Bu çalışma, Umut Scholar Ödülü Savunma Era Bölümü (No W81XWH-05-0396) ve Edward B. Brown III Biyomedikal Bilimler Ödülü Pew Scholar tarafından finanse edildi.

1. Optik hizalayın. MP-sıkı bağlamak deney için önemli ekipman şunlardır: mod-kilitli bir lazer kaynağı, Pockel Hücre (ışın modülasyon), nabız jeneratör, renk değişikliği, objektif lens, floresan emisyon filtresi, kapılı photomultiplier tüp, ve bir veri kayıt sistemi (foton sayacı ve çok kanallı ölçekleyici). 2. Güvenli monitör yetkilerini belirler. <ol><li> Örnek içinde floresan üretmek için düşük, ama makul, güç lazer zayıflatır. </li><li> Örnek içinde odaklanın. </li><li> Beklenen floresan kurtarma daha çok uzun bir zaman ölçeği üzerinde entegre bir foton sayacı ayarlayın. Mikroskop yazılım odak hacmi (bu bir nokta tarama ile elde edilir) numune içinde sabit tutulan makul bir sayıda foton sayımı verileri kaydeder. </li><li> Gücünü artırmak ve foton sayımı verileri başka bir dizi çekmek. Foton sayılarında artış gücünü artırmak açısından önemli ölçüde azaltmak için görünene kadar tekrarlayın. </li><li> Arsa log (güç) bir fonksiyonu olarak log (foton sayısı). Monitör sırasında beyazlatma iki yamacında bir sapma gösterir. Monitörün güç olarak bu cut off bir güç seçin, ancak makul bir sinyal gürültü oranı sağlar. </li></ol> 3. Pulse jeneratör ve çok kanallı ölçekleyici giriş parametreleri belirleyin. <ol><li> Belirleyin geri-of-the-zarf edebiyat ve / veya Stokes-Einstein denklemi, difüzyon denklemi dayalı difüzyon katsayısı ve iyileşme süresi tahminleri. </li><li> Darbe jeneratörü ve ölçekleyici gerekli parametre değerleri ayarlayın. <ol class="lalpha"><li> Darbe jeneratörü, önceden çamaşır suyu ve ağartıcı kez ayarlayın. Başparmak kuralları iyi bir ön-beyazlatıcı beklenen yarısında iyileşme süresi daha 1-2 kat daha büyük olması gerektiğini ve çamaşır suyu beklenen yarısında iyileşme süresi onda biri olmalıdır. </li><li> Ölçekleyici, yaklaşık bir yarım çamaşır suyu süresi bin genişliği ve kayıt başına kutularının sayısını ayarlamak seçtiğiniz bin genişliği ve kayıt başına kutuları ürün beklenen tam iyileşme artı ön yaklaşık eşit veya daha büyük olduğu gibi -Çamaşır suyu ve ağartıcı kez. </li><li> Darbe jeneratörü dönün ve sadece bin genişliği kez kayıt başına kutuların sayısı ürünü ters daha küçük bir değere eşit pre-bleach/bleach/monitor dizisi frekansını ayarlamak. * </li><li> Son olarak, kayıtların sayısını ayarlamak / seçtiğiniz monitör güçte sinyal yoğunluğuna göre ölçekleyici tarama. * Darbe jeneratör tam bir pre-bleach/bleach/monitor dizisi (1/frequency) için zaman ölçekleyici veri toplama süresi (bin genişlik x kutuları / kayıt) daha fazla olduğu çok önemlidir. Bu kriterleri yerine değilse, birden fazla ağartıcı tetikler ölçekleyici tek bir kayıt içinde görünebilir. </li></ol></li><li> Monitörün güç, önceden belirlenmiş kabul edilebilir bir seviyeye ayarlayın. Monitör beyazlatma test sırasında belirlenen beyazlatma kesim üzerinde 200 mW veya çamaşır suyu gücünü ayarlayın. Bu güçler PC kristal boyunca farklı gerilim olarak ayarlanır, her ikisi de. </li><li> Mikroskop Seal, ışıkları kapatmak PMT açmak, mikroskop yazılımı üzerinde bir nokta tarama başlamak, sonra darbe jeneratörü ve ölçekleyici başlar. </li><li> 1) ön-bleach floresan, 2) floresan hemen post-çamaşır suyu, ve 3) veri setinin sonunda floresan: eğrisinin çizilmesi ve üç önemli nokta işaretleme çıkan kurtarma eğrisi analiz edin. Floresans değerleri öncesi ve hemen sonrası yarı-iyileşme süresi daha iyi tahmin etmek için çamaşır suyu. Kullanın. </li><li> Yarı-iyileşme süresi, bu tahmin, önceden çamaşır suyu, çamaşır suyu için yeni değerlerini belirlemek için daha önce belirtilen başparmak kuralları ve bin genişliği süreleri kullanın. Ayrıca, tam iyileşme elde etmek için gerekli süreyi daha iyi tahmin etmek için veri kümesinin sonunda öncesi ağartıcı floresan ve floresan kullanın. Genel bir kural olarak, veri, verilerin ikinci yarısı için rapor edilmesi tam iyileşme sağlar bir süre için alınmalıdır. </li><li> Eğrisi güçlü bir çamaşır suyu ve pürüzsüz bir iyileşme sergiliyor kadar darbe jeneratörü ve ölçekleyici parametrelerini ayarlayın, yeni bir eğri parametreleri almak ve ince ayar devam. Mümkünse, çamaşır suyu süresi göz önünde bulundurun ve başparmak kural altına düşürülmelidir. Çok sığ, ya da çok derin, çamaşır suyu elde edilir, çamaşır suyu gücü de ayarlanabilir. </li></ol> 4. Test uyarım doygunluk. <ol><li> Önceden belirlenmiş uygun monitör ve çamaşır suyu güçler, MP-sıkı bağlamak eğrilerini kullanarak, bir dizi alır. Uygun matematiksel formu ve doğrusal olmayan en küçük kareler uydurma algoritması (bkz. aşağıdaki &quot;Veri Analizi&quot;) kullanarak, ön ağartıcı floresan normalize her kurtarma, analiz edin. Çamaşır suyu derinliği parametre monte değeri kaydedin.</li><li> MP-sıkı bağlamak eğrileri birbirini izleyen seriler alma ve analiz çamaşır suyu güç değerlerini artırarak devam edin. </li><li> Arsa log (güç) bir fonksiyonu olarak log (çamaşır suyu derinliği parametresi). Herhangi bir sapma, bir yamaç iki uyarma doygunluk gösterir. Güçlü bir çamaşır suyu verimi çamaşır suyu güç seçin, ancak doygunluk neden olmaz. </li></ol> 5. MP-sıkı bağlamak eğrileri çekmeye devam edin. <ol><li> Yukarıdaki gibi, bütün parametreler düzgün koyacaktır, eğriler çekmeye devam edin. </li></ol> 6. Veri Analizi. <ol><li> Floresan veri öncesi, çamaşır suyu ve ağartıcı veri, bu veri seti ve ayarlamak kaldırın t = 0 hemen sonrası-ağartıcı floresan değeri ile karşılık gelir. </li><li> -Bleach öncesi ortalama floresan açısından ortaya çıkan floresan kurtarma Normale. </li><li> Uygun bir matematiksel model ve MATLAB lsqcurvefit fonksiyonu olarak doğrusal olmayan, en küçük kareler uydurma algoritması kullanılarak normalize eğrisi sığdır. Burada sunulan model, difüzyon ve konvektif akışı hem de etkilemiş floresan kurtarma hesapları: <img src="/files/ftp_upload/1636/1636eq.jpg" alt="Denklem" /> F o ön ağartıcı ortalama floresan nerede çamaşır suyu derinliği parametresi, β, τ D karakteristik uzadıya iyileşme süresi, R eksenel radyal (w r) genişlikleri karesine oranı (w z) iki foton odak hacmi, τ vx = w r / v x, τ Vy = w r / v y τ vz = w, z / v z ve v 2 = v x 2 + v y 2 + v, z 2- konvektif akış hızı. Görüntü düzlemi ile sınırlı akışı için, τ vz → ∞ ve 1 / τ vx + 1 / τ Vy 1 / τ vr ile değiştirilebilir. Konvektif akışının olmaması, pay hem de üsteller 1 gidip ifade sadece iki uydurma parametreleri, β ve τ D büyük ölçüde azaltılmış oluyor . Difüzyon katsayısı D = w r 2 / 8τ D olarak kolayca hesaplanır. </li></ol> 7. Temsilcisi Sonuçlar. <img src="/files/ftp_upload/1636/1636fig1.jpg" alt="Şekil 1" /> Şekil 1 Temsilcisi çamaşır suyu ve FITC-BSA için kurtarma eğrisi. Iyi bir iyileşme eğrisi verilerin ikinci yarısında tam bir iyileşme floresan ile, güçlü bir çamaşır suyu ve pürüzsüz bir iyileşme sergiliyor. <img src="/files/ftp_upload/1636/1636fig2.jpg" alt="Şekil 2" /> Şekil 2 FITC-BSA Normalize kurtarma eğrisi (kırmızı) ve en küçük kareler ilgili uyum (siyah). Bu uyum, literatür ile tutarlı, difüzyon katsayısı, 52.9 um2 / s verir.

<ol>
	<li>Denk, W., Strickler, J. H., Webb, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-photon+laser+scanning+fluorescence+microscopy.">Two-photon laser scanning fluorescence microscopy.</a> Biophys J. 60, 73-76 (1990).</li><li>Brown, E. B., Wu, E. S., Zipfel, W., Webb, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+molecular+diffusion+in+solution+by+multiphoton+fluorescence+photobleaching+recovery.">Measurement of molecular diffusion in solution by multiphoton fluorescence photobleaching recovery.</a> Biophys J. 77, 2837-2849 (1999).</li><li>Sullivan, K. D., Sipprell, W. H. B. r. o. w. n., Jr, E. B., Brown, E. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+model+of+fluorescence+recovery+expands+the+application+of+multiphoton+fluorescence+recover+after+photobleaching+in+vivo.">Improved model of fluorescence recovery expands the application of multiphoton fluorescence recover after photobleaching in vivo.</a> Biophys J. 96, 5082-5094 (2009).</li></ol>

Photobleaching sonra çok foton floresan kurtarma gücü 3D çözünürlük ile kalın örnekleri prob yeteneği yatıyor. 1990 yılında gelişme bu yana, MP-sıkı bağlamak hücre gövdeleri, ex vivo kalın bir doku dilimleri ve in vivo doku ve interstisyumda difüzyon katsayısı (ya da analog ulaşım parametreleri) belirlemek için kullanılır olmuştur. Bu makalede, biz, deneysel parametreler ayar verileri alma ve kurtarma eğrileri analiz, MP-sıkı bağlamak gibi deney, ışın yolu ...

<table><tbody><tr><td>Ti:sapphire laser</td><td>Newport Corp.</td><td>Mai Tai</td><td></td></tr><tr><td>Pockels Cell</td><td>Conoptics</td><td>350-80</td><td></td></tr><tr><td>Laser Scanning Microscope</td><td>Olympus Corporation</td><td>Fluoview</td><td></td></tr><tr><td>Short pass dichroic mirror</td><td>Chroma Technology Corp.</td><td>670 DCSX-2P</td><td></td></tr><tr><td>Photomultiplier tube</td><td>Hamamatsu Corp.</td><td>HC125-02</td><td></td></tr><tr><td>Photon counter</td><td>Stanford Research Systems</td><td>SR 400</td><td></td></tr><tr><td>Multi-channel scaler/averager</td><td>Stanford Research Systems</td><td>SR 430</td><td></td></tr><tr><td>Pulse Generator</td><td>Stanford Research Systems</td><td>DG 535</td><td></td></tr><tr><td>FITC-BSA</td><td>Invitrogen</td><td>--</td><td></td></tr></tbody></table>

measuring diffusion coefficients via two-photon fluorescence recovery after photobleaching

Photobleaching sonra çok floresan kurtarma makromoleküllerin difüzyon katsayısı (ya da analog ulaşım parametreleri) ölçmek için kullanılan bir mikroskopi tekniği ve hem de uygulanabilir<em&gt; In vitro</em&gt; Ve<em&gt; In vivo</em&gt; Biyolojik sistemleri. Photobleaching sonra çok floresan kurtarma sonra ışın azaltıcı ve izleme photobleached moleküllerin yerine ilgi diffüz bölge dışından hala floresan moleküller olarak floresan yoğun bir lazer flaş kullanmadan floresan örnek bir bölge içinde ilgi photobleaching tarafından yapılır . Biz Pockel Hücre (lazer modülatör) ve örnek lazer tarama kutusu ve objektif lens ile optik yol boyunca lazer ışını hizalayarak gösteri başlayacak. Basitlik için, floresan boya, sulu bir örnek kullanabilirsiniz. Daha sonra uygun deneysel dahil olmak üzere bizim örnek parametreleri, monitör ve ağartma güçler, çamaşır suyu süresi, bin genişlikleri (foton sayma), ve floresan iyileşme süresi belirleyecek. Sonra, kurtarma eğrileri, büyük ölçüde gelişmiş akış için (National Instruments, Austin, Teksas) LabVIEW ile otomatik hale getirilebilir bir süreç ayırdığınız için prosedür anlatacağız. Son olarak, difüzyon katsayısı MATLAB (Mathworks, Natick, MA) gibi yazılımlar kullanarak kolayca programlanabilir en küçük kareler uydurma algoritması kullanılarak uygun bir matematiksel model kurtarma veri sıkıştırılmak suretiyle belirlenir.

Watch this Scientific Journal Video about Measuring Diffusion Coefficients via Two-photon Fluorescence Recovery After Photobleaching at JoVE.com

Measuring Diffusion Coefficients via Two-photon Fluorescence Recovery After Photobleaching

Bu yazıda, photobleaching sonra çok foton floresan kurtarma kullanarak difüzyon katsayıları ölçmek için prosedür anlatacağız. Biz örnek optik yol boyunca lazer hizalayarak ve uygun deneysel parametrelerin belirlenmesi ile başlayacak, daha sonra devam üreten ve nihayet uydurma floresan kurtarma eğrileri.

İki foton Floresan Kurtarma üzerinden Photobleaching sonra Difüzyon Katsayıları Ölçüm

Multi-fluorescence recovery after photobleaching is a microscopy technique used to measure the diffusion coefficient (or analogous transport parameters) ...

measuring-diffusion-coefficients-via-two-photon-fluorescence-recovery

Universidad de Cartagena UDEC

Research

JoVE Journal

Biology

11.1K Görüntüleme.  University of Rochester. Bu yazıda, photobleaching sonra çok foton floresan kurtarma kullanarak difüzyon katsayıları ölçmek için prosedür anlatacağız. Biz örnek optik yol boyunca lazer hizalayarak ve uygun deneysel parametrelerin belirlenmesi ile başlayacak, daha sonra devam üreten ve nihayet uydurma floresan kurtarma eğrileri.

Video: Measuring Diffusion Coefficients via Two-photon Fluorescence Recovery After Photobleaching

High Precision FRET at Single-molecule Level for Biomolecule Structure Determination

A protocol on how to perform high-precision interdye distance measurements using F&#246;rster resonance energy transfer (FRET) at the single-molecule level in multiparameter fluorescence detection (MFD) mode is presented here. MFD maximizes the usage of all &#34;dimensions&#34; of fluorescence to reduce photophysical and experimental artifacts and allows for the measurement of interdye distance with an accuracy up to ~1 &#197; in rigid biomolecules. This method was used to identify three conformational states of the ligand-binding domain of the N-methyl-D-aspartate (NMDA) receptor to explain the activation of the receptor upon ligand binding. When comparing the known crystallographic structures with experimental measurements, they agreed within less than 3 &#197; for more dynamic biomolecules. Gathering a set of distance restraints that covers the entire dimensionality of the biomolecules would make it possible to provide a structural model of dynamic biomolecules.

A protocol for high-precision FRET experiments at the single molecule level is presented here. Additionally, this methodology can be used to identify three conformational states in the ligand-binding domain of the N-methyl-D-aspartate (NMDA) receptor. Determining precise distances is the first step towards building structural models based on FRET experiments.

Biyomolekül Yapısının Belirlenmesi İçin Tek Molekül Seviyesinde Yüksek Hassasiyetteki FRET

A protocol on how to perform high-precision interdye distance measurements using F&#246;rster resonance energy transfer (FRET) at the single-molecule ...

Biyokimya

From Fast Fluorescence Imaging to Molecular Diffusion Law on Live Cell Membranes in a Commercial Microscope

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the regulation of many cellular functions. However, due to the fast dynamics and the tiny structures involved, a very high spatio-temporal resolution is required to catch the real behavior of molecules. Here we present the experimental protocol for studying the dynamics of fluorescently-labeled plasma-membrane proteins and lipids in live cells with high spatiotemporal resolution. Notably, this approach doesn&#8217;t need to track each molecule, but it calculates population behavior using all molecules in a given region of the membrane. The starting point is a fast imaging of a given region on the membrane. Afterwards, a complete spatio-temporal autocorrelation function is calculated correlating acquired images at increasing time delays, for example each 2, 3, n repetitions. It is possible to demonstrate that the width of the peak of the spatial autocorrelation function increases at increasing time delay as a function of particle movement due to diffusion. Therefore, fitting of the series of autocorrelation functions enables to extract the actual protein mean square displacement from imaging (iMSD), here presented in the form of apparent diffusivity vs average displacement. This yields a quantitative view of the average dynamics of single molecules with nanometer accuracy. By using a GFP-tagged variant of the Transferrin Receptor (TfR) and an ATTO488 labeled 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (PPE) it is possible to observe the spatiotemporal regulation of protein and lipid diffusion on &#181;m-sized membrane regions in the micro-to-milli-second time range.

Spatial distribution and temporal dynamics of plasma membrane proteins and lipids is a hot topic in biology. Here this issue is addressed by a spatio-temporal image fluctuation analysis that provides conceptually the same physical quantities of single particle tracking, but it uses small molecular labels and standard microscopy setups.

Ticari Mikroskop Canlı Hücre Zarları Moleküler Difüzyon Kanunu Hızlı Floresans Görüntüleme Gönderen

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the ...

Biyomühendislik

Fluorescence Recovery after Merging a Droplet to Measure the Two-dimensional Diffusion of a Phospholipid Monolayer

We introduce a new method to measure the lateral diffusivity of a surfactant monolayer at the fluid-fluid interface, called fluorescence recovery after merging (FRAM). FRAM adopts the same principles as the fluorescence recovery after photobleaching (FRAP) technique, especially for measuring fluorescence recovery after bleaching a specific area, but FRAM uses a drop coalescence instead of photobleaching dye molecules to induce a chemical potential gradient of dye molecules. Our technique has several advantages over FRAP: it only requires a fluorescence microscope rather than a confocal microscope equipped with high power lasers; it is essentially free from the selection of fluorescence dyes; and it has far more freedom to define the measured diffusion area. Furthermore, FRAM potentially provides a route for studying the mixing or inter-diffusion of two different surfactants, when the monolayers at a surface of droplet and at a flat air/water interface are prepared with different species, independently.

We present a new technique to measure the lateral diffusion of a surface active species at the fluid-fluid interface by merging a droplet monolayer onto a flat monolayer.

Bir Damlacık birleştirme sonra Floresan Kurtarma Fosfolipid Monolayer İki boyutlu Difüzyon Tedbir

We introduce a new method to measure the lateral diffusivity of a surfactant monolayer at the fluid-fluid interface, called fluorescence recovery after ...

PIP-on-a-chip: A Label-free Study of Protein-phosphoinositide Interactions

Numerous cellular proteins interact with membrane surfaces to affect essential cellular processes. These interactions can be directed towards a specific lipid component within a membrane, as in the case of phosphoinositides (PIPs), to ensure specific subcellular localization and/or activation. PIPs and cellular PIP-binding domains have been studied extensively to better understand their role in cellular physiology. We applied a pH modulation assay on supported lipid bilayers (SLBs) as a tool to study protein-PIP interactions. In these studies, pH sensitive ortho-Sulforhodamine B conjugated phosphatidylethanolamine is used to detect protein-PIP interactions. Upon binding of a protein to a PIP-containing membrane surface, the interfacial potential is modulated (i.e. change in local pH), shifting the protonation state of the probe. A case study of the successful usage of the pH modulation assay is presented by using phospholipase C delta1 Pleckstrin Homology (PLC-&#948;1 PH) domain and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) interaction as an example. The apparent dissociation constant (Kd,app) for this interaction was 0.39 &#177; 0.05 &#181;M, similar to Kd,app values obtained by others. As previously observed, the PLC-&#948;1 PH domain is PI(4,5)P2 specific, shows weaker binding towards phosphatidylinositol 4-phosphate, and no binding to pure phosphatidylcholine SLBs. The PIP-on-a-chip assay is advantageous over traditional PIP-binding assays, including but not limited to low sample volume and no ligand/receptor labeling requirements, the ability to test high- and low-affinity membrane interactions with both small and large molecules, and improved signal to noise ratio. Accordingly, the usage of the PIP-on-a-chip approach will facilitate the elucidation of mechanisms of a wide range of membrane interactions. Furthermore, this method could potentially be used in identifying therapeutics that modulate protein&#39;s capacity to interact with membranes.

Here we present a supported lipid bilayer in the context of a microfluidic platform to study protein-phosphoinositide interactions using a label-free method based on pH modulation.

PIP-on-a-chip: Protein-fosfoinositid Etkileşimlerinin Etiketsiz Bir Çalışması

Numerous cellular proteins interact with membrane surfaces to affect essential cellular processes. These interactions can be directed towards a specific ...

Molecular Diffusion in Plasma Membranes of Primary Lymphocytes Measured by Fluorescence Correlation Spectroscopy

Fluorescence correlation spectroscopy (FCS) is a powerful technique for studying the diffusion of molecules within biological membranes with high spatial and temporal resolution. FCS can quantify the molecular concentration and diffusion coefficient of fluorescently labeled molecules in the cell membrane. This technique has the ability to explore the molecular diffusion characteristics of molecules in the plasma membrane of immune cells in steady state (i.e., without processes affecting the result during the actual measurement time). FCS is suitable for studying the diffusion of proteins that are expressed at levels typical for most endogenous proteins. Here, a straightforward and robust method to determine the diffusion rate of cell membrane proteins on primary lymphocytes is demonstrated. An effective way to perform measurements on antibody-stained live cells and commonly occurring observations after acquisition are described. The recent advancements in the development of photo-stable fluorescent dyes can be utilized by conjugating the antibodies of interest to appropriate dyes that do not bleach extensively during the measurements. Additionally, this allows for the detection of slowly diffusing entities, which is a common feature of proteins expressed in cell membranes. The analysis procedure to extract molecular concentration and diffusion parameters from the generated autocorrelation curves is highlighted. In summary, a basic protocol for FCS measurements is provided; it can be followed by immunologists with an understanding of confocal microscopy but with no other previous experience of techniques for measuring dynamic parameters, such as molecular diffusion rates.

A method to measure protein diffusion in membranes of primary immune cells using fluorescence correlation spectroscopy (FCS) is described. In this paper, the use of antibodies for fluorescent labeling is illustrated.

Flüoresan Korelasyon Spektroskopisi Ölçülen İlköğretim Lenfositler Plazma Membranlarda moleküler difüzyon

Fluorescence correlation spectroscopy (FCS) is a powerful technique for studying the diffusion of molecules within biological membranes with high spatial ...

İmmünoloji ve Enfeksiyon

Measurement of Force-Sensitive Protein Dynamics in Living Cells Using a Combination of Fluorescent Techniques

Cells sense and respond to physical cues in their environment by converting mechanical stimuli into biochemically-detectable signals in a process called mechanotransduction. A crucial step in mechanotransduction is the transmission of forces between the external and internal environments. To transmit forces, there must be a sustained, unbroken physical linkage created by a series of protein-protein interactions. For a given protein-protein interaction, mechanical load can either have no effect on the interaction, lead to faster disassociation of the interaction, or even stabilize the interaction. Understanding how molecular load dictates protein turnover in living cells can provide valuable information about the mechanical state of a protein, in turn elucidating its role in mechanotransduction. Existing techniques for measuring force-sensitive protein dynamics either lack direct measurements of protein load or rely on the measurements performed outside of the cellular context. Here, we describe a protocol for the F&#246;rster resonance energy transfer-fluorescence recovery after photobleaching (FRET-FRAP) technique, which enables the measurement of force-sensitive protein dynamics within living cells. This technique is potentially applicable to any FRET-based tension sensor, facilitating the study of force-sensitive protein dynamics in variety of subcellular structures and in different cell types.

Here, we present a protocol for the simultaneous use of F&#246;rster resonance energy transfer-based tension sensors to measure protein load and fluorescence recovery after photobleaching to measure protein dynamics enabling the measurement of force-sensitive protein dynamics within living cells.

Kuvvet duyarlı Protein Dynamics floresan teknikleri bir arada kullanarak canlı hücrelerdeki ölçümü

Cells sense and respond to physical cues in their environment by converting mechanical stimuli into biochemically-detectable signals in a process called ...

Determination of Lipid Raft Partitioning of Fluorescently-tagged Probes in Living Cells by Fluorescence Correlation Spectroscopy (FCS)

In the past fifteen years the notion that cell membranes are not homogenous and rely on microdomains to exert their functions has become widely accepted. Lipid rafts are membrane microdomains enriched in cholesterol and sphingolipids. They play a role in cellular physiological processes such as signalling, and trafficking1,2 but are also thought to be key players in several diseases including viral or bacterial infections and neurodegenerative diseases3.
Yet their existence is still a matter of controversy4,5. Indeed, lipid raft size has been estimated to be around 20 nm6, far under the resolution limit of conventional microscopy (around 200 nm), thus precluding their direct imaging. Up to now, the main techniques used to assess the partition of proteins of interest inside lipid rafts were Detergent Resistant Membranes (DRMs) isolation and co-patching with antibodies. Though widely used because of their rather easy implementation, these techniques were prone to artefacts and thus criticized7,8. Technical improvements were therefore necessary to overcome these artefacts and to be able to probe lipid rafts partition in living cells.
Here we present a method for the sensitive analysis of lipid rafts partition of fluorescently-tagged proteins or lipids in the plasma membrane of living cells. This method, termed Fluorescence Correlation Spectroscopy (FCS), relies on the disparity in diffusion times of fluorescent probes located inside or outside of lipid rafts. In fact, as evidenced in both artificial membranes and cell cultures, probes would diffuse much faster outside than inside dense lipid rafts9,10. To determine diffusion times, minute fluorescence fluctuations are measured as a function of time in a focal volume (approximately 1 femtoliter), located at the plasma membrane of cells with a confocal microscope (Fig. 1). The auto-correlation curves can then be drawn from these fluctuations and fitted with appropriate mathematical diffusion models11.
FCS can be used to determine the lipid raft partitioning of various probes, as long as they are fluorescently tagged. Fluorescent tagging can be achieved by expression of fluorescent fusion proteins or by binding of fluorescent ligands. Moreover, FCS can be used not only in artificial membranes and cell lines but also in primary cultures, as described recently12. It can also be used to follow the dynamics of lipid raft partitioning after drug addition or membrane lipid composition change12.

Determination of Lipid Raft Partitioning of Fluorescently-tagged Probes in Living Cells by Fluorescence Correlation Spectroscopy FCS

A technique to probe the lipid raft partitioning of fluorescent proteins at the plasma membrane of living cells is described. It takes advantage of the disparity in diffusion times of proteins located inside or outside of lipid rafts. Acquisition can be performed dynamically in control conditions or after drug addition.

Lipid Raft belirlenmesi Flüoresan Korelasyon Spektroskopisi (FCS) tarafından Yaşayan hücreler içinde floresan etiketli Soruşturmasının Bölümleme

In the past fifteen years the notion that cell membranes are not homogenous and rely on microdomains to exert their functions has become widely accepted. ...

Biyoloji

Automated Two-dimensional Spatiotemporal Analysis of Mobile Single-molecule FRET Probes

Single-molecule F&#246;rster resonance energy transfer (smFRET) is a versatile technique reporting on distances in the sub-nanometer to nanometer range. It has been used in a wide range of biophysical and molecular biological experiments, including the measurement of molecular forces, characterization of conformational dynamics of biomolecules, observation of intracellular colocalization of proteins, and determination of receptor-ligand interaction times. In a widefield microscopy configuration, experiments are typically performed using surface-immobilized probes. Here, a method combining single-molecule tracking with alternating excitation (ALEX) smFRET experiments is presented, permitting the acquisition of smFRET time traces of surface-bound, yet mobile probes in plasma membranes or glass-supported lipid bilayers. For the analysis of recorded data, an automated, open-source software collection was developed supporting (i) the localization of fluorescent signals, (ii) single-particle tracking, (iii) determination of FRET-related quantities including correction factors, (iv) stringent verification of smFRET traces, and (v) intuitive presentation of the results. The generated data can conveniently be used as input for further exploration via specialized software, e.g., for the assessment of the diffusional behavior of probes or the investigation of FRET transitions.

This article presents a method for spatiotemporal analysis of mobile, single-molecule F&#246;rster resonance energy transfer (smFRET)-based probes using widefield fluorescence microscopy. The newly developed software toolkit allows the determination of smFRET time traces of moving probes, including the correct FRET efficiency and the molecular positions, as functions of time.

Mobil Tek Moleküllü FRET Problarının Otomatik İki Boyutlu Mekansal Analizi

Single-molecule F&#246;rster resonance energy transfer (smFRET) is a versatile technique reporting on distances in the sub-nanometer to nanometer range. ...

Easy Measurement of Diffusion Coefficients of EGFP-tagged Plasma Membrane Proteins Using k-Space Image Correlation Spectroscopy

Lateral diffusion and compartmentalization of plasma membrane proteins are tightly regulated in cells and thus, studying these processes will reveal new insights to plasma membrane protein function and regulation. Recently, k-Space Image Correlation Spectroscopy (kICS)1&#160;was developed to enable routine measurements of diffusion coefficients directly from images of fluorescently tagged plasma membrane proteins, that avoided systematic biases introduced by probe photophysics. Although the theoretical basis for the analysis is complex, the method can be implemented by nonexperts using a freely available code to measure diffusion coefficients of proteins. kICS calculates a time correlation function from a fluorescence microscopy image stack after Fourier transformation of each image to reciprocal (k-) space. Subsequently, circular averaging, natural logarithm transform and linear fits to the correlation function yields the diffusion coefficient. This paper provides a step-by-step guide to the image analysis and measurement of diffusion coefficients via kICS.
First, a high frame rate image sequence of a fluorescently labeled plasma membrane protein is acquired using a fluorescence microscope. Then, a region of interest (ROI) avoiding intracellular organelles, moving vesicles or protruding membrane regions is selected. The ROI stack is imported into a freely available code and several defined parameters (see Method section) are set for kICS analysis. The program then generates a &#34;slope of slopes&#34; plot from the k-space time correlation functions, and the diffusion coefficient is calculated from the slope of the plot. Below is a step-by-step kICS procedure to measure the diffusion coefficient of a membrane protein using the renal water channel aquaporin-3 tagged with EGFP as a canonical example.

This paper provides a step by step guide to the fluctuation analysis technique k-Space Image Correlation Spectroscopy (kICS) for measuring diffusion coefficients of fluorescently labeled plasma membrane proteins in live mammalian cells.

K-Uzay Görüntü Korelasyon Spektroskopisi kullanarak EGFP-etiketli Plazma Membran Proteinleri Difüzyon Katsayılarının kolay Ölçümü

Lateral diffusion and compartmentalization of plasma membrane proteins are tightly regulated in cells and thus, studying these processes will reveal new ...

Internalization and Observation of Fluorescent Biomolecules in Living Microorganisms via Electroporation

The ability to study biomolecules in vivo is crucial for understanding their function in a biological context. One powerful approach involves fusing molecules of interest to fluorescent proteins such as GFP to study their expression, localization and function. However, GFP and its derivatives are significantly larger and less photostable than organic fluorophores generally used for in vitro experiments, and this can limit the scope of investigation. 
We recently introduced a straightforward, versatile and high-throughput method based on electroporation, allowing the internalization of biomolecules labeled with organic fluorophores into living microorganisms. Here we describe how to use electroporation to internalize labeled DNA fragments or proteins into Escherichia coli and Saccharomyces cerevisi&#230;, how to quantify the number of internalized molecules using fluorescence microscopy, and how to quantify the viability of electroporated cells. Data can be acquired at the single-cell or single-molecule level using fluorescence or FRET. The possibility of internalizing non-labeled molecules that trigger a physiological observable response in vivo is also presented. Finally, strategies of optimization of the protocol for specific biological systems are discussed.

Studies of biomolecules in vivo are crucial for understanding molecular function in a biological context. Here we describe a novel method allowing the internalization of fluorescent biomolecules, such as DNA or proteins, into living microorganisms. Analysis of in vivo data recorded by fluorescence microscopy is also presented and discussed.

Elektroporasyon yoluyla Yaşam Mikroorganizmalar içinde içselleştirilmesi ve Floresan biyomoleküllerin Gözlem

The ability to study biomolecules in vivo is crucial for understanding their function in a biological context. One powerful approach involves fusing ...