This work was supported by grants AG027818 and AG030709 from NIH/NIA, 2005/2E from the Larry L. Hillblom Foundation, IIRG-07-58334 from the Alzheimer Association, and 07-65798 from California Department of Public Health.

1. Peptide preparation
<ol>
<li>Weigh out ~100&ndash;200 &mu;g of lyophilized peptide using a microbalance and transfer into labeled, silicon-coated, low-adsorbent microfuge tubes. Here, we use the human sequences of A&beta;40, A&beta;42, calcitonin, and GRF.</li>
<li>Here, we use peptides pre-treated with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) to obtain homogeneous, aggregate-free preparations. This step is necessary because pre-formed aggregates induce rapid aggregation of amyloidogenic proteins, which result in po...

<ol>
	<li>Bitan, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+study+of+metastable+amyloidogenic+protein+oligomers+by+photo-induced+cross-linking+of+unmodified+proteins.">Structural study of metastable amyloidogenic protein oligomers by photo-induced cross-linking of unmodified proteins.</a> Methods Enzymol. 413, 217-236 (2006).</li><li>Fancy, D. A., Kodadek, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemistry+for+the+analysis+of+protein-protein+interactions:+rapid+and+efficient+cross-linking+triggered+by+long+wavelength+light.">Chemistry for the analysis of protein-protein interactions: rapid and efficient cross-linking triggered by long wavelength light.</a> Proc. Natl. Acad. Sci. USA. 96, 6020-6024 (1999).</li><li>Kluger, R., Alagic, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+cross-linking+and+protein-protein+interactions&#8212;a+review+with+illustrative+protocols.">Chemical cross-linking and protein-protein interactions&#8212;a review with illustrative protocols.</a> Bioorg. Chem. 32, 451-472 (2004).</li><li>Tomohiro, T., Hashimoto, M., Hatanaka, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cross-linking+chemistry+and+biology:+development+of+multifunctional+photoaffinity+probes.">Cross-linking chemistry and biology: development of multifunctional photoaffinity probes.</a> Chem. Rec. 5, 385-395 (2005).</li><li>Bitan, G., Fradinger, E. A., Spring, S. M., Teplow, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurotoxic+protein+oligomers&#8212;what+you+see+is+not+always+what+you+get.">Neurotoxic protein oligomers&#8212;what you see is not always what you get.</a> Amyloid. 12, 88-95 (2005).</li><li>Bitan, G., Teplow, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+aggregate-free,+low+molecular+weight+amyloid-&#946;+for+assembly+and+toxicity+assays.">Preparation of aggregate-free, low molecular weight amyloid-&#946; for assembly and toxicity assays.</a> Methods Mol. Biol. 299, 3-9 (2005).</li><li>Bitan, G., Lomakin, A., Teplow, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amyloid+&#946;-protein+oligomerization:+prenucleation+interactions+revealed+by+photo-induced+cross-linking+of+unmodified+proteins.">Amyloid &#946;-protein oligomerization: prenucleation interactions revealed by photo-induced cross-linking of unmodified proteins.</a> J. Biol. Chem. 276, 35176-35184 (2001).</li><li>Bitan, G., Kirkitadze, M. D., Lomakin, A., Vollers, S. S., Benedek, G. B., Teplow, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amyloid+&#946;-protein+(A&#946;)+assembly:+A&#946;40+and+A&#946;42+oligomerize+through+distinct+pathways.">Amyloid &#946;-protein (A&#946;) assembly: A&#946;40 and A&#946;42 oligomerize through distinct pathways.</a> Proc. Natl. Acad. Sci. USA. 100, 330-335 (2003).</li><li>Hepler, R. W., Grimm, K. M., Nahas, D. D., Breese, R., Dodson, E. C., Acton, P., Keller, P. M., Yeager, M., Wang, H., Shughrue, P., Kinney, G., Joyce, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solution+state+characterization+of+amyloid+&#946;-derived+diffusible+ligands.">Solution state characterization of amyloid &#946;-derived diffusible ligands.</a> Biochemistry (Mosc). 45, 15157-15167 (2006).</li><li>Bitan, G., Teplow, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+photochemical+cross-linking&#8212;a+new+tool+for+studies+of+metastable,+amyloidogenic+protein+assemblies).">Rapid photochemical cross-linking&#8212;a new tool for studies of metastable, amyloidogenic protein assemblies).</a> Acc. Chem. Res. 37, 357-364 (2004).</li><li>Piening, N., Weber, P., Hogen, T., Beekes, M., Kretzschmar, H., Giese, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photo-induced+crosslinking+of+prion+protein+oligomers+and+prions.">Photo-induced crosslinking of prion protein oligomers and prions.</a> Amyloid. 13, 67-77 (2006).</li><li>Li, H. T., Lin, X. J., Xie, Y. Y., Hu, H. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+early+events+of+&#945;-synuclein+oligomerization+revealed+by+photo-induced+cross-linking.">The early events of &#945;-synuclein oligomerization revealed by photo-induced cross-linking.</a> Protein Pept. Lett. 13, 385-390 (2006).</li><li>Vollers, S. S., Teplow, D. B., Bitan, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+Peptide+oligomerization+state+using+rapid+photochemical+crosslinking.">Determination of Peptide oligomerization state using rapid photochemical crosslinking.</a> Methods Mol. Biol. 299, 11-18 (2005).</li></ol>

PICUP was developed originally to study stable protein complexes2. The method was applied later to quantitative study of metastable amyloid protein assemblies, including A&beta;10, prion and disease-associated PrPSc 11, and &alpha;-synuclein12. The most important factors that must be considered when designing a PICUP experiment are the reagent stoichiometry, irradiation time, and sample preparation procedure. The former two issues may require empirical optimization, whereas the...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Dolan-Jenner 200-W incandescent lamp</td>
<td>Other</td>
<td>Dolan-Jenner Industries</td>
<td>Model 170-D</td>
<td>The heat generated by the lamp does not affect samples for short incubation periods.</td>
</tr>
<tr>
<td>35-mm SLR camera body</td>
<td>Tool</td>
<td>Pentax</td>
<td>SP500 model</td>
<td>In our settings, a bellows is attached to the body of the camera to provide a convenient chamber for irradiation of the sample placed 10 cm away from the light source.</td>
</tr>
<tr>
<td>Clear, thin walled PCR tubes</td>
<td>Other</td>
<td>Eppendorf</td>
<td>951010006 supplied by Fisher L22-003-24</td>
<td>&nbsp;</td>
<tr>
<td>Glass vials (1.8 mL)</td>
<td>Other</td>
<td>Kimble Chromatography</td>
<td>60940A 2, supplied by Fisher 03-340-60</td>
<td>&nbsp;</td>
<tr>
<td>GRF</td>
<td>Reagent</td>
<td>Bachem</td>
<td>H-3695</td>
<td>&nbsp;</td>
<tr>
<td>HFIP</td>
<td>Reagent</td>
<td>TCI America</td>
<td>H0424</td>
<td>Use in a fume hood.</td>
</tr>
<tr>
<td>A&beta;40 and A&beta;42</td>
<td>Reagent</td>
<td>UCLA Biopolymers Laboratory</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Calcitonin</td>
<td>Reagent</td>
<td>American Peptide</td>
<td>22-1-10</td>
<td>&nbsp;</td>
<tr>
<td>Tris(2,2-bipridyl)dichlororuthenium(II) hexahydrate</td>
<td>Reagent</td>
<td>Sigma</td>
<td>224758-1G</td>
<td>Vortex until the solution is clear. Cover the RuBpy tube with foil to protect the reagent from ambient light. RuBpy is prepared freshly each time and should be used within 48 h.</td>
</tr>
<tr>
<td>Ammonium persulfate</td>
<td>Reagent</td>
<td>Sigma</td>
<td>A-7460</td>
<td>Vortex until the solution is clear. APS is prepared freshly each time and should be used within 48 h. </td>
</tr>
<tr>
<td>&beta;-mercaptoethanol</td>
<td>Reagent</td>
<td>Sigma</td>
<td>M7154-25 ML</td>
<td>Can be used when SDS-PAGE analysis is performed.</td>
</tr>
<tr>
<td>Novex Tricine SDS Sample Buffer (2x)</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>LC1676</td>
<td>&nbsp;</td>
<tr>
<td>XCell SureLock Mini-Cell</td>
<td>Tool</td>
<td>Invitrogen</td>
<td>EI0001</td>
<td>&nbsp;</td>
<tr>
<td>Novex Tricine Gels (10-20%)</td>
<td>Other</td>
<td>Invitrogen</td>
<td>EC6625B0X</td>
<td>&nbsp;</td>
<tr>
<td>Novex Tricine SDS Running Buffer (10x )</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>LC1675</td>
<td>&nbsp;</td>
<tr>
<td>Silver Express Staining Kit</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>LC6100</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

photo-induced cross-linking of unmodified proteins (picup) applied to amyloidogenic peptides

The assembly of amyloidogenic proteins into toxic oligomers is a seminal event in the pathogenesis of protein misfolding diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, hereditary amyotrophic lateral sclerosis, and type 2 diabetes. Owing to the metastable nature of these protein assemblies, it is difficult to assess their oligomer size distribution quantitatively using classical methods, such as electrophoresis, chromatography, fluorescence, or dynamic light scattering. Oligomers of amyloidogenic proteins exist as metastable mixtures, in which the oligomers dissociate into monomers and associate into larger assemblies simultaneously. PICUP stabilizes oligomer populations by covalent cross-linking and when combined with fractionation methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or size-exclusion chromatography (SEC), PICUP provides snapshots of the oligomer size distributions that existed before cross-linking. Hence, PICUP enables visualization and quantitative analysis of metastable protein populations and can be used to monitor assembly and decipher relationships between sequence modifications and oligomerization1. Mechanistically, PICUP involves photo-oxidation of Ru2+ in a tris(bipyridyl)Ru(II) complex (RuBpy) to Ru3+ by irradiation with visible light in the presence of an electron acceptor. Ru3+ is a strong one-electron oxidizer capable of abstracting an electron from a neighboring protein molecule, generating a protein radical1,2. Radicals are unstable, highly-reactive species and therefore disappear rapidly through a variety of intra- and intermolecular reactions. A radical may utilize the high energy of an unpaired electron to react with another protein monomer forming a dimeric radical, which subsequently loses a hydrogen atom and forms a stable, covalently-linked dimer. The dimer may then react further through a similar mechanism with monomers or other dimers to form higher-order oligomers. Advantages of PICUP relative to other photo- or chemical cross-linking methods3,4 include short (&#8804;1 s) exposure to non-destructive visible light, no need for pre facto modification of the native sequence, and zero-length covalent cross-linking. In addition, PICUP enables cross-linking of proteins within wide pH and temperature ranges, including physiologic parameters. Here, we demonstrate application of PICUP to cross-linking of three amyloidogenic proteins the 40- and 42-residue amyloid &beta;-protein variants (A&beta;40 and A&beta;42), and calcitonin, and a control protein, growth-hormone releasing factor (GRF).

Watch this Scientific Journal Video about Photo-Induced Cross-Linking of Unmodified Proteins PICUP Applied to Amyloidogenic Peptides at JoVE.com

Photo-Induced Cross-Linking of Unmodified Proteins PICUP Applied to Amyloidogenic Peptides

Photo-induced cross-linking of unmodified proteins (PICUP) allows characterization of oligomer size distribution in metastable protein mixtures. We demonstrate application of PICUP to three representative amyloidogenic peptides the 40- and 42-residue forms of amyloid &beta;-protein, and calcitonin, and a control peptide growth-hormone releasing factor.

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) Applied to Amyloidogenic Peptides

The assembly of amyloidogenic proteins into toxic oligomers is a seminal event in the pathogenesis of protein misfolding diseases, including Alzheimer's, ...

photo-induced-cross-linking-unmodified-proteins-picup-applied-to

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Biology

21.1K visualizações.  University of California, Los Angeles. Foto-induzida ligação cruzada de proteínas não modificadas (picup) permite a caracterização da distribuição de tamanho de oligômero em misturas de proteínas metaestável. Demonstramos aplicação de picup a três peptídeos representante amiloidogênicas a 40 - e 42 resíduos de formas de amilóide β-proteína, e calcitonina, peptídeo e um controle do fator de crescimento hormônio liberador.