The authors thank Prof. Peter Imming and Diana M&#252;ller for synthesis of the Trityl spin probe and Prof. Sebastian Polarz, Martin Wessig and Andreas Schachtschneider for the synthesis of the porous materials. Financial support by the DFG (DR 743/7-1) and within the SPP 1570 is gratefully acknowledged.

<ol>
	<li>Sch&#252;th, F., Sing, K. S. W., Weitkamp, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of Porous Solids. , (2002).</li><li>Hoffmann, F., Cornelius, M., Morell, J., Fr&#246;ba, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silica-Based+Mesoporous+Organic-Inorganic+Hybrid+Materials.">Silica-Based Mesoporous Organic-Inorganic Hybrid Materials.</a> Angew. Chem. Int. Edit. 45 (20), 3216-3251 (2006).</li><li>Sanchez, C., Boissi&#232;re, C., Grosso, D., Laberty, C., Nicole, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design,+Synthesis,+and+Properties+of+Inorganic+and+Hybrid+Thin+Films+Having+Periodically+Organized+Nanoporosity.">Design, Synthesis, and Properties of Inorganic and Hybrid Thin Films Having Periodically Organized Nanoporosity.</a> Chem. of Mat. 20 (3), 682-737 (2008).</li><li>Le Bihan, D., Johansen-Berg, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+MRI+at+25:+Exploring+brain+tissue+structure+and+function.">Diffusion MRI at 25: Exploring brain tissue structure and function.</a> NeuroImage. 61 (2), 324-341 (2012).</li><li>Pregosin, P. S., Kumar, P. G. A., Fern&#225;ndez, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+Gradient+Spin&#8722;Echo+(PGSE)+Diffusion+and+1H,19F+Heteronuclear+Overhauser+Spectroscopy+(HOESY)+NMR+Methods+in+Inorganic+and+Organometallic+Chemistry:+Something+Old+and+Something+New.">Pulsed Gradient Spin&#8722;Echo (PGSE) Diffusion and 1H,19F Heteronuclear Overhauser Spectroscopy (HOESY) NMR Methods in Inorganic and Organometallic Chemistry: Something Old and Something New.</a> Chem. Rev. 105 (8), 2977-2998 (2005).</li><li>Talmon, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+diffusion+in+porous+media+by+PGS+ESR.">Molecular diffusion in porous media by PGS ESR.</a> Phys. Chem. Chem. Phys. 12 (23), 5998-6007 (2010).</li><li>Okazaki, M., Seelan, S., Toriyama, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Condensation+process+of+alcohol+molecules+on+mesoporous+silica+MCM-41+and+SBA-15+and+fumed+silica:+a+spin-probe+ESR+study.">Condensation process of alcohol molecules on mesoporous silica MCM-41 and SBA-15 and fumed silica: a spin-probe ESR study.</a> Appl. Magn. Reson. 35 (3), 363-378 (2009).</li><li>Wessig, M., Spitzbarth, M., Drescher, M., Winter, R., Polarz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+scale+investigation+of+molecular+diffusion+inside+functionalized+porous+hosts+using+a+combination+of+magnetic+resonance+methods.">Multiple scale investigation of molecular diffusion inside functionalized porous hosts using a combination of magnetic resonance methods.</a> Phys. Chem. Chem. Phys. 17 (24), 15976-15988 (2015).</li><li>Yakimchenko, O. E., Degtyarev, E. N., Parmon, V. N., Lebedev, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+in+Porous+Catalyst+Grains+as+Studied+by+EPR+Imaging.">Diffusion in Porous Catalyst Grains as Studied by EPR Imaging.</a> J. Phys. Chem. 99 (7), 2038-2041 (1995).</li><li>Cleary, D. A., Shin, Y. K., Schneider, D. J., Freed, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+determination+of+translational+diffusion+coefficients+using+ESR+imaging.">Rapid determination of translational diffusion coefficients using ESR imaging.</a> J. Magn. Reson. 79 (3), 474-492 (1988).</li><li>Hornak, J. P., Moscicki, J. K., Schneider, D. J., Freed, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+coefficients+in+anisotropic+fluids+by+ESR+imaging+of+concentration+profiles.">Diffusion coefficients in anisotropic fluids by ESR imaging of concentration profiles.</a> J. Chem. Phys. 84 (6), 3387-3395 (1986).</li><li>Berliner, L. J., Fujii, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EPR+imaging+of+diffusional+processes+in+biologically+relevant+polymers.">EPR imaging of diffusional processes in biologically relevant polymers.</a> J. Magn. Reson. 69 (1), 68-72 (1986).</li><li>Degtyarev, Y. N., Schlick, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+Coefficients+of+Small+Molecules+as+Guests+in+Various+Phases+of+Pluronic+L64+Measured+by+One-Dimensional+Electron+Spin+Resonance+Imaging.">Diffusion Coefficients of Small Molecules as Guests in Various Phases of Pluronic L64 Measured by One-Dimensional Electron Spin Resonance Imaging.</a> Langmuir. 15 (15), 5040-5047 (1999).</li><li>Marek, A., Labsk&#253;, J., Ko&#328;&#225;k, &. #. 2. 6. 8. ;., Pila&#345;, J., Schlick, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+Diffusion+of+Paramagnetic+Tracers+in+HEMA+Gels+and+in+Concentrated+Solutions+of+PolyHEMA+by+1D+Electron+Spin+Resonance+Imaging.">Translational Diffusion of Paramagnetic Tracers in HEMA Gels and in Concentrated Solutions of PolyHEMA by 1D Electron Spin Resonance Imaging.</a> Macromolecules. 35 (14), 5517-5528 (2002).</li><li>Shin, Y. K., Ewert, U., Budil, D. E., Freed, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscopic+versus+macroscopic+diffusion+in+model+membranes+by+electron+spin+resonance+spectral-spatial+imaging.">Microscopic versus macroscopic diffusion in model membranes by electron spin resonance spectral-spatial imaging.</a> Biophys. J. 59 (4), 950-957 (1991).</li><li>Spitzbarth, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+Monitoring+of+Macroscopic+and+Microscopic+Diffusion+of+Guest+Molecules+in+Silica+and+Organosilica+Aerogels+by+Spatially+and+Time-Resolved+Electron+Paramagnetic+Resonance+Spectroscopy.">Simultaneous Monitoring of Macroscopic and Microscopic Diffusion of Guest Molecules in Silica and Organosilica Aerogels by Spatially and Time-Resolved Electron Paramagnetic Resonance Spectroscopy.</a> J. Phys. Chem. C. 119 (30), 17474-17479 (2015).</li><li>Kruczala, K., Schlick, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+Diffusion+Coefficients+of+Nitroxide+Radicals+in+Heterophasic+Propylene&#8722;Ethylene+Copolymers+by+Electron+Spin+Resonance+Imaging.">Measuring Diffusion Coefficients of Nitroxide Radicals in Heterophasic Propylene&#8722;Ethylene Copolymers by Electron Spin Resonance Imaging.</a> Macromolecules. 44 (2), 325-333 (2011).</li><li>Wessig, M., Drescher, M., Polarz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+Functional+Group+Specific+Surface+Interactions+in+Porous+Solids+Using+ESR+Spectroscopy+as+a+Sensitive+and+Quantitative+Tool.">Probing Functional Group Specific Surface Interactions in Porous Solids Using ESR Spectroscopy as a Sensitive and Quantitative Tool.</a> The J. Phys. Chem. C. 117 (6), 2805-2816 (2013).</li><li>Kuschel, A., Polarz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organosilica+Materials+with+Bridging+Phenyl+Derivatives+Incorporated+into+the+Surfaces+of+Mesoporous+Solids.">Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids.</a> Adv. Funct. Mater. 18 (8), 1272-1280 (2008).</li><li>Spitzbarth, M., Drescher, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+iterative+reconstruction+technique+software+for+spectral-spatial+EPR+imaging.">Simultaneous iterative reconstruction technique software for spectral-spatial EPR imaging.</a> J. Magn. Reson. 257, 79-88 (2015).</li><li>Stoll, S., Schweiger, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EasySpin,+a+comprehensive+software+package+for+spectral+simulation+and+analysis+in+EPR.">EasySpin, a comprehensive software package for spectral simulation and analysis in EPR.</a> J. Magn. Reson. 178 (1), 42-55 (2006).</li></ol>

Los autores no tienen nada que revelar.

El protocolo permite la monitorización de la difusión de moléculas huésped paramagnéticas. Un enfoque de formación de imágenes 1D ha sido elegido debido a que permite una resolución de tiempo mayor en comparación con las imágenes 2D o 3D. El enfoque 1d requiere un área de sección transversal constante de la muestra debido a que la intensidad de la imagen 1d obtenido depende no sólo de la concentración sino también en el área de la sección transversal de la muestra. El método requiere también que los e...

Los materiales porosos desempeñan un papel importante en aplicaciones prácticas, tales como la catálisis y la cromatografía 1. Mediante la adición de grupos de superficie y el ajuste de las propiedades de tamaño de poro y de la superficie, los materiales se pueden adaptar a la aplicación deseada 2,3. La funcionalidad del material poroso depende fundamentalmente de las propiedades de difusión de las moléculas huésped en el interior de los poros. En los materiales porosos, una distinción debe hacerse entre lo microscópico de traslación constante de difusión D micro, que describe la difusión en una escala de longitud molecular por un lado y lo macroscópico de traslación constante de difusión D macro por otra parte, que está influenciada por la difusión a través de múltiples poros, límites de grano, tortuosidad y falta de homogeneidad del material. Hay varios métodos de resonancia magnética disponible para estudiar la difusión, cada uno adecuado para una parteicular escala de longitud. En la escala de milímetros, de resonancia magnética nuclear (RMN) de formación de imágenes de resonancia 4 y paramagnética electrónica (EPR) de formación de imágenes (tal como se presenta en este protocolo) se puede utilizar. Escalas más pequeñas se hacen accesibles mediante el uso de gradientes de campo pulsado en RMN, así como experimentos de EPR 5,6. En la escala de nanómetros, espectroscopia EPR puede ser utilizado por la observación de cambios de la interacción de intercambio Heisenberg entre las sondas de espín 7,8. Los estudios de difusión traslacional utilizando la gama de imágenes EPR de catalizador industrial apoye, por ejemplo, óxido de aluminio 9, a anisotrópico fluidos 10,11, sistemas de liberación de fármacos hechos de geles de polímero de 12 - 14 y 15 membranas modelo. Este protocolo presenta un enfoque in situ utilizando imágenes de EPR para controlar la difusión de traslación macroscópica de sondas de espín en cilíndrico, medios porosos. Se demuestra por un sistema hospedador-huésped que consiste en THsonda de correo nitróxido giro 3- (2-yodoacetamido) 2,2,5,5-tetrametil-1-pirrolidiniloxi (IPSL) como invitado en el interior del organosilica mesoporosa periódica (PMO) aerogel UKON1-GEL como anfitrión y etanol como solvente. Este protocolo con éxito ha sido utilizado anteriormente 16 para comparar D macro tal como se determina con imágenes EPR con D micro para el material de relleno UKON1-gel y gel de sílice y IPSL especies de huéspedes y Tris (8-carboxi-2,2,6,6-tetrametil-perdeutero-benzo [1,2-d : 4,5-d &#39;] bis (1,3) ditiol) metilo (tritilo), véase la Figura 1. En otros métodos basados ​​en imágenes de onda continua (CW) 17 EPR, la difusión se lleva a cabo fuera del espectrómetro. En contraste, el método presentado aquí utiliza un enfoque in situ. Una serie de instantáneas de la distribución de la densidad ρ 1d 1d giro (t, γ) esregistrada durante un período de varias horas. Durante este tiempo, una instantánea se toma después de la otra y entrega un patrón de difusión en tiempo real con una resolución de tiempo de aproximadamente 5 min. UKON1-GEL y de gel de sílice se han sintetizado en tubos de muestra con un diámetro interior de 3 mm como se describe en la literatura. 16,18,19 El UKON1-GEL y la síntesis de gel de sílice conduce a una reducción de la muestra. Las muestras se colocan dentro de un tubo termo-retráctil para evitar que las moléculas huésped se mueva entre el aerogel y la pared del tubo de muestra. Este paso adicional no es necesario para las muestras que se pueden sintetizar directamente en el tubo de la muestra sin cambiar su tamaño. El colapso muestras de aerogel cuando se secan, por lo que deben ser sumergidos en un disolvente en todo momento. La temperatura que se necesita para el tubo de contracción de calor es mayor que el punto de ebullición del etanol a presión ambiente. Por lo tanto el protocolo describe el uso de una olla a presión para elevar lapunto de ebullición del etanol. El protocolo abarca la preparación de la muestra de UKON1-GEL sintetizado de antemano para el experimento de formación de imágenes EPR y los ajustes del espectrómetro que se utilizan para controlar la difusión de sonda de giro IPSL. Para el análisis de datos, se proporciona software escrito localmente y su uso se describe. Los datos en bruto desde el espectrómetro se pueden cargar directamente. El software calcula el espacial 1d 1d ρ distribución de la densidad de giro (t, γ) y tiene en cuenta el perfil de sensibilidad resonador. El usuario puede seleccionar una región del aerogel y una ventana de tiempo, durante el cual la constante de difusión ha de ser determinado. Entonces, el programa determina las condiciones de contorno de la ecuación de difusión en base a que la selección y resuelve la ecuación de difusión. Es compatible con por lo menos para formar cuadrados para encontrar el valor de la macro D, donde la solución numérica mejor se ajuste a los datos experimentales. <p clculo = &quot;jove_content&quot;&gt; El protocolo se puede utilizar con ajustes para diferentes huéspedes y de acogida materiales siempre y cuando el área de la sección transversal de la muestra no cambia en toda la muestra, es decir 1d ρ (t, γ) da acceso directo a la concentración y no se ve influenciada por un cambio en la sección transversal de la muestra. El rango de valores accesibles para D macro se estima que el 16 entre 10 -12 m 2 / seg y 7 · 10 -9 m 2 / seg.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>X-Band spectrometer</td>
			<td>Bruker</td>
			<td>E580</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrometer software</td>
			<td>Bruker</td>
			<td>Xepr 2.6b.108</td>
			<td></td>
		</tr>
		<tr>
			<td>gradient coil system</td>
			<td>Bruker</td>
			<td>E540 GCX2</td>
			<td></td>
		</tr>
		<tr>
			<td>imaging resonator</td>
			<td>Bruker</td>
			<td>TMHS 1007</td>
			<td></td>
		</tr>
		<tr>
			<td>micro-classic pipette controller</td>
			<td>Brand</td>
			<td>25900</td>
			<td></td>
		</tr>
		<tr>
			<td>microcapillary ringcaps 50 &#181;l</td>
			<td>Hirschmann</td>
			<td>9600150</td>
			<td>inner diameter 0.5 mm</td>
		</tr>
		<tr>
			<td>EPR sample tube 2 mm inner diameter</td>
			<td>Bruker</td>
			<td>ER 221TUB/2</td>
			<td></td>
		</tr>
		<tr>
			<td>EPR sample tube 4 mm inner diameter</td>
			<td>Bruker</td>
			<td>ER 221TUB/4</td>
			<td></td>
		</tr>
		<tr>
			<td>heat-shrink tubing DERAY-IB</td>
			<td>DSG-Canusa</td>
			<td>2210048952</td>
			<td>4.8 mm/2.4 mm, 2:1, 95 &#176;C - 200 &#176;C</td>
		</tr>
		<tr>
			<td>heat gun</td>
			<td>Bosch</td>
			<td>PHG 600-3</td>
			<td></td>
		</tr>
		<tr>
			<td>PTFE&#160; band</td>
			<td>VWR</td>
			<td>332362S</td>
			<td>width 12 mm</td>
		</tr>
		<tr>
			<td>test tube</td>
			<td></td>
			<td></td>
			<td>length 16 cm, diameter 1.5 cm</td>
		</tr>
		<tr>
			<td>beaker</td>
			<td></td>
			<td></td>
			<td>250 ml, height 9 cm, diameter 7 cm</td>
		</tr>
		<tr>
			<td>capillary tube sealing</td>
			<td>Fisher Scientific</td>
			<td>02-678</td>
			<td></td>
		</tr>
		<tr>
			<td>pressure cooker, 3l with trivet</td>
			<td>Beem</td>
			<td>Vital-X-Press V2, F1000675</td>
			<td></td>
		</tr>
		<tr>
			<td>magnetic stirrer with heating element</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ethanol (p.a.)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ethanol (techn.)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>syringe</td>
			<td>Hamilton</td>
			<td>1705</td>
			<td>0.05 ml, custom length: 20 cm,</td>
		</tr>
		<tr>
			<td>Pasteur capillary pipette</td>
			<td></td>
			<td></td>
			<td>length 23 cm</td>
		</tr>
		<tr>
			<td>data analysis software</td>
			<td>homemade</td>
			<td></td>
			<td>Available for download at http://www.uni-konstanz.de/drescher/software. Requires Matlab.</td>
		</tr>
		<tr>
			<td>UKON1-GEL</td>
			<td>kindly provided by Prof. Sebastian Polarz, Martin Wessig and Andreas Schachtschneider&#160;</td>
			<td></td>
			<td>See references 16, 18, 19 for the synthesis</td>
		</tr>
	</tbody>
</table>

in situ monitoring of diffusion of guest molecules in porous media using electron paramagnetic resonance imaging

A method is demonstrated to monitor macroscopic translational diffusion using electron paramagnetic resonance (EPR) imaging. A host-guest system with nitroxide spin probe 3-(2-Iodoacetamido)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (IPSL) as a guest inside the periodic mesoporous organosilica (PMO) aerogel UKON1-GEL as a host and ethanol as a solvent is used as an example to describe the protocol. Data is shown from a previous publication, where the protocol has been applied to both IPSL and Tris(8-carboxy-2,2,6,6-perdeutero-tetramethyl-benzo[1,2-d:4,5-d&#8242;]bis(1,3)dithiole) methyl (Trityl) as guest molecules and UKON1-GEL and SILICA-GEL as host systems. 
A method is shown to prepare aerogel samples that cannot be synthesized directly in the sample tube for measurement due to a size change during synthesis. The aerogel is attached to sample tubes using heat shrink tubing and a pressure cooker to reach the necessary temperature without evaporating the solvent in the process. The method does not assume a clearly defined initial distribution of guest molecules at the start of the measurement. Instead, it requires a reservoir on top of the aerogel and experimentally determines the influx rate during data analysis.
The diffusion is monitored continually over a period of 20 hr by recording the 1d spin density profile within the sample. The spectrometer settings for the imaging experiment are described quantitatively. Data analysis software is provided to take the resonator sensitivity profile into account and to numerically solve the diffusion equation. The software determines the macroscopic translational diffusion coefficient by least square minimization of the difference between the experiment and the numerical solution of the diffusion equation.

Una foto y esquemática de un aerogel dentro del tubo de contracción se muestran en las Figuras 2a y 2b. La imagen de EPR 2d en la figura 2c muestra claramente el borde superior del aerogel. La intensidad de 1d ρ dentro del tubo de muestra por encima de la aerogel es menor aunque la concentración de la sonda de giro es al menos tan alta como en el aerogel. Sin embargo, la profundidad de la muestra perpendicular al ...

Watch this Scientific Journal Video about In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging at JoVE.com

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

A protocol for the in situ monitoring of the diffusion of guest molecules in porous media using electron paramagnetic resonance (EPR) imaging is presented.

Monitoreo in situ de la difusión de las moléculas huéspedes en medios porosos Usando Resonancia paramagnética de electrones

A method is demonstrated to monitor macroscopic translational diffusion using electron paramagnetic resonance (EPR) imaging. A host-guest system with ...

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Research

JoVE Journal

Chemistry

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

6.3K vistas.  Universität Konstanz. A protocol for the in situ monitoring of the diffusion of guest molecules in porous media using electron paramagnetic resonance (EPR) imaging is presented.

Video: In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date back to the early 1980s the focus of these early papers primarily characterized the changes to the structures under extremely harsh conditions (pH or temperature)1-3. It is also known that paramagnetic molecular oxygen undergoes a Heisenberg spin exchange interaction with stable radicals that extremely broadens the EPR signal4-6. Recently, we reported interesting results where this interaction of molecular oxygen with a certain part of the existing stable radical structure can be reversibly affected simply by flowing a diamagnetic gas through the carbon samples at STP7. As flows of He, CO2, and N2 had a similar effect these interactions occur at the surface area of the macropore system.
This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

Explorando la naturaleza radical de una superficie de carbono por resonancia paramagnética de electrones y un flujo de gas de calibrado

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date ...

Investigación

Química

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical (Methylation) and Physical (Mass Spectrometry, Nuclear Magnetic Resonance) Techniques

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans. De-starched wheat endosperm cell walls were isolated as an alcohol-insoluble residue (AIR)1 and sequentially extracted with water (W-sol Fr) and 1 M KOH containing 1% NaBH4 (KOH-sol Fr) as described by Ratnayake et al. (2014)2. Two different approaches (see summary in Figure 1) are adopted. In the first, intact W-sol AXs are treated with 2AB to tag the original RE backbone chain sugar residue and then treated with an endoxylanase to generate a mixture of 2AB-labelled RE and internal region reducing oligosaccharides, respectively. In a second approach, the KOH-sol Fr is hydrolyzed with endoxylanase to first generate a mixture of oligosaccharides which are subsequently labelled with 2AB. The enzymically released ((un)tagged) oligosaccharides from both W- and KOH-sol Frs are then methylated and the detailed structural analysis of both the native and methylated oligosaccharides is performed using a combination of MALDI-TOF-MS, RP-HPLC-ESI-QTOF-MS and ESI-MSn. Endoxylanase digested KOH-sol AXs are also characterized by nuclear magnetic resonance (NMR) that also provides information on the anomeric configuration. These techniques can be applied to other classes of polysaccharides using the appropriate endo-hydrolases.

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical Methylation and Physical Mass Spectrometry, Nuclear Magnetic Resonance Techniques

This protocol describes the specific techniques used for the structural characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans by tagging the RE with 2 aminobenzamide prior to enzymatic (endoxylanase) hydrolysis and then analysis of the resultant oligosaccharides using mass spectrometry (MS) and nuclear magnetic resonance (NMR).

La secuenciación de pared planta heteroxilanos Usando enzimática, química (metilación) y (espectrometría de masas, resonancia magnética nuclear) Técnicas Físicas

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of ...

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance imaging (MRI). Their purpose is to enhance the relaxation rate of water protons in tissue, thus increasing the MR image contrast and the specificity of the MRI measurements. Current clinically approved contrast agents are low molecular weight molecules that are rapidly cleared from the body. The use of dendrimers as carriers of paramagnetic chelators can play an important role in the future development of more efficient MRI contrast agents. Specifically, the increase in local concentration of the paramagnetic species results in a higher signal contrast. Furthermore, this CA provides a longer tissue retention time due to its high molecular weight and size. Here, we demonstrate a convenient procedure for the preparation of macromolecular MRI contrast agents based on poly(amidoamine) (PAMAM) dendrimers with monomacrocyclic DOTA-type chelators (DOTA &#8211; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate). The chelating unit was appended by exploiting the reactivity of the isothiocyanate (NCS) group towards the amine surface groups of the PAMAM dendrimer to form thiourea bridges. Dendrimeric products were purified and analyzed by means of nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. Finally, high resolution MR images were recorded and the signal contrasts obtained from the prepared dendrimeric and the commercially available monomeric agents were compared.

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

This protocol describes the preparation and characterization of a dendrimeric magnetic resonance imaging (MRI) contrast agent that carries cyclen-based macrocyclic chelates coordinating paramagnetic gadolinium ions. In a series of MRI experiments in vitro, this agent produced an amplified MRI signal when compared to the commercially available monomeric analogue.

Preparación y<em&gt; In Vitro</em&gt; Caracterización de los agentes de contraste basados ​​en dendrímeros de Imágenes por Resonancia Magnética

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance ...

In Situ Characterization of Boehmite Particles in Water Using Liquid SEM

In situ imaging and elemental analysis of boehmite (AlOOH) particles in water is realized using the System for Analysis at the Liquid Vacuum Interface (SALVI) and Scanning Electron Microscopy (SEM). This paper describes the method and key steps in integrating the vacuum compatible SAVLI to SEM and obtaining secondary electron (SE) images of particles in liquid in high vacuum. Energy dispersive x-ray spectroscopy (EDX) is used to obtain elemental analysis of particles in liquid and control samples including deionized (DI) water only and an empty channel as well. Synthesized boehmite (AlOOH) particles suspended in liquid are used as a model in the liquid SEM illustration. The results demonstrate that the particles can be imaged in the SE mode with good resolution (i.e., 400 nm). The AlOOH EDX spectrum shows significant signal from the aluminum (Al) when compared with the DI water and the empty channel control. In situ liquid SEM is a powerful technique to study particles in liquid with many exciting applications. This procedure aims to provide technical know-how in order to conduct liquid SEM imaging and EDX analysis using SALVI and to reduce potential pitfalls when using this approach.

In Situ Characterization of Boehmite Particles in Water Using Liquid SEM

We present a procedure for real-time imaging and elemental composition analysis of boehmite particles in deionized water by in situ liquid Scanning Electron Microscopy.

In Situ Caracterización de partículas de bohemita SEM líquido con agua

In situ imaging and elemental analysis of boehmite (AlOOH) particles in water is realized using the System for Analysis at the Liquid Vacuum Interface ...

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The devices are patterned from epoxy glue using soft lithography and are suitable for in situ X-ray diffraction experiments at room temperature. The sample wells are lidded on both sides with polymeric polyimide foil windows that allow diffraction data collection with low X-ray background. This fabrication method is undemanding and inexpensive. After the sourcing of a SU-8 master wafer, all fabrication can be completed outside of a cleanroom in a typical research lab environment. The chip design and fabrication protocol utilize capillary valving to microfluidically split an aqueous reaction into defined nanoliter sized droplets. This loading mechanism avoids the sample loss from channel dead-volume and can easily be performed manually without using pumps or other equipment for fluid actuation. We describe how isolated nanoliter sized drops of protein solution can be monitored in situ by dynamic light scattering to control protein crystal nucleation and growth. After suitable crystals are grown, complete X-ray diffraction datasets can be collected using goniometer based in situ fixed target serial X-ray crystallography at room temperature. The protocol provides custom scripts to process diffraction datasets using a suite of software tools to solve and refine the protein crystal structure. This approach avoids the artefacts possibly induced during cryo-preservation or manual crystal handling in conventional crystallography experiments. We present and compare three protein structures that were solved using small crystals with dimensions of approximately 10-20 &#181;m grown in chip. By crystallizing and diffracting in situ, handling and hence mechanical disturbances of fragile crystals is minimized. The protocol details how to fabricate a custom X-ray transparent microfluidic chip suitable for in situ serial crystallography. As almost every crystal can be used for diffraction data collection, these microfluidic chips are a very efficient crystal delivery method.

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes in detail how to fabricate and operate microfluidic devices for X-ray diffraction data collection at room temperature. Additionally, it describes how to monitor protein crystallization by dynamic light scattering and how to process and analyze obtained diffraction data.

Chips de microfluídica para dispersión ligera dinámica In Situ mediante difracción de rayos x de cristal y In Situ para la cristalografía Serial

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The ...

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in liquid environments. This manuscript describes the process for making graphene liquid cells through the example of graphene liquid cell transmission electron microscopy (TEM) experiments of gold nanocrystal etching. The protocol for making graphene liquid cells involves coating gold, holey-carbon TEM grids with chemical vapor deposition graphene and then using those graphene-coated grids to encapsulate liquid between two graphene surfaces. These pockets of liquid, with the nanomaterial of interest, are imaged in the electron microscope to see the dynamics of the nanoscale process, in this case the oxidative etching of gold nanorods. By controlling the electron beam dose rate, which modulates the etching species in the liquid cell, the underlying mechanisms of how atoms are removed from nanocrystals to form different facets and shapes can be better understood. Graphene liquid cell TEM has the advantages of high spatial resolution, compatibility with traditional TEM holders, and low start-up costs for research groups. Current limitations include delicate sample preparation, lack of flow capability, and reliance on electron beam-generated radiolysis products to induce reactions. With further development and control, graphene liquid cell may become a ubiquitous technique in nanomaterials and biology, and is already being used to study mechanisms governing growth, etching, and self-assembly processes of nanomaterials in liquid on the single particle level.

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching

Graphene liquid cell electron microscopy can be used to observe nanocrystal dynamics in a liquid environment with greater spatial resolution than other liquid cell electron microscopy techniques. Etching premade nanocrystals and following their shape using graphene liquid cell Transmission Electron Microscopy can yield important mechanistic information about nanoparticle transformations.

Usando el líquido celular microscopia electrónica de transmisión para estudiar in Situ el aguafuerte de Nanocrystal

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in ...

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F&#8722;

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F&#8722;), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.

Here, we present a protocol for photoelectron imaging of anionic species. Anions generated in vacuo and separated by mass spectrometry are probed using velocity mapped photoelectron imaging, providing details of anion and neutral energy levels, anion and neutral structure and the nature of the anion electronic state.

La proyección de imagen del fotoelectrón de aniones ilustrado por 310 Nm la separación de F−

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound ...

Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction

A highly efficient transition metal catalyst removal method is developed. The water-soluble catalyst contains a newly-designed NHC ligand for the catalyst removal via host-guest interactions. The new NHC ligand possesses an adamantyl (guest) tethered linear ethylene glycol units for hydrophobic inclusion into the cavity of a &#946;-cyclodextrin (&#946;-CD) host compound. The new NHC ligand was applied to a Ru-based olefin metathesis catalyst. The Ru catalyst demonstrated excellent activity in representative ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions in aqueous media as well as organic solvent, CH2Cl2. After the reaction was complete, the lingering Ru residue was removed from the aqueous solution with the efficiency of more than 99% (53 ppm of Ru residue) by simple filtration utilizing a host-guest interaction between insoluble silica-grafted &#946;-CD (host) and the adamantyl moiety (guest) on the catalyst. The new Ru catalyst also demonstrated high removal efficiency via extraction when the reaction is run in organic solvent by partitioning the crude reaction mixture between layers of diethyl ether and water. In this way, the catalyst stays in aqueous layer only. In organic layer, the residual Ru amount was only 0.14 ppm in the RCM reactions of diallyl compounds.

A removable water-soluble N-heterocyclic carbene (NHC) ligand in aqueous media via host-guest interaction has been developed. We demonstrated representative olefin metathesis reactions in water as well as in dichloromethane. Via either host-guest interaction or extraction, the residual ruthenium (Ru) catalyst was as low as 0.14 ppm after the reaction.

Extracción heterogénea del catalizador de metátesis de olefinas rutenio solubles en agua de medios acuosos mediante interacción Host-Guest

A highly efficient transition metal catalyst removal method is developed. The water-soluble catalyst contains a newly-designed NHC ligand for the catalyst ...

Pretargeted Radioimmunotherapy Based on the Inverse Electron Demand Diels-Alder Reaction

While radioimmunotherapy (RIT) is a promising approach for the treatment of cancer, the long pharmacokinetic half-life of radiolabeled antibodies can result in high radiation doses to healthy tissues. Perhaps not surprisingly, several different strategies have been developed to circumvent this troubling limitation. One of the most promising of these approaches is pretargeted radioimmunotherapy (PRIT). PRIT is predicated on decoupling the radionuclide from the immunoglobulin, injecting them separately, and then allowing them to combine in vivo at the target tissue. This approach harnesses the exceptional tumor-targeting properties of antibodies while skirting their pharmacokinetic drawbacks, thereby lowering radiation doses to non-target tissues and facilitating the use of radionuclides with half-lives that are considered too short for use in traditional radioimmunoconjugates. Over the last five years, our laboratory and others have developed an approach to in vivo pretargeting based on the inverse electron-demand Diels-Alder (IEDDA) reaction between trans-cyclooctene (TCO) and tetrazine (Tz). This strategy has been successfully applied to pretargeted positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging with a variety of antibody-antigen systems. In a pair of recent publications, we have demonstrated the efficacy of IEDDA-based PRIT in murine models of pancreatic ductal adenocarcinoma and colorectal carcinoma. In this protocol, we describe protocols for PRIT using a 177Lu-DOTA-labeled tetrazine radioligand ([177Lu]Lu-DOTA-PEG7-Tz) and a TCO-modified variant of the colorectal cancer targeting huA33 antibody (huA33-TCO). More specifically, we will describe the construction of huA33-TCO, the synthesis and radiolabeling of [177Lu]Lu-DOTA-PEG7-Tz, and the performance of in vivo biodistribution and longitudinal therapy studies in murine models of colorectal carcinoma.

This protocol describes the synthesis and characterization of a trans-cyclooctene (TCO)-modified antibody and a 177Lu-labeled tetrazine (Tz) radioligand for pretargeted radioimmunotherapy (PRIT). In addition, it details the use of these two constructs for in vivo biodistribution and longitudinal therapy studies in a murine model of colorectal cancer.

Radioinmunoterapia pretargeted basada en la reacción de Diels-Alder de demanda electrónica inversa

While radioimmunotherapy (RIT) is a promising approach for the treatment of cancer, the long pharmacokinetic half-life of radiolabeled antibodies can ...

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. The versatility of the GSMLCs is demonstrated in the context of a study about etching and growth dynamics of gold nanostructures from a HAuCl4 precursor solution. GSMLCs combine the advantages of conventional silicon- and graphene-based liquid cells by offering reproducible well depths together with facile cell manufacturing and handling of the specimen under investigation. The GSMLCs are fabricated on a single silicon substrate which drastically reduces the complexity of the manufacturing process compared to two-wafer-based liquid cell designs. Here, no bonding or alignment process steps are required. Furthermore, the enclosed liquid volume can be tailored to the respective experimental requirements by simply adjusting the thickness of a silicon nitride layer. This enables a significant reduction of window bulging in the electron microscope vacuum. Finally, a state-of-the-art quantitative evaluation of single particle tracking and dendrite formation in liquid cell experiments using only open source software is presented.

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

A protocol for preparation of graphene-supported microwell liquid cells for in situ electron microscopy of gold nanocrystals from HAuCl4 precursor solution is presented. Furthermore, an analysis routine is presented to quantify observed etching and growth dynamics.

Preparación de células líquidas de micropozo compatibles con grafeno para microscopía electrónica de transmisión in situ

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. ...