Name: quantifying plant soluble protein and digestible carbohydrate content, using corn (zea mays) as an exemplar
Uploaded: 2018-08-06T14:30:00
Description: Watch this Scientific Journal Video about Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn Zea mays As an Exemplar at JoVE.com

Thanks to all of our collaborators who have assisted with sweet corn field collections, including Dominic Reisig and Dan Mott at North Carolina State University, and Pat Porter at Texas A&#38; M University in Lubbock, TX. Thanks to Fiona Clissold for helping to optimize the protocols and for providing edits to this manuscript. This work was supported in part by the Texas A&#38; M C. Everette Salyer Fellowship (Department of Entomology) and the Biotechnology Risk Assessment Grant Program competitive grant no. 2015-33522-24099 from the U.S. Department of Agriculture (awarded to GAS and STB).

1. Plant Collection and Processing
<ol>
	<li>Collect and process plant samples
	<ol>
		<li>After collecting plant samples, flash-freeze samples by dipping plant material into liquid nitrogen with forceps and store at -80 &#176;C. If the plant samples collected are too large to flash-freeze, quickly cool the samples using dry ice and transfer to a -80 &#176;C freezer as soon as possible. The macronutrient content of plant material can change after tissues are separated from the plant, so it is important to freeze plant ...

<ol>
	<li>Simpson, S. J., Raubenheimer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Nature of Nutrition: A Unifying Framework from Animal Adapation to Human Obesity. , (2012).</li><li>Behmer, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insect+herbivore+nutrient+regulation.">Insect herbivore nutrient regulation.</a> Annual Review of Entomology. 54, 165-187 (2009).</li><li>Epstein, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mineral+nutrition+of+plants:+mechanisms+of+uptake+and+transport.">Mineral nutrition of plants: mechanisms of uptake and transport.</a> Annual Review of Plant Physiology. 7 (1), 1-24 (1956).</li><li>Chapin, F. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mineral+nutrition+of+wild+plants.">The mineral nutrition of wild plants.</a> Annual Review of Ecology, Evolution, and Systematics. 11 (1), 233-260 (1980).</li><li>Marschner, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Marschner's Mineral Nutrition of Higher Plants. , (1956).</li><li>Stieger, P. A., Feller, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Senescence+and+protein+remobilization+in+leaves+of+maturing+wheat+plants+grown+on+waterlogged+soil.">Senescence and protein remobilization in leaves of maturing wheat plants grown on waterlogged soil.</a> Plant and Soil. 166, 173-179 (1994).</li><li>Li, R., Volenec, J. J., Joern, B. C., Cunningham, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seasonal+changes+in+nonstructural+carbohydrates,+protein,+and+macronutrients+in+roots+of+alfalfa,+red+clover,+sweetclover,+and+birdsfoot+trefoil.">Seasonal changes in nonstructural carbohydrates, protein, and macronutrients in roots of alfalfa, red clover, sweetclover, and birdsfoot trefoil.</a> Crop Science. 36, 617-623 (1996).</li><li>S&#225;nchez, E., Rivero, R. M., Ruiz, J. M., Romero, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+biomass,+enzymatic+activity+and+protein+concentration+in+roots+and+leaves+of+green+bean+plants+(Phaseolus+vulgaris+L.+cv.+Strike)+under+high+NH4NO3+application+rates.">Changes in biomass, enzymatic activity and protein concentration in roots and leaves of green bean plants (Phaseolus vulgaris L. cv. Strike) under high NH4NO3 application rates.</a> Scientia Horticulturae. 99, 237-248 (2004).</li><li>Lenhart, P. A., Eubanks, M. D., Behmer, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water+stress+in+grasslands:+Dynamic+responses+of+plants+and+insect+herbivores.">Water stress in grasslands: Dynamic responses of plants and insect herbivores.</a> Oikos. 124, 381-390 (2015).</li><li>Machado, A. R., Arce, C. C. M., Ferrieri, A. P., Baldwin, I. T., Erb, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Jasmonate-dependent+depletion+of+soluble+sugars+compromises+plant+resistance+to+Manduca+sexta.">Jasmonate-dependent depletion of soluble sugars compromises plant resistance to Manduca sexta.</a> New Phytologist. 207, 91-105 (2015).</li><li>Deans, C. A., Behmer, S. T., Fiene, J., Sword, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatio-temporal,+genotypic,+and+environmental+effects+of+plant+soluble+protein+and+digestible+carbohydrate+content:+implications+for+insect+herbivores+with+cotton+as+an+exemplar.">Spatio-temporal, genotypic, and environmental effects of plant soluble protein and digestible carbohydrate content: implications for insect herbivores with cotton as an exemplar.</a> Journal of Chemical Ecology. 42 (11), 1151-1163 (2016).</li><li>Boisen, S., Bech-Andersen, S., Eggum, B. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+view+of+the+conversion+factor+6.25+from+total+nitrogen+to+protein.">A critical view of the conversion factor 6.25 from total nitrogen to protein.</a> Acta Agriculturae Scandinavica. 37, 299-304 (1987).</li><li>Ezeagu, I. E., Petzke, J. K., Metges, C. C., Akinsoyinu, A. O., Ologhobo, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seed+protein+contents+and+nitrogen-to-protein+conversion+factors+for+some+uncultivated+tropical+plant+seeds.">Seed protein contents and nitrogen-to-protein conversion factors for some uncultivated tropical plant seeds.</a> Food Chemistry. 78, 105-109 (2002).</li><li>Izhaki, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+nonprotein+nitrogen+on+estimation+of+protein+from+total+nitrogen+in+fleshy+fruits.">Influence of nonprotein nitrogen on estimation of protein from total nitrogen in fleshy fruits.</a> Journal of Chemical Ecology. 19, 2605-2615 (1993).</li><li>Moss&#233;, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrogen+to+protein+conversion+factor+for+ten+cereals+and+six+legume+or+oilseeds.+A+reappraisal+of+its+definition+and+determination.+Variation+according+to+species+and+seed+protein+content.">Nitrogen to protein conversion factor for ten cereals and six legume or oilseeds. A reappraisal of its definition and determination. Variation according to species and seed protein content.</a> Journal of Agricultural and Food Chemistry. 38, 18-24 (1990).</li><li>Bradford, M. M. <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+and+sensitive+method+for+the+quantitation+of+microgram+quantities+of+protein+utilizing+the+principle+of+protein-dye+binding.">A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.</a> Analytical Biochemistry. 72 (1-2), 248-254 (1976).</li><li>Jones, C. G., Hare, J. D., Compton, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+plant+protein+with+the+Bradford+assay.">Measuring plant protein with the Bradford assay.</a> Journal of Chemical Ecology. 15 (3), 979-992 (1989).</li><li>Dubois, M., Gilles, K. A., Hamilton, J. K., Rebers, P. A., Smith, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colormetric+method+for+determination+of+sugars+and+related+substances.">Colormetric method for determination of sugars and related substances.</a> Analytical Biochemistry. 28, 350-358 (1956).</li><li>Clissold, F. J., Sanson, G. D., Read, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+paradoxical+effects+of+nutrient+ratios+and+supply+rates+on+an+outbreaking+insect+herbivore,+the+Australian+plague+locust.">The paradoxical effects of nutrient ratios and supply rates on an outbreaking insect herbivore, the Australian plague locust.</a> Journal of Animal Ecology. 75, 1000-1013 (2006).</li><li>Smith, D., Paulsen, G. M., Raguse, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+total+available+carbohydrates+from+grass+and+legume+tissue.">Extraction of total available carbohydrates from grass and legume tissue.</a> Plant Physiology. 39 (6), 960-962 (1964).</li><li>Cui, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Food carbohydrates: Chemistry, physical properties, and applications. , (2005).</li><li>Chow, P. S., Landh&#228;usser, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+routine+measurements+of+total+sugar+and+starch+content+in+woody+plant+tissues.">A method for routine measurements of total sugar and starch content in woody plant tissues.</a> Tree Physiology. 24 (10), 1129-1136 (2004).</li><li>Masuko, T., Minami, A., Iwasaki, N., Majima, T., Nishimura, S. I., Lee, Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbohydrate+analysis+by+a+phenol-sulfuric+acid+method+in+microplate+format.">Carbohydrate analysis by a phenol-sulfuric acid method in microplate format.</a> Analytical Biochemistry. 339 (1), 69-72 (2005).</li><li>Foley, W. J., McIlwee, A., Lawler, I., Aragones, L., Woolnough, A. P., Berding, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ecological+applications+of+near+infrared+reflectance+spectroscopy-+a+tool+for+rapid,+cost-effective+prediction+of+the+composition+of+plant+and+animal+tissues+and+aspects+of+animal+performance.">Ecological applications of near infrared reflectance spectroscopy- a tool for rapid, cost-effective prediction of the composition of plant and animal tissues and aspects of animal performance.</a> Oecologia. 116 (3), 292-305 (1998).</li><li>Kokaly, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+a+physical+basis+for+spectroscopic+estimates+of+leaf+nitrogen+concentration.">Investigating a physical basis for spectroscopic estimates of leaf nitrogen concentration.</a> Remote Sensing of Environment. 75 (2), 153-161 (2001).</li><li>Schulz, H., Baranska, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+quantification+of+valuable+plant+substances+by+IR+and+Raman+spectroscopy.">Identification and quantification of valuable plant substances by IR and Raman spectroscopy.</a> Vibrational Spectroscopy. 43 (1), 13-25 (2007).</li><li>Cozzolino, D., Mor&#243;n, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+potential+of+near-infrared+reflectance+spectroscopy+to+analyse+soil+chemical+and+physical+characteristics.">The potential of near-infrared reflectance spectroscopy to analyse soil chemical and physical characteristics.</a> The Journal of Agricultural Science. 140, 65-71 (2003).</li><li>Simpson, S. J., Sword, G. A., Lorch, P. D., Couzin, I. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cannibal+crickets+on+a+forced+march+for+protein+and+salt.">Cannibal crickets on a forced march for protein and salt.</a> Proceedings of the National Academy of Sciences of the United States of America. 103 (11), 4152-4156 (2006).</li><li>Lihoreau, M., Buhl, J., Sword, G. A., Raubenheimer, D., Simpson, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nutritional+ecology+beyond+the+individual:+a+conceptual+framework+for+integrating+nutrition+and+social+interactions.">Nutritional ecology beyond the individual: a conceptual framework for integrating nutrition and social interactions.</a> Ecology Letters. 18 (3), 273-286 (2015).</li><li>Deans, C. A., Behmer, S. T., Tessnow, A., Tamez-Guerra, P., Pusztai-Carey, M., Sword, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nutrition+affects+insect+susceptibility+to+Bt.">Nutrition affects insect susceptibility to Bt.</a> Scientific Reports. 7, 39705 (2017).</li></ol>

By combining well-established colorimetric assays with effective plant-specific extraction protocols, the assays demonstrated here provide a reasonable and accurate method for measuring plant soluble protein and digestible carbohydrate content. Our results using corn as an exemplar illustrates how these protocols can be used to obtain precise measurements across different biologically-relevant spatial scales. For example, we were able to detect differences in plant soluble protein and digestible carbohydrate content betw...

Plant biomass forms the foundation of virtually all terrestrial food-webs. Plants acquire nutritional elements from the soil through their roots systems and utilize sunlight in their foliar tissues to synthesize biomolecules. In particular, carbon and nitrogen are used to create carbohydrates, proteins (comprised of amino acids), and lipids that are needed to build plant biomass (it should be noted that in plant physiology the term &#34;macronutrient&#34; often refers to soil elements, such as N, P, K, and S, however, throughout this paper this term will refer to biomolecules, such as proteins, carbohydrates, and lipids). When herbivores consume plant material, the macronutrients contained in plant tissues are broken down into their constituent parts and then used to drive the physiological processes of the consumer. In this way, plant macronutrients have a strong influence on consumer physiology along with important implications for higher order ecological interactions and food-web dynamics.
Across the animal kingdom, soluble protein and digestible carbohydrates are the macronutrients most closely tied to survival, reproduction, and performance1. Moreover, the majority of animals actively regulate their intake of these two macronutrients to meet their physiological demands1,2. This is particularly true for insect herbivores that detect the concentrations of sugars and amino acids in plant tissues, which in turn directs feeding behavior. As a result, plant soluble protein and digestible carbohydrate content has played a strong role in the evolution of plant-insect interactions.
While data on plant soluble protein and digestible carbohydrate content are relatively rare (but see6,7,8,9,10,11), there is a preponderance of data available on plant elemental content (carbon, nitrogen, and phosphorus). Largely this is because elements play a primary role in plant mineral nutrition3,4,5. Where elements are measured, correlations have been used to extrapolate the amount of soluble protein and digestible carbohydrate, but accurate calculations are often difficult to obtain. For instance, it is impossible to use carbon as an indicator of plant digestible carbohydrate content because carbon is ubiquitously present in all organic compounds. A stronger relationship exists between elemental nitrogen and plant soluble protein content, and generalized nitrogen-to-protein conversion factors are often utilized. However, there is strong evidence that nitrogen-to-protein conversions are highly species-specific12,13,14,15, making the use of generalized conversion likely inaccurate. Because of this, nitrogen-to-protein conversion factors often lack precision, particularly to the extent that is required for nutritional studies on herbivores. Also, the presence of N-containing plant allelochemicals,&#160;such as alkaloids and glucosinolates that are often toxic to herbivores, can confound these conversions.
Here, we offer two chemical assays for measuring the concentration of soluble proteins and digestible carbohydrates in plant tissues. These assays are presented separately, but it is suggested that they be used concurrently to analyze the same plant samples in order to achieve a more comprehensive analysis of plant macronutrients. Both employ similar methodologies, consisting of an extraction step, followed by quantification via absorbance. Plant sample prep is also identical for both protocols, making it easy to run both analyses in tandem. The utility of these assays do not stem from their novelty, as they rely on older, (Bradford, Jones, Dubois) well-established colorimetric assays16,17,18, but here we have organized a clear and easy-to-follow protocol that combines these methods with more obscure plant-specific extraction techniques17,19 in order to make the application of these assays more accessible to those in plant-relevant fields.
For both assays, plant macronutrients are first extracted physically by freezing, lyophilizing, and grinding the plant material. For the soluble protein assay, further chemical extraction is done17,19 through several rounds of vortexing and heating samples in NaOH solution. The well-known Bradford assay, utilizing Coomassie brilliant blue G-250, is then used to quantify soluble proteins and polypeptides between 3,000-5,000 Daltons16,17. This assay has a detection range between 1-20 &#181;g total proteins per microplate well or &#60;25 &#181;g/mL, but does not measure free amino acids. The extraction step of the digestible carbohydrate assay is based on the dilute acid method of Smith et al.20 and allows for the isolation of soluble sugars, starch, and fructosan &#8211; but not structural carbohydrates. A phenol-sulfuric acid quantification method is taken from Dubois et al.18 and measures all mono-, oligo-, and polysaccharides (as well as methyl derivatives). This assay is able to quantify specific sugars, but here we use it as an indicator of total digestible carbohydrate content (see Smith et al.20 for more detailed analysis). Together, these assays measure the two macronutrients that are strongly tied to plant eco-physiology and herbivore performance, providing important data on resource quality at the base of terrestrial food-webs. Presenting these protocols promotes the generation of plant macronutrient datasets in order to obtain a more thorough understanding of plant physiology, herbivore nutritional ecology, and plant-herbivore interactions.

<table border="0" cellpadding="0" cellspacing="0" width="670">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:273px;">microplate reader (spectrophotometer)</td>
			<td style="width:111px;">Bio-Rad</td>
			<td style="width:119px;">Model 680 XR</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:273px;">Bio-Rad Protein Assay Dye Reagent concentrate</td>
			<td style="width:111px;">Bio-Rad</td>
			<td style="width:119px;">#5000006</td>
			<td>450mL</td>
		</tr>
	</tbody>
</table>

quantifying plant soluble protein and digestible carbohydrate content, using corn (zea mays) as an exemplar

Elemental data are commonly used to infer plant quality as a resource to herbivores. However, the ubiquity of carbon in biomolecules, the presence of nitrogen-containing plant defensive compounds, and variation in species-specific correlations between nitrogen and plant protein content all limit the accuracy of these inferences. Additionally, research focused on plant and/or herbivore physiology require a level of accuracy that is not achieved using generalized correlations. The methods presented here offer researchers a clear and rapid protocol for directly measuring plant soluble proteins and digestible carbohydrates, the two plant macronutrients most closely tied to animal physiological performance. The protocols combine well characterized colorimetric assays with optimized plant-specific digestion steps to provide precise and reproducible results. Our analyses of different sweet corn tissues show that these assays have the sensitivity to detect variation in plant soluble protein and digestible carbohydrate content across multiple spatial scales. These include between-plant differences across growing regions and plant species or varieties, as well as within-plant differences in tissue type and even positional differences within the same tissue. Combining soluble protein and digestible carbohydrate content with elemental data also has the potential to provide new opportunities in plant biology to connect plant mineral nutrition with plant physiological processes. These analyses also help generate the soluble protein and digestible carbohydrate data needed to study nutritional ecology, plant-herbivore interactions and food-web dynamics, which will in turn enhance physiology and ecological research.

To show the usefulness of these methods, we analyzed the soluble protein and digestible carbohydrate content of four different field and sweetcorn tissues that serve as distinct potential nutritional resources for insect herbivores. We collected ears of corn from three agricultural regions in the United States (Minnesota, North Carolina, and Texas), encompassing five different varieties of sweet corn (i.e., genotypes) and one variety of field corn as an outgroup. Table 3<...

Watch this Scientific Journal Video about Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn Zea mays As an Exemplar at JoVE.com

Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn Zea mays As an Exemplar

The protocols described herein provide a clear and approachable methodology for measuring soluble protein and digestible (non-structural) carbohydrate content in plant tissues. The ability to quantify these two plant macronutrients has significant implications for advancing the fields of plant physiology, nutritional ecology, plant-herbivore interactions and food-web ecology.

Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn (Zea mays) As an Exemplar

Elemental data are commonly used to infer plant quality as a resource to herbivores. However, the ubiquity of carbon in biomolecules, the presence of ...

This method allows researchers in the field of plant sciences and nutritional ecology to accurately measure concentrations of soluble proteins and digestible carbohydrates in plant tissue. The main advantage of these techniques is that they offer a quick and easy method for quantifying these two incredibly important macronutrients with high accuracy. These techniques have strong implications for the field of ecology because plant proteins and carbohydrates make up the base of terrestrial food webs.Generally, individuals new to this technique may struggle because there are several steps and some techniques which are not commonly performed in a general-use lab. To begin, weigh out replicate samples of each tissue into labeled 1.5 milliliter microcentrifuge tubes. Next, record the precise mass of each sample.Using a micropipetter, add 500 micro-liters of 0.1 molar sodium hydroxide to each tube. Close the lids tightly and sonic heat the tubes for 30 minutes. Next, place the tubes in a preheated hot-water bath for 15 minutes.After this, centrifuge the tubes at 15, 000 G for 10 minutes. Pipette the supernatant into new, labeled microcentrifuge tubes, using a new pipette tip for each sample. Add 300 microliters of 0.1 molar sodium hydroxide to the pellet, and repeat the centrifugation for 10 minutes.After this, remove the supernatant and transfer it to the tubes containing the supernatant from the first centrifugation. To neutralize the pH of the supernatant, add 11 microliters of 5.8 molar hydrochloric acid. Use litmus paper to confirm the pH is approximately seven.Next, add 90 microliters of 100%trichloroacetic acid to each tube. Then incubate the tubes on ice for 30 minutes. Centrifuge the samples at 13, 000 G for 10 minutes at four degrees Celsius.Carefully use a vacuum line and glass micropipette tip to remove the trichloroacetic acid. Be very careful not to disturb the pellet with the suction tip. Next, wash the pellet with 100 microliters of acetone cooled to 20 degrees Celsius, then allow the acetone to evaporate in a fume hood.Dissolve the protein pellet with one milliliter of sodium hydroxide. Additional rounds of heating, vortexing and sonic heating may be required. Add 160 microliters of each IGG standard solution to a 96-well plate in triplicate, starting with the A1 position Next, in a new 1.5 milliliter tube add 50 microliters of each sample solution to 950 microliters of distilled water.Then add 60 microliters of each diluted sample to the well plate in triplicate, starting with the H1 position. Add 100 microliters of distilled water to all of the blank and unknown sample wells. Using a multi-channel pipette, add 40 microliters of Coomassie Brilliant Blue G-250 protein dye to each well of the plate.Using a needle, pop any bubbles present in the wells. After this, allow the plate to incubate at room temperature for five minutes. Then use a microplate spectrophotometer to record the absorbence values for each well at 595 nanometers.First, weigh out replicates from each tissue sample into glass 15 milliliter tubes. Label the tubes and record the exact mass of each sample. Next, add one milliliter of 0.1 molar sulfuric acid to each tube and close the caps tightly.Then place the tubes in a boiling-water bath for one hour. Transfer the tubes to a tepid water bath to cool. Then pour the contents of the tubes into labeled 1.5 milliliter microcentrifuge tubes.After this centrifuge tubes at 15, 000 G for 10 minutes. Use a micro pipette to transfer the supernatant to new labeled 1.5 milliliter tubes. Using a pipette transfer 15 microliters of each unknown sample to its own test tube.Then add 385 microliters of distilled water to each tube. In a fume hood add 400 microliters of 5%phenol to each standard and unknown sample test tube. Immediately thereafter add two milliliters of sulfuric acid to each tube.Make sure to add the sulfuric acid to the surface of the solution. After incubating the tubes for 10 minutes, vortex the tubes. Then incubate the tube for an additional 30 minutes.Transfer 800 microliter from each sample tube to three polystyrene 1.5 milliliter semi-microcuvettes. Then set the spectrophotometer to read at 490 nanometers and calibrated with a blank cuvette. Finally, run each cuvette through the spectrophotometer and record the absorbence.Using this protocol, the soluble protein and digestible carbohydrate content of four different field and sweet corn tissues from three geographical regions were analyzed. Significant differences in soluble protein content were observed between the regions, thus necessitating separate analyses for each region. Across regions there were several differences in soluble protein and digestible carbohydrate content between tissues.In Minnesota, tissues only varied in soluble protein content while North Carolina tissues varied in both soluble protein and digestible carbohydrates. Variability in tissue macronutrient content in Texas depended on the variety. This technique will allow researchers in the field of plant sciences and nutritional ecology to precisely measure soluble plant protein and digestible carbohydrates, rather than extrapolating from elemental measures.Don't forget that working with liquid nitrogen, concentrated acids and bases, can be extremely hazardous. So always use precautions such as gloves, safety goggles, aprons and closed-toed shoes whenever working with these chemicals.

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Analysis of Fatty Acid Content and Composition in Microalgae

A method to determine the content and composition of total fatty acids present in microalgae is described. Fatty acids are a major constituent of microalgal biomass. These fatty acids can be present in different acyl-lipid classes. Especially the fatty acids present in triacylglycerol (TAG) are of commercial interest, because they can be used for production of transportation fuels, bulk chemicals, nutraceuticals (&omega;-3 fatty acids), and food commodities. To develop commercial applications, reliable analytical methods for quantification of fatty acid content and composition are needed. Microalgae are single cells surrounded by a rigid cell wall. A fatty acid analysis method should provide sufficient cell disruption to liberate all acyl lipids and the extraction procedure used should be able to extract all acyl lipid classes.
With the method presented here all fatty acids present in microalgae can be accurately and reproducibly identified and quantified using small amounts of sample (5 mg) independent of their chain length, degree of unsaturation, or the lipid class they are part of.
This method does not provide information about the relative abundance of different lipid classes, but can be extended to separate lipid classes from each other.
The method is based on a sequence of mechanical cell disruption, solvent based lipid extraction, transesterification of fatty acids to fatty acid methyl esters (FAMEs), and quantification and identification of FAMEs using gas chromatography (GC-FID). A TAG internal standard (tripentadecanoin) is added prior to the analytical procedure to correct for losses during extraction and incomplete transesterification.

A method for the determination of fatty acid content and composition in microalgae based on mechanical cell disruption, solvent based lipid extraction, transesterification, and quantification and identification of fatty acids using gas chromatography is described. A tripentadecanoin internal standard is used to compensate for the possible losses during extraction and incomplete transesterification.

A method to determine the content and composition of total fatty acids present in microalgae is described. Fatty acids are a major constituent of ...

Transcript and Metabolite Profiling for the Evaluation of Tobacco Tree and Poplar as Feedstock for the Bio-based Industry

The global demand for food, feed, energy, and water poses extraordinary challenges for future generations. It is evident that robust platforms for the exploration of renewable resources are necessary to overcome these challenges. Within the multinational framework MultiBioPro we are developing biorefinery pipelines to maximize the use of plant biomass. More specifically, we use poplar and tobacco tree (Nicotiana glauca) as target crop species for improving saccharification, isoprenoid, long chain hydrocarbon contents, fiber quality, and suberin and lignin contents. The methods used to obtain these outputs include GC-MS, LC-MS and RNA sequencing platforms. The metabolite pipelines are well established tools to generate these types of data, but also have the limitations in that only well characterized metabolites can be used. The deep sequencing will allow us to include all transcripts present during the developmental stages of the tobacco tree leaf, but has to be mapped back to the sequence of Nicotiana tabacum. With these set-ups, we aim at a basic understanding for underlying processes and at establishing an industrial framework to exploit the outcomes. In a more long term perspective, we believe that data generated here will provide means for a sustainable biorefinery process using poplar and tobacco tree as raw material. To date the basal level of metabolites in the samples have been analyzed and the protocols utilized are provided in this article.

Plant biomass offers a renewable resource for multiple products, including fuel, feed, food, and a variety of materials. In this paper we investigate the properties of tobacco tree (Nicotiana glauca) and poplar as suitable sources for a biorefinery pipeline.

The global demand for food, feed, energy, and water poses extraordinary challenges for future generations. It is evident that robust platforms for the ...

Air-sampled Filter Analysis for Endotoxins and DNA Content

Outdoor aerosol research commonly uses particulate matter sampled on filters. This procedure enables various characterizations of the collected particles to be performed in parallel. The purpose of the method presented here is to obtain a highly accurate and reliable analysis of the endotoxin and DNA content of bio-aerosols extracted from filters. The extraction of high molecular weight organic molecules, such as lipopolysaccharides, from sampled filters involves shaking the sample in a pyrogen-free water-based medium. The subsequent analysis is based on an enzymatic reaction that can be detected using a turbidimetric measurement. As a result of the high organic content on the sampled filters, the extraction of DNA from the samples is performed using a commercial DNA extraction kit that was originally designed for soils and modified to improve the DNA yield. The detection and quantification of specific microbial species using quantitative polymerase chain reaction (q-PCR) analysis are described and compared with other available methods.

Two complementary analyses of atmospheric biological particles from air sampled filters are described herein: the extraction and detection of endotoxin, and of DNA.

Outdoor aerosol research commonly uses particulate matter sampled on filters. This procedure enables various characterizations of the collected particles ...

Method to Produce Durable Pellets at Lower Energy Consumption Using High Moisture Corn Stover and a Corn Starch Binder in a Flat Die Pellet Mill

A major challenge in the production of pellets is the high cost associated with drying biomass from 30 to 10% (w.b.) moisture content. At Idaho National Laboratory, a high-moisture pelleting process was developed to reduce the drying cost. In this process the biomass pellets are produced at higher feedstock moisture contents than conventional methods, and the high moisture pellets produced are further dried in energy efficient dryers. This process helps to reduce the feedstock moisture content by about 5-10% during pelleting, which is mainly due to frictional heat developed in the die. The objective of this research was to explore how binder addition influences the pellet quality and energy consumption of the high-moisture pelleting process in a flat die pellet mill. In the present study, raw corn stover was pelleted at moistures of 33, 36, and 39% (w.b.) by addition of 0, 2, and 4% pure corn starch. The partially dried pellets produced were further dried in a laboratory oven at 70 &#176;C for 3-4 hr to lower the pellet moisture to less than 9% (w.b.). The high moisture and dried pellets were evaluated for their physical properties, such as bulk density and durability. The results indicated that increasing the binder percentage to 4% improved pellet durability and reduced the specific energy consumption by 20-40% compared to pellets with no binder. At higher binder addition (4%), the reduction in feedstock moisture during pelleting was &#60;4%, whereas the reduction was about 7-8% without the binder. With 4% binder and 33% (w.b.) feedstock moisture content, the bulk density and durability values observed of the dried pellets were &#62;510 kg/m3 and &#62;98%, respectively, and the percent fine particles generated was&#160;reduced to &#60;3%.

In this study, a protocol was developed to produce good quality pellets using a flat die pellet mill at reduced specific energy consumption testing high-moisture corn stover and a starch based binder. The results indicated that adding a corn starch binder improved the pellet durability, reduced percent fines and decreased specific energy consumption.

A major challenge in the production of pellets is the high cost associated with drying biomass from 30 to 10% (w.b.) moisture content. At Idaho National ...

Development of New Methods for Quantifying Fish Density Using Underwater Stereo-video Tools

The use of video camera systems in ecological studies of fish continues to gain traction as a viable, non-extractive method of measuring fish lengths and estimating fish abundance. We developed and implemented a rotating stereo-video camera tool that covers a full 360 degrees of sampling, which maximizes sampling effort compared to stationary camera tools. A variety of studies have detailed the ability of static, stereo-camera systems to obtain highly accurate and precise measurements of fish; the focus here was on the development of methodological approaches to quantify fish density using rotating camera systems. The first approach was to develop a modification of the metric MaxN, which typically is a conservative count of the minimum number of fish observed on a given camera survey. We redefine MaxN to be the maximum number of fish observed in any given rotation of the camera system. When precautions are taken to avoid double counting, this method for MaxN may more accurately reflect true abundance than that obtained from a fixed camera. Secondly, because stereo-video allows fish to be mapped in three-dimensional space, precise estimates of the distance-from-camera can be obtained for each fish. By using the 95% percentile of the observed distance from camera to establish species-specific areas surveyed, we account for differences in detectability among species while avoiding diluting density estimates by using the maximum distance a species was observed. Accounting for this range of detectability is critical to accurately estimate fish abundances. This methodology will facilitate the integration of rotating stereo-video tools in both applied science and management contexts.

We describe a new method for counting fishes, and estimating relative abundance (MaxN) and fish density using rotating stereo-video camera systems. We also demonstrate how to use distance from camera (Z distance) to estimate species-specific detectability.

The use of video camera systems in ecological studies of fish continues to gain traction as a viable, non-extractive method of measuring fish lengths and ...

High-throughput, Microscale Protocol for the Analysis of Processing Parameters and Nutritional Qualities in Maize (Zea mays L.)

Maize is an important grain crop in the United States and worldwide. However, maize grain must be processed prior to human consumption. Furthermore, whole grain composition and processing characteristics vary among maize hybrids and can impact the quality of the final processed product. Therefore, in order to produce healthier processed food products from maize, it is necessary to know how to optimize processing parameters for particular sets of germplasm to account for these differences in grain composition and processing characteristics. This includes a better understanding of how current processing techniques impact the nutritional quality of the final processed food product. Here, we describe a microscale protocol that both simulates the processing pipeline to produce cornflakes from large flaking grits and allows for the processing of multiple grain samples simultaneously. The flaking grits, the intermediate processed products, or final processed product, as well as the corn grain itself, can be analyzed for nutritional content as part of a high-throughput analytical pipeline. This procedure was developed specifically for incorporation into a maize breeding research program, and it can be modified for other grain crops. We provide an example of the analysis of insoluble-bound ferulic acid and p-coumaric acid content in maize. Samples were taken at five different processing stages. We demonstrate that sampling can take place at multiple stages during microscale processing, that the processing technique can be utilized in the context of a specialized maize breeding program, and that, in our example, most of the nutritional content was lost during food product processing.

High-throughput, Microscale Protocol for the Analysis of Processing Parameters and Nutritional Qualities in Maize Zea mays L.

Here, we present a microscale protocol for processing grain samples and for incorporating this microscale approach into a high-throughput analytical pipeline. This is a higher throughput adaptation of currently available protocols.

Maize is an important grain crop in the United States and worldwide. However, maize grain must be processed prior to human consumption. Furthermore, whole ...

Design and Use of an Apparatus for Quantifying Bivalve Suspension Feeding at Sea

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves (i.e., mussels, oysters, and clams) presents new challenges. Quantitative data on the feeding behavior of suspension-feeding mollusks is necessary to determine important ecosystem interactions of offshore shellfish farms, including their carrying capacity, the competition with the zooplankton community, the availability of trophic resources at different depths, and the deposition to the benthos. The biodeposition method is used to quantify feeding variables in suspension-feeding bivalves in a natural setting and represents a more realistic proxy than laboratory experiments. This method, however, relies upon a stable platform to satisfy the requirements that water flow rates supplied to the shellfish remain constant and the bivalves are undisturbed. A flow-through device and process for using the biodeposition method to quantify the feeding of bivalve mollusks were modified from a land-based format for shipboard use by building a two-dimensional gimbal table around the device. Planimeter data reveal a minimal pitch and yaw of the chambers containing the test shellfish despite boat motion, the flow rates within the chambers remain constant, and operators are able to collect the biodeposits (feces and pseudofeces) with sufficient consistency to obtain accurate measurements of the bivalve clearance, filtration, selection, ingestion, rejection, and absorption at offshore shellfish aquaculture sites.

A flow-through device for using the biodeposition method to quantify filtration and feeding behavior of bivalve mollusks was modified for shipboard use. A two-dimensional gimbal table built around the device isolates the apparatus from boat motion, thereby allowing the accurate quantification of bivalve filtration variables at offshore shellfish aquaculture sites.

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves ...

Combining Eye-tracking Data with an Analysis of Video Content from Free-viewing a Video of a Walk in an Urban Park Environment

As individuals increasingly live in cities, methods to study their everyday movements and the data that can be collected becomes important and valuable. Eye-tracking informatics are known to connect to a range of feelings, health conditions, mental states and actions. But because vision is the result of constant eye-movements, teasing out what is important from what is noise is complex and data intensive. Furthermore, a significant challenge is controlling for what people look at compared to what is presented to them.
The following presents a methodology for combining and analyzing eye-tracking on a video of a natural and complex scene with a machine learning technique for analyzing the content of the video. In the protocol we focus on analyzing data from filmed videos, how a video can be best used to record participants&#39; eye-tracking data, and importantly how the content of the video can be analyzed and combined with the eye-tracking data. We present a brief summary of the results and a discussion of the potential of the method for further studies in complex environments.

The objective of the protocol is to detail how to collect video data for use in the laboratory; how to record eye-tracking data of participants looking at the data and how to efficiently analyze the content of the videos that they were looking at using a machine learning technique.

As individuals increasingly live in cities, methods to study their everyday movements and the data that can be collected becomes important and valuable. ...

Separation of Spinach Thylakoid Protein Complexes by Native Green Gel Electrophoresis and Band Characterization using Time-Correlated Single Photon Counting

The light reactions of photosynthesis are carried out by a series of pigmented protein complexes in the thylakoid membranes. The stoichiometry and organization of these complexes is highly dynamic on both long and short time scales due to processes that adapt photosynthesis to changing environmental conditions (i.e., non-photochemical quenching, state transitions, and the long-term response). Historically, these processes have been described spectroscopically in terms of changes in chlorophyll fluorescence, and spectroscopy remains a vital method for monitoring photosynthetic parameters. There are a limited number of ways in which the underlying protein complex dynamics can be visualized. Here we describe a fast and simple method for the high-resolution separation and visualization of thylakoid complexes, native green gel electrophoresis. This method is coupled with time-correlated single photon counting for detailed characterization of the chlorophyll fluorescence properties of bands separated on the green gel.

Here we present a protocol to separate solubilized thylakoid complexes by Native Green Gel electrophoresis. Green gel bands are subsequently characterized by Time Correlated Single Photon Counting (TCSPC) and basic steps for data analysis are provided.

The light reactions of photosynthesis are carried out by a series of pigmented protein complexes in the thylakoid membranes. The stoichiometry and ...

An Optimized Rhizobox Protocol to Visualize Root Growth and Responsiveness to Localized Nutrients

Roots are notoriously difficult to study. Soil is both a visual and mechanical barrier, making it difficult to track roots in situ without destructive harvest or expensive equipment. We present a customizable and affordable rhizobox method that allows the non-destructive visualization of root growth over time and is particularly well-suited to studying root plasticity in response to localized resource patches. The method was validated by assessing maize genotypic variation in plasticity responses to patches containing 15N-labeled legume residue. Methods are described to obtain representative developmental measurements over time, measure root length density in resource-containing and control patches, calculate root growth rates, and determine 15N recovery by plant roots and shoots. Advantages, caveats, and potential future applications of the method are also discussed. Although care must be taken to ensure that experimental conditions do not bias root growth data, the rhizobox protocol presented here yields reliable results if carried out with sufficient attention to detail.

Visualizing and measuring root growth in situ is extremely challenging. We present a customizable rhizobox method to track root development and proliferation over time in response to nutrient enrichment. This method is used to analyze maize genotypic differences in root plasticity in response to an organic nitrogen source.

Roots are notoriously difficult to study. Soil is both a visual and mechanical barrier, making it difficult to track roots in situ without destructive ...