Name: synthesis and structure determination of &#181;-conotoxin piiia isomers with different disulfide connectivities
Uploaded: 2018-10-02T14:00:00
Description: Watch this Scientific Journal Video about Synthesis and Structure Determination of Ã‚Âµ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities at JoVE.com

We would like to thank A. Resemann, F. J. Mayer, and D. Suckau from Bruker Daltonics GmbH Bremen; D. Tietze, A. A. Tietze, V. Schmidts and C. Thiele from the Darmstadt University of Technology; O. Ohlenschl&#228;ger from the FLI Jena, M. Engeser from the University of Bonn; K. Kramer, A. Harzen, and H. Nakagami from the Max Planck Institute for Plant Breeding Research, Cologne; Susanne Neupert from the Institute for Zoology, Cologne; and the Biomolecular Magnetic Resonance Spectroscopy Facilities of the University of Frankfurt for technical support, training modules, and access to instruments. Financial support by the University of Bonn to D.I. is gratefully acknowledged.

Note: All amino acids used herein were in the L-configuration. The abbreviations of amino acids and amino acid derivatives were used according to the recommendations of the Nomenclature Committee of IUB and the IUPAC-IUB Joint Commission on Biochemical Nomenclature.
1. Solid-Phase Peptide Synthesis (SPPS)
NOTE: Carry out the synthesis with a solid-phase peptide synthesizer. Perform the synthesis of the linear peptide precursors of the general sequence ZRLCCGFOKSCRSRQC...

<ol>
	<li>Fosgerau, K., Hoffmann, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peptide+therapeutics:+Current+status+and+future+directions.">Peptide therapeutics: Current status and future directions.</a> Drug Discovery Today. 20 (1), 122-128 (2015).</li><li>Gongora-Ben&#237;tez, M., Tulla-Puche, J., Albericio, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifaceted+roles+of+disulfide+bonds.+peptides+as+therapeutics.">Multifaceted roles of disulfide bonds. peptides as therapeutics.</a> Chemical Reviews. 114 (2), 901-926 (2014).</li><li>Tietze, A. 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=Structurally+diverse+&#181;-conotoxin+PIIIA+isomers+block+sodium+channel+NaV1.4.">Structurally diverse &#181;-conotoxin PIIIA isomers block sodium channel NaV1.4.</a> Angewandte Chemie - International Edition. 51 (17), 4058-4061 (2012).</li><li>Carstens, B. 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=Structure-Activity+Studies+of+Cysteine-Rich+&#945;-Conotoxins+that+Inhibit+High-Voltage-Activated+Calcium+Channels+via+GABABReceptor+Activation+Reveal+a+Minimal+Functional+Motif.">Structure-Activity Studies of Cysteine-Rich &#945;-Conotoxins that Inhibit High-Voltage-Activated Calcium Channels via GABABReceptor Activation Reveal a Minimal Functional Motif.</a> Angewandte Chemie - International Edition. 55 (15), 4692-4696 (2016).</li><li>Zhang, Y., Schulten, K., Gruebele, M., Bansal, P. S., Wilson, D., Daly, N. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disulfide+bridges:+Bringing+together+frustrated+structure+in+a+bioactive+peptide.">Disulfide bridges: Bringing together frustrated structure in a bioactive peptide.</a> Biophysical Journal. 110 (8), 1744-1752 (2016).</li><li>Nielsen, K. 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=Solution+structure+of+&#181;-conotoxin+PIIIA,+a+preferential+inhibitor+of+persistent+tetrodotoxin-sensitive+sodium+channels.">Solution structure of &#181;-conotoxin PIIIA, a preferential inhibitor of persistent tetrodotoxin-sensitive sodium channels.</a> Journal of Biological Chemistry. 277 (30), 27247-27255 (2002).</li><li>Heimer, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conformational+&#181;-Conotoxin+PIIIA+Isomers+Revisited:+Impact+of+Cysteine+Pairing+on+Disulfide-Bond+Assignment+and+Structure+Elucidation.">Conformational &#181;-Conotoxin PIIIA Isomers Revisited: Impact of Cysteine Pairing on Disulfide-Bond Assignment and Structure Elucidation.</a> Analytical Chemistry. 90 (5), 3321-3327 (2018).</li><li>Chang, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diverse+pathways+of+oxidative+folding+of+disulfide+proteins:+Underlying+causes+and+folding+models.">Diverse pathways of oxidative folding of disulfide proteins: Underlying causes and folding models.</a> Biochemistry. 50 (17), 3414-3431 (2011).</li><li>B&#246;hm, 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=Novel+insights+into+structure+and+function+of+factor+XIIIa-inhibitor+tridegin.">Novel insights into structure and function of factor XIIIa-inhibitor tridegin.</a> Journal of Medicinal Chemistry. 57 (24), 10355-10365 (2014).</li><li>Postma, T. M., Albericio, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disulfide+Formation+Strategies+in+Peptide+Synthesis.">Disulfide Formation Strategies in Peptide Synthesis.</a> European Journal of Organic Chemistry. 2014 (17), 3519-3530 (2014).</li><li>Albericio, F., Isidro-llobet, A., Mercedes, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amino+Acid-Protecting+Groups.">Amino Acid-Protecting Groups.</a> Chemical Reviews. 109 (6), 2455-2504 (2009).</li><li>Annis, I., Hargittai, B., Barany, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disulfide+bond+formation+in+peptides.">Disulfide bond formation in peptides.</a> Methods in Enzymology. 289 (1988), 198-221 (1997).</li><li>Kamber, 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=The+Synthesis+of+Cystine+Peptides+by+Iodine+Oxidation+of+S-Trityl-cysteine+and+S-Acetamidomethyl-cysteine+Peptides.">The Synthesis of Cystine Peptides by Iodine Oxidation of S-Trityl-cysteine and S-Acetamidomethyl-cysteine Peptides.</a> Helvetica Chimica Acta. 63 (4), 899-915 (1980).</li><li>Bosch, D. E., Zielinski, T., Lowery, R. G., Siderovski, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+Modulators+of+Regulator+of+G-Protein+Signaling+(RGS)+Proteins.">Evaluating Modulators of Regulator of G-Protein Signaling (RGS) Proteins.</a> Current Protocols in Pharmacology. 56 (2.8), 1-15 (2012).</li><li>Mochizuki, M., Tsuda, S., Tanimura, K., Nishiuchi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regioselective+formation+of+multiple+disulfide+bonds+with+the+aid+of+postsynthetic+S-tritylation.">Regioselective formation of multiple disulfide bonds with the aid of postsynthetic S-tritylation.</a> Organic Letters. 17 (9), 2202-2205 (2015).</li><li>Peigneur, 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=&#948;-conotoxins+synthesized+using+an+acid-cleavable+solubility+tag+approach+reveal+key+structural+determinants+for+NaV+subtype+selectivity.">&#948;-conotoxins synthesized using an acid-cleavable solubility tag approach reveal key structural determinants for NaV subtype selectivity.</a> Journal of Biological Chemistry. 289 (51), 35341-35350 (2014).</li><li>Heimer, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+Room-Temperature+Aprotic+and+Protic+Ionic+Liquids+for+Oxidative+Folding+of+Cysteine-Rich+Peptides.">Application of Room-Temperature Aprotic and Protic Ionic Liquids for Oxidative Folding of Cysteine-Rich Peptides.</a> ChemBioChem. 15 (18), 2754-2765 (2014).</li><li>Kates, S. A., Albericio, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Solid-Phase Synthesis: A Practical Guide. , (2000).</li><li>W&#252;thrich, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMR+studies+of+structure+and+function+of+biological+macromolecules+(Nobel+lecture).">NMR studies of structure and function of biological macromolecules (Nobel lecture).</a> Angewandte Chemie - International Edition. 42 (29), 3340-3363 (2003).</li></ol>

The method described herein for the synthesis of cysteine-rich peptides such as &#181;-PIIIA represents a possibility to selectively produce disulfide-bonded isomers from the same amino acid sequence. Therefore, established methods such as Fmoc-based solid phase peptide synthesis18 and a defined protecting group strategy for the regioselective formation of disulfide bonds were used16. The solid-phase peptide synthesis can produce amino acid sequences on a polymer support (r...

The use of bioactive peptides in pharmaceutical research and development is highly recognized, because they represent potent and highly selective compounds for specific biological targets1. For their bioactivity, however, the three-dimensional structure is of great importance in order to perform structure-activity relationship studies2,3,4. Apart from the primary amino acid sequence that influences the overall conformation, disulfide bonds significantly stabilize the structure of cysteine-rich peptides5. Multiple disulfide-bridged peptides include conotoxins such as &#181;-PIIIA from Conus purpurascens which contains six cysteines in its sequence. This high cysteine content theoretically allows the formation of 15 disulfide isomers. The correct disulfide connectivity is very important for the biological activity6,7. However, the question that arises is whether there is more than one bioactive conformation of naturally occurring peptides and if so, which of those isomers possesses the highest biological activity? In the case of &#181;-conotoxins, the biological targets are voltage-gated sodium ion channels, and &#181;-PIIIA in particular is most potent for subtypes NaV1.2, NaV1.4 and NaV1.73.
The synthesis of disulfide-bridged peptides can be achieved using various methods. The most convenient method for the formation of disulfide bonds within a peptide is the so-called oxidative self-folding approach. Here, the linear precursor of the desired cyclic peptide is synthesized first using solid-phase peptide synthesis, which is after the cleavage from the polymeric support subjected to oxidation in a buffer system. Redox-active agents such as reduced and oxidized glutathione (GSH/GSSG) are often added to promote the formation of the disulfide bonds. The main disadvantage of buffer-supported self-folding is that the disulfide bonds are not formed selectively in a stepwise fashion. Compared to the native peptide, for which often only one specific disulfide isomer is described, it is possible to obtain numerous other isomers with this approach8. &#181;-PIIIA has already been shown to result in at least three differently folded isomers upon self-folding in a previous study3. The separation of such an isomer mixture is rather difficult due to similar retention times if using chromatographic purification methods9. The targeted synthesis of a specific isomer is therefore advantageous. To specifically produce an isomer with defined disulfide connectivity, a special strategy is required in which the disulfide bonds are successively closed. Therefore, the linear precursor carrying distinct protecting groups at the individual cysteine pairs is synthesized on the polymer support. After the elimination, the cysteine pairs are individually and successively deprotected and linked in an oxidation reaction to yield the desired disulfide bonds10,11,12,13,14,15,16. After the synthesis and the purification of the reaction product, it is required to confirm the identity and the disulfide connectivity by suitable analytical methods. Numerous analytical methods are available for the elucidation of the primary amino acid sequence, e.g., MS/MS, while the determination of the disulfide connectivity still remains much less investigated. Apart from the complexity of such multiple disulfide-bonded peptides, product-related impurities (e.g., from disulfide scrambling), due to sample preparation and work-up can further complicate analysis. In this paper, we show that the use of a combination of different analytical techniques is necessary to unequivocally clarify the identity of the disulfide bonds in the &#181;-PIIIA isomers. We have combined chromatographic methods with mass spectrometry and provided the same samples to NMR spectroscopy. In matrix-assisted laser desorption/ionization(MALDI) MS/MS analysis, we identified the disulfide bonds by using partial reduction and iodoacetamide derivatization because top-down analysis is not possible for this peptide. 2D NMR experiments were performed in order to obtain a three-dimensional structure of each isomer. Thus, by combining distinct sophisticated analytical methods, it is possible to elucidate properly the disulfide connectivity and three-dimensional structure of complex multiple disulfide-bonded peptides7.

<table border="0" cellpadding="0" cellspacing="0" style="width:979px;" width="979">
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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Fmoc Rink amide resin</td>
			<td style="width:185px;">Novabiochem</td>
			<td style="width:191px;">855001</td>
			<td style="width:263px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Pyr(Boc)</td>
			<td style="width:185px;">Bachem</td>
			<td style="width:191px;">A-3850</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Arg(Pbf)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSC1010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Asn(Trt)</td>
			<td style="width:185px;">Bachem</td>
			<td style="width:191px;">B-1785</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Asp(tBu)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSP1020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Hyp(tBu)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FAA1627</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Lys(Boc)</td>
			<td style="width:185px;">Bachem</td>
			<td style="width:191px;">B-1080</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Ser(tBu)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSC1190</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Gln(Trt)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSC1043</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Glu(tBu)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSP1045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Trp(Boc)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSC1225</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Tyr(tBu)</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">47623</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Thr(tBu)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FSP1210</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">His(Trt)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FDP1200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-(1H-Benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorphosphat</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">8510060</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">DMF</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:191px;">D119</td>
			<td>Flammable, Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">DCM</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td>D37</td>
			<td>Carcinogenic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Piperidine</td>
			<td style="width:185px;">Alfa Aesar</td>
			<td>A12442</td>
			<td>Flammable, Toxic, Corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">N-Methyl-Morpholin</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">224286</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Cys(Acm)</td>
			<td style="width:185px;">Iris Biotech</td>
			<td style="width:191px;">FAA1506</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Cys(Trt)</td>
			<td style="width:185px;">Bachem</td>
			<td style="width:191px;">E-2495</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Cys(tBu)</td>
			<td style="width:185px;">Bachem</td>
			<td style="width:191px;">B-1220</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">trifluoruacetic acid</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">74564</td>
			<td>Toxic, Corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">phenol</td>
			<td style="width:185px;">Merck</td>
			<td style="width:191px;">1002060</td>
			<td>Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">thioanisol</td>
			<td style="width:185px;">Alfa Aesar</td>
			<td style="width:191px;">A14846</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">ethanedithiol</td>
			<td style="width:185px;">Fluka Analytical</td>
			<td style="width:191px;">2390</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">diethyl ether</td>
			<td style="width:185px;">VWR</td>
			<td style="width:191px;">100,921</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">tert-butanol</td>
			<td style="width:185px;">Alfa Aesar</td>
			<td style="width:191px;">L12338</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">acetonitrile</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:191px;">A998</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">water</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:191px;">W5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">isopropanol</td>
			<td style="width:185px;">VWR</td>
			<td style="width:191px;">ACRO42383</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">sodium hydroxide</td>
			<td style="width:185px;">AppliChem</td>
			<td style="width:191px;">A6579,1000</td>
			<td>Corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">iodoacetamide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">I6125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">iodine</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">I0385</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Hydrochloric acid</td>
			<td style="width:185px;">Merck</td>
			<td style="width:191px;">110165</td>
			<td>Corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">ascorbic acid</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">A4403</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">diphenylsulfoxide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">P35405</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">anisol</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">96109</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">trichloromethylsilane</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">M85301</td>
			<td>Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">sample dilution buffer</td>
			<td style="width:185px;">Laborservice Onken</td>
			<td style="width:191px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">sodium dihydrogen phosphate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">106370</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">disodium hydrogen phosphate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">795410</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">(2-carboxyethyl)phosphine hydrochloride</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">C4706</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">citric acid</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">251275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">sodium citrate dihydrate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">W302600</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">tris-acetate</td>
			<td style="width:185px;">Carl Roth,&#160;</td>
			<td style="width:191px;">7125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Ethylenediaminetetraacetic acid</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:191px;">E26282&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">peptide calibration standard II</td>
			<td style="width:185px;">Bruker Daltonics GmbH</td>
			<td style="width:191px;">8222570</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;"></td>
			<td style="width:185px;"></td>
			<td style="width:191px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Name of Equipment</td>
			<td style="width:185px;">Company</td>
			<td style="width:191px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">solid-phase peptide synthesizer</td>
			<td>Intavis Bioanalytical Instruments AG</td>
			<td style="width:191px;">EPS 221</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:340px;">lyophilizer&#160;</td>
			<td>Martin Christ GmbH</td>
			<td style="width:191px;">&#160;Alpha 1-2 Ldplus</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:340px;">semipreparative HPLC</td>
			<td>Jasco</td>
			<td style="width:191px;">system PV-987</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Eurospher 100 C18 column (RP, 5 &#181;m particle size, 100 &#197; pore size, 250 x 32 mm)</td>
			<td style="width:185px;">Knauer</td>
			<td style="width:191px;">25QE181E2J</td>
			<td>purification of the linear peptide</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:340px;">Vydac 218TP1022 column (RP C18, 10 &#181;m particle size, 300 &#197; pore size, 250 x 22 mm)</td>
			<td>Hichrom-VWR</td>
			<td style="width:191px;">HICH218TP1022</td>
			<td>purification of the oxidized peptide</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:340px;">analytical HPLC&#160;</td>
			<td>Shimadzu</td>
			<td style="width:191px;">system LC-20AD</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Vydac 218TP54 column (C18 RP, 5 &#181;m particle size, 300 &#197; pore size, 250 x 4.6 mm)&#160;</td>
			<td>Hichrom-VWR</td>
			<td style="width:191px;">HICH218TP54</td>
			<td>analytical column</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">ground steel target (MTP 384)</td>
			<td>Bruker Daltonics GmbH</td>
			<td style="width:191px;">NC0910436</td>
			<td>MALDI preparation&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">C18-concentration filter (ZipTip)</td>
			<td style="width:185px;">Merck KGaA</td>
			<td style="width:191px;">ZTC18S096</td>
			<td>MALDI preparation&#160;</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">MALDI mass spectrometer</td>
			<td style="width:185px;">Bruker Daltonics GmbH</td>
			<td style="width:191px;">ultraflex III TOF/TOF</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">amino acid analyzer</td>
			<td>Eppendorf-Biotronik GmbH</td>
			<td style="width:191px;">LC 3000 system</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">NMR spectrometer Bruker Avance III</td>
			<td>Bruker Daltonics GmbH</td>
			<td style="width:191px;">Bruker Avance III 600 MHz</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">computer program for molecular visualising</td>
			<td>YASARA Biosciences GmbH</td>
			<td style="width:191px;">Yasara structures</td>
			<td>NMR structure calculation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">computer program for MALDI data evaluation&#160;</td>
			<td>Bruker Daltonics GmbH</td>
			<td style="width:191px;">flexAnalysis, BioTools</td>
			<td>MS/MS fragmentation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">analog vortex mixer</td>
			<td>VWR</td>
			<td style="width:191px;">VM 3000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Microcentrifuge</td>
			<td>Eppendorf</td>
			<td style="width:191px;">5410</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Centrifuge</td>
			<td>Hettich</td>
			<td style="width:191px;">EBA 20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Rotational vacuum concentrator</td>
			<td style="width:185px;">Christ</td>
			<td style="width:191px;">2-18 Cdplus</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:340px;">Analytical Balance</td>
			<td style="width:185px;">A&#38;D Instruments</td>
			<td style="width:191px;">GR-202-EC</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis and structure determination of &#181;-conotoxin piiia isomers with different disulfide connectivities

Peptides with a high number of cysteines are usually influenced regarding the three-dimensional structure by their disulfide connectivity. It is thus highly important to avoid undesired disulfide bond formation during peptide synthesis, because it may result in a completely different peptide structure, and consequently altered bioactivity. However, the correct formation of multiple disulfide bonds in a peptide is difficult to obtain by using standard self-folding methods such as conventional buffer oxidation protocols, because several disulfide connectivities can be formed. This protocol represents an advanced strategy required for the targeted synthesis of multiple disulfide-bridged peptides which cannot be synthesized via buffer oxidation in high quality and quantity. The study demonstrates the application of a distinct protecting group strategy for the synthesis of all possible 3-disulfide-bonded peptide isomers of &#181;-conotoxin PIIIA in a targeted way. The peptides are prepared by Fmoc-based solid phase peptide synthesis using a protecting group strategy for defined disulfide bond formation. The respective pairs of cysteines are protected with trityl (Trt), acetamidomethyl (Acm), and tert-butyl (tBu) protecting groups to make sure that during every oxidation step only the required cysteines are deprotected and linked. In addition to the targeted synthesis, a combination of several analytical methods is used to clarify the correct folding and generation of the desired peptide structures. The comparison of the different 3-disulfide-bonded isomers indicates the importance of accurate determination and knowledge of the disulfide connectivity for the calculation of the three-dimensional structure and for interpretation of the biological activity of the peptide isomers. The analytical characterization includes the exact disulfide bond elucidation via tandem mass spectrometry (MS/MS) analysis which is performed with partially reduced and alkylated derivatives of the intact peptide isomer produced by an adapted protocol. Furthermore, the peptide structures are determined using 2D nuclear magnetic resonance (NMR) experiments and the knowledge obtained from MS/MS analysis.

15 different disulfide-bridged isomers of the &#181;-conotoxin PIIIA are synthesized and characterized in detail (Figure 1). Disulfide bonds are identified by partial reduction and subsequent MS/MS analysis (Figure 2). NMR analysis of the different isomers is carried out (Figure 3) to reveal the individual peptide structures. Notably, a combination of RP HPLC, MS/MS fragmentation, and NMR analysis is...

Watch this Scientific Journal Video about Synthesis and Structure Determination of Ã‚Âµ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities at JoVE.com

Synthesis and Structure Determination of ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Âµ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities

Cysteine-rich peptides fold into distinct three-dimensional structures depending on their disulfide connectivity. Targeted synthesis of individual disulfide isomers is required when buffer oxidation does not lead to the desired disulfide connectivity. The protocol deals with the selective synthesis of 3-disulfide-bonded peptides and their structural analysis using NMR and MS/MS studies.

Synthesis and Structure Determination of &#181;-Conotoxin PIIIA Isomers with Different Disulfide Connectivities

Peptides with a high number of cysteines are usually influenced regarding the three-dimensional structure by their disulfide connectivity. It is thus ...

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