Name: spatiotemporally controlled nuclear translocation of guests in living cells using caged molecular glues as photoactivatable tags
Uploaded: 2019-01-17T13:00:00
Description: Watch this Scientific Journal Video about Spatiotemporally Controlled Nuclear Translocation of Guests in Living Cells Using Caged Molecular Glues as Photoactivatable Tags at JoVE.com

We acknowledge the Center for NanoBio Integration, the University of Tokyo. This work was supported by Grant-in-Aid for Young Scientists (B) (26810046) to K.O. and partially supported by Grant-in-Aid for Specially Promoted Research (25000005) to T.A. R.M. thanks the Research Fellowships of Japan Society for the Promotion of Science (JSPS) for Young Scientists and the Program for Leading Graduate Schools (GPLLI).

1. Preparation of Guests with CagedGlue-R Tags
<ol>
	<li>Prepare CagedGlue-NBD solution.
	<ol>
		<li>Synthesize CagedGlue-NBD (Figure 1) following the procedures previously described20.</li>
		<li>Prepare a stock solution of CagedGlue-NBD (10 mM) in dry dimethyl sulfoxide (DMSO). 
		Note: Store the stock solution in dark. The solution can be diluted with aqueous buffers or cell culture media upon usage.</li>
	</ol>
	<...

<ol>
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Previous investigations of light-triggered translocation of proteins into the cell nucleus have been achieved using caged NLS7,8,9. As mentioned earlier, these methods require additional techniques to incorporate the NLS-tagged proteins into the cytoplasm. In contrast, our CagedGlue-R tag enables not only photo-induced nuclear translocation but also cellular uptake of the guests. This feature of the CagedGl...

The cell nucleus, which carries genetic information, is one of the most important organelles as a subcellular drug-delivery target, since modulation of gene replication and expression is effective for treating various diseases including cancer and genetic disorders1,2,3. For nuclear delivery of drugs, conjugation of peptide tags such as nuclear localization signals (NLS)4,5,6 has been widely investigated. However, in order to reduce undesired side effects, spatiotemporal control of the nuclear translocation is necessary.
Previously, light-triggered translocation of proteins into the cell nucleus has been achieved using caged NLS7,8,9. NLS migrates into the cell nucleus by binding to cytoplasmic transport proteins6. In the reported methods, guest proteins bearing caged NLS are directly incorporated into the cytoplasm by microinjection8 or expressed in the target cells using a genetic code expansion technique9. Therefore, a method that can achieve both cellular uptake and photo-induced nuclear translocation is advantageous for practical applications.
Herein, we describe light-triggered nuclear translocation of guests in living cells using dendritic caged molecular glue (CagedGlue-R, Figure 1) tags. Water-soluble molecular glues10,11,12,13,14,15,16,17,18,19,20,21,22,23 bearing multiple Gu+ pendants have been previously developed, which tightly adhere to proteins11,12,13,14,15,16,17, nucleic acids18,19,20, phospholipid membranes21, and clay nanosheets22,23 through the formation of multiple salt bridges between their Gu+ pendants and oxyanionic groups on the targets. The Gu+ pendants of CagedGlue-R are protected by an anionic photocleavable group, butyrate-substituted nitroveratryloxycarbonyl (BANVOC). Guests tagged with CagedGlue-R are taken up into living cells via endocytosis and stay in endosomes (Figure 2). Upon photoirradiation, the BANVOC groups of CagedGlue-R are detached to yield an uncaged molecular glue (UncagedGlue-R) carrying multiple Gu+ pendants, which then facilitates the migration of the tagged guest into the cytoplasm followed by the cell nucleus (Figure 2). The CagedGlue-R tag can be uncaged by exposure to UV or two-photon near-infrared (NIR) light without serious phototoxicity. We demonstrate the spatiotemporally controlled nuclear delivery of macromolecular guests as well as small-molecule guests with CagedGlue-R tags, using quantum dots (QDs) and a fluorescent dye (nitrobenzoxadiazole; NBD), respectively, as examples.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58631/58631fig1.jpg" /> 
Figure 1: Schematic structures of CagedGlue-R. The 9 guanidinium ion (Gu+) pendants of CagedGlue-R are protected by a butyrate-substituted nitroveratryloxycarbonyl (BANVOC) group. The BANVOC groups are cleaved by irradiation with UV or two-photon NIR light. The focal core of CagedGlue-R is functionalized with either nitrobenzoxadiazole (NBD) or dibenzocylooctyne (DBCO). Reprinted with permission from reference20. <a href="https://www.jove.com/files/ftp_upload/58631/58631fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58631/58631fig2.jpg" /> 
Figure 2: Schematic illustration of light-triggered nuclear translocation of guests conjugated with a CagedGlue-R tag. The guest/CagedGlue-R conjugate is taken up into living cells via endocytosis. Upon photoirradiation, the CagedGlue-R tag is uncaged to yield an UncagedGlue-R tag, which can facilitate endosomal escape of the tagged guest. Subsequently, the tagged guest migrates into the cell nucleus. Reprinted with permission from reference20. <a href="https://www.jove.com/files/ftp_upload/58631/58631fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table>
	<tbody>
		<tr>
			<td>Azide-PEG4-NHS ester</td>
			<td>Click Chemistry Tools</td>
			<td>AZ103</td>
			<td></td>
		</tr>
		<tr>
			<td>Q-dot 655 ITK</td>
			<td>Invitrogen</td>
			<td>Q21521MP</td>
			<td></td>
		</tr>
		<tr>
			<td>Regenerated cellulose membrane (MWCO 3,500)</td>
			<td>NIPPON Genetics</td>
			<td>TOR-3K</td>
			<td></td>
		</tr>
		<tr>
			<td>Regenerated cellulose membrane (MWCO 25,000)</td>
			<td>Harvard Apparatus</td>
			<td>7425-RC25K</td>
			<td></td>
		</tr>
		<tr>
			<td>Hep3B Cells</td>
			<td>ATCC</td>
			<td>HB-8064</td>
			<td></td>
		</tr>
		<tr>
			<td>8-chambered glass substrate</td>
			<td>Nunc</td>
			<td>155411JP</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well culture plate</td>
			<td>Nunc</td>
			<td>167008</td>
			<td></td>
		</tr>
		<tr>
			<td>Eagle&#39;s minimal essential medium (EMEM)</td>
			<td>Thermo Fisher Scientific</td>
			<td>10370-021</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>GE Healthcare</td>
			<td>SH30406.02</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate buffer saline (D-PBS)</td>
			<td>Wako Pure Chemical Industries</td>
			<td>045-29795</td>
			<td></td>
		</tr>
		<tr>
			<td>LysoTracker Red</td>
			<td>Lonza Walkersville</td>
			<td>PA-3015</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst 33342</td>
			<td>Dojindo</td>
			<td>H342</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Counting Kit-8</td>
			<td>Dojindo</td>
			<td>CK04</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal laser scanning microscope</td>
			<td>Carl-Zeiss</td>
			<td>LSM 510</td>
			<td>Equipped with two-photon excitation laser (Mai Tai laser, Spectra-Physics)</td>
		</tr>
		<tr>
			<td>Confocal laser scanning microscope</td>
			<td>Leica</td>
			<td>TCS SP8</td>
			<td></td>
		</tr>
		<tr>
			<td>Xenon light source</td>
			<td>Asahi Spectra</td>
			<td>LAX-102</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax Paradigm</td>
			<td></td>
		</tr>
	</tbody>
</table>

spatiotemporally controlled nuclear translocation of guests in living cells using caged molecular glues as photoactivatable tags

The cell nucleus is one of the most important organelles as a subcellular drug-delivery target, since modulation of gene replication and expression is effective for treating various diseases. Here, we demonstrate light-triggered nuclear translocation of guests using caged molecular glue (CagedGlue-R) tags, whose multiple guanidinium ion (Gu+) pendants are protected by an anionic photocleavable group (butyrate-substituted nitroveratryloxycarbonyl; BANVOC). Guests tagged with CagedGlue-R are taken up into living cells via endocytosis and remain in endosomes. However, upon photoirradiation, CagedGlue-R is converted into uncaged molecular glue (UncagedGlue-R) carrying multiple Gu+ pendants, which facilitates the endosomal escape and subsequent nuclear translocation of the guests. This method is promising for site-selective nuclear-targeting drug delivery, since the tagged guests can migrate into the cytoplasm followed by the cell nucleus only when photoirradiated. CagedGlue-R tags can deliver macromolecular guests such as quantum dots (QDs) as well as small-molecule guests. CagedGlue-R tags can be uncaged with not only UV light but also two-photon near-infrared (NIR) light, which can deeply penetrate into tissue.

Before photoirradiation, Hep3B cells incubated with CagedGlue-NBD exhibited punctate fluorescence emission from their interior (&#955;ext = 488 nm; Figures 4A and 4C, green). An analogous micrograph was obtained upon excitation at 543 nm for red-fluorescent dye (Figures&#160;4B and 4C, red), indicating that CagedGlue-NBD localized in the endosomes. Accordingly, th...

Watch this Scientific Journal Video about Spatiotemporally Controlled Nuclear Translocation of Guests in Living Cells Using Caged Molecular Glues as Photoactivatable Tags at JoVE.com

Spatiotemporally Controlled Nuclear Translocation of Guests in Living Cells Using Caged Molecular Glues as Photoactivatable Tags

This protocol describes light-triggered nuclear translocation of guests in living cells using caged molecular glue tags. This method is promising for site-selective nuclear-targeting drug delivery.

The cell nucleus is one of the most important organelles as a subcellular drug-delivery target, since modulation of gene replication and expression is ...

This method can help answer key question in the area of drug delivery, such as how to deliver a drug to a specific cellular-granular. The main advantage of this technique is that nuclear translocation of gas can be induced by light. Demonstrating the procedure will be Rina Mogaki and Akio Arisaka the grad students from my group.To begin prepare the quantum dot linked cage molecular glue by synthesizing caged molecular glue linked dibenzocyclooctyne as described in more detail elsewhere. Prepare a 10 millimolar stock solution of the caged molecular glue linked dibenzocyclooctyne in dry DMSO. Then prepare the quantum dot linked caged molecular glue by first making aseye functionalized quantum dots.To accomplish this add 100 microliters of 125 micromolar aseye PEG4 NHS ester in DMF to 400 microliters of a DMF solution containing 500 nanomolar of quantum dots that are coated with amine functionalized peg. Stir the mixture for one hour at room temperature. Place the resulting solution in a regenerated cellulose membrane and dialyze it for 24 hours against 800 ml of DMF.Next dilute the stock solution of caged molecular glue linked dibenzocyclooctyne to 50 micromolar with DMF and add 200 microliters of it to the post dialysis solution. Stir the mixture for three hours at room temperature. Then dialyze the resulting mixture for 24 hours against 800 ml of fresh DMF using a regenerated cellulose membrane with the molecular weight cut off of 25000.After 24 hours dilute the resulting solution to 200 nanomolar with DMF. Maintain human hepatocellular carcinoma HEP3 B-cells in Eagle's minimal essential medium containing 10%FBS under standard culture conditions. One day before the experiment seed 5000 HEP3 B-cells in 200 microliters of culture medium into each well of a 8 chambered glass slide.Then cover the slide and place it into an incubator for 24 hours. The next day remove the culture medium and rinse the cells twice with 100 microliters of pre-warmed PBS. To each well of the 8 chambered slide add 200 microliters of FBS free medium containing 10 micromolar of a fluorescently dyed caged molecular glue.After incubating for 3 hours remove the culture medium and rinse the cell sample twice with 100 microliters of PBS. To visualize the endosomes add 200 microliters of culture media containing 100 nanomolar of an additional red fluorescent dye such as LysoTracker Red. Incubate the resulting cell sample for 20 minutes.Then remove the culture medium and rinse the cell sample twice with 100 microliters of PBS. Afterwards return the cells to 200 microliters of the culture medium. To induce nuclear translocation of the fluorescently dyed caged molecular glue place the cells under a 100 watt xenon light source equipped with a 365 nanometer bandpass filter.Expose the cells to UV light for 2 minutes. During this time keep the control cell sample without UV exposure in the dark. The lid of the glass substrates can be taken off for efficient UV exposure however take caution as prolonged exposure to UV light may cause cell death.To visualize the nuclei add one microliter of Hoeschst stain to the culture medium. Incubate the resulting cell sample for 10 minutes. Then place the sample on the stage of a confocal laser scanning microscope.Record the micrographs for the fluorescently dyed caged molecular glue, the LysoTracker Red, and the nuclear stain. As previously shown, seed 5000 human hepatocellular carcinoma HEP3 B-cells into each well of an 8 well chamber slide and culture under standard conditions for 24 hours. Supply the cell samples with 200 microliters of FBS free culture medium containing the fluorescently dyed caged molecular glue.Incubate the resulting cell sample for 3 hours. Then remove the culture medium and rinse the cell sample twice with 100 microliters of PBS. Return the cells to 200 microliters of culture medium.Then subject to sample confocal laser scanning microscopy and record the micrographs as described in the accompanying text protocol. As previously shown seed 5000 human hepatocellular carcinoma HEP3 B-cells into each well of an 8 well chamber slide and culture under standard conditions for 24 hours. Supply the cell samples with 200 microliters of FBS free culture medium containing 10 nanomolar of the quantum dot linked caged molecular glue.Incubate the resulting cell sample for 3 hours. Then remove the medium and rinse the cell sample twice with 100 microliters of PBS. After rinsing the cells return them to 200 microliters of culture medium.Then place the plate under a 100 watt xenon light source equipped with a 365 nanometer bandpass filter. Expose the cell sample to UV light for 2 minutes keeping the control samples in the dark. To visualize the nuclei add 1 microliter of Hoechst stain to the culture medium.Incubate the resulting cell sample for 10 minutes. Then image the cells using a confocal laser scanning microscope. Seed the human hepatocellular carcinoma HEP3 B-cells the day before the experiment at 5000 cells per well into a 96 well culture plate.Then cover the cells with 200 microliters of culture media and then place the plate in an incubator for 24 hours. The next day remove the culture medium and rinse the cell sample twice with 100 microliters of PBS. Then add 200 microliters of FBS free culture medium containing the fluorescently dyed caged molecular glue at concentrations ranging from 0.1 to 100 micromolar.Incubate the plate for 3 hours and then place a plate under the UV light source. Expose the cell sample to UV light for 2 minutes keeping the control samples in the dark. Following UV exposure at 10 microliters of the Cell Counting Kit-8 reagent to the culture medium and incubate the resulting cell sample for 2 hours.Then read the absorption of the samples at 450 nanometers using a microplate reader. Before photo radiation HEP3 B-cells incubated with fluorescently dyed caged molecular glue exhibits punctate fluorescence emission from the interior an analogous micrograph showing the LysoTracker Red indicates that fluorescently dyed caged molecular glue was localized in the endosomes. Accordingly the fluorescence emission assignable to the fluorescently dyed caged molecular glue was observed outside the cell nucleus prior to UV radiation.After UV radiation the fluorescent suggests that fluorescently dyed caged molecular glue was uncaged and migrated into the cytoplasm and the cell nucleus. Such nuclear translation of the fluorescently dyed caged molecular glue can be induced site selectively by 2-photon near infrared light. The fluorescently dyed caged molecular glue in non irradiated areas did not escape from the endosomes and remained as punctate fluorescence.The dendritic caged molecular glue tags can also deliver macromolecular guests such as quantum dots into the cell nucleus. These conjugates can be taken up into the cells and after UV exposure for 2 minutes the fluorescence emission of the quantum dots can be seen within the nucleus. After this development this technique paved the way for researchers in the field of gene therapy to explore low side effect treatment.

spatiotemporally-controlled-nuclear-translocation-guests-living-cells

Research

JoVE Journal

Chemistry

Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of &#946;-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal &#946;-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (&#8804;1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired.

An efficient, three-step synthesis of RAFT-based fluorescent glycopolymers, consisting of glycomonomer preparation, copolymerization, and post-modification, is demonstrated. This protocol can be used to prepare RAFT-based statistical glycopolymers with desired structures.

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and ...

Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation

Phosphoinositides (PtdInsPs) are essential signaling lipids responsible for recruiting specific effectors and conferring organelles with molecular identity and function. Each of the seven PtdInsPs varies in their distribution and abundance, which are tightly regulated by specific kinases and phosphatases. The abundance of PtdInsPs can change abruptly in response to various signaling events or disturbance of the regulatory machinery. To understand how these events lead to changes in the amount of PtdInsPs and their resulting impact, it is important to quantify PtdInsP levels before and after a signaling event or between control and abnormal conditions. However, due to their low abundance and similarity, quantifying the relative amounts of each PtdInsP can be challenging. This article describes a method for quantifying PtdInsP levels by metabolically labeling cells with 3H-myo-inositol, which is incorporated into PtdInsPs. Phospholipids are then precipitated and deacylated. The resulting soluble 3H-glycero-inositides are further extracted, separated by high-performance liquid chromatography (HPLC), and detected by flow scintillation. The labeling and processing of yeast samples is described in detail, as well as the instrumental setup for the HPLC and flow scintillator. Despite losing structural information regarding acyl chain content, this method is sensitive and can be optimized to concurrently quantify all seven PtdInsPs in cells.

Phosphoinositides are signaling lipids whose relative abundance rapidly changes in response to various stimuli. This article describes a method to measure the abundance of phosphoinositides by metabolically labeling cells with 3H-myo-inositol, followed by extraction and deacylation. Extracted glycero-inositides are then separated by high-performance liquid chromatography and quantified by flow scintillation.

Phosphoinositides (PtdInsPs) are essential signaling lipids responsible for recruiting specific effectors and conferring organelles with molecular ...

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical (Methylation) and Physical (Mass Spectrometry, Nuclear Magnetic Resonance) Techniques

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans. De-starched wheat endosperm cell walls were isolated as an alcohol-insoluble residue (AIR)1 and sequentially extracted with water (W-sol Fr) and 1 M KOH containing 1% NaBH4 (KOH-sol Fr) as described by Ratnayake et al. (2014)2. Two different approaches (see summary in Figure 1) are adopted. In the first, intact W-sol AXs are treated with 2AB to tag the original RE backbone chain sugar residue and then treated with an endoxylanase to generate a mixture of 2AB-labelled RE and internal region reducing oligosaccharides, respectively. In a second approach, the KOH-sol Fr is hydrolyzed with endoxylanase to first generate a mixture of oligosaccharides which are subsequently labelled with 2AB. The enzymically released ((un)tagged) oligosaccharides from both W- and KOH-sol Frs are then methylated and the detailed structural analysis of both the native and methylated oligosaccharides is performed using a combination of MALDI-TOF-MS, RP-HPLC-ESI-QTOF-MS and ESI-MSn. Endoxylanase digested KOH-sol AXs are also characterized by nuclear magnetic resonance (NMR) that also provides information on the anomeric configuration. These techniques can be applied to other classes of polysaccharides using the appropriate endo-hydrolases.

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical Methylation and Physical Mass Spectrometry, Nuclear Magnetic Resonance Techniques

This protocol describes the specific techniques used for the structural characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans by tagging the RE with 2 aminobenzamide prior to enzymatic (endoxylanase) hydrolysis and then analysis of the resultant oligosaccharides using mass spectrometry (MS) and nuclear magnetic resonance (NMR).

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of ...

Investigations on the Ga(III) Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue

We demonstrate a method for the isolation of EOB-DTPA (3,6,9-triaza-3,6,9-tris(carboxymethyl)-4-(ethoxybenzyl)-undecanedioic acid) from its Gd(III) complex and protocols for the preparation of its novel non-radioactive, i.e., natural Ga(III) as well as radioactive 68Ga complex. The ligand as well as the Ga(III) complex were characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry and elemental analysis. 68Ga was obtained by a standard elution method from a 68Ge/68Ga generator. Experiments to evaluate the 68Ga-labeling efficiency of EOB-DTPA at pH 3.8&#8211;4.0 were performed. Established analysis techniques radio TLC (thin layer chromatography) and radio HPLC (high performance liquid chromatography) were used to determine the radiochemical purity of the tracer. As a first investigation of the 68Ga tracers&#39; lipophilicity the n-octanol/water distribution coefficient of 68Ga species present in a pH 7.4 solution was determined by an extraction method. In vitro stability measurements of the tracer in various media at physiological pH were performed, revealing different rates of decomposition.

Investigations on the GaIII Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue

A procedure for the isolation of EOB-DTPA and subsequent complexation with natural Ga(III) and 68Ga is presented herein, as well as a thorough analysis of all compounds and investigations on labeling efficiency, in vitro stability and the n-octanol/water distribution coefficient of the radiolabeled complex.

We demonstrate a method for the isolation of EOB-DTPA (3,6,9-triaza-3,6,9-tris(carboxymethyl)-4-(ethoxybenzyl)-undecanedioic acid) from its Gd(III) ...

Characterizing Electron Transport through Living Biofilms

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980&#39;s to investigate thin film conductive polymers.

A protocol for measuring electrical conductivity of living microbial biofilms under physiologically relevant conditions is presented.

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under ...

Laser-heating and Radiance Spectrometry for the Study of Nuclear Materials in Conditions Simulating a Nuclear Power Plant Accident

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and Fukushima (Japan, 2011). Research on the causes, dynamics, and consequences of these mishaps has been performed in a few laboratories worldwide in the last three decades. Common goals of such research activities are: the prevention of these kinds of accidents, both in existing and potential new nuclear power plants; the minimization of their eventual consequences; and ultimately, a full understanding of the real risks connected with NPPs. At the European Commission Joint Research Centre&#39;s Institute for Transuranium Elements, a laser-heating and fast radiance spectro-pyrometry facility is used for the laboratory simulation, on a small scale, of NPP core meltdown, the most common type of severe accident (SA) that can occur in a nuclear reactor as a consequence of a failure of the cooling system. This simulation tool permits fast and effective high-temperature measurements on real nuclear materials, such as plutonium and minor actinide-containing fission fuel samples. In this respect, and in its capability to produce large amount of data concerning materials under extreme conditions, the current experimental approach is certainly unique. For current and future concepts of NPP, example results are presented on the melting behavior of some different types of nuclear fuels: uranium-plutonium oxides, carbides, and nitrides. Results on the high-temperature interaction of oxide fuels with containment materials are also briefly shown.

We present experiments in which real nuclear fuel, cladding, and containment materials are laser heated to temperatures beyond 3,000 K while their behavior is studied by radiance spectroscopy and thermal analysis. These experiments simulate, on a laboratory scale, the formation of a lava-phase following a nuclear reactor core meltdown.

Major and severe accidents have occurred three times in nuclear power plants (NPPs), at Three Mile Island (USA, 1979), Chernobyl (former USSR, 1986) and ...

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces are demonstrated. This work requires careful design, considerable synthetic effort, and proper analysis. The rotary motion of the molecular motor in solution is shown by 1H NMR and UV-vis absorption spectroscopy techniques. In addition, the method to graft the motor onto an amine-coated quartz is described. This method helps to gain more insight into molecular machines.

The manuscript describes how to synthesize and graft a molecular motor on surfaces for single molecular imaging.

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces ...