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RT: 0,00 - 5,99360000340000320000300000280000260000240000220000200000180000160000140000120000100000800006000040000200000,190,721,031,281,501,711,912,142,412,552,702,933,063,413,874,174,444,714,935,075,875,98NL:3,62E5Channel AUV306_03729_02Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Solid Phase Synthesis and Characterisation of a Platelet-DerivedGrowth Factor Receptor (PDGFR) Specific Affibody MoleculeBård Indrevoll, Roger Bjerke, Dimitrios Mantzilas, Erlend Hvattum,and Astri RogstadGE Healthcare AS, 0401, Oslo, NorwayIntroductionA 66 amino acid PDGFR specific Affibody [1] peptide was prepared by microwaveassistedautomated solid-phase synthesis. The peptide was assembled on a 100% PEG resinaffording good purity and acceptable yield of crude Affibody. Fmoc-deprotection stepswere carried out using piperazine in order to suppress aspartimide formation [2].Pseudo-proline was incorporated in the peptide backbone. The identity of the syntheticAffibody was confirmed by TOF-MS. The secondary structure content was compared withits recombinant counterpart [3] using circular dichroism (CD) and the biological activityassessed by fluorescence polarisation (FP) and surface plasmon resonance (SPR)techniques.Results and DiscussionAffibody molecules, members of the family of antibody mimetics, are small high affinityproteins engineered to bind specifically to a large number of target proteins [4]. Affibodymolecules are composed of three alpha helices and lack disulfide bridges. The three-helixbundle structure is one of the fastest folding protein structure known [5]. The purpose ofthis study was to evaluate the feasibility of preparing a 66 amino acid Affibody peptide(GSSLQVDNKF NKELIEAAAE IDALPNLNRR QWNAFIKSLV DDPSQSANLL) bysolid-phase synthesis and to compare the synthetic peptide with its recombinant counterpartwith respect to secondary structure and biological activity.Solid-phase synthesis was carried out on a CEM Liberty microwave peptidesynthesiser using Fmoc/tBu strategy starting with 0.05 mmol NovaPEG Rink amide resin(0.67 mmol/g). Single couplings of amino acid (0.5 mmol) using HBTU (0.45mmol)/HOAt (0.45 mmol)/DIPEA (1 mmol) in NMP were employed except in the case ofArg(Pbf) residues where double couplings were used. A pseudo-proline dipeptide wasincorporated for Lys 37 -Ser 38 . Fmoc-deprotection was carried out using 5% piperazine/0.1 MHOAt in NMP. The peptide was cleaved from the resin by 2.5% water, 2.5% EDT, 2.5%TIS, 92.5% TFA (10 mL) affording 148 mg (41%) crude Affibody. No aspartimideformation was observed.Purification by HPLC on a Phenomenex Luna 5µ C18 (2) column applying gradientelution (20-50% B over 40 min where A = H 2 O/0.1% TFA and B = ACN/0.1% TFA)uAU00,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5Time (min)Fig. 1. Analytical HPLC chromatogram ofpurified synthetic Affibody.afforded 49 mg (14%) pure lyophilisedAffibody. MS analysis of the product wasperformed on a QTof-micro massspectrometer operating with ESI + (expectedfor C 315 H 511 N 91 O 102 S: 1034.8 (MH 7 7 +),1207.1 (MH 6 6 +), 1448.4 (MH 5 5 +), 1810.2(MH 4 4 +); m/z found: 1034.8, 1207.2,1448.4, 1810.0). Analytical HPLC (Figure1) was run on a Phenomenex Luna 3µ C18(2) 20 x 2 mm column (20-50% B over 5min; A = H 2 O/0.1% TFA and B =ACN/0.1% TFA; 0.6 mL/min; UV 214 nm).Fluorescence polarisation (FP) analyses were performed on a Tecan Safire FP platereader at ex635/em678 nm using PBS (pH 7.5) with 0.01% Tween-20 as binding buffer.The concentration of CyDye-labelled synthetic Affibody was 5 nM and the concentrationof rhPDGFR β (R&D Systems) was varied from 0 to 250 nM. Binding of labelled Affibodyto the PDGF receptor was observed (Figure 2). The labelled Affibody has a MW that is atthe limit of what can be detected in the FP assay (>8 kDa). Hence, no reliable Kd value wascalculated.62