Name: synthesis of terpolymers at mild temperatures using dynamic sulfur bonds in poly(s-divinylbenzene)
Uploaded: 2019-05-20T15:00:00
Description: Watch this Scientific Journal Video about Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene at JoVE.com

Thanks are owed to The American Chemical Society Petroleum Research Fund (PRF # 58416-UNI7) for financial support. The authors would like to thank Indiana STEM Louis Stokes Alliance for Minority Participation for student support provided by the National Science Foundation under Grant No. HRD1618-408.

1. Synthesis of poly(S-divinylbenzene)
<ol>
	<li>To prepare poly(S-divinylbenzene), combine elemental sulfur (S8) and divinylbenzene (DVB) at various weight ratios (30:70, 40:60, 50:50, 60:40, 70:30, 80:20, and 90:10 of S8:DVB). Prepare the reaction according to prior methods described below3,25. 
	NOTE: All reactions here were conducted on a 1.00 g scale. A typical reaction contains 500 mg of S8 and 500 mg of DVB.
	<ol>
		...

<ol>
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J., Chong, S. T., Hasell, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sustainable+Inverse-vulcanised+Sulfur+Polymers.">Sustainable Inverse-vulcanised Sulfur Polymers.</a> RSC Advances. 8, 27892-27899 (2018).</li><li>Arslan, M., Kiskan, B., Yagci, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recycling+and+Self-Healing+of+Polybenzoxazines+with+Dynamic+Sulfide+Linkages.">Recycling and Self-Healing of Polybenzoxazines with Dynamic Sulfide Linkages.</a> Scientific Reports. 7, 5207 (2017).</li><li>Zhang, Y. Y., Konopka, K. M., Glass, R. 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The primary benefit of this method is the ability to form polysulfides at mild temperatures, 90 &#176;C versus &#62;159 &#176;C for traditional inverse vulcanization. The extended sulfur chains and sulfur loops in poly(S-DVB) are less stable than S-S bonds in S823,26. Lower temperatures can then be used to cause homolytic scission and thiyl radical formation24. For monomers with melting points well below the reaction temperature...

Conversion of organosulfur compounds to S8 during petroleum refinement has led to the amassing of large stockpiles of sulfur1. Elemental sulfur is primarily used for the production of sulfuric acid and phosphates for fertilizers2. The relative abundance provides a readily available and inexpensive reagent making elemental sulfur an ideal feedstock for materials development.
Inverse vulcanization is a relatively new polymerization technique that repurposes sulfur into functional materials3. The S8 ring converts to a diradical, linear chain upon heating above 159 &#176;C. The thiyl radicals then initiate polymerization with monomers to form polysulfides3. In addition to traditional radical polymerizations, inverse vulcanization has been utilized to initiate polymerization with benzoxazines4. The resulting polymers have been used for a wide range of applications including cathodes in Li-S batteries1,5,6,7, self-healing optical lenses8,9, mercury and oil sorbents5,10,11,12,13,14,15, thermal insulators15, to aid in the slow release of fertilizer16 as well as demonstrating some antimicrobial activity17. One group has provided a thorough systematic analysis of these polysulfides providing more information about the insulating character and mechanical properties with varied S content18. The specific details may aid in further applications development. The dynamic bonds present in these materials have also been utilized to recycle the polysulfides19,20. However, the high temperatures required by inverse vulcanization, typically 185 &#176;C, and lack of miscibility with S8, limit the monomers that can be used3.
Early efforts focused on the polymerization of aromatic hydrocarbons, extended hydrocarbons, and natural monomers with high boiling points5. These methods have been expanded by using poly(S-styrene) as a prepolymer improving miscibility between S8 and more polar monomers including acrylic, allylic, and functionalized styrenic monomers21. Another method utilizes nucleophilic amine activators to enhance reaction rates and lower reaction temperatures22. However, many monomers have boiling points well below 159 &#176;C and thus require an alternate method for polysulfide formation.
In the stable crown form, S-S bonds are the strongest, thus requiring high temperatures for cleavage23. In polysulfides, sulfur is present as linear chains or loops, allowing S-S bonds to be cleaved at much lower temperatures1,24. By using poly(S-DVB) (DVB, divinylbenzene)as a prepolymer, a second monomer with a lower boiling point such as 1,4-cyclohexanedimethanol divinylether (CDE, boiling point of 126 &#176;C), can be introduced24. This work demonstrates further improvement by lowering the reaction temperature to 90 &#176;C with a family of allyl and vinyl ether monomers. Reactions incorporating a second monomer remain solvent-free.

<table>
	<tbody>
		<tr>
			<td>Sulfur, 99.5%, sublimed, ACROS Organics</td>
			<td>Fisher Scientific</td>
			<td>AC201250250SDS</td>
			<td></td>
		</tr>
		<tr>
			<td>divinylbenzene</td>
			<td>Fisher Scientific</td>
			<td>AA4280422</td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-Cyclohexanedimethanol divinyl ether, mixture of isomers</td>
			<td>Sigma Aldrich</td>
			<td>406171</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclohexyl vinyl ether</td>
			<td>Fisher Scientific</td>
			<td>AC395420500</td>
			<td></td>
		</tr>
		<tr>
			<td>Allyl ether</td>
			<td>Sigma Aldrich</td>
			<td>259470</td>
			<td></td>
		</tr>
		<tr>
			<td>maleimide</td>
			<td>Sigma Aldrich</td>
			<td>129585</td>
			<td></td>
		</tr>
		<tr>
			<td>dichlormethane</td>
			<td>Fisher Scientific</td>
			<td>D37</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-dimethylformamide</td>
			<td>Fisher Scientific</td>
			<td>D119</td>
			<td></td>
		</tr>
		<tr>
			<td>Auto sampler Aluminum Sample Pans, 50&#181;L, 0.1mm, Sealed</td>
			<td>Perkin Elmer</td>
			<td>B0143017</td>
			<td></td>
		</tr>
		<tr>
			<td>Auto sampler Aluminum Sample Covers</td>
			<td>Perkin Elmer</td>
			<td>B0143003</td>
			<td></td>
		</tr>
		<tr>
			<td>EMD Millipore 13mm Nonsterile Millex Syringe Filters - Hydrophobic PTFE Membrane, 0.45 um</td>
			<td>Fisher Scientific</td>
			<td>SLFHX13NL</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of terpolymers at mild temperatures using dynamic sulfur bonds in poly(s-divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications lead to sulfur as a cost-efficient reagent for polymer synthesis. Inverse vulcanization combines elemental sulfur with a variety of monomers to form functional polysulfides without the need for solvents. Short reaction times and straight forward synthetic methods have led to rapid expansion of inverse vulcanization. However, high reaction temperatures (&#62;160 &#176;C) limit the types of monomers that can be used. Here, the dynamic sulfur bonds in poly(S-divinylbenzene) are used to initiate polymerization at much lower temperatures. The S-S bonds in the prepolymer are less stable than S-S bonds in S8, allowing radical formation at 90 &#176;C rather than 159 &#176;C. A variety of allyl and vinyl ethers have been incorporated to form terpolymers. The resulting materials were characterized by 1H NMR, gel permeation chromatography, and differential scanning calorimetry, as well as examining changes in solubility. This method expands on the solvent-free, thiyl radical chemistry utilized by inverse vulcanization to create polysulfides at mild temperatures. This development broadens the range of monomers that can be incorporated thus expanding the accessible material properties and possible applications.

Poly(S-DVB) was synthesized according to published protocols using high temperatures (185 &#176;C) to initiate S8 ring cleavage forming radicals3. These radicals then initiate polymerization with DVB. The molten sulfur and liquid DVB eliminate the need for solvents. Within 30 min, sulfur and DVB react completely for form poly(S-DVB). Upon removal from the vial, the polymer is a hard, brittle material at lower sulfur content (30-40%). Mid-range sulfur con...

Watch this Scientific Journal Video about Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene at JoVE.com

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in PolyS-Divinylbenzene

The goal of this protocol is to initiate polymerization using dynamic sulfur bonds in poly(S-divinylbenzene) at mild temperatures (90 &#176;C) without using solvents. Terpolymers are characterized by GPC, DSC and 1H NMR, and tested for changes in solubility.

Synthesis of Terpolymers at Mild Temperatures Using Dynamic Sulfur Bonds in Poly(S-Divinylbenzene)

Elemental sulfur (S8) is a byproduct of the petroleum industry with millions of tons produced annually. Such abundant production and limited applications ...

We've developed a method to initiate polymerization using dynamic sulfur bonds in poly(sulfur-divinylbenzene)at 90 degrees Celsius without the need for solvents. This is substantially lower than traditional methods which require temperatures above 160 degrees Celsius. Lowering the polymerization temperature broadens the range of monomers that can be incorporated into polysulfides by inverse vulcanization.This expands possible materials'properties and possible applications. Inverse vulcanization has produced polysulfides that have been used in lithium sulfide batteries, as infra-red transparent lenses, as mercury and oil sorbents among other applications. This method would enable the development of new materials and likely additional applications.One of the key benefits of this method is the relative ease of the synthesis. This video provides the opportunity to demonstrate how the reaction progresses over time, as well as showing how much the polymers can vary based on the sulfur content and the ratio of the monomers present. To prepare poly(S-divinylbenzene)combine elemental sulfur and divinylbenzene at the desired weight ratio in a one-dram vial equipped with a magnetic stir bar.Place the vial in an oil bath at 185 degrees Celsius for 30 minutes. After the reaction is complete, remove the vial from the oil bath and immediately quench by placing the vial in liquid nitrogen. Then break open the vial to remove the polymer, and repeat this step for each polymer prepared.To synthesize terpolymers, first crush the poly(S-divinylbenzene)with a mortar and pestle for higher surface area interaction with the monomer 1, 4-Cyclohexanedimethanol divinyl ether, or CDE. Then combine the poly(S-divinylbenzene)and CDE at the desired weight ratio on a 600-milligram scale. Place the sample in a oil bath at 90 degrees Celsius for 24 hours.Then cool the sample to room temperature. For reactions that do not result in complete monomer incorporation, dissolve the soluble polymer portions in dichloromethane, and precipitate in cold methanol. For samples with limited solubility, wash the solid polymer samples with cold methanol to remove any unreacted monomer.To synthesize terpolymers using maleimide, combine sulfur and divinylbenzene at a 30-to-70 weight ratio on a five-gram scale as previously described. Combine the pre-polymer with maleimide at a three-to-one weight ratio in a one-dram glass vial equipped with a magnetic stir bar. Dissolve the mixture in 10 milligrams per microliter of dimethylformamide.Then place the vial in an oil bath at 100 degrees Celsius for 24 hours. Next combine poly(S-divinylbenzene)and the desired monomer at a one-to-one weight ratio as described previously to prepare various terpolymers. Remove a sample of the mixture at various time points during the reaction, and dissolve the polymer in 600 microliters of deuterated chloroform for proton NMR analysis.To confirm that sulfur from the polymer rather than elemental sulfur is required for polymerization, prepare samples of sulfur alone, and with CDE, divinylbenzene, and allyl ether as previously described. Analyze the polymers by proton NMR in deuterated chloroform. Integrate the resulting proton NMR spectra to determine the extent of the reaction.Due to the relative low solubility and high polydispersity of most terpolymers, dissolve each polymer in dichloromethane at a high concentration of 75 milligrams per milliliter. Then remove particulates from the soluble portion using a 0.45-micron hydrophobic filter. Analyze the samples by gel permeation chromatography using dichloromethane as the eluent, two MesoPore columns in sequence, and a refractive index detector for analysis.Determine the number average and weight average molecular weights based on the calibration curve of polystyrene standards. To study thermal properties, fill aluminum pans with 30 to 50 milligrams of each polymer, providing enough sample to adequately discern the glass transition temperature from the resulting thermograms. Scan the samples and obtain the thermogram values from the second scan.For solubility studies, weigh approximately 150 milligrams of each polymer into a pre-weighed vial, and dissolve in dichloromethane to reach a concentration of 75 milligrams per milliliter. After eight hours, remove the soluble portion, and wash the insoluble portion with dichloromethane two times. Dry the remaining insoluble sample in an oven for 10 minutes to remove the remaining solvent.After cooling the vial to room temperature, weigh it, and calculate the percent solubility by determining the difference in starting and final weights. Poly(S-divinylbenzene)was synthesized using high temperatures to initiate sulfur ring cleavage-forming radicals, which then initiate polymerization with divinylbenzene. Dynamic sulfur bonds within poly(S-divinylbenzene)can be utilized to initiate polymerization with additional monomers at much lower temperatures.Mono-functional and di-function vinyl and allyl monomers were evaluated, and all were successfully polymerized as confirmed by NMR. The monomer content for all polymerizations were monitored over the course of 48 hours. Control reactions were performed to determine the role of poly(S-divinylbenzene)versus sulfur in the polymerization.The products were examined by proton NMR and TLC to examine changes to the polymer structure, monomer incorporation, and to determine if sulfur was fully incorporated. Various polymerizations were conducted to examine the polymer structure of poly(S-divinylbenzene)CDE. Both increased sulfur content, and the addition of CDE led to a decrease in the glass transition temperature.After an initial decrease in the molecular weight, the addition of CDE led to an overall increase in chain length. Maximum solubility was achieved for poly(s-divinylbenzene)synthesized with 40%to 50%sulfur. The addition of CDE led to decreased polymer solubility.For high-sulfur-content poly(S-divinylbenzene)low solubility was observed, but incorporating CDE substantially improved the solubility. Developing a solvent-free polymerization that occurs at substantially lower temperatures than previously reported broadens the range of monomers that can be incorporated into polysulfides. This may open the door to new applications, or allow materials to be better tailored for a desired function.A small amount of gas is produced during the synthesis of poly(sulfur-divinylbenzene)Vials should only be filled half-full to prevent a buildup of pressure. Samples should be vented prior from removing them from the hood to ensure the gas is not inhaled.

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Organic Chemistry

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Unit 1

Reactions of Alkenes

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Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent reactions with azides to form cyanocarbene intermediates. The synthesis of hypervalent iodonium alkynyl triflates can be facile, but difficulties stem from their isolation and reactivity. In particular, the necessity to use filtration under inert atmosphere at -45 &deg;C for some HIATs requires special care and equipment. Once isolated, the compounds can be stored and used in reactions with azides to form cyanocarbene intermediates. 
The evidence for cyanocarbene generation is shown by visible extrusion of dinitrogen as well as the characterization of products that occur from O-H insertion, sulfoxide complexation, and cyclopropanation. A side reaction of the cyanocarbene formation is the generation of a vinylidene-carbene and the conditions to control this process are discussed. There is also potential to form a hypervalent iodonium alkenyl triflate and the means of isolation and control of its generation are provided. The O-H insertion reaction involves using a HIAT, sodium azide or tetrabutylammonium azide, and methanol as solvent/substrate. The sulfoxide complexation reaction uses a HIAT, sodium azide or tetrabutylammonium azide, and dimethyl sulfoxide as solvent. The cyclopropanations can be performed with or without the use of solvent. The azide source must be tetrabutylammonium azide and the substrate shown is styrene.

Herein is described the synthesis, isolation, and reactions of hypervalent iodonium alkynyl triflates (HIATs) with azides to generate cyanocarbenes. The procedures will involve air-sensitive and cryogen techniques, including cold filtration under an inert atmosphere. Handling and safety of the synthesized compounds will also be discussed.

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent ...

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Magnetic and plasmonic properties combined in a single nanoparticle provide a synergy that is advantageous in a number of biomedical applications including contrast enhancement in novel magnetomotive imaging modalities, simultaneous capture&#160;and detection of circulating tumor cells (CTCs),&#160;and multimodal molecular imaging combined with photothermal therapy of cancer cells. These applications have stimulated significant interest in development of protocols for synthesis of magneto-plasmonic nanoparticles with optical absorbance in the near-infrared (NIR) region and a strong magnetic moment. Here, we present a novel protocol for synthesis of such hybrid nanoparticles that is based on an oil-in-water microemulsion method. The unique feature of the protocol described herein is synthesis of magneto-plasmonic nanoparticles of various sizes from primary blocks which also have magneto-plasmonic characteristics. This approach yields nanoparticles with a high density of magnetic and plasmonic functionalities which are uniformly distributed throughout the nanoparticle volume. The hybrid nanoparticles can be easily functionalized by attaching antibodies through the Fc moiety leaving the Fab portion that is responsible for antigen binding available for targeting.

Here, we describe a protocol for synthesis of magneto-plasmonic nanoparticles with a strong magnetic moment and a strong near-infrared (NIR) absorbance. The protocol also includes antibody conjugation to the nanoparticles through the Fc moiety for various biomedical applications which require molecular specific targeting.

Magnetic and plasmonic properties combined in a single nanoparticle provide a synergy that is advantageous in a number of biomedical applications ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of trifluoromethoxylated aromatic compounds remains a formidable challenge in organic synthesis. Conventional approaches often suffer from poor substrate scope, or require use of highly toxic, difficult-to-handle, and/or thermally labile reagents. Herein, we report a user-friendly protocol for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate using 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one (Togni reagent II). Treating methyl 4-(N-hydroxyacetamido)benzoate (1a) with Togni reagent II in the presence of a catalytic amount of cesium carbonate (Cs2CO3) in chloroform at RT afforded methyl 4-(N-(trifluoromethoxy)acetamido)benzoate (2a). This intermediate was then converted to the final product methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) in nitromethane at 120 &#176;C. This procedure is general and can be applied to the synthesis of a broad spectrum of ortho-trifluoromethoxylated aniline derivatives, which could serve as useful synthetic building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and functional materials.

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of ...

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

DNA-magnetic Particle Binding Analysis by Dynamic and Electrophoretic Light Scattering

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the evaluation of DNA-magnetic particles binding via dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Analysis by DLS provides valuable information on the physicochemical properties of particles including particle size, polydispersity, and zeta potential. The latter describes the surface charge of the particle which plays major role in electrostatic binding of materials such as DNA. Here, a comparative analysis exploits three chemical modifications of nanoparticles and microparticles and their effects on DNA binding and elution. Chemical modifications by branched polyethylenimine, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane are investigated. Since DNA exhibits a negative charge, it is expected that zeta potential of particle surface will decrease upon binding of DNA. Forming of clusters should also affect particle size. In order to investigate the efficiency of these particles in isolation and elution of DNA, the particles are mixed with DNA in low pH (~6), high ionic strength and dehydration environment. Particles are washed on magnet and then DNA is eluted by Tris-HCl buffer (pH = 8). DNA copy number is estimated using quantitative polymerase chain reaction (PCR). Zeta potential, particle size, polydispersity and quantitative PCR data are evaluated and compared. DLS is an insightful and supporting method of analysis that adds a new perspective to the process of screening of particles for DNA isolation.

This protocol describes the synthesis of magnetic particles and evaluation of their DNA-binding properties via dynamic and electrophoretic light scattering. This method focuses on monitoring changes in particle size, their polydispersity and zeta potential of particle surface which play major role in binding of materials such as DNA.

Isolation of DNA using magnetic particles is a field of high importance in biotechnology and molecular biology research. This protocol describes the ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...