This work was supported by grants AG030709 from NIH/NIA and 07-65798 from the California Department of Public Health. We acknowledge Margaret M. Condron for peptide synthesis and amino acid analysis, Dr. Elizabeth F. Neufeld for helping and supporting the initial steps of the project, Dr. Chi-Hong B. Chen for providing support and reagents, and Dr. Andrew D. Ellington for helpful discussions.

<ol>
	<li>Monien, B. H., Apostolova, L. G., 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=Early+diagnostics+and+therapeutics+for+Alzheimer's+disease-how+early+can+we+get+there.">Early diagnostics and therapeutics for Alzheimer's disease-how early can we get there.</a> Expert. Rev. Neurother. 6, 1293-1306 (2006).</li><li>Nestor, P. J., Scheltens, P., Hodges, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+the+early+detection+of+Alzheimer's+disease.">Advances in the early detection of Alzheimer's disease.</a> Nat. Med. 10, S34-S41 (2004).</li><li>Kawas, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+practice.+Early+Alzheimer's+disease.">Clinical practice. Early Alzheimer's disease.</a> N. Engl. J. Med. 349, 1056-1063 (2003).</li><li>Haass, C., Selkoe, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soluble+protein+oligomers+in+neurodegeneration:+lessons+from+the+Alzheimer's+amyloid+&#946;-peptide.">Soluble protein oligomers in neurodegeneration: lessons from the Alzheimer's amyloid &#946;-peptide.</a> Nat. Rev. Mol. Cell. Biol. 8, 101-112 (2007).</li><li>Kirkitadze, M. D., 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=Paradigm+shifts+in+Alzheimer's+disease+and+other+neurodegenerative+disorders:+the+emerging+role+of+oligomeric+assemblies.">Paradigm shifts in Alzheimer's disease and other neurodegenerative disorders: the emerging role of oligomeric assemblies.</a> J. Neurosci. Res. 69, 567-577 (2002).</li><li>Rahimi, F., Shanmugam, A., 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=Structure-function+relationships+of+pre-fibrillar+protein+assemblies+in+Alzheimer's+disease+and+related+disorders.">Structure-function relationships of pre-fibrillar protein assemblies in Alzheimer's disease and related disorders.</a> Curr. Alzheimer Res. 5, 319-341 (2008).</li><li>Jayasena, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aptamers:+an+emerging+class+of+molecules+that+rival+antibodies+in+diagnostics.">Aptamers: an emerging class of molecules that rival antibodies in diagnostics.</a> Clin. Chem. 45, 1628-1650 (1999).</li><li>Bunka, D. H., Stockley, 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=Aptamers+come+of+age+-+at+last.">Aptamers come of age - at last.</a> Nat. Rev. Microbiol. 4, 588-596 (2006).</li><li>Ellington, A. D., Szostak, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+selection+of+RNA+molecules+that+bind+specific+ligands.">In vitro selection of RNA molecules that bind specific ligands.</a> Nature. 346, 818-822 (1990).</li><li>Tuerk, C., Gold, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systematic+evolution+of+ligands+by+exponential+enrichment:+RNA+ligands+to+bacteriophage+T4+DNA+polymerase.">Systematic evolution of ligands by exponential enrichment: RNA ligands to bacteriophage T4 DNA polymerase.</a> Science. 249, 505-510 (1990).</li><li>Lee, J. F., Stovall, G. M., Ellington, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aptamer+therapeutics+advance.">Aptamer therapeutics advance.</a> Curr. Opin. Chem. Biol. 10, 282-289 (2006).</li><li>Weiss, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+aptamers+specifically+interact+with+the+prion+protein+PrP.">RNA aptamers specifically interact with the prion protein PrP.</a> J. Virol. 71, 8790-8797 (1997).</li><li>Bibby, D. F. <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+a+novel+in+vitro+selection+technique+to+isolate+and+characterise+high+affinity+DNA+aptamers+binding+mammalian+prion+proteins.">Application of a novel in vitro selection technique to isolate and characterise high affinity DNA aptamers binding mammalian prion proteins.</a> J. Virol. Methods. 151, 107-115 (2008).</li><li>Rhie, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+2'-fluoro-RNA+aptamers+that+bind+preferentially+to+disease-associated+conformations+of+prion+protein+and+inhibit+conversion.">Characterization of 2'-fluoro-RNA aptamers that bind preferentially to disease-associated conformations of prion protein and inhibit conversion.</a> J. Biol. Chem. 278, 39697-39705 (2003).</li><li>King, D. J., Safar, J. G., Legname, G., Prusiner, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thioaptamer+interactions+with+prion+proteins:+sequence-specific+and+non-specific+binding+sites.">Thioaptamer interactions with prion proteins: sequence-specific and non-specific binding sites.</a> J. Mol. Biol. 369, 1001-1014 (2007).</li><li>Proske, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prion-protein-specific+aptamer+reduces+PrPSc+formation.">Prion-protein-specific aptamer reduces PrPSc formation.</a> ChemBioChem. 3, 717-725 (2002).</li><li>Murakami, K., Nishikawa, F., Noda, K., Yokoyama, T., Nishikawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-bovine+prion+protein+RNA+aptamer+containing+tandem+GGA+repeat+interacts+both+with+recombinant+bovine+prion+protein+and+its+&#946;+isoform+with+high+affinity.">Anti-bovine prion protein RNA aptamer containing tandem GGA repeat interacts both with recombinant bovine prion protein and its &#946; isoform with high affinity.</a> Prion. 2, 73-80 (2008).</li><li>Luhrs, T., Zahn, R., Wuthrich, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amyloid+formation+by+recombinant+full-length+prion+proteins+in+phospholipid+bicelle+solutions.">Amyloid formation by recombinant full-length prion proteins in phospholipid bicelle solutions.</a> J. Mol. Biol. 357, 833-841 (2006).</li><li>Bunka, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+characterization+of+RNA+aptamers+specific+for+amyloid+fibril+epitopes.">Production and characterization of RNA aptamers specific for amyloid fibril epitopes.</a> J. Biol. Chem. 282, 34500-34509 (2007).</li><li>Ylera, F., Lurz, R., Erdmann, V. A., Furste, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+RNA+aptamers+to+the+Alzheimer's+disease+amyloid+peptide.">Selection of RNA aptamers to the Alzheimer's disease amyloid peptide.</a> Biochem. Biophys. Res. Commun. 290, 1583-1588 (2002).</li><li>Rahimi, F., Murakami, K., Summers, J. L., Chen, C. H., 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=RNA+aptamers+generated+against+oligomeric+A&#946;40+recognize+common+amyloid+aptatopes+with+low+specificity+but+high+sensitivity.">RNA aptamers generated against oligomeric A&#946;40 recognize common amyloid aptatopes with low specificity but high sensitivity.</a> PLoS ONE. 4, e7694-e7694 (2009).</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>Rahimi, F., Maiti, P., 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=Photo-induced+cross-linking+of+unmodified+proteins+(PICUP)+applied+to+amyloidogenic+peptides.">Photo-induced cross-linking of unmodified proteins (PICUP) applied to amyloidogenic peptides.</a> J. Vis. Exp. , (2009).</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-what+you+see+is+not+always+what+you+get.">Neurotoxic protein oligomers-what you see is not always what you get.</a> Amyloid. 12, 88-95 (2005).</li><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>Chen, C. H., Chernis, G. A., Hoang, V. Q., Landgraf, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+heregulin+signaling+by+an+aptamer+that+preferentially+binds+to+the+oligomeric+form+of+human+epidermal+growth+factor+receptor-3.">Inhibition of heregulin signaling by an aptamer that preferentially binds to the oligomeric form of human epidermal growth factor receptor-3.</a> Proc. Natl. Acad. Sci. USA. 100, 9226-9231 (2003).</li><li>Adams, 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=.">.</a> Lab math: a handbook of measurements, calculations, and other quantitative skills for use at the bench. , (2003).</li><li>Gopinath, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+developed+for+SELEX.">Methods developed for SELEX.</a> Anal. Bioanal. Chem. 387, 171-182 (2007).</li><li>Takahashi, T., Tada, K., Mihara, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+aptamers+selected+against+amyloid+&#946;-peptide+(A&#946;)+inhibit+the+aggregation+of+A&#946;.">RNA aptamers selected against amyloid &#946;-peptide (A&#946;) inhibit the aggregation of A&#946;.</a> Mol. Biosyst. 5, 986-991 (2009).</li></ol>

No conflicts of interest declared.

The starting point of the SELEX process is synthesis of a random oligonucleotide library typically containing 1012-1015 sequences. In DNA SELEX, this library is used directly after a ssDNA pool is generated, whereas in RNA SELEX, demonstrated here, the ssDNA library is converted first to an RNA pool enzymatically by in-vitro transcription. Then, SELEX is performed iteratively whereby each cycle comprises exposure and binding of oligonucleotides to the intended target, partitioning of binder...

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		<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>A&beta;40</td>
<td>&nbsp;</td>
<td>UCLA Biopolymers Laboratory</td>
<td>&nbsp;</td>
<td>Lyophilized powder</td>
</tr>
<tr>
<td>MX5 Automated-S Microbalance</td>
<td>&nbsp;</td>
<td>Mettler Toledo</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Silicon-coated, 1.6-ml tubes</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>C19033 or C19035</td>
<td>&nbsp;</td>
<tr>
<td>1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)</td>
<td>&nbsp;</td>
<td>TCI America</td>
<td>H0424</td>
<td>Use in a fume hood.</td>
</tr>
<tr>
<td>Ammonium persulfate</td>
<td>&nbsp;</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>Tris(2,2-bipridyl)dichlororuthenium(II) hexahydrate</td>
<td>&nbsp;</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>Dithiothreitol (DTT)</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>43815</td>
<td>&nbsp;</td>
<tr>
<td>D-Salt&trade; Excellulose&trade; desalting columns</td>
<td>&nbsp;</td>
<td>Thermo Scientific</td>
<td>20449</td>
<td>&nbsp;</td>
<tr>
<td>Ammonium acetate	</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>A637-500</td>
<td>&nbsp;</td>
<tr>
<td>Silicon-coated, 0.6-ml tubes</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>C19063</td>
<td>&nbsp;</td>
<tr>
<td>Novex Tricine Gels (10&#x2013;20%)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>EC6625B0X</td>
<td>10-well; mini size (8 cm X 8 cm); 25 &mu;l loading volume per well; separation range 5 kDa to 40 kDa</td>
</tr>
<tr>
<td>Quartz cuvette</td>
<td>&nbsp;</td>
<td>Hellma</td>
<td>105.250-QS</td>
<td>&nbsp;</td>
<tr>
<td>Beckman DU 640 spectrophotometer</td>
<td>&nbsp;</td>
<td>Beckman</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>ssDNA library</td>
<td>&nbsp;</td>
<td>Integrated DNA Technologies</td>
<td>Custom-ordered</td>
<td>The library was designed to contain 49 random nucleotides flanked by two constant regions containing primer-binding and cloning sites: 
5'-TAA TAC GAC TCA CTA TAG GGA ATT CCG CGT GTG C (N:25:25:25:25%) (N)49 G TCC GTT CGG GAT CCT C-3'</td>
</tr>
<tr>
<td>Taq DNA polymerase</td>
<td>&nbsp;</td>
<td>USB Corporation</td>
<td>71160</td>
<td>Recombinant Thermus aquaticus DNA Polymerase supplied with 10&#215; PCR Buffer and a separate tube of 25 mM MgCl2 for routine PCR.</td>
</tr>
<tr>
<td>PCR Nucleotide Mix, 10 mM solution</td>
<td>&nbsp;</td>
<td>USB Corporation</td>
<td>77212</td>
<td>(10 mM each dATP, dCTP, dGTP, dTTP)</td>
</tr>
<tr>
<td>Forward primer</td>
<td>&nbsp;</td>
<td>Integrated DNA Technologies</td>
<td>Custom-ordered</td>
<td>5'-TAA TAC GAC TCA CTA TAG GGA ATT CCG CGT GTG C-3'</td>
</tr>
<tr>
<td>Reverse primer</td>
<td>&nbsp;</td>
<td>Integrated DNA Technologies</td>
<td>Custom-ordered</td>
<td>5'-GAG GAT CCC GAA CGG AC-3'</td>
</tr>
<tr>
<td>Thermal cycler</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>Techne TC-312</td>
<td>&nbsp;</td>
<tr>
<td>QIAquick PCR Purification Kit (50)</td>
<td>&nbsp;</td>
<td>QIAGEN</td>
<td>28104</td>
<td>&nbsp;</td>
<tr>
<td>Agarose</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>CA3510-8</td>
<td>&nbsp;</td>
<tr>
<td>Conical, sterile 1.6-ml tubes with caps attached with O-rings</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>C19040-S</td>
<td>&nbsp;</td>
<tr>
<td>RiboMAX&trade; Large Scale RNA Production System&#x2013;T7</td>
<td>&nbsp;</td>
<td>Promega</td>
<td>P1300</td>
<td>The kit contains: 120 &mu;l Enzyme Mix (RNA polymerase, recombinant RNasin&reg; ribonuclease inhibitor and recombinant inorganic pyrophosphatase); 240 &mu;l transcription 5 buffer; 100 &mu;l each of 4 rNTPs, 100 mM; 110 U RQ1 RNase-free DNase, 1 U/&mu;l; 10 &mu;l linear control DNA, 1 mg/ml; 1 ml 3M sodium acetate (pH 5.2); 1.25 ml nuclease-Free water</td>
</tr>
<tr>
<td>&alpha;-32P-cytidine 5'-triphosphate, 250 &mu;Ci (9.25 MBq), </td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>BLU008H250UC</td>
<td>Specific Activity: 3000 Ci (111 TBq)/mmol, 50 mM Tricine (pH 7.6)</td>
</tr>
<tr>
<td>Citrate-saturated phenol:chloroform:isoamyl alcohol (125:24:1, pH 4.7)</td>
<td>&nbsp;</td>
<td>Sigma (Fluka)</td>
<td>77619</td>
<td>&nbsp;</td>
<tr>
<td>Chloroform:Isoamyl alcohol (24:1)</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>C0549</td>
<td>&nbsp;</td>
<tr>
<td>Absolute ethanol for molecular biology</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>E7023</td>
<td>&nbsp;</td>
<tr>
<td>Z216-MK refrigerated microcentrifuge</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>C0216-MK</td>
<td>&nbsp;</td>
<tr>
<td>illustra ProbeQuant&trade; G-50 Micro Columns</td>
<td>&nbsp;</td>
<td>GE Healthcare</td>
<td>Obtained from Fisher Scientific (45-001-487)</td>
<td>Prepacked with Sephadex&trade; G-50 DNA Grade and pre-equilibrated in STE buffer containing 0.15% Kathon as Biocide</td>
</tr>
<tr>
<td>Triathler Bench-top Scintillation counter</td>
<td>&nbsp;</td>
<td>Hidex Oy, Turku, Finland</td>
<td>Triathler LSC Model: 425-034</td>
<td>&nbsp;</td>
<tr>
<td>Novex&reg; TBE-Urea Sample Buffer (2&#215;)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>LC6876</td>
<td>&nbsp;</td>
<tr>
<td>6% TBE-Urea Gels 1.0 mm, 10 wells</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>EC6865BOX</td>
<td>&nbsp;</td>
<tr>
<td>Novex&reg; TBE Running Buffer (5&#215;)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>LC6675</td>
<td>&nbsp;</td>
<tr>
<td>Radioactivity decontaminant</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>04-355-67</td>
<td>&nbsp;</td>
<tr>
<td>Gel-loading tips</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>P3080</td>
<td>&nbsp;</td>
<tr>
<td>XCell SureLock Mini-Cell</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>EI0001</td>
<td>XCell SureLock Mini-Cell</td>
</tr>
<tr>
<td>Autoradiography film</td>
<td>&nbsp;</td>
<td>Denville Scientific</td>
<td>E3018</td>
<td>Use in complete darkness</td>
</tr>
<tr>
<td>Autoradiography film, Hyperfilm&trade; ECL</td>
<td>&nbsp;</td>
<td>Amersham Biosciences</td>
<td>RPN3114K</td>
<td>Can be used under red safe light.</td>
</tr>
<tr>
<td>Membrane discs</td>
<td>&nbsp;</td>
<td>Millipore</td>
<td>GSWP02500</td>
<td>Mixed cellulose ester, hydrophilic, 0.22-&mu;m disc membranes</td>
</tr>
<tr>
<td>Fritted glass support base for 125-ml flask</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>26316-696</td>
<td>&nbsp;</td>
<tr>
<td>Petri dishes</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>08-757-11YZ</td>
<td>&nbsp;</td>
<tr>
<td>Urea	</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>AC32738-0050</td>
<td>&nbsp;</td>
<tr>
<td>EDTA</td>
<td>&nbsp;</td>
<td>Fisher Scientific</td>
<td>118430010</td>
<td>&nbsp;</td>
<tr>
<td>Glycogen</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>G1767</td>
<td>&nbsp;</td>
<tr>
<td>2-Propanol for molecular biology</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>I9516</td>
<td>&nbsp;</td>
<tr>
<td>Recombinant RNase inhibitor</td>
<td>&nbsp;</td>
<td>USB Corporation</td>
<td>71571</td>
<td>&nbsp;</td>
<tr>
<td>ImProm-II&trade;Reverse Transcription System</td>
<td>&nbsp;</td>
<td>Promega</td>
<td>A3802</td>
<td>&nbsp;</td>
<tr>
<td>Recombinant RNase inhibitor</td>
<td>&nbsp;</td>
<td>USB Corporation</td>
<td>71571</td>
<td>&nbsp;</td>
<tr>
<td>RapidRun&trade; Loading Dye</td>
<td>&nbsp;</td>
<td>USB Corporation</td>
<td>77524</td>
<td>&nbsp;</td>		</tbody>
		</table>
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selection of aptamers for amyloid &beta;-protein, the causative agent of alzheimer&#39;s disease

Alzheimer's disease (AD) is a progressive, age-dependent, neurodegenerative disorder with an insidious course that renders its presymptomatic diagnosis difficult1. Definite AD diagnosis is achieved only postmortem, thus establishing presymptomatic, early diagnosis of AD is crucial for developing and administering effective therapies2,3.
Amyloid &beta;-protein (A&beta;) is central to AD pathogenesis. Soluble, oligomeric A&beta; assemblies are believed to affect neurotoxicity underlying synaptic dysfunction and neuron loss in AD4,5. Various forms of soluble A&beta; assemblies have been described, however, their interrelationships and relevance to AD etiology and pathogenesis are complex and not well understood6. Specific molecular recognition tools may unravel the relationships amongst A&beta; assemblies and facilitate detection and characterization of these assemblies early in the disease course before symptoms emerge. Molecular recognition commonly relies on antibodies. However, an alternative class of molecular recognition tools, aptamers, offers important advantages relative to antibodies7,8. Aptamers are oligonucleotides generated by in-vitro selection: systematic evolution of ligands by exponential enrichment (SELEX)9,10. SELEX is an iterative process that, similar to Darwinian evolution, allows selection, amplification, enrichment, and perpetuation of a property, e.g., avid, specific, ligand binding (aptamers) or catalytic activity (ribozymes and DNAzymes).
Despite emergence of aptamers as tools in modern biotechnology and medicine11, they have been underutilized in the amyloid field. Few RNA or ssDNA aptamers have been selected against various forms of prion proteins (PrP)12-16. An RNA aptamer generated against recombinant bovine PrP was shown to recognize bovine PrP-&beta;17, a soluble, oligomeric, &beta;-sheet-rich conformational variant of full-length PrP that forms amyloid fibrils18. Aptamers generated using monomeric and several forms of fibrillar &beta;2-microglobulin (&beta;2m) were found to bind fibrils of certain other amyloidogenic proteins besides &beta;2m fibrils19. Ylera et al. described RNA aptamers selected against immobilized monomeric A&beta;4020. Unexpectedly, these aptamers bound fibrillar A&beta;40. Altogether, these data raise several important questions. Why did aptamers selected against monomeric proteins recognize their polymeric forms? Could aptamers against monomeric and/or oligomeric forms of amyloidogenic proteins be obtained? To address these questions, we attempted to select aptamers for covalently-stabilized oligomeric A&beta;4021 generated using photo-induced cross-linking of unmodified proteins (PICUP)22,23. Similar to previous findings17,19,20, these aptamers reacted with fibrils of A&beta; and several other amyloidogenic proteins likely recognizing a potentially common amyloid structural aptatope21. Here, we present the SELEX methodology used in production of these aptamers21.

Watch this Scientific Journal Video about Selection of Aptamers for Amyloid Î²-Protein, the Causative Agent of Alzheimer's Disease at JoVE.com

Selection of Aptamers for Amyloid &amp;#946;-Protein, the Causative Agent of Alzheimer&#039;s Disease

Aptamers are short ribo-/deoxyribo-oligonucleotides selected by in-vitro evolution methods based on affinity for a specific target. Aptamers are molecular recognition tools with versatile therapeutic, diagnostic, and research applications. We demonstrate methods for selection of aptamers for amyloid &beta;-protein, the causative agent of Alzheimer's disease.

Selection of Aptamers for Amyloid &beta;-Protein, the Causative Agent of Alzheimer&#39;s Disease

Alzheimer's disease (AD) is a progressive, age-dependent, neurodegenerative disorder with an insidious course that renders its presymptomatic diagnosis ...

selection-aptamers-for-amyloid-protein-causative-agent-alzheimer-s

Research

JoVE Journal

Neuroscience

19.3K Views.  David Geffen School of Medicine. Aptamers are short ribo-/deoxyribo-oligonucleotides selected by in-vitro evolution methods based on affinity for a specific target. Aptamers are molecular recognition tools with versatile therapeutic, diagnostic, and research applications. We demonstrate methods for selection of aptamers for amyloid β-protein, the causative agent of Alzheimer's disease.

Video: Selection of Aptamers for Amyloid &#946;-Protein, the Causative Agent of Alzheimer's Disease

Assaying &beta;-amyloid Toxicity using a Transgenic C. elegans Model

Accumulation of the &beta;-amyloid peptide (A&beta;) is generally believed to be central to the induction of Alzheimer's disease, but the relevant mechanism(s) of toxicity are still unclear. A&beta; is also deposited intramuscularly in Inclusion Body Myositis, a severe human myopathy. The intensely studied nematode worm Caenorhabditis elegans can be transgenically engineered to express human A&beta;. Depending on the tissue or timing of A&beta; expression, transgenic worms can have readily measurable phenotypes that serve as a read-out of A&beta; toxicity. For example, transgenic worms with pan-neuronal A&beta; expression have defects is associative learning (Dosanjh et al. 2009), while transgenic worms with constitutive muscle-specific expression show a progressive, age-dependent paralysis phenotype (Link, 1995; Cohen et al. 2006). One particularly useful C. elegans model employs a temperature-sensitive mutation in the mRNA surveillance system to engineer temperature-inducible muscle expression of an A&beta; transgene, resulting in a reproducible paralysis phenotype upon temperature upshift (Link et al. 2003). Treatments that counter A&beta; toxicity in this model [e.g., expression of a protective transgene (Hassan et al. 2009) or exposure to Ginkgo biloba extracts (Wu et al. 2006)] reproducibly alter the rate of paralysis induced by temperature upshift of these transgenic worms. Here we describe our protocol for measuring the rate of paralysis in this transgenic C. elegans model, with particular attention to experimental variables that can influence this measurement.

Assaying &amp;#946;-amyloid Toxicity using a Transgenic C. elegans Model

The intensely studied nematode worm Caenorhabditis elegans can be transgenically engineered to express the human &beta;-amyloid peptide (A&beta;). Induced expression of A&beta; in C. elegans muscle leads to a rapid, reproducible paralysis phenotype that can be used to monitor treatments that modulate A&beta; toxicity.

Accumulation of the &beta;-amyloid peptide (A&beta;) is generally believed to be central to the induction of Alzheimer's disease, but the relevant ...

Detection of Neuritic Plaques in Alzheimer's Disease Mouse Model

Alzheimer's disease (AD) is the most common neurodegenerative disorder leading to dementia. Neuritic plaque formation is one of the pathological hallmarks of Alzheimer's disease. The central component of neuritic plaques is a small filamentous protein called amyloid &beta; protein (A&beta;)1, which is derived from sequential proteolytic cleavage of the beta-amyloid precursor protein (APP) by &beta;-secretase and &gamma;-secretase. The amyloid hypothesis entails that A&gamma;-containing plaques as the underlying toxic mechanism in AD pathology2. The postmortem analysis of the presence of neuritic plaque confirms the diagnosis of AD. To further our understanding of A&gamma; neurobiology in AD pathogenesis, various mouse strains expressing AD-related mutations in the human APP genes were generated. Depending on the severity of the disease, these mice will develop neuritic plaques at different ages. These mice serve as invaluable tools for studying the pathogenesis and drug development that could affect the APP processing pathway and neuritic plaque formation. In this protocol, we employ an immunohistochemical method for specific detection of neuritic plaques in AD model mice. We will specifically discuss the preparation from extracting the half brain, paraformaldehyde fixation, cryosectioning, and two methods to detect neurotic plaques in AD transgenic mice: immunohistochemical detection using the ABC and DAB method and fluorescent detection using thiofalvin S staining method.

Detection of Neuritic Plaques in Alzheimer&#039;s Disease Mouse Model

One of the pathological characteristics of AD is the formation of Amyloid &#x03B2; protein positive neuritic plaques. In this protocol we describe two methods to detect neuritic plaques in transgenic AD model mice: immunohistochemical detection using the ABC and DAB method and fluorescent detection using thioflavin S staining method.

Alzheimer's disease (AD) is the most common neurodegenerative disorder leading to dementia. Neuritic plaque formation is one of the pathological hallmarks ...

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this information to the brain. As such, determining how olfactory information is transferred to the brain, modifying both perception and behavior, merits investigation. Interestingly, there is emerging evidence that cellular transduction and transcriptional factors are involved in the diversification of olfactory receptor neuron. Here we provide a robust whole mount immunological labeling method to assay in vivo olfactory receptor neuron organization. Using this method, we identified all olfactory receptor neurons with anti-ELAV antibody, a known pan-neural marker and Or49a-mCD8::GFP, an olfactory receptor neuron specifically expressed in Nba neuron using anti-GFP antibody.

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Herein we describe the process of whole mount immunostaining of Drosophila antennae, which enables us to better understand the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s.

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this ...

Olfactory Assays for Mouse Models of Neurodegenerative Disease

In many neurodegenerative diseases and particularly in Parkinson&#8217;s disease, deficits in olfaction are reported to occur early in the disease process and may be a useful behavioral marker for early detection. Earlier detection in neurodegenerative disease is a major goal in the field because this is when neuroprotective therapies have the best potential to be effective. Therefore, in preclinical studies testing novel neuroprotective strategies in rodent models of neurodegenerative disease, olfactory assessment could be highly useful in determining therapeutic potential of compounds and translation to the clinic. In the present study we describe a battery of olfactory assays that are useful in measuring olfactory function in mice. The tests presented in this study were chosen because they measure olfaction abilities in mice related to food odors, social odors, and non-social odors. These tests have proven useful in characterizing novel genetic mouse models of Parkinson&#8217;s disease as well as in testing potential disease-modifying therapies.

Impairment in olfactory function is a common feature in many neurodegenerative disorders including Parkinson, Alzheimer, and Huntington diseases. In the present article, we describe a set of tests for assessing olfaction discrimination and detection in mice that can be used to measure olfactory abilities in mouse models of neurodegenerative diseases.

In many neurodegenerative diseases and particularly in Parkinson&#8217;s disease, deficits in olfaction are reported to occur early in the disease process ...

Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

Alzheimer&#8217;s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the over-production of amyloid-beta and the deposition of amyloid-beta plaques in brain regions of the afflicted individuals. Throughout the years scientists have generated numerous Alzheimer&#8217;s disease mouse models that attempt to replicate the amyloid-beta pathology. Unfortunately, the mouse models only selectively mimic the disease features. Neuronal death, a prominent effect in the brains of Alzheimer&#8217;s disease patients, is noticeably lacking in these mice. Hence, we and others have employed a method of directly infusing soluble oligomeric species of amyloid-beta - forms of amyloid-beta that have been proven to be most toxic to neurons - stereotaxically into the brain. In this report we utilize male C57BL/6J mice to document this surgical technique of increasing amyloid-beta levels in a select brain region. The infusion target is the dentate gyrus of the hippocampus because this brain structure, along with the basal forebrain that is connected by the cholinergic circuit, represents one of the areas of degeneration in the disease. The results of elevating amyloid-beta in the dentate gyrus via stereotaxic infusion reveal increases in neuron loss in the dentate gyrus within 1 week, while there is a concomitant increase in cell death and cholinergic neuron loss in the vertical limb of the diagonal band of Broca of the basal forebrain. These effects are observed up to 2 weeks. Our data suggests that the current amyloid-beta infusion model provides an alternative mouse model to address region specific neuron death in a short-term basis. The advantage of this model is that amyloid-beta can be elevated in a spatial and temporal manner.

Here, we present a protocol for direct stereotaxic brain infusion of amyloid-beta. This methodology provides an alternative in vivo mouse model to address the short-term effects of amyloid-beta on brain neurons.

Alzheimer&#8217;s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the ...

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic pathways. Quantitative descriptions are rarely performed, although genetic manipulations produce a range of phenotypic effects and variations are observed even among individuals within control groups.&#160;Emerging evidence shows that morphology, size and location of organelles play a previously underappreciated, yet fundamental role in cell function and survival. Here we provide step-by-step instructions for performing quantitative analyses of phenotypes at the Drosophila larval neuromuscular junction (NMJ). We use several reliable immuno-histochemical markers combined with bio-imaging techniques and morphometric analyses to examine the effects of genetic mutations on specific cellular processes. In particular, we focus on the quantitative analysis of phenotypes affecting morphology, size and position of nuclei within the striated muscles of Drosophila larvae. The Drosophila larval NMJ is a valuable experimental model to investigate the molecular mechanisms underlying the structure and the function of the neuromuscular system, both in health and disease. However, the methodologies we describe here can be extended to other systems as well.

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Morphology, size and location of intracellular organelles are evolutionarily conserved and appear to directly affect their function. Understanding the molecular mechanisms underlying these processes has become an important goal of modern biology. Here we show how these studies can be facilitated by the application of quantitative techniques.

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic ...

Modeling Amyloid-&#946;42 Toxicity and Neurodegeneration in Adult Zebrafish Brain

Alzheimer's disease (AD) is a debilitating neurodegenerative disease in which accumulation of toxic amyloid-&#946;42 (A&#946;42) peptides leads to synaptic degeneration, inflammation, neuronal death, and learning deficits. Humans cannot regenerate lost neurons in the case of AD in part due to impaired proliferative capacity of the neural stem/progenitor cells (NSPCs) and reduced neurogenesis. Therefore, efficient regenerative therapies should also enhance the proliferation and neurogenic capacity of NSPCs. Zebrafish (Danio rerio) is a regenerative organism, and we can learn the basic molecular programs with which we could design therapeutic approaches to tackle AD. For this reason, the generation of an AD-like model in zebrafish was necessary. Using our methodology, we can introduce synthetic derivatives of A&#946;42 peptide with tissue penetrating capability into the adult zebrafish brain, and analyze the disease pathology and the regenerative response. The advantage over the existing methods or animal models is that zebrafish can teach us how a vertebrate brain can naturally regenerate, and thus help us to treat human neurodegenerative diseases better by targeting endogenous NSPCs. Therefore, the amyloid-toxicity model established in the adult zebrafish brain may open new avenues for research in the field of neuroscience and clinical medicine. Additionally, the simple execution of this method allows for cost-effective and efficient experimental assessment. This manuscript describes the synthesis and injection of A&#946;42 peptides into zebrafish brain.

Modeling Amyloid-&amp;#946;42 Toxicity and Neurodegeneration in Adult Zebrafish Brain

This protocol describes the synthesis, characterization, and injection of monomeric amyloid-&#946;42 peptides for generating amyloid toxicity in adult zebrafish to establish an Alzheimer&#39;s disease model, followed by histological analyses and detection of aggregations.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease in which accumulation of toxic amyloid-&#946;42 (A&#946;42) peptides leads to ...

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal

An increasing number of super-resolution microscopy techniques are helping to uncover the mechanisms that govern the nanoscale cellular world. Single-molecule imaging is gaining momentum as it provides exceptional access to the visualization of individual molecules in living cells. Here, we describe a technique that we developed to perform single-particle tracking photo-activated localization microscopy (sptPALM) in Drosophila larvae. Synaptic communication relies on key presynaptic proteins that act by docking, priming, and promoting the fusion of neurotransmitter-containing vesicles with the plasma membrane. A range of protein-protein and protein-lipid interactions tightly regulates these processes and the presynaptic proteins therefore exhibit changes in mobility associated with each of these key events. Investigating how mobility of these proteins correlates with their physiological function in an intact live animal is essential to understanding their precise mechanism of action. Extracting protein mobility with high resolution in vivo requires overcoming limitations such as optical transparency, accessibility, and penetration depth. We describe how photoconvertible fluorescent proteins tagged to the presynaptic protein Syntaxin-1A can be visualized via slight oblique illumination and tracked at the motor nerve terminal or along the motor neuron axon of the third instar Drosophila larva.

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal

Here we illustrate how single molecule photo-activated localization microscopy can be carried out on the motor nerve terminal of a live Drosophila melanogaster third instar larva.

An increasing number of super-resolution microscopy techniques are helping to uncover the mechanisms that govern the nanoscale cellular world. ...

Visualization of Amyloid &#946; Deposits in the Human Brain with Matrix-assisted Laser Desorption/Ionization Imaging Mass Spectrometry

The neuropathology of Alzheimer&#39;s disease (AD) is characterized by the accumulation and aggregation of amyloid &#946; (A&#946;) peptides into extracellular plaques of the brain. The A&#946; peptides, composed of 40 amino acids, are generated from amyloid precursor proteins (APP) by &#946;- and &#947;-secretases. A&#946; is deposited not only in cerebral parenchyma but also in leptomeningeal and cerebral vessel walls, known as cerebral amyloid angiopathy (CAA). While a variety of A&#946; peptides were identified, the detailed production and distribution of individual A&#946; peptides in pathological tissues of AD and CAA have not been fully addressed. Here, we develop a protocol of matrix-assisted laser desorption/ionization-based imaging mass spectrometry (MALDI-IMS) on human autopsy brain tissues to obtain comprehensive protein mapping. For this purpose, human cortical specimens were obtained from the Brain Bank at the Tokyo Metropolitan Institute of Gerontology. Frozen cryosections are cut and transferred to indium-tin-oxide (ITO)-coated glass slides. Spectra are acquired using the MALDI system with a spatial resolution up to 20 &#181;m. Sinapinic acid (SA) is uniformly deposited on the slide using either an automatic or a manual sprayer. With the current technical advantages of MALDI-IMS, a typical data set of various A&#946; species within the same sections of human autopsied brains can be obtained without specific probes. Furthermore, high-resolution (20 &#181;m) imaging of an AD brain and severe CAA sample clearly shows that A&#946;1-36 to A&#946;1-41 were deposited into leptomeningeal vessels, while A&#946;1-42 and A&#946;1-43 were deposited in cerebral parenchyma as senile plaque (SP). It is feasible to adopt MALDI-IMS as a standard approach in combination with clinical, genetic, and pathological observations in understanding the pathology of AD, CAA, and other neurological diseases based on the current strategy.

Visualization of Amyloid &amp;#946; Deposits in the Human Brain with Matrix-assisted Laser Desorption/Ionization Imaging Mass Spectrometry

Molecular imaging with matrix-assisted laser desorption/ionization-based imaging mass spectrometry (MALDI-IMS) allows the simultaneous mapping of multiple analytes in biological samples. Here, we present a protocol for the detection and visualization of amyloid &#946; protein on brain tissues of Alzheimer&#39;s disease and cerebral amyloid angiopathy samples using MALDI-IMS.

The neuropathology of Alzheimer&#39;s disease (AD) is characterized by the accumulation and aggregation of amyloid &#946; (A&#946;) peptides into ...

Labeling and Imaging of Amyloid Plaques in Brain Tissue Using the Natural Polyphenol Curcumin

Deposition of amyloid beta protein (A&#946;) in extra- and intracellular spaces is one of the hallmark pathologies of Alzheimer&#39;s disease (AD). Therefore, detection of the presence of A&#946; in AD brain tissue is a valuable tool for developing new treatments to prevent the progression of AD. Several classical amyloid binding dyes, fluorochrome, imaging probes, and A&#946;-specific antibodies have been used to detect A&#946; histochemically in AD brain tissue. Use of these compounds for A&#946; detection is costly and time consuming. However, because of its intense fluorescent activity, high-affinity, and specificity for A&#946;, as well as structural similarities with traditional amyloid binding dyes, curcumin (Cur) is a promising candidate for labeling and imaging of A&#946; plaques in postmortem brain tissue. It is a natural polyphenol from the herb Curcuma longa. In the present study, Cur was used to histochemically label A&#946; plaques from both a genetic mouse model of 5x familial Alzheimer&#39;s disease (5xFAD) and from human AD tissue within a minute. The labeling capability of Cur was compared to conventional amyloid binding dyes, such as thioflavin-S (Thio-S), Congo red (CR), and Fluoro-jade C (FJC), as well as A&#946;-specific antibodies (6E10 and A11). We observed that Cur is the most inexpensive and quickest way to label and image A&#946; plaques when compared to these conventional dyes and is comparable to A&#946;-specific antibodies. In addition, Cur binds with most A&#946; species, such as oligomers and fibrils. Therefore, Cur could be used as the most cost-effective, simple, and quick fluorochrome detection agent for A&#946; plaques.

Curcumin is an ideal fluorophore for labeling and imaging of amyloid beta protein plaques in brain tissue due to its preferential binding to amyloid beta protein as well as its structural similarities with other traditional amyloid binding dyes. It can be used to label and image amyloid beta protein plaques more efficiently and inexpensively than traditional methods.

Deposition of amyloid beta protein (A&#946;) in extra- and intracellular spaces is one of the hallmark pathologies of Alzheimer&#39;s disease (AD). ...