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はそのまま生物学的試料のナノスケールイメージングを可能にし、最近の単一分子の超解像顕微鏡技術である間BIFCは、細胞内でのPPIを検出し、可視化するために一般的に使用される技術となっています。手のひらでBIFCの組み合わせは、ナノメートルの空間分解能と単一分子感度で、細胞内のPPIの選択的イメージングを達成しました。 BIFC-PALMは、両方の技術の有用性を拡張し、この作品?...

タンパク質-タンパク質相互作用薬（PPI）は、生物学1の基本である、しっかりと多くの時間と長さスケール全体の時空間的機構を介して調節されています。細胞膜上の細胞シグナル伝達に対する研究は、例えば、特定のPPIおよび細胞プロセス2を容易に動的な、ナノスケール空間区画を明らかにしました。したがって、十分な空間的・時間的解像度、高い特異性、高感度で生物学的システムでのPPIを調査する能力は、生物学のメカニズムの理解を達成するための鍵です。 二分子蛍光相補（BIFC）は、細胞内の分解能でセル内のPPIを可視化するためのいくつかの既存のツールの一つであり、生細胞の互換性3から5 を 。技術は比較的簡単であり、2つの非蛍光フラグメントに蛍光タンパク質の分裂を伴います。遺伝的に2つの相互作用するタンパク質にタグ付けされたときに近接させ、フラグメントは、蛍光シグナルを生じる、完全な蛍光タンパク質を形成するように再構成することができます。適切に設計すると、BIFCプローブは自発的にのPPIの不存在下で再構成してはいけません。このように、BIFCアッセイにおける蛍光シグナルは、高い特異性でのPPIの直接可視化を可能にするのPPIの存在下で生じます。読み出しとして蛍光を使用することのさらなる利点は、とりわけ、高いスループットと高含有量スクリーニングアッセイ、と高感度、細胞内の解像度、および互換性があります。これらの利点のために、異なる親蛍光タンパク質に基づくBIFCプローブの数が開発されています。従来の光学顕微鏡法に基づいて、すべての他の検出手法のように、しかしながら、BIFCの空間分解能は、光の回折による〜250nmのに限定されています。これは、ナノスケールでのPPIの調節を研究するための挑戦になり、先に言及したと脂質ラフト6 aで例示されるようにします、NDラスナノクラスター7は 、そのようなシグナル伝達などの多くの細胞プロセスを理解するための重要な長さスケールです。 BIFCはPPIの10を撮像するための空間分解能でこの制限を克服するために、光活性化ローカライゼーション顕微鏡（PALM）8,9と組み合わされています。 PALMは、確率論的活性化し、単一の蛍光分子のsubdiffractiveローカライズを通じて蛍光イメージングでの回折限界を回避する最近の超解像顕微鏡技術です。各作動サイクルでは、蛍光分子は、数千光子に数百を放射し、検出器上の単一分子の画像を生じます。画像は、回折限界（幅〜250 nm）であるが、その重心は、典型的には、検出された光子の数に応じて10〜50ナノメートルのオーダで、非常に高い精度で判定することができます。試料中の各蛍光分子を活性化し、局在化することにより、高解像度画像を再構成することができます。 Performe生細胞上のD、単一のセル11からのタンパク質の拡散軌跡の数千の単一分子追跡（smt-）PALMさらに許可取得。重要なのは、Palmは確率的な活性化を達成するために、このような光活性化蛍光タンパク質（PA-のFP）などの特殊な蛍光プローブを使用しています。 BIFCとPalm用の蛍光タンパク質の両方ので、それらは、アミノ酸159と160の間に2つの断片に、Palm用PAmCherry1、一般的に使用されるPA-FPを分割して組み合わせました。 分割PAmCherry1に基づいBIFCシステムは、2つの断片の自発的な再構成からの低バックグラウンドシグナルを示しています。遺伝的に相互作用するタンパク質のペアにタグ付けすると、2つの断片を（RN =は1から159残基; RC =メット+残基160から236）であっても37℃、より低い温度でインキュベートすることなく、完全なPAmCherry1タンパク質を形成するために、効率的に再構成し、これそのような親mCherryを13などの他のBIFCペア12には当てはまりません。 Furthermo再、再構成PAmCherry1タンパク質は、高コントラスト比、正確な単一分子の局在化と高解像度のPALM画像化のために重要である他、間中光子収量、高速光活性化、などの親PAmCherry1の光物理的特性を、保持していました。 このプロトコルでは、分割PAmCherry1（ 図1A）を用いて、U2OS細胞中のRas-Rafの相互作用を撮像するBIFC-PALMの使用が記載されています。最初のステップは、PAmCherry1フラグメント（ すなわち 、RN及びRC）と目的タンパク質との間の融合タンパク質を発現するための構築物を設計することです。理論的には、候補タンパク質（A及びB）の対ごとに、融合タンパク質の8組をテストするために存在する：RN-A / RC-B。 RN-A / B-RC。 RC-A / RN-B; RC-A / B-RN; -RN / RC-B; -RN / B-RC。 -RC / RN-B;そしてA-RC / B-RN。このプロセスは、しばしば考慮候補タンパク質の構造的または生化学的特性を取ることによって簡略化することができます。 Rasの場合には、タンパク質であります翻訳後のC末端CAAXボックスで変更された（C =システイン、A =脂肪族; X =任意の）、その後、AAXモチーフが切断されます。したがって、RNまたはRCは、RasのN末端に融合することができます。これは、4つ（ 図1B）への融合タンパク質のペアの数を減少させます。 Rafは、Rasの結合ドメイン（RBD;残基51から131）が使用され、両端にタグを付けることができます。これら4融合構成が生成されました：RN-KRAS / RC-RafのRBD。 RN-KRAS / RafのRBD-RC。 RC-KRAS / RN-RafのRBD。 RC-KRAS / RafのRBD-RN。 さらに、フラグメントおよび目的のタンパク質との間のリンカーを考慮する必要があります。約10アミノ酸の柔軟なリンカーは、しばしば、それが相補性を生じるのに十分な自由度を提供するように使用されます。マルチクローニングサイト（MCS）14から生成されたランダムな配列を含む、正常に適用されてきた多くの人が、ありますが、そのようなリンカーは、（GGGGS）×2です。リンカーの長さはdependin最適化する必要があるかもしれません目的のタンパク質とその向きの相互作用の大きさにグラム。 PAmCherry1断片はのMCSに隣接すると、小さなクローニングバックボーンに含まれている（材料リストを参照してください）​​。目的の遺伝子は、制限部位を介して、またはライゲーション非依存の方法で挿入することができます。クローニングおよび配列確認の後、発現カセットは、リコンビナーゼ反応、高忠実度、高効率のクローニング法を使用して発現ベクターに移されます。 次に、得られた発現構築物は、標的細胞株を感染するためにレンチウイルスにパッケージング、安定な細胞株が所望される場合、標的細胞株にトランスフェクトまたはれています。一過性トランスフェクションは、BIFC構成の迅速な検証を可能にしますが、潜在的な問題に注意する必要があります。化学薬品を使用してトランスフェクションは、多くの場合、高い自己蛍光が得られ、細胞を強調。一方、全内部反射蛍光（TIRF）microscoの使用PPIは、細胞膜上で行われるときpyがTIRF理想、照明量を制限することにより、このバックグラウンド信号を軽減することができます。また、一過性トランスフェクションは、多くの場合、遠くのPPIの検出にアーチファクトを引き起こす可能性がある内因性タンパク質のものを超える、高レベルのタンパク質発現を導きます。したがって、それは、適切なBIFC設定が初期テストを通じて決定された後に安定な細胞株を確立することをお勧めします。安定な細胞株はまた、ドキシサイクリン誘導15を介して調節可能な発現の可能性を有します。 感染後、細胞を、抗生物質、典型的にはピューロマイシン、ネオマイシンで各構築物のための1つの選択されています。試料調製、画像収集、およびデータ分析のための後続のステップは、プロトコールに詳細に説明します。 このアプローチでは、ラス-RafのRBDのBIFC-PALM画像内のナノスケールのクラスターの形成が日常観察される（ 図2A &lt;/強いです&gt;）。一貫して、ラス-RafのRBDのSMT-PALM軌道が拡散状態（ 図2B-D）での不均質な分布を示しています。これらの結果は、Ras-Rafの複合体は、潜在的な生物学的な意味で、おそらくモノマー及びクラスターとして、細胞膜上の複数の状態で存在することを示唆しています。この作業は、従来BIFC、蛍光の共局在化、または蛍光共鳴エネルギー移動（FRET）を用いて得ることが困難となり、ナノメートルの空間分解能および単一分子感度を有する細胞でのPPIの選択的なイメージングにBIFC-PALMのパワーを示しています。 BIFC実験を設計し、その結果を解釈する際には、BIFCプロセスが分割PAmCherry1を含め、ほとんどの場合、中に不可逆的であることを心に留めておくことは重要です。二つの断片を組み合わせて、完全なPAmCherry1タンパク質、二つの断片間の結合を形成し、一旦このように、PPIは永続的になります。これはBIFCとBIFC-PALの使用を制限PPIのダイナミクス（ すなわち 、結合反応速度ではなく、それが形成されると、タンパク質複合体の拡散ダイナミクス）を監視すると、時間にMがあっても、PPI複合体の誤局在につながる可能性があります。 BIFC-PALM実験を設計する際に考慮すべき付加的な要因は、蛍光タンパク質に固有の発色団の成熟の遅れです。 2つのタンパク質が相互作用し、FPのフラグメントが一緒に来たら、彼らは一般的に数秒程度（EYFP 3 60秒のハーフタイム）にリフォールディング。しかし、その後の発色団の成熟と蛍光シグナルが分程度で開発しています。蛍光はスプリット金星、高速折りたたみYFP変異体の再構成後10分以内に検出することができるが、一般的には成熟のためのハーフタイムは、多くの場合、約60分で16です。分割PAmCherry1は、同様の速度を有することが観察されました。したがって、BIFCとBIFC-PALMは現在、リアルタイムのPPIの動態を監視するための悪い選択です。他の私このようなFRETと最近開発された二量体化に依存する蛍光タンパク質17としてthodsは、この目的のために、より適しているかもしれません。

<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.

示さBIFC-PALMの例は、CRAFのラス結合ドメイン（RBD）（ 図1A）との相互作用KRAS G12D変異体です。議論したように、それはRasの膜局在化、ひいては生物学的活性を破壊になるので、RNまたはRCフラグメントは、RasのC末端にタグ付けされていませんでした。これは、8から4（ 図1B）に可能な組み合わせを減少させました。これらの4つの組み合わせの各々は、レンチウイルス感...

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.

二分子蛍光相補性を持つ光活性化ローカライゼーション顕微鏡（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 ビュー.  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. 

ビデオ: 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.

全内部反射蛍光顕微鏡を用いた微生物のCortex組織とダイナミクスの可視化、

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

生物工学

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).

可変角度全内部反射蛍光顕微鏡（VA-TIRFM）の際に、細胞接着のナノトポロジー

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.

蛍光顕微鏡を用いたイメージング細胞遊走用接着剤及び可溶性グラデーションを作成する

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.

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.

単一分子蛍光顕微鏡による受容体ダイナミクスの高分解能時空間解析

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.

細胞内小胞の追跡への応用：変形二光子顕微鏡での3d軌道の追跡

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.

のためのツールと​​してのリポソームカプセル化された近赤外蛍光体の蛍光消光<em&gt;インビボ</em&gt;光学イメージング

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.

平面支持された二分子層​​上の単一分子蛍光顕微鏡

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.

マウス心臓の研究のための光シート蛍光顕微鏡

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.

1 蛍光顕微鏡を用いた複数の画像モードを実施

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