Il presente lavoro è stato supportato da Vicerrectoría de Investigación y Estudios de Posgrado da BUAP, divulgazione della scienza e progetti n. REOY-NAT14, 15, 16-G. EMEL-NAT17. RMG grazie CONACyT (Messico) per la borsa di studio 417887.

1. reazione
<ol><li>Mettere in una cappa un pallone rotondo aperto 100 mL con 0,5 mol (29,8 mL) di acido acetico glaciale e aggiungere 0,051 mol (5,82 mL) di 3,5-dimethylpyridine e 5 mL di H2O2 (35%). Mantenere la reazione di miscela sotto costante agitazione magnetica, ad una temperatura interna di 80 ° C per 5 h.</li>
	<li>Dopo il tempo di reazione, raffreddare il pallone a 24 ° C con ghiaccio (do non esporre l'acido acetico di gas per il ghiaccio) e collegarlo a un'unità di distillazione sotto vuoto ad alta per 90-120 min per rimuovere l'eccesso di acido acetico. Attenzione: Non utilizzare materiale caldo. Attendere fino a quando il vetro raggiunge una temperatura gestibile. Questo eviterà anche vapori entrando parte superiore dell'unità di distillazione.</li>
	<li>Aggiungere acqua distillata acqua (10 mL) due volte a garantire la rimozione di qualsiasi traccia di acido acetico e di concentrare la miscela molto possibile.</li>
</ol>2. estrazione e regolazione basicità
<ol><li>Sciogliere in acqua bi-distillata prodotto viscoso e trasparente isolato e utilizzare un potenziometro per regolare il pH a 10 con puro solido Na2CO3.</li>
	<li>Posizionare con cura la soluzione in un imbuto separatore mL 250 ed estrarlo 5 volte con 250 mL di CHCl3 per migliorare il rendimento. Recuperare lo strato organico e asciugarlo sopra tinta Na2così4 per 30 min massimo, che conterrà il prodotto. Se necessario, estrarre nuovamente la fase acquosa con la quantità desiderata di CHCl3. Attenzione: CHCl3 può provocare sonnolenza e vertigini; maneggiare con cura e all'interno di una cappa aspirante.</li>
	<li>Rimuovere il solvente sotto pressione ridotta con un'unità di distillazione sotto vuoto ad alta, fino alla formazione di una polvere cristallina chiaro beige molto igroscopica (70%).</li>
</ol>3. della cristallizzazione
<ol><li>Sciogliere 4,3 g di polvere cristallina in 50 mL di etere etilico grado di freddo alta eseguita cromatografia liquida (HPLC). Filtro del vuoto la soluzione per rimuovere qualsiasi traccia di materiale solido di partenza o anche polvere. Versare il filtrato in un bicchiere di Petri, lasciandola a rallentare evaporare a 4 ° C in un frigorifero di laboratorio.</li>
	<li>Assicurarsi che dopo due giorni, si ottengono cristalli limpido incolore. Quindi misurare il punto di fusione, che dovrebbe essere nel range di K. 310-311</li>
</ol>4. analisi di 3,5-Lutidine N -ossido di disidratare
<ol><li>Rimuovere i cristalli che si formano, di forma prismatica e incolore, per decantazione dalle pareti del pallone per ulteriore analisi ai raggi x. Se non immediatamente utilizzato, è possibile mantenere i cristalli in etere etilico per evitare idratazione di cristallo.</li>
	<li>Sciogliere 0,010 g di 3,5-lutidine N -ossido di disidratare in 0,4 mL di CDCl3 per eseguire NMR H1 e C13 analisi per dimostrare l'efficacia della procedura.</li>
</ol>

<ol>
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Org. Chem. 82 (4), 2059-2066 (2017).</li><li>Merino Garc&#237;a, M. R., R&#237;os-Merino, F. J., Bern&#232;s, S., Reyes-Ortega, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+structure+of+3,5-dimethylpyridine+N-oxide+dihydrate.">Crystal structure of 3,5-dimethylpyridine N-oxide dihydrate.</a> Acta Cryst. 72 (12), 1687-1690 (2016).</li><li>Sarma, R., Karmakar, A., Baruah, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-Oxides+in+Metal-Containing+Multicomponent+Molecular+Complexes.">N-Oxides in Metal-Containing Multicomponent Molecular Complexes.</a> Inorg. 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Tutti gli autori non dichiarano alcun conflitto di interessi.

Il protocollo presentato qui è un metodo convenzionale per collegare un atomo di ossigeno all'atomo di azoto di 3,5-lutidine come un metodo di funzionalizzazione dei substrati. Questa tecnica è anche ben consolidata per produrre cristalli disidratati adatti di raggi x (Figura 5, le foto scattate con una fotocamera Sony DSC-HX300 Cyber-shot). Per quanto siamo preoccupati, non molti rapporti hanno descritto la produzione di tali cristalli16. Molti composti cresceranno cristalli id...

Al giorno d'oggi, gli scienziati di tutto il mondo hanno investito risorse nello sviluppo di nuove vie di sintesi per la funzionalizzazione dei gruppi aromatici, che sono conosciuti per la parte anteriore bassa reattività per aggiunta reazioni1,2, 3. Piridina, dove un atomo di azoto sostituisce un atomo di carbonio, presenta una reattività chimica simile analogico anelli è composto unicamente da atomi di carbonio3e subisce solitamente un meccanismo di sostituzione anziché aggiunta. N-ossidi si distinguono per la presenza di un legame di donatore tra azoto e ossigeno formata dalla sovrapposizione di nonbonding coppia di elettroni sull'azoto con un orbitale vuoto sul atomo di ossigeno3. In particolare, piridina N-ossido è basi di Lewis, perché loro frazione di N-O può agire come un donatore di elettroni, e si può combinare con acidi di Lewis, formando il corrispondente coppie acido-base di Lewis. Questa proprietà ha una conseguenza chimica essenziale, perché può aumentare la nucleofilicità degli acidi di Lewis verso potenziali elettrofili e quindi permettere loro di reagire in condizioni dove normalmente la reazione non si verificherebbe. Probabilmente l'uso più frequente di tali composti è nelle varie reazioni di ossidazione, dove agiscono come ossidanti4. Piridina N-ossidi e molti dei loro derivati funzionalizzati anello sono molecole ricorrenti di agenti biologicamente attivi e farmacologici5, e una distribuzione chiara spaziale di diversi strumenti spettroscopici è stata stabilita per alcuni di loro6,7. Nella ricerca sul collegamento di gruppi diversi per l'anello piridinico, gli scienziati hanno testato varie metodologie per produrre un metodo facile e convenzionale, dal isossazoline richiede una quantità catalitica di base quali DBU in ebollizione xilene per formare 6- sostituito-2-aminopyridine N-ossidi8,9. Una varietà di derivati della piridina sono stati convertiti in loro corrispondenti N-ossidi in presenza di una quantità catalitica di manganese tetrakis(2,6-diclorophenyl) porfirina e ammonio acetato CH2Cl2/CH3 CN8,10. Altri piridine sono ossidati a loro ossidi utilizzando H2O2 in presenza di quantità catalitiche di methyltrioxorhenium8,11, o con l'aggiunta di dimethyldioxirane in eccesso in CH2Cl2 a 0 ° C, che conduce al corrispondente N-ossidi8,12,13,14. Bis (trimetilsilile) perossido in presenza di trioxorhenium CH2Cl2 è stato utilizzato per la sintesi della piridina N-ossidi8,11. La sintesi di aminopiridina N-ossidi che coinvolge acilazione utilizzando (acido peroxomonosulfuric) di Caro è stato anche segnalato8. Tuttavia, la metodologia segnalato qui, e che utilizza parte della metodologia riportata da Ochiai1, fornisce risultati molto buoni con l'uso di reagenti più convenienti e accessibili, H2O2 e acido acetico glaciale. Questa pratica è più adatto ad uso nelle preparazioni su larga scala che agiscono sulle ammine terziarie, produce buone rese in una reazione che richiede solo 30% di perossido di idrogeno e acido acetico glaciale in una temperatura compresa tra 70-80 ° C e utilizza un processo di purificazione che è disponibile nella maggior parte dei laboratori di sintesi come la distillazione, senza l'uso del catalizzatore o più costosi reagenti1. La letteratura segnala che altre metodologie anche frequentemente coinvolgono tempo cornici da 10-24 h e temperature superiori a 100 ° C 4,8, e la resa di cristalli ben formati per analisi dei raggi x è segnalata raramente.
Reattivo, vari N -ossido derivati vengono utilizzati per attivare adeguatamente l'anello lutidine, in maniera elettrofila o nucleofila. Il fattore elettrofilo o nucleofilo risente i sostituenti. Con l'anello di piridina essendo i gruppi elettron-attrattori, il fattore principale è il nucleofilo caratteristica1. Il gratuito N-ossido composti sono raramente isolate come cristalli adatti per analisi di raggi x dovuto la carica delocalizzata sull'anello aromatico. Tuttavia, il fattore di solvatazione è fondamentale per stabilizzare la densità negativa dell' ossigeno15.

<table border="0" cellpadding="0" cellspacing="0" style="width:725px;" width="725">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:212px;">3,5-lutidine</td>
			<td style="width:228px;">Sigma-Aldrich</td>
			<td style="width:119px;">L4206-500ML</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glacial acetic acid</td>
			<td>Fermont</td>
			<td>3015</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hidrogen peroxide (35%)</td>
			<td>Sigma-Aldrich</td>
			<td>349887-500ML</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2CO3 anhydrous</td>
			<td>Productos Qu&#237;micos Monterrey</td>
			<td>1792</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2SO4 anhydrous</td>
			<td>Alfa reactivos</td>
			<td>25051-C</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">CHCl3</td>
			<td>Fermont</td>
			<td>6205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethyl eter</td>
			<td>Mercury Chemist</td>
			<td>QME0309</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Distilled water</td>
			<td>Comercializadora Qu&#237;mica Poblana</td>
			<td>not-existent</td>
			<td></td>
		</tr>
	</tbody>
</table>

syntheses, crystallization, and spectroscopic characterization of 3,5-lutidine n-oxide dehydrate

La sintesi di 3,5-lutidine N -ossido di disidratare, 1, è stata realizzata nell'itinerario della sintesi dell'acido 2-ammino-piridina-3,5-dicarbossilico. Ochiai prima usato la metodologia per non-sostituiti piridine nel 1957 in un processo di 12 h, ma sono stato ottenuto senza cristalli adatto ai raggi x. L'anello sostituito utilizzato nella metodologia presentata qui chiaramente influenzato l'aggiunta di molecole d'acqua nell'unità asimmetrica, che conferisce una forza nucleofila diversa in 1. I raggi x cristallo adatto composto 1 era possibile dovuto la stabilizzazione della carica negativa nell'ossigeno dalla presenza di due molecole d'acqua dove gli atomi di idrogeno donano carica positiva sul ring; tali molecole di acqua servono bene per costruire un'interazione supramolecolare. Le molecole idratate potrebbero essere possibile per il sistema alcalino che si raggiunge regolando il pH a 10. D'importanza, il metile doppio sostituito con anello e un tempo di reazione di 5h, lo rende un metodo più versatile e con applicazioni chimiche più ampia per gli inserimenti futuri anello.

Il protocollo è essenzialmente un'estensione di Ochiai tecnica1. Tuttavia, vengono applicate le temperature più basse e meno tempo. Questo semplice metodo può essere utilizzato per ottenere un ligando versatile, che è un sostitutivo piridina N-ossido derivato. Per confermare la formazione di 1, NMR 1H e 13C analisi sono preferiti per testare l'efficacia della procedura.
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Watch this Scientific Journal Video about Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate at JoVE.com

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

Qui, segnaliamo la sintesi e la cristallizzazione di 3,5-lutidine N -ossido di disidratare da un semplice protocollo che differisce dalla classica sintesi della piridina N-ossido. Questo protocollo utilizza materiale di partenza differente e comporta meno tempo di reazione per produrre una nuova struttura supramolecolare solvatato, che cristallizza sotto lenta evaporazione.

Sintesi, cristallizzazione e caratterizzazione spettroscopica di 3,5-Lutidine N-ossido di disidratare

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 ...

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Research

JoVE Journal

Chemistry

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

8.3K Views.  Benemérita Universidad Autónoma de Puebla. Qui, segnaliamo la sintesi e la cristallizzazione di 3,5-lutidine N -ossido di disidratare da un semplice protocollo che differisce dalla classica sintesi della piridina N-ossido. Questo protocollo utilizza materiale di partenza differente e comporta meno tempo di reazione per produrre una nuova struttura supramolecolare solvatato, che cristallizza sotto lenta evaporazione.

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

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

Split-e-pool Sintesi e caratterizzazione di peptidi Terziario Ammide Biblioteca

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

Ricerca

Chimica

Synthesis and Characterization of Functionalized Metal-organic Frameworks

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

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

Sintesi e caratterizzazione di funzionalizzato metallo-organici quadri

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

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated particles provide evidence for the validity of the DRIFTS measurement.

Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

Riflettanza diffusa infrarossi spettroscopica Identificazione disperdenti / particelle Bonding Meccanismi a inchiostri funzionali

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers.  A typical inkjet ink is a colloidal ...

A Filter-based Surface Enhanced Raman Spectroscopic Assay for Rapid Detection of Chemical Contaminants

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.

A procedure for fabrication and performing the filter-based surface enhanced Raman spectroscopic (SERS) assay for the detection of chemical contaminants (i.e., pesticide ferbam and antibiotic ampicillin) is presented.

Una Superficie-filtro basato avanzata Raman spettroscopica Assay per Rapid individuazione dei contaminanti chimici

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Sintesi e caratterizzazione di supramolecolari colloidi

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. Fundamental to these transitions is the intrinsic flexibility of the protein, which is critically modulated by membrane lipid-composition. To better understand the structural basis of channel function, it is necessary to study protein dynamics in a physiological membrane environment. Electron Paramagnetic Resonance (EPR) spectroscopy is an important tool to characterize conformational transitions between functional states. In comparison to NMR and X-ray crystallography, the information obtained from EPR is intrinsically of lower resolution. However, unlike in other techniques, in EPR there is no upper-limit to the molecular weight of the protein, the sample requirements are significantly lower, and more importantly the protein is not constrained by the crystal lattice forces. Therefore, EPR is uniquely suited for studying large protein complexes and proteins in reconstituted systems. In this article, we will discuss general protocols for site-directed spin labeling and membrane reconstitution using a prokaryotic proton-gated pentameric Ligand-Gated Ion Channel (pLGIC) from Gloeobacter violaceus (GLIC) as an example. A combination of steady-state Continuous Wave (CW) and Pulsed (Double Electron Electron Resonance-DEER) EPR approaches will be described that will enable a complete quantitative characterization of channel dynamics.

This article describes methods for site-directed spin labeling and reconstitution of pentameric ligand-gated channels for Electron Paramagnetic Resonance studies. This protocol can be adapted for any membrane protein. The reconstitution method described here can also be used for patch-clamp measurements of macroscopic and single-channel currents in a defined lipid system.

Sito-Labeling Spin e EPR spettroscopiche Studi di canali pentamerica ligando-dipendenti Ion

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparazione e caratterizzazione di nanostrutture ibride C60/Graphene

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

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.

Sintesi di un tiolo Building Block per la cristallizzazione di un quadro di Gyroidal metallo-zolfo ossidi semiconduttori

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

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.

Elettroforetica cristallizzazione delle membrane ultrasottile ad alte prestazioni Metal-organic frameworks

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

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Sintesi e caratterizzazione delle nanoparticelle d'oro dell'anfifile

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...