Premium
Structural features of model glycopeptides in solution and in membrane phase: A spectroscopic and molecular mechanics investigation
Author(s) -
Stella L.,
Venanzi M.,
Carafa M.,
Maccaroni E.,
Straccamore M. E.,
Zanotti G.,
Palleschi A.,
Pispisa B.
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10121
Subject(s) - chemistry , side chain , quenching (fluorescence) , förster resonance energy transfer , fluorescence , bilayer , membrane , fluorescence anisotropy , helix (gastropod) , peptide , crystallography , molecular dynamics , molecule , stereochemistry , computational chemistry , organic chemistry , biochemistry , polymer , ecology , physics , quantum mechanics , snail , biology
Model glycopeptides of the general formula Boc–Ala–Thr(G–D)–A 1 –A 2 –Leu–Leu–Lys(N)–Ala–OMe, where D = dansyl (dimethyl aminonaphthalenesulphonyl), G = glucosyl and N = naphthyl, while A 1 –A 2 = Ala–Leu or Aib–Aib, and denoted as D–G–Ala–N and D–G–Aib–N, respectively, were used to investigate glycoprotein–membrane interactions. They carry two fluorophores (D and N), covalently linked to the glucose ring and the lysine side chain, respectively, while the threonine side chain is O‐glycosylated. CD spectra in different solvent media suggest that both glycopeptides attain an ordered structure, possibly a helix‐like conformation. By combining FRET (fluorescence resonance energy transfer) experiments with molecular mechanics data, the most probable structures of both glycopeptides were built up, starting from both a right‐handed (rh) α‐ and 3 10 ‐helix. They were found to populate an α‐helical conformation, a result further confirmed by the very good agreement between theoretical and experimental quenching efficiency only observed when the backbone chain was in α‐helix. The association of D–G–Ala–N with model membranes (liposomes) was studied by CD, fluorescence decay, fluorescence anisotropy, and collisional quenching experiments. The binding does not alter the structural features of the peptide because the CD spectral patterns are unaffected by the association. The peptide orientation inside the phospholipidic bilayer is guided by the polar glucose molecule lying in the water phase. The insertion of the hydrophobic backbone chain into the membrane, seeing the probes only partially accessible from the external solution, is characterized by a significant degree of heterogeneity, an increase in vesicles size, and a relevant stabilizing effect on the membrane itself against rupture by methanol. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 44–56, 2002