This work was supported by the Lehigh University Start-up Package. We thank Dr. Walter Fast for providing the GST-PAD4 plasmid for protein expression.

1. PAD4 Trasformazione, Espressione e purificazione <ol><li> Per PAD4 trasformazione, trasformare il plasmide contenente pGEX PAD4 GST fusione in chimicamente competente E. Coli (BL21 (DE3)), le cellule per l&#39;espressione di proteine ​​utilizzando la seguente procedura. Preparare chimicamente competente (cloruro di calcio) E. Coli (BL21 (DE3)), le cellule secondo protocolli standard. <ol><li> Scongelare 50 ml di preparato in precedenza BL21 chimicamente competente (DE3) celle su ghiaccio e mescolare con 1 ml di plasmide pGEX contenente gene PAD4 in una provetta da 5 ml. Incubare la miscela in ghiaccio per 10 min, agitando delicatamente ogni 2 min. </li><li> Heat Shock cellule collocando la miscela in un bagno d&#39;acqua a 42 ° per 40 sec. Porre immediatamente la miscela di cellule-plasmide indietro su ghiaccio per 2 minuti per permettere alle cellule di recuperare. Aggiungere 1 ml di brodo LB sterile al composto e mettere in ghiaccio per 1 min. </li><li> Incubare il calore cellule scioccato a 37 ° C, agitazione a 250 rpm per 1hr. Pipettare 75 ml di cellule trasformate su una piastra di agar ampicillina resistenti e incubare a 37 ° C per 15 h. Piastra Conservare a 4 ° C. </li></ol></li><li> PAD4 Expression. <ol><li> Raccogliere 1 colonia di (DE3) cellule BL21 dalla piastra di agar ampicillina e posto in 5 ml di LB contenente ampicillina 1x. Posto in incubatrice e agitare O / N a 37 ° C. </li><li> Trasferire i 5 ml di LB (avviamento) in 1 L di sterile LB contenente ampicillina triidrato 1x (MW 403,45 g / mol). Posizionare la crescita in un incubatore agitazione 37 ° C. Monitorare l&#39;OD 600 della crescita. Quando la crescita raggiunge un diametro esterno 600 di 0,3, muovere la crescita in 16 ° C agitazione incubatore. </li><li> Dopo aver raggiunto un OD 600 di 0,6, induce le cellule con isopropylthiagalactoside 0,3 mM (IPTG, MW 238,30 g / mol). Consentono alle cellule siano scossi per 15 ore a 16 ° C. </li><li> Celle di raccolta per centrifugazione a 4000 xg per 20 minuti a 0 ° C. Eliminare il surnatante e conservare pellet a -80 ° C. </li></ol></li><li> PAD4 Purificazione <ol><li> Risospendere il pellet contenente il PAD4 espresso in BL21 (DE3) cellule in tampone 50 mM NaCl (MW 58.44 g / mol), 300 mM NaH 2 PO 4 (PM 119.98 g / mol), imidazolo 10 mM (MW 68,077 g / mol), 0,1 mM fluoruro phenylmethylsulfonyl (PMSF, MW 174,94 g / mol) e 1 mM ditiotreitolo (DTT, 154.25 g / mol), pH = 8,0. </li><li> Lisare le cellule tramite sonicazione per 15 min a 4 ° C. Dopo sonicazione, centrifugare il lisato cellulare a 20.000 xg per 20 min a 0 ° C. Eliminare il surnatante e riporlo. Batch il surnatante con il glutatione (GSH) agarosio per 30 minuti a RT. </li><li> Scolare il surnatante dal GST perline / colonna per gravità. Lavare perline con 4 x 25 ml di 1x PBS (tampone fosfato, pH = 8.0) a temperatura ambiente. </li><li> Eluire PAD4 con 2 x 10 ml di tampone di eluizione, Tris 50 mM (idrossimetil) aminometano (Tris Base, MW 121,14 g / mol), 10 mM glutatione (GSH, MW 307,32 g / mol), pH = 8,0. </li><li> Concentrato PAD4 con 100k MW cut-oprovette da centrifuga ff e centrifugare a 4000 xg per 20 minuti a 4 ° C. Aliquota di proteine ​​in 200 volumi in microlitri 1,0 ml provette da microcentrifuga e conservare a -80 ° C. </li></ol></li></ol> 2. Preparare soluzioni madre di buffer <ol><li> Pesare il cloruro di sodio (NaCl, MW 58.44 g / mol) e preparare una soluzione 2 M. Mescolare fino a quando la soluzione chiara. </li><li> Pesare Tris (idrossimetil) aminometano (Tris Base, MW 121,14 g / mol) e preparare una soluzione 2 M, pH = 8,0. Mescolare fino a quando la soluzione chiara. </li><li> Pesare diidrato cloruro di calcio (CaCl 2 2H 2 O, MW 147.01 g / mol) e preparare una soluzione 500 mM. Mescolare fino a quando la soluzione chiara. </li><li> Pesare Tris (2-carbossietil) fosfina (TCEP, MW 250,19 g / mol) e preparare una soluzione 200 mM. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. </li><li> Pesare ditiotreitolo (DTT, MW 154,25 g / mol) e preparare una soluzione 1 M. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. </li><li> Preparareuna soluzione allo 0,5% di Triton X-100. </li><li> Pesare etilendiamminotetraacetico (EDTA, MW 292,24 g / mol) e preparare una soluzione 100 mM. Mescolare fino a quando la soluzione chiara. </li><li> Pesare Z- Arg- Arg- 7- amido- 4- metilcumarina cloridrato (ZRcoum, MW 621,69 g / mol) e preparare una soluzione 10 mM in dimetilsolfossido (DMSO). </li></ol> 3. PAD4 test a 37 ° C <ol><li> Da 10 ZRcoum mM magazzino, preparare una soluzione 125 mM di ZRcoum in acqua. Questa soluzione 125 mM ZRcoum sarà Soluzione A. </li><li> Preparare un buffer di 62,5 mM NaCl, 62,5 mM Tris, 12,5 mM CaCl 2, 6,25 mM DTT, e 5 mM PAD4 (pH = 8,0). Questo sarà soluzione B. </li><li> Preparare un buffer di 62,5 mM NaCl, 62,5 mM Tris, 12,5 mM CaCl 2 e 6,25 mM DTT (pH = 8,0). Questo sarà soluzione C. </li><li> Pesare tripsina, cristallino (da pancreas bovino) e preparare 10 mg / ml in EDTA 100 mM. Mescolare fino a quando la soluzione chiara e conservare a -20° C. Questo sarà soluzione D. </li><li> Ottenere una piastra a 96 pozzetti e designare un numero di pozzi per i controlli (non PAD4) e pozzi di prova (+ PAD4). </li><li> Pipettare 160 ml di soluzione B in pozzi di prova e pipetta 160 ml di soluzione di C nei pozzetti di controllo. Incubare per 15 minuti a 37 ° C. </li><li> Pipettare 40 ml di soluzione A in tutti i pozzetti e incubare a 37 ° C per 45 min. </li><li> Pipettare 10 ml di dH 2 O a metà dei pozzetti di controllo e la metà dei pozzi di prova. Per l&#39;altra metà dei pozzetti di controllo e comandi di test, pipetta 10 ml di soluzione di D. Incubare per 10 min a 37 ° C. </li><li> Ottenere una fluorescenza lettura su un lettore multimodale con lunghezza d&#39;onda di eccitazione di 345 nm e una lunghezza d&#39;onda di emissione di 465 nm. </li></ol> 4. PAD4 test a temperatura ambiente <ol><li> Da 10 ZRcoum mM magazzino, preparare una soluzione di 50 mM di ZRcoum in acqua. Questa soluzione ZRcoum 50 micron sarà Soluzione A. </li><li> Preparare un buffer di Na 100 mMCl, Tris 100 mM, 20 mM CaCl 2, 2 TCEP mM, 0,02% Triton X-100, e 8 mM PAD4 (pH = 8,0). Questo sarà soluzione B. </li><li> Preparare un buffer di NaCl 100 mM, Tris 100 mM, 20 mM CaCl 2, 2 TCEP mM e 0,02% Triton X-100 (pH = 8,0). Questo sarà soluzione C. </li><li> Pesare tripsina, cristallino (da pancreas bovino) e preparare 10 mg / ml in EDTA 100 mM. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. Questo sarà soluzione D. </li><li> Ottenere una piastra da 384 pozzetti e designare pozzetti per i controlli (non PAD4) e pozzi di prova (+ PAD4). </li><li> Pipettare 25 ml di soluzione B in pozzi di prova e pipetta 25 ml di soluzione di C nei pozzetti di controllo. Consentire buffer con / senza PAD4 ad incubare in pozzetti per 20 minuti a RT. </li><li> Pipettare 25 ml di soluzione C in tutti i pozzetti e incubare per 45 minuti a temperatura ambiente. </li><li> Pipettare 10 ml di dH 2 O a metà dei pozzetti di controllo e la metà dei pozzi di prova. Per l&#39;altra metà dei pozzetti di controllo e comandi di test, pipette 10 ml della soluzione D. Incubare a temperatura ambiente per 10 min. </li><li> Ottenere una fluorescenza lettura su un lettore multimodale con lunghezza d&#39;onda di eccitazione di 345 nm e una lunghezza d&#39;onda di emissione di 465 nm. </li></ol> 5. PAD4 Andamento temporale saggi a 37 ° C e RT <ol><li> Da 10 ZRcoum mM magazzino, preparare una soluzione 125 mM di ZRcoum in acqua. Questa soluzione 125 mM ZRcoum sarà Soluzione A. </li><li> Preparare un buffer di 62,5 mM NaCl, 62,5 mM Tris, 12,5 mM CaCl 2, 6,25 mM DTT, e 5 mM PAD4 (pH = 8,0). Questo sarà soluzione B. </li><li> Pesare tripsina, cristallino (da pancreas bovino) e preparare 10 mg / ml in EDTA 100 mM. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. Questo sarà soluzione C. </li><li> Ottenere 2 piastre a 96 pozzetti e pipetta 160 ml di soluzione di B in # quantità di pozzi (# di pozzi dipenderà da quanti punti di tempo). </li><li> Incubare una piastra a 96 pozzetti a 37 ° C. Incubare l&#39;altra piastra da 96 pozzetti a temperatura ambiente. </li><li> Semeette 40 ml di soluzione A in tutti i pozzetti in entrambe le piastre a 96 pozzetti e subito Pipettare 10 ml di Soluzione C nelle t = 0 min pozzi. Continuare ad aggiungere 10 ml di soluzione C in punti temporali specifici prima di aver spento tutti i pozzetti. </li><li> Ottenere una fluorescenza lettura su un lettore multimodale con lunghezza d&#39;onda di eccitazione di 345 nm e una lunghezza d&#39;onda di emissione di 465 nm. </li></ol> 6. PAD4 Inibizione test a temperatura ambiente <ol><li> Da 10 ZRcoum mM magazzino, preparare una soluzione 83 mM di ZRcoum in acqua. Questa soluzione ZRcoum 83 mM sarà Soluzione A. </li><li> Pesare Cl-amidina (MW 424,8 g / mol) e preparare una soluzione madre a 100 micron. Questo sarà soluzione B. </li><li> Preparare un buffer di NaCl 100 mM, Tris 100 mM, 20 mM CaCl 2, 2 TCEP mM, 0,02% Triton X-100, e 8 mM PAD4 (pH = 8,0). Questo sarà soluzione C. </li><li> Preparare un buffer di NaCl 100 mM, Tris 100 mM, 20 mM CaCl 2, 2 TCEP mM e 0,02% Triton X-100 (pH = 8,0). Thè sarà Soluzione D. </li><li> Pesare tripsina, cristallino (da pancreas bovino) e preparare 10 mg / ml in EDTA 100 mM. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. Questo sarà Soluzione E. </li><li> Ottenere una piastra da 384 pozzetti e designare pozzi per i controlli (non PAD4), pozzi di prova (+ PAD4), e pozzi di inibizione (PAD4 + Cl-ammidinici). </li><li> Pipettare 25 ml di soluzione C in pozzi di prova e pipetta 25 ml di soluzione di D nei pozzetti di controllo. Consentire buffer con / senza PAD4 ad incubare in pozzetti per 20 minuti a RT. </li><li> Pipettare 10 ml di soluzione B nei pozzetti di inibizione e incubare per 20 minuti a Rte. </li><li> Pipettare 15 ml di soluzione A in tutti i pozzetti e incubare per 45 minuti a temperatura ambiente. </li><li> Pipettare 10 ml di soluzione E a tutti i pozzetti. Incubare a temperatura ambiente per 10 minuti. </li><li> Ottenere una fluorescenza lettura su un lettore multimodale con lunghezza d&#39;onda di eccitazione di 345 nm e una lunghezza d&#39;onda di emissione di 465 nm. </li></ol> 7. greggio lisato Assaya RT <ol><li> Dopo la raccolta delle cellule dal PAD4 1 L di crescita, risospendere le cellule in 10 ml di 50 mM Tris, 50 mM NaCl, 0.1 mM phenylmethylsulfonyl fluoruro (PMSF, MW 174,94 g / mol) e 1 mM ditiotreitolo (DTT, 154.25 g / mol), pH = 8.0. </li><li> Lisare le cellule tramite sonicazione per 15 min a 4 ° C. Centrifugare il lisato cellulare a 20.000 xg per 20 min a 0 ° C. Concentrare il surnatante limpido per la metà del volume mediante centrifugazione a 4000 rpm a 4 ° C con 100k MW provette di cut-off. </li><li> Da 10 ZRcoum mM magazzino, preparare una soluzione 250 mM di ZRcoum in acqua. Questa soluzione 250 mM ZRcoum sarà Soluzione A. </li><li> Preparare un buffer di NaCl 100 mM, Tris 100 mM, 20 mM CaCl 2, e 2 TCEP mM (pH = 8,0). Questo sarà soluzione B. </li><li> Pesare tripsina, cristallino (da pancreas bovino) e preparare 10 mg / ml in EDTA 100 mM. Mescolare fino a quando la soluzione chiara e conservare a -20 ° C. Questo sarà soluzione C. </li><li> Ottenere una piastra da 384 pozzetti nero e designmangiato pozzetti per i controlli (senza lisato cellulare) e le fonti di prova (+ lisato cellulare). </li><li> Pipettare 100 ml di soluzione B in tutti i pozzetti e le pipette 60 ml di lisato cellulare nei pozzetti di prova. Incubare per 20 minuti a RT. </li><li> Pipettare 40 ml di soluzione A in tutti i pozzetti e incubare per 45 minuti a temperatura ambiente. </li><li> Pipettare 10 ml di soluzione C a tutti i pozzetti. Incubare a temperatura ambiente per 10 minuti. </li><li> Ottenere una fluorescenza lettura sul lettore multimodale con lunghezza d&#39;onda di eccitazione di 345 nm e una lunghezza d&#39;onda di emissione di 465 nm. </li></ol>

<ol>
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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+arginine+deiminase+4:+a+target+for+an+epigenetic+cancer+therapy.">Protein arginine deiminase 4: a target for an epigenetic cancer therapy.</a> Cell. Mol. Life Sci. 68, 709-720 (2011).</li><li>Luo, Y., Knuckley, B., Lee, Y. H., Stallcup, M. R., Thompson, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fluoroacetamidine-based+inactivator+of+protein+arginine+deiminase+4:+design,+synthesis,+and+in+vitro+and+in+vivo+evaluation.">A fluoroacetamidine-based inactivator of protein arginine deiminase 4: design, synthesis, and in vitro and in vivo evaluation.</a> J. Am. Chem. Soc. 128, 1092-1093 (2006).</li><li>Knuckley, 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=Substrate+specificity+and+kinetic+studies+of+PADs.">Substrate specificity and kinetic studies of PADs.</a> Biochemistry. 1, 4852-4863 (2010).</li><li>Knipp, M., Vasak, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+colorimetric+96-well+microtiter+plate+assay+for+the+determination+of+enzymatically+formed+citrulline.">A colorimetric 96-well microtiter plate assay for the determination of enzymatically formed citrulline.</a> Anal. Biochem. 286, 257-264 (2000).</li><li>Knuckley, 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=A+fluopol-ABPP+HTS+assay+to+identify+PAD+inhibitors.">A fluopol-ABPP HTS assay to identify PAD inhibitors.</a> Chem. Commun. 46, 7175-7177 (2010).</li><li>Bicker, K. L., Subramanian, V., Chumanevich, A. A., Hofseth, L. J., Thompson, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seeing+citrulline:+development+of+a+phenylglyoxal-based+probe+to+visualize+protein+citrullination.">Seeing citrulline: development of a phenylglyoxal-based probe to visualize protein citrullination.</a> J. Am. Chem. Soc. 134, 17015-17018 (2012).</li><li>Wang, Q., Priestman, M. A., Lawrence, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+of+protein+arginine+deiminase+activity+by+using+fluorescence+quenching:+multicolor+visualization+of+citrullination.">Monitoring of protein arginine deiminase activity by using fluorescence quenching: multicolor visualization of citrullination.</a> Angew. Chem. Int. Ed. Engl. 52, 2323-2325 (2013).</li><li>Jones, J. 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=Synthesis+and+screening+of+a+haloacetamidine+containing+library+to+identify+PAD4+selective+inhibitors.">Synthesis and screening of a haloacetamidine containing library to identify PAD4 selective inhibitors.</a> ACS Chem. Biol. 7, 160-165 (2012).</li><li>Dreyton, C. 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=.">.</a> Optimization and characterization of a pan protein arginine deiminase (PAD) inhibitor. , (2010).</li><li>Shimoyama, 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=Deimination+stabilizes+histone+H2A/H2B+dimers+as+revealed+by+electrospray+ionization+mass+spectrometry.">Deimination stabilizes histone H2A/H2B dimers as revealed by electrospray ionization mass spectrometry.</a> J. Mass Spectrom. 45, 900-908 (2010).</li><li>Luo, Y., 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=Inhibitors+and+inactivators+of+protein+arginine+deiminase+4:+functional+and+structural+characterization.">Inhibitors and inactivators of protein arginine deiminase 4: functional and structural characterization.</a> Biochemistry. 45, 11727-11736 (2006).</li></ol>

The authors have nothing to disclose.

Herein, a fluorescence based assay was successfully developed that monitors the activity of PAD4. The assay has proven to be incredibly robust in a number of high-throughput conditions and is also compatible with whole cell lysates37.
The affinity between the histone proteins and the DNA strands surrounding it loosens due the neutralization of the positive charge on the arginine side chain upon citrullination. It was envisioned that the neutralization of the arginine side-chain coul...

Un gran numero di proteine ​​di mammifero sono fortemente modificato dall&#39;azione di enzimi seguito della biosintesi delle proteine ​​del ribosoma. Queste modificazioni post-traduzionali (PTM) possono aumentare notevolmente la diversità funzionale del proteoma modificando le dimensioni, la carica, la struttura, e lo stato di oligomerizzazione (tra le altre caratteristiche) di proteine ​​1-3. Di conseguenza, il cambiamento della struttura di proteine ​​può portare a conseguenze fisiologiche, quali la degradazione delle proteine, differenziazione cellulare, segnalazione, la modulazione dell&#39;espressione genica, e le interazioni proteina-proteina. Mentre queste modificazioni sono prevalenti in una grande percentuale di tutte le proteine ​​umane, il terminale termina il istoni subiscono un numero insolitamente elevato di modificazioni covalenti 4. Istoni sono una famiglia di proteine ​​strutturali che facilitano la condensazione del DNA genomico. Covalenti modificazioni delle code istoniche non strutturati sono effettuate e regolate da una series di enzimi in grado di catalizzare la modifica covalente di residui (scrittori), invertire le stesse modifiche (gomme), e distinguere tra i cambiamenti che sono impresse sulle code degli istoni (lettori) 5-7. In realtà, la maggior parte dei PTM conosciute si possono osservare in questo breve segmento del istoni compresi metilazione, fosforilazione, acetilazione, sumoilazione, ubiquitinazione e citrullination 8. Citrullination comporta la conversione del peptidil-arginina al t RNA non codificato peptidil-citrullina (Figura 1A). Le proteine, responsabili di questa catena di neutralizzazione lato, sono membri del PAD (p eptide un rginine eiminase d) famiglia di proteine, che sono tutti enzimi calcio-dipendenti. 9,10. Fino ad oggi, cinque membri della famiglia PAD sono state descritte (PAD1, PAD2, PAD3, PAD4, e PAD6). Ogni membro di questa famiglia sembra indirizzare proteine ​​cellulari distinti e anche visualizza unique profili distribuzione tissutale. PAD4 è l&#39;unico membro di questa famiglia di proteine ​​note per essere localizzato all&#39;interno del nucleo tramite una sequenza di localizzazione nucleare 11. Pertanto, è stato dimostrato per deiminate un numero di bersagli nucleari, comprese le catene laterali di arginina sulle code N-terminali degli istoni H2A residuo di arginina (3 H2R3), H3 (H3R2, H3R17 e H3R26) e H4 (H4R3) 12, 13. Mentre ciascuna delle isoenzimi PAD hanno funzioni fisiologiche specifiche e critiche, PAD4 ha ricevuto molta più attenzione a causa del suo ruolo in una serie di processi umani in cellule di entrambi i malati e sani. Recentemente, PAD4 ha dimostrato di essere un membro della pluripotenza trascrizionale di rete 14. Entrambi i livelli di espressione PAD4 e l&#39;attività hanno dimostrato di essere elevata durante la riprogrammazione e la terra statali stati pluripotenti nei topi. Controllando la regolazione dei geni di cellule staminali, PAD4 può mantenere un ruolo centrale nella riprogrammazione cellulare efficienza. PAD4 è stato anche coinvolto nelformazione di trappole extracellulari dei neutrofili, che dopo il legame di agenti patogeni consentire loro liquidazione sistema. La hypercitrullination di proteine ​​istoniche da PAD4 induce decondensazione della cromatina, che serve come materiale di base per l&#39;incapsulamento di batteri patogeni da parte della trappola extracellulare, in modo da scongiurare infezioni batteriche 15,16. Inoltre, PAD4 è stata trovata a svolgere un ruolo attivo in una serie di malattie umane. È stato precedentemente dimostrato che l&#39;espressione aberrante di PAD4 è associato con l&#39;insorgenza e la gravità di artrite reumatoide, morbo di Alzheimer, morbo di Parkinson, sclerosi multipla e 17. Infatti, la presenza di anticorpi anti-proteina citrullinati è uno dei biomarcatori diagnostici e prognostici più affidabili e definitive di artrite reumatoide 18. Analogamente, l&#39;attività PAD4 disregolazione stato recentemente osservato in un certo numero di tumori umani inclusi dell&#39;ovaio, della mammella, del polmone, und tumori esofagei 19-22. Il legame tra PAD4 e il cancro ha dimostrato di essere mediata attraverso l&#39;oncogene ELK1 o tramite il tumore soppressore p53 proteina 22,23 e lavoro precedente ha suggerito che PAD4 potrebbe essere un anti-cancro nuovo bersaglio terapeutico 17,24,25. Come una prova di principio studio, l&#39;esaurimento delle PAD4 via shRNA nella linea cellulare del cancro del colon-retto HCT116 si è rivelato essere sufficiente per indurre l&#39;apoptosi e arresto del ciclo cellulare 26. Un inibitore irreversibile PAD4 recentemente sviluppato ha portato ad una riduzione del settanta per cento della massa tumorale nei topi 27. Piuttosto notevole, l&#39;inibizione PAD4 sembrava operare come una terapia mirata che ha provocato l&#39;uccisione selettiva delle cellule cancerose risparmiando cellule non trasformate. L&#39;uso di piccole molecole per disattivare la funzione di PAD4 può rivelarsi una potente strategia nuova per colpire le cellule tumorali o di aumentare chemioterapici cancro esistenti 28. Purtroppo, un potenda inibitore reversibile PAD4 deve ancora essere scoperto. Un certo numero di inibitori covalenti sono stati sviluppati utilizzando il / maniglia imidine fluoro cloro che imita il substrato arginina 27,29,30 e hanno dimostrato di essere strumenti pratici per comprendere il ruolo di PAD4 in entrambe le cellule statali sani e malati. Tuttavia, queste molecole inibiscono tutte le pastiglie attivi con potenza simile. Pertanto, la necessità di un saggio superficiale che segnala l&#39;attività di PAD4 è cruciale. Fino ad oggi, PAD4 saggi sono stati descritti che collegano il rilascio di ammoniaca dalla reazione a una lettura colorimetrica 31, utilizzare un analogo substrato chloroamidine fluorescente per fluorescenza polarizzata test 32, si basano sulla reazione acida assistita tra gliossale e citrullina 33, e coppia l&#39;attività PAD4 ad una fluorescenza dequenching passo 34. Di questi, solo il modificatore strategia haloacetamidine covalente ha dimostrato di essere compatibile con scre elevato throughputpiattaforme zare 32,35,36. Descriviamo un test basato sulla fluorescenza facile che misura in modo affidabile l&#39;attività di PAD4. Il test, che mostra un forte rapporto segnale-rumore, velocità di analisi, e la robustezza della misura, ha il potenziale per scoprire un inibitore PAD4 veramente potente e selettivo.

<table border="0" cellpadding="0" cellspacing="0" width="716">
	<tbody>
		<tr height="46">
			<td height="46" style="height:46px;width:192px;">Name of the Material/Equipment</td>
			<td style="width:123px;">Company</td>
			<td style="width:135px;">Catalog Number</td>
			<td style="width:267px;">Comments/ Description</td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:192px;">LB Broth, Miller (LURIA-BERTANI)</td>
			<td style="width:123px;">Amresco</td>
			<td style="width:135px;">J106-2KG</td>
			<td style="width:267px;"><a href="http://www.amresco-inc.com/">http://www.amresco-inc.com</a></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:192px;">Ampicillin Trihydrate (Off-white Powder), Fisher BioReagents</td>
			<td style="width:123px;">Fisher Scientific</td>
			<td>BP902-25&#160;</td>
			<td style="width:267px;"><a href="http://www.fishersci.com/">http://www.fishersci.com</a></td>
		</tr>
		<tr height="68">
			<td height="68" style="height:68px;width:192px;">Isopropylthiagalactonse (IPTG)</td>
			<td style="width:123px;">Life Technogolies</td>
			<td>15529-019</td>
			<td style="width:267px;"><a href="http://www.lifetechnologies.com/">http://www.lifetechnologies.com</a></td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:192px;">All Buffer Salts&#160;</td>
			<td style="width:123px;">Fisher Scientific</td>
			<td style="width:135px;">N/A</td>
			<td style="width:267px;">Can purchase from Fisher Scieintifc; VWR; Acros; Sigma-Aldrich; etc.</td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:192px;">Protino Glutathione (GSH) agarose&#160;</td>
			<td style="width:123px;">Machery-Nagel</td>
			<td style="width:135px;">745500.10</td>
			<td style="width:267px;">Store at 4 &#176;C; http://www.mn-net.com/</td>
		</tr>
		<tr height="71">
			<td height="71" style="height:71px;width:192px;">Z-&#8203;Arg-&#8203;Arg-&#8203;7-&#8203;amido-&#8203;4-&#8203;methylcoumarin hydrochloride (Zcoum)</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td>C5429</td>
			<td style="width:267px;"><a href="http://www.sigmaaldrich.com/">www.sigmaaldrich.com</a></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;width:192px;">Chloroamidine&#160;</td>
			<td style="width:123px;">Cayman Chemical&#160;</td>
			<td style="width:135px;">10599</td>
			<td style="width:267px;">Store at -20 &#176;C; https://www.caymanchem.com/app/template/Home.vm</td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:192px;">Tris(2-&#8203;carboxyethyl)&#8203;phosphine hydrochloride (TCEP HCl)</td>
			<td style="width:123px;">Thermo Scientifc</td>
			<td style="width:135px;">20490</td>
			<td style="width:267px;"><a href="http://www.piercenet.com/">http://www.piercenet.com</a></td>
		</tr>
		<tr height="50">
			<td height="50" style="height:50px;width:192px;">Triton X-100</td>
			<td style="width:123px;">Sigma Aldrich</td>
			<td style="width:135px;">X100-100ML</td>
			<td style="width:267px;"><a href="http://www.sigmaaldrich.com/">www.sigmaaldrich.com</a></td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:192px;">Corning/Nunclon MicroWell plates (96 and 384)</td>
			<td style="width:123px;">N/A</td>
			<td style="width:135px;">N/A</td>
			<td style="width:267px;">Purchase from Corning; Sigma-Aldrich</td>
		</tr>
		<tr height="71">
			<td height="71" style="height:71px;width:192px;">Tecan Infinite 200 / Tecan i-control microplate reader software</td>
			<td style="width:123px;">N/A</td>
			<td style="width:135px;">N/A</td>
			<td style="width:267px;"><a href="http://www.tecan.com/">www.tecan.com</a></td>
		</tr>
		<tr height="65">
			<td height="65" style="height:65px;width:192px;">Europium Ex. 340/40 Em. 475/15 filter</td>
			<td style="width:123px;">N/A</td>
			<td style="width:135px;">N/A</td>
			<td style="width:267px;"><a href="http://www.perkinelmer.com/">http://www.perkinelmer.com</a></td>
		</tr>
	</tbody>
</table>

fluorescence-based monitoring of pad4 activity via a pro-fluorescence substrate analog

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein substrates. The histone tails represent one of the most heavily modified stretches within all human proteins. Peptidyl-arginine deiminase 4 (PAD4) has been shown to convert arginine residues into the non-genetically encoded citrulline residue. Few assays described to date have been operationally facile with satisfactory sensitivity. Thus, the lack of adequate assays has likely contributed to the absence of potent non-covalent PAD4 inhibitors. Herein a novel fluorescence-based assay that allows for the monitoring of PAD4 activity is described. A pro-fluorescent substrate analog was designed to link PAD4 enzymatic activity to fluorescence liberation upon the addition of the protease trypsin. It was shown that the assay is compatible with high-throughput screening conditions and has a strong signal-to-noise ratio. Furthermore, the assay can also be performed with crude cell lysates containing over-expressed PAD4.

Inizialmente, è stato dimostrato che ZRcoum può riferire sull&#39;attività di PAD4 in un formato di piastra da 96 pozzetti. Wells sono stati incubati con il substrato ZRcoum e in presenza / assenza di PAD4. Dopo un periodo di incubazione di 45 min a 37 ° C, la fluorescenza è stata misurata con un 340/40 - 475/15 nm filtro (Figura 2A). Come previsto, i livelli di fluorescenza sono rimasti bassi come fluoroforo entro ZRcoum (o il citrullinato <strong...

Watch this Scientific Journal Video about Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog at JoVE.com

Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog

PAD4 is an enzyme responsible for the conversion of peptidyl-arginine to peptidyl-citrulline. Dysregulation of PAD4 has been implicated in a number of human diseases. A facile and high-throughput compatible fluorescence based PAD4 assay is described.

Basato sulla fluorescenza Monitoraggio dei PAD4 attività tramite un substrato Analog Pro-fluorescenza

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein ...

fluorescence-based-monitoring-pad4-activity-via-pro-fluorescence

Research

JoVE Journal

Chemistry

9.8K Views.  Lehigh University. PAD4 is an enzyme responsible for the conversion of peptidyl-arginine to peptidyl-citrulline. Dysregulation of PAD4 has been implicated in a number of human diseases. A facile and high-throughput compatible fluorescence based PAD4 assay is described.

Video: Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice through their ice-binding surfaces. Fluorescence-based ice plane affinity (FIPA) analysis is a modified technique used to determine the ice planes to which the AFPs bind. FIPA is based on the original ice-etching method for determining AFP-bound ice-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single ice crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound ice hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into ice. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single ice crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to ice to halt its growth and why many AFP-producing organisms express multiple AFP isoforms.

Antifreeze proteins (AFPs) bind to specific planes of ice to prevent or slow ice growth. Fluorescence-based ice plane affinity (FIPA) analysis is a modification of the original ice-etching method for determination of AFP-bound ice planes. AFPs are fluorescently labeled, incorporated into macroscopic single ice crystals, and visualized under UV light.

Determinazione dei piani di legame del ghiaccio delle proteine antigelo mediante affinità del piano di ghiaccio basata sulla fluorescenza

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice ...

Ricerca

Chimica

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

Preparazione Silica Aerogel Monoliti tramite una rapida supercritica metodo di estrazione

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

Monitoraggio in tempo reale delle reazioni eseguita utilizzando la lavorazione a flusso continuo: La preparazione di 3-Acetylcoumarin come un esempio

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Simultaneous Measurement of HDAC1 and HDAC6 Activity in HeLa Cells Using UHPLC-MS

The search for new histone deacetylase (HDAC) inhibitors is of increasing interest in drug discovery. Isoform selectivity has been in the spotlight since the approval of romidepsin, a class I HDAC inhibitor for cancer therapy, and the clinical investigation of HDAC6-specific inhibitors for multiple myeloma. The present method is used to determine the inhibitory activity of test compounds on HDAC1 and HDAC6 in cells. The isoform activity is measured using the ultra-high-performance liquid chromatography &#8211; mass spectrometry (UHPLC-MS) analysis of specific substrates incubated with treated and untreated HeLa cells. The method has the advantage of reflecting the endogenous HDAC activity within the cell environment, in contrast to cell-free biochemical assays conducted on isolated isoforms. Moreover, because it is based on the quantification of synthetic substrates, the method does not require the antibody recognition of endogenous acetylated proteins. It is easily adaptable to several cell lines and an automated process. The method has already proved useful in finding HDAC6-selective compounds in neuroblasts. Representative results are shown here with the standard HDAC inhibitors trichostatin A (non-specific), MS275 (HDAC1-specific), and tubastatin A (HDAC6-specific) using HeLa cells.

The present method serves to identify isoform-specific inhibitors of histone deacetylases (HDAC) in HeLa cells by the UHPLC-MS analysis of multiple substrates. This is an antibody-free method developed to reflect HDAC1 and HDAC6 activity in the living cell environment, in contrast to single-isoform cell-free assays.

Misura simultanea di HDAC1 e HDAC6 attività in HeLa Cells utilizzando UHPLC-MS

The search for new histone deacetylase (HDAC) inhibitors is of increasing interest in drug discovery. Isoform selectivity has been in the spotlight since ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Fabbricazione e collaudo di aerogel catalitico preparato tramite rapida estrazione supercritica

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Sintesi di nanofili Au associato a substrato tramite un meccanismo di crescita superficiale attiva

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

Un protocollo in due fasi per Umpolung funzionalizzazione di chetoni Via Enolonium le specie

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

Sintesi degli esteri tramite un'esterificazione Steglich più verde in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

NMR spectroscopy is often used for the identification and characterization of enzyme inhibitors in drug discovery, particularly in the context of fragment screening. NMR-based activity assays are ideally suited to work at the higher concentrations of test compounds required to detect these weaker inhibitors. The dynamic range and chemical shift dispersion in an NMR experiment can easily resolve resonances from substrate, product, and test compounds. This contrasts with spectrophotometric assays, in which read-out interference problems often arise from compounds with overlapping UV-vis absorption profiles. In addition, since they lack reporter enzymes, the single-enzyme NMR assays are not prone to coupled-assay false positives. This attribute makes them useful as orthogonal assays, complementing traditional high throughput screening assays and benchtop triage assays. Detailed protocols are provided for initial compound assays at 500 &#956;M and 250 &#956;M, dose-response assays for determining IC50 values, detergent counter screen assays, jump-dilution counter screen assays, and assays in E. coli whole cells. The methods are demonstrated using two nucleoside ribohydrolase enzymes. The use of 1H NMR is shown for the purine-specific enzyme, while 19F NMR is shown for the pyrimidine-specific enzyme. The protocols are generally applicable to any enzyme where substrate and product resonances can be observed and distinguished by NMR spectroscopy. To be the most useful in the context of drug discovery, the final concentration of substrate should be no more than 2-3x its Km value. The choice of NMR experiment depends on the enzyme reaction and substrates available as well as available NMR instrumentation.

NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

NMR-based activity assays have been developed to identify and characterize inhibitors of two nucleoside ribohydrolase enzymes. Protocols are provided for initial compound assays at 500 &#956;M and 250 &#956;M, dose-response assays for determining IC50 values, detergent counter screen assays, jump-dilution counter screen assays, and assays in E. coli whole cells.

Assaggi di attività basati su NMR per determinare l'inibizione composta, i valori IC50, l'attività Artifactual e l'attività intera delle cellule

NMR spectroscopy is often used for the identification and characterization of enzyme inhibitors in drug discovery, particularly in the context of fragment ...

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, metal-binding interactions, and conformational shape. Coupling ESI with ion mobility-mass spectrometry (IM-MS) provides an instrumental technique that allows for simultaneous measurement of a peptide&#8217;s mass-to-charge (m/z) and collision cross section (CCS) that relate to its stoichiometry, protonation state, and conformational shape. The overall charge of a peptide complex is controlled by the protonation of 1) the peptide&#8217;s acidic and basic sites and 2) the oxidation state of the metal ion(s). Therefore, the overall charge state of a complex is a function of the pH of the solution that affects the peptides metal ion binding affinity. For ESI-IM-MS analyses, peptide and metal ions solutions are prepared from aqueous-only solutions, with the pH adjusted with dilute aqueous acetic acid or ammonium hydroxide. This allows for pH dependence and metal ion selectivity to be determined for a specific peptide. Furthermore, the m/z and CCS of a peptide complex can be used with B3LYP/LanL2DZ molecular modeling to discern binding sites of the metal ion coordination and tertiary structure of the complex. The results show how ESI-IM-MS can characterize the selective chelating performance of a set of alternative methanobactin peptides and compare them to the copper-binding peptide methanobactin.

Ion mobility-mass spectrometry and molecular modeling techniques can characterize the selective metal chelating performance of designed metal-binding peptides and the copper-binding peptide methanobactin. Developing new classes of metal chelating peptides will help lead to therapeutics for diseases associated with metal ion misbalance.

Tecniche di spettrometria ione Mobilità-Massa per determinare la struttura e i meccanismi del riconoscimento degli ioni metallici e dell'attività di redox degli oligopeptidi di metal linciazione