Agradecemos a Oliver Brüstle e todos os membros do Grupo de Engenharia de Células-Tronco da Universidade de Bonn, de apoio e valiosas discussões. Agradecemos a Sabine Schenk para a preparação do SDS-PAGE e apoio permanente ao longo do projeto. Nicole Russ e Anna Magerhans prestou apoio técnico excelente. Além disso, gostaríamos de agradecer a Andreas Bär e Sheila Mertens para a produção do filme. Este trabalho foi financiado por doações da Fundação Volkswagen (Az I/77864) eo Ministério Alemão de Educação e Pesquisa (BMBF, 01 GN 0813).

Construção de vetor de expressão e de expressão: O vetor de expressão pSESAME-Cre foi construído através da inserção de um fragmento de Cre-codificação em pSESAME através de sites e AvrII NheI restrição utilizando os métodos de clonagem padrão. pSESAME codifica uma proteína de fusão que consiste de uma tag histidina, TAT-domínio, a seqüência NLS e Cre, abreviado HTNCre. À manifestação de HTNCre o pSESAME-Cre foi transformado em TUNER (DE3) pLacI e usado para preparar um estoque de glicerol. <ol><li> Uma cultura de over-noite, foi inoculado com uma ponta de pipeta revestidos com bactérias transformadas a partir do estoque de glicerol. A cultura noite mais consistia em media LB suplementado com glicose 0,5% [v / v] e carbenicilina numa concentração final de 50 mcg / mL e foi autorizado a crescer a 37 ° C por 16 horas. </li><li> Dia seguinte, a densamente cresceu durante a noite de cultura foi usada para inocular a cultura de expressão na proporção de 1 a 40 e foi colocado em uma incubadora a 37 ° C. Cultura consistia expressão dos meios de comunicação TB suplementado com glicose 0,5% [v / v] e ampicilina na concentração final de 100 mcg / mL. </li><li> Em um OD 595 de 1,5 a cultura expressão foi induzida com IPTG 0,5 mM por 1 h. </li><li> Posteriormente as bactérias foram coletadas por centrifugação a 5000 rpm por 10 minutos em um rotor SLA3000. </li><li> Pellets bactérias foram armazenadas a -20 ° C até a purificação. </li></ol> Purificação de proteínas de células-permeável: <ol><li> Pellets congelados bactérias foram ressuspendidas em 10 mL tampão de lise por cultura frasco litro por 15 minutos em temperatura ambiente. </li><li> Suspensão foi, então, incubadas com lisozima 1 mg / mL para o adicional de 15 minutos, enquanto a mistura em temperatura ambiente. </li><li> 25 U / mL benzonase foi adicionado depois e incubados durante a mistura por 15 minutos em temperatura ambiente. </li><li> Depois de sonorização no gelo por 1,5 min com 0,5 pulsos s em 45% do poder, 1 mL de buffer sal fria tartárico (TSB) por mL de suspensão foi cuidadosamente adicionado durante a mistura e incubado por 5 min no gelo. SDS-PAGE da amostra da fração lisado (L) foi tirada. </li><li> Lisado limpo foi obtida por centrifugação a 4 ° C por 30 min a 30.000 g. SDS-PAGE de amostras das frações solúvel (S) e insolúvel (I) foram tomadas. </li><li> O sobrenadante foi transferido para novos tubos de 50 mL falcon e foi então delicadamente misturados por 1 hora a 4 ° C com 2 mL de 50% Ni-NTA suspensão por litro de cultura expressão inicial. </li><li> A suspensão foi embalado em um fluxo de gravidade coluna EconoPac (SDS-PAGE amostra de fluxo através fração (FT) foi tomada) e lavadas duas vezes com 5 leitos volumes de tampão de lavagem. SDS-PAGE de amostras de ambas as frações de lavagem (W1 e W2) foram coletados. </li><li> HTNCre contendo frações foram eluídas com três cama-volumes de tampão de eluição e amostra da fração eluato (E) para análise de SDS-PAGE foi tirada. </li><li> Imidazol foi removido por diálise contra tampão de eluição fração elevada de sal duas vezes. </li><li> A solução de proteína foi ainda mais concentrada por diálise contra tampão glicerol duas vezes. Em todas as etapas de diálise a relação de tampão para amostra foi de pelo menos 50. Este procedimento resultou em uma solução estoque contendo glicerol HTNCre na concentração usual entre 200 e 450 mM, ou seja, 1 litro de cultura expressão resultará em ~ 12 mg de proteína. Amostra de estoque de glicerol (GS) para SDS-PAGE análise foi coletado. HTNCre solução estoque pode ser armazenado a menos 20 ° C. </li></ol><img border="0" src="/files/ftp_upload/1627/1627fig1tmb.jpg" alt="Figura 1" /> Figura 1: SDS-PAGE análise das amostras coletadas durante o processo de purificação da Cre recombinase. Indução da expressão do Cre é indicado por banda dominante na fração de lisado. Embora uma parte da proteína é insolúvel da proteína Cre pode ser enriquecido como visto no eluato e frações de ações glicerol. L: Lysate, I: Insolúvel, S: O sobrenadante, FT: Flow-through, W: E lavar roupa,: eluato, GS: Stock Gylcerol. Por favor, <a href="https://www.jove.com/files/ftp_upload/1627/1627fig1.jpg">clique aqui</a> para ver uma versão ampliada da figura 1. Transdução de proteína em camundongos-tronco embrionárias (ES) células: <ol><li> Células ES carregando uma condicional β-Galactosidase repórter construir cinco foram semeadas como células isoladas usando TrypLE ™ Express para a dissociação de células aderentes. Após 4 a 6 horas as células tinham re-inscritos e meio foi removido. </li><li> Posteriormente as células ES foram incubadas com HTNCre meio contendo por 16 horas. <ul><li> Uma quantidade adequada de proteína HTNCre (correspondente a 10 mM) do estoque de glicerol foi diluído em meio ES e posteriormente filtrado estéril (0,22 m). </li></ul></li><li> Depois de meio de transdução de proteína foi alterado novamente para meio de crescimento normal. </li><li> Depois de dois dias as células foram lavadas com PBS e fixadas com paraformaldeído 4% (PFA) por 10 minutos. </li><li> Dois aditradicionais etapas de lavagem com PBS foram executados antes de X-Gal coloração foi realizada. </li><li> Células fixadas foram cobertos com uma camada de X-Gal solução de coloração 6 e incubadas durante a noite a 37 ° C. </li></ol> Resultados representativos: No dia seguinte solução de coloração X-Gal foi aspirado e as células foram cobertos com uma camada de PBS para a análise de microscopia. 8-10% das células recombinadas pôde ser observado no interior das células ES de camundongos julgado por β-Galactosidase atividade.

<ol>
	<li>Gump, J. M., Dowdy, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TAT+transduction:+the+molecular+mechanism+and+therapeutic+prospects.">TAT transduction: the molecular mechanism and therapeutic prospects.</a> Trends Mol Med. 13 (10), 443-448 (2007).</li><li>Edenhofer, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+transduction+revisited:+novel+insights+into+the+mechanism+underlying+intracellular+delivery+of+proteins.">Protein transduction revisited: novel insights into the mechanism underlying intracellular delivery of proteins.</a> Curr Pharm Des. 14 (34), 3628-3636 (2008).</li><li>Branda, C. S., Dymecki, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Talking+about+a+revolution:+The+impact+of+site-specific+recombinases+on+genetic+analyses+in+mice.">Talking about a revolution: The impact of site-specific recombinases on genetic analyses in mice.</a> Dev Cell. 6 (1), 7-28 (2004).</li><li>Nolden, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Site-specific+recombination+in+human+embryonic+stem+cells+induced+by+cell-permeant+Cre+recombinase.">Site-specific recombination in human embryonic stem cells induced by cell-permeant Cre recombinase.</a> Nat Methods. 3 (6), 461-467 (2006).</li><li>Zhang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inducible+site-directed+recombination+in+mouse+embryonic+stem+cells.">Inducible site-directed recombination in mouse embryonic stem cells.</a> Nucleic Acids Res. 24 (4), 543-548 (1996).</li><li>Peitz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+purification+of+cell-permeant+Cre+and+germline+transmission+after+transduction+into+mouse+embryonic+stem+cells.">Enhanced purification of cell-permeant Cre and germline transmission after transduction into mouse embryonic stem cells.</a> Genesis. 45 (8), 508-517 (2007).</li><li>Bosnali, M., Edenhofer, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+transducible+versions+of+transcription+factors+Oct4+and+Sox2.">Generation of transducible versions of transcription factors Oct4 and Sox2.</a> Biol Chem. 389 (7), 851-861 (2008).</li><li>Landry, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Runx+genes+are+direct+targets+of+Scl/Tal1+in+the+yolk+sac+and+fetal+liver.">Runx genes are direct targets of Scl/Tal1 in the yolk sac and fetal liver.</a> Blood. 111 (6), 3005-3014 (2008).</li></ol>

Durante o processo de purificação da proteína de fusão Cre, é importante não omitir a adição de gelo tampão TBS frio antes da centrifugação. Caso contrário Cre recombinase tende a precipitar dentro do buffer de glicerol. Se a fração eluato parece tornar-se turva devido à alta concentração de proteína de fusão do buffer de eluição deve ser adicionado até que a solução cancelou novamente. A aplicação de 10 mM de Cre proteína de fusão normalmente resulta em uma eficiência de recombinação de 80 a 100%. Soro fetal bovino (FCS), sendo um componente importante do ES médio de células inibe fortemente transdução de proteína. Portanto, alta concentração de Cre recombinase teve que ser usado. Ao trabalhar no soro livre de condições menos proteínas (0,5-2 mM) pode ser utilizado para alcançar a eficiência de recombinação semelhante. Com o sistema vector pSESAME na mão pode-se aplicar a técnica de transdução de proteína para outras proteínas, incluindo fatores de transcrição como Oct4 e Sox2 7 e 8 Scl/Tal1.

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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">	
		
		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>TUNER (DE3) pLacI</td>
<td>&nbsp;</td>
<td>Novagen</td>
<td>70625</td>
<td>&nbsp;</td>
<tr>
<td>Glycerol</td>
<td>&nbsp;</td>
<td>Carl Roth</td>
<td>3783.2</td>
<td>&nbsp;</td>
<tr>
<td>Na2HPO4</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>T876.1</td>
<td>&nbsp;</td>
<tr>
<td>Trizma Base</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>T1503</td>
<td>&nbsp;</td>
<tr>
<td>HCl</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>4625.1</td>
<td>&nbsp;</td>
<tr>
<td>Imidazol</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>X998.4</td>
<td>&nbsp;</td>
<tr>
<td>NaCl</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>9265.2</td>
<td>&nbsp;</td>
<tr>
<td>Yeast Extract</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>2363.4</td>
<td>&nbsp;</td>
<tr>
<td>Trypton/Pepton</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>8952.4</td>
<td>&nbsp;</td>
<tr>
<td>K2HPO4 </td>
<td>&nbsp;</td>
<td>Roth</td>
<td>P749.2</td>
<td>&nbsp;</td>
<tr>
<td>KH2PO4</td>
<td>&nbsp;</td>
<td>Roth</td>
<td>3904.1</td>
<td>&nbsp;</td>
<tr>
<td>Ampicillin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>A9518</td>
<td>&nbsp;</td>
<tr>
<td>Carbenicillin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>6344.2</td>
<td>&nbsp;</td>
<tr>
<td>HEPES</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>H3375</td>
<td>&nbsp;</td>
<tr>
<td>Lysozyme</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>62971</td>
<td>&nbsp;</td>
<tr>
<td>Benzonase</td>
<td>&nbsp;</td>
<td>Novagen</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>L-Tartaric acid, disodium salt </td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>50% Ni-NTA slurry</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>R901-15</td>
<td>&nbsp;</td>
<tr>
<td>EconoPac columns</td>
<td>&nbsp;</td>
<td>Biorad</td>
<td>732-1010</td>
<td>&nbsp;</td>
<tr>
<td>Sterile filter 0,22&mu;m</td>
<td>&nbsp;</td>
<td>Whatman</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Paraformaldehyde (PFA)</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>LB medium</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Yeast extract, Trypton/Pepton, NaCl</td>
</tr>
<tr>
<td>TB medium</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Yeast extract, Trypton/Pepton, Glycerol, K2HPO4, KH2PO4</td>
</tr>
<tr>
<td>Lysis Buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>50 mM Na2HPO4, 5 mM Tris, pH 7.8</td>
</tr>
<tr>
<td>Tartaric Salt Buffer (TSB)</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>PTB containing 2 M L-Tartaric acid, disodium salt, and 20 mM Imidazol</td>
</tr>
<tr>
<td>Washing Buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>PTB, 500 mM NaCl, 15 mM Imidazol</td>
</tr>
<tr>
<td>Elution Buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>PTB, 500 mM NaCl, 250 mM Imidazol</td>
</tr>
<tr>
<td>High Salt Buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>600 mM NaCl, 20 mM HEPES, pH 7.4</td>
</tr>
<tr>
<td>Gylcerol Buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>50% glycerol, 500 mM NaCl, 20 mM HEPES, pH 7.4</td>
</tr>
<tr>
<td>TrypLE&trade; Express</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>ESGRO (LIF)</td>
<td>&nbsp;</td>
<td>Millipore</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>NEAA</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>11140035</td>
<td>&nbsp;</td>
<tr>
<td>L-Glutamin</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>25030024</td>
<td>&nbsp;</td>
<tr>
<td>&beta;-Mercaptoethanol</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>31350010</td>
<td>&nbsp;</td>
<tr>
<td>DMEM</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>11960044</td>
<td>&nbsp;</td>
<tr>
<td>PBS</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Fetal Calf Serum (FCS)</td>
<td>&nbsp;</td>
<td>PAA</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>X-Gal staining solution:</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>4 mM K3(FeIII(CN)6), 4 mM K4(FeII(CN)6), 2mM MgCl2 0.4 mg/mL X-Gal solved in PBS</td>
</tr>
<tr>
<td>K3(FeIII(CN)6)</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>P-3367</td>
<td>&nbsp;</td>
<tr>
<td>K4 (FeII(CN)6)</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>P-9387</td>
<td>&nbsp;</td>
<tr>
<td>MgCl2</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>M8266</td>
<td>&nbsp;</td>
<tr>
<td>X-Gal</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>B4252</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

engineering cell-permeable protein

A técnica de transdução de proteína permite a entrega directa do material biologicamente ativo em células de mamíferos [para revisão ver 1,2]. Para este pode-se fazer uso da capacidade translocação dos peptídeos chamada célula penetrante (CPPs), também designado como domínios de proteína de transdução (PTDs). O TAT-CPP derivado do tipo de vírus da imunodeficiência humana 1 (HIV-1) Tat proteína (trans-ativador de transcrição) tem sido amplamente utilizada. O TAT positivamente carregada promove permeabilidade celular, assim, superar as barreiras da membrana celular por endocitose e / ou penetração direta da membrana 2. Em combinação com um sinal de localização nuclear (NLS) proteínas de fusão são capazes de entrar a funcionalidade núcleo expositoras. Nossa apresentação em vídeo demonstra, como uma exemplificação para a engenharia de células-permeável proteínas, a construção, produção e aplicação de uma versão de células-permeável do DNA-enzima Cre modificando. Cre recombinase é um site-specific que é capaz de reconhecer e recombinar base de 34 sites de loxP par em células de mamíferos in vitro e in vivo. Portanto, o sistema Cre / loxP é amplamente utilizado para condicionalmente induzir mutações no genoma das células vivas 3,4. A entrega de ativos Cre recombinase para as células, no entanto, representa uma limitação. Nós descrevemos o sistema vector pSESAME, que permite uma inserção direta do gene de interesse e fornece uma plataforma para rapidamente clone diferentes domínios e marcas usadas dentro do vetor de uma maneira conveniente e padronizado. Reorganização das tags diferentes tem sido mostrado para modificar as propriedades bioquímicas das proteínas de fusão com a possibilidade da obtenção de maior rendimento e melhor solubilidade. Demonstramos como expressar e purificar recombinante de células-permeante proteínas e de E. coli. A funcionalidade da proteína recombinante Cre está finalmente validada em cultura de células, avaliando sua atividade recombinase intracelular.

Watch this Scientific Journal Video about Engineering Cell-permeable Protein at JoVE.com

Engineering Cell-permeable Protein

Transdução da proteína permite a entrega direta de proteínas biologicamente ativos nas células. Em contraste com os métodos convencionais, tais como a transfecção de DNA viral ou transdução este paradigma não-invasivo altamente eficiente permite a manipulação celular de uma forma titulável contornar toxicidade celular eo risco de transformação oncogênica por modificação genética permanente.

Engenharia de Proteínas Cell-permeáveis

The protein transduction technique enables the direct delivery of biologically active material into mammalian cells [for review see 1,2]. For this one can ...

Research

JoVE Journal

Biology

14.4K visualizações.  University of Bonn - Life & Brain Center and Hertie Foundation. Transdução da proteína permite a entrega direta de proteínas biologicamente ativos nas células. Em contraste com os métodos convencionais, tais como a transfecção de DNA viral ou transdução este paradigma não-invasivo altamente eficiente permite a manipulação celular de uma forma titulável contornar toxicidade celular eo risco de transformação oncogênica por modificação genética permanente.

Vídeo: Engineering Cell-permeable Protein

Experimental Approaches to Tissue Engineering

Abordagens experimentais de Engenharia de Tecidos

Biologia

Micro-scale Engineering for Cell Biology

Micro-escala de Engenharia de Biologia Celular

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

Coloração de proteínas em géis com Coomassie G-250 sem ácido acético e Solventes Orgânicos

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering 

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development of constructs for tissue engineering. This environment better mimics what cells observe in vivo, compared to standard tissue culture, due to the tissue-like properties and 3D environment. Synthetic polymeric hydrogels are water-swollen networks that can be designed to be stable or to degrade through hydrolysis or proteolysis as new tissue is deposited by encapsulated cells. A wide variety of polymers have been explored for these applications, such as poly(ethylene glycol) and hyaluronic acid. Most commonly, the polymer is functionalized with reactive groups such as methacrylates or acrylates capable of undergoing crosslinking through various mechanisms. In the past decade, much progress has been made in engineering these microenvironments - e.g., via the physical or pendant covalent incorporation of biochemical cues - to improve viability and direct cellular phenotype, including the differentiation of encapsulated stem cells (Burdick et al.).
The following methods for the 3D encapsulation of cells have been optimized in our and other laboratories to maximize cytocompatibility and minimize the number of hydrogel processing steps. In the following protocols (see Figure 1 for an illustration of the procedure), it is assumed that functionalized polymers capable of undergoing crosslinking are already in hand; excellent reviews of polymer chemistry as applied to the field of tissue engineering may be found elsewhere (Burdick et al.) and these methods are compatible with a range of polymer types. Further, the Michael-type addition (see Lutolf et al.) and light-initiated free radical (see Elisseeff et al.) mechanisms focused on here constitute only a small portion of the reported crosslinking techniques. Mixed mode crosslinking, in which a portion of reactive groups is first consumed by addition crosslinking and followed by a radical mechanism, is another commonly used and powerful paradigm for directing the phenotype of encapsulated cells (Khetan et al., Salinas et al.).

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering

We present protocols for the 3-dimensional (3D) encapsulation of cells within synthetic hydrogels. The encapsulation procedure is outlined for two commonly used methods of crosslinking (michael-type addition and light-initiated free radical mechanisms), as well as a number of techniques for assessing encapsulated cell behavior.

O encapsulamento celular em Hidrogéis 3D para Engenharia de Tecidos

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development ...

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.

Usando o sistema de fracionamento GELFREE 8100 para Fracionamento baseada no peso molecular com Recovery Fase Líquida

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

Automated Hydrophobic Interaction Chromatography Column Selection for Use in Protein Purification

In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction chromatography (HIC) commonly requires experimental determination (referred to as screening or "scouting") in order to select the most suitable chromatographic medium for purifying a given protein 1. The method presented here describes an automated approach to scouting for an optimal HIC media to be used in protein purification.
HIC separates proteins and other biomolecules from a crude lysate based on differences in hydrophobicity. Similar to affinity chromatography (AC) and ion exchange chromatography (IEX), HIC is capable of concentrating the protein of interest as it progresses through the chromatographic process. Proteins best suited for purification by HIC include those with hydrophobic surface regions and able to withstand exposure to salt concentrations in excess of 2 M ammonium sulfate ((NH4)2SO4). HIC is often chosen as a purification method for proteins lacking an affinity tag, and thus unsuitable for AC, and when IEX fails to provide adequate purification. Hydrophobic moieties on the protein surface temporarily bind to a nonpolar ligand coupled to an inert, immobile matrix. The interaction between protein and ligand are highly dependent on the salt concentration of the buffer flowing through the chromatography column, with high ionic concentrations strengthening the protein-ligand interaction and making the protein immobile (i.e. bound inside the column) 2. As salt concentrations decrease, the protein-ligand interaction dissipates, the protein again becomes mobile and elutes from the column. Several HIC media are commercially available in pre-packed columns, each containing one of several hydrophobic ligands (e.g. S-butyl, butyl, octyl, and phenyl) cross-linked at varying densities to agarose beads of a specific diameter 3. Automated column scouting allows for an efficient approach for determining which HIC media should be employed for future, more exhaustive optimization experiments and protein purification runs 4.
The specific protein being purified here is recombinant green fluorescent protein (GFP); however, the approach may be adapted for purifying other proteins with one or more hydrophobic surface regions. GFP serves as a useful model protein, due to its stability, unique light absorbance peak at 397 nm, and fluorescence when exposed to UV light 5. Bacterial lysate containing wild type GFP was prepared in a high-salt buffer, loaded into a Bio-Rad DuoFlow medium pressure liquid chromatography system, and adsorbed to HiTrap HIC columns containing different HIC media. The protein was eluted from the columns and analyzed by in-line and post-run detection methods. Buffer blending, dynamic sample loop injection, sequential column selection, multi-wavelength analysis, and split fraction eluate collection increased the functionality of the system and reproducibility of the experimental approach.

An automated method for identifying suitable hydrophobic interaction chromatography (HIC) media to be used in the process of protein purification is presented. The method utilizes a medium-pressure liquid chromatography system including automated buffer blending, dynamic sample loop injection, sequential column selection, multi-wavelength analysis, and split fraction eluate collection.

Automated interação hidrofóbica Seleção coluna de cromatografia para uso na purificação de proteínas

In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction ...

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific properties, such as binding affinity, agonist or antagonist behavior, or stability, relative to the native sequence. Protein design lies at the center of current advances drug design and discovery. Not only does protein design provide predictions for potentially useful drug targets, but it also enhances our understanding of the protein folding process and protein-protein interactions. Experimental methods such as directed evolution have shown success in protein design. However, such methods are restricted by the limited sequence space that can be searched tractably. In contrast, computational design strategies allow for the screening of a much larger set of sequences covering a wide variety of properties and functionality. We have developed a range of computational de novo protein design methods capable of tackling several important areas of protein design. These include the design of monomeric proteins for increased stability and complexes for increased binding affinity.
To disseminate these methods for broader use we present Protein WISDOM (<a href="http://www.proteinwisdom.org" target="_blank">http://www.proteinwisdom.org</a>), a tool that provides automated methods for a variety of protein design problems. Structural templates are submitted to initialize the design process. The first stage of design is an optimization sequence selection stage that aims at improving stability through minimization of potential energy in the sequence space. Selected sequences are then run through a fold specificity stage and a binding affinity stage. A rank-ordered list of the sequences for each step of the process, along with relevant designed structures, provides the user with a comprehensive quantitative assessment of the design. Here we provide the details of each design method, as well as several notable experimental successes attained through the use of the methods.

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

We developed computational de novo protein design methods capable of tackling several important areas of protein design. To disseminate these methods we present Protein WISDOM, an online tool for protein design (<a href="http://www.proteinwisdom.org" target="_blank">http://www.proteinwisdom.org</a>). Starting from a structural template, design of monomeric proteins for increased stability and complexes for increased binding affinity can be performed.

SABEDORIA Protein: A Workbench para<em&gt; In silico</em&gt;<em&gt; De novo</em&gt; Projeto de biomoléculas

The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific ...

Mouse Genome Engineering Using Designer Nucleases

Transgenic mice carrying site-specific genome modifications (knockout, knock-in) are of vital importance for dissecting complex biological systems as well as for modeling human diseases and testing therapeutic strategies. Recent advances in the use of designer nucleases such as zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) 9 system for site-specific genome engineering open the possibility to perform rapid targeted genome modification in virtually any laboratory species without the need to rely on embryonic stem (ES) cell technology. A genome editing experiment typically starts with identification of designer nuclease target sites within a gene of interest followed by construction of custom DNA-binding domains to direct nuclease activity to the investigator-defined genomic locus. Designer nuclease plasmids are in vitro transcribed to generate mRNA for microinjection of fertilized mouse oocytes. Here, we provide a protocol for achieving targeted genome modification by direct injection of TALEN mRNA into fertilized mouse oocytes.

Designer nucleases such as zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) can be used to modify the genome of mouse preimplantation embryos by triggering both the nonhomologous end joining (NHEJ) and homologous recombination (HR) pathways. These advances enable the rapid generation of mice with precise genetic modifications.

Rato Genoma Engenharia Usando Nucleases Designer

Transgenic mice carrying site-specific genome modifications (knockout, knock-in) are of vital importance for dissecting complex biological systems as well ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and the inherent instability of many membrane proteins once solubilized in detergents. A protocol is described that combines ligation independent cloning of membrane proteins as GFP fusions with expression in Escherichia coli detected by GFP fluorescence. This enables the construction and expression screening of multiple membrane protein/variants to identify candidates suitable for further investment of time and effort. The GFP reporter is used in a primary screen of expression by visualizing GFP fluorescence following SDS polyacrylamide gel electrophoresis (SDS-PAGE). Membrane proteins that show both a high expression level with minimum degradation as indicated by the absence of free GFP, are selected for a secondary screen. These constructs are scaled and a total membrane fraction prepared and solubilized in four different detergents. Following ultracentrifugation to remove detergent-insoluble material, lysates are analyzed by fluorescence detection size exclusion chromatography (FSEC). Monitoring the size exclusion profile by GFP fluorescence provides information about the mono-dispersity and integrity of the membrane proteins in different detergents. Protein: detergent combinations that elute with a symmetrical peak with little or no free GFP and minimum aggregation are candidates for subsequent purification. Using the above methodology, the heterologous expression in E. coli of SED (shape, elongation, division, and sporulation) proteins from 47 different species of bacteria was analyzed. These proteins typically have ten transmembrane domains and are essential for cell division. The results show that the production of the SEDs orthologues in E. coli was highly variable with respect to the expression levels and integrity of the GFP fusion proteins. The experiment identified a subset for further investigation.

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

A streamlined approach to screening for the expression of recombinant membrane proteins in Escherichia coli based on fusion to green fluorescent protein is presented.

Verde Fluorescente à base de proteínas Expressão Rastreio de Proteínas de Membrana em<em&gt; Escherichia coli</em

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains

Due to their modularity and ability to be reprogrammed to recognize a wide range of DNA sequences, Cys2-His2 zinc-finger DNA-binding domains have emerged as useful tools for targeted genome engineering. Like many other DNA-binding proteins, zinc-fingers also possess the innate ability to cross cell membranes. We recently demonstrated that this intrinsic cell-permeability could be leveraged for intracellular protein delivery. Genetic fusion of zinc-finger motifs leads to efficient transport of protein and enzyme cargo into a broad range of mammalian cell types. Unlike other protein transduction technologies, delivery via zinc-finger domains does not inhibit enzyme activity and leads to high levels of cytosolic delivery. Here a detailed step-by-step protocol is presented for the implementation of zinc-finger technology for protein delivery into mammalian cells. Key steps for achieving high levels of intracellular zinc-finger-mediated delivery are highlighted and strategies for maximizing the performance of this system are discussed.

Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains

Zinc-finger domains are intrinsically cell-permeable and capable of mediating protein delivery into a broad range of mammalian cell types. Here, a detailed step-by-step protocol for implementing zinc-finger technology for intracellular protein delivery is presented.

Entrega Protein direto para células de mamíferos utilizando células-permeável Cys<sub&gt; 2</sub&gt; -His<sub&gt; 2</sub&gt; Domínios zinc-finger

Due to their modularity and ability to be reprogrammed to recognize a wide range of DNA sequences, Cys2-His2 zinc-finger DNA-binding domains have emerged ...