העבודה נתמכה על ידי NIH מענקים AI57159 (עד SCH) ו AI72346 (עד AMvO). SCH הוא הווארד יוז חוקר רפואי במכון.

<ol>
	<li>Elender, G., Kuhner, M., Sackmann, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalisation+of+Si/SiO2+and+glass+surfaces+with+ultrathin+dextran+films+and+deposition+of+lipid+bilayers.">Functionalisation of Si/SiO2 and glass surfaces with ultrathin dextran films and deposition of lipid bilayers.</a> Biosens Bioelectron. 11, 565-577 (1996).</li><li>Floyd, D. L., Ragains, J. R., Skehel, J. J., Harrison, S. C., van Oijen, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-particle+kinetics+of+influenza+virus+membrane+fusion.">Single-particle kinetics of influenza virus membrane fusion.</a> Proc Natl Acad Sci U S A. 105, 15382-15387 (2008).</li></ol>

הכנת נוזל רציפה bilayers השומנים נתמך יכול להיות מאתגר. כמויות זעירות של חומר מזהם פגמים או משטח תמנע הפצת bilayers. בתצהיר ניקוי זהיר של שכבה אחידה של dextran חיוניים. הדמיה ממושכת של חלקיקי הנגיף יכול להלבין את תוויות ניאון או לגרום להם להי...

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		<div>
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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Corning cover glass squares, 25 mm</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>CLS286525</td>
<td>&nbsp;</td>
<tr>
<td>Fused silica slides</td>
<td>&nbsp;</td>
<td>Technical Glass</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Staining rack</td>
<td>&nbsp;</td>
<td>Thomas Scientific</td>
<td>8542E40</td>
<td>&nbsp;</td>
<tr>
<td>(3- glycidoxypropyl)trimethoxysilane</td>
<td>&nbsp;</td>
<td>Gelest</td>
<td>SIG5840.1</td>
<td>&nbsp;</td>
<tr>
<td>Dextran T-500</td>
<td>&nbsp;</td>
<td>Pharmacosmos</td>
<td>5510 0500 4006</td>
<td>&nbsp;</td>
<tr>
<td>1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)</td>
<td>&nbsp;</td>
<td>Avanti</td>
<td>850375</td>
<td>&nbsp;</td>
<tr>
<td>1-palmitoyl-2oleoyl-sn-glycero-3-phosphocholine (POPC)</td>
<td>&nbsp;</td>
<td>Avanti</td>
<td>850457</td>
<td>&nbsp;</td>
<tr>
<td>Cholesterol</td>
<td>&nbsp;</td>
<td>Avanti</td>
<td>700000</td>
<td>&nbsp;</td>
<tr>
<td>N-((6-(biotinoyl)amino)hexanoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, triethylammonium salt (biotin-X DHPE)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>B1616</td>
<td>&nbsp;</td>
<tr>
<td>Streptavidin, fluorescein conjugate</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>S-869</td>
<td>&nbsp;</td>
<tr>
<td>Disialoganglioside GD1a from bovine brain</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>G2392</td>
<td>&nbsp;</td>
<tr>
<td>Mini Extruder</td>
<td>&nbsp;</td>
<td>Avanti</td>
<td>610000</td>
<td>&nbsp;</td>
<tr>
<td>0.1 micron polycarbonate membrane filters</td>
<td>&nbsp;</td>
<td>Whatman</td>
<td>800309</td>
<td>&nbsp;</td>
<tr>
<td>10 mm drain discs (membrane supports)</td>
<td>&nbsp;</td>
<td>Whatman</td>
<td>230300</td>
<td>&nbsp;</td>
<tr>
<td>Sulforhodamine b sodium salt</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>S1402</td>
<td>&nbsp;</td>
<tr>
<td>Octadecyl rhodamine 110 (Rh110C18)</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>See Floyd et al. 2008 for synthesis protocol</td>
</tr>
<tr>
<td>PD-10 desalting columns</td>
<td>&nbsp;</td>
<td>GE Healthcare</td>
<td>17-0851-01</td>
<td>&nbsp;</td>
<tr>
<td>Nikon fluorescence microscope</td>
<td>&nbsp;</td>
<td>Nikon</td>
<td>TE2000-U</td>
<td>&nbsp;</td>
<tr>
<td>Plan Apo TIRF 60x 1.45 NA objective</td>
<td>&nbsp;</td>
<td>Nikon</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Innova 70C Spectrum Ar/Kr laser</td>
<td>&nbsp;</td>
<td>Coherent</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Syringe Pump</td>
<td>&nbsp;</td>
<td>Harvard Apparatus</td>
<td>702213</td>
<td>&nbsp;</td>		</tbody>
		</table>
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method for measurement of viral fusion kinetics at the single particle level

היתוך ממברנה היא מהווה נדבך חיוני במהלך כניסה של וירוסים עטופים לתוך התאים. מבחני היתוך קונבנציונלי בדרך כלל לדווח על מספר רב של אירועים היתוך, ולכן קשה לנתח באופן כמותי את רצף הפעולות המולקולריים המעורבים. פיתחנו במבחנה, שני צבעים assay הקרינה לפקח קינטיקה של פיוזינג חלקיקי נגיף יחיד עם bilayer היעד על תמיכה נוזל בעיקרו. חלקיקים שפעת נגיפית מודגרת עם fluorophore lipophilic ירוק להכתים את הממברנה fluorophore הידרופילי אדום להכתים את פנים ויראלי. אנו פיקדון bilayer ganglioside המכילים שומנים על פני השטח dextran-functionilized הזכוכית של התא זרימה, דגירה חלקיקים נגיפיים על bilayer את התמונה מישוריים את הקרינה של 100 x 100 מיקרומטר אזור 2, המכיל כמה מאות של חלקיקים, על CCD המצלמה. על ידי הדמיה הן פלואורסצנטי אדום וירוק, אנחנו יכולים בו זמנית לפקח על התנהגותם של לצבוע את הממברנה (ירוק) לבין תוכן מימית (אדום) של חלקיקים. לאחר הפחתת ה-pH מתחת לערך pH המיזוג, חלקיקים יהיה הפתיל עם הממברנה. Hemifusion, מיזוג של עלון החיצוני של קרום ויראלי עם עלון החיצוני של קרום היעד, יהיה גלוי כשינוי פתאומי פלואורסצנטי ירוק של חלקיק. עם היתוך הבאים של שני כרוזים דיסטלי הנותרים נקבוביות תוקם ואת fluorophore אדום פולטות חלקיק נגיפי ישוחררו תחת קרום היעד. אירוע זה יהיה להצמיח ירידה של הקרינה האדום של חלקיקים בודדים. לבסוף, פלואורסצנציה משולב מ fluorophore pH רגיש המוטבע קרום היעד מדווחת על הזמן המדויק של ירידה ה-pH. מתוך שלושת זמן פלואורסצנציה-עקבות, את כל האירועים החשובים (ירידה pH, שומנים ערבוב על תוכן hemifusion, ערבוב על היווצרות נקבוביות) כעת ניתן לחלץ בצורה ישירה עבור כל חלקיק בנפרד. על ידי איסוף פעמים שחלף על מעברים שונים עבור חלקיקים בודדים רבים היסטוגרמות, אנו יכולים לקבוע את תקופות חיים של ביניים המקביל. אפילו ביניים נסתרים אין הנצפה פלורסנט ישיר ניתן דמיינו ישירות היסטוגרמות אלו.

Watch this Scientific Journal Video about Method for Measurement of Viral Fusion Kinetics at the Single Particle Level at JoVE.com

Method for Measurement of Viral Fusion Kinetics at the Single Particle Level

אנו מציגים<em&gt; במבחנה,</em&gt; שני צבעים assay הקרינה לדמיין את היתוך של חלקיקי נגיף יחיד עם bilayer היעד נוזל. על ידי תיוג חלקיקים נגיפיים עם fluorophores כי דיפרנציאלי כתם הממברנה ויראלי הפנים שלה, אנו יכולים לפקח על קינטיקה של hemifusion היווצרות נקבוביות.

שיטת מדידה של קינטיקס Fusion ויראלי ברמה חלקיק יחיד

Membrane fusion is an essential step during entry of enveloped viruses into cells. Conventional fusion assays typically report on a large number of fusion ...

method-for-measurement-viral-fusion-kinetics-at-single-particle

Research

JoVE Journal

Biology

12.8K Views.  Harvard Medical School. אנו מציגים במבחנה, שני צבעים assay הקרינה לדמיין את היתוך של חלקיקי נגיף יחיד עם bilayer היעד נוזל. על ידי תיוג חלקיקים נגיפיים עם fluorophores כי דיפרנציאלי כתם הממברנה ויראלי הפנים שלה, אנו יכולים לפקח על קינטיקה של hemifusion היווצרות נקבוביות.

Video: Method for Measurement of Viral Fusion Kinetics at the Single Particle Level

Single Particle Electron Microscopy Reconstruction of the Exosome Complex Using the Random Conical Tilt Method

Single particle electron microscopy (EM) reconstruction has recently become a popular tool to get the three-dimensional (3D) structure of large macromolecular complexes. Compared to X-ray crystallography, it has some unique advantages. First, single particle EM reconstruction does not need to crystallize the protein sample, which is the bottleneck in X-ray crystallography, especially for large macromolecular complexes. Secondly, it does not need large amounts of protein samples. Compared with milligrams of proteins necessary for crystallization, single particle EM reconstruction only needs several micro-liters of protein solution at nano-molar concentrations, using the negative staining EM method. However, despite a few macromolecular assemblies with high symmetry, single particle EM is limited at relatively low resolution (lower than 1 nm resolution) for many specimens especially those without symmetry. This technique is also limited by the size of the molecules under study, i.e. 100 kDa for negatively stained specimens and 300 kDa for frozen-hydrated specimens in general.
For a new sample of unknown structure, we generally use a heavy metal solution to embed the molecules by negative staining. The specimen is then examined in a transmission electron microscope to take two-dimensional (2D) micrographs of the molecules. Ideally, the protein molecules have a homogeneous 3D structure but exhibit different orientations in the micrographs. These micrographs are digitized and processed in computers as "single particles". Using two-dimensional alignment and classification techniques, homogenous molecules in the same views are clustered into classes. Their averages enhance the signal of the molecule's 2D shapes. After we assign the particles with the proper relative orientation (Euler angles), we will be able to reconstruct the 2D particle images into a 3D virtual volume.
In single particle 3D reconstruction, an essential step is to correctly assign the proper orientation of each single particle. There are several methods to assign the view for each particle, including the angular reconstitution1 and random conical tilt (RCT) method2. In this protocol, we describe our practice in getting the 3D reconstruction of yeast exosome complex using negative staining EM and RCT. It should be noted that our protocol of electron microscopy and image processing follows the basic principle of RCT but is not the only way to perform the method. We first describe how to embed the protein sample into a layer of Uranyl-Formate with a thickness comparable to the protein size, using a holey carbon grid covered with a layer of continuous thin carbon film. Then the specimen is inserted into a transmission electron microscope to collect untilted (0-degree) and tilted (55-degree) pairs of micrographs that will be used later for processing and obtaining an initial 3D model of the yeast exosome. To this end, we perform RCT and then refine the initial 3D model by using the projection matching refinement method3.

This article describes a standard method to get a three-dimensional (3D) reconstruction of biological macromolecules using negative staining electron microscopy (EM). In this protocol, we explain how to get the 3D structure of the Saccharomyces cerevisiae exosome complex at medium resolution using the random conical tilt reconstruction method (RCT).

חלקיק יחיד מיקרוסקופית אלקטרונים שיקום במתחם Exosome שימוש בשיטה אקראיים הטיה חרוטי

Single particle electron microscopy (EM) reconstruction has recently become a popular tool to get the three-dimensional (3D) structure of large ...

Measuring the Kinetics of mRNA Transcription in Single Living Cells

The transcriptional activity of RNA polymerase II (Pol II) is a dynamic process and therefore measuring the kinetics of the transcriptional process in vivo is of importance. Pol II kinetics have been measured using biochemical or molecular methods.1-3 In recent years, with the development of new visualization methods, it has become possible to follow transcription as it occurs in real time in single living cells.4 Herein we describe how to perform analysis of Pol II elongation kinetics on a specific gene in living cells.5, 6 Using a cell line in which a specific gene locus (DNA), its mRNA product, and the final protein product can be fluorescently labeled and visualized in vivo, it is possible to detect the actual transcription of mRNAs on the gene of interest.7, 8 The mRNA is fluorescently tagged using the MS2 system for tagging mRNAs in vivo, where the 3'UTR of the mRNA transcripts contain 24 MS2 stem-loop repeats, which provide highly specific binding sites for the YFP-MS2 coat protein that labels the mRNA as it is transcribed.9 To monitor the kinetics of transcription we use the Fluorescence Recovery After Photobleaching (FRAP) method. By photobleaching the YFP-MS2-tagged nascent transcripts at the site of transcription and then following the recovery of this signal over time, we obtain the synthesis rate of the newly made mRNAs.5 In other words, YFP-MS2 fluorescence recovery reflects the generation of new MS2 stem-loops in the nascent transcripts and their binding by fluorescent free YFP-MS2 molecules entering from the surrounding nucleoplasm. The FRAP recovery curves are then analyzed using mathematical mechanistic models formalized by a series of differential equations, in order to retrieve the kinetic time parameters of transcription.

RNA polymerase II transcriptional kinetics are measured on specific genes in living cells. mRNAs transcribed from the gene of interest are fluorescently tagged and using Fluorescence Recovery After Photobleaching (FRAP) the in vivo kinetics of transcriptional elongation are obtained.

מדידת קינטיקה של שעתוק mRNA בתאים חיים יחיד

The transcriptional activity of RNA polymerase II (Pol II) is a dynamic process and therefore measuring the kinetics of the transcriptional process in ...

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations

Equal distribution of chromosomes between the two daughter cells during cell division is a prerequisite for guaranteeing genetic stability 1. Inaccuracies during chromosome separation are a hallmark of malignancy and associated with progressive disease 2-4. The spindle assembly checkpoint (SAC) is a mitotic surveillance mechanism that holds back cells at metaphase until every single chromosome has established a stable bipolar attachment to the mitotic spindle1. The SAC exerts its function by interference with the activating APC/C subunit Cdc20 to block proteolysis of securin and cyclin B and thus chromosome separation and mitotic exit. Improper attachment of chromosomes prevents silencing of SAC signaling and causes continued inhibition of APC/CCdc20 until the problem is solved to avoid chromosome missegregation, aneuploidy and malignant growths1.
Most studies that addressed the influence of improper chromosomal attachment on APC/C-dependent proteolysis took advantage of spindle disruption using depolymerizing or microtubule-stabilizing drugs to interfere with chromosomal attachment to microtubules. Since interference with microtubule kinetics can affect the transport and localization of critical regulators, these procedures bear a risk of inducing artificial effects 5.
To study how the SAC interferes with APC/C-dependent proteolysis of cyclin B during mitosis in unperturbed cell populations, we established a histone H2-GFP-based system which allowed the simultaneous monitoring of metaphase alignment of mitotic chromosomes and proteolysis of cyclin B 6.
To depict proteolytic profiles, we generated a chimeric cyclin B reporter molecule with a C-terminal SNAP moiety 6 (Figure 1). In a self-labeling reaction, the SNAP-moiety is able to form covalent bonds with alkylguanine-carriers (SNAP substrate) 7,8 (Figure 1). SNAP substrate molecules are readily available and carry a broad spectrum of different fluorochromes. Chimeric cyclin B-SNAP molecules become labeled upon addition of the membrane-permeable SNAP substrate to the growth medium 7 (Figure 1). Following the labeling reaction, the cyclin B-SNAP fluorescence intensity drops in a pulse-chase reaction-like manner and fluorescence intensities reflect levels of cyclin B degradation 6 (Figure 1). Our system facilitates the monitoring of mitotic APC/C-dependent proteolysis in large numbers of cells (or several cell populations) in parallel. Thereby, the system may be a valuable tool to identify agents/small molecules that are able to interfere with proteolytic activity at the metaphase to anaphase transition. Moreover, as synthesis of cyclin B during mitosis has recently been suggested as an important mechanism in fostering a mitotic block in mice and humans by keeping cyclin B expression levels stable 9,10, this system enabled us to analyze cyclin B proteolysis as one element of a balanced equilibrium 6.

Metaphase to anaphase transition is triggered through anaphase-promoting complex (APC/C)-dependent ubiquitination and subsequent destruction of cyclin B. Here, we established a system which, following pulse-chase labeling, allows monitoring cyclin B proteolysis in entire cell populations and facilitates the detection of interference by the mitotic checkpoint.

לומד Proteolysis של cyclin B ברמת התא הבודד באוכלוסיות תאים שלמות

Equal distribution of chromosomes between the two daughter cells during cell division is a prerequisite for guaranteeing genetic stability 1. Inaccuracies ...

Analysis of Global RNA Synthesis at the Single Cell Level following Hypoxia

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a particular transcriptional program in order to mount an appropriate and coordinated cellular response. The cell possesses several oxygen sensor enzymes that require molecular oxygen as cofactor for their activity. These range from prolyl-hydroxylases to histone demethylases. The majority of studies analyzing cellular responses to hypoxia are based on cellular populations and average studies, and as such single cell analysis of hypoxic cells are seldom performed. Here we describe a method of analysis of global RNA synthesis at the single cell level in hypoxia by using Click-iT RNA imaging kits in an oxygen controlled workstation, followed by microscopy analysis and quantification.&nbsp; Using cancer cells exposed to hypoxia for different lengths of time, RNA is labeled and measured in each cell. This analysis allows the visualization of temporal and cell-to-cell changes in global RNA synthesis following hypoxic stress.

We describe a technique for analysis of global RNA synthesis in hypoxia using imaging. Click-chemistry labeling of RNA has not previously been performed under hypoxia and allows visualization of global RNA changes at the single cell level. This approach complements the existing averaged RNA techniques, allowing direct visualization of cell-to-cell changes in global RNA synthesis.

ניתוח של גלובל RNA סינתזה ברמת התא בודד הבאות היפוקסיה

Hypoxia or lowering of the oxygen availability is involved in many physiological and pathological processes. At the molecular level, cells initiate a ...

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are inactive due to 5' truncations, ~80-100 of these elements remain retrotransposition competent and propagate to different locations throughout the genome via RNA intermediates. While older L1s are believed to target AT rich regions of the genome, the chromosomal targets of newer, more active L1s remain poorly defined. Here we describe fluorescence in situ hybridization (FISH) methodology that can be used to track patterns of L1 insertion and rates of ectopic L1 incorporation at the single nucleus level. In these experiments, fluorescein isothiocyanate/cyanine-3 (FITC/CY3) labeled neomycin probes were employed to track L1 retrotransposition in vitro in HepG2 cells stably expressing ectopic L1. This methodology prevents errors in the estimation of rates of retrotransposition posed by toxicity and account for the occurrence of multiple insertions into a single nucleus.

Here we employ FISH methodology to track LINE-1 retrotransposition at the single nuclei level in chromosome spreads of HepG2 cell lines stably expressing synthetic LINE-1.

ניתוח של ורטרו-טרנספוזיציה LINE-1 ברמת יחיד Nucleus

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are ...

Open-source Single-particle Analysis for Super-resolution Microscopy with VirusMapper

Super-resolution fluorescence microscopy is currently revolutionizing cell biology research. Its capacity to break the resolution limit of around 300 nm allows for the routine imaging of nanoscale biological complexes and processes. This increase in resolution also means that methods popular in electron microscopy, such as single-particle analysis, can readily be applied to super-resolution fluorescence microscopy. By combining this analytical approach with super-resolution optical imaging, it becomes possible to take advantage of the molecule-specific labeling capacity of fluorescence microscopy to generate structural maps of molecular elements within a metastable structure. To this end, we have developed a novel algorithm &#8212; VirusMapper &#8212; packaged as an easy-to-use, high-performance, and high-throughput ImageJ plugin. This article presents an in-depth guide to this software, showcasing its ability to uncover novel structural features in biological molecular complexes. Here, we present how to assemble compatible data and provide a step-by-step protocol on how to use this algorithm to apply single-particle analysis to super-resolution images.

This manuscript uses the Fiji-based open-source software package VirusMapper to apply single-particle analysis to super-resolution microscopy images in order to generate precise models of nanoscale structure.

ניתוח קוד פתוח Single-חלקיק למיקרוסקופיה סופר-רזולוציה עם VirusMapper

Super-resolution fluorescence microscopy is currently revolutionizing cell biology research. Its capacity to break the resolution limit of around 300 nm ...

Advanced Confocal Microscopy Techniques to Study Protein-protein Interactions and Kinetics at DNA Lesions

Local microirradiation with lasers represents a useful tool for studies of DNA-repair-related processes in live cells. Here, we describe a methodological approach to analyzing protein kinetics at DNA lesions over time or protein-protein interactions on locally microirradiated chromatin. We also show how to recognize individual phases of the cell cycle using the Fucci cellular system to study cell-cycle-dependent protein kinetics at DNA lesions. A methodological description of the use of two UV lasers (355 nm and 405 nm) to induce different types of DNA damage is also presented. Only the cells microirradiated by the 405-nm diode laser proceeded through mitosis normally and were devoid of cyclobutane pyrimidine dimers (CPDs). We also show how microirradiated cells can be fixed at a given time point to perform immunodetection of the endogenous proteins of interest. For the DNA repair studies, we additionally describe the use of biophysical methods including FRAP (Fluorescence Recovery After Photobleaching) and FLIM (Fluorescence Lifetime Imaging Microscopy) in cells with spontaneously occurring DNA damage foci. We also show an application of FLIM-FRET (Fluorescence Resonance Energy Transfer) in experimental studies of protein-protein interactions.

Laser microirradiation is a useful tool for studies of DNA repair in living cells. A methodological approach for the use of UVA lasers to induce various DNA lesions is shown. We have optimized a method for local microirradiation that maintains the normal cell cycle; thus, irradiated cells proceed through mitosis.

מיקרוסקופיה קונפוקלית טכניקות ללמוד אינטראקציות חלבון-חלבון וקינטיקה ב DNA נגעים מתקדמות

Local microirradiation with lasers represents a useful tool for studies of DNA-repair-related processes in live cells. Here, we describe a methodological ...

Simple and Effective Administration and Visualization of Microparticles in the Circulatory System of Small Fishes Using Kidney Injection

The systemic administration of micro-size particles into a living organism can be applied for vasculature visualization, drug and vaccine delivery, implantation of transgenic cells and tiny optical sensors. However, intravenous microinjections into small animals, which are mostly used in biological and veterinary laboratories, are very difficult and require trained personnel. Herein, we demonstrate a robust and efficient method for the introduction of microparticles into the circulatory system of adult zebrafish (Danio rerio) by injection into the fish kidney. To visualize the introduced microparticles in the vasculature, we propose a simple intravital imaging technique in fish gills. In vivo monitoring of the zebrafish blood pH was accomplished using an injected microencapsulated fluorescent probe, SNARF-1, to demonstrate one of the possible applications of the described technique. This article provides a detailed description of the encapsulation of pH-sensitive dye and demonstrates the principles of the quick injection and visualization of the obtained microcapsules for in vivo recording of the fluorescent signal. The proposed method of injection is characterized by a low mortality rate (0-20%) and high efficiency (70-90% success), and it is easy to institute using commonly available equipment. All described procedures can be performed on other small fish species, such as guppies and medaka.

This article demonstrates the principles of a quick, minimally invasive injection of fluorescent microparticles into the circulatory system of small fishes and the in vivo visualization of the microparticles in fish blood.

ניהול פשוטה ויעילה והדמיה של Microparticles במערכת הדם של דגים קטנים באמצעות הזרקת כליות

The systemic administration of micro-size particles into a living organism can be applied for vasculature visualization, drug and vaccine delivery, ...

Visualizing the Interaction Between the Qdot-labeled Protein and Site-specifically Modified &#955; DNA at the Single Molecule Level

The fluorescence microscopy&#160;has made great contributions in dissecting the mechanisms of complex biological processes at the single molecule level. In single molecule assays for studying DNA-protein interactions, there are two important factors for consideration: the DNA substrate with enough length for easy observation and labeling a protein with a suitable fluorescent probe. 48.5 kb &#955; DNA is a good candidate for the DNA substrate. Quantum dots (Qdots), as a class of fluorescent probes, allow long-time observation (minutes to hours) and high-quality image acquisition. In this paper, we present a protocol to study DNA-protein interactions at the single-molecule level, which includes preparing a site-specifically modified &#955; DNA and labeling a target protein with streptavidin-coated Qdots. For a proof of concept, we choose ORC (origin recognition complex) in budding yeast as a protein of interest and visualize its interaction with an ARS (autonomously replicating sequence) using TIRFM. Compared with other fluorescent probes, Qdots have obvious advantages in single molecule studies due to its high stability against photobleaching, but it should be noted that this property limits its application in quantitative assays.

Visualizing the Interaction Between the Qdot-labeled Protein and Site-specifically Modified &amp;#955; DNA at the Single Molecule Level

Here, we present a protocol to study DNA-protein interactions by total internal reflection fluorescence microscopy (TIRFM) using a site-specifically modified &#955; DNA substrate and a Quantum-dot labeled protein.

להמחיש את האינטראקציה בין התווית על-ידי Qdot חלבונים ו- DNA λ ששונה Site-specifically ברמת מולקולה בודדת

The fluorescence microscopy&#160;has made great contributions in dissecting the mechanisms of complex biological processes at the single molecule level. ...

Isolation and Fluorescence Imaging for Single-particle Reconstruction of Chlamydomonas Centrioles

Centrioles are large macromolecular assemblies important for the proper execution of fundamental cell biological processes such as cell division, cell motility, or cell signaling. The green algae Chlamydomonas reinhardtii has proven to be an insightful model in the study of centriole architecture, function, and protein composition. Despite great advances toward understanding centriolar architecture, one of the current challenges is to determine the precise localization of centriolar components within structural regions of the centriole in order to better understand their role in centriole biogenesis. A major limitation lies in the resolution of fluorescence microscopy, which complicates the interpretation of protein localization in this organelle with dimensions close to the diffraction limit. To tackle this question, we are providing a method to purify and image a large number of C. reinhardtii centrioles with different orientations using super-resolution microscopy. This technique allows further processing of data through fluorescent single-particle averaging (Fluo-SPA) owing to the large number of centrioles acquired. Fluo-SPA generates averages of stained C. reinhardtii centrioles in different orientations, thus facilitating the localization of distinct proteins in centriolar sub-regions. Importantly, this method can be applied to image centrioles from other species or other large macromolecular assemblies.

Isolation and Fluorescence Imaging for Single-particle Reconstruction of Chlamydomonas Centrioles

We have developed a strategy to purify and image a large number of centrioles in different orientations amenable for super-resolution microscopy and single-particle averaging.

בידוד והדמיה פלורסצנטיות עבור שחזור יחיד-חלקיקים של Chlamydomonas Centrioles

Centrioles are large macromolecular assemblies important for the proper execution of fundamental cell biological processes such as cell division, cell ...