This research was supported by grants from the Intelligent Synthetic Biology Center of Global Frontier Project (2011-0031944) and the KRIBB Research Initiative Program.

1. Preparation of Biosensor
<ol>
	<li>Construct the plasmid pET21a(+)-CFP-MBP-YFP-His6 by following the previously-established protocol2.</li>
	<li>Inoculate 5 ml of Luria broth (LB) with a single colony of an Escherichia coli DE3 strain and incubate at 37 &#176;C for 16 hr with shaking.</li>
	<li>Transfer 1 ml of the O/N culture into a 500-ml flask containing 100 ml LB and incubate at 37 &#176;C in a shaking incubator until the optical density at 600 nm (OD600) reaches 0.5 (about 3 hr).</li>
	<li>Harvest the cells in a 50-ml conical tube by centrifugation at 1,000 &#215; g for 20 min at 4 &#176;C.</li>
	<li>Resuspend the pellet quickly in each tube with 50 ml ice-cold distilled water (DW) and centrifuge at 1,000&#160;&#215; g for 20 min at 4 &#176;C.</li>
	<li>Resuspend the pellet in 50 &#956;l of ice-cold DW with 10% (v/v) glycerol by gently swirling until the solution (electrocompetent cells) reaches an OD600 of 100.</li>
	<li>Place the mixture of electrocompetent cells (50 &#956;l of the cells at an OD600 of 100) and 10 ng of the plasmid pET21a(+)-CFP-MBP-YFP-His6 in an ice-cold electroporation cuvette in an electroporation device and electroporate the mixture (18 kV/cm, 25 &#181;F).</li>
	<li>Quickly add 1 ml SOC medium to the cuvette and resuspend the cells gently, followed by recovery at 37 &#176;C for 1 hr with gentle shaking in a 15 ml round-bottom tube.</li>
	<li>Spread the cells on an LB plate containing 100 &#181;g/ml ampicillin and incubate at 37 &#176;C for 12 hr.</li>
	<li>Isolate a single colony using a loop and inoculate the colony in 10 ml of LB containing 100 &#181;g/ml ampicillin at 37 &#176;C in a shaker for 12 hr.</li>
	<li>Add 5 ml of the seed culture to 500 ml of LB containing 100 &#181;g/ml ampicillin and incubate the culture in a 37 &#176;C shaking incubator.</li>
	<li>Add 0.5 mM isopropyl &#946;-d-thiogalactoside (IPTG) when the OD600 reaches 0.5 and incubate the culture in a 37 &#176;C shaking incubator for 24 hr.</li>
	<li>Centrifuge the cells at 4,500 &#215; g for 20 min (4 &#176;C) and gently remove supernatant.</li>
	<li>Resuspend the pellet in 5 mL binding buffer (20 mM Tris-HCl, pH 8.0, 1 mM PMSF, 0.5 mM EDTA, and 1 mM DTT).</li>
	<li>Sonicate the cells on ice with six 10-sec bursts at 200-300 W, following each burst with 10 sec of cooling.</li>
	<li>Centrifuge the lysate at 10,000 &#215; g for 30 min at 4 &#176;C to pellet the cellular debris. Transfer supernatant (soluble protein) into a new collection tube.</li>
	<li>To achieve affinity purification of the FRET sensor proteins, load 4 ml of the cleared cell lysate onto a Ni-NTA affinity column (5-ml volume) and perform a chromatography assay using fast protein liquid chromatography (FPLC)18.</li>
	<li>Wash the column once with five column volumes of wash buffer I (50 mM phosphate buffer, 300 mM sodium chloride, 10 mM imidazole, pH 7.0).</li>
	<li>Repeat the wash step with five column volumes of wash buffer II (50 mM phosphate buffer, 300 mM sodium chloride, 20 mM imidazole, pH 7.0).</li>
	<li>Elute the sensor protein with five column volumes of elution buffer (50 mM phosphate buffer, 300 mM sodium chloride, 500 mM imidazole, pH 7.0).</li>
	<li>To concentrate and desalt the eluted sample, fill concentrator (membrane size of 10,000 MW) with up to 20 ml of sample and centrifuge for 10 min at 3,000 &#215; g. Refill concentrator with 0.8% phosphate-buffered saline (PBS). Repeat this step twice, first filling the concentrator with 20 ml of sample, and then refilling with PBS.</li>
	<li>Recover the concentrated and de-salted sensor protein and store it at -80 &#176;C.</li>
</ol>
2. Measurement of Sugar Content using the FRET Analyzer
NOTE: The details of the FRET analyzer construction were described in our previous work7.
<ol>
	<li>Prepare a detection solution of 0.8% PBS containing 0.2 &#181;M of the sensor proteins.</li>
	<li>Turn on the FRET analyzer. Press the &#34;UP&#34; button for 2 sec to calibrate the optimal temperature. Set the temperature to 53 &#176;C using the &#34;UP&#34; and &#34;DOWN&#34; buttons and press the &#34;SET&#34; button.</li>
	<li>For the calibration, press and hold the &#34;UP&#34; and &#34;DOWN&#34; buttons simultaneously for 2 sec. Confirm that the LED panel displays &#34;CALIB&#34; and press the &#34;SET&#34; button.</li>
	<li>Place a 12.5 &#215; 12.5 &#215; 45 mm (length &#215; width &#215; height) rectangular parallelepiped vessel (cuvette) containing only PBS buffer into a cuvette holder of the analyzer and press the &#34;SET&#34; button.</li>
	<li>Replace the cuvette with one containing only the detection solution (see 2.1) without sugar (maltose/sucrose) and press the &#34;SET&#34; button to calibrate the baseline.</li>
	<li>Replace the cuvette with one containing the detection solution with 10 mM sugar and press the &#34;SET&#34; button.</li>
	<li>To determine the sugar content of a beverage sample, put 1 ml beverage sample in a 1.5-ml microcentrifuge tube and centrifuge at 16,000 &#215; g for 1 min. 
	NOTE: FRET sensor-based fluorescence measurement has the advantage of not requiring special pre-treatment of the sample because only 1% (v/v) of the sample is included in the total volume. However, we recommend removing any material that may affect the fluorescence measurement (e.g., cells, insoluble particles, lipid, fat, or any material with autofluorescence). In addition, if a strong acid, strong base, cleaning agent (detergent), or emulsifying agent (emulsifier) is present at a high concentration and may affect the properties of the FRET biological sensor, it should be removed using an organic solvent or a neutralizer. For example, when dairy fat and emulsifiers are eliminated from frozen snacks, the samples are centrifuged in a microfuge tube at 16,000 &#215; g for 30 min, and the liquid between the bottom sediment and the top layer of dairy fat is extracted. An equal amount of hexane is then added, followed by centrifugation at 15,000 &#215; g for 30 min to eliminate lipids.</li>
	<li>Remove the supernatant with a 1-ml syringe and filter it through a syringe filter (pore size 0.2 &#181;m).</li>
	<li>Place 0.1 ml filtered beverage sample in a 1.5-ml microcentrifuge tube containing 0.9 ml PBS and vortex gently. 
	NOTE: It is critical to dilute the beverage sample properly. In this case, 1,000-fold dilution was performed so that the sugar concentration would fall within the dynamic range of the device. We recommend estimating the target sugar concentration in advance by referring to the sugar content in the label of the beverage.</li>
	<li>Add 5 &#181;l of the diluted beverage sample (1%, v/v) to a cuvette containing 0.495 ml of the detection solution.</li>
	<li>Place the cuvette in a cuvette holder of the FRET analyzer and preheat the sample solution to 53 &#176;C.</li>
	<li>Press the &#34;SET&#34; button to measure the sugar content. 
	Note It is possible to evaluate the FRET measurement using a multilabel plate reader or a fluorescence spectrophotometer equipped with a Peltier device for temperature control by reading the ratio at 488/535 nm7,8. For sucrose detection, follow the steps from 1.1 to 2.12 with a CSY-LH sensor2.</li>
</ol>

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U.S.A. 101 (29), 10554-10559 (2004).</li><li>Okumoto, S., Looger, L. L., Micheva, K. D., Reimer, R. J., Smith, S. J., Frommer, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+glutamate+release+from+neurons+by+genetically+encoded+surface-displayed+FRET+nanosensors.">Detection of glutamate release from neurons by genetically encoded surface-displayed FRET nanosensors.</a> Proc. Natl. Acad. Sci. 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The authors have nothing to disclose.

This protocol allows rapid and efficient quantification of the sugar content in beverage samples, using a custom-made FRET analyzer7 at an optimal temperature for FRET sensors. The analyzer was designed with a recently-developed, inexpensive 405-nm band ultraviolet-LED as the light source and two photodetectors with a silicon photodiode. This device is more cost-effective than other comparable fluorometers. The device showed high detection sensitivity, specifically when measuring the ratio of two emission wave...

F&#246;rster resonance energy transfer (FRET) has been widely used as a biometric sensor to detect small molecules such as sugars, calcium ions, and amino acids1-4. FRET biosensors contain fluorescent proteins, cyan fluorescent proteins (CFPs), and yellow fluorescent proteins (YFPs), which are fused to both ends of periplasmic-binding proteins (PBPs). Sugars bind to PBPs located in the middle of the FRET sensor, causing structural changes to the sensor that subsequently alter the distance and transition dipole orientation of the two fluorescent proteins at either end of the PBPs. This change enables quantitative analysis of sugar content by measuring the ratio of the emission wavelengths of EYFP (530 nm) and ECFP (480 nm). Owing to the high sensitivity, specificity, real-time monitoring capacity, and fast response time of FRET biosensors, these sensors are widely used in environmental, industrial, and medical applications5. Moreover, ratiometric measurement using FRET biosensors has important practical benefits, as it can be used to measure components in complex biological samples where the sensor concentration cannot be easily controlled and background fluorescence is always present.
Despite these advantages of FRET-based sensors for quantitative visualization, small structural changes with incomplete domain motion-transfer to the fluorescent proteins produce inherently weak signal intensity. This weak signal limits the application of FRET-based sensors for in vitro or in vivo analysis6. Consequently, most FRET biosensors require the use of expensive and highly sensitive equipment. Previously, we developed an inexpensive and portable FRET analyzer with capabilities similar to those of the existing fluorescence analyzers7. In this device, inexpensive 405-nm band ultraviolet light-emitting diode (LED) was used as the light source to cause excitation of the fluorescence signal, replacing an expensive lamp or laser. The detection system of the analyzer efficiently focuses the dissipating fluorescence signal onto two photodetectors with a silicon photodiode. In a more recent study, we showed that optimization of detection temperature at 50 - 55 &#176;C could significantly magnify the ratiometric FRET signal8. This temperature-specific signal enhancement, along with the custom-made FRET analyzer, enables the use of FRET sensors in more general diagnostic applications with rapid and high sensitivity.
In this protocol, we demonstrated the general applicability of the FRET analyzer under optimal FRET temperature conditions by quantifying the sugar content of commercially-available beverages. This protocol provides the details of the FRET device operation, as well as a brief description of sensor and sample preparation. We anticipate that this report will promote the potential application of the portable analyzer in small-scale laboratory environments and provide a foundation for further development of an inexpensive on-site diagnostic device with FRET-based biosensors.

<table border="0" cellpadding="0" cellspacing="0" width="1297">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">LB</td>
			<td style="width:191px;">BD</td>
			<td style="width:119px;">#244620</td>
			<td style="width:760px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:227px;">isopropyl &#946;-D-thiogalactoside (IPTG)</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:119px;">I6758</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">Ampicillin</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:119px;">A9518</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">Tri-HCl</td>
			<td style="width:191px;">Bioneer</td>
			<td style="width:119px;">C-9006-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">PMSF</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:119px;">78830</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">EDTA</td>
			<td style="width:191px;">Bioneer</td>
			<td style="width:119px;">C-9007</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">DTT</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:119px;">D0632</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">NaCl</td>
			<td style="width:191px;">Junsei</td>
			<td style="width:119px;">19015-0350</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:227px;">phosphate-buffered saline (PBS)</td>
			<td style="width:191px;">Gibco</td>
			<td style="width:119px;">70011-044</td>
			<td>0.8% NaCl, 0.02% KCl, 0.0144% Na2HPO4, 0.024% KH2OP4, pH 7.4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">SOC</td>
			<td style="width:191px;"></td>
			<td style="width:119px;"></td>
			<td>2% tryptone, 0.5% Yeast extract, 10 mM NaCl, 2.5 mM KCl, 10 mM MGCl2, 20 mM Glucose</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">Resource Q</td>
			<td>Amersham Biosciences</td>
			<td style="width:119px;">17-1177-01</td>
			<td>6 &#215; 30 mm anion-exchange chromatography column&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">HisTrap HP1</td>
			<td>Amersham Biosciences</td>
			<td style="width:119px;">29-0510-21</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">Quartz cuvette</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:119px;">Z802875</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">AK&#196;KTAFPLC</td>
			<td>Amersham Biosciences</td>
			<td style="width:119px;">18-1900-26</td>
			<td>a fast protein liquid chromatography (FPLC)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cary Eclipse</td>
			<td>VarianInc</td>
			<td style="width:119px;"></td>
			<td>a fluorescence spectrophotometer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">VICTOR&#160;&#160;</td>
			<td style="width:191px;">PerkinElmer</td>
			<td style="width:119px;">2030-0050</td>
			<td>a multilabel plate reader</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">E. coli JM109 (DE3)</td>
			<td style="width:191px;">Promega</td>
			<td style="width:119px;"></td>
			<td>Electrocompetent cells</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">A (Beverage)</td>
			<td style="width:191px;">Korea Yakult Co. (Korea)</td>
			<td style="width:119px;">Birak</td>
			<td>Fermented drinks</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">B (Beverage)</td>
			<td style="width:191px;">Lotte Foods (Korea)</td>
			<td style="width:119px;">Epro</td>
			<td>Soft drink</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:227px;">C (Beverage)</td>
			<td style="width:191px;">Lotte Foods (Korea)</td>
			<td style="width:119px;">Getoray</td>
			<td>Sports drink</td>
		</tr>
	</tbody>
</table>

highly sensitive and rapid fluorescence detection with a portable fret analyzer

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and amino acids. However, the innate weak signal intensity of FRET sensors is a major challenge that prevents their application in various fields and makes the use of expensive, high-end fluorometers necessary. Previously, we built a cost-effective, high-performance FRET analyzer that can specifically measure the ratio of two emission wavelength bands (530 and 480 nm) to achieve high detection sensitivity. More recently, it was discovered that FRET sensors with bacterial periplasmic binding proteins detect ligands with maximum sensitivity in the critical temperature range of 50 - 55 &#176;C. This report describes a protocol for assessing sugar content in commercially-available beverage samples using our portable FRET analyzer with a temperature-specific FRET sensor. Our results showed that the additional preheating process of the FRET sensor significantly increases the FRET ratio signal, to enable more accurate measurement of sugar content. The custom-made FRET analyzer and sensor were successfully applied to quantify the sugar content in three types of commercial beverages. We anticipate that further size reduction and performance enhancement of the equipment will facilitate the use of hand-held analyzers in environments where high-end equipment is not available.

To perform quantitative analysis of sugar content using the FRET analyzer, it is necessary to build a fitted curve estimating the target sugar concentration from the observed FRET ratio. Let r define the ratio of the emission intensity of CFP at 480 nm and the emission intensity of YFP generated at 530 nm (Eq. 1).
<img alt="Equation 1" src="/files/ftp_upload/54144/54144equation1.jpg" />
<p class="jove_content" fo:ke...

Watch this Scientific Journal Video about Highly Sensitive and Rapid Fluorescence Detection with a Portable FRET Analyzer at JoVE.com

Highly Sensitive and Rapid Fluorescence Detection with a Portable FRET Analyzer

This protocol describes the rapid and highly sensitive quantification of F&#246;rster resonance energy transfer (FRET) sensor data using a custom-made portable FRET analyzer. The device was used to detect maltose within a critical temperature range that maximizes detection sensitivity, enabling practical and efficient assessment of sugar content.

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and ...

highly-sensitive-rapid-fluorescence-detection-with-portable-fret

Universidad de Cartagena UDEC

Research

JoVE Journal

Biochemistry

9.0K Views.  Korea Research Institute of Bioscience and Biotechnology. This protocol describes the rapid and highly sensitive quantification of Förster resonance energy transfer (FRET) sensor data using a custom-made portable FRET analyzer. The device was used to detect maltose within a critical temperature range that maximizes detection sensitivity, enabling practical and efficient assessment of sugar content.

Video: Highly Sensitive and Rapid Fluorescence Detection with a Portable FRET Analyzer

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

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

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

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

Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability to provide more dynamic information about cells under physiological conditions than classical biochemical assays, this label-free real-time cell assay based on the electric impedance principle is attracting more attention during the past decade. However, its practical utilization may be limited due to the relatively expensive cost of measurement, in which costly consumable disposable gold microchips are used for the cell analyzer. In this protocol, we have developed a general strategy to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step. The proposed method has been tested and shown to be effective for the regeneration and repeated usage of commercial electronic plates at least three times, which will help researchers save on the high running cost of real-time cell assays.

This protocol describes a general strategy to regenerate commercial arrayed gold microelectrodes equipped for a label-free cell analyzer aimed at saving on the high running costs ofmicrochip-based assays. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step, which enables repeated usage of microchips.

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability ...

Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of the kinase activity of LRRK2 has been implicated in the pathogenesis of PD, it is essential to establish a method to evaluate the physiological levels of the kinase activity of LRRK2. Recent studies revealed that LRRK2 phosphorylates members of the Rab GTPase family, including Rab10, under physiological conditions. Although the phosphorylation of endogenous Rab10 by LRRK2 in cultured cells could be detected by mass spectrometry, it has been difficult to detect it by immunoblotting due to the poor sensitivity of currently available phosphorylation-specific antibodies for Rab10. Here, we describe a simple method of detecting the endogenous levels of Rab10 phosphorylation by LRRK2 based on immunoblotting utilizing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with a phosphate-binding tag (P-tag), which is N-(5-(2-aminoethylcarbamoyl)pyridin-2-ylmetyl)-N,N&#39;,N&#39;-tris(pyridin-2-yl-methyl)-1,3-diaminopropan-2-ol. The present protocol not only provides an example of the methodology utilizing the P-tag but also enables the assessment of how mutations as well as inhibitor treatment/administration or any other factors alter the downstream signaling of LRRK2 in cells and tissues.

The present study describes a simple method of detecting endogenous levels of Rab10 phosphorylation by leucine-rich repeat kinase 2.

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of ...

Highly Sensitive and Quantitative Detection of Proteins and Their Isoforms by Capillary Isoelectric Focusing Method

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides an alternative strategy, capillary isoelectric focusing (cIEF), with many advantages compared to conventional immunoblotting. This is an antibody-based, automated, rapid, and quantitative method in which a complete western blotting procedure takes place inside an ultrathin capillary. This technique does not require a gel to transfer to a membrane, stripping of blots, or x-ray films, which are typically required for conventional immunoblotting. Here, proteins are separated according to their charge (isoelectric point; pI), using less than a microliter (400 nL) of total protein lysate. After electrophoresis, proteins are immobilized onto the capillary walls by ultraviolet light treatment, followed by primary and secondary (horseradish peroxidase (HRP) conjugated) antibody incubation, whose binding is detected through enhanced chemiluminescence (ECL), generating a light signal that can be captured and recorded by a charge-coupled device (CCD) camera. The digital image can be analyzed and quantified (peak area) using software. This high throughput procedure can handle 96 samples at a time; is highly sensitive, with protein detection in the picogram range; and produces highly reproducible results because of automation. All of these aspects are extremely valuable when the quantity of samples (e.g., tissue samples and biopsies) is a limiting factor. The technique has wider applications as well, including screening of drugs or antibodies, biomarker discovery, and diagnostic purposes.

Capillary isoelectric focusing is an antibody-based, ultrasensitive, high throughput technique, enabling detailed characterization of proteins and their isoforms from extremely small biological samples. The following describes a protocol for detection and quantification of specific proteins and their isoforms in an automated and robotized manner.

Immunoblotting has become a routine technique in many laboratories for protein characterization from biological samples. The following protocol provides ...

Detection of Detergent-sensitive Interactions Between Membrane Proteins

Our ability to explore protein-protein interactions is the key to understanding regulatory connections in the cell. However, detection of protein-protein interactions in many cases is associated with significant experimental challenges. In particular, sorting receptors interact with their protein cargo in the lumen of the membrane compartments often in a detergent-sensitive fashion, making co-immunoprecipitation of these proteins unusable. Binding of the sorting receptor sortilin to glucose transporter GLUT4 may serve as an example of weak luminal interactions between membrane proteins. Here, we describe a fast, simple, and inexpensive assay to validate the interaction between sortilin and GLUT4. For that, we have designed and chemically synthesized the myc-tagged peptide corresponding to the potential sortilin-binding epitope in the luminal part of GLUT4. Sortilin tagged with six histidines was expressed in mammalian cells, and isolated from cell lysates using Cobalt beads. Sortilin immobilized on the beads was incubated with the peptide solution at different pH values, and the eluted material was analyzed by Western blotting. This assay can be easily adapted to study other detergent-sensitive protein-protein interactions.

We describe a protocol for detection of detergent-sensitive interactions between membrane proteins using binding of the sorting receptor, sortilin, to the first luminal loop of the glucose transporter protein, GLUT4, as an example.

Our ability to explore protein-protein interactions is the key to understanding regulatory connections in the cell. However, detection of protein-protein ...

Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and  GTPase-linked Immunosorbent Assay

The Rho GTPase family belongs to the Ras superfamily and includes approximately 20 members in humans. Rho GTPases are important in the regulation of diverse cellular functions, including cytoskeletal dynamics, cell motility, cell polarity, axonal guidance, vesicular trafficking, and cell cycle control. Changes in Rho GTPase signaling play an essential regulatory role in many pathological conditions, such as&#160;cancer, central nervous system diseases, and immune system-dependent diseases. The posttranslational modification of Rho GTPases (i.e., prenylation by mevalonate pathway intermediates) and GTP binding are key factors which affect the activation of this protein. In this paper, two essential and simple methods are provided to detect a broad range of Rho GTPase prenylation and GTP binding activities. Details of the technical procedures that have been used are explained step by step in this manuscript.

Here we describe a protocol to investigate the prenylation and guanosine-5'-triphosphate (GTP)-loading of Rho GTPase. This protocol consists of two detailed methods, namely membrane fractionation and a GTPase-linked immunosorbent assay. The protocol can be used for measuring the prenylation and GTP loading of different other small GTPases.

The Rho GTPase family belongs to the Ras superfamily and includes approximately 20 members in humans. Rho GTPases are important in the regulation of ...

Rapid Fluorescence-based Characterization of Single Extracellular Vesicles in Human Blood with Nanoparticle-tracking Analysis

Extracellular vesicles (EVs), including exosomes, are specialized membranous nano-sized vesicles found in bodily fluids that are constitutively released from many cell types and play a pivotal role in regulating cell-cell communication and a diverse range of biological processes. Many different methods for the characterization of EVs have been described. However, most of these methods have the disadvantage that the preparation and characterization of the samples are very time-consuming, or it is extremely difficult to analyze specific markers of interest due to their small size and due to the lack of discrete populations. While methods for analysis of EVs have been considerably improved over the last decade, there is still no standardized method for characterization of single EVs. Here, we demonstrate a semi-automated method for characterization of single EVs by fluorescence-based nanoparticle-tracking analysis. The protocol that is presented addresses the common problem of many researchers in this field and provides the complete workflow for rapid isolation of EVs and characterization with PKH67, a general cell membrane linker, as well as with specific surface markers such as CD63, CD9, vimentin, and lysosomal-associated membrane protein 1 (LAMP-1). The presented results show a high level of reproducibility, as confirmed by other methods, such as Western blotting. In the conducted experiments, we exclusively used EVs isolated from human serum samples, but this method is also suitable for plasma or other body fluids and can be adjusted for characterization of EVs from cell culture supernatants. Irrespective of the future progress of research on EV biology, the protocol that is presented here provides a rapid and reliable method for rapid characterization of single EVs with specific markers.

In this protocol, we describe the complete workflow for rapid isolation of extracellular vesicles from human whole blood and characterization of specific markers by fluorescence-based nanoparticle-tracking analysis. The presented results show a high level of reproducibility and can be adjusted to cell culture supernatants.

Extracellular vesicles (EVs), including exosomes, are specialized membranous nano-sized vesicles found in bodily fluids that are constitutively released ...

Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ubiquitinated proteins, peptides with a diglycine remnant conjugated to the epsilon amino group of lysine (&#39;K-&#949;-diglycine&#39; or simply &#39;diGly&#39;) can be used to track back the original modification site. Efficient immunopurification of diGly peptides combined with sensitive detection by mass spectrometry has resulted in a huge increase in the number of ubiquitination sites identified up to date. We have made several improvements to this workflow, including offline high pH reverse-phase fractionation of peptides prior to the enrichment procedure, and the inclusion of more advanced peptide fragmentation settings in the ion routing multipole. Also, more efficient cleanup of the sample using a filter-based plug in order to retain the antibody beads results in a greater specificity for diGly peptides. These improvements result in the routine detection of more than 23,000 diGly peptides from human cervical cancer cells (HeLa) cell lysates upon proteasome inhibition in the cell. We show the efficacy of this strategy for in-depth analysis of the ubiquitinome profiles of several different cell types and of in vivo samples, such as brain tissue. This study presents an original addition to the toolbox for protein ubiquitination analysis to uncover the deep cellular ubiquitinome.

We present a method for the purification, detection, and identification of diGly peptides that originate from ubiquitinated proteins from complex biological samples. The presented method is reproducible, robust, and outperforms published methods with respect to the level of depth of the ubiquitinome analysis.

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ...

Study on the Metabolism of Six Systemic Insecticides in a Newly Established Cell Suspension Culture Derived from Tea (Camellia Sinensis L.) Leaves

A platform for studying insecticide metabolism using in vitro tissues of tea plant was developed. Leaves from sterile tea plantlets were induced to form loose callus on Murashige and Skoog (MS) basal media with the plant hormones 2,4-dichlorophenoxyacetic acid (2,4-D, 1.0 mg L-1) and kinetin (KT, 0.1 mg L-1). Callus formed after 3 or 4 rounds of subculturing, each lasting 28 days. Loose callus (about 3 g) was then inoculated into B5 liquid media containing the same plant hormones and was cultured in a shaking incubator (120 rpm) in the dark at 25 &#177; 1 &#176;C. After 3&#8722;4 subcultures, a cell suspension derived from tea leaf was established at a subculture ratio ranging between 1:1 and 1:2 (suspension mother liquid: fresh medium). Using this platform, six insecticides (5 &#181;g mL-1 each thiamethoxam, imidacloprid, acetamiprid, imidaclothiz, dimethoate, and omethoate) were added into the tea leaf-derived cell suspension culture. The metabolism of the insecticides was tracked using liquid chromatography and gas chromatography. To validate the usefulness of the tea cell suspension culture, the metabolites of thiamethoxan and dimethoate present in treated cell cultures and intact plants were compared using mass spectrometry. In treated tea cell cultures, seven metabolites of thiamethoxan and two metabolites of dimethoate were found, while in treated intact plants, only two metabolites of thiamethoxam and one of dimethoate were found. The use of a cell suspension simplified the metabolic analysis compared to the use of intact tea plants, especially for a difficult matrix such as tea.

Study on the Metabolism of Six Systemic Insecticides in a Newly Established Cell Suspension Culture Derived from Tea Camellia Sinensis L. Leaves

This work presents a protocol for establishing a cell suspension culture derived from tea (Camellia sinensis L.) leaves that can be used to study the metabolism of external compounds that can be taken up by the whole plant, such as insecticides.

A platform for studying insecticide metabolism using in vitro tissues of tea plant was developed. Leaves from sterile tea plantlets were induced to form ...

Extremely Rapid and Specific Metabolic Labelling of RNA In Vivo with 4-Thiouracil (Ers4tU)

The nucleotide analogue, 4-thiouracil (4tU), is readily taken up by cells and incorporated into RNA as it is transcribed in vivo, allowing isolation of the RNA produced during a brief period of labelling. This is done by attaching a biotin moiety to the incorporated thio group and affinity purifying, using streptavidin coated beads. Achieving a good yield of pure, newly synthesized RNA that is free of pre-existing RNA makes shorter labelling times possible and permits increased temporal resolution in kinetic studies. This is a protocol for very specific, high yield purification of newly synthesized RNA. The protocol presented here describes how RNA is extracted from the yeast Saccharomyces cerevisiae. However, the protocol for purification of thiolated RNA from total RNA should be effective using RNA from any organism once it has been extracted from the cells. The purified RNA is suitable for analysis by many widely used techniques, such as reverse transcriptase-qPCR, RNA-seq and SLAM-seq. The specificity, sensitivity and flexibility of this technique allow unparalleled insights into RNA metabolism.

Extremely Rapid and Specific Metabolic Labelling of RNA In Vivo with 4-Thiouracil Ers4tU

The use of thiolated uracil to sensitively and specifically purify newly transcribed RNA from the yeast Saccharomyces cerevisiae.

The nucleotide analogue, 4-thiouracil (4tU), is readily taken up by cells and incorporated into RNA as it is transcribed in vivo, allowing isolation of ...