Name: efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition
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1. Plasmid Construction
<ol>
	<li>Construct an expression plasmid (pBAD-HerFab-L177TAG) that would express the target antibody gene (pBAD-HerFab-WT) with a His6-tag, and replace the codon for Leucine-177 with the amber codon (TAG) 27, using conventional site-directed mutagenesis technique. 
	See Table of Materials.</li>
	<li>Construct another expression plasmid (pEVOL-AFRS) containing the genes for the evolved tRNATyr and aminoacyl-tRNA synthetase (aaRS) pair. Use ...

<ol>
	<li>Wang, L., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expanding+the+genetic+code.">Expanding the genetic code.</a> Angew. Chem. Int. Ed. 44 (1), 34-66 (2004).</li><li>Wu, X., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+at+the+interface+of+chemistry+and+biology.">Synthesis at the interface of chemistry and biology.</a> J. Am. Chem. Soc. 131 (35), 12497-12515 (2009).</li><li>Liu, C. C., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adding+new+chemistries+to+the+genetic+code.">Adding new chemistries to the genetic code.</a> Annu. Rev. Biochem. 79, 413-444 (2010).</li><li>Wang, L., Zhang, Z., Brock, A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Addition+of+the+keto+functional+groupto+the+genetic+code+of+Escherichia+coli.">Addition of the keto functional groupto the genetic code of Escherichia coli.</a> proc. Natl. Acad. Sci. U.S.A. 100 (1), 56-61 (2003).</li><li>Chin, J. W., 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=Addition+of+p-azido-L-phenylalanine+to+the+genetic+code+of+Escherichia+coli.">Addition of p-azido-L-phenylalanine to the genetic code of Escherichia coli.</a> J. Am. Chem. Soc. 124 (31), 9026-9027 (2002).</li><li>Deiters, A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+incorporation+of+an+alkyne+into+proteins+in+Esshcerichia+coli.">In vivo incorporation of an alkyne into proteins in Esshcerichia coli.</a> Bioorg. Med. Chem. Lett. 15 (5), 1521-1524 (2005).</li><li>Plass, T., Milles, S., Koehler, C., Schultz, C., Lemke, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+copper-free+click+chemistry.">Genetically encoded copper-free click chemistry.</a> Angew. Chem. Int. Ed. 50 (17), 3878-3881 (2011).</li><li>Seitchik, J. L., 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=Genetically+encoded+tetrazine+amino+acid+directs+rapid+site-specific+in+vivo+bioorthogonal+ligation+with+transcyclooctenes.">Genetically encoded tetrazine amino acid directs rapid site-specific in vivo bioorthogonal ligation with transcyclooctenes.</a> J. Am. Chem. Soc. 134 (6), 2898-2901 (2014).</li><li>Lee, Y. -. 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+genetically+encoded+acrylamide+fuctionality.">A genetically encoded acrylamide fuctionality.</a> ACS Chem. Biol. 8 (8), 1664-1670 (2013).</li><li>Lang, 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=Genetically+encoded+norbornene+directs+site-specific+cellular+protein+labelling+via+a+rapid+bioorthogonal+raction.">Genetically encoded norbornene directs site-specific cellular protein labelling via a rapid bioorthogonal raction.</a> Nat Chem. 4 (4), 298-304 (2012).</li><li>Lang, 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=Genetic+encoding+of+bicyclononynes+and+trans-cyclooctenes+for+site-specific+protein+labeling+in+vitro+and+in+live+mammalian+cells+via+rapid+fluorogenic+Diels-Alder+reactions.">Genetic encoding of bicyclononynes and trans-cyclooctenes for site-specific protein labeling in vitro and in live mammalian cells via rapid fluorogenic Diels-Alder reactions.</a> J. Am. Chem. Soc. 134 (25), 10317-10320 (2012).</li><li>Jewett, J. C., Sletten, E. M., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+Cu-free+click+chemistry+with+readily+synthesized+biarylazacyclooctynones.">Rapid Cu-free click chemistry with readily synthesized biarylazacyclooctynones.</a> J. Am. Chem. Soc. 132 (11), 3688-3690 (2010).</li><li>Debets, M. F., 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=Azadibenzocyclooctynes+for+fast+and+efficient+enzyme+PEGylation+via+copper-free+(3+++2)+cycloaddition.">Azadibenzocyclooctynes for fast and efficient enzyme PEGylation via copper-free (3 + 2) cycloaddition.</a> Chem. Commun. 46 (1), 97-99 (2010).</li><li>Sletten, E. M., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+mechanism+to+mouse:+a+tale+of+two+bioorthogonal+reactions.">From mechanism to mouse: a tale of two bioorthogonal reactions.</a> Acc. Chem. Res. 44 (9), 666-676 (2011).</li><li>Debets, M. F., 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=Bioconjugation+with+strained+alkenes+and+alkynes.">Bioconjugation with strained alkenes and alkynes.</a> Acc. Chem. Res. 44 (9), 805-815 (2011).</li><li>Mbua, N. E., Guo, J., Wolfert, M. A., Steet, R., Boons, G. -. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain-promoted+alkyne&#8722;azide+cycloadditions+(SPAAC)+reveal+new+features+of+glycoconjugate+biosynthesis.">Strain-promoted alkyne&#8722;azide cycloadditions (SPAAC) reveal new features of glycoconjugate biosynthesis.</a> ChemBioChem. 12 (12), 1912-1921 (2011).</li><li>Kuzmin, A., Poloukhtine, A., Wolfert, M. A., Popik, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+functionalization+using+catalyst-free+azide-alkyne+cycloaddition.">Surface functionalization using catalyst-free azide-alkyne cycloaddition.</a> Bioconjug. Chem. 21 (11), 2076-2085 (2011).</li><li>Yao, J. Z., 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=Fluorophore+targeting+to+cellular+proteins+via+enzymemediated+azide+ligation+and+strain-promoted+cycloaddition.">Fluorophore targeting to cellular proteins via enzymemediated azide ligation and strain-promoted cycloaddition.</a> J. Am. Chem. Soc. 134 (8), 3720-3728 (2012).</li><li>Hao, Z., Hong, S., Chen, X., Chen, 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=Introducing+bioorthogonal+functionalities+into+proteins+in+living+cells.">Introducing bioorthogonal functionalities into proteins in living cells.</a> Acc. Chem. Res. 44 (9), 742-751 (2011).</li><li>Reddington, S. C., Tippmann, E. M., Jones, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Residue+choice+defines+efficiency+and+influence+of+bioorthogonal+protein+modification+via+genetically+encoded+strain+promoted+Click+chemistry.">Residue choice defines efficiency and influence of bioorthogonal protein modification via genetically encoded strain promoted Click chemistry.</a> Chem. Commun. 48 (9), 8419-8421 (2012).</li><li>Chari, R. V. J., Miller, M. L., Widdison, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antibody-drug+conjugates:+an+emerging+concept+in+cancer+therapy.">Antibody-drug conjugates: an emerging concept in cancer therapy.</a> Angew. Chem. Int. Ed. 53 (15), 3751-4005 (2014).</li><li>Tsao, M., Tian, F., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+staudinger+modification+of+proteins+containing+p-Azidophenylalanine.">Selective staudinger modification of proteins containing p-Azidophenylalanine.</a> ChemBioChem. 6 (12), 2147-2149 (2005).</li><li>Brustad, E. M., Lemke, E. A., Schultz, P. G., Deniz, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+general+and+efficient+method+for+the+site-specific+dual-labeling+of+proteins+for+single+molecule+fluorescence+resonance+energy+transfer.">A general and efficient method for the site-specific dual-labeling of proteins for single molecule fluorescence resonance energy transfer.</a> J. Am. Chem. Soc. 130 (52), 17664-17665 (2008).</li><li>Milles, 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=Click+strategies+for+single-molecule+protein+fluorescence.">Click strategies for single-molecule protein fluorescence.</a> J. Am. Chem. Soc. 134 (11), 5187-5195 (2012).</li><li>Jang, S., Sachin, K., Lee, h. J., Kim, D. W., Lee, h. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simple+method+for+protein+conjugation+by+copper-free+click+reaction+and+its+application+to+antibody-free+Western+blot+analysis.">Development of a simple method for protein conjugation by copper-free click reaction and its application to antibody-free Western blot analysis.</a> Bioconjug. Chem. 23 (11), 2256-2261 (2012).</li><li>Kazane, S. 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=Self-assembled+antibody+multimers+through+peptide+nucleic+acid+conjugation.">Self-assembled antibody multimers through peptide nucleic acid conjugation.</a> J. Am. Chem. Soc. 135 (1), 340-346 (2012).</li><li>Ko, W., 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=Efficient+and+site-specific+antibody+labeling+by+strain-promoted+azide-alkyne+cycloaddition.">Efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition.</a> Bull. Korean Chem. Soc. 36 (9), 2352-2354 (2015).</li><li>Young, T. S., Ahmad, I., Yin, J. A., Schultz, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+enhanced+system+for+unnatural+amino+acid+mutagenesis+in+E.+coli.">An enhanced system for unnatural amino acid mutagenesis in E. coli.</a> J. Mol. Biol. 395 (2), 361-374 (2010).</li><li>Bradford, M. 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+rapid+and+sensitive+method+for+the+quantitation+of+microgram+quantities+of+protein+utilizing+the+principle+of+protein-dye+binding.">A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.</a> Anal. Biochem. 72, 248-254 (1976).</li><li>Cho, H. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+the+extracellular+region+of+HER2+alone+and+in+complex+with+the+Herceptin+Fab.">Structure of the extracellular region of HER2 alone and in complex with the Herceptin Fab.</a> Nature. 421 (6924), 756-760 (2003).</li><li>Kolb, H. C., Finn, M. G., Sharpless, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click+chemistry+:+Diverse+chemical+function+from+a+few+good+reactions.">Click chemistry : Diverse chemical function from a few good reactions.</a> Angew. Chem. Int. Ed. 40 (11), 2004-2021 (2001).</li></ol>

The genetic incorporation of unnatural amino acids into proteins has several advantages over other methods used for protein modification. 1-3 One of the important advantages is its general applicability to any kind of protein. In principle, there is no limitation in selecting a target protein and a target site of the protein. However, replacement of a structurally or functionally important residue with a UAA may result in altering the structure and function of the target protein. Generally, residues that are e...

Since the genetic incorporation of p-methoxyphenylalanine in Escherichia coli was reported,1 more than 100 unnatural amino acids (UAAs) have been successfully incorporated into various proteins.1-3 Among these UAAs, the amino acids containing bioorthogonal functional groups have been extensively studied and represent the largest proportion. The bioorthogonal functional groups used in the UAAs include ketone,4 azide,5 alkyne,6 cyclooctyne,7 tetrazine,8 &#945;,&#946;-unsaturated amide,9 norbonene,10 transcyclooctene,11 and bicyclo[6.1.0]-nonyne.11 Although each functional group has its advantages and disadvantages, the azide-containing amino acids have been most extensively used for protein conjugation. p-Azidophenylalanine (AF), one of the azido-containing amino acids, is readily available, and its incorporation efficiency is excellent. Mutant proteins containing this amino acid can be reacted with alkynes by copper-catalyzed cycloaddition or with cyclooctynes by SPAAC.12-20
Recently, biopharmaceuticals have been attracting great attention in the pharmaceutical industry. The antibody-drug conjugate (ADC) is a class of therapeutic antibodies that are advantageous due to their ability for targeted therapy for the treatment of human cancers21 and other diseases. More than 50 ADCs are currently in clinical trials, and the number is rapidly increasing. In development of ADCs, many factors need to be considered to maximize the efficacy and minimize the side effects. Among these factors, an efficient and site-specific conjugation reaction to form a covalent bond between an antibody and a drug is critical. The desired efficiency and specificity in the conjugation reaction can be achieved by conjugation with a bioorthogonal functional group in an unnatural amino acid that is specifically incorporated into an antibody.22-26 Here, we report a protocol to site-specifically incorporate AF into an antibody fragment and conjugate the mutant antibody fragment with a biochemical probe.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1. plasmid Construction</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>plasmid pBAD_HerFab_L177TAG</td>
			<td></td>
			<td></td>
			<td>optionally contain the amber stop codon(TAG) at a desired position. Ko, W. et al. Efficient and Site-Specific Antibody Labeling by Strain-promoted Azide-Alkyne Cycloaddition. BKCS. 36 (9), 2352-2354, doi: 10.1002/bkcs.10423, (2015)</td>
		</tr>
		<tr>
			<td>plasmid pEvol-AFRS</td>
			<td></td>
			<td></td>
			<td>Young, T. S., Ahmad, I., Yin, J. A., and Schultz, P. G. An enhanced system for unnatural amino acid mutagenesis in E. coli. J. Mol. Biol. 395 (2), 361-374, doi: 10.1016/j.jmb.2009.10.030, (2010)</td>
		</tr>
		<tr>
			<td>DH10B</td>
			<td>Invitrogen</td>
			<td>C6400-03</td>
			<td>Expression Host</td>
		</tr>
		<tr>
			<td>Plasmid Mini-prep kit</td>
			<td>Nucleogen</td>
			<td>5112</td>
			<td>200/pack</td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Intron biotechnology</td>
			<td>32034</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>Ethidium bromide</td>
			<td>Alfa Aesar</td>
			<td>L07482</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>LB Broth</td>
			<td>BD Difco</td>
			<td>244620</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>2. Culture preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2.1) Electroporation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro pulser&#160;</td>
			<td>BIO-RAD</td>
			<td>165-2100</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro pulser cuvette</td>
			<td>BIO-RAD</td>
			<td>165-2089</td>
			<td>0.1cm electrode gap, pkg. of 50</td>
		</tr>
		<tr>
			<td>Ampicillin Sodium</td>
			<td>Wako</td>
			<td>018-10372</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Chloramphenicol</td>
			<td>Alfa Aesar</td>
			<td>B20841</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>SAMCHUN</td>
			<td>214230</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>SOC medium</td>
			<td>Sigma</td>
			<td>S1797</td>
			<td>100ML</td>
		</tr>
		<tr>
			<td>3. Expression and purification of HerFab-L177AF</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3.1 Expression of Herfab-L177AF</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>p-azido-L-phenylalanine (AF)</td>
			<td>Bachem</td>
			<td>F-3075.0001</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>L(+)-Arabinose, 99%</td>
			<td>Acros</td>
			<td>104981000</td>
			<td>100g</td>
		</tr>
		<tr>
			<td>Hydrochloric acid, 35~37%</td>
			<td>SAMCHUN</td>
			<td>H0256</td>
			<td>500ml</td>
		</tr>
		<tr>
			<td>3.2 Cell lysis</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tris(hydroxymethyl)aminomethane, 99%</td>
			<td>SAMCHUN</td>
			<td>T1351</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>EDTA disodium salt dihydrate, 99.5%</td>
			<td>SAMCHUN</td>
			<td>E0064</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma</td>
			<td>S9378</td>
			<td>500g</td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Siyaku</td>
			<td>126-0671</td>
			<td>1g</td>
		</tr>
		<tr>
			<td>3.3 Ni-NTA Affinity Chromatography</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ni-NTA resin</td>
			<td>QIAGEN</td>
			<td>30210</td>
			<td>25ml</td>
		</tr>
		<tr>
			<td>Polypropylene column</td>
			<td>QIAGEN</td>
			<td>34924</td>
			<td>50/pack, 1ml capacity</td>
		</tr>
		<tr>
			<td>Imidazole, 99%</td>
			<td>SAMCHUN</td>
			<td>I0578</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sodium phosphate monobasic, 98%</td>
			<td>SAMCHUN</td>
			<td>S0919</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>Sodium Chloride, 99%</td>
			<td>SAMCHUN</td>
			<td>S2907</td>
			<td>1kg</td>
		</tr>
		<tr>
			<td>4. Conjugation of Purified HerFab-L177AF with Alkyne Probes Using Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC)&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cy5.5-ADIBO&#160;</td>
			<td>FutureChem</td>
			<td>FC-6119</td>
			<td>1mg</td>
		</tr>
		<tr>
			<td>5. Purification of Labeled HerFab</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Amicon Ultra 0.5 mL Centrifugal Filters</td>
			<td>MILLIPORE</td>
			<td>UFC500396</td>
			<td>96/pack, 500ul capacity</td>
		</tr>
		<tr>
			<td>6. SDS-PAGE Analysis of Labeled HerFab and Fluorescent Gel Scanning</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-Dithio-DL-threitol, DTT, 99.5 %</td>
			<td>Sigma</td>
			<td>10708984001</td>
			<td>10g</td>
		</tr>
		<tr>
			<td>NuPAGE LDS Sample Buffer, 4X</td>
			<td>Thermofisher</td>
			<td>NP0007</td>
			<td>10ml</td>
		</tr>
		<tr>
			<td>MES running buffer</td>
			<td>Thermofisher</td>
			<td>NP0002</td>
			<td>500ml</td>
		</tr>
		<tr>
			<td>Nupage Novex 4-12% SDS PAGE gels</td>
			<td>Thermofisher</td>
			<td>NO0321</td>
			<td>12well</td>
		</tr>
		<tr>
			<td>Coomassie Brilliant Blue R-250</td>
			<td>Wako</td>
			<td>031-17922</td>
			<td>25g</td>
		</tr>
		<tr>
			<td>Typhoon 9210 variable mode imager</td>
			<td>Amersham Biosciences</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

efficient and site-specific antibody labeling by strain-promoted azide-alkyne cycloaddition

There are currently many chemical tools available to introduce chemical probes into proteins to study their structure and function. A useful method is protein conjugation by genetically introducing an unnatural amino acid containing a bioorthogonal functional group. This report describes a detailed protocol for site-specific antibody conjugation. The protocol includes experimental details for the genetic incorporation of an azide-containing amino acid, and the conjugation reaction by strain-promoted azide-alkyne cycloaddition (SPAAC). This strain-promoted reaction proceeds by simple mixing of the reacting molecules at physiological pH and temperature, and does not require additional reagents such as copper(I) ions and copper-chelating ligands. Therefore, this method would be useful for general protein conjugation and development of antibody drug conjugates (ADCs).

In this study, an antibody fragment was site-specifically conjugated with a fluorophore by incorporating an azide-containing amino acid into the fragment and reacting the mutant antibody fragment with a strained cyclooctyne (Figure 1). HerFab was selected as the target antibody fragment into which AF was incorporated as an azide-containing amino acid. To choose the residue in HerFab for the replacement with AF, the X-ray crystal structure of HerFab was analyzed. 30 <...

Watch this Scientific Journal Video about Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition at JoVE.com

Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition

Here, we present a protocol to site-specifically introduce chemical probes into an antibody fragment by genetically incorporating an azide-containing amino acid, and subsequently coupling the azide with a chemical probe by strain-promoted azide-alkyne cycloaddition (SPAAC).

There are currently many chemical tools available to introduce chemical probes into proteins to study their structure and function. A useful method is ...

The overall goal of this procedure is to site-specifically introduce chemical probes into an antibody fragment by genetically incorporating an azide-containing amino acid. This method can help answer key questions in the chemical biology field such as in protein modification, engineering and conjugation. The main advantage of this technique is that your target probe or broth can be site-specifically introduced into proteins or antibodies by simple mixing.After constructing the plasmids, add one microliter of each to 20 microliters of E.Coli strain DH10-beta at a concentration of two times 10 to the eight cells per microliter to a 1.5 milliliter centrifuge tube. Use a pipette to gently mix the solution. Then place 20 microliters of the mixed solution into a clean cuvette.Set the electroporation machine to 25 microfarads and 2.5 kilovolts. Then insert the cuvette into the slide of the shocking chamber. Push the slide into the chamber until the cuvette makes firm contact with the chamber electrodes.Press the pulse button once until the electroporation machine beeps. After this, add one milliliter SOC medium to the cuvette quickly. Then transfer the mixture to a test tube.Incubate with shaking at 37 degrees Celsius for one hour. After incubation is complete, spread the transformed E.Coli cells onto lysogeny broth agar plates containing appropriate antibiotics. Incubate the plates at 37 degrees Celsius for 12 hours.After the plate incubation is complete, inoculate a single transformed colony in five milliliters of LB medium containing antibiotics. Incubate with shaking for 12 hours at 37 degrees Celsius. Then transfer the primary culture into 200 milliliters of LB medium with 100 micrograms per milliliter ampicillin and one millimolar AF.Incubate with shaking at 37 degrees Celsius for at least three hours.Add two milliliters of 1.6 molar arabinose when the culture reaches an optical density of 0.8 at 550 nanometers. Then incubate with shaking at 30 degrees Celsius for 12 hours. When the incubation is complete, harvest the cells by centrifugation at 11, 000 times g for five minutes.Discard the supernatant and freeze the pellet at negative 20 degrees Celsius. When ready to lyse the cells, re-suspend the pellet in 20 milliliters of paraplasmic lysis buffer in a fresh centrifuge tube. Incubate the mixture at 37 degrees Celsius for one hour.Next, centrifuge the cell lysate at 18, 000 times g for 15 minutes at four degrees Celsius. Transfer the supernatant to a fresh tube and discard the pellet. Then add 400 microliters of an Ni-NTA resin suspension.Using a rotator, gently agitate the tube for one hour at four degrees Celsius. After mixing is complete, pour the suspension into a polypropylene column. Wash the resin three times with five milliliters of wash buffer.Elute the target antibody with 300 microliters of elution buffer. After this, determine the concentration of the mutant protein as outlined in the text protocol. Begin by adding 10 microliters of a 10 micromolar solution of HerFab-L177AF in phosphate buffer containing 10 millimolar sodium phosphate dibasic and 100 millimolar sodium chloride to a fresh centrifuge tube.Then add 20 microliters of a 200 micromolar solution of Cy 5.5 azadibenzocyclooctyne in water. After this, cover the reaction vessel with aluminum foil. Allow the stain-promoted cyclo-edition reaction to proceed for six hours at 37 degrees Celsius.Once the reaction is complete, add 30 microliters of sample and 450 microliters of phosphate buffer to wash free Cy 5.5 dye in a centrifugal filter spin column. Centrifuge the spin column at 14, 000 times g for 15 minutes at four degrees Celsius. Discard the flow-through and then transfer the purified sample to a 1.5 milliliter microcentrifuge tube.Store the purified labeled HerFab at four degrees Celsius unless ready for analysis. Begin by adding 13 microliters of 7.8 micromolar purified HerFab to a fresh tube. Then add five microliters of LDS protein sample buffer.Incubate the mixture at 95 degrees Celsius for 10 minutes. After incubation, attach the four to 12%Bis-Tris SDS-PAGE gel cassette to the electrophoresis cell. Add running buffer.Next, load the conjugated protein samples in the pre-stained molecular weight maker. Perform gel electrophoresis for 35 minutes at 200 volts. After the electrophoresis is complete, transfer the gel to a gel documentation and analysis system.Scan for Cy 5.5 and then stain the gel with a commercial protein stain. In this study, the antibody fragment Her-Fab is site-specifically conjugated with a This is accomplished by incorporating an azide-containing amino acid into the fragment and then reacting the mutant antibody fragment with a strained cyclooctyne. SDS-PAGE analysis is performed for mutant proteins expressed both with and without the azide-containing amino acid.As can be seen, the full-length antibody fragment was obtained only in the presence of the amino acid. The antibody containing the amino acid is evaluated for conjugation via reaction with a Cy 5.5 linked azadibenzocyclooctyne derivative Cy 5.5 and analyzed by SDS-PAGE. The fluorescence images show conjugation of the mutant antibody fragment with Cy 5.5 while no conjugation was observed in the control.Once properly expressed and purify your protein with acetylphenylalanine, the protein can be efficiently labeled with a probe with the strain Because the labeling reaction requires no additional reagent, you can introduce the probe into your target protein by simply mixing the probe with your protein. After watching this video, you should have a good understanding of how to site-specifically introduce chemical probe into an antibody fragment by genetically incorporating an azide-containing amino acid.

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