Name: separation of bioactive small molecules, peptides from natural sources and proteins from microbes by preparative isoelectric focusing (ief) method
Uploaded: 2020-06-14T14:00:00.000+00:00
Duration: 9 min 57 s
Description: Watch this Scientific Journal Video about Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative Isoelectric Focusing IEF Method at JoVE.com

We are thankful for the funding sources from the Division of Biology and Johnson Cancer Research Center for BRIEF and IRA awards, respectively to GV. We also thank the K-INBRE postdoctoral award to RV. This work was supported in part by the Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20 GM103418. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of General Medical Sciences or the National Institutes of Health. We thank the anonymous reviewers for their helpful comments.

1. Setup and prerunning of standard liquid-phase IEF unit
<ol>
	<li>Assemble the liquid-phase IEF electrodes (anode-red button and cathode-black button) with their respective exchange membranes according to the instruction manual (see Table of Materials). Equilibrate the anion exchange membranes with 0.1 M NaOH and the cation exchange membranes with 0.1 M H3PO4 at least for 16 h when new membranes are used.
	<ol>
		<li>Store the membranes in electrolytes (0.1 M NaOH or 0.1 M H3PO4) between runs and do not allow to dry out.</li>
	</ol>
	</li>
	<li>Assemble the inner and outer portion of the electrode by aligning three oblong holes in the ion-exchange gaskets. Fill the electrodes with respective electrolytes (~25-30 mL) to prevent their membranes from drying out.
	<ol>
		<li>Do not add excess (more than 1/3rd of electrode chamber volume) electrolyte that may build up pressure inside the electrode and cause leakage.</li>
	</ol>
	</li>
	<li>Cover the sample collection ports with sealing tape that comes with the instrument assembly parts (see Table of Materials). The sample collection ports side can be identified by the two vertical metal aligning pins. Alternatively, use standard sealing tape to seal the ports.</li>
	<li>Assemble all parts of the focusing chamber assembly in sequence (anode electrode, nylon membrane core, focusing chamber and cathode electrode) over the ceramic cooling finger.</li>
	<li>Fill the focusing chamber with precooled distilled water (total volume of 60 mL for the standard IEF cell) using a 50 mL syringe.</li>
	<li>Connect the liquid-phase IEF instrument to a circulating cooling water at 4 &#186;C and prerun the unit at 15 W and 3,000 V for 3-5 min or until the voltage stabilizes. 
	NOTE: Generally, within one minute, the voltage will reach the maximum set values. Prerunning with distilled water helps to remove the residual ions from the focusing chamber and the nylon membrane core.</li>
	<li>Switch off the power source and remove the water from the cell using the fraction collector. Re-seal the collection ports with sealing tape. 
	NOTE: Now the instrument is ready for use in step 2.4.</li>
</ol>
2. Separation and purification of small molecules and peptides from Gymnema sylvestre&#160; extract
<ol>
	<li>Measure 0.6 g of plant extract and dissolve in distilled water (60 mL) by mixing in a roller tube for 5 min. 
	NOTE: Any biological sample that is soluble and free of salt can be used for separation and purification using this IEF instrument. Samples with buffering salt concentration up to 10 mM can be used with slightly decreased resolution. We are interested in the saponin family of triterpenoid compounds, the gymnemic acids, from G. sylvestre plant for their unique antifungal properties16.</li>
	<li>Centrifuge the solubilized plant extract at 10,000 x g for 5 min to remove insoluble particles.</li>
	<li>Transfer the supernatant (~60 mL) to an 80 mL centrifuge tube, and mix it with 0.6 mL of ampholyte (pH 3-10) to 1% (v/v).</li>
	<li>Follow steps 1.1 &#8211; 1.7 to prepare the liquid-phase IEF unit. The chamber is now ready to load the sample.</li>
	<li>Use a 50 mL syringe with a 1-1/2 inch 19 G blunt end needle (comes with the instrument) and load the prepared sample with ampholyte (60 mL total) in the cell through sample collection ports.</li>
	<li>Remove air bubbles from the sample cell by removing the focusing cell from the stand and tapping the electrode chamber to dislodge the bubbles. The presence of air bubbles will cause voltage and current fluctuations and affect the run.</li>
	<li>Connect the unit to the water coolant (4 &#176;C) and start fractionation with the power supply at a constant 15 W.</li>
	<li>Run the apparatus for 3 h or until the voltage reaches a constant value. 
	NOTE: As the sample starts focusing, the voltage will start climbing gradually until it reaches a constant value.</li>
	<li>After the run, prepare to collect the fractions in the harvest box (containing 20 plastic tubes, 12 mm x 75 mm, 5-6 mL volume) connected to the vacuum pump by pressing the harvest button ON in the IEF unit.</li>
	<li>Align the 20-collection pins with the 20-collection ports of the focusing cell that is sealed with the tape.</li>
	<li>Push the collection pins through the sealing tape and turn the vacuum pump ON simultaneously (see Figure 2B, 2C &#38; 2D). 
	NOTE: About 3 mL fractions from each chamber will be collected into the tubes for each time. Fractions can be used for subsequent downstream applications (SDS-PAGE for peptide quantification, TLC and bioassay for small molecules).</li>
</ol>
3. Separation and purification of proteins from&#160;&#160;C. albicans
<ol>
	<li>Grow single colony of C. albicans in yeast-peptone-dextrose (YPD) broth16 at 30 &#176;C with shaking (200 rpm) for overnight.</li>
	<li>Collect the yeast cells by centrifugation (10,000 x g for 5 min).</li>
	<li>Suspend C. albicans yeast cells in ammonium carbonate (1.89 g/L) buffer containing 1% (v/v) beta-mercaptoethanol (&#946;-ME) (1/10th of the culture volume) and rotate in a roller tube for 1 h at 5 &#176;C15.</li>
	<li>Remove the yeast cells by centrifugation (10,000 x g for 5 min) and filter the protein extract through a 0.45 &#181;m filter. 
	NOTE: Protein samples from C. albicans cytosol, membrane or cell wall can be prepared and used for IEF fractionation. Similarly, proteins from bacteria or other biological samples (animal tissue extract) can be used after removing any salt by appropriate methods (e.g., by dialysis or using desalting columns).</li>
	<li>Dialyze the protein extract in a dialysis tubing (3,500 MWCO) against water for 15 h at 4 &#176;C. Estimate the protein concentration by the Bradford dye-binding method using gamma globulin as a standard17.</li>
	<li>Use 500 mg of total protein in 60 mL of water containing 1% (v/v) ampholyte (pH 5-8) for the fractionation. 
	NOTE: Since a broad-range ampholyte (pH 3-10) does not enrich certain non-glucan attached cell wall proteins of C. albicans well, use a narrow-range (pH 5-8) ampholyte. An ampholyte concentration of up to 2% can be used if the sample protein concentration is more than 2 mg/mL; this minimizes protein aggregation during focusing. Always keep the samples, ampholytes, and water precooled on ice.</li>
	<li>Repeat steps 1.1- 1.7 to prepare the IEF unit and use the protein solution from step 3.6 to load into the IEF cell.</li>
	<li>After 4 h of focusing at a constant 15 W, harvest protein fractions (1-20) as described above (steps 2.9-2.11) and analyze on 12.5% SDS-PAGE after reducing and boiling the protein samples18.</li>
	<li>Stain the resolved proteins by staining the SDS-PAGE gel with the Coomassie blue dye (0.01%) solution for 2-3 h at room temperature on a rocker. Destain the gel and record the gel image using a gel imager. 
	NOTE: Coomassie blue dye (0.01%) can be prepared by mixing 0.01 g of Coomassie blue powder in a destaining solution containing 40% methanol and 10% acetic acid.</li>
</ol>
4. Bioactivity of purified small molecules from plant extract Gymnema sylvestre
<ol>
	<li>Grow C. albicans in yeast cells as in step 3.1.</li>
	<li>To prepare cell suspension, dilute overnight culture of C. albicans yeast cells (1/1000 dilution) into a fresh RPMI cell culture medium supplemented with 50 mM glucose. 
	NOTE: C. albicans converts from yeast growth to hyphae under hyphal inducing conditions (RPMI at 37 &#176;C). Gymnemic acid small molecules are shown to inhibit the conversion of yeast cells into hyphae under hypha inducing conditions16. We aimed to determine if liquid-phase-IEF-separated G. sylvestre extract contain these bioactive molecules.</li>
	<li>From the prepared cell suspension, add 90 &#956;L to each well of the 96-well plate.</li>
	<li>From each fraction (1-20 harvested fractions of G. sylvestre extract obtained from liquid-phase IEF, Figure 4), add 10 &#956;L into the wells with 90 &#956;L of the above cell suspension (step 4.2). Perform the assay in triplicate.</li>
	<li>Add 10 &#956;L of water that contains ampholyte (1%) into separate wells with 90 &#956;L of C. albicans yeast cell suspension as a negative control. 
	NOTE: Ampholytes have bioactivity potential and so it is essential to include an ampholyte control while performing any bioassay19.</li>
	<li>Incubate the 96-well plate at 37 &#176;C for 12 h and observe the inhibition of C. albicans yeast-to-hypha conversion under the microscope16. Also, determine the percentage of inhibition of yeast-to-hypha conversion.</li>
</ol>

<ol>
	<li>Jankowska, U., 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=Optimized+procedure+of+extraction,+purification+and+proteomic+analysis+of+nuclear+proteins+from+mouse+brain.">Optimized procedure of extraction, purification and proteomic analysis of nuclear proteins from mouse brain.</a> Journal of Neuroscience Methods. 261, 1-9 (2016).</li><li>Pergande, M. R., Cologna, 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=Isoelectric+Point+Separations+of+Peptides+and+Proteins.">Isoelectric Point Separations of Peptides and Proteins.</a> Proteomes. 5 (1), (2017).</li><li>Stoyanov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IEF-based+multidimensional+applications+in+proteomics:+toward+higher+resolution.">IEF-based multidimensional applications in proteomics: toward higher resolution.</a> Electrophoresis. 33 (22), 3281-3290 (2012).</li><li>Vesterberg, O. A. Y. <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 of Isoelectric Fractionation. , (1964).</li><li>Vesterberg, O., Svensson, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isoelectric+fractionation,+analysis,+and+characterization+of+ampholytes+in+natural+pH+gradients.+IV.+Further+studies+on+the+resolving+power+in+connection+with+separation+of+myoglobins.">Isoelectric fractionation, analysis, and characterization of ampholytes in natural pH gradients. IV. Further studies on the resolving power in connection with separation of myoglobins.</a> Acta Chemica Scandinavica. 20 (3), 820-834 (1966).</li><li>Righetti, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Isoelectric Focusing: Theory, Methodology and Applications. , 1 (1983).</li><li>Vesterberg, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+Isoelectric+Fractionation+of+Carrier+Ampholytes.">Synthesis and Isoelectric Fractionation of Carrier Ampholytes.</a> Acta Chemica Scandinavica. 23, 2653-2666 (1969).</li><li>Bier, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recycling+isoelectric+focusing+and+isotachophoresis.">Recycling isoelectric focusing and isotachophoresis.</a> Electrophoresis. 19 (7), 1057-1063 (1998).</li><li>Bier, M., Palusinski, O. A., Mosher, R. A., Saville, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoresis:+mathematical+modeling+and+computer+simulation.">Electrophoresis: mathematical modeling and computer simulation.</a> Science. 219 (4590), 1281-1287 (1983).</li><li>Ayala, A., Parrado, J., Machado, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+Rotofor+preparative+isoelectrofocusing+cell+in+protein+purification+procedure.">Use of Rotofor preparative isoelectrofocusing cell in protein purification procedure.</a> Applied Biochemistry and Biotechnology. 69 (1), 11-16 (1998).</li><li>Wagner, 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=Isolation+of+dipeptidyl+peptidase+IV+(DP+4)+isoforms+from+porcine+kidney+by+preparative+isoelectric+focusing+to+improve+crystallization.">Isolation of dipeptidyl peptidase IV (DP 4) isoforms from porcine kidney by preparative isoelectric focusing to improve crystallization.</a> Biological Chemistry. 392 (7), 665-677 (2011).</li><li>Hosken, B. D., Li, C., Mullappally, B., Co, C., Zhang, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+Characterization+of+Monoclonal+Antibody+Charge+Variants+by+Free+Flow+Isoelectric+Focusing.">Isolation and Characterization of Monoclonal Antibody Charge Variants by Free Flow Isoelectric Focusing.</a> Analytical Chemistry. 88 (11), 5662-5669 (2016).</li><li>Yu, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Francisella+tularensis+T-cell+antigen+identification+using+humanized+HLA-DR4+transgenic+mice.">Francisella tularensis T-cell antigen identification using humanized HLA-DR4 transgenic mice.</a> Clinical Vaccine Immunology. 17 (2), 215-222 (2010).</li><li>Riyong, D., 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=Size+and+charge+antigens+of+Dirofilaria+immitis+adult+worm+for+IgG-ELISA+diagnosis+of+bancroftian+filariasis.">Size and charge antigens of Dirofilaria immitis adult worm for IgG-ELISA diagnosis of bancroftian filariasis.</a> Southeast Asian Journal of Tropical Medicine and Public Health. 41 (2), 285-297 (2010).</li><li>Vediyappan, G., Bikandi, J., Braley, R., Chaffin, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+surface+proteins+of+Candida+albicans:+preparation+of+extracts+and+improved+detection+of+proteins.">Cell surface proteins of Candida albicans: preparation of extracts and improved detection of proteins.</a> Electrophoresis. 21 (5), 956-961 (2000).</li><li>Vediyappan, G., Dumontet, V., Pelissier, F., d'Enfert, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gymnemic+acids+inhibit+hyphal+growth+and+virulence+in+Candida+albicans.">Gymnemic acids inhibit hyphal growth and virulence in Candida albicans.</a> PLoS One. 8 (9), 74189 (2013).</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, 248-254 (1976).</li><li>Laemmli, U. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleavage+of+structural+proteins+during+the+assembly+of+the+head+of+bacteriophage+T4.">Cleavage of structural proteins during the assembly of the head of bacteriophage T4.</a> Nature. 227 (5259), 680-685 (1970).</li><li>Riazi, S., Dover, S., Turovskiy, Y., Chikindas, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Commercial+ampholytes+used+for+isoelectric+focusing+may+interfere+with+bioactivity+based+purification+of+antimicrobial+peptides.">Commercial ampholytes used for isoelectric focusing may interfere with bioactivity based purification of antimicrobial peptides.</a> Journal of Microbiological Methods. 71 (1), 87-89 (2007).</li><li>Kamei, K., Takano, R., Miyasaka, A., Imoto, T., Hara, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amino-Acid-Sequence+of+Sweet-Taste-Suppressing+Peptide+(Gurmarin)+from+the+Leaves+of+Gymnema-Sylvestre.">Amino-Acid-Sequence of Sweet-Taste-Suppressing Peptide (Gurmarin) from the Leaves of Gymnema-Sylvestre.</a> Journal of Biochemistry. 111 (1), 109-112 (1992).</li><li>Craik, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry.+Seamless+proteins+tie+up+their+loose+ends.">Chemistry. Seamless proteins tie up their loose ends.</a> Science. 311 (5767), 1563-1564 (2006).</li><li>Craik, D. J., Daly, N. L., Bond, T., Waine, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+cyclotides:+A+unique+family+of+cyclic+and+knotted+proteins+that+defines+the+cyclic+cystine+knot+structural+motif.">Plant cyclotides: A unique family of cyclic and knotted proteins that defines the cyclic cystine knot structural motif.</a> Journal of Molecular Biology. 294 (5), 1327-1336 (1999).</li><li>Stoecklin, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+and+physiological+properties+of+gymnemic+acid,+the+antisaccharine+principle+of+the+leaves+of+Gymnema+sylvestre.">Chemistry and physiological properties of gymnemic acid, the antisaccharine principle of the leaves of Gymnema sylvestre.</a> Journal of Agricultural and Food Chemistry. 17 (4), 704-708 (1969).</li><li>Liu, H. M., Kiuchi, F., Tsuda, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+structure+elucidation+of+gymnemic+acids,+antisweet+principles+of+Gymnema+sylvestre.">Isolation and structure elucidation of gymnemic acids, antisweet principles of Gymnema sylvestre.</a> Chemical &amp; Pharmaceutical Bulletin (Tokyo). 40 (6), 1366-1375 (1992).</li><li>Veerapandian, R., Vediyappan, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gymnemic+Acids+Inhibit+Adhesive+Nanofibrillar+Mediated+Streptococcus+gordonii-Candida+albicans+Mono-Species+and+Dual-Species+Biofilms.">Gymnemic Acids Inhibit Adhesive Nanofibrillar Mediated Streptococcus gordonii-Candida albicans Mono-Species and Dual-Species Biofilms.</a> Frontiers in Microbiology. 10, 2328 (2019).</li><li>Chaffin, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candida+albicans+cell+wall+proteins.">Candida albicans cell wall proteins.</a> Microbiology and Molecular Biology Reviews. 72 (3), 495-544 (2008).</li></ol>

The authors would like to declare no competing financial interests.

Small molecules from natural product sources (e.g., plants) include complex secondary metabolites that are highly diverse in chemical structure. They are believed to be involved in plant defense mechanisms. In addition, polypeptides are also present in plant tissues22. These natural product small molecules are rich sources of test molecules for drug discovery and development. However, the difficult and tedious methods required for their isolation and purification limit their use for therapeutic ap...

The purification of biomolecules from complex biological samples is an essential and often difficult step in biological experiments1. Isoelectric focusing (IEF) is well-suited for high resolution separation of complex biomolecules where carrier ampholytes travel according to their charge and establish the pH gradient in an electric field3. The first commercial carrier ampholyte for IEF was developed by Olof Vesterberg in 1964 and patented4,5. Carrier ampholytes are aliphatic oligo-amino oligo-carboxylic acid molecules of varying length and branching6. Subsequently, Vesterberg and others improved the carrier ampholytes for their expanded use in separating biomolecules6,7.
Methods to separate biomolecules include agarose and polyacrylamide gel electrophoresis, two-dimensional gel electrophoresis (2-DE), isoelectric focusing, capillary electrophoresis, isotachophoresis and other chromatographic techniques (e.g., TLC, FPLC, HPLC)2. Liquid-phase IEF performed in an instrument called a &#8220;Rotofor&#8221; was invented by Milan Bier8. He pioneered the concept and design of this instrument and contributed extensively to the theory of electrophoretic migration. His team also developed a mathematical model of electrophoretic separation process for computer simulations9.
The liquid-phase IEF apparatus is a horizontally rotating cylindrical cell consisting of a nylon core divided into 20 porous compartments and a circulating water cooling ceramic rod. The porous chambers allow molecules to migrate through the aqueous phase between the electrodes and permit collection of purified samples under vacuum in fractions. This purification system can provide up to 1000-fold purification of a specific molecule in &#60;4 hours. A valuable feature of this instrument is that it can be applied as a first step for purification from a complex mixture or as a final step to achieve purity10. If the molecule of interest is a protein, another advantage is that its native conformation will be maintained during the separation.
The use of liquid-phase IEF has been reported widely for proteins, enzymes and antibody purification6,10,11,12,13,14. Here we describe the use of this approach for separating and purifying small molecules and peptides from the medicinal plant Gymnema sylvestre. This protocol will help researchers concentrate and purify active small molecules from a plant extract for downstream applications at low cost. In addition, we also demonstrate that enrichment of proteins from a complex protein extract from Candida albicans fungus15 in this IEF-based system as a second example.

<table><tbody><tr><td>0.45 &amp;micro;m syringe filter</td><td>Fisher scientfic</td><td>09-720-004</td><td></td></tr><tr><td>2-Mercaptoethanol</td><td>Sigma</td><td>M3148</td><td></td></tr><tr><td>Ammonium carbonate</td><td>Sigma-Aldrich</td><td>207861-500</td><td></td></tr><tr><td>Bio-Lyte 3/10 Ampholyte</td><td>Bio-Rad</td><td>163-1113</td><td></td></tr><tr><td>Bio-Lyte 5/8 Ampholyte</td><td>Bio-Rad</td><td>163-1192</td><td></td></tr><tr><td>Compact low temperature thermostat</td><td>Lauda -Brinkmann</td><td>RM 6T</td><td>Set water cooling to 4 oC and it can be run even at 0 oC as when it passes through the Rotofor cooling core, the circulating water temperature will be around 5 or more depending on the voltage.</td></tr><tr><td>Coomassie Brilliant Blue R</td><td>Sigma-Aldrich</td><td>B7920</td><td></td></tr><tr><td>Dialysis tubing (3,500 MWCO)</td><td>Spectrum Spectra/Por</td><td>132112T</td><td></td></tr><tr><td>Gymnema plant leaf extract powder (&gt;25% Gymnemic acids)</td><td>Suan Farma, NJ USA</td><td></td><td></td></tr><tr><td>Incubator</td><td>Lab companion</td><td>SI 300R</td><td></td></tr><tr><td>Microscope</td><td>Leica</td><td>DM 6B</td><td></td></tr><tr><td>Mini protean electrophoresis</td><td>Bio-Rad</td><td></td><td></td></tr><tr><td>pH meter</td><td>Mettler Toledo</td><td>S20</td><td>Useful to determine the pH of the Rotofor (liquid-phase IEF) fractions</td></tr><tr><td>Rotofor</td><td>Bio-Rad</td><td>170-2972</td><td>http://www.bio-rad.com/webroot/web/pdf/lsr/literature/M1702950E.pdf (Rotofor Instruction manual for assembling the unit)</td></tr><tr><td>RPMI-1640 Medium</td><td>HyClone</td><td>DH30255.01</td><td></td></tr><tr><td>Sealing tape</td><td>Bio-Rad</td><td>170-2960</td><td>Scotch tape may also be used.</td></tr><tr><td>Sorvall legend micro 17 centrifuge</td><td>Thermo scientific</td><td>75002432</td><td></td></tr><tr><td>TPP tissue culture plate -96 well flat bottom</td><td>TPP</td><td>TP92696</td><td></td></tr></tbody></table>

separation of bioactive small molecules, peptides from natural sources and proteins from microbes by preparative isoelectric focusing (ief) method

Natural products derived from plants and microbes are a rich source of bioactive molecules. Prior to their use, the active molecules from complex extracts must be purified for downstream applications. There are various chromatographic methods available for this purpose yet not all labs can afford high performance methods and isolation from complex biological samples can be difficult. Here we demonstrate that preparative liquid-phase isoelectric focusing (IEF) can separate molecules, including small molecules and peptides from complex plant extracts, based on their isoelectric points (pI). We have used the method for complex biological sample fractionation and characterization. As a proof of concept, we fractionated a Gymnema sylvestre plant extract, isolating a family of terpenoid saponin small molecules and a peptide. We also demonstrated effective microbial protein separation using the Candida albicans fungus as a model system.

Separation and purification of small molecules and peptides from Gymnema sylvestre plant extract 
Using the preparative liquid-phase IEF method, we fractionated medicinal plant extracts and cell surface proteins from a human pathogenic fungus, C. albicans. A schematic of these fractionation protocols is shown in Figure 1.
From 20 fractions of G. sylvestre extract obtained from liquid-phase IEF, the dark-colored mole...

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Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative Isoelectric Focusing IEF Method

The objective is to fractionate and isolate bioactive small molecules, peptides from a complex plant extract, and proteins from pathogenic microbes by employing liquid-phase isoelectric focusing (IEF) method. Further, the separated molecules were identified and their bioactivity confirmed.

Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative Isoelectric Focusing (IEF) Method

Natural products derived from plants and microbes are a rich source of bioactive molecules. Prior to their use, the active molecules from complex extracts ...

separation-bioactive-small-molecules-peptides-from-natural-sources

Universidad de Cartagena UDEC

Research

JoVE Journal

Immunology and Infection

9.4K Views.  Kansas State University. The objective is to fractionate and isolate bioactive small molecules, peptides from a complex plant extract, and proteins from pathogenic microbes by employing liquid-phase isoelectric focusing (IEF) method. Further, the separated molecules were identified and their bioactivity confirmed.

Video: Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative Isoelectric Focusing IEF Method

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

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

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

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

Biochemistry

On-chip Isotachophoresis for Separation of Ions and Purification of Nucleic Acids

Electrokinetic techniques are a staple of microscale applications because of their unique ability to perform a variety of fluidic and electrophoretic processes in simple, compact systems with no moving parts. Isotachophoresis (ITP) is a simple and very robust electrokinetic technique that can achieve million-fold preconcentration1,2 and efficient separation and extraction based on ionic mobility.3 For example, we have demonstrated the application of ITP to separation and sensitive detection of unlabeled ionic molecules (e.g. toxins, DNA, rRNA, miRNA) with little or no sample preparation4-8 and to extraction and purification of nucleic acids from complex matrices including cell culture, urine, and blood.9-12
ITP achieves focusing and separation using an applied electric field and two buffers within a fluidic channel system. For anionic analytes, the leading electrolyte (LE) buffer is chosen such that its anions have higher effective electrophoretic mobility than the anions of the trailing electrolyte (TE) buffer (Effective mobility describes the observable drift velocity of an ion and takes into account the ionization state of the ion, as described in detail by Persat et al.13). After establishing an interface between the TE and LE, an electric field is applied such that LE ions move away from the region occupied by TE ions. Sample ions of intermediate effective mobility race ahead of TE ions but cannot overtake LE ions, and so they focus at the LE-TE interface (hereafter called the "ITP interface"). Further, the TE and LE form regions of respectively low and high conductivity, which establish a steep electric field gradient at the ITP interface. This field gradient preconcentrates sample species as they focus. Proper choice of TE and LE results in focusing and purification of target species from other non-focused species and, eventually, separation and segregation of sample species.
We here review the physical principles underlying ITP and discuss two standard modes of operation: "peak" and "plateau" modes. In peak mode, relatively dilute sample ions focus together within overlapping narrow peaks at the ITP interface. In plateau mode, more abundant sample ions reach a steady-state concentration and segregate into adjoining plateau-like zones ordered by their effective mobility. Peak and plateau modes arise out of the same underlying physics, but represent distinct regimes differentiated by the initial analyte concentration and/or the amount of time allotted for sample accumulation.
We first describe in detail a model peak mode experiment and then demonstrate a peak mode assay for the extraction of nucleic acids from E. coli cell culture. We conclude by presenting a plateau mode assay, where we use a non-focusing tracer (NFT) species to visualize the separation and perform quantitation of amino acids.

Isotachophoresis (ITP) is a robust electrokinetic separation and preconcentration technique with applications ranging from toxin detection to sample preparation. We review the physical principles of ITP and the methodology of applying this technique to two specific example applications: separation and detection of small molecules and purification of nucleic acids from cell culture lysate.

Electrokinetic techniques are a staple of microscale applications because of their unique ability to perform a variety of fluidic and electrophoretic ...

Bioengineering

Highly Sensitive and Quantitative Detection of Proteins and Their Isoforms by Capillary Isoelectric Focusing Method

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides an alternative strategy, capillary isoelectric focusing (cIEF), with many advantages compared to conventional immunoblotting. This is an antibody-based, automated, rapid, and quantitative method in which a complete western blotting procedure takes place inside an ultrathin capillary. This technique does not require a gel to transfer to a membrane, stripping of blots, or x-ray films, which are typically required for conventional immunoblotting. Here, proteins are separated according to their charge (isoelectric point; pI), using less than a microliter (400 nL) of total protein lysate. After electrophoresis, proteins are immobilized onto the capillary walls by ultraviolet light treatment, followed by primary and secondary (horseradish peroxidase (HRP) conjugated) antibody incubation, whose binding is detected through enhanced chemiluminescence (ECL), generating a light signal that can be captured and recorded by a charge-coupled device (CCD) camera. The digital image can be analyzed and quantified (peak area) using software. This high throughput procedure can handle 96 samples at a time; is highly sensitive, with protein detection in the picogram range; and produces highly reproducible results because of automation. All of these aspects are extremely valuable when the quantity of samples (e.g., tissue samples and biopsies) is a limiting factor. The technique has wider applications as well, including screening of drugs or antibodies, biomarker discovery, and diagnostic purposes.

Capillary isoelectric focusing is an antibody-based, ultrasensitive, high throughput technique, enabling detailed characterization of proteins and their isoforms from extremely small biological samples. The following describes a protocol for detection and quantification of specific proteins and their isoforms in an automated and robotized manner.

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides ...

Electrophoretic Separation of Proteins

Electrophoresis is used to separate complex mixtures of proteins (e.g., from cells, subcellular fractions, column fractions, or immunoprecipitates), to investigate subunit compositions, and to verify homogeneity of protein samples. It can also serve to purify proteins for use in further applications. In polyacrylamide gel electrophoresis, proteins migrate in response to an electrical field through pores in a polyacrylamide gel matrix; pore size decreases with increasing acrylamide concentration. The combination of pore size and protein charge, size, and shape determines the migration rate of the protein. In this unit, the standard Laemmli method is described for discontinuous gel electrophoresis under denaturing conditions, i.e., in the presence of sodium dodecyl sulfate (SDS). 

In this video, we demonstrate a method for electrophoretic separation of proteins using poly-acrylimide gel electrophoresis (PAGE).

Electrophoresis is used to separate complex mixtures of proteins (e.g., from cells, subcellular fractions, column fractions, or immunoprecipitates), to ...

Biology

Separating Protein with SDS-PAGE

Sodium Dodecyl Sulfate Poly-Acrylamide Gel Electrophoresis, or SDS-PAGE, is a widely-used technique for separating mixtures of proteins based on their size and nothing else. SDS, an anionic detergent, is used to produce an even charge across the length of proteins that have been linearized. By first loading them into a gel made of polyacrylamide and then applying an electric field to the gel, SDS-coated proteins are then separated. The electric field acts as the driving force, drawing the SDS coated proteins towards the anode with larger proteins moving more slowly than small proteins. In order to identify proteins by size, protein standards of a known size are loaded along with samples and run under the same conditions.
This video presents an introduction to SDS-PAGE by first explaining the theory behind it and later demonstrating its step-by-step procedure. Various experimental parameters, such as the polyacrylamide concentration and voltage applied to the gel are discussed. Downstream staining methods like Coomassie and silver stains are introduced, and variations of the method, like 2D gel electrophoresis are presented.

Separating Protein with SDS-PAGE: Procedure and Applications

Sodium Dodecyl Sulfate Poly-Acrylamide Gel Electrophoresis, or SDS-PAGE, is a widely-used technique for separating mixtures of proteins based on their ...

Education

JoVE Science Education

Basic Biology

Basic Methods in Cellular and Molecular Biology

Two-Dimensional Gel Electrophoresis

Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct separation methods that have been coupled together: isoelectric focusing (IEF) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). This physically separates compounds across two axes of a gel by their isoelectric points (an electrochemical property) and their molecular weights.
The procedure in this video covers the main concepts of 2DGE and a general procedure for characterizing the composition of a complex protein solution. Three examples of this technique are shown in the applications section, including biomarker detection for disease initiation and progress, monitoring treatment in patients, and the study of proteins following posttranslational modification (PTM).
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Two-dimensional, or 2D, gel electrophoresis is a technique utilizing two distinct separation methods which can separate thousands of proteins from a single mixture. One of the techniques, SDS-PAGE or sodium dodecyl sulfate polyacrylamide gel electrophoresis, cannot fully separate complex mixtures alone. 2D gel electrophoresis couples the SDS-PAGE to a second method, isoelectric focusing or IEF, which separates based on isoelectric points, allowing for the resolution of potentially all proteins in a cell lysate. This video will show the principles of 2D gel electrophoresis, a general procedure, and some of its biomedical applications.
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2D gel electrophoresis begins with IEF as the first dimension. Every protein has a pH value, called the isoelectric point or pI, where the net charge is zero. When a protein is subjected to an electric field, it will move toward the electrode with opposite charge. Samples of interest are loaded onto immobilized pH gradient, or IPG, strips which have embedded ampholytes, molecules containing both acidic and basic groups. An electric field is then applied to the pH gradient strip, causing the proteins to migrate until they reach the pH value matching their pI, where they lose their net charge.
Prior to running the second-dimension, the embedded proteins are treated with SDS, denaturing them and providing a uniform negative charge. Once completed, the IPG strips are placed onto a polyacrylamide gel. An applied electric field draws the proteins toward the anode, with larger proteins moving more slowly through the gel.
Once the protein mixture has been separated according to pI and molecular weight, the proteome map is visualized using stains, and proteins of interest are identified.
Now that we have discussed the principles of 2D gel electrophoresis, let&#39;s go over a typical laboratory procedure.
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Before the experiment can be performed, the proteins must be solubilized into media. Solubilization of the sample is achieved by de-aggregating proteins with a combination of chaotropic agents for disrupting hydrogen-bonding interactions, nonionic detergents to prevent altering of the proteins&#39; charge, reducing agents to break disulfide bonds, and buffers. To remove interfering abundant proteins and other molecules, the material is sequentially extracted by centrifugation, and collection of the resulting pellet; followed by treatment with endonuclease, an enzyme used to consume any DNA that would interfere with the experiment.
Once the proteins have been solubilized, IPG strips are prepared by rinsing with a strip-cleaning solution and left upside-down to dry. Each strip is then assigned a strip holder number. Once ready, the cellular extract is loaded onto the strips in a slow, sliding motion from the negative to the positive end. For the purpose of rehydration, damp blotting paper is placed on top of the electrode and under the gel strips; the IPG strips are then lined onto the IEF instrument. A high electric current is applied, and the proteins begin to migrate.
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Following completion of the first dimension, the gel for SDS-PAGE is prepared in a casting apparatus. The IPG strips are treated by placing them face down in SDS-containing equilibration buffer. The electrophoresis unit is readied with the addition of electrophoresis buffer. The treated IPG strips are collected using tweezers, placed on top of the gel plates, and sealed with agarose-sealing solution. A voltage source then applies an electric field, which is held until the fastest-moving proteins are 1 cm from the bottom of the gel.
After completion of the electrophoresis, the proteins must be visualized. Traditionally this is performed by staining with Coomassie blue or silver nitrate. Proteins of interest may be transferred from the gel, and analyzed by Western blot analysis.
A second identification approach involves excision of the proteins from the gel, digesting them, than analyzing them by mass spectrometry.
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Now that we&#39;ve reviewed a procedure, let&#39;s look at some of the uses for 2D gel electrophoresis.
One of the most common uses for this technique is the identification of molecules involved in disease initiation and progression. 2D gel electrophoresis, coupled with mass spectrometry, can detect the up- or down-regulation of specific proteins in diseased areas in comparison to healthy ones.
Additionally, 2D gel electrophoresis is useful in following the progress of patients&#39; response to a potential therapeutic drug. Specimens may be taken from patients at various timepoints following administration of the treatment. In this way, 2D gel electrophoresis coupled with Western blot or mass spectrometry analysis, can detect proteins associated with negative responses such as inflammation; or the absence of proteins in an alleviated state.
Another use for 2D gel electrophoresis is in the study of protein structure and function following posttranslational modification, or PTM, which are additions to proteins following their translation from mRNA. PTM&#39;s can regulate a variety of functions, including protein signaling, gene expression, or cause oxidative damage. 2D gel electrophoresis is sensitive to modifications such as methylation or acetylation, which can cause a shift in pI as well as the molecular weight.
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You&#39;ve just watched JoVE&#39;s video on 2D gel electrophoresis. This video described the principles of the technique, a typical experimental procedure, and several of its applications in the field of biomedicine.
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Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct ...

Chemistry

Anion-Exchange Chromatography-Based Protein Purification: A Separation Technique to Isolate a Protein of Interest From Dialyzed Bacterial Lysate Based on Net Charge

Source: Fuehner, S., et al. <a href="https://jove.unicartagenaproxy.elogim.com/v/60065">Purification of Human S100A12 and Its Ion-induced Oligomers for Immune Cell Stimulation</a> J. Vis. Exp. (2019)
In this video, we demonstrate an anion-exchange chromatography technique to purify human calcium-binding protein S100A12 based on the net surface charge of the protein from an Escherichia coli culture.

Source: Fuehner, S., et al. Purification of Human S100A12 and Its Ion-induced Oligomers for Immune Cell Stimulation J. Vis. Exp. (2019)
In this video, we ...

JoVE Encyclopedia of Experiments

Biological Techniques

Chromatography Techniques

Liquid Phase Isoelectric Focusing: An Electrophoresis Technique to Separate Bioactive Molecules from Crude Gymnema sylvestre Extract

Source: Veerapandian, R., et al. <a href="https://jove.unicartagenaproxy.elogim.com/v/61101">Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative Isoelectric Focusing (IEF) Method</a>. J. Vis. Exp. (2020).
This video describes a technique to separate complex molecules from plant extracts using liquid phase isoelectric focusing. This technique helps purify complex biomolecules in their native state which can be used for various downstream applications.

Source: Veerapandian, R., et al. Separation of Bioactive Small Molecules, Peptides from Natural Sources and Proteins from Microbes by Preparative ...

Electrophoresis Techniques

Two-Dimensional Polyacrylamide Gel Electrophoresis: A Separation Technique for Analysis of Proteins in Complex Protein Mixture Based on Charge and Molecular Weight

Source: Zhan, X., et al. <a href="https://jove.unicartagenaproxy.elogim.com/v/56739">Two-dimensional Gel Electrophoresis Coupled with Mass Spectrometry Methods for an Analysis of Human Pituitary Adenoma Tissue Proteome</a> J. Vis. Exp. (2018)
In this video, we demonstrate a two-dimensional gel electrophoresis method that separates individual proteins from a complex protein mixture obtained from tumor tissues of human nonfunctional pituitary adenoma (NFPA). The proteins are separated based on their electric charge in the first dimension and further separated based on molecular weights in the second dimension.

Source: Zhan, X., et al. Two-dimensional Gel Electrophoresis Coupled with Mass Spectrometry Methods for an Analysis of Human Pituitary Adenoma Tissue ...

Two-dimensional Gel Electrophoresis

Two-dimensional gel electrophoresis is a high-resolution protein separation method first introduced by O&#39;&#160;Farrell and Klose in 1975. This method involves protein separation by two dimensions, mass and charge, making it more accurate than one-dimensional gel electrophoresis.
The first dimension separation uses the isoelectric focusing or IEF technique performed on immobilized pH gradient (IPG) strips that separate proteins according to their isoelectric points.
Biological samples, such as&#160; cells and tissues, are first prepared for IEF by treatment with a buffer containing urea, dithiothreitol, detergents, and ampholytes. Here, urea and detergent solubilize and denature the proteins. Dithiothreitol is a reducing agent that cleaves disulfide bonds. Ampholytes used in a suitable concentration solubilize the protein and maintain pH. The buffer also rehydrates the IPG strip that helps it absorb the proteins before their charge-based separation.
Proteins are amphoteric molecules with positive and negative charges. The amphoteric protein molecules migrate on the pH gradient of the IPG strip under the electric current. Once the proteins reach their isoelectric point, they immobilize because, at this point, they have no net charge. IPG strips have a fixed pH gradient; for instance, strips with a smaller pH range (for example, pH 4-7) can detect proteins with higher accuracy than those with a broader range (pH 3-10). Once the proteins separate, the IPG strips are treated with sodium dodecyl sulfate (SDS) buffer to proceed to the next phase, i.e., mass-based separation using SDS-PAGE (polyacrylamide gel electrophoresis). SDS covers the uncharged protein on the IPG strips with a negative charge, and glycerol reduces electroendosmosis which helps the transfer of proteins from the first to the second dimension.
Generally, bands on the gel can be visualized upon staining. Sometimes radiolabelled samples are used to obtain an autoradiographic image. Samples capable of producing fluorescent images can also be used.
Two-dimensional gel electrophoresis has gained importance owing to the precision of the outcome results. However, the method is unsuitable for distinguishing highly hydrophobic proteins,&#160; proteins with high molecular mass, or those present in very low quantities per cell.

Two-dimensional gel electrophoresis is a high-resolution protein separation method first introduced by O&#39;&#160;Farrell and Klose in 1975. This method ...