It is important to note that this work was a collaborative effort between three institutions, two research groups, and one core facility. The distribution and workload were carried out as follows: Protein (Xrn-1) expression was carried out at the University of Denver (Denver, CO). Oligonucleotide synthesis, quantification, and experimentation (mainly enzymatic degradation) were conducted at the University of Colorado Denver (Denver, CO). Optimization was also carried out there. MALDI-TOF spotting, acquisition, and analysis were carried out at the Analytical Resources Core Facility at Colorado State University. (Fort Collins, CO). SS would like to acknowledge a UROP Award (CU Denver) and Eureca grants (CU Denver) for support. E. G. C. acknowledges support from NIGMS, via R00GM115757. MJER acknowledges support from NIGMS, via 1R15GM132816. K. B. acknowledges resource ID: SCR_021758. The work was also supported by a Teacher-Scholar Award (MJER), TH-21-028, from the Henry Dreyfus Foundation.

RNase-free ultra pure water (Table 1) was used for the present study.
1. Concentration determination of RNA solution
<ol>
	<li>Prepare the RNA sample following the steps below.
	<ol>
		<li>Use a microcentrifuge tube (0.6 mL) to prepare a solution of RNA by diluting 1 &#181;L of stock solution (obtained via solid-phase synthesis)19 into 159 &#181;L of RNase-free H2O. Mix the solution by pipetting the mixture up and ...

<ol>
	<li>Tanaka, K., 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=Protein+and+polymer+analyses+up+to+m/z+100+000+by+laser+ionization+time-of-flight+mass+spectrometry.">Protein and polymer analyses up to m/z 100 000 by laser ionization time-of-flight mass spectrometry.</a> Rapid Communications in Mass Spectrometry. 2 (8), 151-153 (1988).</li><li>Karas, M., Hillenkamp, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+desorption+ionization+of+proteins+with+molecular+masses+exceeding+10,000+daltons.">Laser desorption ionization of proteins with molecular masses exceeding 10,000 daltons.</a> Analytical Chemistry. 60 (20), 2299-2301 (1988).</li><li>Zenobi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+nobel+prize+2002+goes+to+analytical+chemistry.">Chemistry nobel prize 2002 goes to analytical chemistry.</a> Chimia. 57, 73 (2003).</li><li>Aristri, M. A., 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=Bio-based+polyurethane+resins+derived+from+tannin:+Source,+synthesis,+characterization,+and+application.">Bio-based polyurethane resins derived from tannin: Source, synthesis, characterization, and application.</a> Forests. 12 (11), 1516 (2021).</li><li>Pedrazzani, 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=5-n-Alkylresorcinol+profiles+in+different+cultivars+of+einkorn,+emmer+spelt,+common+wheat,+and+tritordeum.">5-n-Alkylresorcinol profiles in different cultivars of einkorn, emmer spelt, common wheat, and tritordeum.</a> Journal of Agricultural and Food Chemistry. 69 (47), 14092-14102 (2021).</li><li>Unger, M. S., Blank, M., Enzlein, T., Hopf, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Label-free+cell+assays+to+determine+compound+uptake+or+drug+action+using+MALDI-TOF+mass+spectrometry.">Label-free cell assays to determine compound uptake or drug action using MALDI-TOF mass spectrometry.</a> Nature Protocols. 16 (12), 5533-5558 (2021).</li><li>Croxatto, A., Prod'hom, G., Greub, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+MALDI-TOF+mass+spectrometry+in+clinical+diagnostic+microbiology.">Applications of MALDI-TOF mass spectrometry in clinical diagnostic microbiology.</a> FEMS Microbiology Reviews. 36 (2), 380-407 (2012).</li><li>Kaufmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Marrix-assisted+laser+desorption+ionization+(MALDI)+mass+spectrometry:+a+novel+analytical+tool+in+molecular+biology+and+biotechnology.">Marrix-assisted laser desorption ionization (MALDI) mass spectrometry: a novel analytical tool in molecular biology and biotechnology.</a> Journal of Biotechnology. 41 (2-3), 155-175 (1995).</li><li>Kiggins, C., Skinner, A., Resendiz, M. 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K., Rojas, E. <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+antibacterial+immunity+proteins+in+Escherichia+coli+using+MALDI-TOF-TOF-MS/MS+and+Top-Down+proteomic+analysis.">Identification of antibacterial immunity proteins in Escherichia coli using MALDI-TOF-TOF-MS/MS and Top-Down proteomic analysis.</a> Journal of Visualized Experiments: JoVE. (171), e62577 (2021).</li><li>Phillips, C. N., 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=Processing+of+RNA+containing+8-Oxo-7,8-dihydroguanosine+(8-oxoG)+by+the+exoribonuclease+Xrn-1.">Processing of RNA containing 8-Oxo-7,8-dihydroguanosine (8-oxoG) by the exoribonuclease Xrn-1.</a> Frontiers in Molecular Biosciences. 8, 780315 (2021).</li><li>Francis, A. J., Resendiz, M. J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protocol+for+the+solid-phase+synthesis+of+oligomers+of+RNA+containing+a+2'-O-thiophenylmethyl+modification+and+characterization+via+circular+dichroism.">Protocol for the solid-phase synthesis of oligomers of RNA containing a 2'-O-thiophenylmethyl modification and characterization via circular dichroism.</a> Journal of Visualized Experiments: JoVE. (125), e56189 (2017).</li><li>Langeberg, C. 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=Biochemical+characterization+of+yeast+Xrn1.">Biochemical characterization of yeast Xrn1.</a> Biochemistry. 59 (15), 1493-1507 (2020).</li><li>Stevens, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+and+characterization+of+a+Saccharomyces+cerevisiae+exoribonuclease+which+yields+5'-mononucleotides+by+a+5'+leads+to+3'+mode+of+hydrolysis.">Purification and characterization of a Saccharomyces cerevisiae exoribonuclease which yields 5'-mononucleotides by a 5' leads to 3' mode of hydrolysis.</a> Journal of Biological Chemistry. 255 (7), 3080-3085 (1980).</li><li>Yan, L. L., Simms, C. L., McLoughlin, F., Vierstra, R. D., Zaher, H. 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A., Addepalli, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+damage+to+RNA+is+altered+by+the+presence+of+interacting+proteins+or+modified+nucleosides.">Oxidative damage to RNA is altered by the presence of interacting proteins or modified nucleosides.</a> Frontiers in Molecular Biosciences. 8, 697149 (2021).</li><li>Tomar, 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=DNA+sequence+modulates+the+efficiency+of+NEIL1-catalyzed+excision+of+the+aflatoxin+B1-induced+formamidopyrimidine+guanine+adduct.">DNA sequence modulates the efficiency of NEIL1-catalyzed excision of the aflatoxin B1-induced formamidopyrimidine guanine adduct.</a> Journal of the American Chemical Society. 34 (3), 901-911 (2021).</li><li>Gaffney, A., 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=HIV-1+env-dependent+cell+killing+by+bifunctional+small-molecule/peptide+conjugates.">HIV-1 env-dependent cell killing by bifunctional small-molecule/peptide conjugates.</a> ACS Chemical Biology. 16 (1), 193-204 (2021).</li><li>Sikorski, E. 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The main challenge in this workflow arose between finalizing the experiments and carrying out the mass spectrometric analyses. Experiments were carried out and completed at the University of Colorado Denver and shipped (overnight) to the Colorado State University facilities. Data acquisition was carried out upon receipt, as per convenience. Several unexpected circumstances led to time delays in the process. In one instance, unexpected instrument malfunctions required the samples to be frozen (one time for 21 days) prior ...

MALDI-TOF1,2,3 is a widely used technique for the characterization and/or detection of molecules of varying sizes and characteristics. Some of its uses include diverse applications such as detecting tannins from natural resources4, imaging metabolites in food5, discovery or monitoring of cellular drug targets or markers6, and clinical diagnostics7, to name a few. Of relevance to the present work is the use of MALDI-TOF with DNA or RNA, with its use on oligonucleotides dating back to over three decades8, where several limitations were noted. This technique has now evolved to a reliable, commonly used means to characterize both biopolymers9 and identify/understand chemical and biochemical reactions, e.g., characterization of platinated sites in RNA10, identification of RNA fragments following strand cleavage11,12, or formation of protein-DNA cross-links13. Thus, it is valuable to illustrate and highlight important aspects of using this technique. The basics of MALDI-TOF have been described in video format as well14 and will not be further elaborated herein. Furthermore, its application in a DNA or protein context has been previously described and illustrated in the said format15,16,17.
The protocol for detecting RNA fragments formed after enzymatic hydrolysis is reported herein. The experimental model was chosen based on a recent finding published by our group18, where MALDI-TOF was used to determine the unique reactivity between the exoribonuclease Xrn-1 and oligonucleotides of RNA containing the oxidative lesion 8-oxoG. The 20-nucleotide long strands were obtained via solid-phase synthesis19, [5&#39;-CAU GAA ACA A(8-oxoG)G CUA AAA GU] and [5&#39;-CAU GAA ACA A(8-oxoG)(8-oxoG) CUA AAA GU], while Xrn-1 was expressed and purified following the previously described report20. In brief, Xrn-121 is a 5&#39;-3&#39; exoribonuclease with various key biological roles that degrade multiple types of RNA, including oxidized RNA22. It was found that the processivity of the enzyme stalls upon encountering 8-oxoG, which led to RNA fragments containing 5&#39;-phosphorylated ends [5&#39;-H2PO4-(8-oxoG)G CUA AAA GU], [5&#39;-H2PO4-(8-oxoG)(8-oxoG) CUA AAA GU], and [5&#39;-H2PO4-(8-oxoG) CUA AAA GU]18.
Finally, it is important to note that mass spectrometry is a powerful method that, through various methodologies, can be adapted to other purposes23,24; thus, choosing the right ionization method as well as other experimental set up is of utmost importance.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.6 mL MCT Graduated Violet</td>
			<td>Fisher Scientific</td>
			<td>05-408-127</td>
			<td></td>
		</tr>
		<tr>
			<td>6&#8217;-Trihydroxyacetophenone monohydrate 98%</td>
			<td>Sigma Aldrich</td>
			<td>480-66-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile 99.9%, HPLC grade</td>
			<td>Fisher Scientific</td>
			<td>75-05-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenosine triphosphate, 10 mM</td>
			<td>New Englang Bioscience</td>
			<td>P0756S</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium citrate, dibasic 98%</td>
			<td>Sigma Aldrich</td>
			<td>3012-65-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Fluoride 98.0%, ACS grade</td>
			<td>Alfa Aesar</td>
			<td>12125-01-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Bruker bacterial test standard</td>
			<td>Bruker Daltonics</td>
			<td>8255343</td>
			<td></td>
		</tr>
		<tr>
			<td>Commercial source of Xrn-1</td>
			<td>New England BioLabs</td>
			<td>M0338S</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyl pyrocarbonate, 97%</td>
			<td>ACROS Organics</td>
			<td>A0368487</td>
			<td></td>
		</tr>
		<tr>
			<td>Flex analysis software</td>
			<td>Bruker daltonics</td>
			<td></td>
			<td>FlexAnalysis software version 3.4, Bruker Daltonics</td>
		</tr>
		<tr>
			<td>Lambda 365 UV-vis spectrophotometer</td>
			<td>Perkin Elmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MALDI plate: MSP 96 ground steel target</td>
			<td>Bruker Daltonics</td>
			<td>280799</td>
			<td></td>
		</tr>
		<tr>
			<td>Mass Spectrometer</td>
			<td>Bruker</td>
			<td></td>
			<td>Microflex LRFTOF mass spectrometer (Bruker Daltonics, Billerica, MA)</td>
		</tr>
		<tr>
			<td>Mili-Q IQ 7000</td>
			<td>Milipore Sigma</td>
			<td></td>
			<td>A Mili-Q system was used to purify all water used in this work</td>
		</tr>
		<tr>
			<td>Nanosep Centrifugal Devices with OmegaTM Membrane 10 K, blue (24/pkg)</td>
			<td>Pall Corporation</td>
			<td>OD010C33</td>
			<td>filter media, Omega (modified polyethersulfone) 10 K pore size</td>
		</tr>
		<tr>
			<td>NEBuffer 3</td>
			<td>New England Biolabs</td>
			<td>B7003S</td>
			<td>This is solution B</td>
		</tr>
		<tr>
			<td>Oligo Analyzer tool</td>
			<td>IDT-DNA</td>
			<td></td>
			<td>https://www.idtdna.com/calc/analyzer</td>
		</tr>
		<tr>
			<td>Pipette tips P10</td>
			<td>Fisher Scientific</td>
			<td>02-707-441</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips P200</td>
			<td>Fisher Scientific</td>
			<td>02-707-419</td>
			<td></td>
		</tr>
		<tr>
			<td>RNase Away</td>
			<td>Molecular BioProducts</td>
			<td>7005-11</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 Polynucleotide Kinase</td>
			<td>New England BioLabs</td>
			<td>M0201S</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 Polynucleotide Kinase Reaction Buffer</td>
			<td>New England BioLabs</td>
			<td>B0201S</td>
			<td>This is solution A</td>
		</tr>
		<tr>
			<td>Triflouroacetic Acid</td>
			<td>Alfa Aesar</td>
			<td>76-05-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Xrn-1 exoribonuclease</td>
			<td>Expressed in house</td>
			<td>See ref. 20</td>
			<td></td>
		</tr>
		<tr>
			<td>ZipTip Pipette Tips for Sample preparation</td>
			<td>Millipore</td>
			<td>ZTC 18S 096</td>
			<td>10 &#181;L pipette tips loaded with a C18 standard 0.6 &#181;L bed</td>
		</tr>
	</tbody>
</table>

identification of rna fragments resulting from enzymatic degradation using maldi-tof mass spectrometry

RNA is a biopolymer present in all domains of life, and its interactions with other molecules and/or reactive species, e.g., DNA, proteins, ions, drugs, and free radicals, are ubiquitous. As a result, RNA undergoes various reactions that include its cleavage, degradation, or modification, leading to biologically relevant species with distinct functions and implications. One example is the oxidation of guanine to 7,8-dihydro-8-oxoguanine (8-oxoG), which may occur in the presence of reactive oxygen species (ROS). Overall, procedures that characterize such products and transformations are largely valuable to the scientific community. To this end, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry is a widely used method. The present protocol describes how to characterize RNA fragments formed after enzymatic treatment. The chosen model uses a reaction between RNA and the exoribonuclease Xrn-1, where enzymatic digestion is halted at oxidized sites. Two 20-nucleotide long RNA sequences [5&#39;-CAU GAA ACA A(8-oxoG)G CUA AAA GU] and [5&#39;-CAU GAA ACA A(8-oxoG)(8-oxoG) CUA AAA GU] were obtained via solid-phase synthesis, quantified by UV-vis spectroscopy, and characterized via MALDI-TOF. The obtained strands were then (1) 5&#39;-phosphorylated and characterized via MALDI-TOF; (2) treated with Xrn-1; (3) filtered and desalted; (4) analyzed via MALDI-TOF. This experimental setup led to the unequivocal identification of the fragments associated with the stalling of Xrn-1: [5&#39;-H2PO4-(8-oxoG)G CUA AAA GU], [5&#39;-H2PO4-(8-oxoG)(8-oxoG) CUA AAA GU], and [5&#39;-H2PO4-(8-oxoG) CUA AAA GU]. The described experiments were carried out with 200 picomols of RNA (20 pmol used for MALDI analyses); however, lower amounts may result in detectable peaks with spectrometers using laser sources with more power than the one used in this work. Importantly, the described methodology can be generalized and potentially extended to product identification for other processes involving RNA and DNA, and may aid in the characterization/elucidation of other biochemical pathways.

The oligonucleotides used in this work were synthesized, characterized, and quantified prior to use. The concentration of all oligonucleotides was determined via UV-vis spectroscopy recorded at 90 &#176;C to avoid erroneous readings arising from the potential formation of the secondary structures. Figure 3 displays the spectra of the model oligonucleotides of RNA used in this work, taken at room temperature and after applying heat.
The overall procedure, ...

Watch this Scientific Journal Video about Identification of RNA Fragments Resulting from Enzymatic Degradation using MALDI-TOF Mass Spectrometry at JoVE.com

Identification of RNA Fragments Resulting from Enzymatic Degradation using MALDI-TOF Mass Spectrometry

MALDI-TOF was used to characterize fragments obtained from the reactivity between oxidized RNA and the exoribonuclease Xrn-1. The present protocol describes a methodology that can be applied to other processes involving RNA and/or DNA.

RNA is a biopolymer present in all domains of life, and its interactions with other molecules and/or reactive species, e.g., DNA, proteins, ions, drugs, ...

Mass spectrometry has been widely adopted for various applications. The methodology in this article provides the unequivocal characterization of RNA fragments obtained from an in vitro enzymatic process. Advantages of this technique include that the molecule iron peak is obtained, that the experiments can be carried out with small amounts of material for in vitro applications, and that the protocol can be accomplished with minimal training.The described methodology can be widely applied to study processes involving DNA, RNA, or proteins. Examples include biochemical transformations such as cross information, identification of chemical modifications, or other biopolymer interactions and reactivity. One difficulty can occur from the accessibility to a MALDI spectrometer or core facilities that offer this service.Another aspect is establishing the detection limit which may be higher or lower depending on the instrument. To begin, turn on the UV-Vis spectrophotometer, then click on the PerkinElmer UV WinLab icon to open the instrument operation control window. Turn on the Peltier temperature controller spectrophotometer using the switch located to the instrument's right and click on Scan-Lambda 365, present under Base Methods.Another screen will open and prompt the user to ensure that the cell holders are empty. Click on OK and allow the instrument to conduct its system checks. Now, adjust the scanning parameters by selecting Data Collection.In the new window under Scan Settings, change the start to 350 nanometers and the end to 215 nanometers. Activate the Peltier by selecting the plus to the left of the accessory. Then click on Multiple Cell Peltier, change the temperature degrees Celsius to 25, and click on Peltier On.Navigate to the sample info tab and enter the number of samples, names, and cell position desired.Click on Autozero and insert the cuvette containing the background solution. Click on Start and insert the cuvette in the desired cell and ensure that the cuvette window is oriented parallel to the front face of the instrument. Now, click OK to begin the first scan at 25 degrees Celsius.For measurements at higher temperatures, click on Multiple Cell Peltier, change the temperature to the desired sample temperature and repeat the scanning. Click on File, Export and choose the desired file location and select XY Data to obtain a text file. To perform 5'phosphorylation of RNA, prepare a solution in a 0.6-microliters micro centrifuge tube by adding 33.5-microliters RNase-free water, five microliters of solution A, six microlites of 10 millimolar adenosine triphosphate, one microlite of 200 micromolar RNA aqueous solution, and 4.5-microliters of polynucleotide kinase and mix the solution gently.Incubate the reaction mixture at 37 degrees Celsius for 45 minutes by placing it in a water bath. Then inactivating the enzyme by placing the reaction tube in a heat block, preheated at 65 degrees Celsius for 10 minutes. Allow the solution to cool to room temperature to yield a final 5'phosphorylated RNA solution.After incubation, use 50-microliters of this solution, add five microliters of solution B, and five microliters of 1-femtomole solution of Xrn-1 to perform RNA hydrolysis. Incubate the reaction tube at room temperature for two hours. Transfer this reaction mixture to a 10-kilodalton pore-sized centrifugal device and filter the enzymes by centrifuging for 10 minutes at 700 times G.Transfer the filtrate into a 0.6-milliliter centrifuge tube.Then, add 20-microliters of RNase-free water to wash the residual RNA on the centrifugal tube, followed by centrifugation. Finally, combine this filtrate with the resultant filtrate obtained previously by centrifugation in 10-kilodaltons pore-sized centrifugal device, and freeze the solution at zero degrees Celsius or ship for analysis. To desalt and concentrate the sample, use commercially available cation exchange C18 pipette tips loaded with a bed of C18 chromatography media at its end.For this, position the 10-microliter pipette tip onto a 10-microliter pipette and wash this tip twice with 50%aqueous acetyl nitrile solution. Discard the used volumes into a separate waste tube each time and equilibrate the C18 tip with 10-microliters of 0.1%aqueous trifluoroacetic acid solution two times. Manually remove the C18 tip from the pipette and secure it onto a 200-microliter pipette containing a P200 pipette tip.Then immerse the C18 tip into the resulting solution prepared during hydrolysis of oligonucleotides of RNA by Xrn-1 and aspirate release the solution through the C18 tip 10 times. Now, detach the C18 tip from the P200 pipette, position it down to a 10-microliter pipette and wash the C18 tip using an aqueous solution of 0.1%trifluoroacetic acid solution twice. Discard the used volumes into a separate waste tube each time.Wash the C18 tip with 10-microliters RNase-free water two times. For spotting onto the MALDI plate, elute the RNA oligonucleotide from the C18 tip by immersing the sample into the desired matrix and dispensing the solution back into the tube 10 times. Pipette out this solution onto two separate spots of one microliter each on the plate and allow spots to air dry.The concentration of RNA used in this work was determined via UV-Visible spectroscopy recorded at 90 degrees Celsius to avoid erroneous readings arising from the potential formation of the secondary structures. The overall sequence of events included two parts. One, the efficient 5'phosphorylation of RNA, evidenced by the appearance of only one peak corresponding to the expected product.And two, the stalling fragment arising from the treatment of the sample mixture with Xrn-1. The same results were obtained using a different sequence that contained two oxidative lesions. Potential changes to consider include eliminating the use of the filtering device or considering different matrices for MALDI spotting.For example, sinapinic acid or picolinic acid. The RNA fragments were obtained from an enzymatic process. This process was established by coupling MALDI, electrophoretic analysis, solid-phase synthesis, and circular dichroism.The described protocol has a potential to be used in various fields, from research in the chemical sciences to applications in the biomedical field.

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3.1K vistas.  University of Colorado, Denver. La espectrometría de masas ha sido ampliamente adoptada para diversas aplicaciones. La metodología de este artículo proporciona la caracterización inequívoca de fragmentos de ARN obtenidos a partir de un proceso enzimático in vitro. Las ventajas de esta técnica incluyen que se obtiene el pico de hierro de la molécula, que los experimentos se pueden llevar a cabo con pequeñas cantidades de material para aplicaciones in vitro y que el protocolo se puede lograr con un entrenamiento mín...