AP is grateful to Imperial College London for a PhD studentship via the Frankland Chair endowment. Johnson Matthey plc are also thanked for the loan of the precious metal salts used in this work.

Hinweis: Führen Sie alle Synthesen in einem Abzug, und erst nach einer entsprechenden Sicherheitsprobleme wurden identifiziert und Maßnahmen ergriffen, um gegen sie zu schützen. Persönliche Schutzausrüstung gehören ein Laborkittel, Schutzhandschuhe und Schutzbrille und müssen immer getragen werden. 1. Synthese von N, N, N-Tris (diphenylphosphinomethylene) amin, N (CH 2 PPh 2) 3 (N -triphos Ph) (1) <ol><li> In einen 200 ml-Schlenk-Kolben Ofen getrocknet hinzufügen Diphenyl (Hydroxymethylen) phosphoniumchlorid 11 (6,99 g, 24,7 mmol) und Ort unter Stickstoff über drei aufeinanderfolgende Vakuum-Stickstoffkreislauf auf einem Doppelverteilerschlenklinie. </li><li> Hinzufügen entgastem Methanol (30 ml) und Triethylamin (9,5 ml, 68,1 mmol), zugegeben und bei RT für 1 h, um die Umwandlung des phosphoniumchlorid Salz dem hydroxymethene Phosphin gewährleisten. Als Nächstes fügen Sie entgast Ammoniaklösung in Methanol (2 M, 4,1 ml, 8,2 mmol). </li><li> Erhitzen Sie das Reaktionsgemisch 2 h unter Rückfluss, In dem der Ligand als ein weißer Feststoff auszufällen. </li><li> Obwohl die N -triphos Ph Ligand stabil gegenüber Oxidation an der Luft während kurzer Zeiträume, für die optimale Reinheit, das Lösemittel wird über eine Kanüle 26 Filtration unter Stickstoff, und Spülen mit entgastem Methanol (3 x 10 ml), um ein analytisch reines Produkt zu erhalten , und speichern Sie unter einer Stickstoffatmosphäre. </li></ol> 2. Synthese von [Ru (CO) 2 {N (CH 2 PPh 2) 3} -κ 3 P] (2) <ol><li> In einen 200 ml-Schlenk-Kolben Ofen getrocknet, fügen N -Triphos Ph (1,0 g, 1,63 mmol) und [Ru 3 (CO) 12] (347 mg, 0,54 mmol) und Platz unter Stickstoff über drei aufeinanderfolgende Vakuum-Stickstoffkreislauf auf ein Doppelverteilerschlenklinie. </li><li> 30 ml trockenes, entlüftetes Toluol und bringt die Mischung für 12 h auf Rückflußtemperatur. </li><li> Nach Ablauf dieser 12 Stunden Rückfluss, filtriert die Lösung über eine Kanüle in einen zweiten Schlenk-Kolben zuEntfernen kleiner Mengen von metallischem Ruthenium, die im Laufe der Reaktion bilden. </li><li> Reduzieren des Volumens des Lösungsmittels auf etwa 10 ml im Vakuum unter Verwendung eines Doppelverteiler Schlenk- mit flüssigem Stickstoff gekühlten Falle eingepasst, um eine Ausfällung des Komplexes induzieren. </li><li> Man kristallisiert den Niederschlag durch gelindes Erwärmen (80-90 ° C) in einem Ölbad bis zur vollständigen Wiederauflösung auftritt, und nachfolgendes langsames Abkühlen auf RT durch Entfernen der Wärme aus dem Ölbad, aber so dass der Schlenkkolben zu untergetaucht bleiben. Lassen Sie O / N, um eine orange kristalliner Feststoff erhalten. </li><li> Isolieren Sie die orangefarbene Kristalle für Röntgenbeugung über eine Kanüle Filtration des Überstandes in ein anderes Ofen getrocknet Schlenkkolben. Anschließend spülen Sie die Kristalle mit trockenem und entgastem Toluol (2 x 5 ml) gewaschen und im Vakuum getrocknet O / N. Speichern Sie die kombinierte Überstand und die Waschlösungen in einem separaten Schlenkkolben. </li><li> Besorgen Sie sich eine zweite Charge von Kristallen aus der kombinierten Überstand und Spüllösungs durch ein ähnliches Rekristallisationsprozeß den Schritten 2.5 und 2.6 zur Verbesserung der Gesamtausbeute der Reaktion. </li><li> Speichern den Komplex unter Stickstoff als an der Luft führt zu einer langsamen Umwandlung in das oxidierte Carbonat-Komplexes (siehe unten). </li></ol> 3. Synthese von [Ru (CO 3) (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (3) <ol><li> In einen 200 ml Schlenkkolben gegeben, mit 2 (280 mg, 0,364 mmol) und 5 ml Toluol gelöst, um eine teilweise orange Suspension zu erzeugen. </li><li> Legen Sie eine Nadel an einem Ballon von Sauerstoff in die Suspension und Blasen Sauerstoff gebunden mit einer Rate von 2-3 Blasen pro Sekunde durch das Reaktionsgemisch für 10 min. </li><li> Als oranges Präzipitat bildet, sammeln sie durch Filtration an der Luft und mit Toluol (2 x 5 ml) und Diethylether (2 x 5 ml) gewaschen und trocken im Vakuum zu einem rieselfähigen orangen Pulvers, das in Luft stabil wurde. </li><li> Um Kristalle für Röntgen diffr wachsenAktion, werden 100 mg 3 in 3 ml Dichlormethan in einem Fläschchen und Layer 3 ml Toluol auf langsam so dass diese Lösungsmittel zu laufen an der Seite des Fläschchens. <ol><li> Lassen Sie das O / N, um Kristalle zu erhalten. Isolieren der Kristalle durch Dekantieren des Überstandes und dem Waschen der Toluol (2 x 3 ml) und Diethylether (2 x 3 ml). Trockene im Vakuum auf einem Doppelverteilerschlenklinie. </li></ol></li></ol> 4. Synthese von [Ru (H) 2 (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (4) <ol><li> Es wird eine Lösung von 3 (763 mg, 0,953 mmol) in 20 ml trockenem, entgastem THF und spritzen in einen 100 ml Autoklav Engineers Hochdruckreaktor unter Überdruck (0,2 bar) von Stickstoff. </li><li> Ändern der Reaktorkopfraum Gas 100% Wasserstoff und unter Druck auf 15 bar bei RT, dann Hitze auf 100 ° C unter Rühren 2 Std. Vorsicht! Achten Sie darauf, alle Sicherheitsverfahren bei der Verwendung von Hochhalten wurdenDrucksysteme! </li><li> Nach Abkühlen auf RT, sorgfältiges Entlüften des überschüssigen Wasserstoffgas im Kopfraum des Reaktors und verändern Stickstoff. </li><li> Übertragen die Reaktionslösung in einen 100 ml Schlenkkolben unter Stickstoff, und nach der Wiederverbindung mit einer Doppelverteilerschlenkleitung, Filter mit einer Kanüle und mit 20 ml trockenem verdünnen, entgastem Methanol. </li><li> Das Lösemittel wird unter Vakuum mit einem Doppelverteilerschlenklinie mit einer Flüssigstickstoffkühlfalle ausgestattet, um ein oranges Pulver. Mit trockenem, entgastem Methanol (3 x 5 ml) und trockenem Waschen Sie diese orangefarbenes Pulver, entgast Diethylether (3 x 5 ml) gewaschen und im Vakuum getrocknet. </li><li> Wachsen Kristalle für Röntgenbeugungsanalyse O / N von einer gesättigten trockenen und entgasten Toluollösung von 4 mit einem gleichen Volumen Menge an Trocken geschichtet, entgastem Methanol. </li><li> Bewahren Sie die komplexe unter Stickstoff. </li></ol> 5. Reaktion von [RuH 2 (CO) {N (CH 2 PPh 2) 3} 3 P -κ] (4) mit NH 4 PF 6 und Levulinsäure <ol><li> Es wird eine Lösung von 4 (48,4 mg, 65,2 uMol) in 2 ml trockenem, entgastem Toluol in einem Ofen getrocknet Schlenkkolben, und geben über eine Spritze zu einer gerührten Lösung von NH 4 PF 6 (10,6 mg, 65,0 umol) in Acetonitril (2 ml) in einem separaten Ofen getrocknet Schlenkkolben. </li><li> Rühre das Reaktionsgemisch bei RT für 2 Std. Nach Entfernen des Lösungsmittels im Vakuum mit einem Doppelverteilerschlenklinie mit einer Flüssigstickstoffkühlfalle ausgestattet, um die Zwischen [RuH (CO) (MeCN) {N (CH 2 PPh 2) 3} -κ 3 P] geben ( 5). </li><li> Waschen mit trockenem, entgastem Hexan (3 x 3 ml) und im Vakuum getrocknet, um komplexe 5 als braunes Pulver zu isolieren. </li><li> Zu einer Lösung von 5 in 0,5 ml entgastem Aceton-d 6, hinzuzufügen Lävulinsäure (10,8 mg, 93,0 &amp; mgr; mol, 1,43 Äquiv.) In 0,5 ml entgastem Aceton-d 6. Das Reaktionsgemisch wird für 2 min mitein Wirbel Rührer. </li><li> Aufnahme 1 H und 30 P {1 H} -NMR-Spektren des Reaktions jede Stunde für 16 Stunden, um die Reaktion zu beobachten. 27 </li></ol>

<ol>
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The authors have nothing to disclose.

Wir haben hier effizienter Syntheseverfahren für die Synthese eines dreizähnigen Phosphin-Liganden und einer Reihe von Rutheniumkomplexen beschrieben. Die N -triphos Ph-Liganden (1) kann leicht in hoher Ausbeute mit einem minimalistischen Aufarbeitung Verfahren hergestellt werden. Diese Phosphorbasis Mannich-Reaktion verwendet, um diese Arten von Liganden zu synthetisieren, ist sehr allgemein und kann für andere Ligand-Derivate mit unterschiedlichen R-Gruppen an den P-Atomen verwe...

Ruthenium Phosphin Komplexe sind einige der am meisten untersuchten und chemisch vielseitig molekulare Katalysatoren. 1-9 Typischerweise sind solche Rutheniumkatalysatoren enthalten entweder ein- oder zweizähnigen Liganden, der die Elektronik, Sterik, Geometrie und die Löslichkeit des Komplexes zu diktieren, und welche zutiefst Auswirkungen auf die katalytische Aktivität. Mehrzähnigen Phosphin-Systeme wurden weniger häufig für die Katalyse untersucht, wie sie bekannt sind, um eine größere Stabilität auf dem Metallzentrum wegen der größeren Chelateffekt mehrerer Phosphor Spender am Metallzentrum zu vermitteln. Eine solche Stabilisierung kann unerwünscht Katalyse jedoch unter härteren Reaktionsbedingungen (höhere Temperaturen und Drücke) komplexstabilisierende Eigenschaften solcher Liganden kann vorteilhaft bei der Gewährleistung Katalysator Integrität. Eine solche mehrzähnigen Phosphinliganden System, das wir 10 bis 12 und 13 bis 18 andere wurden für Komplexstabilität und Gesichts Koor Vermittlung untersuchtrung Geometrien ist die sogenannte N -triphos Ligand Serie wo drei Phosphin Arme an einem apikalen Brückenstickstoffatom einen potentiell dreizähnigen Liganden gebunden. Eines der Schlüsselmerkmale auf diese speziellen Liganden ist die einfache Art und Weise, dass sie sich über eine auf Phosphor basierende Mannichreaktion aus leicht erhältlichen sekundären Phosphine (1) synthetisiert werden, also Phosphine mit einer Vielzahl von R-Gruppen können in der Regel in hohen Ausbeuten hergestellt werden, und mit minimalem Aufarbeitung. Das übergeordnete Ziel dieser Methodik ist es, einen einfachen Weg, auf dem Ruthenium Dihydrid Komplexe mit N -triphos Liganden können für die anschließende katalytische Anwendungen zugänglich zu präsentieren. Kürzlich wurden Ru-triphos Komplexe Aufmerksamkeit als Katalysatoren für die Hydrierung von Biomasse abgeleitete Produkte, wie Lävulinsäure, 19,20 bio-Ester 11,21 und Kohlenstoffdioxid 22 zu höherwertigen Chemikalien zogen. Es wäre vorteilhaft,den Umfang der Ru-triphos Derivate, die entweder wie oder aktiver als die Systeme bereits berichtet, vor allem wenn sie synthetisch leichter zugänglich, wie der n -triphos Ligand erweitern. Die am besten untersuchten Kohlenstoff-zentrierte analogen leidet in der Regel aus niedrig verzinsten Synthese und beinhaltet sehr luftempfindlichen Metallphosphid Reagenzien, im Gegensatz zu der N -triphos Liganden, der anpassungsfähiger und leichter herzustellen ist. 10-18 N -triphos Liga bleiben relativ untersuchten, nur mit Molybdän, Wolfram, Ruthenium, Rhodium und Gold-Komplexe mit neun Veröffentlichungen berichtet. Dies steht in krassem Gegensatz zu den bor- und kohlenstoffzentrierten Analoga, für die es etwa 50 und 900 Artikel, die jeweils mit einer großen Anzahl von einzigartigen Verbindungen. Dennoch N -triphos haltige Komplexe haben festgestellt, Anwendung in der asymmetrischen katalytischen Hydrierung von prochiralen Olefinen 23 als wirll als asymmetrische cyclohydroamination von N-geschützten γ-Allenyl Sulfonamide. 24 Zusätzlich wird ein Ruthenium-Komplex durch eine sperrige N -triphos Ligand mit Phospholan koordinierende Einheiten koordiniert wurde festgestellt, Silane, einen wichtigen Schritt in der Entwicklung der siliciumorganischen Chemie zu aktivieren. 25 Im Rahmen des laufenden Forschungsprogramms in der Katalyse, haben wir versucht, eine Reihe von Ruthenium N -triphos Ph Präkatalysatoren vorzubereiten und ihre stöchiometrische Reaktionen und katalytische Potential zu untersuchen. Trotz Molybdänkomplexe von N -triphos Ph nachdem zum ersten Mal vor über 25 Jahren berichtet worden, deren Anwendung, katalytische oder nicht wurde nicht untersucht. Diese Arbeit zeigt die Anwendbarkeit des N -triphos Gerüst, die, obwohl sie in der Regel unterentwickelt, besitzen viele wünschenswerte Eigenschaften wie Komplexstabilität. Hier berichten wir über den Syntheseweg und Charakterisierung zu berichten,eine Reihe von Ruthenium N -triphos Ph-Komplexe, die Anwendung in katalytischen Hydrierungsreaktionen finden.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Methanol</td>
			<td rowspan="5">&#8211;</td>
			<td rowspan="5">&#8211;</td>
			<td rowspan="5">Obtained from in-house solvent purification system: Innovative Technology, inc &#34;pure solv&#34; drying tower. Stored in ampules over activated molecular sieves under nitrogen.</td>
		</tr>
		<tr>
			<td>Toluene</td>
		</tr>
		<tr>
			<td>Diethyl Ether</td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF)</td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
		</tr>
		<tr>
			<td>d6-Acetone</td>
			<td>VWR</td>
			<td>VWRC87152.0011</td>
			<td>Store in fridge</td>
		</tr>
		<tr>
			<td>Triethylamine</td>
			<td>Sigma-Aldrich</td>
			<td>TO886-1L</td>
			<td>Distilled and stored over activated molecular sieves under N2</td>
		</tr>
		<tr>
			<td>2M Ammonia solution in methanol</td>
			<td>Sigma-Aldrich</td>
			<td>341428-100ML</td>
			<td>Solution comes in a &#34;Sure-Seal&#34; bottle</td>
		</tr>
		<tr>
			<td>NH4PF6</td>
			<td>Sigma-Aldrich</td>
			<td>216593-5G</td>
			<td>Store in desiccator</td>
		</tr>
		<tr>
			<td>Levulinic Acid</td>
			<td>Acros Organics</td>
			<td>125142500</td>
			<td>Solid but melts close to room temperature</td>
		</tr>
		<tr>
			<td>3 &#197; Molecular sieves</td>
			<td>Alfa Aesar</td>
			<td>LO5359</td>
			<td>Activate by heating over night under vacuum</td>
		</tr>
		<tr>
			<td>Schlenk flasks</td>
			<td>GPE</td>
			<td>Custom design</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>Dual-manifold Schlenk line</td>
			<td>GPE</td>
			<td>Custom design</td>
			<td>Dual-manifold of i) N2 that has been passed through a silica drying column and ii) vacuum.</td>
		</tr>
		<tr>
			<td>Rotary vacuum pump</td>
			<td>Edwards</td>
			<td>RV3 A652-01-903</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>100 ml Autoclave Engineer&#39;s high pressure reactor</td>
			<td>Autoclave Engineer</td>
			<td>Custon design</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>Vortex Stirrer</td>
			<td>VWR</td>
			<td>444-1378</td>
			<td>&#8211;</td>
		</tr>
	</tbody>
</table>

the synthesis, characterization and reactivity of a series of ruthenium n-triphosph complexes

Hier berichten wir über die Synthese eines dreizähnigen Phosphin-Liganden N (CH 2 PPh 2) 3 (N -triphos Ph) (1) über eine auf Phosphor basierende Mannich Reaktion des hydroxylmethylene Phosphin Vorstufe mit Ammoniak in Methanol unter einer Stickstoffatmosphäre. Die N -triphos Ph Ligand aus der Lösung ausfällt nach ca. 1 h Reflux und isoliert unter Stickstoff analytisch rein über einfache Kanüle Filtrationsvorgang werden. Reaktion des N -triphos Ph-Liganden mit [Ru 3 (CO) 12] unter Rückfluss bietet eine tiefrote Lösung, die Entwicklung von CO-Gas auf Komplexliganden zeigen. Orangefarbene Kristalle des Komplexes [Ru (CO) 2 {N (CH 2 PPh 2) 3} -κ 3 P] (2) wurden beim Abkühlen auf RT isoliert. Die 31 P {1 H} NMR-Spektrum zeigte einen charakteristischen einzelnen Peak bei niedrigeren Frequenzim Vergleich zu dem freien Liganden. Reaktion einer Toluol-Lösung von Komplex 2 mit Sauerstoff in Folge der momentanen Ausfällung des Carbonat-Komplex [Ru (CO 3) (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (3) als Luft stabile orangefarbenen Feststoff. Anschließende Hydrierung von 3 unter 15 bar Wasserstoff in einem Hochdruckreaktor ergab das Dihydrid [RuH 2 (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (4), die vollständig durch X gekennzeichnet wurden -ray-Kristallographie und NMR-Spektroskopie. Komplexe 3 und 4 sind potenziell nützliche Katalysatorvorläufer für einen Bereich von Hydrierungsreaktionen, einschließlich Biomasse stammenden Produkten, wie Lävulinsäure (LA). Komplex 4 wurde gefunden, dass sauber reagieren mit LA in Gegenwart von Protonenquelle Additiv NH 4 PF 6, um [Ru (CO) {N (CH 2 PPh 2) 3} -κ 3 P {CH 3 CO (CH 2) 2 CO 2 H} -κ 2 O] (PF 6) (6).

Die N -triphos Ph Ligand (1) und der Rutheniumkomplex der Reihe: Ru (CO) 2 {N (CH 2 PPh 2) 3} -κ 3 P] (2) [Ru (CO 3) (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (3) und [Ru (H) 2 (CO) {N (CH 2 PPh 2) 3} -κ 3 P] (4) wurden durch 1 H ist, 13 C {1 H}, ...

Watch this Scientific Journal Video about The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes at JoVE.com

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium Phosphinkomplexe werden häufig für die homogene katalytische Reaktionen wie Hydrierungen eingesetzt. Die Synthese einer Reihe von neuartigen dreizähnigen Ruthenium-Komplexe mit dem N -triphos Liganden N (CH 2 PPh 2) 3 gemeldet. Zusätzlich wird die stöchiometrische Umsetzung eines Dihydrid Ru N -triphos Komplex mit Lävulinsäure beschrieben.

Die Synthese, Charakterisierung und Reaktivität von einer Serie von Ruthenium<em&gt; N</em&gt; -triphos<sup&gt; Ph</sup&gt; Komplexe

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

the-synthesis-characterization-reactivity-series-ruthenium-n

Research

JoVE Journal

Chemistry

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

12.0K Aufrufe.  Imperial College London.  Ruthenium Phosphinkomplexe werden häufig für die homogene katalytische Reaktionen wie Hydrierungen eingesetzt. Die Synthese einer Reihe von neuartigen dreizähnigen Ruthenium-Komplexe mit dem N -triphos Liganden N (CH 2 PPh 2) 3 gemeldet. Zusätzlich wird die stöchiometrische Umsetzung eines Dihydrid Ru N -triphos Komplex mit Lävulinsäure beschrieben. 

Serie: The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

Physical interactions among the lipid-embedded alpha-helical domains of membrane proteins play a crucial role in folding and assembly of membrane protein complexes and in dynamic processes such as transmembrane (TM) signaling and regulation of cell-surface protein levels. Understanding the structural features driving the association of particular sequences requires sophisticated biophysical and biochemical analyses of TM peptide complexes. However, the extreme hydrophobicity of TM domains makes them very difficult to manipulate using standard peptide chemistry techniques, and production of suitable study material often proves prohibitively challenging. Identifying conditions under which peptides can adopt stable helical conformations and form complexes spontaneously adds a further level of difficulty. Here we present a procedure for the production of homo- or hetero-dimeric TM peptide complexes from materials that are expressed in E. coli, thus allowing incorporation of stable isotope labels for nuclear magnetic resonance (NMR) or non-natural amino acids for other applications relatively inexpensively. The key innovation in this method is that TM complexes are produced and purified as covalently associated (disulfide-crosslinked) assemblies that can form stable, stoichiometric and homogeneous structures when reconstituted into detergent, lipid or other membrane-mimetic materials. We also present carefully optimized procedures for expression and purification that are equally applicable whether producing single TM domains or crosslinked complexes and provide advice for adapting these methods to new TM sequences.

Biophysical and biochemical studies of interactions among membrane-embedded protein domains face many technical challenges, the first of which is obtaining appropriate study material. This article describes a protocol for producing and purifying disulfide-stabilized transmembrane peptide complexes that are suitable for structural analysis by solution nuclear magnetic resonance (NMR) and other analytical applications.

Produktion von Disulfid-stabilisierte Transmembrane Peptid-Komplexe für Structural Studies

Physical  interactions among the lipid-embedded alpha-helical domains of membrane  proteins play a crucial role in folding and assembly of membrane ...

Forschung

Chemie

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS can be subdivided into three domains: the distal O-polysaccharide, a core oligosaccharide, and the lipid A domain consisting of a lipid A molecular species and 3-deoxy-D-manno-oct-2-ulosonic acid residues (Kdo). The lipid A domain is the only component essential for bacterial cell survival. Following its synthesis, lipid A is chemically modified in response to environmental stresses such as pH or temperature, to promote resistance to antibiotic compounds, and to evade recognition by mediators of the host innate immune response. The following protocol details the small- and large-scale isolation of lipid A from gram-negative bacteria. Isolated material is then chemically characterized by thin layer chromatography (TLC) or mass-spectrometry (MS). In addition to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS, we also describe tandem MS protocols for analyzing lipid A molecular species using electrospray ionization (ESI) coupled to collision induced dissociation (CID) and newly employed ultraviolet photodissociation (UVPD) methods. Our MS protocols allow for unequivocal determination of chemical structure, paramount to characterization of lipid A molecules that contain unique or novel chemical modifications. We also describe the radioisotopic labeling, and subsequent isolation, of lipid A from bacterial cells for analysis by TLC. Relative to MS-based protocols, TLC provides a more economical and rapid characterization method, but cannot be used to unambiguously assign lipid A chemical structures without the use of standards of known chemical structure. Over the last two decades isolation and characterization of lipid A has led to numerous exciting discoveries that have improved our understanding of the physiology of gram-negative bacteria, mechanisms of antibiotic resistance, the human innate immune response, and have provided many new targets in the development of antibacterial compounds.

Isolation and characterization of the lipid A domain of lipopolysaccharide (LPS) from gram-negative bacteria provides insight into cell surface based mechanisms of antibiotic resistance, bacterial survival and fitness, and how chemically diverse lipid A molecular species differentially modulate host innate immune responses.

Isolierung und chemische Charakterisierung von Lipid A von gramnegativen Bakterien

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS ...

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Anti-Krebs-Metall-Komplexe: Synthese und Zytotoxizität Bewertung durch die MTT-Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

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-and-Pool-Synthese und Charakterisierung von Peptid-Amid-Tertiär-Bibliothek

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

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

Nucleosidtriphosphaten - von der Synthese zur biochemischen Charakterisierung

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

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.

Synthese und Charakterisierung von funktionalisierten Metall-organische Gerüste

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

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.

Synthese und Charakterisierung von supramolekularen Kolloid-

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

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

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

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

Synthese cyclischer Polymere und Charakterisierung ihrer Diffusionsbewegung im geschmolzenen Zustand auf der Einzelmolekülebene

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

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

Solid-State-und Lösungsorientierte Techniken Kombination: Synthese und Reaktivität von Chalcogenidoplumbates (II oder IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Palladium<em&gt; N.</em&gt; -Heterocyclische Carbenkomplexe: Synthese aus Benzimidazoliumsalzen und katalytische Aktivität bei Kohlenstoff-Kohlenstoff-Bindungs-bildenden Reaktionen

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...