Wir danken Ihnen, Dr. Praveen Kumar in der Wittman Labor am UCSF für den Film von Aktin in HaCaT-Zellen.

1. Vorbereitung von Aktin Die Quelle von Aktin in diesem Test verwendet wurde non-muscle menschlichen Blutplättchen (β-Aktin) von Zytoskelett Inc. Stock Aliquots bei 10 mg / ml in der -70 ° C Gefrierschrank aufbewahrt erhalten. Für den Test wird die Aktin bis 0,4 mg / ml in einem Puffer, enthaltend 5 mM Tris pH 8, 0,2 mM CaCl 2, 0,2 mM ATP und 0,5 mM DTT, bei 20.000 g für 10 Minuten zentrifugiert bei 4 º C verdünnt Der Überstand, der monomeren Aktin ist bereit, polymerisiert werden. Aktin-Polymerisation wird durch Zugabe 50 mM KCl, 1 mM ATP und 2 mM MgCl 2 induziert. Die Polymerisation erfolgt bei Raumtemperatur für 1 Stunde. 2. Zubereitung von Protein- In diesem Test werden wir die Verwendung des C-Terminus von Talin, die als GST-markierte Protein wurde gereinigt. Das Protein im Assay verwendet werden soll, um eine Hochgeschwindigkeits-Zentrifugation vor, frei von Aggregaten vor der Inkubation mit F-Aktin unterzogen. Das Protein wird bei 100.000 g in einer Beckman-Ultrazentrifuge für 20 min bei 22 º C gesponnen 3. Aktin-Protein-Inkubation Der Betrag von Aktin und Protein in einem Test variieren. In diesem Beispiel verwenden wir Aktin im Übermaß. Normalerweise wird ein Molverhältnis berechnet, zB. einem 4:1 Molverhältnis von Aktin an Protein. In den folgenden Assay wird die Endreaktionsvolumen 150 pl. Der Puffer, in dem die Protein-und F-Aktin inkubiert wird das Protein getestet werden und auf die notwendigen Voraussetzungen abhängig. In diesem Beispiel verwenden wir einen Puffer mit 10 mM Tris pH 7,0, 1 mM ATP, 0,2 mM DTT, 1 mM EGTA, 0,1 mM CaCl 2 und 2 mM MgCl 2. Die Protein-und F-Aktin sind in den Puffer für 1 Stunde bei Raumtemperatur inkubiert. 4. Sedimentation von F-Aktin Nach der Inkubation werden die Proben bei 100.000 g bei 22 º C gesponnen Wir verwenden einen Beckman Ultrazentrifuge in dem Video. Der Rotor ist vorsichtig, um nicht auf die Pellets stören entfernt. 5. Analyse von Protein-Co-Sedimentation mit F-Aktin Die Überstände werden sorgfältig durch Pipettieren in ein Eppendorf-Röhrchen und 5 X Laemmli SDS-PAGE-Probenpuffer entfernt wird aufgenommen. Eine entsprechende Volumen von 1 X Laemmli SDS-PAGE-Probenpuffer ist es, die Pellets noch hinzu, pipettiert rauf und runter, und in neue Eppendorf-Röhrchen. Die relativen Mengen an Protein in den Pellets und Überstände werden nach ihrer Trennung durch SDS-PAGE und Coomassie-Blau-Färbung des Gels oder Western-Blot analysiert. Um die Spezifität der Protein-Interaktion mit Aktin zu bestimmen, Aktin abhängig von ihrer Konzentration co-Ablagerungen durchgeführt werden kann. Für diese Art von Experiment, eine feste Menge des Proteins und eine Reihe von steigenden Mengen an Aktin inkubiert, und die Analyse erfolgt wie oben beschrieben durchgeführt.

<ol>
	<li>Senetar, M. A., Foster, S. J., McCann, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrasteric+inhibition+mediates+the+interaction+of+the+I/LWEQ+module+proteins+Talin1,+Talin2,+Hip1,+and+Hip12+with+actin.">Intrasteric inhibition mediates the interaction of the I/LWEQ module proteins Talin1, Talin2, Hip1, and Hip12 with actin.</a> Biochemistry. 14, 15418-15428 (2004).</li><li>Goldmann, W. H., Hess, D., Isenberg, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+intact+talin+and+talin+tail+fragment+on+actin+filament+dynamics+and+structure+depends+on+pH+and+ionic+strength.">The effect of intact talin and talin tail fragment on actin filament dynamics and structure depends on pH and ionic strength.</a> Eur J Biochem. 260, 439-445 (1999).</li><li>Lee, H., Bellin, R. M., Walker, D. L., Patel, B., Powers, P., Liu, H., Garcia-Alvarez, B., de Pereda, J., Liddington, R. C., Volkmann, N., Hanein, D., Critchley, D. R., Robson, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+an+Actin-binding+Site+within+the+Talin+FERM+Domain.">Characterization of an Actin-binding Site within the Talin FERM Domain.</a> J Mol Biol. 22, 771-784 (2004).</li></ol>

Aktin co-Sedimentation ist ein einfaches in vitro-Assay zur specfic Proteine ​​die Bindung an F-Aktin zu analysieren. In diesem Video zeigen wir ein Beispiel, wie eine einfache Aktin co-Sedimentation durchgeführt werden kann. Wir zeigen, wie F-Aktin vorbereiten, bereiten das Protein getestet werden und das Verfahren von Aktin co-Sedimentation. Eine Reihe von Punkten zu beachten bei der Durchführung von Aktin-Co-Sedimentation Assays werden. Zum Beispiel kann der Puffer-Komponenten für die Inkubation je nach Protein getestet und pH-Wer...

actin co-sedimentation assay; for the analysis of protein binding to f-actin

Das Aktin-Zytoskelett in der Zelle ist ein Netzwerk von Aktin-Filamenten, die die Bewegung von Zellen und zelluläre Prozesse ermöglicht, und das erzeugt Spannung und hilft unterhält zelluläre Form. Obwohl das Aktin-Zytoskelett ist eine starre Struktur, es ist eine dynamische Struktur, die ständig Umbau ist. Eine Reihe von Proteinen, um das Aktin-Zytoskelett zu binden. Die Bindung eines bestimmten Proteins zu F-Aktin ist oft erwünscht, zellbiologische Beobachtungen stützen oder besser zu verstehen dynamische Prozesse wegen Umbau des Aktin-Zytoskeletts. Die Aktin-Co-Sedimentation Assay ist ein in-vitro-Test routinemäßig verwendet, um die Bindung spezifischer Proteine ​​oder Proteindomänen mit F-Aktin zu analysieren. Die grundlegenden Prinzipien des Tests beinhalten eine Inkubation des Proteins von Interesse (in voller Länge oder Domäne) mit F-Aktin, Ultrazentrifugationsschritt zu Pellets F-Aktin und Analyse des Proteins co-sedimentiert mit F-Aktin. Aktin co-Sedimentation Assays können entsprechend ausgelegt sein, um Aktin Bindungsaffinitäten und im Wettbewerb Assays messen.

Watch this Scientific Journal Video about Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin at JoVE.com

Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin

Proteine ​​binden an filamentösen Aktin (F-Aktin) durch verschiedene Aktin-bindende Module. In diesem Video zeigen wir das Verfahren von Aktin co-Sedimentation, die eine in vitro-Assay routinemäßig verwendet, um Proteine ​​oder bestimmte Domänen, die F-Aktin binden zu analysieren.

Aktin Co-Sedimentation Assay; für die Analyse von Protein-Bindung an F-Aktin

The actin cytoskeleton within the cell is a network of actin filaments that allows the movement of cells and cellular processes, and that generates ...

actin-co-sedimentation-assay-for-analysis-protein-binding-to-f

Research

JoVE Journal

Biology

19.3K Aufrufe.  University of California, San Francisco - UCSF. Proteine ​​binden an filamentösen Aktin (F-Aktin) durch verschiedene Aktin-bindende Module. In diesem Video zeigen wir das Verfahren von Aktin co-Sedimentation, die eine in vitro-Assay routinemäßig verwendet, um Proteine ​​oder bestimmte Domänen, die F-Aktin binden zu analysieren.

Serie: Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin

A Neuronal and Astrocyte Co-Culture Assay for High Content Analysis of Neurotoxicity

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing measurement of multiple cellular phenotypes within a single assay. In this study, we utilized HCA to develop a novel assay for neurotoxicity. Neurotoxicity assessment represents an important part of drug safety evaluation, as well as being a significant focus of environmental protection efforts. Additionally, neurotoxicity is also a well-accepted in vitro marker of the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Recently, the application of HCA to neuronal screening has been reported. By labeling neuronal cells with &beta;III-tubulin, HCA assays can provide high-throughput, non-subjective, quantitative measurements of parameters such as neuronal number, neurite count and neurite length, all of which can indicate neurotoxic effects. However, the role of astrocytes remains unexplored in these models. Astrocytes have an integral role in the maintenance of central nervous system (CNS) homeostasis, and are associated with both neuroprotection and neurodegradation when they are activated in response to toxic substances or disease states. GFAP is an intermediate filament protein expressed predominantly in the astrocytes of the CNS. Astrocytic activation (gliosis) leads to the upregulation of GFAP, commonly accompanied by astrocyte proliferation and hypertrophy. This process of reactive gliosis has been proposed as an early marker of damage to the nervous system. The traditional method for GFAP quantitation is by immunoassay. This approach is limited by an inability to provide information on cellular localization, morphology and cell number. We determined that HCA could be used to overcome these limitations and to simultaneously measure multiple features associated with gliosis - changes in GFAP expression, astrocyte hypertrophy, and astrocyte proliferation - within a single assay. In co-culture studies, astrocytes have been shown to protect neurons against several types of toxic insult and to critically influence neuronal survival. Recent studies have suggested that the use of astrocytes in an in vitro neurotoxicity test system may prove more relevant to human CNS structure and function than neuronal cells alone. Accordingly, we have developed an HCA assay for co-culture of neurons and astrocytes, comprised of protocols and validated, target-specific detection reagents for profiling &beta;III-tubulin and glial fibrillary acidic protein (GFAP). This assay enables simultaneous analysis of neurotoxicity, neurite outgrowth, gliosis, neuronal and astrocytic morphology and neuronal and astrocytic development in a wide variety of cellular models, representing a novel, non-subjective, high-throughput assay for neurotoxicity assessment. The assay holds great potential for enhanced detection of neurotoxicity and improved productivity in neuroscience research and drug discovery.

This article describes a novel protocol and reagent set designed for sensitive measurement of neurotoxic effects of compounds and treatments on co-cultures of neurons and astrocytes using high content analysis. Results demonstrate that high content analysis represents an exciting novel technology for neurotoxicity assessment.

Eine Neuronale und Astrocyte Co-Kultur-Assay für High Content Analyse der Neurotoxizität

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing ...

Forschung

Biologie

Detection of Protein Ubiquitination

Ubiquitination, the covalent attachment of the polypeptide ubiquitin to target proteins, is a key posttranslational modification carried out by a set of three enzymes. They include ubiquitin-activating enzyme E1, ubiquitin-conjugating enzyme E2, and ubiquitin ligase E3. Unlike to E1 and E2, E3 ubiquitin ligases display substrate specificity. On the other hand, numerous deubiquitylating enzymes have roles in processing polyubiquitinated proteins. Ubiquitination can result in change of protein stability, cellular localization, and biological activity. Mutations of genes involved in the ubiquitination/deubiquitination pathway or altered ubiquitin system function are associated with many different human diseases such as various types of cancer, neurodegeneration, and metabolic disorders. The detection of altered or normal ubiquitination of target proteins may provide a better understanding on the pathogenesis of these diseases. &nbsp;Here, we describe protocols to detect protein ubiquitination in cultured cells in vivo and test tubes in vitro. These protocols are also useful to detect other ubiquitin-like small molecule modification such as sumolyation and neddylation.

Ubiquitination is a key posttranslational modification carried out by a set of three enzymes. Mutations of genes involved in this modification are associated with many different human diseases. Here, we describe protocols to detect protein ubiquitination in cultured cells in vivo and test tubes in vitro.

Detektion von Protein Ubiquitination

Ubiquitination, the covalent attachment of the polypeptide ubiquitin to target proteins, is a key posttranslational modification carried out by a set of ...

Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy (FSM)

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique advantage of FSM is its ability to capture the movement and turnover kinetics (assembly/disassembly) of the F-actin network within living cells. This technique is particularly useful in deriving quantitative measurements of F-actin dynamics when paired with computer vision software (qFSM).  We describe  the selection, microinjection and visualization of fluorescent actin probes in living cells. Importantly, similar procedures are applicable to visualizing other macomolecular assemblies. FSM has been demonstrated for microtubules, intermediate filaments, and adhesion complexes.  

Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy FSM

Selection, microinjection, and imaging of fluorescently-labeled F-actin via fluorescent speckle microscopy (FSM).

Live Cell Imaging von F-Aktin Dynamics über Fluorescent Speckle Microscopy (FSM)

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique ...

Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based fractionation. The system is comprised of single-use, 8-sample capacity cartridges and a benchtop GELFREE Fractionation Instrument. During separation, a constant voltage is applied between the anode and cathode reservoirs, and each protein mixture is electrophoretically driven from a loading chamber into a specially designed gel column gel. Proteins are concentrated into a tight band in a stacking gel, and separated based on their respective electrophoretic mobilities in a resolving gel. As proteins elute from the column, they are trapped and concentrated in liquid phase in the collection chamber, free of the gel. The instrument is then paused at specific time intervals, and fractions are collected using a pipette. This process is repeated until all desired fractions have been collected. If fewer than 8 samples are run on a cartridge, any unused chambers can be used in subsequent separations.
This novel technology facilitates the quick and simple separation of up to 8 complex protein mixtures simultaneously, and offers several advantages when compared to previously available fractionation methods. This system is capable of fractionating up to 1mg of total protein per channel, for a total of 8mg per cartridge. Intact proteins over a broad mass range are separated on the basis of molecular weight, retaining important physiochemical properties of the analyte. The liquid phase entrapment provides for high recovery while eliminating the need for band or spot cutting, making the fractionation process highly reproducible1.

The accompanying video describes the use of the GELFREE 8100 Fractionation System, which partitions complex protein samples on the basis of molecular weight and recovers the fractions in liquid phase. The video describes how the technology works, how it is used, and provides resultant data, with polyacrylamide gel electrophoresis analysis of fractionated bovine liver homogenate.

Mit dem GELFREE 8100 Fraktionierung System für Molecular Weight-Based Fraktionierung mit Liquid Phase Wiederherstellung

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based ...

Linearization of the Bradford Protein Assay

Determination of microgram quantities of protein in the Bradford Coomassie brilliant blue assay is accomplished by measurement of absorbance at 590 nm. This most common assay enables rapid and simple protein quantification in cell lysates, cellular fractions, or recombinant protein samples, for the purpose of normalization of biochemical measurements. However, an intrinsic nonlinearity compromises the sensitivity and accuracy of this method. It is shown that under standard assay conditions, the ratio of the absorbance measurements at 590 nm and 450 nm is strictly linear with protein concentration. This simple procedure increases the accuracy and improves the sensitivity of the assay about 10-fold, permitting quantification down to 50 ng of bovine serum albumin. Furthermore, the interference commonly introduced by detergents that are used to create the cell lysates is greatly reduced by the new protocol. A linear equation developed on the basis of mass action and Beer's law perfectly fits the experimental data.

The accuracy and sensitivity of protein determination by the rapid and convenient Bradford assay is compromised by intrinsic nonlinearity. We show a simple linearization procedure that greatly increases the accuracy, improves the sensitivity of the assay about 10-fold, and significantly reduces interference by detergents.

Linearisierung der Bradford Protein Assay

Determination of microgram quantities of protein in the Bradford Coomassie brilliant blue assay is accomplished by measurement of absorbance at 590 nm. ...

PAR-CliP - A Method to Identify Transcriptome-wide the Binding Sites of RNA Binding Proteins

RNA transcripts are subjected to post-transcriptional gene regulation by interacting with hundreds of RNA-binding proteins (RBPs) and microRNA-containing ribonucleoprotein complexes (miRNPs) that are often expressed in a cell-type dependently. To understand how the interplay of these RNA-binding factors affects the regulation of individual transcripts, high resolution maps of in vivo protein-RNA interactions are necessary1.
A combination of genetic, biochemical and computational approaches are typically applied to identify RNA-RBP or RNA-RNP interactions. Microarray profiling of RNAs associated with immunopurified RBPs (RIP-Chip)2 defines targets at a transcriptome level, but its application is limited to the characterization of kinetically stable interactions and only in rare cases3,4 allows to identify the RBP recognition element (RRE) within the long target RNA. More direct RBP target site information is obtained by combining in vivo UV crosslinking5,6 with immunoprecipitation7-9 followed by the isolation of crosslinked RNA segments and cDNA sequencing (CLIP)10. CLIP was used to identify targets of a number of RBPs11-17. However, CLIP is limited by the low efficiency of UV 254 nm RNA-protein crosslinking, and the location of the crosslink is not readily identifiable within the sequenced crosslinked fragments, making it difficult to separate UV-crosslinked target RNA segments from background non-crosslinked RNA fragments also present in the sample.
We developed a powerful cell-based crosslinking approach to determine at high resolution and transcriptome-wide the binding sites of cellular RBPs and miRNPs that we term PAR-CliP (Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation) (see Fig. 1A for an outline of the method). The method relies on the incorporation of photoreactive ribonucleoside analogs, such as 4-thiouridine (4-SU) and 6-thioguanosine (6-SG) into nascent RNA transcripts by living cells. Irradiation of the cells by UV light of 365 nm induces efficient crosslinking of photoreactive nucleoside-labeled cellular RNAs to interacting RBPs. Immunoprecipitation of the RBP of interest is followed by isolation of the crosslinked and coimmunoprecipitated RNA. The isolated RNA is converted into a cDNA library and deep sequenced using Solexa technology. One characteristic feature of cDNA libraries prepared by PAR-CliP is that the precise position of crosslinking can be identified by mutations residing in the sequenced cDNA. When using 4-SU, crosslinked sequences thymidine to cytidine transition, whereas using 6-SG results in guanosine to adenosine mutations. The presence of the mutations in crosslinked sequences makes it possible to separate them from the background of sequences derived from abundant cellular RNAs.
Application of the method to a number of diverse RNA binding proteins was reported in Hafner et al.18

RNA transcripts are subject to extensive posttranscriptional regulation that is mediated by a multitude of trans-acting RNA-binding proteins (RBPs). Here we present a generalizable method to identify precisely and on a transcriptome-wide scale the RNA binding sites of RBPs.

PAR-Clip - Ein Verfahren zur Transkriptom-weiten die Bindungsstellen des RNA-bindende Proteine ​​Identifizieren

RNA transcripts are subjected to post-transcriptional gene regulation by interacting with hundreds of RNA-binding proteins (RBPs) and microRNA-containing ...

Study of the Actin Cytoskeleton in Live Endothelial Cells Expressing GFP-Actin

The microvascular endothelium plays an important role as a selectively permeable barrier to fluids and solutes. The adhesive junctions between endothelial cells regulate permeability of the endothelium, and many studies have indicated the important contribution of the actin cytoskeleton to determining junctional integrity1-5. A cortical actin belt is thought to be important for the maintenance of stable junctions1, 2, 4, 5. In contrast, actin stress fibers are thought to generate centripetal tension within endothelial cells that weakens junctions2-5. Much of this theory has been based on studies in which endothelial cells are treated with inflammatory mediators known to increase endothelial permeability, and then fixing the cells and labeling F-actin for microscopic observation. However, these studies provide a very limited understanding of the role of the actin cytoskeleton because images of fixed cells provide only snapshots in time with no information about the dynamics of actin structures5. 
Live-cell imaging allows incorporation of the dynamic nature of the actin cytoskeleton into the studies of the mechanisms determining endothelial barrier integrity. A major advantage of this method is that the impact of various inflammatory stimuli on actin structures in endothelial cells can be assessed in the same set of living cells before and after treatment, removing potential bias that may occur when observing fixed specimens. Human umbilical vein endothelial cells (HUVEC) are transfected with a GFP-&beta;-actin plasmid and grown to confluence on glass coverslips. Time-lapse images of GFP-actin in confluent HUVEC are captured before and after the addition of inflammatory mediators that elicit time-dependent changes in endothelial barrier integrity. These studies enable visual observation of the fluid sequence of changes in the actin cytoskeleton that contribute to endothelial barrier disruption and restoration. 
Our results consistently show local, actin-rich lamellipodia formation and turnover in endothelial cells. The formation and movement of actin stress fibers can also be observed. An analysis of the frequency of formation and turnover of the local lamellipodia, before and after treatment with inflammatory stimuli can be documented by kymograph analyses. These studies provide important information on the dynamic nature of the actin cytoskeleton in endothelial cells that can used to discover previously unidentified molecular mechanisms important for the maintenance of endothelial barrier integrity.

Microscopic imaging of live endothelial cells expressing GFP-actin allows characterization of dynamic changes in cytoskeletal structures. Unlike techniques that use fixed specimens, this method provides a detailed assessment of temporal changes in the actin cytoskeleton in the same cells before, during, and after various physical, pharmacological, or inflammatory stimuli.

Studie des Aktin-Zytoskeletts in Live Endothelial Cells, die GFP-Aktin

The microvascular endothelium plays an important role as a selectively permeable barrier to fluids and solutes. The adhesive junctions between endothelial ...

A Liquid Phase Affinity Capture Assay Using Magnetic Beads to Study Protein-Protein Interaction: The Poliovirus-Nanobody Example

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein labeled, this method can be implemented for the investigation of protein-protein interactions. It is based on one hand on the recognition of the tagged protein by cobalt coated magnetic beads and on the other hand on the interaction between the tagged protein and a second specific protein that is labeled. First, the labeled and tagged proteins are mixed and incubated at room temperature. The magnetic beads, that recognize the tag, are added and the bound fraction of labeled protein is separated from the unbound fraction using magnets. The amount of labeled protein that is captured can be determined in an indirect way by measuring the signal of the labeled protein remained in the unbound fraction. The described liquid phase affinity assay is extremely useful when conformational conversion sensitive proteins are assayed. The development and application of the assay is demonstrated for the interaction between poliovirus and poliovirus recognizing nanobodies1. Since poliovirus is sensitive to conformational conversion2 when attached to a solid surface (unpublished results), the use of ELISA is limited and a liquid phase based system should therefore be preferred. An example of a liquid phase based system often used in polioresearch3,4 is the micro protein A-immunoprecipitation test5. Even though this test has proven its applicability, it requires an Fc-structure, which is absent in the nanobodies6,7. However, as another opportunity, these interesting and stable single-domain antibodies8 can be easily engineered with different tags. The widely used (His)6-tag shows affinity for bivalent ions such as nickel or cobalt, which can on their turn be easily coated on magnetic beads. We therefore developed this simple quantitative affinity capture assay based on cobalt coated magnetic beads. Poliovirus was labeled with 35S to enable unhindered interaction with the nanobodies and to make a quantitative detection feasible. The method is easy to perform and can be established with a low cost, which is further supported by the possibility of effectively regenerating the magnetic beads.

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. It is a reliable technique based on the interaction between magnetic beads and tagged proteins (e.g. nanobodies) on one hand and the affinity between the tagged protein and a second, labeled protein (e.g. poliovirus) on the other.

Eine flüssige Phase Affinity Capture Assay Verwendung von magnetischen Kügelchen, um Protein-Protein Interaktion Studie: Das Poliovirus-Nanobody Beispiel

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein ...

A High Throughput MHC II Binding Assay for Quantitative Analysis of Peptide Epitopes

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or design1,2. Here, a peptide-MHC II binding assay is scaled to 384-well format. The scaled down protocol reduces reagent costs by 75% and is higher throughput than previously described 96-well protocols1,3-5. Specifically, the experimental design permits robust and reproducible analysis of up to 15 peptides against one MHC II allele per 384-well ELISA plate. Using a single liquid handling robot, this method allows one researcher to analyze approximately ninety test peptides in triplicate over a range of eight concentrations and four MHC II allele types in less than 48 hr. Others working in the fields of protein deimmunization or vaccine design and development may find the protocol to be useful in facilitating their own work. In particular, the step-by-step instructions and the visual format of JoVE should allow other users to quickly and easily establish this methodology in their own labs.

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or design. &#160;Here, a peptide-MHC II binding assay scaled to 384-well plates is described. This cost effective format should prove useful in the fields of protein deimmunization and vaccine design and development.

Ein hoher Durchsatz MHC II-Bindungsassay für die quantitative Analyse von Peptid-Epitope

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or ...

Reporter-based Growth Assay for Systematic Analysis of Protein Degradation

Protein degradation by the ubiquitin-proteasome system (UPS) is a major regulatory mechanism for protein homeostasis in all eukaryotes. The standard approach to determining intracellular protein degradation relies on biochemical assays for following the kinetics of protein decline. Such methods are often laborious and time consuming and therefore not amenable to experiments aimed at assessing multiple substrates and degradation conditions. As an alternative, cell growth-based assays have been developed, that are, in their conventional format, end-point assays that cannot quantitatively determine relative changes in protein levels.
Here we describe a method that faithfully determines changes in protein degradation rates by coupling them to yeast cell-growth kinetics. The method is based on an established selection system where uracil auxotrophy of URA3-deleted yeast cells is rescued by an exogenously expressed reporter protein, comprised of a fusion between the essential URA3 gene and a degradation determinant (degron). The reporter protein is designed so that its synthesis rate is constant whilst its degradation rate is determined by the degron. As cell growth in uracil-deficient medium is proportional to the relative levels of Ura3, growth kinetics are entirely dependent on the reporter protein degradation.
This method accurately measures changes in intracellular protein degradation kinetics. It was applied to: (a) Assessing the relative contribution of known ubiquitin-conjugating factors to proteolysis (b) E2 conjugating enzyme structure-function analyses (c) Identification and characterization of novel degrons. Application of the degron-URA3-based system transcends the protein degradation field, as it can also be adapted to monitoring changes of protein levels associated with functions of other cellular pathways.

Here we describe a robust biological assay for quantifying the relative rate of proteolysis by the ubiquitin-proteasome system. The assay readout is yeast growth rate in liquid culture, which is dependent on the cellular levels of a reporter protein comprising a degradation signal fused to an essential metabolic marker.

Reporter-basierten Wachstumstest für die systematische Analyse von Proteinabbau

Protein degradation by the ubiquitin-proteasome system (UPS) is a major regulatory mechanism for protein homeostasis in all eukaryotes. The standard ...

Methods Article

Aktin Co-Sedimentation Assay; für die Analyse von Protein-Bindung an F-Aktin