method yielded approximately 500 biologically relevant features per ionization mode. Further, significantly different metabolite and lipid feature signals between wheat varieties were determined.

A method for the untargeted analysis of wheat grain metabolites and lipids is presented. The protocol includes an acetonitrile metabolite extraction method and reversed phase liquid chromatography-mass spectrometry methodology, with acquisition in positive and negative electrospray ionization modes.

Understanding the interactions between genes, the environment and management in agricultural practice could allow more accurate prediction and management ...