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Conformational studies of ?-helix structures in D,L-alternating oligonorleucine peptides by C? and H? chemical shifts and FTIR spectroscopy.

2005
2005
Inglese
VII Convegno "Complex Systems: structure, properties, reactivity and dynamics"
13-15 Giugno 2005
Alghero
Conformational studies of ?-helix structures in D,L-alternating oligonorleucine peptides by C? and H? chemical shifts and FTIR spectroscopy. The conformational analysis of D,L alternating peptides is a alternative way to enhance our knowledge about the ?-helix transmembrane ion channels and how affect factors like the main chain length or terminal group in the adoption of a specific ?-helix structure. A family of oligopeptides formed by D,L alternating norleucines has been selected to analyze the influence of those factors on the ?-helix conformational features. Inter-conformer steric repulsions were reduced using lineal side chains. Boc and formyl are used as terminal groups, and all this peptides are methylated in the residue (n-3). Previous NMR data combined with Molecular Dynamics calculations indicate that Boc-XIIMe-OMe and Boc-XVMe-OMe assume a single right handed ?4.4 and double right handed antiparallel ?5.6 respectively in chloroform. For the peptide HCO-XMe-OMe using the same methodology a equilibrium between a ?4.4 and ???5.6 conformation. The combined analysis of this previous structural information, 1H and 13C secondary chemical shifts (??) and FTIR data has allowed to establish empirical rules to identify the ?-helix conformation for the whole set of these oligopeptides. The discrimination among the different ?-helix configurations has been properly achieved by the analysis of H? secondary chemical shifts (??H?). ??H? values for ?4.4 conformation are negative while for ???5.6 structures are positive. On the contrary, a direct correlation between C? and C? chemical shifts and ?-helix conformation was not found. Additionally the FTIR spectrum in solution showed that the amide I bands are strongly dependent on the conformation and allowed to associate bands at 1646 cm-1 with a ?4.4 conformation and 1633 cm-1 with ???5.6 configuration respectively. The analysis of the whole family of norleucine oligopeptides indicated that if the main chain length increases, the ???5.6 conformation is more favourable by stabilisation the through additional inter-strand H-bonds. On the other hand, the deletion of the Boc group reduces the steric effects in the N-terminal part of the peptide, shifting the conformational equilibrium towards the ???5.6 structure. [1] E Fenude, L. Tomasic, G.P. Lorenzi, Biopolymers, 28, (1989), , 185 [2] E..Fenude, D.U. Römer, G.P. Lorenzi,. Int J Pept Protein Res 44, (1993), 10 [3] E. Navarro, R. Tejero, E. Fenude, B. Celda, Biopolymers, 59, (2001), 110 [4] E. Navarro, E. Fenude, B. Celda, Biopolymers, 64, (2002), 198 [5] E. Navarro, E. Fenude, B. Celda, Biopolymers, 73, (2004), 229
none
info:eu-repo/semantics/conferenceObject
Fenude E. S.Dedola; M. Fais; A.M. Roggio.
275
04 Contributo in convegno::04.03 Poster in Atti di convegno
1
04.03 Poster in Atti di convegno
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/15579
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