Name: chemical inactivation of the e3 ubiquitin ligase cereblon by pomalidomide-based homo-protacs
Uploaded: 2019-05-15T14:00:00
Description: Watch this Scientific Journal Video about Chemical Inactivation of the E3 Ubiquitin Ligase Cereblon by Pomalidomide-based Homo-PROTACs at JoVE.com

This work was supported by the Deutsche Forschungsgemeinschaft (Emmy-Noether Program Kr-3886/2-1 and SFB-1074 to J.K.; FOR2372 to M.G.)

1. Preparation of PROTAC molecules
CAUTION: Please consult all relevant material safety data sheets (MSDS) before use. Several of the chemicals used in these syntheses are toxic and carcinogenic. Please use all appropriate safety practices and personal protective equipment.
<ol>
	<li>Preparation of tert-butyl N-(2,6-dioxo-3-piperidyl)carbamate (compound 1)
	<ol>
		<li>Add 1,1&#39;-carbonyldiimidazole (1.95 g, 12 mmol) and a catalytic amount of 4-(dimethylam...

<ol>
	<li>Ito, T., 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=Identification+of+a+primary+target+of+thalidomide+teratogenicity.">Identification of a primary target of thalidomide teratogenicity.</a> Science. 327 (5971), 1345-1350 (2010).</li><li>Lopez-Girona, A., 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=Cereblon+is+a+direct+protein+target+for+immunomodulatory+and+antiproliferative+activities+of+lenalidomide+and+pomalidomide.">Cereblon is a direct protein target for immunomodulatory and antiproliferative activities of lenalidomide and pomalidomide.</a> Leukemia. 26 (11), 2326-2335 (2012).</li><li>Fischer, E. S., 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+DDB1-CRBN+E3+ubiquitin+ligase+in+complex+with+thalidomide.">Structure of the DDB1-CRBN E3 ubiquitin ligase in complex with thalidomide.</a> Nature. 512 (7512), 49-53 (2014).</li><li>Gandhi, A. K., 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=Immunomodulatory+agents+lenalidomide+and+pomalidomide+co-stimulate+T+cells+by+inducing+degradation+of+T+cell+repressors+Ikaros+and+Aiolos+via+modulation+of+the+E3+ubiquitin+ligase+complex+CRL4(CRBN).">Immunomodulatory agents lenalidomide and pomalidomide co-stimulate T cells by inducing degradation of T cell repressors Ikaros and Aiolos via modulation of the E3 ubiquitin ligase complex CRL4(CRBN).</a> British Journal of Haematology. 164 (6), 811-821 (2014).</li><li>Kronke, J., Hurst, S. N., Ebert, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lenalidomide+induces+degradation+of+IKZF1+and+IKZF3.">Lenalidomide induces degradation of IKZF1 and IKZF3.</a> Oncoimmunology. 3 (7), e941742 (2014).</li><li>Lu, G., 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+myeloma+drug+lenalidomide+promotes+the+cereblon-dependent+destruction+of+Ikaros+proteins.">The myeloma drug lenalidomide promotes the cereblon-dependent destruction of Ikaros proteins.</a> Science. 343 (6168), 305-309 (2014).</li><li>Zhu, Y. X., Kortuem, K. M., Stewart, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanism+of+action+of+immune-modulatory+drugs+thalidomide,+lenalidomide+and+pomalidomide+in+multiple+myeloma.">Molecular mechanism of action of immune-modulatory drugs thalidomide, lenalidomide and pomalidomide in multiple myeloma.</a> Leukemia &amp; Lymphona. 54 (4), 683-687 (2013).</li><li>Chamberlain, P. P., 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+human+Cereblon-DDB1-lenalidomide+complex+reveals+basis+for+responsiveness+to+thalidomide+analogs.">Structure of the human Cereblon-DDB1-lenalidomide complex reveals basis for responsiveness to thalidomide analogs.</a> Nature Structural &amp; Molecular Biology. 21 (9), 803-809 (2014).</li><li>Donovan, K. A., 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=Thalidomide+promotes+degradation+of+SALL4,+a+transcription+factor+implicated+in+Duane+Radial+Ray+syndrome.">Thalidomide promotes degradation of SALL4, a transcription factor implicated in Duane Radial Ray syndrome.</a> eLife. 7, (2018).</li><li>Matyskiela, M. E., 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=SALL4+mediates+teratogenicity+as+a+thalidomide-dependent+cereblon+substrate.">SALL4 mediates teratogenicity as a thalidomide-dependent cereblon substrate.</a> Nature Chemical Biology. 14 (10), 981-987 (2018).</li><li>Kronke, 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=Lenalidomide+induces+ubiquitination+and+degradation+of+CK1alpha+in+del(5q)+MDS.">Lenalidomide induces ubiquitination and degradation of CK1alpha in del(5q) MDS.</a> Nature. 523 (7559), 183-188 (2015).</li><li>Sakamoto, K. 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=Protacs:+chimeric+molecules+that+target+proteins+to+the+Skp1-Cullin-F+box+complex+for+ubiquitination+and+degradation.">Protacs: chimeric molecules that target proteins to the Skp1-Cullin-F box complex for ubiquitination and degradation.</a> Proceedings of the National Academy of Sciences of the United States of America. 98 (15), 8554-8559 (2001).</li><li>Sakamoto, K. 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=Development+of+Protacs+to+target+cancer-promoting+proteins+for+ubiquitination+and+degradation.">Development of Protacs to target cancer-promoting proteins for ubiquitination and degradation.</a> Molecular &amp; Cellular Proteomics. 2 (12), 1350-1358 (2003).</li><li>Schneekloth, J. S., 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=Chemical+genetic+control+of+protein+levels:+selective+in+vivo+targeted+degradation.">Chemical genetic control of protein levels: selective in vivo targeted degradation.</a> Journal of the American Chemical Society. 126 (12), 3748-3754 (2004).</li><li>Gu, S., Cui, D., Chen, X., Xiong, X., Zhao, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PROTACs:+An+Emerging+Targeting+Technique+for+Protein+Degradation+in+Drug+Discovery.">PROTACs: An Emerging Targeting Technique for Protein Degradation in Drug Discovery.</a> Bioessays. 40 (4), e1700247 (2018).</li><li>Collins, I., Wang, H., Caldwell, J. J., Chopra, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+approaches+to+targeted+protein+degradation+through+modulation+of+the+ubiquitin-proteasome+pathway.">Chemical approaches to targeted protein degradation through modulation of the ubiquitin-proteasome pathway.</a> Biochemical Journal. 474 (7), 1127-1147 (2017).</li><li>Neklesa, T. K., Winkler, J. D., Crews, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+protein+degradation+by+PROTACs.">Targeted protein degradation by PROTACs.</a> Pharmacology &amp; Therapeutics. 174, 138-144 (2017).</li><li>Winter, G. E., 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=Phthalimide+conjugation+as+a+strategy+for+in+vivo+target+protein+degradation.">Phthalimide conjugation as a strategy for in vivo target protein degradation.</a> Science. 348 (6241), 1376-1381 (2015).</li><li>Maniaci, 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=Homo-PROTACs:+bivalent+small-molecule+dimerizers+of+the+VHL+E3+ubiquitin+ligase+to+induce+self-degradation.">Homo-PROTACs: bivalent small-molecule dimerizers of the VHL E3 ubiquitin ligase to induce self-degradation.</a> Nature Communications. 8 (1), 830 (2017).</li><li>Crew, A. P., 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=Identification+and+Characterization+of+Von+Hippel-Lindau-Recruiting+Proteolysis+Targeting+Chimeras+(PROTACs)+of+TANK-Binding+Kinase+1.">Identification and Characterization of Von Hippel-Lindau-Recruiting Proteolysis Targeting Chimeras (PROTACs) of TANK-Binding Kinase 1.</a> Journal of Medicinal Chemistry. , (2017).</li><li>Lu, 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=Hijacking+the+E3+Ubiquitin+Ligase+Cereblon+to+Efficiently+Target+BRD4.">Hijacking the E3 Ubiquitin Ligase Cereblon to Efficiently Target BRD4.</a> Chemistry &amp; Biology. 22 (6), 755-763 (2015).</li><li>Steinebach, 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=PROTAC-mediated+crosstalk+between+E3+ligases.">PROTAC-mediated crosstalk between E3 ligases.</a> Chemical Communications. 55 (12), 1821-1824 (2019).</li><li>Tinworth, C. P., Lithgow, H., Churcher, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+molecule-mediated+protein+knockdown+as+a+new+approach+to+drug+discovery.">Small molecule-mediated protein knockdown as a new approach to drug discovery.</a> Medchemcomm. 7 (12), 2206-2216 (2016).</li><li>Steinebach, 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=Homo-PROTACs+for+the+Chemical+Knockdown+of+Cereblon.">Homo-PROTACs for the Chemical Knockdown of Cereblon.</a> ACS Chemical Biology. 13 (9), 2771-2782 (2018).</li><li>Ambrozak, A., 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=Synthesis+and+Antiangiogenic+Properties+of+Tetrafluorophthalimido+and+Tetrafluorobenzamido+Barbituric+Acids.">Synthesis and Antiangiogenic Properties of Tetrafluorophthalimido and Tetrafluorobenzamido Barbituric Acids.</a> ChemMedChem. 11 (23), 2621-2629 (2016).</li><li>Zhou, B., 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=Discovery+of+a+Small-Molecule+Degrader+of+Bromodomain+and+Extra-Terminal+(BET)+Proteins+with+Picomolar+Cellular+Potencies+and+Capable+of+Achieving+Tumor+Regression.">Discovery of a Small-Molecule Degrader of Bromodomain and Extra-Terminal (BET) Proteins with Picomolar Cellular Potencies and Capable of Achieving Tumor Regression.</a> Journal of Medicinal Chemistry. , (2017).</li><li>Zhang, 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=Proteolysis+Targeting+Chimeras+(PROTACs)+of+Anaplastic+Lymphoma+Kinase+(ALK).">Proteolysis Targeting Chimeras (PROTACs) of Anaplastic Lymphoma Kinase (ALK).</a> European Journal of Medicinal Chemistry. 151, 304-314 (2018).</li><li>Runcie, A. C., Chan, K. H., Zengerle, M., Ciulli, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+genetics+approaches+for+selective+intervention+in+epigenetics.">Chemical genetics approaches for selective intervention in epigenetics.</a> Current Opinion in Chemical Biology. 33, 186-194 (2016).</li><li>Kronke, 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=Lenalidomide+causes+selective+degradation+of+IKZF1+and+IKZF3+in+multiple+myeloma+cells.">Lenalidomide causes selective degradation of IKZF1 and IKZF3 in multiple myeloma cells.</a> Science. 343 (6168), 301-305 (2014).</li><li>Eichner, 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=Immunomodulatory+drugs+disrupt+the+cereblon-CD147-MCT1+axis+to+exert+antitumor+activity+and+teratogenicity.">Immunomodulatory drugs disrupt the cereblon-CD147-MCT1 axis to exert antitumor activity and teratogenicity.</a> Nature Medicine. 22 (7), 735-743 (2016).</li><li>Zhu, Y. 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=Cereblon+expression+is+required+for+the+antimyeloma+activity+of+lenalidomide+and+pomalidomide.">Cereblon expression is required for the antimyeloma activity of lenalidomide and pomalidomide.</a> Blood. 118 (18), 4771-4779 (2011).</li><li>Kortum, K. 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=Targeted+sequencing+of+refractory+myeloma+reveals+a+high+incidence+of+mutations+in+CRBN+and+Ras+pathway+genes.">Targeted sequencing of refractory myeloma reveals a high incidence of mutations in CRBN and Ras pathway genes.</a> Blood. 128 (9), 1226-1233 (2016).</li><li>Gil, 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=Cereblon+deficiency+confers+resistance+against+polymicrobial+sepsis+by+the+activation+of+AMP+activated+protein+kinase+and+heme-oxygenase-1.">Cereblon deficiency confers resistance against polymicrobial sepsis by the activation of AMP activated protein kinase and heme-oxygenase-1.</a> Biochemical and Biophysical Research Communications. 495 (1), 976-981 (2018).</li><li>Kim, H. K., 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=Cereblon+in+health+and+disease.">Cereblon in health and disease.</a> Pfl&#252;gers Archiv: European Journal of Physiology. 468 (8), 1299-1309 (2016).</li><li>Lee, K. 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=Disruption+of+the+cereblon+gene+enhances+hepatic+AMPK+activity+and+prevents+high-fat+diet-induced+obesity+and+insulin+resistance+in+mice.">Disruption of the cereblon gene enhances hepatic AMPK activity and prevents high-fat diet-induced obesity and insulin resistance in mice.</a> Diabetes. 62 (6), 1855-1864 (2013).</li></ol>

The design of such homo-PROTACs as described here for CRBN relies on the specific affinity of pomalidomide to CRBN, which has been successfully utilized in numerous heterobifunctional PROTACs and resulted in the development of PROTAC 8 as a highly selective CRBN degrader. The specificity of our molecule has already been confirmed by proteomic analyses24. For genetically mediated knockout, exclusion and validation of side effects is challenging and time consuming. In addition, a ch...

The immunomodulatory drugs (IMiDs) thalidomide and its analogs, lenalidomide and pomalidomide, all approved for the treatment of multiple myeloma, bind to the E3 ubiquitin ligase cereblon (CRBN), a substrate adaptor for cullin4A-RING E3 ubiquitin ligase (CRL4CRBN)1,2,3. Binding of IMiDs enhances the affinity of CRL4CRBN to the lymphoid transcription factors Ikaros (IKZF1) and Aiolos (IKZF3), leading to their ubiquitination and degradation (Figure 1)4,5,6,7,8. Since IKZF1 and IKZF3 are essential for multiple myeloma cells, their inactivation results in growth inhibition. SALL4 was recently found as an additional IMiD-induced neo-substrate of CRBN that is likely responsible for the teratogenicity and the so-called Contergan catastrophe in the 1950s caused by thalidomide9,10. In contrast, casein kinase 1&#945; (CK1&#945;) is a lenalidomide-specific substrate of CRBN that is implicated in the therapeutic effect in myelodysplastic syndrome with chromosome 5q deletions11.
The ability of small-molecules to target a specific protein for degradation is an exciting implication for modern drug development. While the mechanism of thalidomide and its analogs was discovered after their first use in humans, so called Proteolysis Targeting Chimeras (PROTACs) have been designed to specifically target a protein of interest (POI) (Figure 2)12,13,14,15,16,17,18. PROTACs are heterobifunctional molecules that consist of a specific ligand for the POI connected via a linker to a ligand of an E3 ubiquitin ligase like CRBN or von-Hippel-Lindau (VHL)18,19,20,21,22. PROTACs induce the formation of a transient ternary complex, directing the POI to the E3 ubiquitin ligase, resulting in its ubiquitination and proteasomal degradation. The major advantages of PROTACs over conventional inhibitors is that binding to a POI is sufficient rather than its inhibition and therefore PROTACs can potentially target a far wider spectrum of proteins including those that were considered to be undruggable like transcription factors15. In addition, chimeric molecules act catalytically and therefore have a high potency. After ubiquitin transfer to the POI, the ternary complex dissociates and is available for the formation of new complexes. Thus, very low PROTAC concentrations are sufficient for the degradation of the target protein23.
Here we describe the synthesis of a pomalidomide-pomalidomide conjugated homo-PROTAC (compound 8) that recruits CRBN for the degradation of itself24. The E3 ubiquitin ligase CRBN serves as both the recruiter and the target at the same time (Figure 3). To validate our data, we also synthesized a negative binding control (compound 9). Our data confirm that the newly synthesized homo-PROTAC is specific for CRBN degradation and has only minimal effects on other proteins.

<table>
	<tbody>
		<tr>
			<td>1,1&#39;-Carbonyldiimidazole</td>
			<td>TCI chemicals</td>
			<td>C0119</td>
			<td></td>
		</tr>
		<tr>
			<td>2,2&#8242;-(Ethylenedioxy)-bis(ethylamine)</td>
			<td>Sigma-Aldrich</td>
			<td>385506</td>
			<td>Compound 6</td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>Sigma-Aldrich</td>
			<td>M6250</td>
			<td></td>
		</tr>
		<tr>
			<td>3-Fluorophthalic anhydride, 98 %</td>
			<td>Alfa Aesar</td>
			<td>A12275</td>
			<td></td>
		</tr>
		<tr>
			<td>4-Dimethylaminopyridine, 99 %</td>
			<td>Acros</td>
			<td>148270250</td>
			<td>Toxic</td>
		</tr>
		<tr>
			<td>Acrylamidstamml&#246;sung/ Bisacrylamid (30%/0,8%)</td>
			<td>Carl Roth</td>
			<td>3029.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Aiolos (D1C1E) mAB</td>
			<td>Cell signaling</td>
			<td>15103S</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-CRBN antibody produced in rabbit</td>
			<td>Sigma</td>
			<td>HPA045910</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-rabbit IgG HRP-linked antibody</td>
			<td>Sigma</td>
			<td>7074S</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Persulfate</td>
			<td>Roth</td>
			<td>9592.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Boc-Gln-OH</td>
			<td>TCI chemicals</td>
			<td>B1649</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A7906-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>CellTiter-Glo Luminescent Cell Viability Assay</td>
			<td>Promega</td>
			<td>G7571</td>
			<td></td>
		</tr>
		<tr>
			<td>ChemiDoc XRS+</td>
			<td>Bio-Rad</td>
			<td>1708265</td>
			<td></td>
		</tr>
		<tr>
			<td>DMF, anhydrous, 99.8 %</td>
			<td>Acros</td>
			<td>348435000</td>
			<td>Extra Dry over Molecular Sieve</td>
		</tr>
		<tr>
			<td>DMSO, anhydrous, 99.7 %</td>
			<td>Acros</td>
			<td>348445000</td>
			<td>Extra Dry over Molecular Sieve</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma-Aldrich</td>
			<td>15523-1L-R</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse (HRP conjugated)</td>
			<td>Santa Cruz biotechnology</td>
			<td>sc-2005</td>
			<td></td>
		</tr>
		<tr>
			<td>Halt Protease &#38; Phosphatase Inhibitor Single-use Cocktail (100X)</td>
			<td>Thermo Scientific</td>
			<td>1861280</td>
			<td></td>
		</tr>
		<tr>
			<td>Ikaros (D6N9Y) Mab</td>
			<td>Cell signaling</td>
			<td>14859S</td>
			<td></td>
		</tr>
		<tr>
			<td>ImmobilonP Transfer Membrane (0,45&#181;m)</td>
			<td>Merck</td>
			<td>IPVH000010</td>
			<td></td>
		</tr>
		<tr>
			<td>Iodomethane, 99 %</td>
			<td>Sigma-Aldrich</td>
			<td>I8507</td>
			<td>Highly toxic</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma-Aldrich</td>
			<td>32213-2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Mg132</td>
			<td>Selleckchem</td>
			<td>S2619</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini Trans-Blot electrophoretic transfer cell</td>
			<td>Bio-Rad</td>
			<td>1703930</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini-PROTEAN Tetra Vertical Electrophoresis Cell</td>
			<td>Bio-Rad</td>
			<td>1658004</td>
			<td></td>
		</tr>
		<tr>
			<td>MLN4942</td>
			<td>biomol (cayman)</td>
			<td>Cay15217-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Monoclonal Anti-&#945;-Tubulin antibody produced in mouse (B512)</td>
			<td>Sigma</td>
			<td>T5168</td>
			<td></td>
		</tr>
		<tr>
			<td>N-Ethyldiisopropylamine, 99 %</td>
			<td>Alfa Aesar</td>
			<td>A11801</td>
			<td></td>
		</tr>
		<tr>
			<td>Nonfat dried milk powder</td>
			<td>PanReac AppliChem</td>
			<td>A0830,0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Nunc F96 MicroWell White Polystyrene Plate</td>
			<td>Thermo Scientific</td>
			<td>136101</td>
			<td></td>
		</tr>
		<tr>
			<td>NuPAGE LDS Sample Buffer (4X)</td>
			<td>Thermo Scientific</td>
			<td>NP0008</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce BCA Protein Assay kit</td>
			<td>Thermo Scientific</td>
			<td>23225</td>
			<td></td>
		</tr>
		<tr>
			<td>Pomalidomide</td>
			<td>Selleckchem</td>
			<td>S1567</td>
			<td></td>
		</tr>
		<tr>
			<td>RestoreTM Western Blot Stripping Buffer</td>
			<td>Thermo Scientific</td>
			<td>46430</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium dodecyl sulfate</td>
			<td>Carl Roth</td>
			<td>183.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>A9539-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>TEMED</td>
			<td>Carl Roth</td>
			<td>2367.3</td>
			<td></td>
		</tr>
		<tr>
			<td>tert-Butyl N-[2-[2-(2-aminoethoxy)ethoxy]ethyl]carbamate</td>
			<td>Sigma-Aldrich</td>
			<td>89761</td>
			<td>Compound 5</td>
		</tr>
		<tr>
			<td>Tricin</td>
			<td>Carl Roth</td>
			<td>6977.4</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma-Aldrich</td>
			<td>T1503-1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma-Aldrich</td>
			<td>P7949-500ml</td>
			<td></td>
		</tr>
		<tr>
			<td>WesternBright ECL spray</td>
			<td>Advansta</td>
			<td>K-12049-D50</td>
			<td></td>
		</tr>
	</tbody>
</table>

chemical inactivation of the e3 ubiquitin ligase cereblon by pomalidomide-based homo-protacs

The immunomodulatory drugs (IMiDs) thalidomide and its analogs, lenalidomide and pomalidomide, all FDA approved drugs for the treatment of multiple myeloma, induce ubiquitination and degradation of the lymphoid transcription factors Ikaros (IKZF1) and Aiolos (IKZF3) via the cereblon (CRBN) E3 ubiquitin ligase for proteasomal degradation. IMiDs have recently been utilized for the generation of bifunctional proteolysis targeting chimeras (PROTACs) to target other proteins for ubiquitination and proteasomal degradation by the CRBN E3 ligase. We designed and synthesized pomalidomide-based homobifunctional PROTACs and analyzed their ability to induce self-directed ubiquitination and degradation of CRBN. Here, CRBN serves as both, the E3 ubiquitin ligase and the target at the same time. The homo-PROTAC compound 8 degrades CRBN with a high potency with only minimal remaining effects on IKZF1 and IKZF3. CRBN inactivation by compound 8 had no effect on cell viability and proliferation of different multiple myeloma cell lines. This homo-PROTAC abrogates the effects of IMiDs in multiple myeloma cells. Therefore, our homodimeric pomalidomide-based compounds may help to identify CRBN&#8216;s endogenous substrates and physiological functions and investigate the molecular mechanism of IMiDs.

Here we described the design, synthesis and biological evaluation of a homodimeric pomalidomide-based PROTAC for the degradation of CRBN. Our PROTAC interacts simultaneously with two CRBN molecules and forms ternary complexes that induces self-ubiquitination and proteasomal degradation of CRBN with only minimal remaining effects on pomalidomide-induced neo-substrates IKZF1 or IKZF3.
Out of a series of previously published pomali...

Watch this Scientific Journal Video about Chemical Inactivation of the E3 Ubiquitin Ligase Cereblon by Pomalidomide-based Homo-PROTACs at JoVE.com

Chemical Inactivation of the E3 Ubiquitin Ligase Cereblon by Pomalidomide-based Homo-PROTACs

This work describes the synthesis and characterization of a pomalidomide-based, bifunctional homo-PROTAC as a novel approach to induce ubiquitination and degradation of the E3 ubiquitin ligase cereblon (CRBN), the target of thalidomide analogs.

The immunomodulatory drugs (IMiDs) thalidomide and its analogs, lenalidomide and pomalidomide, all FDA approved drugs for the treatment of multiple ...

Our homodimeric PROTACs are the first chemical inhibitors of Cereblon and may help to further elucidate the molecular mechanism of thalidomide analogs, as well as to investigate the physiological function of Cereblon. This new PROTAC platform technology can be highly helpful for specifically targeting proteins of interest that are otherwise considered to be untrackable. CRBN inhibition alone has no anti-tumor activity.However, CRBN degraders may have clinical implications in obesity, infectious diseases, and other disorders. The synthesis is challenging and it's hard to find optimal linkers and attachment to generate effective protein degraders when designing a PROTAC compound. To begin, place 2.46 grams of Boc-protected L-glutamine and 50 milliliters of tetrahydrofuran in a 100 milliliter round-bottomed flask, and stir at 800 rpm for one minute.Then, add 1.95 grams of 1, 1'carbonyldiimidazole and a catalytic amount of 4-pyridine. Continue stirring for 10 hours at reflux to obtain a clear colorless solution of glutarimide compound. Let the solution cool to room temperature, and remove the solvent with a rotary evaporator.Redissolve the residue in 200 milliliters of ethyl acetate and pour it into a separatory funnel. Wash the organic layer with 50 milliliters each of deionized water and brine, and dry the organic layer over sodium sulfate. Gravity filter the solution through silica gel to remove the desiccant, and then rinse the silica gel with 200 milliliters of ethyl acetate.Remove the solvent from the filtrate under vacuum to obtain Compound 1 as a colorless solid. Dry the product under vacuum overnight before using it. Next, dissolve 0.50 grams of sodium acetate in 20 milliliters of glacial acetic acid in a 100 milliliter round-bottom flask equipped with a stir bar.Add 1.25 grams of 3-fluorophthalic anhydride and 1.14 grams of glutarimide and stir at reflux for six hours to obtain a purple solution of Compound 3. Let the mixture cool to room temperature, and then pour it into 100 milliliters of deionized water and stir for 10 minutes to precipitate Compound 3. Collect the solid by filtration, wash it with water and petroleum ether, and dry it under vacuum for two days.Next, place 0.83 grams of Compound Three and 20 milliliters of dry dimethyl sulfoxide in a 50 milliliter Schlenk flask and stir for two minutes. Add 0.22 grams of alpha omega diamine linker Compound 6, and 1.05 millilitres of N, N-diisopropylethylamine and stir the mixture under argon at 90 degrees celsius for 18 hours to obtain Homodimer 8 in a dark green mixture. Let the mixture cool to room temperature and pour it into 100 millilitres of deionized water.Extract the product into three 50 milliliter portions of ethyl acetate, combine the organic layers, and wash them with 50 milliliters each of water and brine. Dry the washed organic layer over sodium sulfate, filter out the desiccant and remove the solvent under vacuum. Redissolve the residue in a minimal amount of chromatography solvent and apply to a silica gel column for purification.Collect the fluorescent product fractions, combine them, and remove the solvent to obtain Homodimer 8 as a yellow solid. To begin, dissolve 2.28 grams of Glutarimide 1 in 25 milliliters of dimethylformamide in a 100 milliliter round-bottom flask. Suspend 2.76 grams of milled potassium carbonate in this solution.Then, draw 0.62 milliliters of iodomethane into a syringe equipped with a 20-gauge needle. Add the iodomethane drop-wise over the course of 10 seconds. Stopper the flask with a rubber septum, and add a vent needle.Sonicate the mixture for two hours at room temperature to obtain Glutarimide Compound 2. Dilute the mixture with 50 milliliters of ethyl acetate and pour it into a separatory funnel. Rinse the flask into the funnel with another 50 milliliters of ethyl acetate.Work up the product and purify it with silica gel column chromatography to obtain Glutarimide 2 as a colorless solid. Compare the retention times of Glutarimide Compounds 1 and 2 to confirm that N-methylation was successful. To begin the validation, treat multiple myeloma cells with the compounds of interest.Isolate the relevant proteins, and prepare samples for a Western Blot analysis of protein degradation. Then, prepare a gel sandwich for SDS-PAGE and fill the anode buffer tank with a pH 8.9 tris-HCl solution. Load the protein samples into the gel and run it at 70 Volts for 20 minutes, followed by 115 volts for 150 minutes.Next, prepare 1x transfer buffer for immunoblotting and carefully move the gel from its cassette to the transfer buffer to equilibrate. You have to be very careful when you remove the gel from the cassette for equilibration, because it can burst and crumple very quickly. Immerse a 0.45 micrometer polyvinylidene difluoride membrane in pure methanol for at least 20 seconds to activate it, and then immerse it in 1x transfer buffer.Let the gel and the membrane equilibrate for 10 minutes. Then, assemble the Western Blotting cassette and apply 180 milliamperes for 90 minutes to transfer the proteins to the membrane. Afterwards, visualize the proteins by immunostaining.To evaluate the effects on cell viability, first, seed 50, 000 multiple myeloma cells per well of a 96 well plate in biological triplicate. Add to each well 100 microliters of media containing DMSO, or a 0.1, one, or 10 micromolar of Compound 8, Compound 9, or pomalidomide. To perform cell viability rescue experiment, instead treat the cells with a 100 nanomolar solution of Compound 8 for three hours, either before or after adding a one micromolar solution of pomalidomide.Incubate the cells for 24, 48, or 96 hours at 37 degrees celsius in a 5%carbon dioxide atmosphere, and measure cell viability with a luminescent assay. The structure of homodimeric PROTAC 8 was confirmed with proton and carbon NMR. Heterodimeric PROTAC 9 was synthesized as a negative control, as N-methylation within the glutarimide portion results in a loss of Cereblon, or CRBN, binding capability.The homo PROTAC 8 induced near complete proteosomal CRBN degradation with minimal effects on the lymphoid transcription factors IKZF1 and IKZF3. In contrast, the hetero PROTAC 9 showed behavior similar to pomalidomides. Compound 8 induced CRBN degradation could be blocked by a direct inhibitor of the proteasome, or indirectly blocked by netylation inhibition.Cells pre-treated with Compound 8 significantly resisted the effects of pomalidomide on IKZF1 and IKZF3. Compound 8 induced CRBN degradation had much less of an effect on multiple myeloma cell viability after 96 hours than the IKZF1 and IKZF3 degradation from Compound 9 and pomalidomide did. Multiple myeloma cells pre-treated with Compound 8 had significantly greater viability when exposed to pomalidomide than untreated cells, suggesting that Compound 8 could be used to mimic immunomodulatory IMiD drug-resistance.We found that Compound 8 induces complete proteasomal degradation of Cereblon, has no side effects on IKZF1 and IKZF3 cell viability and proliferation. Extending the project technology to other targets has the potential for inactivating and tracking of proteins related to cancer and other diseases. When adapting this technique for other drugs and proteins, one should carefully investigate the molecular structures of the drug and the protein target to choose the optimal linkers and attachments.The IMiDs will not work in mice because of a point mutation in Cereblon, but a transgenic knock-in mouse model exists which can be used for further animal studies. As pomalidomide is an analog thalidomide, which is highly teratogenic, we do not recommend pregnant women working with these drugs.

chemical-inactivation-e3-ubiquitin-ligase-cereblon-pomalidomide-based

Research

JoVE Journal

Chemistry

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS can be subdivided into three domains: the distal O-polysaccharide, a core oligosaccharide, and the lipid A domain consisting of a lipid A molecular species and 3-deoxy-D-manno-oct-2-ulosonic acid residues (Kdo). The lipid A domain is the only component essential for bacterial cell survival. Following its synthesis, lipid A is chemically modified in response to environmental stresses such as pH or temperature, to promote resistance to antibiotic compounds, and to evade recognition by mediators of the host innate immune response. The following protocol details the small- and large-scale isolation of lipid A from gram-negative bacteria. Isolated material is then chemically characterized by thin layer chromatography (TLC) or mass-spectrometry (MS). In addition to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS, we also describe tandem MS protocols for analyzing lipid A molecular species using electrospray ionization (ESI) coupled to collision induced dissociation (CID) and newly employed ultraviolet photodissociation (UVPD) methods. Our MS protocols allow for unequivocal determination of chemical structure, paramount to characterization of lipid A molecules that contain unique or novel chemical modifications. We also describe the radioisotopic labeling, and subsequent isolation, of lipid A from bacterial cells for analysis by TLC. Relative to MS-based protocols, TLC provides a more economical and rapid characterization method, but cannot be used to unambiguously assign lipid A chemical structures without the use of standards of known chemical structure. Over the last two decades isolation and characterization of lipid A has led to numerous exciting discoveries that have improved our understanding of the physiology of gram-negative bacteria, mechanisms of antibiotic resistance, the human innate immune response, and have provided many new targets in the development of antibacterial compounds.

Isolation and characterization of the lipid A domain of lipopolysaccharide (LPS) from gram-negative bacteria provides insight into cell surface based mechanisms of antibiotic resistance, bacterial survival and fitness, and how chemically diverse lipid A molecular species differentially modulate host innate immune responses.

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS ...

Preparing Adherent Cells for X-ray Fluorescence Imaging by Chemical Fixation

X-ray fluorescence imaging allows us to non-destructively measure the spatial distribution and concentration of multiple elements simultaneously over large or small sample areas. It has been applied in many areas of science, including materials science, geoscience, studying works of cultural heritage, and in chemical biology. In the case of chemical biology, for example, visualizing the metal distributions within cells allows us to study both naturally-occurring metal ions in the cells, as well as exogenously-introduced metals such as drugs and nanoparticles. Due to the fully hydrated nature of nearly all biological samples, cryo-fixation followed by imaging under cryogenic temperature represents the ideal imaging modality currently available. However, under the circumstances that such a combination is not easily accessible or practical, aldehyde based chemical fixation remains useful and sometimes inevitable. This article describes in as much detail as possible in the preparation of adherent mammalian cells by chemical fixation for X-ray fluorescent imaging.

Here, we present a protocol on how to determine the quantity and distribution of metals in a sample using synchrotron X-ray fluorescence. We focus on adherent cells, and describe the chemical fixation method to prepare this sample. We then describe how to mount and image the sample using synchrotron X-rays.

X-ray fluorescence imaging allows us to non-destructively measure the spatial distribution and concentration of multiple elements simultaneously over ...

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in traditional materials, including low cost and mechanical flexibility. In a similar vein, it would be advantageous to expand the use of organics into high frequency electronics and spin-based electronics. This work presents a synthetic process for the growth of thin films of the room temperature organic ferrimagnet, vanadium tetracyanoethylene (V[TCNE]x, x~2) by low temperature chemical vapor deposition (CVD). The thin film is grown at &#60;60 &#176;C, and can accommodate a wide variety of substrates including, but not limited to, silicon, glass, Teflon and flexible substrates. The conformal deposition is conducive to pre-patterned and three-dimensional structures as well. Additionally this technique can yield films with thicknesses ranging from 30 nm to several microns. Recent progress in optimization of film growth creates a film whose qualities, such as higher Curie temperature (600 K), improved magnetic homogeneity, and narrow ferromagnetic resonance line-width (1.5 G) show promise for a variety of applications in spintronics and microwave electronics.

We present the synthesis of the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]x, x~2) via low temperature chemical vapor deposition (CVD). This optimized recipe yields an increase in Curie temperature from 400 K to over 600 K and a dramatic improvement in magnetic resonance properties.

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr2+ act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO2 polymorphs and is at the origin of the epitaxial growth.

A protocol is presented for the preparation of piezoelectric macroporous epitaxial films of quartz on silicon by solution chemistry using dip-coating and thermal treatments in air.

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.