Biomedical subjects

Luisa Bracci

Publications and source records attributed to Luisa Bracci.

23 records · Page 2Linked to original sources

PubMed2002

A branched peptide mimotope of the nicotinic receptor binding site is a potent synthetic antidote against the snake neurotoxin alpha-bungarotoxin.

We previously produced synthetic peptides mimicking the snake neurotoxin binding site of the nicotinic receptor. These peptide mimotopes bind the snake neurotoxin alpha-bungarotoxin with higher affinity than peptides reproducing native receptor sequences and inhibit toxin binding to nicotinic receptors in vitro; yet their efficiency in vivo is low. Here we synthesized one of the peptide mimotopes in a tetrabranched MAP form. The MAP peptide binds alpha-bungarotoxin in solution and inhibits its binding to the receptor with a K(A) and an IC(50) similar to the monomeric peptide. Nonetheless, it is at least 100 times more active in vivo. The MAP completely neutralizes toxin lethality when injected in mice at a dose compatible with its use as a synthetic antidote in humans. The in vivo efficacy of the tetrameric peptide cannot be ascribed to a kinetic and thermodynamic effect and is probably related to different pharmacokinetic behavior of the tetrameric molecule, with respect to the monomer. Our findings bring new perspectives to the therapeutic use of multimeric peptides.

Animals↗

PubMed2002

Metal ion complexation and folding of linear peptides.

A Linear peptide, GASYQDLG was synthesised and used as a model to evaluate the effects of nickel additions to increase the conformational stability. The NMR data obtained for the peptide and its histidyl derivative (H)(3)GASYQDLG(H)(3) suggest that in solution folded structures are present only for the H-tagged peptide-Ni(II) ion system. These results suggest that metal ions and additions of a double histidine tags of suitable length can be used as efficient tools to reduce peptide flexibility without other internal modifications. Synthesis of H-tagged analogs could offer a promising strategy for large-scale preparation of diagnostic tools and, in general, whenever more rigid molecular structures should be advisable.

Metals↗

PubMed2002

NMR structure of alpha-bungarotoxin free and bound to a mimotope of the nicotinic acetylcholine receptor.

A combinatorial library approach was used to produce synthetic peptides mimicking the snake neurotoxin binding site of nicotinic receptors. Among the sequences, which inhibited binding of alpha-bungarotoxin to muscle and neuronal nicotinic receptors, HRYYESSLPWYPD, a 14-amino acid peptide with considerably higher toxin-binding affinity than the other synthesized peptides, was selected, and the structure of its complex with the toxin was analyzed by NMR. Comparison of the solution structure of the free toxin and its complex with this peptide indicated that complex formation induced extensive conformational rearrangements mainly at finger II and the carboxy terminus of the protein. The peptidyl residues P10 and Y4 seemed to be critical for peptide folding and complex stability, respectively. The latter residue of the peptide strongly interacted with the protein by entering a small pocket delimited by D30, C33, S34, R36, and V39 toxin side chains.

Animals↗

PubMed2002

Peptide-protein interactions studied by surface plasmon and nuclear magnetic resonances.

The structural features of the complexes that alpha-bungarotoxin forms with three different synthetic peptides, mimotopes of the nicotinic acetylcholine receptor binding site, have been compared to the corresponding nuclear magnetic resonance (NMR) and surface plasmon resonance (SPR) data. For the considered peptides, the observed different affinities towards the toxin could not be accounted simply by static structural considerations. A combined analysis of the SPR- and NMR-derived dynamic parameters shows new correlations between complex formation and dissociation and the overall pattern of intramolecular and intermolecular nuclear Overhauser effects. These features could be crucial for a rational design of protein ligands.

Amino Acid Sequence↗

PubMed2002

NMR studies on Ni(II) induced cyclization of a histidine-tagged peptide.

A linear decapeptide, HGASYQDLGH, was synthesized and used as a model to evaluate the effect of nickel addition upon non-covalent backbone cyclization. The NMR data, obtained for the peptide in the presence of the metal ion, support the existence of predominant folded structures in solution, where the two His residues are maintained close to each other. These results suggest that insertion of even a single His residue at each peptide terminus can be used efficiently to reduce peptide flexibility without any backbone modification.

Amino Acid Sequence↗