This research was supported in part by Grants-in-Aid for Scientific Research for challenging exploratory research (J.K.), and Scientific Research (A) (J.K. and S.M.) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. A RIKEN FPR fellowship (R.C.E.) provided additional support. The authors express their gratitude to Drs. Eisuke Chikayama, Yasuyo Sekiyama and Mami Okamoto for technical assistance with NMR and statistical analyses.

1. Filter Preparation to Remove Extractables
<ol>
 <li>Use 25-mm diameter 0.22 &mu;m pore-size Durapore PVDF hydrophilic filters (Millipore). Place filters in a clean 500 ml Pyrex beaker using tweezers. Pre-rinse three times with distilled water. Swirl well as you rinse to prevent the filters from sticking to each other. Add 300 ml Milli-Q (Millipore) or equivalent high-quality water. Autoclave to facilitate complete removal of extractables from the filters. </li>
 <li>Pour off the Milli-Q and again triple rinse the filters, this time with Milli-Q. Using tweezers place individual filters on a clean dry surface (such as aluminum foil) and either dry at a reasonable temperature (e.g. 37 &deg;C) or air dry. The filters are now ready to use.</li>
</ol>
2. Filtration of Sample Material
<ol>
 <li>For demonstrating this protocol, a Millipore stainless steel 3-place filter manifold with 25-mm microanalysis filter columns with glass supports and a mechanical pump are used. Using aseptic technique, place a single 25-mm filter on the filter column base, apply the column and clamp together.</li>
 <li>Load 15 ml of sample to the column, open the stop-valve on the filter manifold, and turn on the pump. Filter under gentle pressure to minimize cell breakage (&lt;5 kPa). Other pumps, such as hand or a peristaltic pump may be adapted to this protocol. For lower density samples, successive additions of water may be necessary, do not let the filter go dry for an extended period of time between additions of water.</li>
 <li>For marine samples, after you have filtered your sample, you can perform an optional freshwater rinse to reduce residual paramagnetic ions in your sample and on the filter. This may help with more precise tuning of the spectrometer magnet. Simply gently add a small volume of water and filter through your collected sample at the end.</li>
 <li>Once filtering is finished, turn off the pump, and leave the valve open so there is still negative pressure under the filter. Remove the clamp and filter column.</li>
 <li>With one hand, use clean tweezers to take hold of the filter. Fold the filter across itself, but do not crease. With your other hand use the lip of a sterile 2-ml microcentrifuge tube to hold down the filter. Release the tweezers then use them to re-grip both edges of the filter. Regrip at a 45 &deg; angle to the fold.</li>
 <li>Place the filter into the 2-ml tube and release so it opens with the sample side facing inwards. You can place up to two filters into the sterile 2 ml microcentrifuge tube this way. If using two filters, ensure they overlap as little as possible. Immediately freeze (at least -30 &deg;C).</li>
</ol>
3. Extraction of Aqueous-soluble Metabolites
<ol>
 <li>Lyophilize your samples overnight or for at least 10 hours.</li>
 <li>After lyophilization, add a stainless steel crusher to each tube (Tokken). Add 750 &mu;l standardized potassium phosphate NMR buffer in deuterium oxide (2H &gt; 90%) with 2,2-Dimethyl-2-silapentane-5-sulfonate (DSS) standard (KPi; 38.3 mM KH2PO4, 61.7 mM K2HPO4, DSS 0.1 mM, pH 7.0, 90% D2O)2.</li>
 <li>Sonicate the samples for 5 minutes at 4 &deg;C in a water sonicator (Bioruptor, Diagenode) to remove the cell material from the filter. Remove the filters with clean tweezers.</li>
 <li>Disrupt the cells using a mill crusher (1600 rpm) for 5 minutes.</li>
 <li>Incubate at 65 &deg;C with shaking (1400 rpm) on a bench-top shaker (Eppendorf) for 15 minutes.</li>
 <li>Remove the metal pig with clean tweezers, and centrifuge the sample at 13,000 g for 5 minutes.</li>
 <li>Draw off the supernatant directly to an NMR tube for NMR spectroscopy.</li>
</ol>
4. NMR Spectroscopy and Data Analysis
<ol>
 <li>Load your sample into a NMR spectrometer (here, a Bruker DRX-500 spectrometer equipped with TXI probe with triple-axis gradient controlled by a computer running XWIN-NMR).</li>
 <li>Obtain 1D 1H NMR spectra using appropriate previously published methods2,15 from the XWIN-NMR interface. In the present study 1H NMR spectra were recorded on a DRX-500 spectrometer operating at 500.03 MHz at 298 K. Residual water signals were suppressed by the Watergate pulse sequence, with a repetition time of 1.2 s. 128 transients were collected to obtain 32,000 data points per spectrum.</li>
 <li>Transfer the NMR data directories to a PC installed NMRPipe software16. Process the raw data and set DSS as 0 ppm reference then manually phase the spectra. Digitize the spectral data into a set of discrete values by integrating or 'binning' them with software such as rNMR, Automics, or using the publicly available FT2B package from the ECOMICS web site (<a href="https://database.riken.jp/ecomics/">https://database.riken.jp/ecomics/</a>)3,17. In this example, spectra were integrated between 0.5 and 10.5 ppm over 0.032 ppm integral regions using ECOMICS, and normalized to either DSS or total signal intensity. Output data can now be used for downstream statistical analysis such as principal components analysis (PCA) using free software packages like R18.</li>
</ol>
5. Representative Results
An example of 1H NMR spectra obtained using the above methods are shown in Figure 1. These samples, from two time points of a microcosm experiment show clear differences due to algal metabolic activities. The day 4 spectrum shows considerable abundance of peaks, particularly in the 3-4 ppm range compared to the day 1 sample. These peaks can be attributed to sugars produced by blooming diatoms within the microcosm. In a similar experiment comparing the growth of natural plankton communities in artificial or natural seawater, statistical approaches such as principal component analysis (PCA) score plot derived from binned NMR spectra can be used to show clear metabolic differences between the two treatments (Fig. 2), while the loading plots can identify peaks within the spectra that shape the distribution of the data. Such results can be compared with data from other omics levels, such as from genomic fingerprinting methods (Fig. 3). These NMR peaks can be queried individually (e.g. at the BMRB; <a href="http://www.bmrb.wisc.edu/">http://www.bmrb.wisc.edu/</a>)19, or entire spectra can be analyzed statistically (e.g. with SpinAssign at <a href="http://prime.psc.riken.jp/?action=nmr_search">http://prime.psc.riken.jp/?action=nmr_search</a>)2. In this example, differences between treatments were due to an abundance of peaks in the sugars region (3.39 ppm to 4.04 ppm) of spectra from natural plankton community metabolites, and several peaks characteristic to the artificial seawater communities were tentatively identified as lactate and formate using SpinAssign.
<img src="/files/ftp_upload/3163/3163fig1.jpg" alt="Figure 1" /> 
Figure 1. Representative 1H NMR spectra obtained from samples processed using this procedure. Microcosm samples were taken before (day 1) and during (day 4) an intense diatom bloom. NMR experiments were performed on a Bruker DRX-500 with signals normalized to the internal standard peak height (DSS; 0 ppm).
<img src="/files/ftp_upload/3163/3163fig2.jpg" alt="Figure 2" /> 
Figure 2. Principal component analysis (PCA) score plot for binned NMR spectra from metabolomes of naturally-derived microbial planktonic communities grown in microcosms with natural (open diamonds) or artificial (black circles) seawater. Clear metabolic differences can be observed in the scatterplot. A loading plot from such an analysis can then be used to identify distinct peaks of importance in the system; these peaks can be further analyzed as needed.
<img src="/files/ftp_upload/3163/3163fig3.jpg" alt="Figure 3" /> 
Figure 3. An example of multi-omics analysis combining NMR with genomic data. Community composition based on denaturing gradient gel electrophoresis of 18S (left) and 16S (right) rRNA genes from the same samples as analyzed in Figure 2 also shows distinct microbial community patterns between natural (open diamonds) and artificial (black circles) seawater microcosms. Such correspondence between metabolome and genome from natural systems demonstrates the usefulness of this approach.

<ol>
	<li>Bundy, J. G., Davey, M. P., Viant, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environmental+metabolomics:+a+critical+review+and+future+perspectives.">Environmental metabolomics: a critical review and future perspectives.</a> Metabolomics. 5, 3-21 (2008).</li><li>Chikayama, E., 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=Statistical+indices+for+simultaneous+large-scale+metabolite+detections+for+a+single+NMR+spectrum.">Statistical indices for simultaneous large-scale metabolite detections for a single NMR spectrum.</a> Anal. Chem. 82, 1653-1658 (2010).</li><li>Lewis, I. A., Schommer, S. C., Markley, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=rNMR:+open+source+software+for+identifying+and+quantifying+metabolites+in+NMR+spectra.">rNMR: open source software for identifying and quantifying metabolites in NMR spectra.</a> Magn. Reson. Chem. 47, S123-S126 (2009).</li><li>Li, M., 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=Symbiotic+gut+microbes+modulate+human+metabolic+phenotypes.">Symbiotic gut microbes modulate human metabolic phenotypes.</a> Proc. Natl. Acad. Sci. U.S.A. 105, 2117-2122 (2008).</li><li>Mochida, K., Furuta, T., Ebana, K., Shinozaki, K., Kikuchi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+exploration+of+metabolic+and+genomic+diversity+in+rice.">Correlation exploration of metabolic and genomic diversity in rice.</a> BMC Genomics. 10, 568 (2009).</li><li>Fukuda, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bifidobacteria+can+protect+from+enteropathogenic+infection+through+production+of+acetate.">Bifidobacteria can protect from enteropathogenic infection through production of acetate.</a> Nature. 469, 543-547 (2011).</li><li>Kikuchi, J., Hirayama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Practical+aspects+of+stable+isotope+labeling+of+higher+plants+for+a+hetero-nuclear+multi-dimensional+NMR-based+metabolomics.">Practical aspects of stable isotope labeling of higher plants for a hetero-nuclear multi-dimensional NMR-based metabolomics.</a> Methods Mol. Biol. 358, 273-286 (2007).</li><li>Martin, F. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+top-down+systems+biology+view+of+microbiome-mammalian+metabolic+interactions+in+a+mouse+model.">A top-down systems biology view of microbiome-mammalian metabolic interactions in a mouse model.</a> Mol. Syst. Biol. 3, 112 (2007).</li><li>Mahrous, E. A., Lee, R. B., Lee, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+approach+to+lipid+profiling+of+mycobacteria+using+2D+HSQC+NMR+maps.">A rapid approach to lipid profiling of mycobacteria using 2D HSQC NMR maps.</a> J. Lipid Res. 49, 455-463 (2008).</li><li>Fukuda, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+and+characterization+of+bacterial+metabolic+dynamics+with+a+novel+profiling+technique,+real-time+metabolotyping.">Evaluation and characterization of bacterial metabolic dynamics with a novel profiling technique, real-time metabolotyping.</a> PloS ONE. 4, e4893 (2009).</li><li>Date, 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=New+monitoring+approach+for+metabolic+dynamics+in+microbial+ecosystems+using+stable-isotope-labeling+technologies.">New monitoring approach for metabolic dynamics in microbial ecosystems using stable-isotope-labeling technologies.</a> J. Biosci. Bioeng. 110, 87-93 (2010).</li><li>Nakanishi, 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=Dynamic+omics+approach+identifies+nutrition-mediated+microbial+interactions.">Dynamic omics approach identifies nutrition-mediated microbial interactions.</a> J. Proteome Res. 10, 824-836 (2011).</li><li>Falkowski, P., Barber, R., Smetacek, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biogeochemical+controls+and+feedbacks+on+ocean+primary+production.">Biogeochemical controls and feedbacks on ocean primary production.</a> Science. 281, 200-207 (1998).</li><li>Viant, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolomics+of+aquatic+organisms:+the+new+'omics'+on+the+block.">Metabolomics of aquatic organisms: the new 'omics' on the block.</a> Mar. Ecol. Prog. Ser. 332, 301-306 (2007).</li><li>Sekiyama, Y., Chikayama, E., Kikuchi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+semipolar+solvent+system+as+a+step+toward+heteronuclear+multidimensional+NMR-based+metabolomics+for+13C-labeled+bacteria,+plants,+and+animals.">Evaluation of a semipolar solvent system as a step toward heteronuclear multidimensional NMR-based metabolomics for 13C-labeled bacteria, plants, and animals.</a> Anal. Chem. 83, 719-726 (2011).</li><li>Delaglio, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMRPipe:+A+multidimensional+spectral+processing+system+based+on+UNIX+pipes.">NMRPipe: A multidimensional spectral processing system based on UNIX pipes.</a> J. Biomol. NMR. 6, 277-293 (1995).</li><li>Wang, 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=Automics:+an+integrated+platform+for+NMR-based+metabonomics+spectral+processing+and+data+analysis.">Automics: an integrated platform for NMR-based metabonomics spectral processing and data analysis.</a> BMC Bioinformatics. 10, 83 (2009).</li><li>Eldon, L., 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=BioMagResBank.">BioMagResBank.</a> Nucleic Acids Res. 36, D402-D408 (2007).</li><li>Sekiyama, Y., Chikayama, E., Kikuchi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Profiling+polar+and+semipolar+plant+metabolites+throughout+extraction+processes+using+a+combined+solution-state+and+high-resolution+magic+angle+spinning+NMR+approach.">Profiling polar and semipolar plant metabolites throughout extraction processes using a combined solution-state and high-resolution magic angle spinning NMR approach.</a> Anal. Chem. 82, 1643-1652 (2011).</li></ol>

No conflicts of interest declared.

The filtration and metabolite extraction method demonstrated here allows for microbial planktonic biomass to be collected in sufficient amount for NMR metabolomics. While only extraction of aqueous-soluble metabolites using KPi and 1D 1H NMR is demonstrated, other extraction solvents and spectroscopic approaches can be used. One useful example is the use of deuterated methanol as a semi-polar solvent, which has been shown to produce superior NMR spectra from heterogeneous samples and is less sensitive to conta...

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>0.22 &mu;m hydrophilic Durapore PVDF filters, 25 mm</td>
			<td>Millipore </td>
			<td>GVWP02500</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Microanalysis Filter Holder, 25 mm, fritted glass support</td>
			<td>Millipore</td>
			<td>XX1002500</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>3-place manifold, 47 mm, stainless steel</td>
			<td>Millipore</td>
			<td>XX2504735</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Wako</td>
			<td>169-04245</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>Wako</td>
			<td>164-04295</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Deuterium oxide, 2H &gt; 90%</td>
			<td>Campridge Isotope Laboratoties</td>
			<td>DLM-4</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>DSS</td>
			<td>Fluka</td>
			<td>92754</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Automill</td>
			<td>Tokken</td>
			<td>TK-AM4</td>
			<td>Stainless steel crushers included</td>
		</tr>
		<tr>
			<td>Thermomixer comfort</td>
			<td>Eppendorf</td>
			<td>5355 000.011</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Bioruptor</td>
			<td>Diagenode</td>
			<td>UCD-200</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Vacuum evaporator</td>
			<td>EYELA</td>
			<td>CVE-3100</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NMR</td>
			<td>Bruker </td>
			<td>DRX-500 with 5 mm-TXI probe</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Spectral binning tool</td>
			<td>Originally developed</td>
			<td>FT2DB</td>
			<td><a href="https://database.riken.jp/ecomics/">https://database.riken.jp/ecomics/</a></td>
		</tr>
		<tr>
			<td>Metabolite annotation tool and database</td>
			<td>Originally developed</td>
			<td>SpinAssign</td>
			<td><a href="http://prime.psc.riken.jp/?action=nmr_search">http://prime.psc.riken.jp/?action=nmr_search</a></td>
		</tr>
	</tbody>
</table>

concentration of metabolites from low-density planktonic communities for environmental metabolomics using nuclear magnetic resonance spectroscopy

Environmental metabolomics is an emerging field that is promoting new understanding in how organisms respond to and interact with the environment and each other at the biochemical level1. Nuclear magnetic resonance (NMR) spectroscopy is one of several technologies, including gas chromatography&#x2013;mass spectrometry (GC-MS), with considerable promise for such studies. Advantages of NMR are that it is suitable for untargeted analyses, provides structural information and spectra can be queried in quantitative and statistical manners against recently available databases of individual metabolite spectra2,3. In addition, NMR spectral data can be combined with data from other omics levels (e.g. transcriptomics, genomics) to provide a more comprehensive understanding of the physiological responses of taxa to each other and the environment4,5,6. However, NMR is less sensitive than other metabolomic techniques, making it difficult to apply to natural microbial systems where sample populations can be low-density and metabolite concentrations low compared to metabolites from well-defined and readily extractable sources such as whole tissues, biofluids or cell-cultures. Consequently, the few direct environmental metabolomic studies of microbes performed to date have been limited to culture-based or easily defined high-density ecosystems such as host-symbiont systems, constructed co-cultures or manipulations of the gut environment where stable isotope labeling can be additionally used to enhance NMR signals7,8,9,10,11,12. Methods that facilitate the concentration and collection of environmental metabolites at concentrations suitable for NMR are lacking. Since recent attention has been given to the environmental metabolomics of organisms within the aquatic environment, where much of the energy and material flow is mediated by the planktonic community13,14, we have developed a method for the concentration and extraction of whole-community metabolites from planktonic microbial systems by filtration. Commercially available hydrophilic poly-1,1-difluoroethene (PVDF) filters are specially treated to completely remove extractables, which can otherwise appear as contaminants in subsequent analyses. These treated filters are then used to filter environmental or experimental samples of interest. Filters containing the wet sample material are lyophilized and aqueous-soluble metabolites are extracted directly for conventional NMR spectroscopy using a standardized potassium phosphate extraction buffer2. Data derived from these methods can be analyzed statistically to identify meaningful patterns, or integrated with other omics levels for comprehensive understanding of community and ecosystem function.

Watch this Scientific Journal Video about Concentration of Metabolites from Low-density Planktonic Communities for Environmental Metabolomics using Nuclear Magnetic Resonance Spectroscopy at JoVE.com

Concentration of Metabolites from Low-density Planktonic Communities for Environmental Metabolomics using Nuclear Magnetic Resonance Spectroscopy

A method for metabolite extraction from microbial planktonic communities is presented. Whole community sampling is achieved by filtration onto specially prepared filters. After lyophilization, aqueous-soluble metabolites are extracted. This approach allows for application of environmental metabolomics to trans-omics investigations of natural or experimental microbial communities.

Environmental metabolomics is an emerging field that is promoting new understanding in how organisms respond to and interact with the environment and each ...

concentration-metabolites-from-low-density-planktonic-communities-for

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12.7K Views.  RIKEN Advanced Science Institute. A method for metabolite extraction from microbial planktonic communities is presented. Whole community sampling is achieved by filtration onto specially prepared filters. After lyophilization, aqueous-soluble metabolites are extracted. This approach allows for application of environmental metabolomics to trans-omics investigations of natural or experimental microbial communities.

Video: Concentration of Metabolites from Low-density Planktonic Communities for Environmental Metabolomics using Nuclear Magnetic Resonance Spectroscopy

Microbial Communities in Nature and Laboratory - Interview

In vitro Labeling of Human Embryonic Stem Cells for Magnetic Resonance Imaging

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of the predominant imaging modalities to assess the restoration of the injured myocardium. Furthermore, ex-vivo labeling agents, such as iron-oxide nanoparticles, have been employed to track and localize the transplanted stem cells. However, this method does not monitor a fundamental cellular biology property regarding the viability of transplanted cells. It has been known that manganese chloride (MnCl2) enters the cells via voltage-gated calcium (Ca2+) channels when the cells are biologically active, and accumulates intracellularly to generate T1 shortening effect. Therefore, we suggest that manganese-guided MRI can be useful to monitor cell viability after the transplantation of hESC into the myocardium.
In this video, we will show how to label hESC with MnCl2 and how those cells can be clearly seen by using MRI in vitro. At the same time, biological activity of Ca2+-channels will be modulated utilizing both Ca2+-channel agonist and antagonist to evaluate concomitant signal changes.

In this video, we are showing how to label human embryonic stem cells (hESC) with manganese chloride (MnCl2) which can enter cells via voltage-gated calcium channels when the cells are biologically active. Additionally, we show the use of MnCl2 as cellular MRI contrast agent to determine the in vitro viability of hESC.

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of ...

Analyzing Gene Expression from Marine Microbial Communities using Environmental Transcriptomics

Analogous to metagenomics, environmental transcriptomics (metatranscriptomics) retrieves and sequences environmental mRNAs from a microbial assemblage without prior knowledge of what genes the community might be expressing. Thus it provides the most unbiased perspective on community gene expression in situ. Environmental transcriptomics protocols are technically difficult since prokaryotic mRNAs generally lack the poly(A) tails that make isolation of eukaryotic messages relatively straightforward 1 and because of the relatively short half lives of mRNAs 2. In addition, mRNAs are much less abundant than rRNAs in total RNA extracts, thus an rRNA background often overwhelms mRNA signals. However, techniques for overcoming some of these difficulties have recently been developed. A procedure for analyzing environmental transcriptomes by creating clone libraries using random primers to reverse-transcribe and amplify environmental mRNAs was recently described was successful in two different natural environments, but results were biased by selection of the random primers used to initiate cDNA synthesis 3. Advances in linear amplification of mRNA obviate the need for random primers in the amplification step and make it possible to use less starting material decreasing the collection and processing time of samples and thereby minimizing RNA degradation 4. In vitro transcription methods for amplifying mRNA involve polyadenylating the mRNA and incorporating a T7 promoter onto the 3 end of the transcript. Amplified RNA (aRNA) can then be converted to double stranded cDNA using random hexamers and directly sequenced by pyrosequencing 5. A first use of this method at Station ALOHA demonstrated its utility for characterizing microbial community gene expression 6.

We present a method for generating cDNA from environmental mRNA. In general, total RNA is first collected from the environment, rRNA is selectively removed, mRNA is selectively amplified, and cDNA synthesized from the enriched mRNA pool is sequenced. Recovered sequences can be annotated using standard bioinformatics techniques to identify the expressed genes.

Analogous to metagenomics, environmental transcriptomics (metatranscriptomics) retrieves and sequences environmental mRNAs from a microbial assemblage ...

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps

Reactive nitrogen/oxygen species (ROS/RNS) at low concentrations play an important role in regulating cell function, signaling, and immune response but in unregulated concentrations are detrimental to cell viability1, 2. While living systems have evolved with endogenous and dietary antioxidant defense mechanisms to regulate ROS generation, ROS are produced continuously as natural by-products of normal metabolism of oxygen and can cause oxidative damage to biomolecules resulting in loss of protein function, DNA cleavage, or lipid peroxidation3, and ultimately to oxidative stress leading to cell injury or death4. 
Superoxide radical anion (O2&bull;-) is the major precursor of some of the most highly oxidizing species known to exist in biological systems such as peroxynitrite and hydroxyl radical. The generation of O2&bull;- signals the first sign of oxidative burst, and therefore, its detection and/or sequestration in biological systems is important. In this demonstration, O2&bull;- was generated from polymorphonuclear neutrophils (PMNs). Through chemotactic stimulation with phorbol-12-myristate-13-acetate (PMA), PMN generates O2&bull;- via activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase5. 
Nitric oxide (NO) synthase which comes in three isoforms, as inducible-, neuronal- and endothelial-NOS, or iNOS, nNOS or eNOS, respectively, catalyzes the conversion of L- arginine to L-citrulline, using NADPH to produce NO6. Here, we generated NO from endothelial cells. Under oxidative stress conditions, eNOS for example can switch from producing NO to O2&bull;- in a process called uncoupling, which is believed to be caused by oxidation of heme7 or the co-factor, tetrahydrobiopterin (BH4)8.
There are only few reliable methods for the detection of free radicals in biological systems but are limited by specificity and sensitivity. Spin trapping is commonly used for the identification of free radicals and involves the addition reaction of a radical to a spin trap forming a persistent spin adduct which can be detected by electron paramagnetic resonance (EPR) spectroscopy. The various radical adducts exhibit distinctive spectrum which can be used to identify the radicals being generated and can provide a wealth of information about the nature and kinetics of radical production9.
The cyclic nitrones, 5,5-dimethyl-pyrroline-N-oxide, DMPO10, the phosphoryl-substituted DEPMPO11, and the ester-substituted, EMPO12 and BMPO13, have been widely employed as spin traps--the latter spin traps exhibiting longer half-lives for O2&bull;- adduct. Iron (II)-N-methyl-D-glucamine dithiocarbamate, Fe(MGD)2 is commonly used to trap NO due to high rate of adduct formation and the high stability of the spin adduct14.

Electron paramagnetic resonance (EPR) spectroscopy was employed to detect nitric oxide from bovine aortic endothelial cells and superoxide radical anion from human neutrophils using iron (II)-N-methyl-D-glucamine dithiocarbamate, Fe(MGD)2 and 5,5-dimethyl-1-pyroroline-N-oxide, DMPO, respectively.

Reactive nitrogen/oxygen species (ROS/RNS) at low concentrations play an important role in regulating cell function, signaling, and immune response but in ...

Quantifying Mixing using Magnetic Resonance Imaging

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device.
 Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media 1, 2. The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile 1H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products.

Magnetic resonance imaging (MRI) provides a powerful tool to evaluate the effectiveness of process equipment during operation. We discuss the use of MRI to visualize mixing in a static mixer. The application is relevant to personal care products, but can be applied to a broad range of food, chemical, biomass and biological fluids.

Mixing is a unit operation that combines two or more components into a homogeneous mixture.  This work involves mixing two viscous liquid streams using an ...

Purification of Transcripts and Metabolites from Drosophila Heads

For the last decade, we have tried to understand the molecular and cellular mechanisms of neuronal degeneration using Drosophila as a model organism. Although fruit flies provide obvious experimental advantages, research on neurodegenerative diseases has mostly relied on traditional techniques, including genetic interaction, histology, immunofluorescence, and protein biochemistry. These techniques are effective for mechanistic, hypothesis-driven studies, which lead to a detailed understanding of the role of single genes in well-defined biological problems. However, neurodegenerative diseases are highly complex and affect multiple cellular organelles and processes over time. The advent of new technologies and the omics age provides a unique opportunity to understand the global cellular perturbations underlying complex diseases. Flexible model organisms such as Drosophila are ideal for adapting these new technologies because of their strong annotation and high tractability. One challenge with these small animals, though, is the purification of enough informational molecules (DNA, mRNA, protein, metabolites) from highly relevant tissues such as fly brains. Other challenges consist of collecting large numbers of flies for experimental replicates (critical for statistical robustness) and developing consistent procedures for the purification of high-quality biological material. Here, we describe the procedures for collecting thousands of fly heads and the extraction of transcripts and metabolites to understand how global changes in gene expression and metabolism contribute to neurodegenerative diseases. These procedures are easily scalable and can be applied to the study of proteomic and epigenomic contributions to disease.

Purification of Transcripts and Metabolites from Drosophila Heads

We describe here the procedures for the extraction and purification of mRNA and metabolites from Drosophila heads. We are applying these techniques to better understand the cellular perturbations underlying neuronal degeneration. These methodologies can be easily scaled and adapted for other "omic" projects.

For the last decade, we have tried to understand the molecular and cellular mechanisms of neuronal degeneration using Drosophila as a model organism. ...

Removal of Exogenous Materials from the Outer Portion of Frozen Cores to Investigate the Ancient Biological Communities Harbored Inside

The cryosphere offers access to preserved organisms that persisted under past environmental conditions. In fact, these frozen materials could reflect conditions over vast time periods and investigation of biological materials harbored inside could provide insight of ancient environments. To appropriately analyze these ecosystems and extract meaningful biological information from frozen soils and ice, proper collection and processing of the frozen samples is necessary. This is especially critical for microbial and DNA analyses since the communities present may be so uniquely different from modern ones. Here, a protocol is presented to successfully collect and decontaminate frozen cores. Both the absence of the colonies used to dope the outer surface and exogenous DNA suggest that we successfully decontaminated the frozen cores and that the microorganisms detected were from the material, rather than contamination from drilling or processing the cores.

The cryosphere offers access to preserved organisms that persisted under past environmental conditions. A protocol is presented to collect and decontaminate permafrost cores of soils and ice. The absence of exogenous colonies and DNA suggest that microorganisms detected represent the material, rather than contamination from drilling or processing.

The cryosphere offers access to preserved organisms that persisted under past environmental conditions. In fact, these frozen materials could reflect ...

Experimental Protocol for Using Drosophila As an Invertebrate Model System for Toxicity Testing in the Laboratory

Emergent properties and external factors (population-level and ecosystem-level interactions, in particular) play important roles in mediating ecologically-important endpoints, though they are rarely considered in toxicological studies. D. melanogaster is emerging as a toxicology model for the behavioral, neurological, and genetic impacts of toxicants, to name a few. More importantly, species in the genus Drosophila can be utilized as a model system for an integrative framework approach to incorporate emergent properties and answer ecologically-relevant questions in&#160;toxicology research. The aim of this paper is to provide a protocol for exposing species in the genus Drosophila to pollutants to be used as a model system for a range of phenotypic outputs and ecologically-relevant questions. More specifically, this protocol can be used to 1) link multiple biological levels of organization and understand the impact of toxicants on both individual- and population-level fitness; 2) test the impact of toxicants at different stages of developmental exposure; 3) test multigenerational and evolutionary implications of pollutants; and 4) test multiple contaminants and stressors simultaneously.

Experimental Protocol for Using Drosophila As an Invertebrate Model System for Toxicity Testing in the Laboratory

In this paper, we provide a detailed protocol for exposing species in the genus Drosophila to pollutants with the goal of studying the impact of exposure on a range of phenotypic outputs at different developmental stages and for more than one generation.

Emergent properties and external factors (population-level and ecosystem-level interactions, in particular) play important roles in mediating ...

Synthesis of 68Ga Core-doped Iron Oxide Nanoparticles for Dual Positron Emission Tomography /(T1)Magnetic Resonance Imaging

Here, we describe a microwave synthesis to obtain iron oxide nanoparticles core-doped with 68Ga. Microwave technology enables fast and reproducible synthetic procedures. In this case, starting from FeCl3 and citrate trisodium salt, iron oxide nanoparticles coated with citric acid are obtained in 10 min in the microwave. These nanoparticles present a small core size of 4.2 &#177; 1.1 nm and a hydrodynamic size of 7.5 &#177; 2.1 nm. Moreover, they have a high longitudinal relaxivity (r1) value of 11.9 mM-1&#183;s-1 and a modest transversal relaxivity value (r2) of 22.9 mM-1&#183;s-1, which results in a low r2/r1 ratio of 1.9. These values enable positive contrast generation in magnetic resonance imaging (MRI) instead of negative contrast, commonly used with iron oxide nanoparticles. In addition, if a 68GaCl3 elution from a 68Ge/68Ga generator is added to the starting materials, a nano-radiotracer doped with 68Ga is obtained. The product is obtained with a high radiolabeling yield (&#62; 90%), regardless of the initial activity used. Furthermore, a single purification step renders the nano-radiomaterial ready to be used in vivo.

Synthesis of 68Ga Core-doped Iron Oxide Nanoparticles for Dual Positron Emission Tomography /T1Magnetic Resonance Imaging

Here, we present a protocol to obtain 68Ga core-doped iron oxide nanoparticles via fast microwave-driven synthesis. The methodology renders PET/(T1)MRI nanoparticles with radiolabeling efficiencies higher than 90% and radiochemical purity of 99% in a 20-min synthesis.

Here, we describe a microwave synthesis to obtain iron oxide nanoparticles core-doped with 68Ga. Microwave technology enables fast and reproducible ...

Quasi-metagenomic Analysis of Salmonella from Food and Environmental Samples

Quasi-metagenomics sequencing refers to the sequencing-based analysis of modified microbiomes of food and environmental samples. In this protocol, microbiome modification is designed to concentrate genomic DNA of a target foodborne pathogen contaminant to facilitate the detection and subtyping of the pathogen in a single workflow. Here, we explain and demonstrate the sample preparation steps for the quasi-metagenomics analysis of Salmonella enterica from representative food and environmental samples including alfalfa sprouts, ground black pepper, ground beef, chicken breast and environmental swabs. Samples are first subjected to the culture enrichment of Salmonella for a shortened and adjustable duration (4&#8211;24 h). Salmonella cells are then selectively captured from the enrichment culture by immunomagnetic separation (IMS). Finally, multiple displacement amplification (MDA) is performed to amplify DNA from IMS-captured cells. The DNA output of this protocol can be sequenced by high throughput sequencing platforms. An optional quantitative PCR analysis can be performed to replace sequencing for Salmonella detection or assess the concentration of Salmonella DNA before sequencing.

Quasi-metagenomic Analysis of Salmonella from Food and Environmental Samples

Here, we present a protocol to prepare DNA samples from food and environmental microbiomes for concerted detection and subtyping of Salmonella through quasimetagenomic sequencing. The combined use of culture enrichment, immunomagnetic separation (IMS), and multiple displacement amplification (MDA) allows effective concentration of Salmonella genomic DNA from food and environmental samples.&#160;