This work received support through grant HA 6136/1-1 from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) to MH. JAT is supported by Program and Project Grants from the National Health and Medical Research Council of Australia.

NOTA: Los bazos fueron derivadas de ratones (6-10 semanas de edad) y todos los experimentos con animales se realizaron de acuerdo con las directrices de Ética Animal del Centro de Cáncer Peter MacCallum (E486). 1. Preparación de las muestras. <ol><li> Preparación de células de ratón NK activadas. <ol><li> Aislar las células NK ingenuos primarias a partir de suspensiones de una sola célula de bazo de C57BL / 6 o B6.GrzmB - / - (GzmB gen null) ratones por selección negativa utilizando kits disponibles en el mercado. </li><li> Siga el protocolo de los fabricantes. Brevemente, magnéticamente marcar las células NK &quot;no&quot;, tales como las células T y B, células dendríticas, granulocitos, macrófagos, y células rojas de la sangre utilizando anticuerpos conjugados con biotina contra sus marcadores de superficie específicos. Utilice separación magnética con cuentas anti-biotina para agotar las células NK &quot;no&quot;. </li><li> Aislado Cultura células NK durante 5-7 días en medio que contenía IL-2 (1000 U / ml) a 700,000 células / ml en placas de 24 pocillosa 37 &#160; ° C. </li><li> Alternativamente, el uso de células T activadas 19, CTL restringido el antígeno principal de OT1 receptor de células T de ratones transgénicos 20, CTL generados en cultivos mixtos de linfocitos 21, o los sobrenadantes de las células NK activadas para determinar la actividad de secretada GzmB 19. </li></ol></li><li> Mantenimiento de la línea humana de células NK y el aislamiento de células primarias NK. <ol><li> Mantener la leucemia NK humana (células YT) en Roswell Park Memorial Institute (RPMI) suplementado con 10% de suero de ternera fetal. Alternativamente, purificar células NK primarias de la sangre periférica de sujetos sanos y estimular durante 2-3 días en medio que contiene IL-2 a 100 U / ml como se ha descrito previamente 22. </li></ol></li><li> Generación de lisados ​​celulares. <ol><li> Lavar las células tres veces en PBS (pH 7,4), a continuación, suspender en Nonidet P-40 tampón de lisis (0,1% NP-40, NaCl 250 mM, 25 mM Hepes, EDTA 2,5 mM). Idealmente, la lisis de un mínimo de 5 x 10 6 </sarriba&gt; células NK, o 1 x 10 7 células T en 100 l de tampón. No añadir inhibidores de la proteasa, ya que muchos son inhibidores irreversibles de proteasas de serina, y en triptasas particulares como GzmA. Incubar en hielo durante 20 min, y luego sedimentar los núcleos en una microcentrífuga a 15.000 xg durante 10 min. Desechar el pellet nuclear y transferir el sobrenadante a un tubo nuevo. </li></ol></li><li> Determinar la concentración de proteína de los lisados. <ol><li> Use un protocolo disponible comercialmente de elección tales como, Bradford o ácido bicinconínico (BCA) y determinar la concentración de proteínas. Asegúrese de que la concentración es de ~ 2 mg mínimo / ml. Lisados ​​almacenar a -20 ° C hasta que sea necesario (actividad granzima es estable durante muchos meses a -20 ° C). </li></ol></li></ol> 2. granzima B Ensayo de la actividad <ol><li> Preparación de los reactivos <ol><li> Preparar una mM balance de los sustratos (Boc-AAD-S-Bzl o Ac-IEPD-PNA) 10 en DMSO (~ 5 mg / ml) y almacenar en alícuotas a -20 &amp; #176; C. Prepare una dilución de trabajo recién y desechar después de cada día, como Boc-AAD-S-Bzl hidroliza parcialmente en el almacenamiento en DMSO. </li><li> Preparar una población de 250 mM de reactivo colorimétrico (5,5&#39;-ditio-bis (ácido 2-nitrobenzoico), DTNB) en DMSO (0,09 g / ml) y se almacena a -20 ° C. Prepare una dilución de trabajo nueva cada día. Este reactivo sólo se requiere para sustratos con grupos indicadores SBzl, no ANP. </li><li> Invente tampón fresco (0,1 M HEPES, 0,05 M MgCl 2, pH 7,3) cada 2-3 semanas. </li></ol></li><li> Llevar DTNB y sustratos sintéticos a temperatura ambiente. Diluir sustratos (1:16, por ejemplo, 100 l en 1,6 ml de tampón) y DTNB (1: 250, por ejemplo, 10 l en tampón 2,5 ml) y mezclar bien. </li><li> Diluir un mínimo de 100 g de proteína de lisado de cada muestra en un tampón a un volumen final de 160 microlitros. Usando una pipeta multicanal añadir 50 l por pocillo por triplicado (~ 33,3 g / pocillo) en una &#39;&#39; U &#39;&#39; de vinilo del fondo placa de 96 pocillos.Incluir un &quot;búfer de sólo&quot; control (también por triplicado). </li><li> Añadir 100 l de diluirse DTNB para el control de muestras / tampón (omita este paso cuando se trabaja con Ac-IEPD-pNA. NOTA: La escisión de Ac-IEPD-pNA por GzmB libera directamente fluorogénica pNA (Figura 4B). </li><li> Utilizar una pipeta multicanal para añadir rápidamente 50 l de sustratos diluidas a cada conjunto de triplicados, empezando con el tampón entonces cualquier controles negativos y terminando con muestras positivas esperados. </li><li> Colocar la placa en el lector de placas. Medir la actividad Asp-asa por hidrólisis de Boc-Ala-Ala-Asp-S-Bzl / Ac-IEPD-pNA en un lector de microplacas a OD 405 nm. Utilice un protocolo de ensayo cinético, tomar 25 lecturas, cada 15 segundos (aprox 6 min tiempo de lectura total). </li><li> Use las lecturas de absorbancia generadas en cada punto de tiempo para calcular manualmente la tasa de escisión de sustrato de si el software del lector de placas no puede generar un valor de Vmax. </li></ol> 3. Análisis de Data NOTA: Los datos generados se presenta como velocidad máxima, que se define como el cambio de OD en el tiempo (mod / min). <ol><li> Para analizar los datos, determinar la tasa máxima de escisión de sustrato, que se calcula a partir de la tasa de cambio en la absorbancia. Hacer esto automáticamente con el software lector de placas, que normalmente tiene esta opción. </li><li> Alternativamente después de ver las parcelas cinéticos de cambio en la absorbancia, que se generan durante el ensayo cinético en el lector de placas, seleccionar manualmente los puntos de datos que dan a la línea recta más empinada. Para la mayoría de los ensayos se consigue la tasa máxima dentro de la primera 2 min del ensayo. </li><li> Restar la lectura OD inicial a partir de la lectura más alta OD en esta línea recta y se dividen por el intervalo de tiempo. Transferir datos brutos a Microsoft Excel / Gráfico almohadilla para el análisis estadístico y gráfico. </li></ol>

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The authors have nothing to disclose.

Históricamente las granzimas fueron identificados como moléculas efectoras clave de linfocitos citotóxicos (CTL y células NK) capaces de inducir una muerte apoptótica rápida en las células diana. Esto se debió principalmente a la acción de GzmB, que escinde moléculas de sustrato diana a aspartato (D) los residuos y por lo tanto fue capaz de activar la cascada de caspasas por ambas escisión pro-caspasas, así como varios de sus objetivos de abajo. Sin embargo, ahora se aprecia que la expresión GzmB no se limi...

Granzimas son una familia de serina proteasas que se encuentran en los lisosomas secretores de las células (NK) y linfocitos T citotóxicos (CTL) 1 asesino natural. Existen cinco granzimas diferentes en los seres humanos (A, B, H, K y M), y diez en ratones (A - G, K, M y N) 2,3. Granzima A y granzima B (GzmA, GzmB) son las más abundantes y han sido investigadas extensamente en el ambiente humano y de roedor. La función clásica de GzmB es la inducción de apoptosis en las células diana ejecutados en conjunción con la proteína de perforina de formación de poros, que permite la granzima para acceder al citosol de la célula diana 4. Aunque la expresión GzmB se encuentra de manera inequívoca en los linfocitos citotóxicos, estudios recientes se han ocupado de una variedad de otros tipos de células que expresan GzmB, incluyendo pero no limitado a los queratinocitos 5, 6 basófilos, mastocitos, células dendríticas 7 plasmacitoides 8, 9 y las células B, 10.En este contexto, las funciones GzmB no apoptóticas fueron revelados desde la participación en los procesos inflamatorios, la remodelación de tejidos y otras propiedades inmunorreguladoras 11-14. Dado que un papel biológico más amplio se ha propuesto para GzmB lo que se sospechaba previamente, los investigadores necesitan herramientas fiables y específicos para su detección. De la ventaja es requisito específico de GzmB para escindir en el lado carboxilo de residuos de ácido aspártico, una propiedad única entre serina proteasas eucariotas 15. Ratón, humano y de rata GzmB son estructuralmente muy similares, sin embargo, la especificidad de sustrato prolongado de GzmB ratón difiere sutilmente de que tanto de humano y de rata 16, lo que significa que ciertos sustratos genéricos con Asp en la terminal (P1) se pueden escindir eficientemente por GzmB de las tres especies, mientras que otros sustratos con secuencias más complicadas aguas arriba de P1 puede dar resultados muy variables. Tanto en el pasado y li más recienteterature, este hecho ha causado gran confusión y mala interpretación de la importancia biológica de algunos resultados experimentales, aunque cuidadosamente controlado, estudios cinéticos han tratado de corregir la situación 17. En este trabajo hemos tratado de ilustrar estos puntos usando dos sustratos disponibles en el mercado, a saber, Boc-Ala-Ala-Asp-SBzl y N-acetil-Ile-Glu-Pro-Asp-p-nitroanilida. Los dos reactivos hacer generar diferentes grupos reactivos después de la escisión (un sulfhidrilo libre versus un paranitroanilida libre fluorescente), pero esto no tiene efecto alguno sobre la escisión proteolítica. El protocolo descrito es una adaptación moderna de un protocolo muy antiguo 18, pero debería ayudar a los investigadores a utilizar los diferentes sustratos GzmB adecuadamente, mientras que también proporciona un marco metodológico para la detección de la actividad de otros granzimas, como GzmA y GzmH.

<table border="0" cellpadding="0" cellspacing="0" width="1133">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Product</td>
			<td style="width:241px;">Company</td>
			<td style="width:181px;">Catalogue number</td>
			<td style="width:427px;">Comment/description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Boc-Ala-Ala-Asp-S-Bzl</td>
			<td>SM Biochemicals LLC, CA</td>
			<td>SMSB05</td>
			<td>Granzyme B substrate (mouse and human)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ac-IEPD-pNA&#160;</td>
			<td>SM Biochemicals LLC, CA</td>
			<td>SMPNA009</td>
			<td>Granzyme B substrate (only human)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">N-a-CBZ-L-lysine-S-Bzl</td>
			<td>Sigma-Aldrich</td>
			<td>C3647</td>
			<td>Granzyme A substrate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Suc-Phe-Leu-Phe-S-Bzl</td>
			<td>SM Biochemicals LLC, CA</td>
			<td>SB025</td>
			<td>Granzyme H substrate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5,5&#8217;-dithio-bis(2-nitrobenzoic acid)&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>D8130</td>
			<td>&#160;DTNB, Ellman&#8217;s Reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NK cell isolation kit II mouse</td>
			<td>Miltenyi Biotec GmbH</td>
			<td style="width:181px;">130-096-892</td>
			<td style="width:427px;">negative selection kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NK cell isolation kit human</td>
			<td>Miltenyi Biotec GmbH</td>
			<td>130-092-657</td>
			<td style="width:427px;">negative selection kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;"></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plate reader</td>
			<td>Biorad iMark</td>
			<td></td>
			<td>Biorad Microplate Manager Software Version MPM6.3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Serocluster U-bottom vinyl 96-well plate</td>
			<td>Corning, MA, USA</td>
			<td>2797</td>
			<td></td>
		</tr>
	</tbody>
</table>

a colorimetric assay that specifically measures granzyme b proteolytic activity: hydrolysis of boc-ala-ala-asp-s-bzl

The serine protease Granzyme B (GzmB) mediates target cell apoptosis when released by cytotoxic T lymphocytes (CTL) or natural killer (NK) cells. GzmB is the most studied granzyme in humans and mice and therefore, researchers need specific and reliable tools to study its function and role in pathophysiology. This especially necessitates assays that do not recognize proteases such as caspases or other granzymes that are structurally or functionally related. Here, we apply GzmB&#8217;s preference for cleavage after aspartic acid residues in a colorimetric assay using the peptide thioester Boc-Ala-Ala-Asp-S-Bzl. GzmB is the only mammalian serine protease capable of cleaving this substrate. The substrate is cleaved with similar efficiency by human, mouse and rat GzmB, a property not shared by other commercially available peptide substrates, even some that are advertised as being suitable for this purpose. This protocol is demonstrated using unfractionated lysates from activated NK cells or CTL and is also suitable for recombinant proteases generated in a variety of prokaryotic and eukaryotic systems, provided the correct controls are used. This assay is a highly specific method to ascertain the potential pro-apoptotic activity of cytotoxic molecules in mammalian lymphocytes, and of their recombinant counterparts expressed by a variety of methodologies.

El sustrato Boc-AAD-S-Bzl es específico para GzmB El GzmB serina proteasa es un constituyente principal de los linfocitos citotóxicos (CTL y células NK) y es predominantemente responsable de inducir la rápida muerte apoptótica en las células diana, tales como células infectadas por virus o transformadas. Esto es en gran parte debido a su preferencia de sustrato para la escisión después de ciertos residuos de aspartato específicos en las proteínas seleccionadas, un...

Watch this Scientific Journal Video about A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl at JoVE.com

A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl

We describe a simple, quantitative colorimetric assay that specifically measures the proteolytic activity of human, mouse or rat Granzyme B (GzmB). This protocol can be easily adapted for determining protease activity of other granule serine proteases by the hydrolysis of other synthetic peptide substrates with an appropriate recognition sequence.

Un ensayo colorimétrico que mide específicamente granzima B actividad proteolítica: La hidrólisis de Boc-Ala-Ala-Asp-S-Bzl

The serine protease Granzyme B (GzmB) mediates target cell apoptosis when released by cytotoxic T lymphocytes (CTL) or natural killer (NK) cells. GzmB is ...

a-colorimetric-assay-that-specifically-measures-granzyme-b

Research

JoVE Journal

Chemistry

12.9K vistas.  Peter MacCallum Cancer Centre. We describe a simple, quantitative colorimetric assay that specifically measures the proteolytic activity of human, mouse or rat Granzyme B (GzmB). This protocol can be easily adapted for determining protease activity of other granule serine proteases by the hydrolysis of other synthetic peptide substrates with an appropriate recognition sequence.

Video: A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl

Rapid Colorimetric Assays to Qualitatively Distinguish RNA and DNA in Biomolecular Samples

Biochemical experimentation generally requires accurate knowledge, at an early stage, of the nucleic acid, protein, and other biomolecular components in potentially heterogeneous specimens. Nucleic acids can be detected via several established approaches, including analytical methods that are spectrophotometric (e.g., A260), fluorometric (e.g., binding of fluorescent dyes), or colorimetric (nucleoside-specific chromogenic chemical reactions).1 Though it cannot readily distinguish RNA from DNA, the A260/A280 ratio is commonly employed, as it offers a simple and rapid2 assessment of the relative content of nucleic acid, which absorbs predominantly near 260 nm and protein, which absorbs primarily near 280 nm. Ratios &lt; 0.8 are taken as indicative of 'pure' protein specimens, while pure nucleic acid (NA) is characterized by ratios &gt; 1.53.
However, there are scenarios in which the protein/NA content cannot be as clearly or reliably inferred from simple uv-vis spectrophotometric measurements. For instance, (i) samples may contain one or more proteins which are relatively devoid of the aromatic amino acids responsible for absorption at &asymp;280 nm (Trp, Tyr, Phe), as is the case with some small RNA-binding proteins, and (ii) samples can exhibit intermediate A260/A280 ratios (~0.8 &lt; ~1.5), where the protein/NA content is far less clear and may even reflect some high-affinity association between the protein and NA components. For such scenarios, we describe herein a suite of colorimetric assays to rapidly distinguish RNA, DNA, and reducing sugars in a potentially mixed sample of biomolecules. The methods rely on the differential sensitivity of pentoses and other carbohydrates to Benedict's, Bial's (orcinol), and Dische's (diphenylamine) reagents; the streamlined protocols can be completed in a matter of minutes, without any additional steps of having to isolate the components. The assays can be performed in parallel to differentiate between RNA and DNA, as well as indicate the presence of free reducing sugars such as glucose, fructose, and ribose (Figure 1).

A suite of colorimetric assays is described for rapidly distinguishing protein, RNA, DNA, and reducing sugars in potentially heterogeneous biomolecular samples.

Rapid ensayos colorimétricos para distinguir cualitativamente ARN y ADN en muestras Biomolecular

Biochemical experimentation generally requires accurate knowledge, at an early stage, of the nucleic acid, protein, and other biomolecular components in ...

Investigación

Química

Steady-state, Pre-steady-state, and Single-turnover Kinetic Measurement for DNA Glycosylase Activity

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization of OGG1 is undertaken to measure the rates of 8-oxoG excision and product release. When the OGG1 concentration is lower than substrate DNA, time courses of product formation are biphasic; a rapid exponential phase (i.e. burst) of product formation is followed by a linear steady-state phase. The initial burst of product formation corresponds to the concentration of enzyme properly engaged on the substrate, and the burst amplitude depends on the concentration of enzyme. The first-order rate constant of the burst corresponds to the intrinsic rate of 8-oxoG excision and the slower steady-state rate measures the rate of product release (product DNA dissociation rate constant, koff). Here, we describe steady-state, pre-steady-state, and single-turnover approaches to isolate and measure specific steps during OGG1 catalytic cycling. A fluorescent labeled lesion-containing oligonucleotide and purified OGG1 are used to facilitate precise kinetic measurements. Since low enzyme concentrations are used to make steady-state measurements, manual mixing of reagents and quenching of the reaction can be performed to ascertain the steady-state rate (koff). Additionally, extrapolation of the steady-state rate to a point on the ordinate at zero time indicates that a burst of product formation occurred during the first turnover (i.e. y-intercept is positive). The first-order rate constant of the exponential burst phase can be measured using a rapid mixing and quenching technique that examines the amount of product formed at short time intervals (&lt;1 sec) before the steady-state phase and corresponds to the rate of 8-oxoG excision (i.e. chemistry). The chemical step can also be measured using a single-turnover approach where catalytic cycling is prevented by saturating substrate DNA with enzyme (E&gt;S). These approaches can measure elementary rate constants that influence the efficiency of removal of a DNA lesion.

Time courses for the glycosylase activity of 8-oxoguanine DNA glycosylase are biphasic exhibiting a burst of product formation and a linear steady-state phase. Utilizing quench-flow techniques, the burst and the steady-state rates can be measured, which correspond to excision of 8-oxoguanine and release of the glycosylase from the product DNA, respectively.

Medición cinética de estado estable, Pre-estado de equilibrio, y un solo volumen de negocios de ADN glicosilasa Actividad

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization ...

Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein substrates. The histone tails represent one of the most heavily modified stretches within all human proteins. Peptidyl-arginine deiminase 4 (PAD4) has been shown to convert arginine residues into the non-genetically encoded citrulline residue. Few assays described to date have been operationally facile with satisfactory sensitivity. Thus, the lack of adequate assays has likely contributed to the absence of potent non-covalent PAD4 inhibitors. Herein a novel fluorescence-based assay that allows for the monitoring of PAD4 activity is described. A pro-fluorescent substrate analog was designed to link PAD4 enzymatic activity to fluorescence liberation upon the addition of the protease trypsin. It was shown that the assay is compatible with high-throughput screening conditions and has a strong signal-to-noise ratio. Furthermore, the assay can also be performed with crude cell lysates containing over-expressed PAD4.

PAD4 is an enzyme responsible for the conversion of peptidyl-arginine to peptidyl-citrulline. Dysregulation of PAD4 has been implicated in a number of human diseases. A facile and high-throughput compatible fluorescence based PAD4 assay is described.

Monitoreo basado en la fluorescencia de PAD4 actividad a través de un sustrato Analog Pro-fluorescencia

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein ...

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

Dinámica electroquímico Medición de cloruro de iones

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Un método para manipular tensión superficial de un metal líquido a través de la oxidación de la superficie y Reducción

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable low-valent-phosphorus-containing compound acts as a useful P+ transfer agent. Unlike traditional methods employed to access low-coordinate phosphorus species which usually require pyrophoric phosphorus-containing precursors (white phosphorus, Tris(trimethylsilyl)phosphine, etc.), or harsh reducing agents (alkali metals, potassium graphite, etc.), the current approach does not involve pyrophoric or explosive reagents and can be done on large scales (&#62;20 g) in excellent yields by undergraduates with basic air-free synthetic training. The bromide counter ion is readily exchanged with other anions such as tetraphenyl borate (described herein) using typical salt metathesis reagents to obtain materials with desired properties and reactivities. The versatility of this P+ transfer approach is exemplified by the reactions of these triphosphenium precursors with an N-heterocyclic carbene and an anionic bisphosphine, each of which readily displace the neutral bisphosphine to give an NHC-stabilized phosphorus(I) cation and a phosphorus(I) containing zwitterion, respectively.

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

The synthesis of a triphosphenium bromide salt is described and its use as a P+ transfer agent is outlined by reactions with an N-heterocyclic carbene and an anionic bisphosphine, yielding an NHC-stabilized P(I) cation and a P(I) containing zwitterion, respectively.

Preparación y reactividad de un Triphosphenium Bromuro de sal: una fuente conveniente y estable de fósforo (I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable ...

Simultaneous Measurement of HDAC1 and HDAC6 Activity in HeLa Cells Using UHPLC-MS

The search for new histone deacetylase (HDAC) inhibitors is of increasing interest in drug discovery. Isoform selectivity has been in the spotlight since the approval of romidepsin, a class I HDAC inhibitor for cancer therapy, and the clinical investigation of HDAC6-specific inhibitors for multiple myeloma. The present method is used to determine the inhibitory activity of test compounds on HDAC1 and HDAC6 in cells. The isoform activity is measured using the ultra-high-performance liquid chromatography &#8211; mass spectrometry (UHPLC-MS) analysis of specific substrates incubated with treated and untreated HeLa cells. The method has the advantage of reflecting the endogenous HDAC activity within the cell environment, in contrast to cell-free biochemical assays conducted on isolated isoforms. Moreover, because it is based on the quantification of synthetic substrates, the method does not require the antibody recognition of endogenous acetylated proteins. It is easily adaptable to several cell lines and an automated process. The method has already proved useful in finding HDAC6-selective compounds in neuroblasts. Representative results are shown here with the standard HDAC inhibitors trichostatin A (non-specific), MS275 (HDAC1-specific), and tubastatin A (HDAC6-specific) using HeLa cells.

The present method serves to identify isoform-specific inhibitors of histone deacetylases (HDAC) in HeLa cells by the UHPLC-MS analysis of multiple substrates. This is an antibody-free method developed to reflect HDAC1 and HDAC6 activity in the living cell environment, in contrast to single-isoform cell-free assays.

Medición simultánea de HDAC1 y HDAC6 actividad en HeLa células usando UHPLC-MS

The search for new histone deacetylase (HDAC) inhibitors is of increasing interest in drug discovery. Isoform selectivity has been in the spotlight since ...

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

This article describes the microfluidic process and parameters to prepare actuating particles from liquid crystalline elastomers. This process allows the preparation of actuating particles and the variation of their size and shape (from oblate to strongly prolate, core-shell, and Janus morphologies) as well as the magnitude of actuation.

Preparación de microfluídica de elastómero cristalino líquido actuadores

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

Síntesis de ésteres mediante una esterificación Steglich más verde en acetonitrilo

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

NMR spectroscopy is often used for the identification and characterization of enzyme inhibitors in drug discovery, particularly in the context of fragment screening. NMR-based activity assays are ideally suited to work at the higher concentrations of test compounds required to detect these weaker inhibitors. The dynamic range and chemical shift dispersion in an NMR experiment can easily resolve resonances from substrate, product, and test compounds. This contrasts with spectrophotometric assays, in which read-out interference problems often arise from compounds with overlapping UV-vis absorption profiles. In addition, since they lack reporter enzymes, the single-enzyme NMR assays are not prone to coupled-assay false positives. This attribute makes them useful as orthogonal assays, complementing traditional high throughput screening assays and benchtop triage assays. Detailed protocols are provided for initial compound assays at 500 &#956;M and 250 &#956;M, dose-response assays for determining IC50 values, detergent counter screen assays, jump-dilution counter screen assays, and assays in E. coli whole cells. The methods are demonstrated using two nucleoside ribohydrolase enzymes. The use of 1H NMR is shown for the purine-specific enzyme, while 19F NMR is shown for the pyrimidine-specific enzyme. The protocols are generally applicable to any enzyme where substrate and product resonances can be observed and distinguished by NMR spectroscopy. To be the most useful in the context of drug discovery, the final concentration of substrate should be no more than 2-3x its Km value. The choice of NMR experiment depends on the enzyme reaction and substrates available as well as available NMR instrumentation.

NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

NMR-based activity assays have been developed to identify and characterize inhibitors of two nucleoside ribohydrolase enzymes. Protocols are provided for initial compound assays at 500 &#956;M and 250 &#956;M, dose-response assays for determining IC50 values, detergent counter screen assays, jump-dilution counter screen assays, and assays in E. coli whole cells.

Ensayos de actividad basados en RMN para determinar la inhibición compuesta, valores IC50, actividad artifefectiva y actividad de células enteras de ribohidrolasas de nucleósidos

NMR spectroscopy is often used for the identification and characterization of enzyme inhibitors in drug discovery, particularly in the context of fragment ...