Este trabalho foi financiado pelo NIH R01 EB014869.

1. preparar células para a imagem latente
Nota: A sonda de força direta (DFP) pode ser usada para qualquer tipo de células aderentes. Aqui, fibroblastos de rato do NIH 3T3 são usados como a linha celular do modelo para este protocolo.
<ol><li>Células de fibroblastos cultura NIH 3T3 em modificado águia de Dulbecco médio (DMEM) suplementado com 10% de soro de bovino doador e 1% penicilina-estreptomicina em um fundo de vidro 35mm prato até confluência desejada. Manter as células em 37 ° C e 5% de CO2.<ol>
<li>Não se esqueça de revestir todos os pratos de fundo de vidro 35mm com 5 µ g/mL de fibronectina (ou proteína de ECM semelhante), antes da semeadura das células 3T3 NIH para a imagem latente. Nota: As células devem ser totalmente espalhadas e aderente sobre o prato para o experimento. Não existem quaisquer restrições em termos de confluência para o método DFP trabalhar.</li>
	</ol>
</li>
	<li>Imediatamente antes do experimento, as células de duas lavagens com PBS, seguido por uma simples lavagem com meio de cultura completo.</li>
	<li>Adicione 3 mL de meio de cultura completo para o prato fundo de vidro.</li>
</ol>2. microscopia e aquisição de imagem
Nota: Um invertido fluorescência microscópio (ou equivalente) com micromanipulador instalado para o lado do braço, de acordo com as recomendações do fabricante. O microscópio também deve ser equipado com uma câmara ambiental para manter a temperatura a 37 ° C e o nível de CO2 em 5%. Também é necessário um micromanipulador e microinjector anexado ao microscópio. Um óleo de imersão x 40 / 1,3 at ou 60 x / 1.49 at (ou objectivos equivalentes) são recomendados para os experimentos. O microscópio deve ser montado sobre uma mesa de isolamento de vibração.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58038/58038fig1.jpg"> Figura 1 . Deformação nuclear e microscópio com foco R. máxima deformação nuclear e relaxamento da deformação nuclear. Antes de calcular a máxima deformação nuclear, as bordas traseiras das formas nucleares foram primeiro coincidiu para corrigir para a tradução do núcleo deformado. A forma do núcleo no momento do desprendimento de ponta micropipeta era revestida na forma nuclear inicial antes de puxar. A diferença de área entre as duas formas foi medida como Δum1. A máxima deformação nuclear foi definida como ΔA1 dividido pela área nuclear original. Da mesma forma, um segundo parâmetro, ΔA2, podem ser definidas por sobrepondo a forma nuclear final estado estacionário após descolamento micropipeta na forma nuclear original. B. a célula no avião A concentrar-se e mova o plano focal até avião B para encontrar a ponta da micropipeta. Durante a imagem latente, a micropipeta foi traduzida para a direita (sentido da seta laranja). Esta figura foi modificada de Eelam et al. 15. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/58038/58038fig1large.jpg" target="_blank">clique aqui para ver uma versão maior desta figura.</a>
<ol><li>Ligue o microinjector acordo com o protocolo do fabricante.</li>
	<li>Usando um gotas de óleo de imersão, aplica uma gota de óleo de imersão em cima da lente objetiva.</li>
	<li>Fixar o prato firmemente no suporte do prato e carregar o suporte para o palco. Nota: As células devem ser mantidas a 37 ° C e 5% CO2 durante todo o experimento.</li>
	<li>Ajuste a altura do objectivo de colocar as células em foco (A do avião, figura 1B).</li>
	<li>Mova o estágio de microscópio para encontrar uma célula de interesse.</li>
	<li>Gire o joystick no micromanipulador para mover o titular pipeta para a posição superior. Carrega a micropipeta de ponta de diâmetro de 0,5 µm no suporte pipeta.<ol>
<li>Para evitar aderência de célula para a micropipeta, pré-tratamento a ponta da micropipeta com 0,3 mg/mL solução de PLL-g-PEG por 1h à temperatura ambiente. Teste de aderência tocando a micropipeta para o núcleo sem qualquer pressão de sucção, e então traduzir a micropipeta longe do núcleo. A ausência de adesão pode ser discernida por falta completa de deformação nuclear e tradução. Nota: Por favor siga sugestões de fabrico para abrir o pacote.</li>
	</ol>
</li>
	<li>Elevar o plano focal objectivo acima A do avião e o topo da célula para o plano B, ajustando o controle fino (figura 1B, consulte a etapa 2.4).</li>
	<li>Conjunto o micromanipulador para controle de grosseira . Traga lentamente a micropipeta até avião B observando para a silhueta da micropipeta, até a micropipeta totalmente entra em foco.</li>
	<li>Uma vez que a ponta da micropipeta está em foco, defina o micromanipulador para controle fino .</li>
	<li>Baixe o objectivo para o plano equatorial da célula (avião A, figura 1B) e inferior a micropipeta para cerca de 15 µm acima plano A (figura 1B, micropipeta tracejada).</li>
	<li>Ajustar a pressão de compensação (Pc) sobre o microinjector a pressão desejada; Aguarde alguns segundos até a pressão estabilizar. Nota: O ponto de ajuste de pressão ideal depende de tipo de célula e os objetivos específicos do experimento. Para a maioria dos casos, 300 hPa seria um bom ponto de partida.</li>
	<li>Certifique-se de que a micropipeta não está entupida usando a configuração de limpeza no painel micromanipulador e verificar para certificar-se de bolhas de ar emergem da ponta da micropipeta.</li>
	<li>Introduza a ponta dentro da célula, diminuindo gradualmente a micropipeta, até que a ponta é levemente tocar a superfície nuclear. Nota: Ao descer a micropipeta, a silhueta da ponta da micropipeta se tornará clara como entra em foco. Antes a micropipeta toca o núcleo, aumentar o foco da objetivo e alinhe a ponta da micropipeta com núcleo (mesma coordenada x-y, z-plano superior). Retornar o foco para o plano equatorial do núcleo (A de avião, figura 1B) e gradualmente diminuir a ponta da micropipeta.</li>
	<li>Crie um selo entre a ponta da micropipeta e a membrana nuclear, desconectar o tubo de alimentação de pressão do sistema de microinjeção, abrindo assim a extremidade do tubo micropipeta para a atmosfera. Esta etapa cria uma pressão negativa igual a Pc na superfície nuclear.</li>
	<li>Adquira imagens com o software de coleta de imagem de microscópios. Configure um avi-aquisição (vídeo) ou nd-aquisição do software de coleta de imagem (imagens). Nota: Para qualquer imagem adquirir o software, criar imagens de vídeo em tempo real ou aquisições de imagem de lapso de tempo com um curto intervalo de tempo.</li>
	<li>Alternar para o fluorescente correspondente canal de imagem (ou seja, as boas práticas agrícolas, RFP, etc.) e começar a imagem latente.</li>
	<li>Definição da palavra a ponta da micropipeta longe do corpo da célula (para a direita, figura 1B) até que o núcleo se desprende da micropipeta. Nota: Puxe a ponta ao longo de x-direção positiva (à direita no campo de visão). A taxa de tração pode ser programada e controlada por computador ou o joystick pode ser movido manualmente. Não encontramos qualquer correlação entre a tirar taxa e deformação nuclear15 sugerindo uma resposta principalmente elástica para forçar.</li>
</ol>3. análise de dados
<ol><li>Realizar análise de imagem com qualquer software de processamento de imagem básico disponível. O grau de deformação nuclear pode ser quantificado pela estirpe de comprimento (Ɛ) ou a tensão da área (figura 1A). Quantificar a estirpe de comprimento usando a equação 1, onde L e L0 representam os comprimentos do núcleo na deformação máxima e a posição inicial, respectivamente. <img alt="Equation 1" src="/files/ftp_upload/58038/58038eq1.jpg">(Equação 1)</li>
</ol>

<ol>
	<li>Chow, K. H., Factor, R. E., Ullman, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nuclear+envelope+environment+and+its+cancer+connections.">The nuclear envelope environment and its cancer connections.</a> Nature Reviews Cancer. 12 (3), 196-209 (2012).</li><li>Zink, D., Fischer, A. H., Nickerson, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+structure+in+cancer+cells.">Nuclear structure in cancer cells.</a> Nature Reviews Cancer. 4 (9), 677-687 (2004).</li><li>Bank, E. M., Gruenbaum, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nuclear+lamina+and+heterochromatin:+a+complex+relationship.">The nuclear lamina and heterochromatin: a complex relationship.</a> Biochemical Society Transactions. 39 (6), 1705-1709 (2011).</li><li>Lammerding, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lamins+A+and+C+but+not+lamin+B1+regulate+nuclear+mechanics.">Lamins A and C but not lamin B1 regulate nuclear mechanics.</a> Journal of Biological Chemistry. 281 (35), 25768-25780 (2006).</li><li>Dahl, K. N., Engler, A. J., Pajerowski, J. D., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Power-law+rheology+of+isolated+nuclei+with+deformation+mapping+of+nuclear+substructures.">Power-law rheology of isolated nuclei with deformation mapping of nuclear substructures.</a> Biophysical Journal. 89 (4), 2855-2864 (2005).</li><li>Crisp, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coupling+of+the+nucleus+and+cytoplasm:+role+of+the+LINC+complex.">Coupling of the nucleus and cytoplasm: role of the LINC complex.</a> Journal of Cell Biology. 172 (1), 41-53 (2006).</li><li>Sosa, B. A., Rothballer, A., Kutay, U., Schwartz, T. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LINC+complexes+form+by+binding+of+three+KASH+peptides+to+domain+interfaces+of+trimeric+SUN+proteins.">LINC complexes form by binding of three KASH peptides to domain interfaces of trimeric SUN proteins.</a> Cell. 149 (5), 1035-1047 (2012).</li><li>Tapley, E. C., Starr, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connecting+the+nucleus+to+the+cytoskeleton+by+SUN-KASH+bridges+across+the+nuclear+envelope.">Connecting the nucleus to the cytoskeleton by SUN-KASH bridges across the nuclear envelope.</a> Current Opinion in Cell Biology. 25 (1), 57-62 (2013).</li><li>Arsenovic, P. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nesprin-2G,+a+Component+of+the+Nuclear+LINC+Complex,+Is+Subject+to+Myosin-Dependent+Tension.">Nesprin-2G, a Component of the Nuclear LINC Complex, Is Subject to Myosin-Dependent Tension.</a> Biophysical Journal. 110 (1), 34-43 (2016).</li><li>Rowat, A. C., Lammerding, J., Ipsen, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+the+cell+nucleus+and+the+effect+of+emerin+deficiency.">Mechanical properties of the cell nucleus and the effect of emerin deficiency.</a> Biophysical Journal. 91 (12), 4649-4664 (2006).</li><li>Rowat, A. C., Foster, L. J., Nielsen, M. M., Weiss, M., Ipsen, J. H. <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+the+elastic+properties+of+the+nuclear+envelope.">Characterization of the elastic properties of the nuclear envelope.</a> Journal of the Royal Society Interface. 2 (2), 63-69 (2005).</li><li>Pagliara, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Auxetic+nuclei+in+embryonic+stem+cells+exiting+pluripotency.">Auxetic nuclei in embryonic stem cells exiting pluripotency.</a> Nature Materials. 13 (6), 638-644 (2014).</li><li>Liu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+mechanical+characterization+of+the+cell+nucleus+by+atomic+force+microscopy.">In situ mechanical characterization of the cell nucleus by atomic force microscopy.</a> ACS Nanotechnology. 8 (4), 3821-3828 (2014).</li><li>Krause, M., Te Riet, J., Wolf, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+compressibility+of+tumor+cell+nuclei+by+combined+atomic+force-confocal+microscopy.">Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy.</a> Physical Biology. 10 (6), 065002 (2013).</li><li>Neelam, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+force+probe+reveals+the+mechanics+of+nuclear+homeostasis+in+the+mammalian+cell.">Direct force probe reveals the mechanics of nuclear homeostasis in the mammalian cell.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (18), 5720-5725 (2015).</li><li>Pajerowski, J. D., Dahl, K. N., Zhong, F. L., Sammak, P. J., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+plasticity+of+the+nucleus+in+stem+cell+differentiation.">Physical plasticity of the nucleus in stem cell differentiation.</a> Proceedings of the National Academy of Sciences of the United States of America. 104 (40), 15619-15624 (2007).</li><li>Lammerding, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lamin+A/C+deficiency+causes+defective+nuclear+mechanics+and+mechanotransduction.">Lamin A/C deficiency causes defective nuclear mechanics and mechanotransduction.</a> Journal of Clinical Investigation. 113 (3), 370-378 (2004).</li><li>Chancellor, T. J., Lee, J., Thodeti, C. K., Lele, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actomyosin+tension+exerted+on+the+nucleus+through+nesprin-1+connections+influences+endothelial+cell+adhesion,+migration,+and+cyclic+strain-induced+reorientation.">Actomyosin tension exerted on the nucleus through nesprin-1 connections influences endothelial cell adhesion, migration, and cyclic strain-induced reorientation.</a> Biophysical Journal. 99 (1), 115-123 (2010).</li><li>Neelam, S., Dickinson, R. B., Lele, T. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+approaches+for+understanding+the+nuclear+force+balance+in+living,+adherent+cells.">New approaches for understanding the nuclear force balance in living, adherent cells.</a> Methods. 94, 27-32 (2016).</li></ol>

Os autores não têm nada para divulgar.

Medindo a integração mecânica do núcleo com o citoesqueleto é um desafio para métodos mais atuais, como micropipeta aspiração16, pois eles exigem ou núcleos isolados (onde o núcleo é dissociado do citoesqueleto) ou núcleos em células suspensos (onde forças extracelulares, como forças de tração, estão ausentes). Força aplicou-se para o núcleo aplicando tensão biaxial de aderente de células a uma membrana17,,18; no enta...

Patologias como câncer envolvem alterações à forma nuclear e estrutura1,2, que geralmente são acompanhados de um amolecimento do núcleo3,4. Nuclear resistência à deformação mecânica tem sido geralmente caracterizada pela aplicação de uma força de núcleos isolados5.
O núcleo nas células molecularmente está ligado ao citoesqueleto pelo vinculador de Nucleoskeleton e citoesqueleto (LINC) complexo6,7,8,9. Como resultado, o núcleo mecanicamente é integrado com o citoesqueleto e, através de aderências célula-substrato, a matriz extracelular. Mecanicamente, sondar o núcleo no interior das células aderentes pode fornecer insights sobre essa integração mecânica. Métodos para manipular os núcleos em células vivas incluem micropipeta aspiração10,11e microscopia de força atômica a12,13,14. Recentemente descrevemos uma sonda de força direta (DFP) que se aplica forças mecânicas diretamente no núcleo em uma vida aderentes célula15.
Aqui, podemos descrever o procedimento para usar um sistema de microinjeção que está geralmente disponível em instalações de microscopia para aplicar uma força mecânica de nano-escala conhecida, diretamente para o núcleo em uma célula aderente. Um femtotip (0,5 µm ponta de micropipeta de diâmetro) é montado e ligado ao sistema de microinjeção por um tubo. A ponta, posicionada em um ângulo de 45° em relação à superfície do prato, cultura é abaixada até adjacente à superfície nuclear. O tubo é então desligado e aberto para a atmosfera, o que cria uma pressão negativa de sucção na superfície nuclear e lacra a ponta da micropipeta contra a superfície nuclear. Através da tradução da ponta da micropipeta, o núcleo é deformado e eventualmente (dependendo da magnitude da força aplicada), extraído da micropipeta. Este desprendimento ocorre quando as forças de restaura (oposição), exercidas pelo núcleo e célula, igual a força de sucção aplicada pela micropipeta. Análise pode ser realizada medindo-se o deslocamento do núcleo, a estirpe de comprimento (equação 1), ou a tensão da área (figura 1A).

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		<tr height="21">
			<td height="21" style="height:21px;width:299px;">FluoroDish</td>
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			<td style="width:119px;">FD35</td>
			<td style="width:355px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:299px;">SYTO 59</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td style="width:119px;">S11341</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Femtotips&#160;</td>
			<td style="width:71px;">Eppendorf</td>
			<td align="right">930000043</td>
			<td></td>
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			<td height="42" style="height:42px;width:299px;">InjectMan NI2</td>
			<td style="width:71px;">Eppendorf</td>
			<td style="width:119px;">NA</td>
			<td>discontinued, current equivalent model: InjectMan 4</td>
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			<td height="42" style="height:42px;width:299px;">FemtoJet</td>
			<td style="width:71px;">Eppendorf</td>
			<td style="width:119px;">NA</td>
			<td>Current model FemtoJet 4i</td>
		</tr>
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			<td height="21" style="height:21px;width:299px;">Plan Fluor oil immersion 40x</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">NA</td>
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			<td height="21" style="height:21px;width:299px;">Apo TIRF oil immersion 60x</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">NA</td>
			<td></td>
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		<tr height="63">
			<td height="63" style="height:63px;width:299px;">Donor Bovine Serum (DBS)</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td align="right" style="width:119px;">16030074</td>
			<td>NIH 3T3 serum</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Dulbecco&#39;s Modification of Eagle&#39;s (DMEM)</td>
			<td style="width:71px;">Mediatech cellgro</td>
			<td style="width:119px;">MT10013CVRF</td>
			<td>NIH 3T3 medium</td>
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		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Penicillin-Streptomycin&#160;</td>
			<td style="width:71px;">Mediatech</td>
			<td style="width:119px;">MT30004CIRF</td>
			<td>NIH 3T3 medium supplement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Immersion Oil Type LDF Non-Fluorescing</td>
			<td style="width:71px;">Nikon</td>
			<td align="right" style="width:119px;">77007</td>
			<td>Immersion oil for objective lens&#160;</td>
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a direct force probe for measuring mechanical integration between the nucleus and the cytoskeleton

As propriedades mecânicas do núcleo determinam sua resposta às forças mecânicas geradas nas células. Porque o núcleo é molecularmente contínuo com o citoesqueleto, métodos são necessários para sondar seu comportamento mecânico em células aderentes. Aqui, vamos discutir a sonda de força direta (DFP) como uma ferramenta para aplicar a força diretamente para o núcleo em uma célula aderente viva. Atribuímos uma micropipeta estreita à superfície nuclear com sucção. A micropipeta é traduzida longe do núcleo, o que faz com que o núcleo se deforma e traduzir. Quando a força restauradora é igual à força de sucção, o núcleo desconecta e elasticamente, relaxa. Porque o pressão de sucção é precisamente conhecido, é conhecida a força na superfície nuclear. Este método revelou-se que as forças de nano-escala são suficientes para deformar-se e traduzir o núcleo nas células aderentes e identificaram elementos do citoesqueleto que permitem que o núcleo resistir às forças. O DFP pode ser usado para dissecar as contribuições dos componentes celulares e nucleares para propriedades mecânicas nucleares em células vivas.

Figura 2A mostra a força de um núcleo de fibroblasto NIH 3T3 rato. Como a ponta da micropipeta é traduzida para a direita, o núcleo deforma e eventualmente desanexa da ponta da micropipeta. A estirpe do comprimento do núcleo é vista a aumentar com o aumento da força de sucção (Figura 2B). Na extremidade dianteira do núcleo (micropipeta puxando a borda) forma uma protusão nuclear e a borda direita é deslocada de sua po...

Watch this Scientific Journal Video about A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton at JoVE.com

A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton

Uma sonda de força direta para medir a integração mecânica entre o núcleo e o citoesqueleto

Neste protocolo, descrevemos um método de micropipeta para aplicar directamente uma força controlada para o núcleo de uma célula viva. Este ensaio permite interrogatório das propriedades mecânicas nucleares na célula viva, aderente.

The mechanical properties of the nucleus determine its response to mechanical forces generated in cells. Because the nucleus is molecularly continuous ...

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Biochemistry

15.1K visualizações.  University of Florida. Neste protocolo, descrevemos um método de micropipeta para aplicar directamente uma força controlada para o núcleo de uma célula viva. Este ensaio permite interrogatório das propriedades mecânicas nucleares na célula viva, aderente.

Vídeo: A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton

Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the excitability of neurons. The subcellular distribution of these channels in pyramidal neurons of hippocampal area CA1 is regulated by tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), an auxiliary subunit. Genetic knockout of HCN pore forming subunits or TRIP8b, both lead to an increase in antidepressant-like behavior, suggesting that limiting the function of HCN channels may be useful as a treatment for Major Depressive Disorder (MDD). Despite significant therapeutic interest, HCN channels are also expressed in the heart, where they regulate rhythmicity. To circumvent off-target issues associated with blocking cardiac HCN channels, our lab has recently proposed targeting the protein-protein interaction between HCN and TRIP8b in order to specifically disrupt HCN channel function in the brain. TRIP8b binds to HCN pore forming subunits at two distinct interaction sites, although here the focus is on the interaction between the tetratricopeptide repeat (TPR) domains of TRIP8b and the C terminal tail of HCN1. In this protocol, an expanded description of a method for purifying TRIP8b and executing a high throughput screen to identify small molecule inhibitors of the interaction between HCN and TRIP8b, is described. The method for high throughput screening utilizes a Fluorescence Polarization (FP) -based assay to monitor the binding of a large TRIP8b fragment to a fluorophore-tagged eleven amino acid peptide corresponding to the HCN1 C terminal tail. This method allows &#39;hit&#39; compounds to be identified based on the change in the polarization of emitted light. Validation assays are then performed to ensure that &#39;hit&#39; compounds are not artifactual.

The interaction between HCN channels and their auxiliary subunit has been identified as a therapeutic target in Major Depressive Disorder. Here, a fluorescence polarization-based method for identifying small molecule inhibitors of this protein-protein interaction, is presented.

Método para a identificação de molécula pequena inibidores da interacção proteína-proteína entre HCN1 e TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the ...

Bioquímica

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

resolvida no tempo com ionização por electrospray Hidrogénio-deutério troca Espectrometria de Massa para estudar a estrutura e dinâmica das proteínas

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

Force Spectroscopy of Single Protein Molecules Using an Atomic Force Microscope

The determination of the folding process of proteins from their amino acid sequence to their native 3D structure is an important problem in biology. Atomic force microscopy (AFM) can address this problem by enabling stretching and relaxation of single protein molecules, which gives direct evidence of specific unfolding and refolding characteristics. AFM-based single-molecule force-spectroscopy (AFM-SMFS) provides a means to consistently measure high-energy conformations in proteins that are not possible in traditional bulk (biochemical) measurements. Although numerous papers were published to show principles of AFM-SMFS, it is not easy to conduct SMFS experiments due to a lack of an exhaustively complete protocol. In this study, we briefly illustrate the principles of AFM and extensively detail the protocols, procedures, and data analysis as a guideline to achieve good results from SMFS experiments. We demonstrate representative SMFS results of single protein mechanical unfolding measurements and we provide troubleshooting strategies for some commonly encountered problems.

We describe the detailed procedures and strategies to measure the mechanical properties and mechanical unfolding pathways of single protein molecules using an atomic force microscope. We also show representative results as a reference for selection and justification of good single protein molecule recordings.

Espectroscopia de força das moléculas de proteína único, usando um microscópio de força atômica

The determination of the folding process of proteins from their amino acid sequence to their native 3D structure is an important problem in biology. ...

Utilizing a Comprehensive Immunoprecipitation Enrichment System to Identify an Endogenous Post-translational Modification Profile for Target Proteins

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein&#39;s structure and function, which may be essential for a given protein&#39;s role both physiologically and pathologically. Enrichment of PTMs is often necessary when investigating the PTM status of a target protein, because PTMs are often transient and relatively low in abundance. Many pitfalls are encountered when enriching for a PTM of a target protein, such as buffer incompatibility, the target protein antibody is not IP-compatible, loss of PTM signal, and others. The degree of difficulty is magnified when investigating multiple PTMs like acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation for a given target protein. Studying a combination of these PTMs may be necessary, as crosstalk between PTMs is prevalent and critical for protein regulation. Often, these PTMs are studied in different lysis buffers and with unique inhibitor compositions. To simplify the process, a unique denaturing lysis system was developed that effectively isolates and preserves these four PTMs; thus, enabling investigation of potential crosstalk in a single lysis system. A unique filter system was engineered to remove contaminating genomic DNA from the lysate, which is a problematic by-product of denaturing buffers. Robust affinity matrices targeting each of the four PTMs were developed in concert with the buffer system to maximize the enrichment and detection of the endogenous states of these four PTMs. This comprehensive PTM detection toolset streamlines the process of obtaining critical information about whether a protein is modified by one or more of these PTMs.

Investigating multiple, endogenous post-translational modifications for a target protein can be extremely challenging. Techniques described here utilize an optimized lysis buffer and filter system developed with specific PTM-targeting, affinity matrices to detect the acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation modifications for a target protein using a single, streamlined system.

Utilizando um sistema de enriquecimento de imunoprecipitação abrangente para identificar um perfil endógena modificação pós-traducional de proteínas alvo

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein&#39;s structure and function, which ...

A Colorimetric Method for Measuring Iron Content in Plants

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content is rather low in all organisms, amounting in plants to about 0.009% of dry weight. To date, one of the most accurate methods for measuring iron concentration in plant tissues is flame absorption atomic spectroscopy. However, this approach is time-consuming and expensive and requires specific equipment not commonly found in plant laboratories. Therefore, a simpler, yet accurate method that can be routinely used is needed. The colorimetric Prussian Blue method is regularly used for qualitative iron staining in animal and plant histological sections. In this study, we adapted the Prussian Blue method for quantitative measurements of iron in tobacco leaves. We validated the accuracy of this method using both atomic spectroscopy and Prussian Blue staining to measure iron content in the same samples and found a linear regression (R2 = 0.988) between the two procedures. We conclude that the Prussian Blue method for quantitative iron measurement in plant tissues is precise, simple, and inexpensive. However, the linear regression presented here may not be appropriate for other plant species, due to potential interactions between the sample and the reagent. Establishment of a regression curve is thus needed for different plant species.

We present a simple and reliable protocol for measuring iron content in plant tissues using the colorimetric Prussian Blue method.

Um método colorimétrico para medir o teor de ferro nas plantas

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content ...

Polysome Profiling in Leishmania, Human Cells and Mouse Testis

Proper protein expression at the right time and in the right amounts is the basis of normal cell function and survival in a fast-changing environment. For a long time, the gene expression studies were dominated by research on the transcriptional level. However, the steady-state levels of mRNAs do not correlate well with protein production, and the translatability of mRNAs varies greatly depending on the conditions. In some organisms, like the parasite Leishmania, the protein expression is regulated mostly at the translational level. Recent studies demonstrated that protein translation dysregulation is associated with cancer, metabolic, neurodegenerative and other human diseases. Polysome profiling is a powerful method to study protein translation regulation. It allows to measure the translational status of individual mRNAs or examine translation on a genome-wide scale. The basis of this technique is the separation of polysomes, ribosomes, their subunits and free mRNAs during centrifugation of a cytoplasmic lysate through a sucrose gradient. Here, we present a universal polysome profiling protocol used on three different models - parasite Leishmania major, cultured human cells and animal tissues. Leishmania cells freely grow in suspension and cultured human cells grow in adherent monolayer, while mouse testis represents an animal tissue sample. Thus, the technique is adapted to all of these sources. The protocol for the analysis of polysomal fractions includes detection of individual mRNA levels by RT-qPCR, proteins by Western blot and analysis of ribosomal RNAs by electrophoresis. The method can be further extended by examination of mRNAs association with the ribosome on a transcriptome level by deep RNA-seq and analysis of ribosome-associated proteins by mass spectroscopy of the fractions. The method can be easily adjusted to other biological models.

Polysome Profiling in Leishmania, Human Cells and Mouse Testis

The overall goal of polysome profiling technique is analysis of translational activity of individual mRNAs or transcriptome mRNAs during protein synthesis. The method is important for studies of protein synthesis regulation, translation activation and repression in health and multiple human diseases.

Polysome de criação de perfil em Leishmania, células humanas e testículo de rato

Proper protein expression at the right time and in the right amounts is the basis of normal cell function and survival in a fast-changing environment. For ...

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

In recent years, atomic force microscopy (AFM) based single molecule force spectroscopy (SMFS) extended our understanding of molecular properties and functions. It gave us the opportunity to explore a multiplicity of biophysical mechanisms, e.g., how bacterial adhesins bind to host surface receptors in more detail. Among other factors, the success of SMFS experiments depends on the functional and native immobilization of the biomolecules of interest on solid surfaces and AFM tips. Here, we describe a straightforward protocol for the covalent coupling of proteins to silicon surfaces using silane-PEG-carboxyls and the well-established N-hydroxysuccinimid/1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimid (EDC/NHS) chemistry in order to explore the interaction of pilus-1 adhesin RrgA from the Gram-positive bacterium Streptococcus pneumoniae (S. pneumoniae) with the extracellular matrix protein fibronectin (Fn). Our results show that the surface functionalization leads to a homogenous distribution of Fn on the glass surface and to an appropriate concentration of RrgA on the AFM cantilever tip, apparent by the target value of up to 20% of interaction events during SMFS measurements and revealed that RrgA binds to Fn with a mean force of 52 pN. The protocol can be adjusted to couple via site specific free thiol groups. This results in a predefined protein or molecule orientation and is suitable for other biophysical applications besides the SMFS.

This protocol describes the covalent immobilization of proteins with a heterobifunctional silane coupling agent to silicon-oxide surfaces designed for the atomic force microscopy based single molecule force spectroscopy which is exemplified by the interaction of RrgA (pilus-1 tip adhesin of S. pneumoniae) with fibronectin.

Imobilização covalente de proteínas para a espectroscopia de força única molécula

In recent years, atomic force microscopy (AFM) based single molecule force spectroscopy (SMFS) extended our understanding of molecular properties and ...

Imaging of Extracellular Vesicles by Atomic Force Microscopy

Exosomes and other extracellular vesicles (EVs) are molecular complexes consisting of a lipid membrane vesicle, its surface decoration by membrane proteins and other molecules, and diverse luminal content inherited from a parent cell, which includes RNAs, proteins, and DNAs. The characterization of the hydrodynamic sizes of EVs, which depends on the size of the vesicle and its coronal layer formed by surface decorations, has become routine. For exosomes, the smallest of EVs, the relative difference between the hydrodynamic and vesicles sizes is significant. The characterization of vesicles sizes by the cryogenic transmission electron microscopy (cryo-TEM) imaging, a gold standard technique, remains a challenge due to the cost of the instrument, the expertise required to perform the sample preparation, imaging and data analysis, and a small number of particles often observed in images. A widely available and accessible alternative is the atomic force microscopy (AFM), which can produce versatile data on three-dimensional geometry, size, and other biophysical properties of extracellular vesicles. The developed protocol guides the users in utilizing this analytical tool and outlines the workflow for the analysis of EVs by the AFM, which includes the sample preparation for imaging EVs in hydrated or desiccated form, the electrostatic immobilization of vesicles on a substrate, data acquisition, its analysis, and interpretation. The representative results demonstrate that the fixation of EVs on the modified mica surface is predictable, customizable, and allows the user to obtain sizing results for a large number of vesicles. The vesicle sizing based on the AFM data was found to be consistent with the cryo-TEM imaging.&#160;

A step-by-step procedure is described for label-free immobilization of exosomes and extracellular vesicles from liquid samples and their imaging by atomic force microscopy (AFM). The AFM images are used to estimate the size of the vesicles in the solution and characterize other biophysical properties.&#160;

Imagens de vesículas extracelulares por microscopia de força atômica

Exosomes and other extracellular vesicles (EVs) are molecular complexes consisting of a lipid membrane vesicle, its surface decoration by membrane ...

High-Throughput Total Internal Reflection Fluorescence and Direct Stochastic Optical Reconstruction Microscopy Using a Photonic Chip

Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced contrast due to optical sectioning. The conventional approach is to use high numerical aperture microscope TIRF objectives for both excitation and collection, severely limiting the field of view and throughput. We present a novel approach to generating TIRF excitation for imaging with optical waveguides, called chip-based nanoscopy. The aim of this protocol is to demonstrate how chip-based imaging is performed in an already built setup. The main advantage of chip-based nanoscopy is that the excitation and collection pathways are decoupled. Imaging can then be done with a low magnification lens, resulting in large field of view TIRF images, at the price of a small reduction in resolution. Liver sinusoidal endothelial cells (LSECs) were imaged using direct stochastic optical reconstruction microscopy (dSTORM), showing a resolution comparable to traditional super-resolution microscopes. In addition, we demonstrate the high-throughput capabilities by imaging a 500 &#181;m x 500 &#181;m region with a low magnification lens, providing a resolution of 76 nm. Through its compact character, chip-based imaging can be retrofitted into most common microscopes and can be combined with other on-chip optical techniques, such as on-chip sensing, spectroscopy, optical trapping, etc. The technique is thus ideally suited for high throughput 2D super-resolution imaging, but also offers great opportunities for multi-modal analysis.

Chip-based super-resolution optical microscopy is a novel approach to fluorescence microscopy and offers advantages in cost effectiveness and throughput. Here, the protocols for chip preparation and imaging are shown for TIRF microscopy and localization-based super-resolution microscopy.

Fluorescência de reflexão interna total de alta taxa de transferência e microscopia de reconstrução óptica estocástica direta usando um chip fotônico

Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced ...

A High-Throughput Enzyme-Coupled Activity Assay to Probe Small Molecule Interaction with the dNTPase SAMHD1

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a pivotal regulator of intracellular deoxynucleoside triphosphate (dNTP) pools, as this enzyme can hydrolyze dNTPs into their corresponding nucleosides and inorganic triphosphates. Due to its critical role in nucleotide metabolism, its association to several pathologies, and its role in therapy resistance, intense research is currently being carried out for a better understanding of both the regulation and cellular function of this enzyme. For this reason, development of simple and inexpensive high-throughput amenable methods to probe small molecule interaction with SAMHD1, such as allosteric regulators, substrates, or inhibitors, is vital. To this purpose, the enzyme-coupled malachite green assay is a simple and robust colorimetric assay that can be deployed in a 384-microwell plate format allowing the indirect measurement of SAMHD1 activity. As SAMHD1 releases the triphosphate group from nucleotide substrates, we can couple a pyrophosphatase activity to this reaction, thereby producing inorganic phosphate, which can be quantified by the malachite green reagent through the formation of a phosphomolybdate malachite green complex. Here, we show the application of this methodology to characterize known inhibitors of SAMHD1 and to decipher the mechanisms involved in SAMHD1 catalysis of non-canonical substrates and regulation by allosteric activators, exemplified by nucleoside-based anticancer drugs. Thus, the enzyme-coupled malachite green assay is a powerful tool to study SAMHD1, and furthermore, could also be utilized in the study of several enzymes which release phosphate species.

SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase with critical roles in human health and disease. Here we present a versatile enzyme-coupled SAMHD1 activity assay, deployed in a 384-well microplate format, that allows for the evaluation of small molecules and nucleotide analogues as SAMHD1 substrates, activators, and inhibitors.

Um ensaio de atividade enzimática acoplada de alto rendimento para sondar a interação de pequenas moléculas com a dNTPase SAMHD1

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a pivotal regulator of intracellular deoxynucleoside triphosphate (dNTP) pools, as this ...