1. Preparação de soluções e materiais Estes passos devem ser realizados vários dias de antecedência. <ol><li> Lamínulas de vidro. Lamínulas foram limpos por imersão por 10 minutos em uma solução de detergente Linbro provêm 7X: água, misturados em um 1: 3 ratio e aquecida, com agitação, até claro. Lamínulas foram lavadas exaustivamente com água deionizada, e depois cozido a 450 ° C por 6 horas. Carregando lamínulas em racks coloração de cerâmica (veja Os reagentes) simplificou o processo. </li><li> Solução de proteína para carimbar. Fibronectina reconstituir seguir as instruções dos fabricantes para uma solução estoque de uma concentração mg / ml. </li></ol> 2. Elenco selos do mestre topológica Estes passos podem ser realizados vários dias de antecedência. Selos loja padrão-up em um prato coberto, como um prato de cultura de tecidos. <ol><li> Remover a poeira solta de mestre usando um fluxo de ar comprimido, ar filtrado ou gás inerte. </li><li> Coloque o mestre lado, modelado para cima, no fundo de um prato de plástico maior que o mestre. 60 - ou 100 mm de placas de cultura de tecidos são bem adaptados para esta finalidade. </li><li> Em um tubo de centrifugação de poliestireno de 50 ml, combine os componentes Sylgard na proporção de agente de cura: base de elastômero de 1: 10 por peso. Misturar bem utilizando um dispositivo de plástico, como uma pipeta descartável. Prepare pelo menos 0,2 ml de elastômero por centímetro quadrado de área prato. </li><li> Centrifugar o tubo de 50 ml a 300 G por 5 min para remover bolhas de ar. </li><li> Despeje o elastômero sobre o mestre, em seguida, coloque em um dessecador, sob vácuo, por 30 minutos. </li><li> Cura do elastômero em um forno a 65 ° C por pelo menos 2 horas. Cura em temperaturas mais altas e para resultados mais vezes em mais aguerrida elastômero. Deixe esfriar até a temperatura ambiente. </li><li> Separe a folha de selos do mestre. </li></ol> 3. Microcontact impressão de fibronectina em vidro <ol><li> Cortar um único carimbo. Carimbos medindo 4 mm x 4 mm a 1 cm X 1 cm de área e 1-2 mm de espessura são mais fáceis de começar. Coloque o lado padrão acima em uma lâmina de vidro ou prato de plástico. </li><li> Coloque selo em um aspirador de plasma, e processo, sob vácuo, por 30 segundos. A Harrick Científico limpo plasma (vide acessórios), fixado em sua configuração mais alta saída será tornar a superfície hidrofílica PDMS. Mais vezes resultar em quebra do elastômero. </li><li> Diluir a solução fibronectina com água deionizada a uma concentração de estampagem de 50 mcg / ml. </li><li> Coloque uma pequena gota (10-50 L) de estamparia solução no selo. Ele vai se espalhar por toda a superfície hidrofílica. Adicionar única solução o suficiente para que a queda cobre o selo, mas não é executado sobre as bordas. Vamos absorver proteína para carimbar por 5 minutos. </li><li> Usando um ® Kimwipe ou lenço de papel limpo outros, pavio a maior parte da solução de proteína do selo, sem tocar na região modelada. </li><li> Secar a solução restante do selo sob um fluxo de limpeza, gás seco e inerte, como nitrogênio. </li><li> Usando uma pinça, retire o selo da lâmina de vidro, invertido, e coloque em contato com a lamela de vidro limpo (a superfície a ser modelada). Coloque um peso em cima para promover um bom contato. O peso específico que fornece a melhor padronização é dependente do tamanho do selo e padrão; começar com um peso de 5 g, e ajuste entre peças estampadas. Deixe selo em contato com a superfície de um minuto. </li><li> Cuidadosamente desmontar a pilha, e carimbo separado lamela. </li><li> Vigorosamente lavar as lamelas padronizadas em PBS, seguido de água deionizada, para remover proteína que não é adsorvido à superfície. Lamela seco sob corrente de nitrogênio. </li></ol> Resultados representante Microcontact impressão é um processo poderoso para moléculas padronização em superfícies. Este processo tem a capacidade de criar recursos com dimensões variando de dezenas de micrômetros de centenas de nanômetros, na fig. 1A, o logos à esquerda estão cada 200 mM de altura, enquanto as manchas verdes ilustrado na figura. 1B são 1 m de diâmetro e espaçadas em intervalos de 4 M, medido de centro a centro. Fig. 1B também ilustra uma propriedade poderosa da impressão microcontact, ou seja, que ela é e processo aditivo. Várias rodadas de impressão microcontact pode ser aplicada a uma única superfície para criar sistemas multicomponentes 3. <img src="/files/ftp_upload/old/1065_2008_11_24_3/Figure_a.jpg" alt="Figura A" /><img src="/files/ftp_upload/old/1065_2008_11_24_4/FIGURE_B.jpg" alt="Figura B" />

<ol>
	<li>Chen, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Geometric+control+of+cell+life+and+death.">Geometric control of cell life and death.</a> Science. 276, 1425-1425 (1997).</li><li>Kumar, A., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Features+of+Gold+Having+Micrometer+to+Centimeter+Dimensions+can+be+Formed+Through+a+Combination+of+Stamping+with+an+Elastomeric+Stamp+and+an+Alkanethiol+"Ink"+Followed+by+Chemical+Etching.">Features of Gold Having Micrometer to Centimeter Dimensions can be Formed Through a Combination of Stamping with an Elastomeric Stamp and an Alkanethiol "Ink" Followed by Chemical Etching.</a> Applied Physics Letters. 63, 4-4 (1993).</li><li>St. John, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preferential+Glial+Cell+Attachment+to+Microcontact-printed+Surfaces.">Preferential Glial Cell Attachment to Microcontact-printed Surfaces.</a> Journal of Neuroscience Methods. 75, 171-171 (1997).</li><li>Kam, L., Boxer, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+adhesion+to+protein-micropatterned-supported+lipid+bilayer+membranes.">Cell adhesion to protein-micropatterned-supported lipid bilayer membranes.</a> Journal of Biomedical Materials Research. 55, 487-487 (2001).</li><li>Kung, L. A., Kam, L., Hovis, J. S., Boxer, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterning+Hybrid+Surfaces+of+Proteins+and+Supported+Lipid+Bilayers.">Patterning Hybrid Surfaces of Proteins and Supported Lipid Bilayers.</a> Langmuir. 16, 6773-6773 (2000).</li><li>Shen, K., Thomas, V. K., Dustin, M. L., Kam, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micropatterning+of+costimulatory+ligands+enhances+CD4++T+cell+function.">Micropatterning of costimulatory ligands enhances CD4+ T cell function.</a> Proceedings of the National Academy of Sciences. 105, 7791-7791 (2008).</li><li>Shi, P., Shen, K., Kam, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+presentation+of+L1+and+N-cadherin+in+multicomponent,+microscale+patterns+differentially+direct+neuron+function+in+vitro.">Local presentation of L1 and N-cadherin in multicomponent, microscale patterns differentially direct neuron function in vitro.</a> Developmental Neurobiology. 67, 1765-1765 (2007).</li></ol>

The authors have nothing to disclose.

O processo de impressão microcontact é conceitualmente simples e muito robusto, tendo sido aplicada a padronização uma ampla gama de moléculas em uma variedade de substratos. No entanto, este processo continua a ser algo de uma arte. A geometria específica do padrão a ser criada, a proteína a ser modelada, peso aplicado, e revestimento / condições stamping afetam a qualidade de estamparia. Por exemplo, muito pouco de peso, aplicada a características de grande porte, muitas vezes resulta em falhas no padrão de como pode ser visto...

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		<th>Catalogue Number</th>
		<th>Comment</th>
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<tr>
<td>Plasma Cleaner</td>
<td>&nbsp;</td>
<td>Harrick Scientific Products, Inc.</td>
<td>PDC-32G</td>
<td>&nbsp;</td>
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<td>Desiccator</td>
<td>&nbsp;</td>
<td>Nalgene</td>
<td>5315-0150</td>
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<td>PBS</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>10010-072</td>
<td>&nbsp;</td>
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<td>Protein labeling kit</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>A30006</td>
<td>&nbsp;</td>
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<td>Fibronectin </td>
<td>Reagent</td>
<td>Sigma-Aldrich</td>
<td>F2006</td>
<td>&nbsp;</td>
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<td>Staining rack</td>
<td>Reagent</td>
<td>Thomas Scientific</td>
<td>8542E40</td>
<td>&nbsp;</td>
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<td>Coverslips</td>
<td>Reagent</td>
<td>Fisher Scientific</td>
<td>12-544-12</td>
<td>&nbsp;</td>
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<td>Sylgard 184</td>
<td>Reagent</td>
<td>Ellsworth Adhesives</td>
<td>184 Sil Elast Kit</td>
<td>&nbsp;</td>
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<td>Diffraction Grating</td>
<td>Reagent</td>
<td>Edmund Scientific</td>
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microcontact printing of proteins for cell biology

A capacidade de proteínas e outras biomoléculas padrão sobre substratos é importante para captar a complexidade espacial do ambiente extracelular. Desenvolvimento da impressão microcontact pelo grupo Whitesides (<a href="http://gmwgroup.harvard.edu/"&gt; Http://gmwgroup.harvard.edu/</a&gt;), Em meados da década de 1990 revolutionalized neste campo, fazendo microeletrônica / técnicas de microfabricação acessível a laboratórios focados em ciências da vida. Implementações iniciais deste método utilizado PDMS (polidimetilsiloxano) selos para criar padrões de produtos químicos nas superfícies de materiais funcionalizados<sup&gt; 1</sup&gt;. Desde então, uma série de abordagens inovadoras foram desenvolvidos para moléculas de outro padrão, incluindo proteínas<sup&gt; 2</sup&gt;. Este vídeo demonstra o processo básico de criação de selos de PDMS e as utiliza para proteínas padrão, como estes passos são difíceis de expressar em palavras com precisão. Nós nos concentramos em padronização da proteína fibronectina da matriz extracelular sobre lamínulas de vidro como um exemplo específico de padronização. Um componente importante do processo de impressão microcontact é um mestre topológico, a partir do qual os selos são lançados; as regiões levantados e abaixados do mestre são espelhados no selo e definir o padrão final. Tipicamente, um mestre consiste em um wafer de silício revestido com fotorresiste e depois modelado por fotolitografia como é feito aqui. Criação de mestres contendo um padrão específico requer equipamento especializado, e é melhor abordado em consulta com um centro de fabricação ou instalação. No entanto, quase todos os suportes com a topologia pode ser usado como um mestre, como redes de difração de plástico (ver Reagentes para um exemplo), e tais mestres serendipitous fornecer prontamente disponíveis, os padrões simples. Este protocolo começa no ponto de ter um mestre na mão.

Watch this Scientific Journal Video about Microcontact Printing of Proteins for Cell Biology at JoVE.com

Microcontact Printing of Proteins for Cell Biology

Microcontact impressão é usado extensivamente às proteínas padrão e outras moléculas nas superfícies de materiais. Demonstramos as etapas básicas desse processo, carimbar padrões de fibronectina em vidro.

Impressão microcontact de Proteínas de Biologia Celular

The ability to pattern proteins and other biomolecules onto substrates is important for capturing the spatial complexity of the extracellular environment. ...

microcontact-printing-of-proteins-for-cell-biology

Research

JoVE Journal

Biology

19.9K visualizações.  Columbia University. Microcontact impressão é usado extensivamente às proteínas padrão e outras moléculas nas superfícies de materiais. Demonstramos as etapas básicas desse processo, carimbar padrões de fibronectina em vidro.

Vídeo: Microcontact Printing of Proteins for Cell Biology

A Gradient-generating Microfluidic Device for Cell Biology

 The fabrication and operation of a gradient-generating microfluidic device for studying cellular behavior is described.  A microfluidic platform is an enabling experimental tool, because it can precisely manipulate fluid flows, enable high-throughput experiments, and generate stable soluble concentration gradients.  Compared to conventional gradient generators, poly(dimethylsiloxane) (PDMS)-based  microfluidic devices can generate stable concentration gradients of growth factors with well-defined profiles.  Here, we developed simple gradient-generating microfluidic devices with three separate inlets.  Three microchannels combined into one microchannel to generate concentration gradients.  The stability and shape of growth factor gradients were confirmed by fluorescein isothyiocyanate (FITC)-dextran with a molecular weight similar to epidermal growth factor (EGF).  Using this microfluidic device, we demonstrated that fibroblasts exposed to concentration gradients of EGF migrated toward higher concentrations.  The directional orientation of cell migration and motility of migrating cells were quantitatively assessed by cell tracking analysis.  Thus, this gradient-generating microfluidic device might be useful for studying and analyzing the behavior of migrating cells.

We describe a protocol for the microfabrication of the gradient-generating microfluidic device that can generate spatial and temporal gradients in well-defined microenvironment. In this approach, the gradient-generating microfluidic device can be used to study directed cell migration, embryogenesis, wound healing, and cancer metastasis.

Um dispositivo de geração de Gradient microfluídicos de Biologia Celular

 The fabrication and operation of a gradient-generating microfluidic device for studying cellular behavior is described.  A microfluidic platform is an ...

Biologia

Micro-scale Engineering for Cell Biology

Micro-escala de Engenharia de Biologia Celular

Assessing Two-dimensional Crystallization Trials of Small Membrane Proteins for Structural Biology Studies by Electron Crystallography

Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray crystallography to study structure-function questions of membrane proteins, as well as soluble proteins. Screening for two-dimensional (2D) crystals by transmission electron microscopy (EM) is the critical step in finding, optimizing, and selecting samples for high-resolution data collection by cryo-EM. Here we describe the fundamental steps in identifying both large and ordered, as well as small 2D arrays, that can potentially supply critical information for optimization of crystallization conditions.
By working with different magnifications at the EM, data on a range of critical parameters is obtained. Lower magnification supplies valuable data on the morphology and membrane size. At higher magnifications, possible order and 2D crystal dimensions are determined. In this context, it is described how CCD cameras and online-Fourier Transforms are used at higher magnifications to assess proteoliposomes for order and size.
While 2D crystals of membrane proteins are most commonly grown by reconstitution by dialysis, the screening technique is equally applicable for crystals produced with the help of monolayers, native 2D crystals, and ordered arrays of soluble proteins. In addition, the methods described here are applicable to the screening for 2D crystals of even smaller as well as larger membrane proteins, where smaller proteins require the same amount of care in identification as our examples and the lattice of larger proteins might be more easily identifiable at earlier stages of the screening.

Evaluating two-dimensional (2D) crystallization trials for the formation of ordered membrane protein arrays is a highly critical and difficult task in electron crystallography. Here we describe our approach in screening for and identifying 2D crystals of predominantly small membrane proteins in the range of 15 &#x2013; 90kDa.

Avaliar Trials bidimensional cristalização de proteínas da membrana Pequenas de Estudos Biologia Estrutural por Cristalografia Electron

Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray ...

Fluorescent Labeling of COS-7 Expressing SNAP-tag Fusion Proteins for Live Cell Imaging

SNAP-tag and CLIP-tag protein labeling systems enable the specific, covalent attachment of molecules, including fluorescent dyes, to a protein of interest in live cells. These systems offer a broad selection of fluorescent substrates optimized for a range of imaging instrumentation. Once cloned and expressed, the tagged protein can be used with a variety of substrates for numerous downstream applications without having to clone again. There are two steps to using this system: cloning and expression of the protein of interest as a SNAP-tag fusion, and labeling of the fusion with the SNAP-tag substrate of choice. The SNAP-tag is a small protein based on human O6-alkylguanine-DNA-alkyltransferase (hAGT), a DNA repair protein. SNAP-tag labels are dyes conjugated to guanine or chloropyrimidine leaving groups via a benzyl linker. In the labeling reaction, the substituted benzyl group of the substrate is covalently attached to the SNAP-tag. CLIP-tag is a modified version of SNAP-tag, engineered to react with benzylcytosine rather than benzylguanine derivatives. When used in conjunction with SNAP-tag, CLIP-tag enables the orthogonal and complementary labeling of two proteins simultaneously in the same cells.

SNAP-tag and CLIP-tag protein labeling systems enable the specific, covalent attachment of molecules, including fluorescent dyes, to a protein of interest in live cells. Once cloned and expressed, the tagged protein can be used with a variety of substrates for numerous downstream applications without having to clone again.

Labeling fluorescentes de COS-7 expressando as proteínas SNAP tag-Fusion para imagens de células vivas

SNAP-tag and CLIP-tag protein labeling systems enable the specific, covalent attachment of molecules, including fluorescent dyes, to a protein of interest ...

Protein Membrane Overlay Assay: A Protocol to Test Interaction Between Soluble and Insoluble Proteins in vitro

Validating interactions between different proteins is vital for investigation of their biological functions on the molecular level. There are several methods, both in vitro and in vivo, to evaluate protein binding, and at least two methods that complement the shortcomings of each other should be conducted to obtain reliable insights. 
For an in vivo assay, the bimolecular fluorescence complementation (BiFC) assay represents the most popular and least invasive approach that enables to detect protein-protein interaction within living cells, as well as identify the intracellular localization of the interacting proteins 1,2. In this assay, non-fluorescent N- and C-terminal halves of GFP or its variants are fused to tested proteins, and when the two fusion proteins are brought together due to the tested proteins&#x2019; interactions, the fluorescent signal is reconstituted3-6. Because its signal is readily detectable by epifluorescence or confocal microscopy, BiFC has emerged as a powerful tool of choice among cell biologists for studying about protein-protein interactions in living cells 3. This assay, however, can sometimes produce false positive results. For example, the fluorescent signal can be reconstituted by two GFP fragments arranged as far as 7 nm from each other due to close packing in a small subcellular compartment, rather that due to specific interactions7.
Due to these limitations, the results obtained from live cell imaging technologies should be confirmed by an independent approach based on a different principle for detecting protein interactions. Co-immunoprecipitation (Co-IP) or glutathione transferase (GST) pull-down assays represent such alternative methods that are commonly used to analyze protein-protein interactions in vitro. However, iIn these assays, however, the tested proteins must be readily soluble in the buffer that supportsused for the binding reaction. Therefore, specific interactions involving an insoluble protein cannot be assessed by these techniques.
 Here, we illustrate the protocol for the protein membrane overlay binding assay, which circumvents this difficulty. In this technique, interaction between soluble and insoluble proteins can be reliably tested because one of the proteins is immobilized on a membrane matrix. This method, in combination with in vivo experiments, such as BiFC, provides a reliable approach to investigate and characterize interactions faithfully between soluble and insoluble proteins. In this article, binding between Tobacco mosaic virus (TMV) movement protein (MP), which exerts multiple functions during viral cell-to-cell transport8-14, and a recently identified plant cellular interactor, tobacco ankyrin repeat-containing protein (ANK) 15, is demonstrated using this technique.

Protein Membrane Overlay Assay: A Protocol to Test Interaction Between Soluble and Insoluble Proteins in vitro

Testing protein-protein interaction is indispensable for dissection of protein functionality. Here, we introduce an in vitro protein-protein binding assay to probe a membrane-immobilized protein with a soluble protein. This assay provides a reliable method to test interaction between an insoluble protein and a protein in solution.

Protein Assay Overlay membrana: um protocolo para testar Interação entre proteínas solúveis e insolúveis In vitro</em

Validating interactions between different proteins is vital for investigation of their biological functions on the molecular level.  There are several ...

Pull-down of Calmodulin-binding Proteins

Calcium (Ca2+) is an ion vital in regulating cellular function through a variety of mechanisms. Much of Ca2+ signaling is mediated through the calcium-binding protein known as calmodulin (CaM)1,2. CaM is involved at multiple levels in almost all cellular processes, including apoptosis, metabolism, smooth muscle contraction, synaptic plasticity, nerve growth, inflammation and the immune response. A number of proteins help regulate these pathways through their interaction with CaM. Many of these interactions depend on the conformation of CaM, which is distinctly different when bound to Ca2+ (Ca2+-CaM) as opposed to its Ca2+-free state (ApoCaM)3.
While most target proteins bind Ca2+-CaM, certain proteins only bind to ApoCaM. Some bind CaM through their IQ-domain, including neuromodulin4, neurogranin (Ng)5, and certain myosins6. These proteins have been shown to play important roles in presynaptic function7, postsynaptic function8, and muscle contraction9, respectively. Their ability to bind and release CaM in the absence or presence of Ca2+ is pivotal in their function. In contrast, many proteins only bind Ca2+-CaM and require this binding for their activation. Examples include myosin light chain kinase10, Ca2+/CaM-dependent kinases (CaMKs)11 and phosphatases (e.g. calcineurin)12, and spectrin kinase13, which have a variety of direct and downstream effects14.
The effects of these proteins on cellular function are often dependent on their ability to bind to CaM in a Ca2+-dependent manner. For example, we tested the relevance of Ng-CaM binding in synaptic function and how different mutations affect this binding. We generated a GFP-tagged Ng construct with specific mutations in the IQ-domain that would change the ability of Ng to bind CaM in a Ca2+-dependent manner. The study of these different mutations gave us great insight into important processes involved in synaptic function8,15. However, in such studies, it is essential to demonstrate that the mutated proteins have the expected altered binding to CaM.
Here, we present a method for testing the ability of proteins to bind to CaM in the presence or absence of Ca2+, using CaMKII and Ng as examples. This method is a form of affinity chromatography referred to as a CaM pull-down assay. It uses CaM-Sepharose beads to test proteins that bind to CaM and the influence of Ca2+ on this binding. It is considerably more time efficient and requires less protein relative to column chromatography and other assays. Altogether, this provides a valuable tool to explore Ca2+/CaM signaling and proteins that interact with CaM.

Calmodulin (CaM) pull-down assay is an effective way to investigate the interaction of CaM with various proteins. This method uses CaM-sepharose beads for efficient and specific analysis of CaM-binding proteins. This provides an important tool to explore CaM signaling in cellular function.

Pull-down da Calmodulina Proteínas de Ligação

Calcium (Ca2+) is an ion vital in regulating cellular function through a variety of mechanisms. Much of Ca2+ signaling is mediated through the ...

Modified Yeast-Two-Hybrid System to Identify Proteins Interacting with the Growth Factor Progranulin

Progranulin (PGRN), also known as granulin epithelin precursor (GEP), is a 593-amino-acid autocrine growth factor. PGRN is known to play a critical role in a variety of physiologic and disease processes, including early embryogenesis, wound healing 1, inflammation 2, 3, and host defense 4. PGRN also functions as a neurotrophic factor 5, and mutations in the PGRN gene resulting in partial loss of the PGRN protein cause frontotemporal dementia 6, 7. Our recent studies have led to the isolation of PGRN as an important regulator of cartilage development and degradation 8-11. Although PGRN, discovered nearly two decades ago, plays crucial roles in multiple physiological and pathological conditions, efforts to exploit the actions of PGRN and understand the mechanisms involved have been significantly hampered by our inability to identify its binding receptor(s). To address this issue, we developed a modified yeast two-hybrid (MY2H) approach based on the most commonly used GAL4 based 2-hybrid system. Compared with the conventional yeast two-hybrid screen, MY2H dramatically shortens the screen process and reduces the number of false positive clones. In addition, this approach is reproducible and reliable, and we have successfully employed this system in isolating the binding proteins of various baits, including ion channel 12, extracellular matrix protein 10, 13, and growth factor14. In this paper, we describe this MY2H experimental procedure in detail using PGRN as an example that led to the identification of TNFR2 as the first known PGRN-associated receptor 14, 15.

We have modified the conventional yeast two-hybrid screening, an effective genetic tool in identifying protein interaction. This modification markedly shortens the process, reduces the workload, and most importantly, reduces the number of false positives. In addition, this approach is reproducible and reliable.

Modificado Sistema Yeast-Two-Hybrid para identificar proteínas Interagindo com o Fator de Crescimento progranulina

Progranulin (PGRN), also known as granulin epithelin precursor (GEP), is a 593-amino-acid autocrine growth factor. PGRN is known to play a critical role ...

Cell Tracking Using Photoconvertible Proteins During Zebrafish Development

Embryogenesis is a dynamic process that is best studied by using techniques that allow the documentation of developmental changes in vivo. The use of genetically-encoded fluorescent proteins has proven a valuable strategy for elucidating dynamic morphogenetic processes as they occur in the intact organism. During the past decade, the development of photoactivatable and photoconvertible fluorescent proteins has opened the possibility to investigate the fate of discrete subpopulations of tagged proteins1. Unlike photoactivatable proteins, photoconvertible fluorescent proteins (PCFPs) are readily tracked and imaged in their native emission state prior to photoconversion, making it easier to identify and select regions by optical inspection. PCFPs, such as Kaede2, KikGR3, Dendra4 and EosFP5, can be shifted from green to red upon exposure to UV or blue light due to a His-Tyr-Gly tripeptide sequence which forms a green chromophore that can be photoconverted to a red one by a light-catalyzed &beta;-elimination and subsequent extension of a &pi;-conjugated system3. PCFPs and their monomeric variants are useful tools for tracking cells6-10 and studying protein dynamics11-14, respectively. During recent years, PCFPs have been expressed in different animal model, such as zebrafish6, chicken7,8 and mouse9,10 for cell fate tracking. Here we report a protocol for cell-specific photoconversion of PCFPs in the living zebrafish embryo and further tracking of photoconverted proteins at later developmental stages. This methodology allows studying, in a tissue-specific manner, cell biological events underlying morphogenesis in the zebrafish animal model.

Here, we present a method for the photoactivated switch of photoconvertible fluorescent proteins (PCFPs) in the living zebrafish embryo and further tracking of photoconverted protein at specific time points during development. This methodology allows monitoring of cell biological events underlying different developmental processes in a live vertebrate organism.

Rastreamento de celular utilizando proteínas Photoconvertible Durante o Desenvolvimento Zebrafish

Embryogenesis is a dynamic process that is best studied by using techniques that allow the documentation of developmental changes in vivo. The use of ...

The Use of Chemostats in Microbial Systems Biology

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated including macromolecular synthesis, metabolism and ultimately, commitment to the cell division cycle. The chemostat, a method of experimentally controlling cell growth rate, provides a powerful means of systematically studying how growth rate impacts cellular processes - including gene expression and metabolism - and the regulatory networks that control the rate of cell growth. When maintained for hundreds of generations chemostats can be used to study adaptive evolution of microbes in environmental conditions that limit cell growth. We describe the principle of chemostat cultures, demonstrate their operation and provide examples of their various applications. Following a period of disuse after their introduction in the middle of the twentieth century, the convergence of genome-scale methodologies with a renewed interest in the regulation of cell growth and the molecular basis of adaptive evolution is stimulating a renaissance in the use of chemostats in biological research.

Cell growth rate is a regulated process and a primary determinant of cell physiology. Continuous culturing using chemostats enables extrinsic control of cell growth rate by nutrient limitation facilitating the study of molecular networks that control cell growth and how those networks evolve to optimize cell growth.

O Uso de quimiostatos em Microbial Biologia de Sistemas

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated ...

Protocols for Implementing an Escherichia coli Based TX-TL Cell-Free Expression System for Synthetic Biology

Ideal cell-free expression systems can theoretically emulate an in vivo cellular environment in a controlled in vitro platform.1 This is useful for expressing proteins and genetic circuits in a controlled manner as well as for providing a prototyping environment for synthetic biology.2,3 To achieve the latter goal, cell-free expression systems that preserve endogenous Escherichia coli transcription-translation mechanisms are able to more accurately reflect in vivo cellular dynamics than those based on T7 RNA polymerase transcription. We describe the preparation and execution of an efficient endogenous E. coli based transcription-translation (TX-TL) cell-free expression system that can produce equivalent amounts of protein as T7-based systems at a 98% cost reduction to similar commercial systems.4,5 The preparation of buffers and crude cell extract are described, as well as the execution of a three tube TX-TL reaction. The entire protocol takes five days to prepare and yields enough material for up to 3000 single reactions in one preparation. Once prepared, each reaction takes under 8 hr from setup to data collection and analysis. Mechanisms of regulation and transcription exogenous to E. coli, such as lac/tet repressors and T7 RNA polymerase, can be supplemented.6 Endogenous properties, such as mRNA and DNA degradation rates, can also be adjusted.7 The TX-TL cell-free expression system has been demonstrated for large-scale circuit assembly, exploring biological phenomena, and expression of proteins under both T7- and endogenous promoters.6,8 Accompanying mathematical models are available.9,10 The resulting system has unique applications in synthetic biology as a prototyping environment, or "TX-TL biomolecular breadboard."

Protocols for Implementing an Escherichia coli Based TX-TL Cell-Free Expression System for Synthetic Biology

This five-day protocol outlines all steps, equipment, and supplemental software necessary for creating and running an efficient endogenous Escherichia coli based TX-TL cell-free expression system from scratch. With reagents, the protocol takes 8 hours or less to setup a reaction, collect, and process data.

Protocolos para implementação de uma<em&gt; Escherichia coli</em&gt; Com base TX-TL Expression System-Free Cell para Biologia Sintética

Ideal cell-free expression systems can theoretically emulate an in vivo cellular environment in a controlled in vitro platform.1 This is useful for ...