We acknowledge the research support by the Intramural Research Program of NIBIB, NIH.

Sample Cell Assembly and Torque
<ol>
<li>We begin sample cell construction by putting together 2 window assemblies. 
Place a window gasket into the window holder. Position the window liner (or it&#x2019;s sometimes called a window cushion) inside the window holder so that the opening of the liner is opposite the keyway of the holder. At a slight angle, place the window in the holder aligning the scribe mark on the window with the key way of the window holder. Press down gently at the very edges on both sides of the window.</li>
<li>To ensure proper sealing and accurate torque of the sample cell, we lightly coat the housing gasket and the screw ring with Spinkote lubricant. Spread a very small amount of Spinkote between your thumb and forefinger. Coat the screw ring threads with a thin, invisible film of Spinkote. Likewise, coat the housing gasket. Wipe off any visible lubricant.</li>
<li>Begin sample cell assembly by sliding one window assembly, with the window facing up towards you, into the cell housing by aligning the keyway with the housing key. Align the centerpiece keyway with the housing key and let it gently fall on top of the window assembly inside the cell.</li>
<li>Never use any sort of tool to push the centerpiece into the cell housing. This could cause permanent damage to the CP resulting in leak during experiments. Turn the second window assembly so that the window is facing towards the centerpiece, away from you, align keyway with housing key and slide it down on top of the centerpiece. Place a housing gasket on top, then, a screw ring so the word "Out" is visible. Using your fingers and an alignment tool, hand tighten the screw ring. 
If the CP doesn&#x2019;t slide easily into the housing barrel, first align it, then, place the second window assembly on top of it. By applying gentle downward pressure on the window assembly, slide both into the cell housing at the same time. This way, we avoid pressing directly on the CP. 
Now is a good time to look inside the cell for dust, lint and fingerprints. You will also notice Newton&#x2019;s Rings that indicate there is still air between the CP and the windows. These will disappear after applying torque.</li>
<li>With the screw ring up and the word "out" visible, place the sample cell all the way down inside the cell torque collet of the torque stand. Hold cell in place by applying constant pressure on the torque stand handle. In one continuous motion, tighten the screw ring to between 120-140 in-lbs. If using an adjustable micrometer torque wrench, set it to between 120-140 in/lbs and tighten the screw ring until wrench "clicks" indicating the set torque has been reached. Release the torque stand handle and carefully remove the sample cell without touching the windows.
</li>
</ol>
Loading and Sealing the Sample Cell
<ol start="6">
 <li> For sedimentation velocity experiments, we routinely load a volume of 400ul into each sector of the 12mm centerpiece using a 200ul pipette. Position the sample cell with the loading holes on top and the word "out" on the screw ring visible. Slide the pipette tip half way down into the LEFT centerpiece sector through the loading holes and slowly dispense 200ul of reference solution. Repeat once to total 400ul. Using the same pipette tip and the same technique, carefully and slowly fill the RIGHT centerpiece sector with 400ul of sample solution. Volumes of 150-180 ul are used for sedimentation equilibrium experiments but the same care and technique should be followed. 
It is imperative to match the volumes of reference and sample solutions as closely as possible. Fitting the pipette tip firmly onto the pipette, slowly loading and dispensing solutions, avoiding loading bubbles and using the same pipette tip for both solutions all aid in keeping the volumes as equal as possible.</li>
 <li>Seal the cell by placing 2 new red housing plug gaskets snugly into each loading hole making sure they are positioned between the center piece and the aluminum housing. Cover each with a housing plug. Hand tighten with a small flat head screwdriver.
</li>
</ol>
Sample Cell Alignment in Rotor
<ol start="8">
<li>Before loading the rotor, make sure the counterbalance is no more than .5g LIGHTER than the sample cell in the opposite position in case that sample cell leaks. Start out with the balance at zero. First weigh the sample cell that will be in position opposite the CB. Tare the balance to subtract the sample cell weight, then, weigh the CB. Add or subtract weight from the attachment hole of the counterbalance. Make sure weights do not protrude from the top. Reweigh to ensure that the counterbalance final weight is within .5g lighter than the opposite sample cell.</li>
<li>Using a 4-place rotor, place the counterbalance into position 4 so that the white arrow is visible and pointing in the direction of the centrifugal force. Make sure it is all the way down inside the rotor. Gently fasten the set screw, found on top of the counterbalance just across from the white arrow, until the counterbalance is firmly in place, but still able to be aligned. Position the balanced sample cell with the housing plugs facing the center of the rotor and the word "out" on the screw ring visible.</li>
<li>Looking from underneath the rotor, align the inside scribe mark (the mark closest to the center of the rotor) with the scribe mark on the counterbalance using an alignment tool. Tighten the set screw to lock aligned counterbalance in place. In the same way, align the sample cell scribe mark with the inside scribe mark at position 2 on the rotor.</li>
</ol>
For more information see <a href="https://sedfitsedphat.nibib.nih.gov/default.aspx">https://sedfitsedphat.nibib.nih.gov/default.aspx</a>

<ol>
	<li>Brown, P. H., Balbo, A., Schuck, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterizing+protein-protein+interactions+by+sedimentation+velocity+analytical+ultracentrifugation.">Characterizing protein-protein interactions by sedimentation velocity analytical ultracentrifugation.</a> Curr Protoc Immunol. Chapter 18, Unit 18.15-Unit 18.15 (2008).</li><li>Balbo, A., Brown, P. H., Braswell, E. H., Schuck, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+protein-protein+interactions+by+equilibrium+sedimentation.">Measuring protein-protein interactions by equilibrium sedimentation.</a> Curr Protoc Immunol. Chapter 18, Unit 18.8-Unit 18.8 (2007).</li><li>. Home - Workshops [Internet] Available from: <a target="_blank" href="https://sedfitsedphat.nibib.nih.gov/workshop/default.aspx">https://sedfitsedphat.nibib.nih.gov/workshop/default.aspx</a></li></ol>

The proper cell assembly, sample insertion, and cell alignment in the rotor is critical for high quality AUC experiments. This is true, in particular, for experiments that require a very detailed analysis of the acquired data on the macromolecular sedimentation profiles, for example, when studying protein interactions and determining trace aggregate amounts. Often the quality of the experimental setup is limiting for the accuracy and precision of the results from the AUC study. For details on the practical design and further execution of AUC experiments, see References 1 &#x2013; 3. Workshops covering the practical setup, theory, and data analysis of AUC experiments are being held twice a year at our laboratory at the National Institutes of Health [4].

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>4-place Ti analytical rotor</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>361964</td>
<td>&nbsp;</td>
<tr>
<td>Torque stand assembly</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>361318</td>
<td>&nbsp;</td>
<tr>
<td>Cell alignment tool</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>362340</td>
<td>&nbsp;</td>
<tr>
<td>Spinkote Lubricant</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>306812</td>
<td>&nbsp;</td>
<tr>
<td>Counterbalance</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>360219</td>
<td>&nbsp;</td>
<tr>
<td>Cell Housing kit</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>334602</td>
<td>&nbsp;</td>
<tr>
<td>Window gasket</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>327021</td>
<td>&nbsp;</td>
<tr>
<td>Window liner</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>362329</td>
<td>&nbsp;</td>
<tr>
<td>Window, sapphire</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>307177</td>
<td>&nbsp;</td>
<tr>
<td>Window, quartz</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>301730</td>
<td>&nbsp;</td>
<tr>
<td>Window holder</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>305037</td>
<td>&nbsp;</td>
<tr>
<td>12mm double sector Epon centerpiece</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>306493</td>
<td>&nbsp;</td>
<tr>
<td>Cell plug gaskets</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>327022</td>
<td>&nbsp;</td>
<tr>
<td>Cell housing plug	</td>
<td>&nbsp;</td>
<td>Beckman Coulter</td>
<td>362327</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

assembly, loading, and alignment of an analytical ultracentrifuge sample cell

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed centrifugation. When properly planned and executed, an AUC sedimentation velocity or sedimentation equilibrium experiment can reveal a great deal about a protein in regards to size and shape, sample purity, sedimentation coefficient, oligomerization states and protein-protein interactions.
This technique, however, requires a rigorous level of technical attention. Sample cells hold a sectored center piece sandwiched between two window assemblies. They are sealed with a torque pressure of around 120-140 in/lbs. Reference buffer and sample are loaded into the centerpiece sectors and then after sealing, the cells are precisely aligned into a titanium rotor so that the optical detection systems scan both sample and reference buffer in the same radial path midline through each centerpiece sector while rotating at speeds of up to 60, 000 rpm and under very high vacuum
Not only is proper sample cell assembly critical, sample cell components are very expensive and must be properly cared for to ensure they are in optimum working condition in order to avoid leaks and breakage during experiments. Handle windows carefully, for even the slightest crack or scratch can lead to breakage in the centrifuge. The contact between centerpiece and windows must be as tight as possible; i.e. no Newton s rings should be visible after torque pressure is applied. Dust, lint, scratches and oils on either the windows or the centerpiece all compromise this contact and can very easily lead to leaking of solutions from one sector to another or leaking out of the centerpiece all together. Not only are precious samples lost, leaking of solutions during an experiment will cause an imbalance of pressure in the cell that often leads to broken windows and centerpieces. In addition, plug gaskets and housing plugs must be securely in place to avoid solutions being pulled out of the centerpiece sector through the loading holes by the high vacuum in the centrifuge chamber. Window liners and gaskets must be free of breaks and cracks that could cause movement resulting in broken windows.
This video will demonstrate our procedures of sample cell assembly, torque, loading and rotor alignment to help minimize component damage, solution leaking and breakage during the perfect AUC experiment.

Watch this Scientific Journal Video about Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell at JoVE.com

Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell

The analytical ultracentrifuge (AUC) sample cell holds sample and reference buffer and during experiments and is exposed to high vacuum and rotor speeds up to 60,000 rpm. This video will demonstrate the rigorous attention to detail necessary for assembly, loading and alignment of this very important component of an AUC experiment.

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed ...

assembly-loading-alignment-an-analytical-ultracentrifuge-sample

Research

JoVE Journal

Biology

22.5K Views.  Dynamics of Macromolecular Assembly, Laboratory of Bioengineering and Physical Science. The analytical ultracentrifuge (AUC) sample cell holds sample and reference buffer and during experiments and is exposed to high vacuum and rotor speeds up to 60,000 rpm. This video will demonstrate the rigorous attention to detail necessary for assembly, loading and alignment of this very important component of an AUC experiment.

Video: Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell

Dissection of Organizer and Animal Pole Explants from Xenopus laevis Embryos and Assembly of a Cell Adhesion Assay

This video demonstrates the technique used for preparation of organizer and animal pole explants from Xenopus laevis embryos, including the use of the eyebrow knife - a specialized dissection tool made of one's eyebrow. The protocol for assembling an adhesion assay is also given, which probes for the presence of key adhesion molecules present on the surface organizer or animal pole cells that are critical for proper development.

Ex vivo Mechanical Loading of Tendon

Injuries to the tendon (e.g., wrist tendonitis, epicondyltis) due to overuse are common in sports activities and the workplace. Most are associated with repetitive, high force hand activities. The mechanisms of cellular and structural damage due to cyclical loading are not well known. The purpose of this video is to present a new system that can simultaneously load four tendons in tissue culture. The video describes the methods of sterile tissue harvest and how the tendons are loaded onto a clamping system that is subsequently immersed into media and maintained at 37&deg;C. One clamp is fixed while the other one is moved with a linear actuator. Tendon tensile force is monitored with a load cell in series with the mobile clamp. The actuators are controlled with a LabView program. The four tendons can be repetitively loaded with different patterns of loading, repetition rate, rate of loading, and duration. Loading can continue for a few minutes to 48 hours. At the end of loading, the tendons are removed and the mid-substance extracted for biochemical analyses. This system allows for the investigation of the effects of loading patterns on gene expression and structural changes in tendon. Ultimately, mechanisms of injury due to overuse can be studies with the findings applied to treatment and prevention.

A new in vitro system for simultaneously loading four tendons in culture is described.

Injuries to the tendon (e.g., wrist tendonitis, epicondyltis) due to overuse are common in sports activities and the workplace.  Most are associated with ...

In Vitro Nuclear Assembly Using Fractionated Xenopus Egg Extracts

Nuclear membrane assembly is an essential step in the cell division cycle; this process can be replicated in the test tube by combining Xenopus sperm chromatin, cytosol, and light membrane fractions. Complete nuclei are formed, including nuclear membranes with pore complexes, and these reconstituted nuclei are capable of normal nuclear processes.

Nuclear membrane assembly is an essential step in the cell division cycle; this process can be replicated in the test tube by combining Xenopus sperm chromatin, cytosol, and light membrane fractions. Complete nuclei are formed, including nuclear membranes with pore complexes, and these reconstituted nuclei are capable of normal nuclear processes.

Nuclear membrane assembly is an essential step in the cell division cycle; this process can be replicated in the test tube by combining Xenopus sperm ...

Assembly, Tuning and Use of an Apertureless Near Field Infrared Microscope for Protein Imaging

This paper aims to instruct the reader in the assembly and operation of an infrared near-field microscope for imaging beyond the diffraction limit.  The apertureless near-field microscope is a light scattering-type instrument that provides infrared spectra at circa 20 nm resolution. A complete list of components and a step-by-step protocol for use is provided.  Common errors in assembly and instrument tuning are discussed.  A representative data set that shows the secondary structure of an amyloid fibril is presented.  

The assembly of a nearfield infrared microscope for imaging protein aggregates is described.

This paper aims to instruct the reader in the assembly and operation of an infrared near-field microscope for imaging beyond the diffraction limit.  The ...

Cargo Loading onto Kinesin Powered Molecular Shuttles

Cells have evolved sophisticated molecular machinery, such as kinesin motor proteins and microtubule filaments, to support active intracellular transport of cargo. While kinesins tail domain binds to a variety of cargoes, kinesins head domains utilize the chemical energy stored in ATP molecules to step along the microtubule lattice. The long, stiff microtubules serve as tracks for long-distance intracellular transport.
These motors and filaments can also be employed in microfabricated synthetic environments as components of molecular shuttles 1. In a frequently used design, kinesin motors are anchored to the track surface through their tails, and functionalized microtubules serve as cargo carrying elements, which are propelled by these motors. These shuttles can be loaded with cargo by utilizing the strong and selective binding between biotin and streptavidin. The key components (biotinylated tubulin, streptavidin, and biotinylated cargo) are commercially available.
Building on the classic inverted motility assay 2, the construction of molecular shuttles is detailed here. Kinesin motor proteins are adsorbed to a surface precoated with casein; microtubules are polymerized from biotinylated tubulin, adhered to the kinesin and subsequently coated with rhodamine-labeled streptavidin. The ATP concentration is maintained at subsaturating concentration to achieve a microtubule gliding velocity optimal for loading cargo 3. Finally, biotinylated fluorescein-labeled nanospheres are added as cargo. Nanospheres attach to microtubules as a result of collisions between gliding microtubules and nanospheres adhering to the surface.
The protocol can be readily modified to load a variety of cargoes such as biotinylated DNA4, quantum dots 5 or a wide variety of antigens via biotinylated antibodies 4-6.

Molecular shuttles consisting of functionalized microtubules gliding on surface-adhered kinesin motor proteins can serve as a nanoscale transport system. Here, the assembly of a typical shuttle system is described.

Cells have evolved sophisticated molecular machinery, such as kinesin motor proteins and microtubule filaments, to support active intracellular transport ...

An Analytical Tool that Quantifies Cellular Morphology Changes from Three-dimensional Fluorescence Images

The most common software analysis tools available for measuring fluorescence images are for two-dimensional (2D) data that rely on manual settings for inclusion and exclusion of data points, and computer-aided pattern recognition to support the interpretation and findings of the analysis. It has become increasingly important to be able to measure fluorescence images constructed from three-dimensional (3D) datasets in order to be able to capture the complexity of cellular dynamics and understand the basis of cellular plasticity within biological systems. Sophisticated microscopy instruments have permitted the visualization of 3D fluorescence images through the acquisition of multispectral fluorescence images and powerful analytical software that reconstructs the images from confocal stacks that then provide a 3D representation of the collected 2D images. Advanced design-based stereology methods have progressed from the approximation and assumptions of the original model-based stereology1 even in complex tissue sections2. Despite these scientific advances in microscopy, a need remains for an automated analytic method that fully exploits the intrinsic 3D data to allow for the analysis and quantification of the complex changes in cell morphology, protein localization and receptor trafficking. 
Current techniques available to quantify fluorescence images include Meta-Morph (Molecular Devices, Sunnyvale, CA) and Image J (NIH) which provide manual analysis. Imaris (Andor Technology, Belfast, Northern Ireland) software provides the feature MeasurementPro, which allows the manual creation of measurement points that can be placed in a volume image or drawn on a series of 2D slices to create a 3D object. This method is useful for single-click point measurements to measure a line distance between two objects or to create a polygon that encloses a region of interest, but it is difficult to apply to complex cellular network structures. Filament Tracer (Andor) allows automatic detection of the 3D neuronal filament-like however, this module has been developed to measure defined structures such as neurons, which are comprised of dendrites, axons and spines (tree-like structure). This module has been ingeniously utilized to make morphological measurements to non-neuronal cells3, however, the output data provide information of an extended cellular network by using a software that depends on a defined cell shape rather than being an amorphous-shaped cellular model. To overcome the issue of analyzing amorphous-shaped cells and making the software more suitable to a biological application, Imaris developed Imaris Cell. This was a scientific project with the Eidgen&ouml;ssische Technische Hochschule, which has been developed to calculate the relationship between cells and organelles. While the software enables the detection of biological constraints, by forcing one nucleus per cell and using cell membranes to segment cells, it cannot be utilized to analyze fluorescence data that are not continuous because ideally it builds cell surface without void spaces. To our knowledge, at present no user-modifiable automated approach that provides morphometric information from 3D fluorescence images has been developed that achieves cellular spatial information of an undefined shape (Figure 1). 
We have developed an analytical platform using the Imaris core software module and Imaris XT interfaced to MATLAB (Mat Works, Inc.). These tools allow the 3D measurement of cells without a pre-defined shape and with inconsistent fluorescence network components. Furthermore, this method will allow researchers who have extended expertise in biological systems, but not familiarity to computer applications, to perform quantification of morphological changes in cell dynamics.

We developed a software platform that utilizes Imaris Neuroscience, ImarisXT and MATLAB to measure the changes in morphology of an undefined shape taken from three-dimensional confocal fluorescence of single cells. This novel approach can be used to quantify changes in cell shape following receptor activation and therefore represents a possible additional tool for drug discovery.

The most common software analysis tools available for measuring fluorescence images are for two-dimensional (2D) data that rely on manual settings for ...

Test Samples for Optimizing STORM Super-Resolution Microscopy

STORM is a recently developed super-resolution microscopy technique with up to 10 times better resolution than standard fluorescence microscopy techniques. However, as the image is acquired in a very different way than normal, by building up an image molecule-by-molecule, there are some significant challenges for users in trying to optimize their image acquisition. In order to aid this process and gain more insight into how STORM works we present the preparation of 3 test samples and the methodology of acquiring and processing STORM super-resolution images with typical resolutions of between 30-50 nm. By combining the test samples with the use of the freely available rainSTORM processing software it is possible to obtain a great deal of information about image quality and resolution. Using these metrics it is then possible to optimize the imaging procedure from the optics, to sample preparation, dye choice, buffer conditions, and image acquisition settings. We also show examples of some common problems that result in poor image quality, such as lateral drift, where the sample moves during image acquisition and density related problems resulting in the 'mislocalization' phenomenon.

We describe the preparation of three test samples and how they can be used to optimize and assess the performance of STORM microscopes. Using these examples we show how to acquire raw data and then process it to acquire super-resolution images in cells of approximately 30-50 nm resolution.

STORM is a recently developed super-resolution microscopy technique with up to 10 times better resolution than standard fluorescence microscopy ...

Sample Preparation for Single Virion Atomic Force Microscopy and Super-resolution Fluorescence Imaging

Immobilization of virions to glass surfaces is a critical step in single virion imaging. Here we present a technique&#160;adopted from single molecule imaging assays which allows adhesion of single virions to glass surfaces with specificity. This preparation is based on grafting the surface of the glass with a mixture of PLL-g-PEG and PLL-g-PEG-Biotin, adding a layer of avidin, and finally creating virion anchors through attachment of biotinylated virus specific antibodies. We have applied this technique across a range of experiments including atomic force microscopy (AFM) and super-resolution fluorescence imaging. This sample preparation method results in a control adhesion of the virions to the surface.

The attachment of virions to a surface is a requirement for single virion imaging by Super-resolution fluorescence imaging or atomic force microscopy (AFM). Here we demonstrate a sample preparation method for controlled adhesion of virions to glass surfaces suitable for use in AFM and super-resolution fluorescence imaging.

Immobilization of virions to glass surfaces is a critical step in single virion imaging. Here we present a technique&#160;adopted from single molecule ...

Generation of Plasmid Vectors Expressing FLAG-tagged Proteins Under the Regulation of Human Elongation Factor-1&#945; Promoter Using Gibson Assembly

Gibson assembly (GA) cloning offers a rapid, reliable, and flexible alternative to conventional DNA cloning methods. We used GA to create customized plasmids for expression of exogenous genes in mouse embryonic stem cells (mESCs). Expression of exogenous genes under the control of the SV40 or human cytomegalovirus promoters diminishes quickly after transfection into mESCs. A remedy for this diminished expression is to use the human elongation factor-1 alpha (hEF1&#945;) promoter to drive gene expression. Plasmid vectors containing hEF1&#945; are not as widely available as SV40- or CMV-containing plasmids, especially those also containing N-terminal 3xFLAG-tags. The protocol described here is a rapid method to create plasmids expressing FLAG-tagged CstF-64 and CstF-64 mutant under the expressional regulation of the hEF1&#945; promoter. GA uses a blend of DNA exonuclease, DNA polymerase and DNA ligase to make cloning of overlapping ends of DNA fragments possible. Based on the template DNAs we had available, we designed our constructs to be assembled into a single sequence. Our design used four DNA fragments: pcDNA 3.1 vector backbone, hEF1&#945; promoter part 1, hEF1&#945; promoter part 2 (which contained 3xFLAG-tag purchased as a double-stranded synthetic DNA fragment), and either CstF-64 or specific CstF-64 mutant. The sequences of these fragments were uploaded to a primer generation tool to design appropriate PCR primers for generating the DNA fragments. After PCR, DNA fragments were mixed with the vector containing the selective marker and the GA cloning reaction was assembled. Plasmids from individual transformed bacterial colonies were isolated. Initial screen of the plasmids was done by restriction digestion, followed by sequencing. In conclusion, GA allowed us to create customized plasmids for gene expression in 5 days, including construct screens and verification.

Synthesis of custom plasmids is labor and time consuming. This protocol describes the use of Gibson assembly cloning to reduce the work and duration of custom DNA cloning procedure. The protocol described also produces reliable tagged protein constructs for mammalian expression at similar cost to the traditional cut-and-paste DNA cloning.

Gibson assembly (GA) cloning offers a rapid, reliable, and flexible alternative to conventional DNA cloning methods. We used GA to create customized ...

An Alternative Approach for Sample Preparation with Low Cell Number for TEM Analysis

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, especially cells in suspension such as hematopoietic stem cells (HSCs), remains limited due to the requirement of a high cell number during sample preparation. There are a few cytospin or monolayer approaches for TEM analysis from scarce samples, but these approaches fail to get significant quantitative data from the limited number of cells. Here, an alternative and novel approach for sample preparation in TEM studies is described for rare cell populations that enables quantitative analysis.
A relatively low cell number, i.e., 10,000 HSCs, was successfully used for TEM analysis compared to the millions of cells typically used for TEM studies. In particular, Evans blue staining was performed after paraformaldehyde-glutaraldehyde (PFA-GA) fixation to visualize the tiny cell pellet, which facilitated embedding in agarose. Clusters of numerous cells were observed in ultra-thin sections. The cells had a well preserved morphology, and the ultra-structural details of the Golgi complex and several mitochondria were visible. This efficient, easy and reproducible protocol allows sample preparation from a low cell number and can be used for qualitative and quantitative TEM analysis on rare cell populations from limited biological samples.

Here, we present a protocol to prepare samples with low cell numbers for transmission electron microscopy (TEM) analysis.

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, ...