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 그대로 생체 시료의 나노 이미징을 가능하게하는 최근 단일 분자 수퍼 해상도 현미경 기법 동안 BiFC는 검출 셀에서 프로톤 펌프 억제제를 시각화 기술에 일반적으로 사용되어왔다. 손바닥 BiFC의 조합은 나노 미터 공간 해상도와 단일 분자 감도 세포 내에서 프로톤 펌프 억제제의 선택 영상을 달성했다. BiFC-PALM은 두 가지 기술의 유틸리티를 확장하고,이 연구에서 입증 된 바와 같이, 그 나라의 ...

단백질 - 단백질 상호 작용 (프로톤 펌프 억제제)는 생물학 1 기본적인 단단히 많은 시간과 길이 스케일에서 시공간 메커니즘을 통해 조절된다. 세포막 시그널링 세포에 관한 연구는 예를 들어, 특정 프로톤 펌프 억제제 및 세포 과정 (2)을 용이하게 동적 나노 스케일 공간 구획을 밝혀냈다. 따라서, 충분한 공간 및 시간 해상도, 높은 특이성 및 고감도 생물학적 시스템에서 프로톤 펌프 억제제를 검사 할 수있는 능력은 생물의 기계적 이해를 달성하기위한 키이다. 5 - 이분자 형광 보완 (BiFC)는 세포 내 해상도와 라이브 셀 호환성 3 셀에 프로톤 펌프 억제제를 시각화에 대한 몇 가지 기존 도구 중 하나입니다. 이 기술은 비교적 간단하고 두 비 형광 조각으로 형광 단백질의 분리를 포함한다; 유전자 두 개의 상호 작용하는 단백질에 태그 때근접하게, 단편은 형광 신호를 산출 완전한 형광 단백질을 형성하도록 재구성 할 수있다. 적절하게 설계하면 BiFC 프로브 자발적 프로톤 펌프 억제제의 부재하에 재구성 안된다. 이와 같이, BiFC 분석에서의 형광 신호 만 높은 특이성 프로톤 펌프 억제제의 직접적인 시각화를 가능하게 프로톤 펌프 억제제의 존재하에 일어난다. 판독으로 형광을 사용하는 추가 혜택은 다른 사람의 사이에서 높은 처리량과 높은 콘텐츠 심사 분석, 높은 감도, 세포 내 해상도 및 호환성이다. 이러한 장점에 대해, 다른 상위 형광 단백질에 기초 BiFC 프로브의 수는 개발되었다. 통상적 인 광 현미경 검사에 기초하여 모든 다른 검출 기술에서와 같이, 그러나 BiFC의 공간 분해능은 빛의 회절에 의해 ~ 250 나노 미터로 제한된다. 이 지질 뗏목 (6)을하여 이전 언급과 예시 된 바와 같이, 나노 스케일에서 프로톤 펌프 억제제의 조절을 연구하기 위해 그것에게 도전한다ND 라스 나노 클러스터 (7)는 이러한 시그널링 많은 세포 과정을 이해하는데 중요한 길이 스케일이다. BiFC는 프로톤 펌프 억제제 (10) 이미징을위한 공간 해상도에서이 한계를 극복하기 위해 광 활성화 현지화 현미경 (PALM) 8,9과 결합되었다. 손바닥 확률 활성화 및 단일 형광 분자의 subdiffractive 현지화를 통해 형광 이미징의 회절 한계를 우회 최근 수퍼 해상력 현미경 기술이다. 각 사이클에서 활성화, 형광 분자는 몇천 광자 몇백을 방출하고 검출기상의 단일 분자 영상을 발생시킨다. 화상 회절 한정 동안 (~ 250 nm의 폭)은, 그 중심은 일반적으로 검출 된 광자의 수에 따라 10 ~ 50 nm 인 주문에, 훨씬 더 높은 정밀도로 측정 할 수있다. 활성화하고 샘플의 각 형광 분자를 로컬 화하여, 고해상도 화상이 재구성 될 수있다. Performe살아있는 세포에 D, 하나의 셀 (11)에서 단백질 확산 궤적 수천의 단일 분자 추적 (SMT를 구분) 종려 추가 허가 취득. 중요한 것은, 손바닥 확률 활성화를 달성하기 위해 이러한 광활성 형광 단백질 (PA-FPS)와 같은 특수 형광 프로브를 사용합니다. BiFC 및 PALM 이용 형광 단백질 양 때문에,이 아미노산 159과 160 사이의 두 단편으로, PALM PAmCherry1 위해, 일반적으로 사용되는 PA-FP를 분할하여 혼합 하였다. 스플릿 PAmCherry1에 기초 BiFC 시스템은 두 조각의 자발적인 재구성에서 낮은 배경 신호를 나타낸다. 상호 작용하는 단백질의 유전자 쌍 태그 때, 두 조각 (RN = 159은 잔기 RC = + 잔기 1백60부터 2백36까지 메트)에도 37 ℃ 낮은 온도에서 배양없이 완전한 PAmCherry1 단백질을 형성하도록 효율적으로 재구성 어느 이러한 부모 mCherry (13)와 같은 다른 BiFC 쌍 (12)의 경우에는 해당되지 않습니다. Furthermo다시 재구성 PAmCherry1 단백질은 정확한 단일 분자 현지화 및 고해상도 PALM 영상에 중요한 다른 사람 사이의 높은 명암비, 매체 광자 수율, 빠른 photoactivati​​on, 같은 부모 PAmCherry1의 광 물리 특성을 유지했다. 이 프로토콜에서, 스플릿 PAmCherry1 (도 1A)를 사용하여 U2OS 세포에서 라스 - 미친 상호 작용을 이미징 BiFC-PALM의 사용을 설명한다. 첫 번째 단계는 PAmCherry1 단편 (즉, RN과 RC) 및 관심 단백질 사이의 융합 단백질을 표현하기위한 구조를 설계하는 것이다. 이론적으로, 후보 단백질 (A 및 B)의 각 쌍에 대해, 융합 단백질 여덟 쌍 테스트 될있다 : RN-A / RC-B; RN-A / B-RC; RC-A / RN-B; RC-A / B-RN; A-RN / RC-B; A-RN / B-RC; -RC / RN-B; 및-RC는 / B-RN. 이 프로세스는 종종 계정에 후보 단백질의 구조적 또는 생화학 적 특성을 고려함으로써 단순화 될 수있다. 라스의 경우, 상기 단백질은번역 후 C- 말단 CAAX 상자에서 수정 (C = Cys이고; = 지방족, X = 모든), 그 후 AAX 모티브 전원이 절단된다. 따라서, RN 또는 RC은 라스의 N 말단에 융합 될 수있다; 이 4 개의 (도 1b)에 대한 융합 단백질의 쌍의 수를 감소시킨다. Raf를 들어, 도메인은 라스 - 결합 (RBD를 잔기 51에서 1백31까지)가 사용되며, 양단에 태그 될 수있다. 이러한 네 융합 구성이 생성되었다 : RN-KRAS / RC-Raf를 RBD; RN-KRAS / Raf를 RBD-RC; RC-KRAS / RN-Raf를 RBD; 와 RC-KRAS / Raf를 RBD-RN. 또한, 단편 및 관심 단백질 사이의 링커는 고려 될 필요가있을 것이다. 약 10 아미노산 링커는 유연 종종 보완이 발생하기에 충분한 자유도를 제공로서 사용된다. 여러 복제 사이트 (MCS) (14)에서 생성 된 임의의 시퀀스를 포함하여 성공적으로 적용되어 많은 사람들이 있기는하지만 그 중 하나 링커, (GGGGS) X2입니다. 링커의 길이는 dependin 최적화 될 필요가있다관심의 단백질과 방향 상호 작용의 크기에 들어. PAmCherry1 단편의 MCS의 측면에있는 작은 복제 백본에 포함되어 있습니다 (자료 목록 참조). 관심있는 유전자는 제한 부위로 결찰 또는 독립적 인 방식으로 삽입 될 수있다. 클로닝 및 서열 확인 후, 발현 카세트가 재조합 효소 반응, 높은 정확도 및 높은 효율로 복제 프로세스를 사용하여 발현 벡터로 전달된다. 이어서, 생성 된 작 제물은 발현 표적 세포주를 감염위한 안정된 세포주 원하면, 렌티 바이러스로 패키지, 표적 세포주로 형질 감염 또는된다. 과도 형질은 BiFC 구성의 빠른 확인이 가능하지만, 잠재적 인 문제는 주목해야합니다. 종종 화학 물질을 사용하는 형질 감염이 높은 형광도의 결과, 세포를 강조; 반면 전반사 형광 (TIRF) microsco 사용PY는 프로톤 펌프 억제제는 세포막에 일어날 때 조명 볼륨 TIRF 이상적 제한함으로써 이러한 배경 신호를 완화 할 수있다. 또한, 일시적인 형질은 종종까지 프로톤 펌프 억제제를 검출하는 아티팩트가 발생할 수 있습니다 내인성 단백질의 사람들을 초과, 단백질 발현의 높은 수준을 초래할. 따라서, 적절한 BiFC 구성은 초기 테스트를 통해 측정 한 후 안정한 세포주를 확립하는 것이 권장된다. 안정한 세포주는 독시사이클린 유도 (15)를 통해 조정 가능한 발현의 가능성을 가지고있다. 감염 후 세포는 일반적으로 퓨로 마이신과 각 구조에 대한 네오 마이신, 하나, 항생제로 선택됩니다. 샘플 준비, 이미지 수집 및 데이터 분석을위한 후속 단계는 프로토콜에 상세히 설명한다. 이 방법, 라스-Raf를 RBD의 BiFC-PALM 이미지에서 나노 클러스터의 형성이 정기적으로 관찰된다 (그림 2A &lt;/ STRONG&gt;). 지속적으로, 라스-Raf를 RBD의 SMT-PALM 궤도는 확산 상태 (그림 2B-D)에서 이종 분포를 보여줍니다. 이러한 결과는 라스-Raf를 착체 잠재적 생물 함의 아마도 단량체 및 클러스터로서, 세포막의 여러 상태에 있는지 제안한다. 이 작업은 종래 BiFC 형광 공동 지역화 또는 형광 공명 에너지 전달 (FRET)을 얻는 것이 어려울 수 나노 미터의 공간 해상도와 단일 분자 감도를 가진 세포에서의 프로톤 펌프 억제제의 선택적 이미징 BiFC-PALM의 전력을 나타낸다. BiFC 실험을 설계하고 결과를 해석 할 때, BiFC 프로세스가 분할 PAmCherry1을 포함하여 대부분의 경우에 돌이킬 명심하는 것이 중요하다. 두 조각이 결합하여 완전한 PAmCherry1 단백질, 두 조각 사이의 결합을 형성하고, 일단 따라서 PPI는 영구된다. 이것은 BiFC과 BiFC-PAL의 사용을 제한프로톤 펌프 억제제의 역학 (즉, 결합 반응 속도가 아니라이 형성되면 단백질 복합체의 확산 역학)를 모니터링하고 시간에 M 심지어 PPI 단지의 mislocalization가 발생할 수 있습니다. BiFC-PALM 실험을 설계하는 형광 단백질에 내재되어 발색단 성숙의 지연 인 경우 추가 요인을 고려해야한다. 두 단백질이 상호 작용하고 FP 조각이 함께 모여되면, 그들은 일반적으로 초 (EYFP 3 60 초 하프 타임)의 순서에 접힘. 그러나, 이후의 발색단의 성숙과 형광 신호 분 정도의 개발. 형광 분할 금성, 빨리 접는 YFP 변형의 재구성 후 10 분 이내에 검출 할 수 있지만, 일반적으로 성숙 하프 타임은 종종 약 60 분 (16)이다. 분할 PAmCherry1 비슷한 속도를 가지고 관찰 하였다. 따라서, BiFC과 BiFC-PALM 실시간 PPI 속도론을 모니터링 현재 가난한 선택할 수 있습니다; 다른 나FRET과 같은 최근 개발 된 이량 종속 형광 단백질 17 thods 등이 목적에 더 적합 할 수있다.

<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.

표시된 BiFC-PALM 예제 CRaf의 도메인 (RBD) (그림 1A)를 결합 라스와 상호 작용 KRAS G12D 돌연변이입니다. 논의 된 바와 같이 그것의 라스 막 지역화 때문에 생물학적 활성을 방해 할 것이기 때문에, RN 또는 RC 라스 단편의 C- 말단에 태그되지 않았다. 이 네 가지 (그림 1B)에 여덟에서 가능한 조합을 감소시켰다. 이러한 네 개의 조합들 각각은 렌티 바이러스를 사용하여 감염 U2OS 세?...

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.

이분자 형광 보완과 광 활성화 현지화 현미경 (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 조회수.  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. 

비디오: 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.

미생물에 접속 조직 및 역학 시각화, 총 내부 반사의 형광 현미경을 사용하여

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

연구

생체공학

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).

가변 각도 총 내부 반사 형광 현미경 (VA-TIRFM)시 세포 접착의 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.

형광 현미경과 영상 셀 마이그레이션을위한 접착제 및 가용성식이 그라디언트를 만들기

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.

멀티 스펙트럼 이미징 유동 세포 계측법과 세포의 현지화 및 탄소 나노 튜브의 상대 정량

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.

단일 분자 형광 현미경에 의한 수용체 역학의 고해상도 시공간 분석

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.

수정 된 두 개의 광자 현미경에서 3D 궤도 추적 : 세포 내 소포의 추적에 응용

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.

위한 도구로 리포좀 캡슐화 된 근적외선 형광의 형광 담금질<em&gt; 생체</em&gt; 광학 이미징

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.

평면에 단일 분자 형광 현미경은 이중층 지원

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.

Murine 심장 연구에 대 한 빛-시트 형광 현미경 검사 법

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.

실시 한 형광 현미경으로 여러 영상 모드

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