This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. We thank the University of North Carolina Wilmington for providing the seawater.

1. Síntese de 1,4-benzeno-bis (iminoguanidinium) Cloreto (Cl-BBiG) <ol><li> In situ síntese do 1,4-benzeno-bis (iminoguanidinium) Cloreto de Ligand (BBiG-Cl) e sua cristalização com sulfato <ol><li> Adicionar 0,067 g de tereftalaldeído e 2,2 ml de uma solução aquosa 0,5 M de cloreto de aminoguanidinium a 10 ml de água desionizada num balão de 25 ml de fundo redondo equipado com uma barra de agitação magnética. </li><li> Agita-se a solução magneticamente durante quatro horas a 20 ° C. Isto irá dar uma solução ligeiramente amarela de BBiG-Cl. </li><li> Adicionar 0,5 ml de uma solução aquosa 1 M de sulfato de sódio. Isto irá resultar na precipitação imediata de BBiG-SO 4 como um sólido branco cristalino. </li><li> Filtra-se o sólido utilizando filtração sob vácuo para se recuperar BBiG-SO 4. Lava-se o sólido sobre o papel de filtro cinco vezes com alíquotas de 5 ml de água, a fim de obter o sal de sulfato puro. </li><li> Verificar a pureza fase do cristalino BBiG-SO <sub&gt; 4 obtida por difracção de raios X 12. Comparar com o padrão mostrado na Figura 1. </li></ol></li><li> Ex Situ Síntese de 1,4-benzeno-bis (iminoguanidinium) Chloride 11 <ol><li> Adicionar 4 g de tereftalaldeído e 7,26 g de cloreto de aminoguanidinium a 20 ml de etanol num frasco de 50 ml de fundo redondo equipado com uma barra de agitação magnética. </li><li> Aquece-se a solução a 60 ° C utilizando uma placa de aquecimento, e agitar com uma barra de agitação magnética durante 2 horas. Arrefece-se a solução para 20 ° C e deixar repousar durante 3 h, em seguida, recolher o sólido por filtração sob vácuo através de um funil de Buchner de papel-filtro equipado. </li><li> Suspender o sólido obtido em 20 ml de etanol e de calor em uma chapa quente até ferver. Se o sólido não entrar completamente em solução, neste ponto, adicionar pequenas alíquotas (1 ml) de etanol, permitindo que cada vez que a solução atingir a temperatura de ebulição, até que todo o sólido estar dissolvido. </li><li> Deixar o balão arrefecer até à temperatu quartoRe, em seguida, coloque em uma temperatura de 0 ° C congelador durante a noite. Recolher o sólido por filtração através de um filtro de papel equipado funil de Buchner utilizando filtração sob vácuo. </li><li> Confirmar a identidade e pureza do BBiG-Cl por 1 H espectroscopia de RMN 13. Comparar com o espectro apresentado na Figura 2. </li></ol></li></ol> 2. Separação de sulfato da água do mar <ol><li> Cristalização de sulfato como BBiG-SO 4 NOTA: A quantidade de BBiG-Cl necessário para remover o sulfato depende da quantidade exacta de sulfato na água do mar. Verificou-se que a utilização de 1,5 equivalentes de BBiG-Cl em relação ao sulfato de resultados na remoção de 99% de sulfato. A água do mar usada no presente protocolo tem uma concentração de sulfato de 30 mM, tal como determinado por titulação com BaCl2. <ol><li> Filtra-se a água do mar com um filtro de seringa de 0,22? M ou com membrana de filtração de tamanho de poro pequeno para remover as partículas em suspensão e organismos bio. </li><li> Adicione uma 30solução mM de BBiG-Cl usando água desionizada e sólido BBiG-Cl preparada tal como descrito na secção anterior. </li><li> Adicionar a solução BBiG-Cl à água do mar em 1.5: (v / v), proporção 1. </li><li> Agita-se a mistura durante algumas horas para assegurar a remoção quantitativa (&gt; 99%) de sulfato. </li><li> Recolher o sólido por filtração através de um filtro de papel equipado funil de Buchner utilizando filtração sob vácuo. Lava-se o sólido sobre o papel de filtro cinco vezes com alíquotas de 5 ml de água. </li><li> Seca-se o sólido isolado sob vácuo e pesá-lo para determinar o rendimento. </li></ol></li><li> Recuperação Ligand <ol><li> Adicionar 53,1 mg de BBiG-SO 4 a uma solução de 2 ml de NaOH (10%) num frasco de cintilação de 20 mL equipado com uma barra de agitação magnética. </li><li> Agita-se a mistura durante duas horas a 20 ° C. Um precipitado de cor ligeiramente amarela irá formar. </li><li> Filtrar o sólido através de um filtro de papel equipado funil de Buchner utilizando filtração sob vácuo. Lava-se o sólido sobre o papel de filtro com 0,2ml de água, e seco sob vácuo. </li><li> Caracterizar o sólido recuperado por RMN 13 para confirmar a sua identidade como a base livre de bis (guanidina). Comparar com o espectro de RMN mostrado na Figura 3. </li></ol></li><li> A determinação da quantidade de sulfato Removido Seawater por p líquido de contagem de cintilação CUIDADO: Esta técnica envolve a utilização de radioisótopos, que representam uma classe diferente de perigos do que o que é normalmente encontrado na maioria dos laboratórios. Equipamento especial de protecção contra radiações normalmente é exigida durante o manuseio dos radionuclídeos. Assim, é essencial que o procedimento é seguido com atenção e que um oficial de segurança é consultado para aconselhamento e orientação. <ol><li> Calcular o volume da solução de reserva de o enxofre-35 radioisótopo (5 mCi / ml) usadas para assegurar que não é mais de 5 milhões de contagens por minuto (cpm) por mililitro de solução de água salgada, utilizando as seguintes equações (cpm e Curies (Ci ) são ambas unidades de medida fou radioactividade): <img alt="equação 1" src="/files/ftp_upload/54411/54411eq1.jpg" /> <img alt="equação 2" src="/files/ftp_upload/54411/54411eq2.jpg" /> <img alt="equação 3" src="/files/ftp_upload/54411/54411eq3.jpg" /></li><li> Pico 25 ml de água do mar com 0,0112 ml de solução 5,0 mCi / ml de 35 S uma solução de sulfato de sódio radiomarcado. </li><li> Preparar soluções de 0, 15, 30, 33, 45, e 60 mM de Cl-BBiG em água desionizada e combinar 0,750 ml destas soluções com um volume igual de sulfato de S-35 marcado radioactivamente água do mar enriquecida em um tubo de centrífuga de 2 ml. </li><li> Agita-se a mistura através de uma roda rotativa ou de vórtice, em um / caixa de ar incubadora mantida a uma temperatura constante de 25 ± 0,2 ° C durante 24 h. </li><li> Centrifugar as soluções a 1.500 xg durante 10 min a 25 ° C. </li><li> Após centrifugação, retirar 1,2 ml de cada solução, utilizando uma seringa, seguida de filtração através de um filtro de seringa de 0,22 um para retirar a suspensão<html> precipitado. Pipetar 1,0 ml de cada uma destas soluções em 20 ml de cocktail de cintilação em frascos de cintilação em polipropileno. A solução não contendo BBiG-Cl (a solução de controlo) deve ser diluída dez-vezes com água desionizada antes da adição do cocktail de cintilação. </li><li> Coloque os frascos de cintilação contendo as amostras e o cocktail de cintilação em um contador de cintilação líquida e deixe descansar por 1 hora antes de contar para permitir que as amostras para dark-se adaptar. NOTA: antes da contagem das amostras, calibrar o instrumento e permite que cada amostra para contar durante 30 min. Contagem de frascos adicionais contendo apenas cocktail de cintilação a fim de permitir uma correcção de fundo que é utilizado na determinação das concentrações de sulfato em solução. </li><li> Determinar a quantidade de sulfato de removido, utilizando as seguintes equações: <img alt="equação 4" src="/files/ftp_upload/54411/54411eq4.jpg" /> 54411 / 54411eq5.jpg &quot;/&gt; <img alt="equação 6" src="/files/ftp_upload/54411/54411eq6.jpg" /></li></ol></li></ol>

<ol>
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Growth Des. 11, 2702-2706 (2011).</li><li>Custelcean, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Urea-Functionalized+Crystalline+Capsules+for+Recognition+and+Separation+of+Tetrahedral+Oxoanions.">Urea-Functionalized Crystalline Capsules for Recognition and Separation of Tetrahedral Oxoanions.</a> Chem. Commun. 49, 2173-2182 (2013).</li><li>Custelcean, R., Sloop, F. V., Rajbanshi, A., Wan, S., Moyer, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sodium+Sulfate+Separation+from+Aqueous+Alkaline+Solutions+via+Crystalline+Urea-Functionalized+Capsules:+Thermodynamics+and+Kinetics+of+Crystallization.">Sodium Sulfate Separation from Aqueous Alkaline Solutions via Crystalline Urea-Functionalized Capsules: Thermodynamics and Kinetics of Crystallization.</a> Cryst. 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The authors have nothing to disclose.

Esta técnica é bastante tolerante a muitos desvios do procedimento escrito, o que torna bastante robusto. No entanto, existem dois passos críticos que devem ser seguidas. Em primeiro lugar, o ligando BBiG-Cl necessita de ser tão puro quanto possível. As impurezas não só afecta a cristalização e a solubilidade do sal de sulfato resultante, mas também vai fazer com que seja difícil para calcular a quantidade necessária para a remoção do sulfato de quantitativa a partir da solução. Em segundo lugar, todos o...

Separação selectiva de oxoanions hidrofílicos (por exemplo, sulfato, cromato, fosfato) de soluções aquosas competitivos representa um desafio fundamental com relevância para a remediação ambiental, produção de energia, e na saúde humana. 1,2 Sulfato em particular, é difícil extrair da água, devido à sua relutância intrínseca para lançar sua esfera de hidratação e migram para ambientes menos polares. 3 Fazendo extração de sulfato aquosa mais eficiente geralmente requer receptores de complexos que são difíceis e tedioso para sintetizar e purificar, muitas vezes envolvendo reagentes tóxicos e solventes. 4,5 Cristalização selectiva oferece uma alternativa simples, mas eficaz para sulfato de separação de água. 09/06 Embora alguns catiões metálicos, tais como Ba 2+, Pb 2+, ou formar sais de sulfato muito insolúveis Ra 2+, a sua utilização na separação de sulfato de nem sempre é prático devido à sua alta toxicidade e, por vezes, de baixa seletividade. Empregando ligandos orgânicos como precipitantes sulfato tira proveito da diversidade estrutural e receptividade ao desenho característico para moléculas orgânicas. Um ligando orgânico ideal para a cristalização de sulfato aquosa deve ser solúvel em água, ainda formar um sal de sulfato ou complexo insolúvel num tempo relativamente curto e, na presença de concentrações elevadas de iões concorrentes. Além disso, deve ser fácil de sintetizar e de reciclagem. Um destes um ligando, 1,4-benzeno-bis (iminoguanidinium) (BBiG), auto-montadas in situ a partir de dois precursores disponíveis comercialmente, e cloreto de teref aminoguanidinium, foi recentemente encontrada para ser extremamente eficaz na separação de sulfato aquoso. 10 O ligando está na forma de cloreto solúvel em água, e cristaliza selectivamente com sulfato num sal extremamente insolúvel que pode ser facilmente removido da solução por filtração simples. O ligando BBiG pode então ser recuperado por desprotonação com umaNaOH queous e cristalização do neutro bis-iminoguanidine, que pode ser convertido de volta para a forma de cloreto com HCl aquoso, e reutilizado num outro ciclo de separação. A eficácia deste ligando na remoção de sulfato de água é tão grande que o controlo da concentração de sulfato restante em solução já não é uma tarefa trivial, requerendo uma técnica mais avançada que permite uma medição precisa de quantidades vestigiais do anião. Para este efeito, radiomarcado 35S marcador em conjunto com sulfato de contagem de cintilação líquida β foi empregue, uma técnica largamente utilizada para separações de extracção líquido-líquido, e recentemente demonstrou ser eficaz em cristalização de sulfato de monitorização. 8 Este protocolo demonstra a um só recipiente na síntese in situ do ligando e a sua BBiG Cristalização como o sal de sulfato a partir de soluções aquosas. A síntese ex situ do ligando 11 é também apresentada como um convenient método para a produção de grandes quantidades de BBiG-Cl, que podem ser armazenadas na forma cristalina até estar pronto para usar. Remoção de sulfato a partir de água do mar utilizando o ligando BBiG-Cl previamente preparada é então demonstrado. Finalmente, o uso de 35 S-sulfato rotulados e contagem de cintilação líquida β para medir a concentração de sulfato na água do mar é demonstrada. Este protocolo destina-se a fornecer um tutorial para aqueles amplamente interessado em explorar o uso de cristalização seletiva para a separação ânion aquosa.

<table border="0" cellpadding="0" cellspacing="0" width="740">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Terephthalaldehyde</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">T2207</td>
			<td style="width:313px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Aminoguanidinium Chloride</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#396494</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Sulfate</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#239313</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Barium Chloride</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#342920</td>
			<td>Highly Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;"></td>
			<td>Reagent Grade (190 proof)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium Hydroxide</td>
			<td style="width:92px;">EMD</td>
			<td style="width:119px;">SX0590-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hydrochloric Acid</td>
			<td style="width:92px;">Sigma</td>
			<td style="width:119px;">#258148</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Filter Paper</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Any qualitative or analytical filter paper will work</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Syringe Filter (0.22 um)</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Nylon filter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">35S Labeled Sulfate</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;">NEX041005MC</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultima Gold Scintillation Cocktail</td>
			<td style="width:92px;">Perkin Elmer</td>
			<td style="width:119px;">#6013329</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Polypropylene Vials&#160;</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Disposable Syringe (2-3 mL)</td>
			<td style="width:92px;">Any</td>
			<td style="width:119px;">-</td>
			<td>Any disposable plastic syringe works</td>
		</tr>
	</tbody>
</table>

sulfate separation by selective crystallization with a bis-iminoguanidinium ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

O raio-X padrão de difracção de de BBiG-SO 4 (Figura 1) permite a confirmação inequívoca da identidade do sólido cristalizado. Ao comparar o padrão obtido versus a referência um, pico de intensidade importa menos do que o posicionamento de pico. Todos os picos fortes mostrados na referência deve estar presente na amostra obtida. O aparecimento de fortes picos na amostra que estão ausentes no padrão de referência indica a presença de impurezas. </...

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Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

Um protocolo para síntese em solução aquosa in situ de um composto bis (iminoguanidinium) ligando e sua utilização na separação selectiva de sulfato é apresentada.

Separação sulfato por cristalização selectiva com um ligando bis-iminoguanidinium

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

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8.3K visualizações.  Oak Ridge National Laboratory.  Um protocolo para síntese em solução aquosa in situ de um composto bis (iminoguanidinium) ligando e sua utilização na separação selectiva de sulfato é apresentada. 

Vídeo: Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Preparação e Caracterização de SDF-1α-Quitosana As nanopartículas de sulfato de dextrano

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

Química

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.

Síntese de CDs Nanopartículas sem ligando dentro de uma matriz de copolímero de Enxofre

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

Preparation of Biopolymer Aerogels Using Green Solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Preparação de Biopolymer Aerogels utilizando solventes verdes

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Eletroforese Capilar para monitorar Peptide Enxertia em quitosana Films em Tempo real

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that derive from initial 2-bromo-2-butene lithiation followed by acid mediated dienol cyclization. The revised synthesis and purification of the ligand avoids the use of mechanical stirring while still permitting access to significant quantities (39 g) of Cp*H in good yield (58%). The procedure offers other additional benefits, including a more controlled quench of excess lithium during the production of the intermediate heptadienols and a simplified isolation of Cp*H of sufficient purity for metallation with transition metals. The ligand was subsequently used to synthesize [Cp*MCl2]2 complexes of both iridium and ruthenium to demonstrate the utility of the Cp*H prepared and purified by our method. The procedure outlined herein affords substantial quantities of a ubiquitous ancillary ligand support used in organometallic chemistry while minimizing the need for specialized laboratory equipment, thus providing a simpler and more accessible entry point into the chemistry of 1,2,3,4,5-pentamethylcyclopentadiene.

Reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented. The revised protocol for the synthesis and purification of the ligand minimizes the need for specialized laboratory equipment while simplifying reaction workups and product purification. Use of Cp*H in the synthesis of [Cp*MCl2]2 complexes (M = Ru, Ir) is also described.

Acesso a Suportes de Ligantes Valiosos para Metais de Transição: Preparação Modificada em Escala Intermediária de 1

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that ...

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the methodology for non-substituted pyridines in 1957 in a 12 h process, but no X-ray suitable crystals were obtained. The substituted ring used in the methodology presented here clearly influenced the addition of water molecules into the asymmetric unit, which confers a different nucleophilic strength in 1. The X-ray suitable crystal compound 1 was possible due to the stabilization of the negative charge in the oxygen by the presence of two water molecules where the hydrogen atoms donate positive charge into the ring; such water molecules serve well to construct a supramolecular interaction. The hydrated molecules may be possible for the alkaline system that is reached by adjusting the pH to 10. Importantly, the double methyl substituted ring and a reaction time of 5 h, makes it a more versatile method and with wider chemical applications for future ring insertions.

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Herein, we report the synthesis and crystallization of 3,5-lutidine N-oxide dehydrate by a simple protocol that differs from the classical synthesis of pyridine N-oxide. This protocol utilizes different starting material and involves less reaction time to yield a new solvated supramolecular structure, which crystallizes under slow evaporation.

Sínteses, cristalização e caracterização espectroscópica de 3,5-Lutidine N-óxido de desidratar

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used 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.

Síntese de um Bloco de Construção Tiol para a Cristalização de uma Estrutura Semicondutora de Metal-Enxofre com Geometria Giroidal

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

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer by generating a charged structure provides an opportunity to use extraction as a simple purification technique. By combining the use of a miscible organic solvent with saturated sodium bisulfite, aldehydes and reactive ketones can be successfully transformed into charged bisulfite adducts that can then be separated from other organic components of a mixture by the introduction of an immiscible organic layer. Here, we describe a simple protocol for the removal of aldehydes, including sterically-hindered neopentyl aldehydes and some ketones, from chemical mixtures. Ketones can be separated if they are sterically unhindered cyclic or methyl ketones. For aliphatic aldehydes and ketones, dimethylformamide is used as the miscible solvent to improve removal rates. The bisulfite addition reaction can be reversed by basification of the aqueous layer, allowing for the re-isolation of the reactive carbonyl component of a mixture.

Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

Separação de aldeídos e cetonas reativas de misturas usando um protocolo de extração de bissulfito

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry

Proteins are an important class of biological macromolecules that play many key roles in cellular functions including gene expression, catalyzing metabolic reactions, DNA repair and replication. Therefore, a detailed understanding of these processes provides critical information on how cells function. Integrative structural MS methods offer structural and dynamical information on protein complex assembly, complex connectivity, subunit stoichiometry, protein oligomerization and ligand binding. Recent advances in integrative structural MS have allowed for the characterization of challenging biological systems including large DNA binding proteins and membrane proteins. This protocol describes how to integrate diverse MS data such as native MS and ion mobility-mass spectrometry (IM-MS) with molecular dynamics simulations to gain insights into a helicase-nuclease DNA repair protein complex. The resulting approach provides a framework for detailed studies of ligand binding to other protein complexes involved in important biological processes.

Mass spectrometry (MS) has emerged as an important tool for the investigation of structure and dynamics of macromolecular assemblies. Here, we integrate MS-based approaches to interrogate protein complex formation and ligand binding.

Análise de arquiteturas de proteínas e complexos proteína-ligante por espectrometria de massa estrutural Integrativa

Proteins are an important class of biological macromolecules that play many key roles in cellular functions including gene expression, catalyzing ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

Eletroforética cristalização das membranas ultrafinos estrutura Metal-orgânicos de alto desempenho

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...