Name: preparation of poly(pentafluorophenyl acrylate) functionalized sio2 beads for protein purification
Uploaded: 2018-11-19T14:00:00
Description: Watch this Scientific Journal Video about Preparation of Polypentafluorophenyl acrylate Functionalized SiO2 Beads for Protein Purification at JoVE.com

This work was supported by Agency for Defense Development (Grant No. UD170039ID).

1. Preparation of Poly(PFPA) Homopolymer
<ol>
	<li>Recrystallization of AIBN
	<ol>
		<li>Combine 5 g of 2,2&#8217;-azobis(2-methylpropionitrile) (AIBN) with 25 mL of methanol in a 250 mL beaker. Immerse the beaker in a 60 &#176;C oil bath, then vigorously stir the mixture with a stir bar until AIBN is fully dissolved.</li>
		<li>Filter the warm solution through filter paper (5-8 &#956;m particle retention) and store the filtrate at 4 &#176;C to allow the crystals to form slowly.</li>
		<li>Collect the recrystallized AI...

<ol>
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J., Theato, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+surface+coatings+based+on+polysilsesquioxanes:+controlled+functionalization+for+specific+protein+immobilization.">Reactive surface coatings based on polysilsesquioxanes: controlled functionalization for specific protein immobilization.</a> Langmuir. 25 (17), 10068-10076 (2009).</li><li>Kessler, D., Theato, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+surface+coatings+based+on+polysilsesquioxanes:+defined+adjustment+of+surface+wettability.">Reactive surface coatings based on polysilsesquioxanes: defined adjustment of surface wettability.</a> Langmuir. 25 (24), 14200-14206 (2009).</li><li>Kessler, D., Nilles, K., Theato, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modular+approach+towards+multi-functional+surfaces+with+adjustable+and+dual-responsive+wettability+using+a+hybrid+polymer+toolbox.">Modular approach towards multi-functional surfaces with adjustable and dual-responsive wettability using a hybrid polymer toolbox.</a> Journal of Materials Chemistry. 19 (43), 8184-8189 (2009).</li><li>Eberhardt, M., Mruk, R., Zentel, R., Theato, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+pentafluorophenyl(meth)acrylate+polymers:+new+precursor+polymers+for+the+synthesis+of+multifunctional+materials.">Synthesis of pentafluorophenyl(meth)acrylate polymers: new precursor polymers for the synthesis of multifunctional materials.</a> European Polymer Journal. 41 (7), 1569-1575 (2005).</li><li>Jochum, F. 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The synthesis of poly(PFPA) grafted SiO2 beads is illustrated in Figure 1. By employing APTMS as a linker molecule, poly(PFPA) brushes covalently grafted to SiO2 substrate can be prepared via a simple two-step process. Although some of the PFP units are sacrificed for the reaction with APTMS, a large number of the PFP units are expected to remain available for later reaction with either amino-PEG or antibodies. The PFP groups are known to form low energy surfaces so pol...

An erratum was issued for: <a href="https://www.jove.com/video/58843/preparation-poly-pentafluorophenyl-acrylate-functionalized-sio2-beads">Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification</a>.&#160; Throughout the article, the term &#34;3-aminopropyltriethoxysilane&#34; has been replaced with &#34;3-aminopropyltrimethoxysilane&#34;, and &#34;APTES&#34; with &#34;APTMS&#34;.

Erratum: Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification

Reactive polymer brushes have received much interest in recent years. They can be used to immobilize functional molecules on organic or inorganic materials to create activated surfaces with applications in areas such as detection and separation1,2,3,4,5. Among the reactive polymers reported, those containing pentafluorophenyl ester units are particularly useful due to their high reactivity with amines and resistance toward hydrolysis6. One such polymer is poly(PFPA), and it can be readily functionalized post-polymerization with molecules containing primary or secondary amines7,8,9,10. In one example, poly(PFPA) brushes were reacted with amino-spiropyrans to create light-responsive surfaces7.
The preparation of poly(PFPA) and its applications have been described in a number of previous publications6,7,8,9,10,11,12,13,14,15,16,17. In particular, Theato and co-workers reported the synthesis of poly(PFPA) brushes via both &#34;grafting to&#34; and &#34;grafting from&#34; methods7,8,10,11,12. In the &#34;grafting to&#34; approach, a poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylate) (poly(MSSQ-PFPA)) hybrid polymer was synthesized8,10,11,12. The poly(MSSQ) component was able to form strong adhesion with a number of different organic and inorganic surfaces, thus allowing the poly(PFPA) component to form a brush layer on the coated material surface. In the &#34;grafting from&#34; approach, surface initiated reversible addition and fragmentation chain transfer (SI-RAFT) polymerization was employed to prepare poly(PFPA) brushes7. In this case, a surface immobilized chain transfer agent (SI-CTA) was first covalently attached to the substrate via silica-silane reaction. The immobilized SI-CTA then participated in the SI-RAFT polymerization of PFPA monomers, generating densely packed poly(PFPA) brushes with stable covalent linkage to the substrate.
By utilizing the poly(PFPA) brushes synthesized via SI-RAFT polymerization, we recently demonstrated the immobilization of antibodies on poly(PFPA) grafted silica particles and their subsequent application in protein purification18. The use of poly(PFPA) brushes for antibody immobilization was found to resolve a number of issues associated with current protein separation through IP. Conventional IP relies on the use of Protein A/G as a linker for antibody immobilization19,20,21. Since the use of Protein A/G allows the antibodies to be attached with a specific orientation, high target antigen recovery efficiency is achieved. However, the use of Protein A/G suffers from non-specific protein interaction as well as the loss of antibodies during protein recovery, both of which contribute to a high level of background noise. To resolve these shortcomings, direct crosslinking of the antibodies to a solid support has been explored22,23,24. The efficiency of such techniques is typically low due to the random orientation of the crosslinked antibodies. For the poly(PFPA) grafted substrate, the immobilization of antibodies is permanent, achieved through exchange reaction between PFP units and amine functionalities on antibodies. Although the antibody orientation is still random, the system benefits from having many reactive PFP sites, controllable by the degree of polymerization. Furthermore, we showed that by partial substitution of PFP units with amino-PEG, surface hydrophilicity can be tuned, further improving the protein recovery efficiency of the system18. Overall, the poly(PFPA) grafted silica particles were shown to be an effective alternative to traditional IP with reasonable efficiency as well as much cleaner background.
In this contribution, we report an alternative method to prepare poly(PFPA) grafted surface for antibody immobilization and IP application. In a simple two-step process, as illustrated in Figure 1, an APTMS linker molecule is first deposited onto the silica surface, then the poly(PFPA) polymer is covalently attached to the linker molecule through the reaction between the PFP units on the polymer and the amine functions on APTMS. This preparation method allows for the permanent crosslinking of poly(PFPA) to a substrate surface, but avoids the many complications associated with SI-CTA synthesis and SI-RAFT polymerization of poly(PFPA) brushes. Partial substitution of the PFP units with amino-PEG can still be performed, allowing fine-tuning of the polymer brush surface properties. We show the poly(PFPA) grafted silica beads thus prepared can be immobilized with antibodies and used for protein enrichment via IP. The detailed bead preparation procedure, antibody immobilization, and IP testing are documented in this article, for readers interested in seeking an alternative to conventional Protein A/G based IP.

<table>
	<tbody>
		<tr>
			<td>2,2-Azobisisobutyronitrile, 99%</td>
			<td>Daejung Chemicals</td>
			<td>1102-4405</td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl alcohol for HPLC, 99.9%</td>
			<td>Duksan Pure Chemicals</td>
			<td>d62</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenylmagnesium bromide solution 1.0&#160;M in THF</td>
			<td>Sigma-Aldrich</td>
			<td>331376</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon disulfide anhydrous, &#8805;99%</td>
			<td>Sigma-Aldrich</td>
			<td>335266</td>
			<td></td>
		</tr>
		<tr>
			<td>Benzyl bromide, 98%</td>
			<td>Sigma-Aldrich</td>
			<td>B17905</td>
			<td></td>
		</tr>
		<tr>
			<td>Petroleum ether, 90%</td>
			<td>Samchun Chemicals</td>
			<td>P0220</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl ether, 99%</td>
			<td>Daejung Chemicals</td>
			<td>4025-4404</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate anhydrous, powder,&#160;99%</td>
			<td>Daejung Chemicals</td>
			<td>5514-4405</td>
			<td></td>
		</tr>
		<tr>
			<td>Pentafluorophenyl acrylate</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-264001</td>
			<td>contains inhibitor</td>
		</tr>
		<tr>
			<td>Aluminium oxide, activated, basic, Brockmann I</td>
			<td>Sigma-Aldrich</td>
			<td>199443</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride (NaCl)</td>
			<td>Daejung Chemicals</td>
			<td>7548-4400</td>
			<td></td>
		</tr>
		<tr>
			<td>Anisole anhydrous, 99.7%</td>
			<td>Sigma-Aldrich</td>
			<td>296295</td>
			<td></td>
		</tr>
		<tr>
			<td>Silica nanoparticle</td>
			<td>Microparticles GmbH</td>
			<td>SiO2-R-0.7</td>
			<td>5% w/v aqueous suspension</td>
		</tr>
		<tr>
			<td>3-Aminopropyltrimethoxysilane, &#62;96.0%</td>
			<td>Tokyo Chemical Industry</td>
			<td>T1255</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide for HPLC, &#8805;99.7%</td>
			<td>Sigma-Aldrich</td>
			<td>34869</td>
			<td></td>
		</tr>
		<tr>
			<td>Amino-terminated poly(ethylene glycol) methyl ether</td>
			<td>Polymer Source</td>
			<td>P16082-EGOCH3NH2</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline tablet</td>
			<td>Takara</td>
			<td>T9181</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Calbiochem</td>
			<td>9480</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-HCl (pH 8.0)</td>
			<td>Invitrogen</td>
			<td>AM9855G</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Invitrogen</td>
			<td>AM9640G</td>
			<td></td>
		</tr>
		<tr>
			<td>NP-40</td>
			<td>VWR</td>
			<td>E109-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Invitrogen</td>
			<td>15514-011</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol</td>
			<td>Biosesang</td>
			<td>D1037</td>
			<td></td>
		</tr>
		<tr>
			<td>Protease inhibitor</td>
			<td>Merck</td>
			<td>535140-1MLCN</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromo phenol blue</td>
			<td>Sigma-Aldrich</td>
			<td>B5525-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-HCl (pH 6.8)</td>
			<td>Biosolution</td>
			<td>BT033</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate</td>
			<td>Biosolution</td>
			<td>BS003</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>Gibco</td>
			<td>21985-023</td>
			<td></td>
		</tr>
		<tr>
			<td>PKR Antibody</td>
			<td>Cell Signaling Technology</td>
			<td>12297S</td>
			<td></td>
		</tr>
		<tr>
			<td>GAPDH Antibody</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-32233</td>
			<td></td>
		</tr>
		<tr>
			<td>Normal Rabbit IgG</td>
			<td>Cell Signaling Technology</td>
			<td>2729S</td>
			<td></td>
		</tr>
		<tr>
			<td>HeLa</td>
			<td>Korea Cell Line Bank</td>
			<td>10002</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>DAIHAN Scientific</td>
			<td>WUC-D10H</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonicator</td>
			<td>BMBio</td>
			<td>BR2006A</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge I</td>
			<td>Eppendorf</td>
			<td>5424 R</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge II</td>
			<td>LABOGENE</td>
			<td>1736R</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotator</td>
			<td>FINEPCR</td>
			<td>ROTATOR/AG</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum oven</td>
			<td>DAIHAN Scientific</td>
			<td>ThermoStable OV-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel permeation chromatography (THF)</td>
			<td>Agilent Technologies</td>
			<td>1260 Infinity II</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray photoelectron spectrometer</td>
			<td>Thermo VG Scientific</td>
			<td>Sigma Probe</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynamic light scattering</td>
			<td>Malvern Instruments</td>
			<td>ZEN 3690</td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of poly(pentafluorophenyl acrylate) functionalized sio2 beads for protein purification

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent immunoprecipitation (IP) application. The poly(PFPA) grafted surface is prepared via a simple two-step process. In the first step, 3-aminopropyltrimethoxysilane (APTMS) is deposited as a linker molecule onto the silica surface. In the second step, poly(PFPA) homopolymer, synthesized via the reversible addition and fragmentation chain transfer (RAFT) polymerization, is grafted to the linker molecule through the exchange reaction between the pentafluorophenyl (PFP) units on the polymer and the amine groups on APTMS. The deposition of APTMS and poly(PFPA) on the silica particles are confirmed by X-ray photoelectron spectroscopy (XPS), as well as monitored by the particle size change measured via dynamic light scattering (DLS). To improve the surface hydrophilicity of the beads, partial substitution of poly(PFPA) with amine-functionalized poly(ethylene glycol) (amino-PEG) is also performed. The PEG-substituted poly(PFPA) grafted silica beads are then immobilized with antibodies for IP application. For demonstration, an antibody against protein kinase RNA-activated (PKR) is employed, and IP efficiency is determined by Western blotting. The analysis results show that the antibody immobilized beads can indeed be used to enrich PKR while non-specific protein interactions are minimal.

A schematic for the preparation of poly(PFPA) grafted SiO2 beads, with or without PEG substitution is shown in Figure 1. To monitor the APTMS and poly(PFPA) grafting process, bare SiO2 beads, APTMS functionalized SiO2 beads, and poly(PFPA) grafted SiO2 beads are characterized by both DLS (Figure 2) and XPS (Figure 3). IP efficiencies of the beads are determ...

Watch this Scientific Journal Video about Preparation of Polypentafluorophenyl acrylate Functionalized SiO2 Beads for Protein Purification at JoVE.com

Preparation of Polypentafluorophenyl acrylate Functionalized SiO2 Beads for Protein Purification

A protocol for the preparation of poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads is presented. The poly(PFPA) functionalized surface is then immobilized with antibodies and used successfully for the protein separation through immunoprecipitation.

Preparation of Poly(pentafluorophenyl acrylate) Functionalized SiO2 Beads for Protein Purification

We demonstrate a simple method to prepare poly(pentafluorophenyl acrylate) (poly(PFPA)) grafted silica beads for antibody immobilization and subsequent ...

This method can be used to prepare biomolecule-activated surfaces, which have applications in areas such as drug delivery, biological target detection, and bio separation. The main advantage of this technique is that the poly PFPA brushes are highly reactive with amines, and the immobilization of antibodies is achieved by incubation in buffer solution for a few hours. The implications of this technique extend toward the protein purification through immunopurification, as the immobilized antibody can successfully bind with target antigens.Though this method is demonstrate for antibody mobilization and protein purification, it can also be applied to other systems requiring biomolecular mobilization. To treat silicon dioxide beads with APTES, first obtain silicon dioxide particles in the form of a 5%weight volume aqueous suspension. Combine 0.8 milliliters of silicon dioxide suspension with 40 milligrams of APTES, and eight milliliters of methanol in a 20 milliliter scintillation vial equipped with a stir bar.Allow the reaction to proceed at room temperature for five hours with vigorous stirring. After five hours, transfer the solution to a conical tube. To isolate the APTES functionalized silicone dioxide beads, centrifuge the solution at 10, 000 G for five minutes.Then remove the supernatant. Now wash the beads by redispursing them in three milliliters of fresh methanol. Shake the tube by hand for mixing, but if necessary, improve the dispersion by sonication in a water bath for a few seconds.Centrifuge as before, and repeat the wash step one more time. Combine the methanol wash silicone dioxide beads with three milliliters of dimethyl sulfoxide, or DMSO. Shake the mixture by hand, or if necessary, sonicate for a few seconds until the beads are fully dispersed in the DMSO.Following centrifugation at before, remove the supernatant. Repeat the centrifugation step a final time to ensure complete solvent exchange from methanol to DMSO. To prepare the poly PFPA solution, dissolve 20 milligrams of poly PFPA in two milliliters of DMSO in a 20 milliliter scintillation vial.To prepare PEG solution, dissolve amine functionalized PEG in one milliliter of DMSO. Now transfer the PEG solution to the poly PFPA solution. React at room temperature for one hour with vigorous stirring.Transfer one milliliter of the APTES functionalized silicon dioxide beads suspended in DMSO into the PEG substituted poly PFPA solution. Allow the grafting between poly PFPA and APTES functionalized silicon dioxide beads to proceed at room temperature for one hour with vigorous stirring. Then isolate the beads by centrifugation at 10, 000 G for five minutes, followed by the removal of the supernatant.Wash the beads by adding three milliliters of DMSO, and mix by hand or with a few seconds of sonication. Centrifuge the beads as before. And remove the supernatant before repeating the DMSO wash twice.Wash the beads twice more with three milliliters of triple distilled water. Then mix by hand or with a few seconds of sonication. Centrifuge the beads as before and remove the supernatant.Finally dry the beads at 40 degrees celsius in a vacuum oven overnight. Add five milligrams of poly PFPA grafted silicon dioxide beads to a 1.5 milliliter microcentrifuge tube. Wash the beads by adding 800 microliters of PBS, and mix well by vortexing.Centrifuge the beads at 10, 000 G at room temperature for one minute. Remove the supernatant, and repeat the wash step three times. Now add 350 microliters of fresh PBS, 50 microliters of 0.1%PBST, and 6.67 micrograms of the antibody.Incubate approximately 20 hours on a rotator at four degrees celsius. The next day, wash the beads and centrifuge at 400 G and four degrees celsius for one minute. Then remove the supernatant and carefully add 400 microliters of lysis buffer.Gently resuspend the beads by pipetting up and down five times. Repeat this wash step three times. After the final wash, remove as much of the supernatant as possible.Prepare cells and lysis buffer as described in the text protocol. Then resuspend the cell pellet with 400 microliters of the lysis buffer. Sonicate the cells using an ultra sonicator.After sonication, vortex briefly. Then centrifuge the lysate at 20, 000 G at four degrees celsius for 10 minutes. Transfer the supernatant to a new, 1.5 milliliter centrifuge tube.To perform immunoprecipitation, transfer 300 microliters of cell lysate to previously prepared antibody immobilized poly PFPA grafted silicon dioxide beads. Retain 30 microliters of the cell lysate as the input sample in a new microcentrifuge tube. Incubate the lysate beads mixture for three hours on a rotator at four degrees celsius.Following incubation, centrifuge the mixture at 400 G at four degrees celsius for one minute. Remove the supernatant, and carefully add 400 microliters of wash buffer. Gently resuspend the beads by pipetting up and down about five times.After three washes, remove as much of the supernatant as possible. Add 30 microliters of 2x SDS loading dye to the beads and to the input sample. Then heat them for 10 minutes at 95 degrees celsius.After heating, analyze the sample using western blotting, or store the sample at minus 20 degrees celsius. The functionalized silica beads are examined by x-ray photoelectron spectroscopy, or XPS, to determine surface composition. Representative XPS data are shown here.Following APTES treatment, the nitrogen 1s peak associated with the amine group zone APTES is detected. Following poly PFPA treatment, the fluorine 1s peak associated with the PFP units on the polymer is detected. Protein kinase RNA activated, or PKR enrichment through immunoprecipitation is performed, and the alluded protein sample are analyzed using western blotting.As expected, beads immobilized with no antibody, or a non-specific antibody mixuture show no PKR recovery. The beads incubated with anti-PKR can successfully enrich PKR as indicated by the presence of a PKR band and the absence of GAPDH band. While attempting this procedure, it's important to remember that when comparing of systems, the IP experiments as well as the subsequent western blotting analysis should be done simultaneously.After its development, this technique can be used for the immobilization of different biomolecular or material substrate. Moreover, this method has the additional benefit of tuning Only surface property to be tailored to suit each application's need.

preparation-polypentafluorophenyl-acrylate-functionalized-sio2-beads

Research

JoVE Journal

Chemistry

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Microbubble Fabrication of Concave-porosity PDMS Beads

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is particularly useful for separations applications. Porous polydimethylsiloxane (PDMS) beads can be produced by heat-curing such an emulsion, allowing the interface between the aqueous and aliphatic phases to mold the morphology of the polymer. In the procedures described here, both polymer and crosslinker (triethoxysilane) are sonicated together in a cold-bath sonicator. Following a period of cross-linking, emulsions are added dropwise to a hot surfactant solution, allowing the aqueous phase of the emulsion to separate, and forming porous polymer beads. We demonstrate that this method can be tuned, and the SAV ratio optimized, by adjusting the electrolyte content of the aqueous phase in the emulsion. Beads produced in this way are imaged with scanning electron microscopy, and representative SAV ratios are determined using Brunauer&#8211;Emmett&#8211;Teller (BET) analysis. Considerable variability with the electrolyte identity is observed, but the general trend is consistent: there is a maximum in SAV obtained at a specific concentration, after which porosity decreases markedly.

Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized.

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is ...

Immobilization of Multi-biocatalysts in Alginate Beads for Cofactor Regeneration and Improved Reusability

We have recently developed a simple, reusable and coupled whole-cell biocatalytic system with the capability of cofactor regeneration and biocatalyst immobilization for improved production yield and sustained synthesis. Described herewith is the experimental procedure for the development of such a system consisting of two E. coli strains that express functionally complementary enzymes. Together, these two enzymes can function co-operatively to mediate the regeneration of expensive cofactors for improving the product yield of the bioreaction. In addition, the method of synthesizing an immobilized form of the coupled biocatalytic system by encapsulation of whole cells in calcium alginate beads is reported. As an example, we present the improved biosynthesis of L-xylulose from L-arabinitol by coupling E. coli cells expressing the enzymes L-arabinitol dehydrogenase or NADH oxidase. Under optimal conditions and using an initial concentration of 150 mM L-arabinitol, the maximal L-xylulose yield reached 96%, which is higher than those reported in the literature. The immobilized form of the coupled whole-cell biocatalysts demonstrated good operational stability, maintaining 65% of the yield obtained in the first cycle after 7 cycles of successive re-use, while the free cell system almost completely lost the catalytic activity. Therefore, the methods reported here provides two strategies that could help improve the industrial production of L-xylulose, as well as other value-added compounds requiring the use of cofactors in general.

Presented is the protocol for co-immobilizing whole-cell biocatalysts for cofactor regeneration and improved reusability, using the production of L-xylulose as an example. The cofactor regeneration is achieved by coupling two Escherichia coli strains expressing functionally complementary enzymes; the whole-cell biocatalyst immobilization is achieved by cell encapsulation in calcium alginate beads.

We have recently developed a simple, reusable and coupled whole-cell biocatalytic system with the capability of cofactor regeneration and biocatalyst ...

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar polyaromatic units, which are two corannulene moieties and a racemic hexahelicene linking them. The compound described in this work is a good host for fullerenes. Several common organic reactions, such as free-radical reactions, C-C coupling or click chemistry, are employed demonstrating the versatility of functionalization that this compound can accept. All of these reactions work for planar aromatic molecules. With subtle modifications, it is possible to achieve similar results for nonplanar polyaromatic compounds.

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Here, we present a protocol to synthesize a complex organic compound comprised of three nonplanar polyaromatic units, assembled easily with reasonable yields.

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar ...

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO2 has been supported on the surface of SiO2 by means of two different methods: (i) by the in situ formation of TiO2 in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO2 powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS). For comparison, TiO2 nanoparticles were also deposited on the surfaces of a more reactive SiO2 prepared by a hydrolysis-controlled sol-gel technique as well as through a sol-gel route from TiO2 and SiO2 precursors. The combination of TiO2 and SiO2, through interfacial Ti-O-Si bonds, was confirmed by FTIR spectroscopy and the photocatalytic activities of the obtained composites were tested for photocatalytic degradation of NO according to the ISO standard method (ISO 22197&#8722;1). The electron microscope images of the obtained materials showed that variable photocatalyst coverage of the support surface can successfully be achieved but the photocatalytic activity towards NO removal was found to be affected by the preparation method and the nitrate selectivity is adversely affected by Ti-O-Si bonding.

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

The focus of the present work is to establish means to generate and quantify levels of Ti-O-Si linkages and to correlate these with the photocatalytic properties of the supported TiO2.

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical ...

Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This work presents the preparation of methionine functionalized biocompatible block copolymers via RAFT polymerization. Firstly, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-aminopropyl)methacrylamide (BNHEMA-b-APMA, BA) was synthesized via RAFT polymerization using 4,4&#8217;-azobis(4-cyanovaleric acid) (ACVA) as an initiating agent and 4-cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent. Subsequently, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-guanidinopropyl)methacrylamide (methionine grafted BNHEMA-b-GPMA, mBG) was prepared by modifying amine groups in APMA with methionine and guanidine groups. Three kinds of block polymers, mBG1, mBG2, and mBG3, were synthesized for comparison. A ninhydrin reaction was used to quantify the APMA content; mBG1, mBG2, and mBG3 had 21%, 37%, and 52% of APMA, respectively. Gel permeation chromatography (GPC) results showed that BA copolymers possess molecular weights of 16,200 (BA1), 20,900(BA2), and 27,200(BA3) g/mol. The plasmid DNA (pDNA) complexing ability of the obtained block copolymer gene carriers was also investigated. The charge ratios (N/P) were 8, 16, and 4 when pDNA was complexed completely with mBG1, mBG2, mBG3, respectively. When the N/P ratio of mBG/pDNA polyplexes was higher than 1, the Zeta potential of mBG was positive. At an N/P ratio between 16 and 32, the average particle size of mBG/pDNA polyplexes was between 100-200 nm. Overall, this work illustrates a simple and convenient protocol for the block copolymer carrier synthesis.

This work presents the preparation of methionine functionalized biocompatible block copolymers (mBG) via the reversible addition-fragmentation chain transfer (RAFT) method. The plasmid DNA complexing ability of the obtained mBG and their transfection efficiency were also investigated. The RAFT method is very beneficial for polymerizing monomers containing special functional groups.

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This ...

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the preparation of all-carbon quaternary centers. Though conjugate additions of organometallic reagents are typically performed utilizing highly reactive organolithium or Grignard reagents, organozinc reagents have garnered attention for their enhanced chemoselectivity and mild reactivity. Despite numerous recent advances with more reactive diorganozinc and mixed diorganozinc reagents, the generation of all-carbon quaternary centers via the conjugate addition of functionalized monoorganozinc reagents remains a challenge. This protocol details a convenient and mild &#8220;one-pot&#8221; preparation and copper mediated conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to afford a broad scope of all-carbon quaternary centers in generally excellent yield and diastereoselectivity. Key to the development of this technology is the utilization of DMA as a reaction solvent with TMSCl as a Lewis acid. Notable advantages to this methodology include the operational simplicity of the organozinc reagent preparation afforded by the utilization of DMA as a solvent, as well as an efficient conjugate addition mediated by various Cu(I) and Cu(II) salts. Moreover, an intermediate silyl enol ether can be isolated utilizing a modified workup procedure. The substrate scope is limited to cyclic unsaturated ketones, and the conjugate addition is impeded by stabilized (e.g., allyl, enolate, homoenolate) and sterically encumbered (e.g., neopentyl, o-aryl) monoorganozinc reagents. Conjugate additions to five- and seven-membered rings were effective, albeit in lower yields compared with six-membered ring substrates.

A simple and practical protocol for the efficient conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to furnish all-carbon quaternary centers was developed.

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the ...

Organic Solvent-Based Protein Precipitation for Robust Proteome Purification Ahead of Mass Spectrometry

While multiple advances in mass spectrometry (MS) instruments have improved qualitative and quantitative proteome analysis, more reliable front-end approaches to isolate, enrich, and process proteins ahead of MS are critical for successful proteome characterization. Low, inconsistent protein recovery and residual impurities such as surfactants are detrimental to MS analysis. Protein precipitation is often considered unreliable, time-consuming, and technically challenging to perform compared to other sample preparation strategies. These concerns are overcome by employing optimal protein precipitation protocols. For acetone precipitation, the combination of specific salts, temperature control, solvent composition, and precipitation time is critical, while the efficiency of chloroform/methanol/water precipitation depends on proper pipetting and vial manipulation. Alternatively, these precipitation protocols are streamlined and semi-automated within a disposable spin cartridge. The expected outcomes of solvent-based protein precipitation in the conventional format and using a disposable, two-stage filtration and extraction cartridge are illustrated in this work. This includes the detailed characterization of proteomic mixtures by bottom-up LC-MS/MS analysis. The superior performance of SDS-based workflows is also demonstrated relative to non-contaminated protein.

The present protocol describes solvent-based protein precipitation under controlled conditions for robust and rapid recovery and purification of proteome samples prior to mass spectrometry.

While multiple advances in mass spectrometry (MS) instruments have improved qualitative and quantitative proteome analysis, more reliable front-end ...

Porphyrin-Modified Beads in Flow Cytometry

Porphyrin-Modified Beads for Use as Compensation Controls in Flow Cytometry

Flow cytometry can rapidly characterize and quantify diverse cell populations based on fluorescence measurements. The cells are first stained with one or more fluorescent reagents, each functionalized with a different fluorescent molecule (fluorophore) that binds to cells selectively based on their phenotypic characteristics, such as cell surface antigen expression. The intensity of fluorescence from each reagent bound to cells can be measured on the flow cytometer using channels that detect a specified range of wavelengths. When multiple fluorophores are used, the light from individual fluorophores often spills over into undesired detection channels, which requires a correction to the fluorescence intensity data in a process called compensation. 
Compensation control particles, typically polymer beads bound to a single fluorophore, are needed for each fluorophore used in a cell labeling experiment. Data from compensation particles from the flow cytometer are used to apply a correction to the fluorescence intensity measurements. This protocol describes the preparation and purification of polystyrene compensation beads covalently functionalized with the fluorescent reagent meso-tetra(4-carboxyphenyl) porphine (TCPP) and their application in flow cytometry compensation. In this work, amine-functionalized polystyrene beads were treated with TCPP and the amide coupling reagent EDC (N-(3-dimethylaminopropyl)-N&#8242;-ethylcarbodiimide hydrochloride) at pH 6 and at room temperature for 16 h with agitation. The TCPP beads were isolated by centrifugation and resuspended in a pH 7 buffer for storage. TCPP-related particulates were observed as a byproduct. The number of these particulates could be reduced using an optional filtration protocol. The resultant TCPP beads were successfully used on a flow cytometer for compensation in experiments with human sputum cells labeled with multiple fluorophores. The TCPP beads proved stable following storage in a refrigerator for 300 days.

Author Spotlight: Porphyrin-Modified Beads for Use as Compensation Controls in Flow Cytometry  

The protocol describes how porphyrin-based compensation beads for flow cytometry are prepared by the reaction of amine-functionalized polystyrene beads with the porphyrin TCPP and the amide coupling reagent EDC. A filtration procedure is used to reduce the particulate byproducts.

Flow cytometry can rapidly characterize and quantify diverse cell populations based on fluorescence measurements. The cells are first stained with one or ...

Combining Amine-Functionalized Polystyrene Beads with TCPP Solution

Begin by adding 4.3 milliliters of 0.1 molar MES buffer solution to a 15 milliliter polypropylene tube. Then add 288 microliters of the vortexed amine functionalized polystyrene bead suspension to the 15 milliliter polypropylene tube containing MES buffer. Vortex the MES bead solution for 15 seconds at maximum speed.Next, vortex the one milligram per milliliter TCPP solution for 60 seconds at maximum speed. Then add 1.2 milliliters of this solution to the MES bead suspension. After vortexing the resultant suspension for 15 seconds, cover the tube with foil.