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-(dimethylamino)pyridine (5 mg) to a mixture of Boc-Gln-OH (2.46 g, 10 mmol) in THF (50 mL) in 100 mL round bottom flask with a stir bar and equipped with a reflux condenser. Heat at reflux for 10 h while stirring until a clear solution is formed.</li>
		<li>Remove the solvent under reduced pressure with a rotary evaporator, add EtOAc (200 mL) and transfer it to a separatory funnel. Wash the organic layer with H2O (50 mL) and brine (50 mL) and dry it over Na2SO4.</li>
		<li>Filter the solution through a short pad of silica gel (5 cm diameter and 5 cm height) and eluate with a further volume (200 mL) of EtOAc.</li>
		<li>Evaporate the solvent and dry the obtained colorless solid in vacuo.</li>
	</ol>
	</li>
	<li>Preparation of tert-butyl N-(1-methyl-2,6-dioxo-3-piperidyl)carbamate (compound 2)
	<ol>
		<li>Combine compound 1 (2.28 g, 10 mmol) with milled potassium carbonate (2.76 g, 20 mmol) and DMF (25 mL) in a 100 mL round bottom flask. Add iodomethane (1.42 g, 0.62 mL, 10 mmol) drop-wise using a syringe and equip the flask with a punctured rubber septum. Place the reaction vessel into an ultrasonication bath for 2 h.</li>
		<li>Dilute the&#160;reaction mixture with EtOAc (100 mL) and transfer it to a separatory funnel. Wash the organic layer with 1 N NaOH (2x 25 mL), H2O (25 mL), and brine (25 mL), and dry it over Na2SO4.</li>
		<li>Filter and evaporate the solvent. Purify the product by column chromatography over silica gel (6 cm column diameter and 20 cm height) using petroleum ether/EtOAc (2:1).</li>
	</ol>
	</li>
	<li>Preparation of 2-(2,6-dioxopiperidin-3-yl)-4-fluoroisoindoline-1,3-dione (compound 3)
	<ol>
		<li>Combine 3-fluorophthalic anhydride (1.25 g, 7.5 mmol), glutarimide 1 (1.14 g, 5 mmol) and a solution of sodium acetate (0.50 g, 6.0 mmol) in glacial acetic acid (20 mL) in a 50 mL round bottom flask with a stir bar and equipped with a reflux condenser. Heat the mixture at 120 &#176;C for 6 h.</li>
		<li>After cooling, pour the purple mixture onto H2O (100 mL) and stir for 10 min. Collect the formed solid by filtration, wash with H2O (3 &#215; 5 mL) and petroleum ether (3 &#215; 5 mL) and dry in vacuo.</li>
	</ol>
	</li>
	<li>Preparation of 4-fluoro-2-(1-methyl-2,6-dioxopiperidin-3-yl)isoindoline-1,3-dione (compound 4)
	<ol>
		<li>Combine 3-fluorophthalic anhydride (1.25 g, 7.5 mmol), glutarimide 2 (1.21 g, 5 mmol) and a solution of sodium acetate (0.50 g, 6.0 mmol) in glacial acetic acid (20 mL) in a 100 mL round bottom flask with a stir bar and equipped with a reflux condenser. Heat the mixture at 120 &#176;C for 6 h.</li>
		<li>After cooling, pour the purple mixture onto H2O (100 mL) and stir for 10 min. Collect the formed solid by filtration, wash with H2O (3 &#215; 5 mL) and petroleum ether (3 &#215; 5 mL) and dry in vacuo.</li>
	</ol>
	</li>
	<li>Preparation of tert-butyl N-[2-[2-[2-[[2-(2,6-dioxo-3-piperidyl)-1,3-dioxo-isoindolin-4-yl]amino]ethoxy]ethoxy]ethyl]carbamate (compound 7)
	<ol>
		<li>Charge a 50 mL round bottom flask with tert-butyl N-[2-[2-(2-aminoethoxy)ethoxy]ethyl]carbamate (5, 0.41 g, 1.65 mmol), compound 3 (0.41 g, 1.50 mmol), dry DMF (10 mL) and DIPEA (0.39 g, 0.51 mL, 3.0 mmol). Equip with a stir bar and a reflux condenser. Heat under argon atmosphere at 90 &#176;C for 10 h.</li>
		<li>After cooling to room temperature, pour the dark green mixture onto H2O (100 mL) and extract with EtOAc (3x 50 mL) in a separatory funnel. Wash the combined organic layers with H2O (50 mL) and brine (50 mL), dry over Na2SO4, filter, and concentrate in vacuo.</li>
		<li>Purify the crude product by column chromatography over silica gel (3 cm column diameter and 60 cm height) using a gradient of petroleum ether/EtOAc (1:1 to 1:2).</li>
	</ol>
	</li>
	<li>Preparation of homodimer (compound 8)
	<ol>
		<li>Combine the &#945;,&#969;-diamine linker 6 (0.22 g, 0.22 mL, 1.50 mmol), DIPEA (1.05 mL, 6.00 mmol) and a solution of 3 (0.83 g, 3.00 mmol) in dry DMSO (20 mL) in a 50 mL round bottom flask with a stir bar and equipped with a reflux condenser. Heat under argon atmosphere at 90 &#176;C for 18 h.</li>
		<li>After cooling to room temperature, pour the dark green mixture onto H2O (100 mL) and extract with EtOAc (3x 50 mL) in a separatory funnel. Wash the combined organic layers with H2O (50 mL) and brine (50 mL), dry over Na2SO4, filter and concentrate in vacuo.</li>
		<li>Purify the crude product by column chromatography over silica gel (3 cm column diameter and 50 cm height) using a gradient of petroleum ether/EtOAc (1:2) to EtOAc.</li>
	</ol>
	</li>
	<li>Preparation of heterodimer (compound 9)
	<ol>
		<li>Dissolve compound 7 (0.83 g, 1.65 mmol) in dry CH2Cl2 (10 mL). Add trifluoroacetic acid (10 mL) and stir the yellow mixture at 40 &#176;C for 2 h in a closed 50 mL round bottom flask.</li>
		<li>Remove the volatiles and coevaporate with CH2Cl2 (4x 5 mL). Dry the residue in vacuo for 10 h.</li>
		<li>Redissolve the material in dry DMF (20 mL). Add compound 4 (0.44 g, 1.50 mmol) and DIPEA (0.78 g, 1.05 mL, 6.00 mmol) and equip the flask with a reflux condenser. Heat under argon atmosphere at 90 &#176;C for 10 h.</li>
		<li>After cooling to room temperature, pour the dark green mixture onto H2O (100 mL) and extract with EtOAc (3x 50 mL) in a separatory funnel. Wash the combined organic layers with saturated NaHCO3 (50 mL), H2O (50 mL), 10% KHSO4 (50 mL), H2O (50 mL), and brine (50 mL), dry over Na2SO4, filter and concentrate in vacuo.</li>
		<li>Purify the crude product by column chromatography over silica gel (3 cm column diameter and 50 cm height) using a gradient of petroleum ether/EtOAc (1:2) to EtOAc.</li>
		<li>Elucidate and verify molecule structure (Figure 5A compound 8, 5B compound 9) by 1H NMR and 13C NMR spectra in DMSO-d6 on a nuclear magnetic resonance (NMR) spectrometer. Check that the purity of both compounds is higher than 97% by means of liquid chromatography-mass spectrometry (LC-MS), applying a diode array detection (DAD) at 220&#8211;500 nm.</li>
	</ol>
	</li>
</ol>
2. Functional validation of PROTAC molecules
<ol>
	<li>Western blot analysis of CRBN degradation by PROTACs 
	NOTE: The effects of compound 8 and compound 9 on CRBN protein level were tested by western blot analysis. In addition, the impact on IKZF1 and IKZF3 levels could also be confirmed (Figure 6).
	<ol>
		<li>Sample preparation
		<ol>
			<li>Dissolve compounds 8 and 9, lenalidomide (Len), pomalidomide (Pom), MG132, and MLN-4924 in DMSO at a concentration of 10 mM, aliquot and store at -80 &#176;C until further usage.</li>
			<li>Seed 1 x 106 MM1S cells in a 6-well plate with 2.5 mL media and treat cells with 100 nM or 1 &#181;M compound 8 or 9 for 24 h.</li>
			<li>Harvest cells after treatment and centrifuge at 700 x g, 5 min, 4 &#176;C. Wash cell pellet with cold 1x PBS to remove remaining media, centrifuge at 700 x g, 5 min, 4 &#176;C, and discard supernatant. Repeat this step once.</li>
			<li>Lyse cells in lysis buffer (25 mM Tris HCl pH 7.4, 150 mM NaCl, 1% NP-40, 1 mM EDTA, 5% glycerol, 1x Protease &#38; Phosphatase Inhibitor Cocktail) for 10 min on ice, centrifuge at 320 x g for 10 min, 4 &#176;C. Harvest supernatant and determine protein concentration by a bicinchoninic acid protein assay (BCA assay) according to the manufacturer&#8217;s protocol.</li>
			<li>Denature proteins (15&#8211;30 &#181;g/sample) with 1x LDS loading buffer (5% 2-mercaptoethanol) and boil 10 min, 75 &#176;C.</li>
		</ol>
		</li>
		<li>SDS-PAGE
		<ol>
			<li>Fix gel sandwich with a 10% separating gel [4 mL 3x gel buffer (3 M Tris/HCl, 0.3% (w/v) sodium dodecyl sulfate (SDS), pH 8.45), 4 mL acrylamide 30%, 2.52 mL glycerol 50%, 1.395 mL H2O, 75 &#181;L 11% ammonium persulfate (APS), and 9.75 &#181;L TEMED] and a 4% stacking gel [1.992 mL 3x gel buffer, 0.792 mL 30% acrylamide, 3.168 mL H2O, 36 &#181;L 11% APS, and 6 &#181;L TEMED] in an electrode assembly unit. Remove combs, flush wells with cathode buffer (100 mM Tris/HCl, 100 mM tricine, 0.1% (w/v) SDS), and load samples.</li>
			<li>Fill anode buffer (100 mM Tris/HCl, pH 8.9) into the tank. Load protein sample from step 2.1.1.4 and run SDS-PAGE at 70 V, 20 min, followed by 115 V, 150 min at constant voltage.</li>
		</ol>
		</li>
		<li>Immunoblotting and detection of CRBN, IKZF1 and IKZF3
		<ol>
			<li>Activate PVDF membrane (0.45 &#181;m) in 100% methanol for 1 min. Equilibrate membrane and separating gel in 1x transfer buffer [10x transfer buffer (192 mM glycine, 25 mM Tris-base/HCl, 900 mL H2O), 20% methanol, 0.1% SDS, pH 8.3].</li>
			<li>Assemble blotting cassette according to manufacturer&#8217;s protocol. Transfer gel at 180 mA for 90 min.</li>
			<li>Wash membrane 3x in 1x TBS-T (25 mM Tris/HCl, 150 mM NaCl, pH 7.6, 0.1% Tween 20) for 5&#8211;10 min each at room temperature. Block membrane in 5% nonfat-dried milk (NFDM), TBS-T for 1 h at room temperature. Wash membrane 3x in 1X TBS-T for 5&#8211;10 min each at room temperature.</li>
			<li>Incubate membrane with primary antibody for CRBN (1:500 in 5% BSA, TBS-T) with gentle shaking at 4 &#176;C, overnight.</li>
			<li>Wash membrane 3x in 1X TBS-T for 5&#8211;10 min each at room temperature. Incubate membrane with anti-mouse (1:10.000 in 5% NFDM, TBS-T) or anti-rabbit (1:5.000 in 5% NFDM, TBS-T) secondary antibody coupled to horseradish peroxidase HRP (1 h at room temperature.)</li>
			<li>Wash membrane 2x in 1X TBS-T for 5&#8211;10 min each at room temperature. Repeat this step twice with 1x TBS.</li>
			<li>Incubate membrane for 2 min with HRP substrate solution according to manufacturer&#8217;s protocols and detect chemiluminescence in a chemiluminescence detection device.</li>
			<li>Wash membrane 1x in 1X TBS for 5&#8211;10 min each at room temperature. For release of antibodies, strip membrane in commercially available stripping buffer for 15 min. Wash membrane 3x in 1X TBS for 5&#8211;10 min each at room temperature.</li>
			<li>Reblock membrane in 5% nonfat-dried milk, TBS-T for 1 h at room temperature. Wash membrane 3x in 1x TBS-T for 5&#8211;10 min each at room temperature and reprobe with IKZF1, IKZF3 or tubulin according to step 2.1.3.4.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Competition experiments with MG132, MLN4942 or pomalidomide 
	NOTE: To confirm whether CRBN is degraded via the ubiquitin-proteasome pathway, we performed competition experiments with the proteasome inhibitor MG132 and a neddylation activating enzyme (NAE) inhibitor MLN4942 (Figure 7).
	<ol>
		<li>Seed 1 x 106 MM1S cells per well in a 6-well plate. Pretreat cells with 10 &#181;M MG132, 10 &#181;M MLN4942, or lenalidomide (100x), and incubate 1 h at 37 &#176;C, 5% CO2.</li>
		<li>Add 100 nM compound 8 for 3 h at 37 &#176;C, 5% CO2.</li>
		<li>Harvest cells for western blot according to step 2.1.1.</li>
	</ol>
	</li>
	<li>Cell viability assays in multiple myeloma cell lines 
	NOTE: This assay is used to test the impact on cell viability and additionally, antagonize the effect of IMiDs on multiple myeloma cells by pretreatment of the cells with compound 8 (Figure 8, Figure 9A,B).
	<ol>
		<li>Seed 5 x 104 MM1S cells per well in a 96-well plate in biological triplicates for viability assay. For western blot analysis, seed 1 x 106 MM1S cells per well in a 6-well plate in biological triplicates.</li>
		<li>Treat cells with DMSO or 100 nM, 1 &#181;M, or 10 &#181;M compound 8, compound 9 or pomalidomide and incubate for 24 h, 48 h, or 96 h at 37 &#176;C, 5% CO2. For rescue experiments, treat cells with 100 nM compound 8 for 3 h, before or after addition of 1 &#181;M pomalidomide and incubate for 96 h.</li>
		<li>Measure 96-well plate luminescence with a luminescent cell viability assay, according to the manufacturer&#8217;s protocol on a plate reader or harvest cells from the 6-well plate for western blot analysis.</li>
	</ol>
	</li>
</ol>

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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 authors do not declare a potential financial conflict of interest.

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 ...

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

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JoVE Journal

Chemistry

13.0K Views.  University Hospital Ulm. 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.

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

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 ...

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

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 ...

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.