The authors thank Drs. Steven Chu and Joe W. Gray for helpful discussions, Henry Marr for his initial work on the BiFC-PALM project, and Alexis Shoemaker for her technical assistance. This work is supported by startup funds to X.N. from OHSU. Research in the Nan laboratory was also supported by NIH 5U54CA143836-05, the Damon Runyon Cancer Research Foundation, the M. J. Murdock Charitable Trust, and the FEI company.

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The authors have nothing to disclose.

PALM sağlam biyolojik örneklerin nano ölçekli sokulmuşlardır son tek bir molekül superresolution mikroskopi tekniği ise BiFC, tespit ve hücrelerde PPIs görselleştirmek için yaygın olarak kullanılan bir teknik, olmuştur. PALM ile BiFC kombinasyonu nanometre mekansal çözünürlükte ve tek bir molekülün duyarlılığı ile bir hücrenin içinde PPİ seçici görüntüleme elde etti. BiFC PALM her iki tekniğin yararını uzanır ve bu çalışmada gösterildiği gibi, kendi ana hücresel bağlamda PPİ ...

Protein-protein etkileşimleri (PPİ) biyoloji 1 için temel olan ve sıkı birçok zaman ve uzunluk ölçeklerinde genelinde zamanmekansal mekanizmalar üzerinden düzenlenir. Hücre zarı üzerinde hücre sinyal ile ilgili çalışmalar, örneğin, belirli bir PPIs ve hücresel süreçlerin 2 kolaylaştıran dinamik nano ölçekli mekansal bölmeleri göstermektedir. Bu nedenle, yeterli mekansal ve zamansal çözünürlükte, yüksek özgüllük ve yüksek hassasiyet ile biyolojik sistemlerde PPIs prob yeteneği biyoloji mekanistik anlayış ulaşmanın anahtarıdır. 5 - Bimoleküler floresan tamamlama (BiFC) hücre içi çözünürlük ve canlı hücre uyumluluğu 3 bir hücreye PPIs görselleştirmek için birkaç mevcut araçlardan biridir. Tekniği oldukça basit ve iki floresan olmayan parçalara bir floresan proteininin yarma içerir; genetik iki etkileşen proteinlere etiketlendi zaman veyakınına getirildiğinde, fragmanları, flüoresan sinyali verecek şekilde tam bir floresan protein oluşturmak üzere sulandırmak olabilir. Doğru tasarlandığında, BiFC probları kendiliğinden PPİ yokluğunda sulandırmak gerekir. Bunun gibi, bir BiFC tahlilinde floresan sinyali sadece yüksek özgüllük ile PPİ doğrudan görüntülenmesine olanak tanıyan PPİ varlığında ortaya çıkacaktır. Okuma olarak floresan kullanmanın ek yararlar diğerleri arasında yüksek verimlilik ve yüksek içerik tarama deneyleri, yüksek hassasiyet, subsellüler çözünürlük ve uyumluluk. Bu faydalar, farklı üst floresan proteinleri göre BiFC probları bir dizi geliştirilmiştir. Geleneksel ışık mikroskopisi göre tüm diğer algılama teknikleri gibi, ancak, BiFC uzaysal çözünürlüğü ışık difraksiyonu ile ~ 250 nm ile sınırlıdır. Bu lipit sallar 6 a göre daha önce değindiğim ve örneklendiği gibi, nano, at PPİ düzenlenmesini incelemek için bunu bir meydan okuma yaparnd Ras nanokümeler 7, örneğin sinyalizasyon gibi birçok hücresel süreçleri anlamak için kritik bir uzunluk ölçektir. BiFC PPIs 10 görüntülenmesi için mekansal çözünürlükte bu sınırı aşmak için fotoaktive yerelleştirme mikroskobu (PALM) 8,9 ile kombine edilmiştir. PALM stokastik aktivasyonu ve tek flüoresan moleküllerinin subdiffractive lokalizasyonu ile floresan görüntüleme kırınım sınırı atlatır son superresolution mikroskopi tekniğidir. Her bir aktivasyon çevriminde, bir flüoresan molekül birkaç bin fotonlara birkaç yüz verir ve dedektör üzerinde tek bir molekülün bir görüntüye yol açmaktadır. Görüntü kırınım sınırlı olsa da (~ genişliği 250 nm) olarak, ağırlık merkezi, tipik olarak tespit edilen fotonların sayısına bağlı olarak 10-50 nm mertebesinde, daha yüksek hassasiyet ile tespit edilebilir. Aktive ve numunedeki her floresan molekülü lokalize ederek, yüksek çözünürlüklü bir görüntü yeniden inşa edilebilir. Performecanlı hücreler üzerinde d tek bir hücreden 11 protein difüzyon yörüngeleri binlerce tek bir molekül izleme (smt-) PALM ileri izin edinimi. Önemlisi, PALM stokastik aktivasyonunu elde etmek için bu tür ışıkla aktive floresan proteinleri (PA-FP) gibi özel flüoresan millerini kullanır. BiFC ve PALM kullanım floresan proteinleri hem beri onlar amino asitler 159 ve 160 arasında iki parça halinde, PALM için PAmCherry1, yaygın olarak kullanılan bir PA-FP bölerek kombine edilmiştir. Bölünmüş PAmCherry1 dayalı BiFC sistemi iki parçalarının kendiliğinden sulandırıldıktan düşük arka plan sinyalini gösterir. Genetik olarak etkileşen proteinlerin bir çift etiketli, iki fragman (RN = 1-159 kalıntıları RC = Met + kalıntıları 160-236) da 37 ° C &#39;de ve daha düşük sıcaklıklarda kuluçkaya olmadan PAmCherry1 proteinleri oluşturmak için etkin bir şekilde yeniden, burada Böyle ebeveyn mCherry 13 gibi diğer BiFC çiftleri 12 için durum böyle değil. Furthermoyeniden yeniden PAmCherry1 proteini gibi doğru tek bir molekül lokalizasyonu ve yüksek çözünürlüklü PALM görüntüleme için kritik olan diğerleri arasında yüksek kontrast oranı, orta foton verimi ve hızlı fotoaktivasyon gibi ana PAmCherry1 ait Fotofiziksel özelliklerini korudu. Bu protokolde, split PAmCherry1 (Şekil 1A) kullanarak U2OS hücrelerinde Ras-Raf etkileşimlerini görüntüleme için BiFC PALM kullanılması tarif edilmektedir. İlk adım PAmCherry1 fragmanları (örneğin, RN ve Re) ve ilgili proteinler arasındaki füzyon proteinleri ifade etmek için yapıları tasarlamaktır. Teorik olarak, aday protein (A ve B) her çifti için, füzyon proteinlerinin sekiz çifti, test edilecek vardır: RN-A / RC-B; RN-A / B-RC; RC-A / RN-B; RC-A / B-RN; A-RN / RC-B; A-RN / B-RC; A-RC / RN-B; ve A-RC / B-RN. Bu süreç genellikle dikkate aday proteinlerin yapısal veya biyokimyasal özellikleri alarak basitleştirilmiş olabilir. Ras&#39;ın bir durumda, proteintranslasyon sonrası C-terminal CAAX kutusunun modifiye (C = Cys; A = alifatik, X = herhangi bir), ve bundan sonra AAX motifi kesilir. Bu nedenle, RN RC yalnızca Ras&#39;ın N-terminine kaynaşmış olabilir; Bu dört (Şekil 1B), füzyon proteini çiftlerinin sayısını azaltır. Raf için domain Ras bağlayıcı (RBD; artıkları 51-131) kullanılır ve her iki uçta etiketlenmiş olabilir. Bu dört füzyon konfigürasyonları elde edilmiştir: RN-Kras / RC-Raf RBD; RN-Kras / Raf RBD-RC; RC-Kras / RN-Raf RBD; ve RC-KRAS / Raf RBD-RN. Buna ek olarak, fragmanlar ve ilgi proteinleri arasındaki bağlayıcı olarak kabul edilmesi gerekir. Yaklaşık on amino asit esnek bir bağlayıcı genellikle tamamlama oluşması için yeterli özgürlüğü sağlar olarak kullanılır. Çoklu bir klonlama bölgesinin (MCS) 14 elde edilen rasgele diziler dahil olmak üzere, başarılı bir şekilde uygulanmıştır diğerleri, olmasına rağmen böyle bir bağlayıcı (GGGGS) x2. Bağlayıcıların uzunluğu dependin optimize edilmesi gerekebilirilgi proteinlerin ve yönelimleri etkileşim boyutuna g. PAmCherry1 fragmanları MCSS yan küçük bir klonlama omurgası içerdiği (Malzeme listesi). Söz konusu genler sınırlama siteleri yoluyla, ya da bir ligasyon bağımsız yöntemi ile yerleştirilebilir. Klonlama ve Sekans doğrulama sonrasında, ekspresyon kaseti, bir yeniden bağlayıcı reaksiyonlar, yüksek aslına uygunluk ve yüksek verimlilik ile bir klonlama işlemi kullanılarak bir ekspresyon vektörüne transfer edilir. Daha sonra, elde edilen sentezleme konstruktları hedef hücre hattı enfekte etmek için sabit bir hücre serisi isteniyorsa, lentivirüs içine paketlenmiş, hedef hücre hattına transfekte veya edilir. Geçici transfeksiyon BiFC yapılandırmasının hızlı doğrulama için sağlar, ancak potansiyel problemler dikkat edilmelidir. Genellikle kimyasallar kullanarak Transfeksiyon yüksek otofloresans sonuçlanan hücreleri vurgular; ise toplam iç yansıma floresan (TIRF) mikroskobik kullanımıpy PPİ hücre zarındaki yer alırken aydınlatma hacmi, TIRF idealini sınırlayarak bu arka plan sinyalini azaltmak olabilir. Buna ek olarak, geçici nakiller genellikle çok PPIs saptanmasında eserler neden endojen proteinlerin aşan, protein ekspresyonunun yüksek seviyeleri yol açar. Bu nedenle, uygun bir BiFC yapılandırması ilk test ile belirlenmiştir sonra kararlı hücre soyları kurulmuştur önerilir. Stabil hücre hatları da doksisiklin indüksiyonu 15 vasıtasıyla ayarlanabilir ekspresyon için potansiyele sahiptir. Enfeksiyondan sonra, hücreler tipik haliyle puromisin ve her bir yapı için neomisin, bir antibiyotik kullanılarak seçilir. Numune hazırlama, görüntü elde etme ve veri analizi için bir sonraki adım protokoller detaylı olarak tarif edilecektir. Bu yaklaşımla, Ras-Raf RBD BiFC PALM görüntülerde nano kümelerin oluşumu rutin görülmektedir (Şekil 2A &lt;/ strong&gt;). Sürekli, Ras-Raf RBD smt-PALM yörüngeleri difüzyon devletler (Şekil 2B-D) heterojen bir dağılım gösterir. Bu sonuçlar, Ras-Raf kompleksleri potansiyel biyolojik etkileri olan, muhtemelen monomerlerin ve kümeleri gibi, hücre zarı üzerinde birden fazla eyalette mevcut olduğunu göstermektedir. Bu çalışma, geleneksel BiFC, floresan co-lokalizasyon veya floresan rezonans enerji transferi (FRET) ile elde etmek zor olurdu nanometre uzamsal çözünürlük ve tek bir molekülün duyarlılık, hücrelerin içinde PPİ seçici görüntülenmesinde BiFC PALM gücünü gösteriyor. BiFC deneyler tasarlama ve sonuçları yorumlama, bu BiFC süreci bölünmüş PAmCherry1 dahil çoğu durumda, geri dönüşümsüz akılda tutmak önemlidir. Iki parça bir araya ve tam bir PAmCherry1 protein, iki parça arasındaki bağlantı oluşturabilir ve sonra bu şekilde PPI kalıcı olur. Bu BiFC ve BiFC-PAL kullanımını sınırlamaktadırPPI dinamiklerini (örneğin, bağlayıcı bir kinetik olup oluşturulduğu bir kez protein kompleksinin difüzyon dinamikleri) izlenmesi için ve zaman zaman M da PPI komplekslerinin mislocalization yol açabilir. BiFC PALM deney tasarlama floresan proteinleri doğasında vardır kromofor olgunlaşmasında gecikme olduğunda ek bir faktör dikkate. İki protein etkileşim ve FP fragmanları bir araya gelip, onlar genellikle saniye (EYFP 3 60 saniyelik yarı zamanlı) mertebesinde yeniden katlayın. Ancak, sonraki kromofor olgunlaşma ve flüoresan sinyal dakika mertebesinde gelişir. Floresan bölünmüş Venüs, hızlı bir katlama YFP varyant sulandırılmasından sonra 10 dakika içinde tespit edilebilir iken, genel olarak olgunlaşması için yarı-zamanı genellikle yaklaşık 60 dakika 16. Split-PAmCherry1 benzer fiyat bilgisi gözlendi. Dolayısıyla, BiFC ve BiFC PALM gerçek zamanlı ÜFE kinetiği izlemek için şu anda kötü seçimlerdir; Diğer meörneğin FRET ve yeni geliştirilmiş bir dimerizasyon bağlı floresan proteini 17 gibi thods, bu amaç için daha uygun olabilir.

<table>
	<tbody>
		<tr>
			<td>TIRF Microscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>60X oil immersion TIRF objective with 1.49 NA</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>EMCCD camera</td>
			<td>Andor</td>
			<td>iXon Ultra 897</td>
			<td></td>
		</tr>
		<tr>
			<td>561 nm laser</td>
			<td>Coherent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>405 nm laser</td>
			<td>Coherent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>561 nm dichroic mirror</td>
			<td>Semrock</td>
			<td>&#160;Di01-R405/488/561/635-25x36</td>
			<td></td>
		</tr>
		<tr>
			<td>561 nm filter</td>
			<td>Semrock</td>
			<td>FF01-525/45-25</td>
			<td></td>
		</tr>
		<tr>
			<td>405/561 nm notch filter</td>
			<td>Semrock</td>
			<td>NF01-405/488/568-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature and CO2 controlled stage</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pENTR-D-TOPO-PAmCherry1_1-159-MCS</td>
			<td>Addgene</td>
			<td>60545</td>
			<td></td>
		</tr>
		<tr>
			<td>pENTR-D-TOPO-PAmCherry160-236-MCS</td>
			<td>Addgene</td>
			<td>60546</td>
			<td></td>
		</tr>
		<tr>
			<td>pcDNA3.2-DEST</td>
			<td>Life Technologies</td>
			<td>12489-019</td>
			<td></td>
		</tr>
		<tr>
			<td>pLenti-DEST</td>
			<td>Addgene</td>
			<td></td>
			<td>http://www.addgene.org/Eric_Campeau/</td>
		</tr>
		<tr>
			<td>Phusion High-Fidelity DNA Polymerase</td>
			<td>Thermo Scientific</td>
			<td>F-531</td>
			<td></td>
		</tr>
		<tr>
			<td>In-Fusion HD Cloning</td>
			<td>Clontech</td>
			<td>639649</td>
			<td></td>
		</tr>
		<tr>
			<td>LR Clonase</td>
			<td>Life Technologies</td>
			<td>11791</td>
			<td></td>
		</tr>
		<tr>
			<td>Vira Power Lentivirus Packaging</td>
			<td>Life Technologies</td>
			<td>K497500</td>
			<td></td>
		</tr>
		<tr>
			<td>X-tremeGENE Transfection Reagent</td>
			<td>Roche</td>
			<td>13873800</td>
			<td></td>
		</tr>
		<tr>
			<td>Lab-Tek II Chambered Coverglass</td>
			<td>Thermo Scientific</td>
			<td>155409</td>
			<td>#1.5 glass bottom dishes</td>
		</tr>
		<tr>
			<td>U2OS cells</td>
			<td>ATCC</td>
			<td>HTB-96</td>
			<td></td>
		</tr>
		<tr>
			<td>293T/17 cells</td>
			<td>ATCC</td>
			<td>CRL-11268</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM with phenol red</td>
			<td>Life Technologies</td>
			<td>11995</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM no phenol red</td>
			<td>Life Technologies</td>
			<td>21063</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Life Technologies</td>
			<td>10082</td>
			<td></td>
		</tr>
		<tr>
			<td>Leibovit&#39;s L-15, no phenol red</td>
			<td>Life Technologies</td>
			<td>21083-027</td>
			<td></td>
		</tr>
		<tr>
			<td>Reduced serum medium</td>
			<td>Life Technologies</td>
			<td>31985</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline</td>
			<td>Life Technologies</td>
			<td>14040</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>BD Biosciences</td>
			<td>309604</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe filter</td>
			<td>Millipore</td>
			<td>SLHV033RB</td>
			<td></td>
		</tr>
		<tr>
			<td>Lentiviral concentrator</td>
			<td>Clontech</td>
			<td>631231</td>
			<td></td>
		</tr>
		<tr>
			<td>Retroviral concentrator</td>
			<td>Clontech</td>
			<td>631455</td>
			<td></td>
		</tr>
		<tr>
			<td>10 cm culture dish</td>
			<td>BD Biosciences</td>
			<td>353003</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well culture plate</td>
			<td>BD Biosciences</td>
			<td>353046</td>
			<td></td>
		</tr>
		<tr>
			<td>Polybrene</td>
			<td>Sigma</td>
			<td>107689</td>
			<td></td>
		</tr>
		<tr>
			<td>Puromycin</td>
			<td>Life Technologies</td>
			<td>A11138</td>
			<td></td>
		</tr>
		<tr>
			<td>G-418</td>
			<td>Calbiochem</td>
			<td>345812</td>
			<td>Neomycin</td>
		</tr>
		<tr>
			<td>Doxycyline</td>
			<td>Fisher</td>
			<td>BP2653</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Fisher</td>
			<td>BP152</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma</td>
			<td>EDS</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Hydroxide</td>
			<td>Sigma</td>
			<td>S5881</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutaraldehyde</td>
			<td>Sigma</td>
			<td>G6257</td>
			<td></td>
		</tr>
		<tr>
			<td>PIPES</td>
			<td>Sigma</td>
			<td>P6757</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H4034</td>
			<td></td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Sigma</td>
			<td>3777</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium Sulfate</td>
			<td>Sigma</td>
			<td>M2643</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Hydroxide</td>
			<td>Sigma</td>
			<td>221473</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Fisher</td>
			<td>BP358</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride</td>
			<td>Fisher</td>
			<td>M33</td>
			<td></td>
		</tr>
		<tr>
			<td>100 nm gold particles</td>
			<td>BBI Solutions</td>
			<td>EM.GC100</td>
			<td></td>
		</tr>
		<tr>
			<td>Molecular grade water</td>
			<td>Life Technologies</td>
			<td>10977</td>
			<td></td>
		</tr>
		<tr>
			<td>Dpn1</td>
			<td>New England Biolabs</td>
			<td>R0176</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR purification kit</td>
			<td>Qiagen</td>
			<td>28104</td>
			<td></td>
		</tr>
		<tr>
			<td>Miniprep kit</td>
			<td>Qiagen</td>
			<td>27104</td>
			<td></td>
		</tr>
		<tr>
			<td>Midiprep kit</td>
			<td>Macherey-Nagel</td>
			<td>740410</td>
			<td></td>
		</tr>
		<tr>
			<td>0.6 mL microcentrifuge tubes</td>
			<td>Fisher</td>
			<td>05-408-120</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL microcentrifuge tubes</td>
			<td>Fisher</td>
			<td>05-408-137</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL tubes</td>
			<td>Fisher</td>
			<td>05-539-12</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL&#160; polypropylene round-bottom tubes</td>
			<td>BD Biosciences</td>
			<td>352063</td>
			<td></td>
		</tr>
		<tr>
			<td>14 mL polypropylene round-bottom tubes</td>
			<td>BD Biosciences</td>
			<td>352059</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL tube</td>
			<td>BD Biosciences</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR tube</td>
			<td>GeneMate</td>
			<td>C-3328-1</td>
			<td></td>
		</tr>
		<tr>
			<td>SOC medium</td>
			<td>Life Technologies</td>
			<td>15544</td>
			<td></td>
		</tr>
		<tr>
			<td>LB broth</td>
			<td>BD Biosciences</td>
			<td>244610</td>
			<td></td>
		</tr>
		<tr>
			<td>Kanamycin sulfate</td>
			<td>Fisher</td>
			<td>BP906</td>
			<td></td>
		</tr>
		<tr>
			<td>Competent cells</td>
			<td>Life Technologies</td>
			<td>C4040</td>
			<td></td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>Mathworks</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

photoactivated localization microscopy with bimolecular fluorescence complementation (bifc-palm)

Protein-protein interactions (PPIs) are key molecular events to biology. However, it remains a challenge to visualize PPIs with sufficient resolution and sensitivity in cells because the resolution of conventional light microscopy is diffraction-limited to ~250 nm. By combining bimolecular fluorescence complementation (BiFC) with photoactivated localization microscopy (PALM), PPIs can be visualized in cells with single molecule sensitivity and nanometer spatial resolution. BiFC is a commonly used technique for visualizing PPIs with fluorescence contrast, which involves splitting of a fluorescent protein into two non-fluorescent fragments. PALM is a recent superresolution microscopy technique for imaging biological samples at the nanometer and single molecule scales, which uses phototransformable fluorescent probes such as photoactivatable fluorescent proteins (PA-FPs). BiFC-PALM was demonstrated by splitting PAmCherry1, a PA-FP compatible with PALM, for its monomeric nature, good single molecule brightness, high contrast ratio, and utility for stoichiometry measurements. When split between amino acids 159 and 160, PAmCherry1 can be made into a BiFC probe that reconstitutes efficiently at 37 &#176;C with high specificity to PPIs and low non-specific reconstitution. Ras-Raf interaction is used as an example to show how BiFC-PALM helps to probe interactions at the nanometer scale and with single molecule resolution. Their diffusion can also be tracked in live cells using single molecule tracking (smt-) PALM. In this protocol, factors to consider when designing the fusion proteins for BiFC-PALM are discussed, sample preparation, image acquisition, and data analysis steps are explained, and a few exemplary results are showcased. Providing high spatial resolution, specificity, and sensitivity, BiFC-PALM is a useful tool for studying PPIs in intact biological samples.

Gösterilen BiFC PALM örnek Craf etki (RBD) (Şekil 1A) bağlayıcı Ras ile etkileşim Kras G12D mutant olduğunu. Tartışıldığı gibi Ras zar lokalizasyonu ve dolayısıyla biyolojik aktivitesini bozacak, çünkü, RN veya RC fragmanları Ras&#39;ın C-terminaline etiketlenmemiş. Bu dört (Şekil 1B) sekizden olası kombinasyonları azalır. Bu dört kombinasyon her lentiviral enfeksiyonu ile U2OS hücrelerine dahil edilmiştir. Protokolde ayrıntılı olarak hücreler sabitlend...

Watch this Scientific Journal Video about Photoactivated Localization Microscopy with Bimolecular Fluorescence Complementation BiFC-PALM at JoVE.com

Photoactivated Localization Microscopy with Bimolecular Fluorescence Complementation BiFC-PALM

Protein-protein interactions are visualized in cells with nanometer spatial resolution by combining bimolecular fluorescence complementation (BiFC) with photoactivated localization microscopy (PALM). Described here is the use of BiFC-PALM for imaging Ras-Raf interactions in U2OS cells for visualizing the nanoscale clustering and diffusion of individual Ras-Raf complexes.

Bimoleküler Floresan tamamlama ile fotoaktive Yerelleştirme Mikroskobu (BiFC-PALM)

Protein-protein interactions (PPIs) are key molecular events to biology. However, it remains a challenge to visualize PPIs with sufficient resolution and ...

photoactivated-localization-microscopy-with-bimolecular-fluorescence

Research

JoVE Journal

Bioengineering

Photoactivated Localization Microscopy with Bimolecular Fluorescence Complementation (BiFC-PALM)

9.8K Görüntüleme.  Oregon Health and Science University. Protein-protein interactions are visualized in cells with nanometer spatial resolution by combining bimolecular fluorescence complementation (BiFC) with photoactivated localization microscopy (PALM). Described here is the use of BiFC-PALM for imaging Ras-Raf interactions in U2OS cells for visualizing the nanoscale clustering and diffusion of individual Ras-Raf complexes. 

Video: Photoactivated Localization Microscopy with Bimolecular Fluorescence Complementation BiFC-PALM

Visualization of Cortex Organization and Dynamics in Microorganisms, using Total Internal Reflection Fluorescence Microscopy

TIRF microscopy has emerged as a powerful imaging technology to study spatio-temporal dynamics of fluorescent molecules in vitro and in living cells1. The optical phenomenon of total internal reflection occurs when light passes from a medium with high refractive index into a medium with low refractive index at an angle larger than a characteristic critical angle (i.e. closer to being parallel with the boundary). Although all light is reflected back under such conditions, an evanescent wave is created that propagates across and along the boundary, which decays exponentially with distance, and only penetrates sample areas that are 100-200 nm near the interface2. In addition to providing superior axial resolution, the reduced excitation of out of focus fluorophores creates a very high signal to noise ratios and minimizes damaging effects of photobleaching2,3. Being a widefield technique, TIRF also allows faster image acquisition than most scanning based confocal setups.
At first glance, the low penetration depth of TIRF seems to be incompatible with imaging of bacterial and fungal cells, which are often surrounded by thick cell walls. On the contrary, we have found that the cell walls of yeast and bacterial cells actually improve the usability of TIRF and increase the range of observable structures4-8. Many cellular processes can therefore be directly accessed by TIRF in small, single-cell microorganisms, which often offer powerful genetic manipulation techniques. This allows us to perform in vivo biochemistry experiments, where kinetics of protein interactions and activities can be directly assessed in living cells.
We describe here the individual steps required to obtain high quality TIRF images for Saccharomyces cerevisiae or Bacillus subtilis cells. We point out various problems that can affect TIRF visualization of fluorescent probes in cells and illustrate the procedure with several application examples. Finally, we demonstrate how TIRF images can be further improved using established image restoration techniques.

Total Internal Reflection Fluorescence (TIRF) microscopy is a powerful approach to observe structures close to the cell surface at high contrast and temporal resolution. We demonstrate how TIRF can be employed to study protein dynamics at the cortex of cell wall-enclosed bacterial and fungal cells.

Mikroorganizmalarda Cortex Organizasyon ve Dinamiği Görselleştirme, Toplam İç Yansıma Floresan Mikroskobu kullanılarak

TIRF microscopy has emerged as  a powerful imaging technology to study spatio-temporal dynamics of fluorescent molecules  in vitro and in living cells1. ...

Biyomühendislik

Nanotopology of Cell Adhesion upon Variable-Angle Total Internal Reflection Fluorescence Microscopy (VA-TIRFM)

Surface topology, e.g. of cells growing on a substrate, is determined with nanometer precision by Variable-Angle Total Internal Reflection Fluorescence Microscopy (VA-TIRFM). Cells are cultivated on transparent slides and incubated with a fluorescent marker homogeneously distributed in their plasma membrane. Illumination occurs by a parallel laser beam under variable angles of total internal reflection (TIR) with different penetration depths of the evanescent electromagnetic field. Recording of fluorescence images upon irradiation at about 10 different angles permits to calculate cell-substrate distances with a precision of a few nanometers. Differences of adhesion between various cell lines, e.g. cancer cells and less malignant cells, are thus determined. In addition, possible changes of cell adhesion upon chemical or photodynamic treatment can be examined. In comparison with other methods of super-resolution microscopy light exposure is kept very small, and no damage of living cells is expected to occur.

Nanotopology of Cell Adhesion upon Variable-Angle Total Internal Reflection Fluorescence Microscopy VA-TIRFM

Topology of cell adhesion on a substrate is measured with nanometre precision by variable-angle total internal reflection fluorescence microscopy (VA-TIRFM).

Değişken Açılı Toplam İç Yansıma Floresan Mikroskopi (VA-TIRFM) üzerine Hücre yapışma Nanotopology

Surface topology, e.g. of cells growing on a substrate, is determined with nanometer precision by Variable-Angle Total Internal Reflection Fluorescence ...

Creating Adhesive and Soluble Gradients for Imaging Cell Migration with Fluorescence Microscopy

Cells can sense and migrate towards higher concentrations of adhesive cues such as the glycoproteins of the extracellular matrix and soluble cues such as growth factors. Here, we outline a method to create opposing gradients of adhesive and soluble cues in a microfluidic chamber, which is compatible with live cell imaging. A copolymer of poly-L-lysine and polyethylene glycol (PLL-PEG) is employed to passivate glass coverslips and prevent non-specific adsorption of biomolecules and cells. Next, microcontact printing or dip pen lithography are used to create tracks of streptavidin on the passivated surfaces to serve as anchoring points for the biotinylated peptide arginine-glycine-aspartic acid (RGD) as the adhesive cue. A microfluidic device is placed onto the modified surface and used to create the gradient of adhesive cues (100% RGD to 0% RGD) on the streptavidin tracks. Finally, the same microfluidic device is used to create a gradient of a chemoattractant such as fetal bovine serum (FBS), as the soluble cue in the opposite direction of the gradient of adhesive cues.

A method for the assembly of adhesive and soluble gradients in a microscopy chamber for live cell migration studies is described. The engineered environment combines antifouling surfaces and adhesive tracks with solution gradients and therefore allows one to determine the relative importance of guidance cues.

Floresan Mikroskobu ile Görüntüleme Hücre Göç Yapıştırıcı ve Çözünür Degradeler oluşturma

Cells can sense and migrate towards higher concentrations of adhesive cues such as the glycoproteins of the extracellular matrix and soluble cues such as ...

Localization and Relative Quantification of Carbon Nanotubes in Cells with Multispectral Imaging Flow Cytometry

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich cell structures and de facto there is still no quantitative method to assess their distribution at cell and tissue levels. What we propose here is an innovative method allowing the detection and quantification of CNTs in cells using a multispectral imaging flow cytometer (ImageStream, Amnis). This newly developed device integrates both a high-throughput of cells and high resolution imaging, providing thus images for each cell directly in flow and therefore statistically relevant image analysis. Each cell image is acquired on bright-field (BF), dark-field (DF), and fluorescent channels, giving access respectively to the level and the distribution of light absorption, light scattered and fluorescence for each cell. The analysis consists then in a pixel-by-pixel comparison of each image, of the 7,000-10,000 cells acquired for each condition of the experiment. Localization and quantification of CNTs is made possible thanks to some particular intrinsic properties of CNTs: strong light absorbance and scattering; indeed CNTs appear as strongly absorbed dark spots on BF and bright spots on DF with a precise colocalization.
This methodology could have a considerable impact on studies about interactions between nanomaterials and cells given that this protocol is applicable for a large range of nanomaterials, insofar as they are capable of absorbing (and/or scattering) strongly enough the light.

In this study, the main purpose was to monitor the cellular uptake and eventual exocytosis of carbon nanotubes (CNTs). From this perspective, we proposed here a unique method using multispectral imaging flow cytometry allowing a quantification and localization of CNTs in a statistically relevant number of cells.

Çokspektrumlu Görüntüleme Sitometrisi ile Hücreleri yerelleştirme ve Karbon nanotüpler Bağıl Kantitasyonu

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich ...

High-resolution Spatiotemporal Analysis of Receptor Dynamics by Single-molecule Fluorescence Microscopy

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., kinetics, coexistence of different states and populations, transient interactions), which are typically hidden in ensemble measurements, such as those obtained with standard biochemical or microscopy methods. Thus, dynamic events, such as receptor-receptor interactions, can be followed in real time in a living cell with high spatiotemporal resolution. This protocol describes a method based on labeling with small and bright organic fluorophores and total internal reflection fluorescence (TIRF) microscopy to directly visualize single receptors on the surface of living cells. This approach allows one to precisely localize receptors, measure the size of receptor complexes, and capture dynamic events such as transient receptor-receptor interactions. The protocol provides a detailed description of how to perform a single-molecule experiment, including sample preparation, image acquisition and image analysis. As an example, the application of this method to analyze two G-protein-coupled receptors, i.e., &#946;2-adrenergic and &#947;-aminobutyric acid type B (GABAB) receptor, is reported. The protocol can be adapted to other membrane proteins and different cell models, transfection methods and labeling strategies.

This protocol describes how to use total internal reflection fluorescence microscopy to visualize and track single receptors on the surface of living cells and thereby analyze receptor lateral mobility, size of receptor complexes as well as to visualize transient receptor-receptor interactions. This protocol can be extended to other membrane proteins.

Tek molekül Floresan Mikroskopi Reseptör Dinamiği Yüksek çözünürlüklü Spatiotemporal Analizi

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., ...

3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a modified two-photon microscope1. As opposed to conventional approaches (raster scan or wide field based on a stack of frames), the 3D orbital tracking allows to localize and follow with a high spatial (10 nm accuracy) and temporal resolution (50 Hz frequency response) the 3D displacement of a moving fluorescent particle on length-scales of hundreds of microns2. The method is based on a feedback algorithm that controls the hardware of a two-photon laser scanning microscope in order to perform a circular orbit around the object to be tracked: the feedback mechanism will maintain the fluorescent object in the center by controlling the displacement of the scanning beam3-5. To demonstrate the advantages of this technique, we followed a fast moving organelle, the lysosome, within a living cell6,7. Cells were plated according to standard protocols, and stained using a commercially lysosome dye. We discuss briefly the hardware configuration and in more detail the control software, to perform a 3D orbital tracking experiment inside living cells. We discuss in detail the parameters required in order to control the scanning microscope and enable the motion of the beam in a closed orbit around the particle. We conclude by demonstrating how this method can be effectively used to track the fast motion of a labeled lysosome along microtubules in 3D within a live cell. Lysosomes can move with speeds in the range of 0.4-0.5 &#181;m/sec, typically displaying a directed motion along the microtubule network8.

In this video protocol we track - at high speed and in three dimensions - fluorescently labeled lysosomes within living cells, using the orbital tracking method in a modified two-photon microscope.

Modifiye İki foton mikroskop 3D Orbital Takip: Hücre içi veziküllerin İzlemeye Bir Uygulama

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a ...

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

The use of fluorophores for in vivo imaging can be greatly limited by opsonization, rapid clearance, low detection sensitivity and cytotoxic effects on the host. Encapsulation of fluorophores in liposomes by film hydration and extrusion leads to fluorescence quenching and protection which enables in vivo imaging with high detection sensitivity.

Aracı Olarak bir lipozomal-kapsüllü Yakın-Kızılötesi floroforun Floresan-söndürme<em&gt; İn Vivo</em&gt; Optik Görüntüleme

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous ...

Single Molecule Fluorescence Microscopy on Planar Supported Bilayers

In the course of a single decade single molecule microscopy has changed from being a secluded domain shared merely by physicists with a strong background in optics and laser physics to a discipline that is now enjoying vivid attention by life-scientists of all venues 1. This is because single molecule imaging has the unique potential to reveal protein behavior in situ in living cells and uncover cellular organization with unprecedented resolution below the diffraction limit of visible light 2. Glass-supported planar lipid bilayers (SLBs) are a powerful tool to bring cells otherwise growing in suspension in close enough proximity to the glass slide so that they can be readily imaged in noise-reduced Total Internal Reflection illumination mode 3,4. They are very useful to study the protein dynamics in plasma membrane-associated events as diverse as cell-cell contact formation, endocytosis, exocytosis and immune recognition. Simple procedures are presented how to generate highly mobile protein-functionalized SLBs in a reproducible manner, how to determine protein mobility within and how to measure protein densities with the use of single molecule detection. It is shown how to construct a cost-efficient single molecule microscopy system with TIRF illumination capabilities and how to operate it in the experiment.

Preparation of protein-functionalized planar glass-supported lipid bilayers, determination of protein mobility within and measurement of protein densities is shown here. A roadmap to building a noise-reduced Total Internal Reflection microscope is outlined, which allows visualizing single bilayer-resident fluorochromes with high spatiotemporal resolution.

Planar on Tek Molekül Floresans Mikroskopi bilayers Desteklenen

In the course of a single decade single molecule microscopy has changed from being a secluded domain shared merely by physicists with a strong background ...

Light-sheet Fluorescence Microscopy for the Study of the Murine Heart

Light-sheet fluorescence microscopy has been widely used for rapid image acquisition with a high axial resolution from micrometer to millimeter scale. Traditional light-sheet techniques involve the use of a single illumination beam directed orthogonally at sample tissue. Images of large samples that are produced using a single illumination beam contain stripes or artifacts and suffer from a reduced resolution due to the scattering and absorption of light by the tissue. This study uses a dual-sided illumination beam and a simplified CLARITY optical clearing technique for the murine heart. These techniques allow for deeper imaging by removing lipids from the heart and produce a large field of imaging, greater than 10 x 10 x 10 mm3. As a result, this strategy enables us to quantify the ventricular dimensions, track the cardiac lineage, and localize the spatial distribution of cardiac-specific proteins and ion-channels from the post-natal to adult mouse hearts with sufficient contrast and resolution.

This study uses a dual-sided illumination light-sheet fluorescence microscopy (LSFM) technique combined with optical clearing to study the murine heart.

Fare kalp çalışma için ışık sayfalık floresans mikroskobu

Light-sheet fluorescence microscopy has been widely used for rapid image acquisition with a high axial resolution from micrometer to millimeter scale. ...

Conducting Multiple Imaging Modes with One Fluorescence Microscope

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to conventional epi-fluorescence microscopy, various imaging techniques have been developed to achieve specific experimental goals. Some of the widely used techniques include single-molecule fluorescence resonance energy transfer (smFRET), which can report conformational changes and molecular interactions with angstrom resolution, and single-molecule detection-based super-resolution (SR) imaging, which can enhance the spatial resolution approximately ten&#160;to twentyfold compared to diffraction-limited microscopy. Here we present a customer-designed integrated system, which merges multiple imaging methods in one microscope, including conventional epi-fluorescent imaging, single-molecule detection-based SR imaging, and multi-color single-molecule detection, including smFRET imaging. Different imaging methods can be achieved easily and reproducibly by switching optical elements. This set-up is easy to adopt by any research laboratory in biological sciences with a need for routine and diverse imaging experiments at a reduced cost and space relative to building separate microscopes for individual purposes.

Here we present a practical guide of building an integrated microscopy system, which merges conventional epi-fluorescent imaging, single-molecule detection-based super-resolution imaging, and multi-color single-molecule detection, including single-molecule fluorescence resonance energy transfer imaging, into one set-up in a cost-efficient way.

Çoklu görüntüleme modları bir floresan mikroskop ile iletken

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to ...