Recette de solution de rétrécissement est du laboratoire de RW Aldrich. Nous remercions les organismes de financement et fondations suivantes pour le soutien: National Institutes of Health, National Science Foundation, l&#39;American Heart Association, la Muscular Dystrophy Association, le B. Donald E. Baxter et Delia Fondation, le Fonds de dotation et les Klingenstein McKnight for Neuroscience.

Partie 1: Retrait de la membrane vitelline <ol><li> Préparer deux séries de pinces. Nous préférons n ° 5 pinces, où un ensemble a été légèrement taillé avec un fichier. Préparez aussi une pipette de transfert en verre par parage et polissage au feu un 7 &quot;pipette Pasteur. </li><li> Recommandé: Pour prévenir les ovocytes de glisser, couper un cercle de grille (carrés de 1 mm) et de la colle dans le fond d&#39;un plat de Pétri 60mm. Ce plat peut être réutilisé indéfiniment si maintenu propre entre deux utilisations. </li><li> Remplissez la boîte de Pétri avec une solution à mi-chemin hyperosmotiques (voir recette) et placer sous un microscope à dissection. </li><li> Retirer 1-3 ovocytes de Xenopus de leur solution d&#39;incubation avec une pipette Pasteur polie et le placer dans le plat. </li><li> Attendre 15s - 2 min pour les cellules de commencer à se rétrécir. Des temps plus longs rendent les cellules plus faciles à peler; réduction des délais de cellules saines pour patcher. </li><li> Comme les cellules se rétrécit, la membrane vitelline va commencer à devenir à peine visible comme une couche transparente sur la cellule. Sélectionnez une cellule saine (sans verticilles ou défauts) pour peler. </li><li> Avec une paire de pince, pincez doucement la membrane vitelline, sans endommager la membrane plasmique. Avec l&#39;autre, saisir près au même endroit et doucement déchirer la membrane claire et libre en dehors de la cellule. </li><li> Avec la pipette Pasteur, soigneusement déplacer la cellule vers la chambre d&#39;enregistrement. Notez que la cellule va être fragile après le retrait vitelline. </li></ol> Partie 2: génération Gigaseal <ol><li> Remplir une pipette d&#39;enregistrement avec une solution saline. Utilisez le volume minimal de solution qui permet un bon contact électrique avec le fil électrode afin de minimiser la capacité pipette. </li><li> Flick la pipette plusieurs fois pour permettre aux bulles à flotter et glisser sur le fil électrode. Appliquer une pression à la pipette remplie. Cela peut être fait par la bouche ou avec une pompe d&#39;aquarium dans une animalerie. Cette pression est essentiel pour maintenir la pipette nettoie comme il traverse l&#39;interface liquide et se déplace à la cellule. </li><li> Trouvez l&#39;ovocyte dans la chambre et de se concentrer fortement sur le bord de la cellule. </li><li> Avec la pipette de la baignoire, le centre de la pointe (hors foyer) au-dessus de la cellule. Cette fois-ci minimise passé dans le bain avant la génération de phoque. </li><li> Baisse de la pipette vers le bas dans la prochaine mise au point nette à la cellule. Le mettre en proximité (~ 50 microns). Vous devriez voir une petite distorsion de solution poussé hors de la pipette par la pression. </li><li> Utilisation du logiciel de patch-clamp, vérifier la résistance de la pipette (notre but est d&#39;environ 3-4 MQ) et zéro le courant en utilisant la tension de décalage. </li><li> Avec une pression positive sur la pipette, déplacer la pointe lentement vers la cellule tout en surveillant la résistance visuellement ou en utilisant un moniteur audio qui génère un signal dont la fréquence est proportionnelle à la résistance. Comme la pointe commence à toucher la cellule, la résistance va augmenter. </li><li> Soudain, mais doucement basculer du positif au négatif de la pression d&#39;environ la même valeur absolue. Résistance devrait augmenter pour sceller la formation. </li><li> La plupart du temps, la formation de joint se produit en quelques secondes, parfois 30-60 secondes sont nécessaires. </li><li> Une fois que la résistance est à 1GΩ, la pression peut être libérée à neutre. Vous avez maintenant un patch sur les cellules. Pour un patch à l&#39;envers, tirez hors de la cellule rapidement. Pour l&#39;extérieur-out, voir ci-dessous. </li></ol> Partie 5: Hors-out topologie (facultatif) <ol><li> Immédiatement après la réalisation d&#39;un gigaseal, la rupture de la membrane. Cela peut être fait avec aspiration forte, mais nous préférons une impulsion de 1 V pour 1 ms. La résistance devrait tomber à un peu plus de la résistance pipette initiale. </li><li> Déplacer la pipette hors de la cellule lentement et en douceur. Vous devriez voir une section de la traction cellule avec la pipette. Soudain, et au sein de quelques secondes, la cellule se cassera le dos et la résistance doivent immédiatement et simultanément retour à GΩs. </li><li> Vous avez maintenant un patch dans la configuration hors-out. Le ectodomaines de tout les canaux ioniques inclus est exposé à la baignoire. </li></ol> Partie 6: Résultats prévus Généralement, les joints de résistance plus élevées sont préférables et plus vivaient. 10 GQ est un bon guide pour la haute qualité des joints. Dans notre expérience, les chances d&#39;obtenir des joints de cette qualité varie en fonction de nombreux facteurs, notamment la cellule et la pipette de qualité. Taux d&#39;acquisition patch peut être plus de 95% avec des cellules saines, des pipettes propre, et un chercheur expérimenté. Ces correctifs peuvent durer pendant plusieurs minutes et sont adaptés à toute étude électrophysiologique des canaux ioniques exprimés dans des ovocytes de Xenopus, y compris les enregistrements mono-canal.

<ol>
	<li>Neher, E., Sakmann, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-channel+currents+recorded+from+membrane+of+denervated+frog+muscle+fibres.">Single-channel currents recorded from membrane of denervated frog muscle fibres.</a> Nature. 260, 799-802 (1976).</li><li>Sackmann, B., Neher, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Single-channel Recording. , (1983).</li></ol>

Il ya de nombreux paramètres d&#39;enregistrement électrophysiologiques pas discuté ici. Configuration Rig, la gestion du bruit du système, l&#39;expression de canaux, et des protocoles d&#39;enregistrement sont tous également critique pour de bons résultats expérimentaux. Dans notre expérience, ce sont les paramètres les plus critiques pour la formation de joints d&#39;étanchéité fiable: ovocytes de grande qualité, en enlevant la membrane vitelline rapidement (aka, «peeling»), utiliser des pipettes nouvellement tiré...

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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Patch Clamp Amplifier & Software</td>
<td>Instrument</td>
<td>HEKA or Axon</td>
<td>EPC-10</td>
<td>Or other similar device (e.g. HEKA EPC-9 or Axopatch 200B)</td>
</tr>
<tr>
<td>No. 5 forceps (two pairs)</td>
<td>Tool</td>
<td>Fine Science Tools</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Oocyte shrinking solution</td>
<td>Reagent</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Ingredient In mM
N-methyl-D-glucamine 220
HEPES 10
MgCl2 1
EGTA 10
Aspartic Acid 220
KCl 2
pH to 7.4 w/ N-methyl-D-glucamine</td>
</tr>
<tr>
<td>woven mesh</td>
<td>800 um</td>
<td>Spectrum Laboratories INC</td>
<td>146481</td>
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patch clamp recording of ion channels expressed in  xenopus oocytes

Depuis son développement en Sakmann et Neher 1, 2, le patch-clamp s&#39;est imposé comme une technique extrêmement utile pour la mesure électrophysiologique des canaux ioniques uniques ou multiples dans les cellules. Cette technique peut être appliquée aux canaux ioniques, tant dans leur environnement natif et exprimé dans des cellules hétérologues, tels que des ovocytes récoltés à partir de la grenouille africaine griffes, Xenopus laevis. Ici, nous décrivons la technique bien établie de l&#39;enregistrement de patch-clamp à partir d&#39;ovocytes de Xénope. Cette technique est utilisée pour mesurer les propriétés des canaux ioniques exprimés soit au sein des populations (macropatch) ou individuellement (un seul canal d&#39;enregistrement). Nous nous concentrons sur les techniques pour maximiser la qualité de la préparation des ovocytes et la génération de phoque. Avec tous les facteurs optimisée, cette technique donne une probabilité de succès au cours de génération d&#39;étanchéité 90 pour cent. Le processus peut être optimisé différemment par chaque chercheur sur la base des facteurs qu&#39;il ou elle trouve le plus important, et nous présentons la démarche qui ont conduit à la plus grande réussite dans nos mains.

Watch this Scientific Journal Video about Patch Clamp Recording of Ion Channels Expressed in  Xenopus Oocytes at JoVE.com

Patch Clamp Recording of Ion Channels Expressed in  Xenopus Oocytes

Ceci est conçu comme une introduction à l&#39;enregistrement de patch clamp à partir d&#39;ovocytes de Xenopus laevis. Il couvre l&#39;enlèvement membrane vitelline, la formation d&#39;un joint gigaohm (gigaseal), et la conversion en option du patch à la topologie en dehors-out.

Enregistrement Patch Clamp des canaux ioniques exprimés dans les oocytes de Xenopus

Since its development by Sakmann and Neher 1, 2, the patch clamp has become established as an extremely useful technique for electrophysiological ...

patch-clamp-recording-of-ion-channels-expressed-in-xenopus-oocytes

Research

JoVE Journal

Biology

26.0K vues.  Stanford University. Ceci est conçu comme une introduction à l'enregistrement de patch clamp à partir d'ovocytes de Xenopus laevis. Il couvre l'enlèvement membrane vitelline, la formation d'un joint gigaohm (gigaseal), et la conversion en option du patch à la topologie en dehors-out.

Vidéo: Patch Clamp Recording of Ion Channels Expressed in  Xenopus Oocytes

Methods for Patch Clamp Capacitance Recordings from the Calyx

We demonstrate the basic techniques for presynaptic patch clamp recording at the calyx of Held, a mammalian central nervous system nerve terminal. Electrical recordings from the presynaptic terminal allow the measurement of action potentials, calcium channel currents, vesicle fusion (exocytosis) and subsequent membrane uptake (endocytosis). The fusion of vesicles containing neurotransmitter causes the vesicle membrane to be added to the cell membrane of the calyx. This increase in the amount of cell membrane is measured as an increase in capacitance. The subsequent reduction in capacitance indicates endocytosis, the process of membrane uptake or removal from the calyx membrane. Endocytosis, is necessary to maintain the structure of the calyx and it is also necessary to form vesicles that will be filled with neurotransmitter for future exocytosis events. Capacitance recordings at the calyx of Held have made it possible to directly and rapidly measure vesicular release and subsequent endocytosis in a mammalian CNS nerve terminal. In addition, the corresponding postsynaptic activity can be simultaneously measured by using paired recordings. Thus a complete picture of the presynaptic and postsynaptic electrical activity at a central nervous system synapse is achievable using this preparation. Here, the methods for slice preparation, morphological features for identification of calyces of Held, basic patch clamping techniques, and examples of capacitance recordings to measure exocytosis and endocytosis are presented.

We demonstrate the basic techniques for presynaptic patch clamp recording at the calyx of Held, a mammalian central nervous system nerve terminal.

Méthodes pour les enregistrements patch clamp Capacité du calice

We demonstrate the basic techniques for presynaptic patch clamp recording at the calyx of Held, a mammalian central nervous system nerve terminal. ...

Recherche

Biologie

Pressure-polishing Pipettes for Improved Patch-clamp Recording

Pressure-polishing is a method for shaping glass pipettes for patch-clamp recording. We first developed this method for fabricating pipettes suitable for recording from small (&lt;3 m) neuronal cell bodies. The basic principal is similar to glass-blowing and combines air pressure and heat to modify the shape of patch pipettes prepared by a conventional micropipette puller. It can be applied to so-called soft (soda lime) and hard (borosilicate) glasses. Generally speaking, pressure polishing can reduce pipette resistance by 25% without decreasing the diameter of the tip opening (Goodman and Lockery, 2000). It can be applied to virtually any type of glass and requires only the addition of a high-pressure valve and fitting to a microforge. This technique is essential for recording from ultrasmall cells (&lt;5 m) and can also improve single-channel recording by minimizing pipette resistance. The blunt shape is also useful for perforated-patch clamp recording since this tip shape results in a larger membrane bleb available for perforation.

This is a guide to modifying the shape of glass micropipettes. Specifically, by using heat and air pressure the taper is widened without increasing the tip opening, leading to lower pipette resistance. This is critical to obtain low noise recordings of small cells but is useful in many applications.

Pression de polissage Pipettes Amélioration patch-clamp

Pressure-polishing is a method for shaping glass pipettes for patch-clamp recording.  We first developed this method for fabricating pipettes suitable for ...

Microinjection of Xenopus Laevis Oocytes

Microinjection of Xenopus laevis oocytes followed by thin-sectioning electron microscopy (EM) is an excellent system for studying nucleocytoplasmic transport. Because of its large nucleus and high density of nuclear pore complexes (NPCs), nuclear transport can be easily visualized in the Xenopus oocyte. Much insight into the mechanisms of nuclear import and export has been gained through use of this system (reviewed by Pant&eacute;, 2006). In addition, we have used microinjection of Xenopus oocytes to dissect the nuclear import pathways of several viruses that replicate in the host nucleus. 
Here we demonstrate the cytoplasmic microinjection of Xenopus oocytes with a nuclear import substrate. We also show preparation of the injected oocytes for visualization by thin-sectioning EM, including dissection, dehydration, and embedding of the oocytes into an epoxy embedding resin. Finally, we provide representative results for oocytes that have been microinjected with the capsid of the baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV) or the parvovirus Minute Virus of Mice (MVM), and discuss potential applications of the technique.

Here we demonstrate cytoplasmic microinjection of Xenopus laevis oocytes with a nuclear import substrate, as well as preparation of the injected oocytes for visualization by thin-sectioning electron microscopy.

Microinjection d&#39;ovocytes de Xenopus laevis

Microinjection of Xenopus laevis oocytes followed by thin-sectioning electron microscopy (EM) is an excellent system for studying nucleocytoplasmic ...

Visualizing RNA Localization in Xenopus Oocytes

RNA localization is a conserved mechanism of establishing cell polarity. Vg1 mRNA localizes to the vegetal pole of Xenopus laevis oocytes and acts to spatially restrict gene expression of Vg1 protein. Tight control of Vg1 distribution in this manner is required for proper germ layer specification in the developing embryo. RNA sequence elements in the 3' UTR of the mRNA, the Vg1 localization element (VLE) are required and sufficient to direct transport. To study the recognition and transport of Vg1 mRNA in vivo, we have developed an imaging technique that allows extensive analysis of trans-factor directed transport mechanisms via a simple visual readout. 
To visualize RNA localization, we synthesize fluorescently labeled VLE RNA and microinject this transcript into individual oocytes. After oocyte culture to allow transport of the injected RNA, oocytes are fixed and dehydrated prior to imaging by confocal microscopy. Visualization of mRNA localization patterns provides a readout for monitoring the complete pathway of RNA transport and for identifying roles in directing RNA transport for cis-acting elements within the transcript and trans-acting factors that bind to the VLE (Lewis et al., 2008, Messitt et al., 2008). We have extended this technique through co-localization with additional RNAs and proteins (Gagnon and Mowry, 2009, Messitt et al., 2008), and in combination with disruption of motor proteins and the cytoskeleton (Messitt et al., 2008) to probe mechanisms underlying mRNA localization.

Visualizing RNA Localization in Xenopus Oocytes

Visualization of in vivo RNA transport is accomplished by microinjection of fluorescently labeled RNA transcripts into Xenopus oocytes, followed by confocal microscopy.

Visualisation de localisation de l&#39;ARN Xenopus Les ovocytes

RNA localization is a conserved mechanism of establishing cell polarity.  Vg1 mRNA localizes to the vegetal pole of Xenopus laevis oocytes and acts to ...

Fertilization of Xenopus oocytes using the Host Transfer Method

Studying the contribution of maternally inherited molecules to vertebrate early development is often hampered by the time and expense necessary to generate maternal-effect mutant animals. Additionally, many of the techniques to overexpress or inhibit gene function in organisms such as Xenopus and zebrafish fail to sufficiently target critical maternal signaling pathways, such as Wnt signaling. In Xenopus, manipulating gene function in cultured oocytes and subsequently fertilizing them can ameliorate these problems to some extent. Oocytes are manually defolliculated from donor ovary tissue, injected or treated in culture as desired, and then stimulated with progesterone to induce maturation. Next, the oocytes are introduced into the body cavity of an ovulating host female frog, whereupon they will be translocated through the host's oviduct and acquire modifications and jelly coats necessary for fertilization. The resulting embryos can then be raised to the desired stage and analyzed for the effects of any experimental perturbations. This host-transfer method has been highly effective in uncovering basic mechanisms of early development and allows a wide range of experimental possibilities not available in any other vertebrate model organism.

Fertilization of Xenopus oocytes using the Host Transfer Method

Procedure for fertilizing Xenopus oocytes by the host transfer method.

La fertilisation des Ovocytes de Xenopus En utilisant la méthode de transfert d&#39;hôte

Studying the contribution of maternally inherited molecules to vertebrate early development is often hampered by the time and expense necessary to ...

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells

We will demonstrate how to study the functional effects of introducing a point mutation in an ion channel. We study G protein-gated inwardly rectifying potassium (referred to as GIRK) channels, which are important for regulating the excitability of neurons. There are four different mammalian GIRK channel subunits (GIRK1-GIRK4) - we focus on GIRK2 because it forms a homotetramer. Stimulation of different types of G protein-coupled receptors (GPCRs), such as the muscarinic receptor (M2R), leads to activation of GIRK channels. Alcohol also directly activates GIRK channels. We will show how to mutate one amino acid by specifically changing one or more nucleotides in the cDNA for the GIRK channel. This mutated cDNA sequence will be amplified in bacteria, purified, and the presence of the point mutation will be confirmed by DNA sequencing. The cDNAs for the mutated and wild-type GIRK channels will be transfected into human embryonic kidney HEK293T cells cultured in vitro. Lastly, whole-cell patch-clamp electrophysiology will be used to study the macroscopic potassium currents through the ectopically expressed wild-type or mutated GIRK channels. In this experiment, we will examine the effect of a L257W mutation in GIRK2 channels on M2R-dependent and alcohol-dependent activation.

We will demonstrate how to study the effect of a single point mutation on the function of an ion channel.

Mutagenèse et analyse fonctionnelle des canaux ioniques hétérologue exprimée dans les cellules de mammifères

We will demonstrate how to study the functional effects of introducing a point mutation in an ion channel. We study G protein-gated inwardly rectifying ...

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may also be used to study the structure-function relationship for other ion channels and neurotransmitter receptors1. BK channels are widely expressed in different tissues and have been implicated in many physiological functions, including regulation of smooth muscle contraction, frequency tuning of inner hair cells and regulation of neurotransmitter release2-6. BK channels are activated by membrane depolarization and by intracellular Ca2+ and Mg2+ 6-9. Therefore, the protocol is designed to control both the membrane voltage and the intracellular solution. In this protocol, messenger RNA of BK channels is injected into Xenopus laevis oocytes (stage V-VI) followed by 2-5 days of incubation at 18&deg;C10-13. Membrane patches that contain single or multiple BK channels are excised with the inside-out configuration using patch clamp techniques10-13. The intracellular side of the patch is perfused with desired solutions during recording so that the channel activation under different conditions can be examined. To summarize, the mRNA of BK channels is injected into Xenopus laevis oocytes to express channel proteins on the oocyte membrane; patch clamp techniques are used to record currents flowing through the channels under controlled voltage and intracellular solutions.

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

Ionic current of BK channels is recorded using patch clamp techniques. BK channels are expressed in Xenopus oocytes by injecting messenger RNA. The intracellular solution during patch clamp recordings is controlled by a perfusion system.

Patch Clamp et des techniques de perfusion pour étudier les canaux ioniques Exprimé en Xenopus Ovocytes

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may ...

Optimized Transfection Strategy for Expression and Electrophysiological Recording of Recombinant Voltage-Gated Ion Channels in HEK-293T Cells

The in vitro expression and electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T) is a ubiquitous research strategy. HEK-293T cells must be plated onto glass coverslips at low enough density so that they are not in contact with each other in order to allow for electrophysiological recording without confounding effects due to contact with adjacent cells. Transfected channels must also express with high efficiency at the plasma membrane for whole-cell patch clamp recording of detectable currents above noise levels. Heterologous ion channels often require long incubation periods at 28&deg;C after transfection in order to achieve adequate membrane expression, but there are increasing losses of cell-coverslip adhesion and membrane stability at this temperature. To circumvent this problem, we developed an optimized strategy to transfect and plate HEK-293T cells. This method requires that cells be transfected at a relatively high confluency, and incubated at 28&deg;C for varying incubation periods post-transfection to allow for adequate ion channel protein expression. Transfected cells are then plated onto glass coverslips and incubated at 37&deg;C for several hours, which allows for rigid cell attachment to the coverslips and membrane restabilization. Cells can be recorded shortly after plating, or can be transferred to 28&deg;C for further incubation. We find that the initial incubation at 28&deg;C, after transfection but before plating, is key for the efficient expression of heterologous ion channels that normally do not express well at the plasma membrane. Positively transfected, cultured cells are identified by co-expressed eGFP or eGFP expressed from a bicistronic vector (e.g. pIRES2-EGFP) containing the recombinant ion channel cDNA just upstream of an internal ribosome entry site and an eGFP coding sequence. Whole-cell patch clamp recording requires specialized equipment, plus the crafting of polished recording electrodes and L-shaped ground electrodes from borosilicate glass. Drug delivery to study the pharmacology of ion channels can be achieved by directly micropipetting drugs into the recording dish, or by using microperfusion or gravity flow systems that produce uninterrupted streams of drug solution over recorded cells.

Reliable method for highly efficient in vitro expression and subsequent electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T).

Stratégie de transfection optimisés pour l&#39;expression et l&#39;enregistrement électrophysiologique des recombinants canaux ioniques voltage-dépendants présents au HEK-293T

The in vitro expression and electrophysiological recording of recombinant voltage-gated ion channels in cultured human embryonic kidney cells (HEK-293T) ...

Giant Liposome Preparation for Imaging and Patch-Clamp Electrophysiology

The reconstitution of ion channels into chemically defined lipid membranes for electrophysiological recording has been a powerful technique to identify and explore the function of these important proteins. However, classical preparations, such as planar bilayers, limit the manipulations and experiments that can be performed on the reconstituted channel and its membrane environment. The more cell-like structure of giant liposomes permits traditional patch-clamp experiments without sacrificing control of the lipid environment.
Electroformation is an efficient mean to produce giant liposomes &gt;10 &mu;m in diameter which relies on the application of alternating voltage to a thin, ordered lipid film deposited on an electrode surface. However, since the classical protocol calls for the lipids to be deposited from organic solvents, it is not compatible with less robust membrane proteins like ion channels and must be modified. Recently, protocols have been developed to electroform giant liposomes from partially dehydrated small liposomes, which we have adapted to protein-containing liposomes in our laboratory.
We present here the background, equipment, techniques, and pitfalls of electroformation of giant liposomes from small liposome dispersions. We begin with the classic protocol, which should be mastered first before attempting the more challenging protocols that follow. We demonstrate the process of controlled partial dehydration of small liposomes using vapor equilibrium with saturated salt solutions. Finally, we demonstrate the process of electroformation itself. We will describe simple, inexpensive equipment that can be made in-house to produce high-quality liposomes, and describe visual inspection of the preparation at each stage to ensure the best results.

Reconstituting functional membrane proteins into giant liposomes of defined composition is a powerful approach when combined with patch-clamp electrophysiology. However, conventional giant liposome production may be incompatible with protein stability. We describe protocols for producing giant liposomes from pure lipids or small liposomes containing ion channels.

Préparation des liposomes de géant pour l&#39;imagerie et de patch-clamp électrophysiologie

The reconstitution of ion channels into chemically defined lipid membranes for electrophysiological recording has been a powerful technique to identify ...

The Xenopus Oocyte Cut-open Vaseline Gap Voltage-clamp Technique With Fluorometry

The cut-open oocyte Vaseline gap (COVG) voltage clamp technique allows for analysis of electrophysiological and kinetic properties of heterologous ion channels in oocytes. Recordings from the cut-open setup are particularly useful for resolving low magnitude gating currents, rapid ionic current activation, and deactivation. The main benefits over the two-electrode voltage clamp (TEVC) technique include increased clamp speed, improved signal-to-noise ratio, and the ability to modulate the intracellular and extracellular milieu.
Here, we employ the human cardiac sodium channel (hNaV1.5), expressed in Xenopus oocytes, to demonstrate the cut-open setup and protocol as well as modifications that are required to add voltage clamp fluorometry capability.
The properties of fast activating ion channels, such as hNaV1.5, cannot be fully resolved near room temperature using TEVC, in which the entirety of the oocyte membrane is clamped, making voltage control difficult. However, in the cut-open technique, isolation of only a small portion of the cell membrane allows for the rapid clamping required to accurately record fast kinetics while preventing channel run-down associated with patch clamp techniques.
In conjunction with the COVG technique, ion channel kinetics and electrophysiological properties can be further assayed by using voltage clamp fluorometry, where protein motion is tracked via cysteine conjugation of extracellularly applied fluorophores, insertion of genetically encoded fluorescent proteins, or the incorporation of unnatural amino acids into the region of interest1. This additional data yields kinetic information about voltage-dependent conformational rearrangements of the protein via changes in the microenvironment surrounding the fluorescent molecule.

The Xenopus Oocyte Cut-open Vaseline Gap Voltage-clamp Technique With Fluorometry

The cut-open Vaseline gap approach is used to obtain low noise recordings of ionic and gating currents from voltage-dependent ion channels expressed in Xenopus oocytes with high resolution of fast channel kinetics. With minor modification, voltage clamp fluorometry can be coupled to the cut-open oocyte protocol.

La<em&gt; Xenopus</em&gt; Ovocytes Cut-ouvert vaseline Gap voltage-clamp Technique Avec Fluorimétrie

The cut-open oocyte Vaseline gap (COVG) voltage clamp technique allows for analysis of electrophysiological and kinetic properties of heterologous ion ...