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Table 1. Gold nanoparticles obtained by ligand-exchange reactionLigandLigand/Ph(CH 2 ) 2 SH Ratio Usedfor the Exchange ReactionExtent of Exchange(“death reaction”)Percentage ofExchange1 1.72 16-17 ~90%1 0.7 5-6 ~30%1 0.2 3-4 ~20%2 0.7 7-8 ~40%observed that irradiation at 366 nm leads to formation of a mixture of the cis and transisomers with, under our experimental conditions, a cis to trans ratio of about 70% (Trtprotected1, Figure 2B) and 40% (2). Upon trans→cis transition, the peptide 3 10 -helicalstructure remained intact, as indicated by FT-IR, but we observed noticeable changes in the1 H NMR spectrum, including peaks of the peptide moiety (CH 3 groups of Aib). Thermaldecay experiments at r.t. showed that the spontaneous cis to trans conversion (in the dark)has a t 1/2 of 29.6 hours for Trt-protected 1.Different amounts of 1 or 2 were used to carry out the ligand-exchange reaction. Thepercentage of substitution was determined by destruction of the so-obtained MPCs withiodine, and calculation of the ratio between the resulting oxidized phenylethanethiol andexogenous ligand by 1 H NMR (“death reaction”) (Table 1).We also carried an analytical HPLC separation of the MPCs containing 90% of 1,whereas the MPCs with 20 and 30% of 1 showed a single broad peak. Irradiation of thesubstituted MPCs also led to spectral changes related to trans→cis isomerization. Underotherwise identical conditions, the decrease of the intensity of the main band was much lesspronounced than for the free ligand (Figure 2C). We also observed that the decrease wasless marked for more substituted MPCs. The cis→trans thermal decay was about 3 timesfaster than observed for the free ligand. These observations are in agreement with stericalhindrance affecting the isomerization process when the ligands are in the MPC monolayer.FT-IR analysis of N-H stretchregion (Amide A) showed thepresence of inter- and intramolecularH-bonds as well as freeN-H groups (Figure 3). Whereasthe stretch frequency of the freeN-H groups does not changesignificantly, the band of intramolecularH-bonds red-shiftswhen the ligand is in the MPCmonolayer. This is attributed toenhancement of the stiffness ofthe 3 10 -helical structure when thepeptide ligand is in the monolayer.Further shift takes place uponirradiation causing trans→cisisomerization, but the effectFig.3. FT-IR analysis of the substituted MPCs.vanishes when the nanoparticle isheavily substituted (90%).Differential Pulse Voltammetry (DPV) showed that for the MPCs with 20% and 30%of 1 as well as 40% of 2 the two main oxidation peaks are located at more positivepotentials and are more separated with respect to the corresponding oxidation peaks of thenative nanoparticle, Au 25 (SCH 2 CH 2 Ph) 18 . The positive shift is in line with the expectedpeptide dipole-moment effect on the charging behavior. In particular, the potential shift ismore evident for the 30% substituted MPC.References1. Murray, R.W. Chem. Rev. 108, 2688-2720 (2008).2. Antonello, S., et al. J. Am. Chem. Soc. 129, 9836-9837 (2007).3. Fabris, L., et al. J. Am. Chem. Soc. 128, 326-336 (2006).4. Holms, A.H., et al. Langmuir 22, 10584-10589 (2006).617
Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Photocurrent Generation Through Mono- and BicomponentPeptide Self-Assembled Monolayers:Antenna and Junction EffectsAlessandro Porchetta 1 , Emanuela Gatto 1 , Mario Caruso 1 ,Marco Crisma 2 , Fernando Formaggio 2 , Claudio Toniolo 2 ,and Mariano Venanzi 11 Department of Chemical Sciences and Technologies, University of Rome “Tor Vergata”,Rome, 00133, Italy; 2 ICB, Padova Unit, CNR, Department of Chemistry,University of Padova, Padova, 35131, ItalyIntroductionHybrid materials obtained by functionalizing metals or semiconductors with biomoleculesor bioinspired molecular systems have been recently synthesized, paving the way for thefast-growing field of bionanoelectronics. The photocurrent generation properties of monoandbicomponent, peptide-based self-assembled monolayers (SAMs) immobilized on agold surface were studied by electrochemical and spectroscopic techniques. The peptidesinvestigated were exclusively formed by C -tetrasubstituted -amino acids. These residues,due to their peculiar conformational properties [1,2], constrain the peptide in a helicalconformation, as confirmed by X-ray diffraction structure determinations, and circulardichroism and NMR experiments in solution.Results and DiscussionAn Aib ( -aminoisobutyric acid) homo-hexapeptide was functionalized at the N-terminuswith a lipoic group for immobilization to a gold substrate exploiting the strong Au-Saffinity (≈40kcal mol -1 ). The peptide was further functionalized with a pyrene chromophore(SSA6Pyr) strongly absorbing in the UV-Vis region to enhance the molecular photoncapture cross-section. A peptide with the same backbone, but lacking the pyrenechromophore (SSA6), was also synthesized as a reference compound.SSA6SSA6PyrA photoactive octapeptide (A8Pyr), formed exclusively by C -tetrasubstituted residues andcomprising a pyrene chromophore but not linked to the gold surface as it lacks the lipoicgroup, was additionally prepared for photocurrent studies of a peptide SAM:Z-Aib-Api(Pyr)-L-( Me)Val-Aib-L-( Me)Val -L-( Me)Val -Aib-Api(Boc)-NHtBu (A8Pyr)where Z is benzyloxycarbonyl, ( Me)Val is C -methyl valine, Boc is tert-butyloxycarbonyl,and Api is 4-aminopiperidine-4-carboxylic acid.ecc =330nmonofft= 60 s5 nAFig. 1. Photocurrent generation experiment on a gold electrode modified by deposition ofan SSA6Pyr film.618
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Peptides 2010Tales of PeptidesProce
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Peptides 2010Tales of PeptidesProce
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IntroductionWe had the distinct hon
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Scientific programIn planning the 3
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31 st EUROPEAN PEPTIDE SYMPOSIUMSep
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published by John Wiley & Sons as a
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The Josef Rudinger AwardThis award
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Young Investigators' SymposiumThe y
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xxiv
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Design of Peptidyl-Inhibitors for G
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Synthetic Antifreeze Glycopeptide A
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Synthesis and Oxidative Folding of
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Convergent Syntheses of Huprp106-12
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Bactericidal Activity of Small Beta
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Bradykinin Analogues Acylated on Th
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Antimicrobial Activity of Small 3-(
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Interaction of Curcumin with A-Synu
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Fluorescent and Luminescent Fusion
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Cellular Expression of the Human An
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2D IR Spectroscopy of Oligopeptides
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large, non-redundant subset of prot
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The aberrantly glucosylated peptide
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Table 1. Proline cis/trans ratios o
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Table 1. Yields, UV-vis absorption
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Table 1. Purity of the targeted tri
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processes are blocked. Interestingl
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(tb4 n ,1 m )MTII(tb1 n ,4 m )MTIIF
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Fig. 2. a) Part of the 400 MHz HR-M
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Once printed, the amino acid partic
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A) PSA, few seconds73B) PSA, 45 min
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short β strands. In contrast, nume
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neg. control Cs9-Rhd MM-218Fig. 2.
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Table 1. The general structure of t
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% ID in the liver 1 h p.i.100908070
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Peptidyl phosphoranes were first re
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obtained from the same sardines and
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MccJ25 variants were produced by si
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Fig. 2. Proposed signaling mechanis
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Table 1. mCD4-HS12 antiviral activi
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Page 613 and 614: Proceedings of the 31 st European P
Page 663: Proceedings of the 31 st European P
Page 679 and 680: Subject index(S)-2-(1-adamantyl)gly
Page 681 and 682: chip 18chiral triazine condensing r
Page 683 and 684: heat stress 348helical conformation
Page 685 and 686: O-acyl isopeptide method 112obesity
Page 687 and 688: SH2-ligands 210short collagen-relat
Page 689 and 690: Author indexAboye, Teshome Leta 142
Page 691 and 692: Chi, Hongfang 480Chiche, Laurent 6C
Page 693 and 694: Geronikaki, Athina 444Gessmann, Ren
Page 695 and 696: Kostova, Kalina 528Kotzia, Georgia
Page 697 and 698: Nagata, Koji 162Nagayev, Igor Yu. 5
Page 699 and 700: Salvarese, Nicola 518Sammet, Benedi
Page 701 and 702: Vauquelin, Georges 138Veiga, Ana Sa
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