The authors would like to acknowledge Chan-Sien Lay for providing pictures of purified microcrystals, Daniel Eriksson and Tom Caradoc-Davies for support at the MX2 beamline of the Australian Synchrotron, and Kathryn Flanagan and Andrew Fryga from the FlowCore facility at Monash University for their invaluable assistance.

<ol>
	<li>Tari, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+utility+of+structural+biology+in+drug+discovery.">The utility of structural biology in drug discovery.</a> Methods Mol Bio (Clifton, N.J). 841, 1-27 (2012).</li><li>Gati, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serial+crystallography+on+in+vivo+grown+microcrystals+using+synchrotron+radiation.">Serial crystallography on in vivo grown microcrystals using synchrotron radiation.</a> IUCrJ. 1 (2), (2014).</li><li>Redecke, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Natively+inhibited+Trypanosoma+brucei+cathepsin+B+structure+determined+by+using+an+X-ray+laser.">Natively inhibited Trypanosoma brucei cathepsin B structure determined by using an X-ray laser.</a> Science. 339 (2013), 227-230 (2013).</li><li>Shi, D., Nannenga, B. L., Iadanza, M. G., Gonen, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+electron+crystallography+of+protein+microcrystals.">Three-dimensional electron crystallography of protein microcrystals.</a> eLife. 2, e01345 (2013).</li><li>Evans, G., Axford, D., Waterman, D., Owen, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macromolecular+microcrystallography.">Macromolecular microcrystallography.</a> Crystallog. Rev. 17 (2), 105-142 (2011).</li><li>Smith, J. L., Fischetti, R. F., Yamamoto, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro-crystallography+comes+of+age.">Micro-crystallography comes of age.</a> Curr Opin Struct Biol. 22 (5), 602-612 (2012).</li><li>Boudes, M., Garriga, D., Coulibaly, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reflections+on+the+Many+Facets+of+Protein+Microcrystallography.">Reflections on the Many Facets of Protein Microcrystallography.</a> Aust J Chem. 67 (12), 1793-1806 (2014).</li><li>Nelson, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+the+cross-beta+spine+of+amyloid-like+fibrils.">Structure of the cross-beta spine of amyloid-like fibrils.</a> Nature. 435 (7043), 773-778 (2005).</li><li>Coulibaly, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+organization+of+cypovirus+polyhedra.">The molecular organization of cypovirus polyhedra.</a> Nature. 446 (7131), 97-101 (2007).</li><li>Coulibaly, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+atomic+structure+of+baculovirus+polyhedra+reveals+the+independent+emergence+of+infectious+crystals+in+DNA+and+RNA+viruses.">The atomic structure of baculovirus polyhedra reveals the independent emergence of infectious crystals in DNA and RNA viruses.</a> Proc Natl Acad Sci U S A. 106 (52), 22205-22210 (2009).</li><li>Johansson, L. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+a+photosynthetic+reaction+centre+determined+by+serial+femtosecond+crystallography.">Structure of a photosynthetic reaction centre determined by serial femtosecond crystallography.</a> Nat Comm. 4, (2013).</li><li>Li, D., Boland, C., Aragao, D., Walsh, K., Caffrey, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Harvesting+and+Cryo-cooling+Crystals+of+Membrane+Proteins+Grown+in+Lipidic+Mesophases+for+Structure+Determination+by+Macromolecular+Crystallography.">Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography.</a> J Vis Exp. 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X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+crystallography+at+X-ray+free-electron+lasers:+the+next+generation+of+structural+biology.">In vivo crystallography at X-ray free-electron lasers: the next generation of structural biology.</a> Phil Trans R Soc B. 369 (1647), 20130497 (2014).</li><li>Duszenko, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+protein+crystallization+in+combination+with+highly+brilliant+radiation+sources+offers+novel+opportunities+for+the+structural+analysis+of+post-translationally+modified+eukaryotic+proteins.">In vivo protein crystallization in combination with highly brilliant radiation sources offers novel opportunities for the structural analysis of post-translationally modified eukaryotic proteins.</a> Acta Cryst. F. 71 (8), 929-937 (2015).</li><li>Axford, D., Ji, X., Stuart, D. I., Sutton, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+cellulo+structure+determination+of+a+novel+cypovirus+polyhedrin.">In cellulo structure determination of a novel cypovirus polyhedrin.</a> Acta Cryst D. 70 (5), 1435-1441 (2014).</li><li>Sawaya, M. 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W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=iMOSFLM:+a+new+graphical+interface+for+diffraction-image+processing+with+MOSFLM.">iMOSFLM: a new graphical interface for diffraction-image processing with MOSFLM.</a> Acta Cryst D. 67, 271-281 (2011).</li><li>Kabsch, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=XDS.">XDS.</a> Acta Cryst D. 66, 125-132 (2010).</li><li>French, S., Wilson, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+treatment+of+negative+intensity+observations.">On the treatment of negative intensity observations.</a> Acta Cryst.A. 34, 517-525 (1978).</li><li>Winn, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overview+of+the+CCP4+suite+and+current+developments.">Overview of the CCP4 suite and current developments.</a> Acta Cryst D. 67, 235-242 (2011).</li><li>Foadi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clustering+procedures+for+the+optimal+selection+of+data+sets+from+multiple+crystals+in+macromolecular+crystallography.">Clustering procedures for the optimal selection of data sets from multiple crystals in macromolecular crystallography.</a> Acta Cryst D. 69 (8), 1617-1632 (2013).</li><li>Rey, F. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Virology:+holed+up+in+a+natural+crystal.">Virology: holed up in a natural crystal.</a> Nature. 446 (7131), 35-37 (2007).</li><li>Sch&#246;nherr, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+investigation+of+dynamic+protein+crystallization+in+living+cells.">Real-time investigation of dynamic protein crystallization in living cells.</a> Struct Dyn. 2 (4), 041712 (2015).</li><li>Hasegawa, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+crystallization+of+human+IgG+in+the+endoplasmic+reticulum+of+engineered+Chinese+hamster+ovary+(CHO)+cells.">In vivo crystallization of human IgG in the endoplasmic reticulum of engineered Chinese hamster ovary (CHO) cells.</a> J Biol Chem. 286 (22), 19917-19931 (2011).</li><li>Ishchenko, A., Cherezov, V., Liu, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+Delivery+of+Protein+Microcrystals+in+Lipidic+Cubic+Phase+for+Serial+Femtosecond+Crystallography.">Preparation and Delivery of Protein Microcrystals in Lipidic Cubic Phase for Serial Femtosecond Crystallography.</a> J Vis Exp. 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The authors have nothing to disclose.

This protocol provides two approaches to analyze microcrystals with the aim of facilitating the analysis of very small crystals that would have been overlooked in the past.
Critical steps for microcrystal purification 
The presented protocol has been optimized using Bombyx mori CPV1 polyhedrin expressed in Sf9 cells as a model system. However, in vivo microcrystals display a great variability in mechanical resistance. For instance, cathepsin B needle-lik...

The use of X-ray crystallography for the determination of high-resolution structures of biological macromolecules has experienced a steady progression over the last two decades. The growing uptake of X-ray crystallography by non-expert researchers exemplifies the democratization of this approach in many fields of life sciences1.
Historically, crystals with dimensions below ~10 &#181;m have been considered as challenging, if not unusable, for structure determination. The increasing availability of dedicated microfocus beamlinesat synchrotron radiation sources worldwide and technological advances, such as the development of tools to manipulate microcrystals, have removed much of these barriers that stymied the wide use of X-ray microcrystallography. Advances in serial X-ray microcrystallography2,3 and micro electron diffraction4 have shown that the use of micro- and nanocrystals for structure determination is not only feasible but also sometimes preferable to the use of large crystals5,6,7.
These advances were first applied to the study of peptides8 and natural crystals produced by insect viruses9,10. They are now used for a diverse range of biological macromolecules including the most difficult systems such as membrane proteins and large complexes11. To facilitate the analysis of these microcrystals, they have been analyzed in meso, particularly membrane proteins12 and in microfluidics chips13.
The availability of these novel microcrystallography methodologies has raised the possibility of using in vivo crystallization as a new route for structural biology14,15,16 offering an alternative to classical in vitro crystallogenesis. Unfortunately, even when in vivo crystals can be produced, several obstacles remain such as the degradation or loss of ligands during the purification from cells, difficulty in the manipulation and visualization of the crystals at the synchrotron beamline and tedious X-ray diffraction experiments. As an alternative crystals have also been analyzed directly within the cell without any purification step17,18,19. A comparative analysis suggests that such in cellulo approaches may be more efficient than the analysis of purified crystals and yield data of higher resolution20.
This protocol is intended to assist researchers new to protein microcrystallography. It provides methodologies focusing on sample preparation and manipulation for X-ray diffraction experiments at a synchrotron beamline. Two options are proposed using isolated crystals for classical microcrystallography or crystal-containing cells sorted by flow cytometry for in cellulo analysis (Figure 1).

<table border="0" cellpadding="0" cellspacing="0" width="629">
	<colgroup>
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		<col />
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	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sf9 cells</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SF900-SFM insect medium</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1L cell culture flask</td>
			<td style="width:127px;">Thermofisher Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Shaking incubator for insect cell culture</td>
			<td style="width:127px;">Eppendorf</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">50mL conical tubes</td>
			<td style="width:127px;">Falcon</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Centrifuge with swing buckets for 50mL tubes</td>
			<td style="width:127px;">Eppendorf</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sonicator equiped with a 19mm probe</td>
			<td>MSE Soniprep 150&#160;</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Glass slides</td>
			<td style="width:127px;">Hampton Research</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hemacytometer</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Propidium iodide</td>
			<td style="width:127px;">Thermofisher Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">BD Influx cell sorter&#160;</td>
			<td style="width:127px;">BD Biosciences</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hampton Heavy atom screens</td>
			<td style="width:127px;">Hampton Research</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microcentrifuge</td>
			<td style="width:127px;">Eppendorf</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Micromesh</td>
			<td style="width:127px;">Mitigen</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">700/25 meshes offer a larger surface. Indexed meshes can be purchased for systematic studies.</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:216px;">Paper wick</td>
			<td style="width:127px;">Mitigen</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">The size of the paper wick can be varied for optimal flow. This will largely depend on the nature of the crystals and cryoprotectant used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethylene glycol</td>
			<td style="width:127px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Trypan blue</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="231">
			<td height="231" style="height:231px;width:216px;">MX2 microfocus beamline</td>
			<td style="width:127px;">Australian Synchrotron</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">A list of available microfocus beamlines can be found in Boudes et al. (2014) Reflections on the Many Facets of Protein 
			Microcrystallography. Australian Journal of Chemistry 67 (12), 1793&#8211;1806, 
			doi:10.1071/CH14455.</td>
		</tr>
	</tbody>
</table>

microcrystallography of protein crystals and in cellulo diffraction

The advent of high-quality microfocus beamlines at many synchrotron facilities has permitted the routine analysis of crystals smaller than 10 &#181;m in their largest dimension, which used to represent a challenge. We present two alternative workflows for the structure determination of protein microcrystals by X-ray crystallography with a particular focus on crystals grown in vivo. The microcrystals are either extracted from cells by sonication and purified by differential centrifugation, or analyzed in cellulo after cell sorting by flow cytometry of crystal-containing cells. Optionally, purified crystals or crystal-containing cells are soaked in heavy atom solutions for experimental phasing. These samples are then prepared for diffraction experiments in a similar way by application onto a micromesh support and flash cooling in liquid nitrogen. We briefly describe and compare serial diffraction experiments of isolated microcrystals and crystal-containing cells using a microfocus synchrotron beamline to produce datasets suitable for phasing, model building and refinement.
These workflows are exemplified with crystals of the Bombyx mori cypovirus 1 (BmCPV1) polyhedrin produced by infection of insect cells with a recombinant baculovirus. In this case study, in cellulo analysis is more efficient than analysis of purified crystals and yields a structure in ~8 days from expression to refinement.

An overview of both alternative methods for structure determination using in vivo microcrystals is presented (Figure 1). Polyhedra can easily be purified by sonication and centrifugation. Due to their density, they form a layer at the bottom of the tube underneath a layer of debris that can be removed by pipetting (Figure 3a and 3b). The sample is then subjected to several rounds of sonication and washes...

Watch this Scientific Journal Video about Microcrystallography of Protein Crystals and In Cellulo Diffraction at JoVE.com

Microcrystallography of Protein Crystals and In Cellulo Diffraction

A protocol is presented for X-ray crystallography using protein microcrystals. Two examples analyzing in vivo-grown microcrystals after purification or in cellulo are compared.

Microcrystallography of Protein Crystals and In Cellulo Diffraction

The advent of high-quality microfocus beamlines at many synchrotron facilities has permitted the routine analysis of crystals smaller than 10 &#181;m in ...

microcrystallography-of-protein-crystals-and-in-cellulo-diffraction

Universidad de Cartagena UDEC

Research

JoVE Journal

Biochemistry

9.0K Views.  Monash University. A protocol is presented for X-ray crystallography using protein microcrystals. Two examples analyzing in vivo-grown microcrystals after purification or in cellulo are compared.

Video: Microcrystallography of Protein Crystals and In Cellulo Diffraction

Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay

Protein-protein interactions are involved in thousands of cellular processes and occur in distinct spatial context. Traditionally, co-immunoprecipitation is a popular technique to detect protein-protein interactions. Subsequent Western blot analysis is the most common method to visualize co-immunoprecipitated proteins. Recently, the proximity ligation assay has become a powerful tool to visualize protein-protein interactions in situ and provides the possibility to quantify protein-protein interactions by this method. Similar to conventional immunocytochemistry, the proximity ligation assay technique is also based on the accessibility of primary antibodies to the antigens, but in contrast, proximity ligation assay detects protein-protein interactions with a unique technique involving rolling-circle PCR, while conventional immunocytochemistry only shows co-localization of proteins.
Nuclear factor 90 (NF90) and RNA-binding motif protein 3 (RBM3) have been previously demonstrated as interacting partners. They are predominantly localized in the nucleus, but also migrate into the cytoplasm and regulate signaling pathways in the cytoplasmic compartment. Here, we compared NF90-RBM3 interaction in both the nucleus and the cytoplasm by co-immunoprecipitation and proximity ligation assay. In addition, we discussed the advantages and limitations of these two techniques in visualizing protein-protein interactions in respect to spatial distribution and the properties of protein-protein interactions.

Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay

Protein-protein interactions can occur in both the nucleus and the cytoplasm of a cell. To investigate these interactions, traditional co-immunoprecipitation and modern proximity ligation assay are applied. In this study, we compare these two methods to visualize the distribution of NF90-RBM3 interactions in the nucleus and the cytoplasm.

Protein-protein interactions are involved in thousands of cellular processes and occur in distinct spatial context. Traditionally, co-immunoprecipitation ...

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

Growing Protein Crystals with Distinct Dimensions Using Automated Crystallization Coupled with In Situ Dynamic Light Scattering

The automated crystallization device is a patented technique1 especially developed for monitoring protein crystallization experiments with the aim to precisely maneuver the nucleation and crystal growth towards desired sizes of protein crystals. The controlled crystallization is based on sample investigation with in situ Dynamic Light Scattering (DLS) while all visual changes in the droplet are monitored online with the help of a microscope coupled to a CCD camera, thus enabling a full investigation of the protein droplet during all stages of crystallization. The use of in situ DLS measurements throughout the entire experiment allows a precise identification of the highly supersaturated protein solution transitioning to a new phase &#8211; the formation of crystal nuclei. By identifying the protein nucleation stage, the crystallization can be optimized from large protein crystals to the production of protein microcrystals. The experimental protocol shows an interactive crystallization approach based on precise automated steps such as precipitant addition, water evaporation for inducing high supersaturation, and sample dilution for slowing induced homogeneous nucleation or reversing phase transitions.

Growing Protein Crystals with Distinct Dimensions Using Automated Crystallization Coupled with In Situ Dynamic Light Scattering

Here we present a protocol for controlled production of protein microcrystals. The process uses an automated device allowing controlled manipulation of several crystallization parameters. The protein crystallization is carried-out by controlled and automated addition of crystallization solutions while monitoring and investigating the radius distribution of particles in the crystallization droplet.

The automated crystallization device is a patented technique1 especially developed for monitoring protein crystallization experiments with the aim to ...

2 in 1: One-step Affinity Purification for the Parallel Analysis of Protein-Protein and Protein-Metabolite Complexes

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of protein-protein interactions (PPI) is no novelty, experimental approaches aiming to characterize endogenous protein-metabolite interactions (PMI) constitute a rather recent development. Herein, we present a protocol that allows simultaneous characterization of the PPI and PMI of a protein of choice, referred to as bait. Our protocol was optimized for Arabidopsis cell cultures and combines affinity purification (AP) with mass spectrometry (MS)-based protein and metabolite detection. In short, transgenic Arabidopsis lines, expressing bait protein fused to an affinity tag, are first lysed to obtain a native cellular extract. Anti-tag antibodies are used to pull down protein and metabolite partners of the bait protein. The affinity-purified complexes are extracted using a one-step methyl tert-butyl ether (MTBE)/methanol/water method. Whilst metabolites separate into either the polar or the hydrophobic phase, proteins can be found in the pellet. Both metabolites and proteins are then analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS or UPLC-MS/MS). Empty-vector (EV) control lines are used to exclude false positives. The major advantage of our protocol is that it enables identification of protein and metabolite partners of a target protein in parallel in near-physiological conditions (cellular lysate). The presented method is straightforward, fast, and can be easily adapted to biological systems other than plant cell cultures.

Protein-protein and protein-metabolite interactions are crucial for all cellular functions. Herein, we describe a protocol that allows parallel analysis of these interactions with a protein of choice. Our protocol was optimized for plant cell cultures and combines affinity purification with mass spectrometry-based protein and metabolite detection.

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of ...

Measuring and Interpreting Oxygen Consumption Rates in Whole Fly Head Segments

Regulated metabolic activity is essential for the normal functioning of living cells. Indeed, altered metabolic activity is causally linked with the progression of cancer, diabetes, neurodegeneration, and aging to name a few. For instance, changes in mitochondrial activity, the cell&#39;s metabolic powerhouse, have been characterized in many such diseases. Generally, the oxygen consumption rates of mitochondria were considered a reliable readout of mitochondrial activity and measurements in some of these studies were based on isolated mitochondria or cells. However, such conditions may not represent the complexity of a whole tissue. Recently, we have developed a novel method that enables the dynamic measurement of oxygen consumption rates from whole isolated fly heads. By utilizing this method, we have recorded lower oxygen consumption rates of the whole head segment in young versus aged flies. Secondly, we have discovered that lysine deacetylase inhibitors rapidly alter the oxygen consumption in the whole head. Our novel technique may therefore aid in uncovering new properties of various drugs, which may impact metabolic rates. Furthermore, our method may give a better understanding of metabolic behavior in an experimental setup that more closely resembles physiological states.

Measuring alterations in metabolic rates is central to understanding the progression of various diseases and aging. Here, we present a novel technique to measure whole head oxygen consumption that more closely resembles the physiological state and may aid in revealing novel drugs that modify mitochondrial activity.

Regulated metabolic activity is essential for the normal functioning of living cells. Indeed, altered metabolic activity is causally linked with the ...

High Sensitivity Measurement of Transcription Factor-DNA Binding Affinities by Competitive Titration Using Fluorescence Microscopy

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing approaches suffer from significant limitations, we have developed a new method for determining TF-DNA binding affinities with high sensitivity on a large scale. The assay relies on the established fluorescence anisotropy (FA) principle but introduces important technical improvements. First, we measure a full FA competitive titration curve in a single well by incorporating TF and a fluorescently labeled reference DNA in a porous agarose gel matrix. Unlabeled DNA oligomer is loaded on the top as a competitor and, through diffusion, forms a spatio-temporal gradient. The resulting FA gradient is then read out using a customized epifluorescence microscope setup. This improved setup greatly increases the sensitivity of FA signal detection, allowing both weak and strong binding to be reliably quantified, even for molecules of similar molecular weights. In this fashion, we can measure one titration curve per well of a multi-well plate, and through a fitting procedure, we can extract both the absolute dissociation constant (KD) and active protein concentration. By testing all single-point mutation variants of a given consensus binding sequence, we can survey the entire binding specificity landscape of a TF, typically on a single plate. The resulting position weight matrices (PWMs) outperform those derived from other methods in predicting in vivo TF occupancy. Here, we present a detailed guide for implementing HiP-FA on a conventional automated fluorescent microscope and the data analysis pipeline.

Here we present a novel method for determining binding affinities at equilibrium and in solution with high sensitivity on a large scale. This improves the quantitative analysis of transcription factor-DNA binding. The method is based on automated fluorescence anisotropy measurements in a controlled delivery system.

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing ...

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and the degradation of target proteins in live cells. By using short (pulse) radiolabeling times (&lt;30 min) and tightly controlled chase times, it is possible to label only a small fraction of the total protein pool and follow its folding. When combined with nonreducing/reducing SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoprecipitation with (conformation-specific) antibodies, folding processes can be examined in great detail. This system has been used to analyze the folding of proteins with a huge variation in properties such as soluble proteins, single and multi-pass transmembrane proteins, heavily N- and O-glycosylated proteins, and proteins with and without extensive disulfide bonding. Pulse-chase methods are the basis of kinetic studies into a range of additional features, including co- and posttranslational modifications, oligomerization, and polymerization, essentially allowing the analysis of a protein from birth to death. Pulse-chase studies on protein folding are complementary with other biochemical and biophysical methods for studying proteins in vitro by providing increased temporal resolution and physiological information. The methods as described within this paper are adapted easily to study the folding of almost any protein that can be expressed in mammalian or insect-cell systems.

Here we describe a protocol for a general pulse-chase method that allows the kinetic analysis of folding, transport, and degradation of proteins to be followed in live cells.

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and ...

Fully Autonomous Characterization and Data Collection from Crystals of Biological Macromolecules

High-brilliance X-ray beams coupled with automation have&#160;led to the use of synchrotron-based macromolecular X-ray crystallography (MX) beamlines for even the most challenging projects in structural biology. However, most facilities still require the presence of a scientist on site to perform the experiments. A new generation of automated beamlines dedicated to the fully automatic characterization of, and data collection from, crystals of biological macromolecules has recently been developed. These beamlines represent a new tool for structural biologists to screen the results of initial crystallization trials and/or the collection of large numbers of diffraction data sets, without users having to control the beamline themselves. Here we show how to set up an experiment for automatic screening and data collection, how an experiment is performed at the beamline, how the resulting data sets are processed, and how, when possible, the crystal structure of the biological macromolecule is solved.

Here, we describe how to use the automated screening and data collection options available at some synchrotron beamlines. Scientists send cryocooled samples to the synchrotron, and the diffraction properties are screened, the data sets are collected and processed and, where possible, a structure solution is carried out&#8212;all without human intervention.

High-brilliance X-ray beams coupled with automation have&#160;led to the use of synchrotron-based macromolecular X-ray crystallography (MX) beamlines for ...

Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA is a novel transcription activator found specifically in the obligate intracellular bacterial pathogen Chlamydia. Protein pulldown assays using affinity beads have revealed that GrgA binds two &#963; factors, namely &#963;66 and &#963;28, which recognize different sets of promoters for genes whose products are differentially required at developmental stages. We have used BLI to confirm and further characterize the interactions. BLI demonstrates several advantages over pulldown: 1) It reveals real-time association and dissociation between binding partners, 2) It generates quantitative kinetic parameters, and 3) It can detect bindings that pulldown assays often fail to detect. These characteristics have enabled us to deduce the physiological roles of GrgA in gene expression regulation in Chlamydia, and possible detailed interaction mechanisms. We envision that this relatively affordable technology can be extremely useful for studying transcription and other biological processes.

Application of Biolayer Interferometry BLI for Studying Protein-Protein Interactions in Transcription

Interactions of transcription factors (TFs) with the RNA polymerase are usually studied using pulldown assays. We apply a Biolayer Interferometry (BLI) technology to characterize the interaction of GrgA with the chlamydial RNA polymerase. Compared to pulldown assays, BLI detects real-time association and dissociation, offers higher sensitivity, and is highly quantitative.

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA ...

Creating Highly Specific Chemically Induced Protein Dimerization Systems by Stepwise Phage Selection of a Combinatorial Single-Domain Antibody Library

Protein dimerization events that occur only in the presence of a small-molecule ligand enable the development of small-molecule biosensors for the dissection and manipulation of biological pathways. Currently, only a limited number of chemically induced dimerization (CID) systems exist and engineering new ones with desired sensitivity and selectivity for specific small-molecule ligands remains a challenge in the field of protein engineering. We here describe a high throughput screening method, combinatorial binders-enabled selection of CID (COMBINES-CID), for the de novo engineering of CID systems applicable to a large variety of ligands. This method uses the two-step selection of a phage-displayed combinatorial nanobody library to obtain 1) &#34;anchor binders&#34; that first bind to a ligand of interest and then 2) &#34;dimerization binders&#34; that only bind to anchor binder-ligand complexes. To select anchor binders, a combinatorial library of over 109 complementarity-determining region (CDR)-randomized nanobodies is screened with a biotinylated ligand and hits are validated with the unlabeled ligand by bio-layer interferometry (BLI). To obtain dimerization binders, the nanobody library is screened with anchor binder-ligand complexes as targets for positive screening and the unbound anchor binders for negative screening. COMBINES-CID is broadly applicable to select CID binders with other immunoglobulin, non-immunoglobulin, or computationally designed scaffolds to create biosensors for in vitro and in vivo detection of drugs, metabolites, signaling molecules, etc.

Creating chemically induced protein dimerization systems with desired affinity and specificity for any given small molecule ligand would have many biological sensing and actuation applications. Here, we describe an efficient, generalizable method for de novo engineering of chemically induced dimerization systems via the stepwise selection of a phage-displayed combinatorial single-domain antibody library.

Microcrystallography of Protein Crystals and In Cellulo Diffraction

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Chapters in this video

Visualization of Protein-protein Interaction in Nuclear and Cytoplasmic Fractions by Co-immunoprecipitation and In Situ Proximity Ligation Assay

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Growing Protein Crystals with Distinct Dimensions Using Automated Crystallization Coupled with In Situ Dynamic Light Scattering

2 in 1: One-step Affinity Purification for the Parallel Analysis of Protein-Protein and Protein-Metabolite Complexes

Measuring and Interpreting Oxygen Consumption Rates in Whole Fly Head Segments

High Sensitivity Measurement of Transcription Factor-DNA Binding Affinities by Competitive Titration Using Fluorescence Microscopy

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase

Fully Autonomous Characterization and Data Collection from Crystals of Biological Macromolecules

Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription

Creating Highly Specific Chemically Induced Protein Dimerization Systems by Stepwise Phage Selection of a Combinatorial Single-Domain Antibody Library