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O Pieroni

Publications and source records attributed to O Pieroni.

27 records · Page 2Linked to original sources
PubMed1977

Asymmetric hydrogenation of unsaturated peptides.

Eleven unsaturated peptides, containing one or two dehydro-phenylalanyl (dehydro-Phe) residues and a C-terminal L-amino acid have been hydrogenated in the presence of palladium-on-charcoal. Hydrolysis of the saturated peptides thus obtained gave optically active phenylalanine showing the occurrence of asymmetric induction during the hydrogenation. Both mono-unsaturated dipeptides and doubly unsaturated tripeptides with L-Glu, L-Leu and L-Val as chiral end-group afforded L-Phe in 40-50% optical yield. In the case of the tripeptide N-acetyl-(dehydro-Phe)-(dehydro-Tyr)-L-Glu the asymmetric induction was higher (70%) for the unsaturated residue which is farther from the chiral end-group along the peptide chain. The results are discussed on the bases of Prelog rule and the rigid dissymmetric conformation of the dehydropeptides in solution.

Amino Acids↗
PubMedDate not supplied

3(10)-Helices, helix screw sense and screw sense reversal in the dehydro-peptide Boc-Val-delta Phe-Gly-delta Phe-Val-OMe.

The pentapeptide Boc-Val-delta Phe-Gly-delta Phe-Val-OME, containing two dehydro-phenylalanine (delta Phe) residues, has been synthesized and its structure investigated. In the crystalline state, the molecule adopts a right-handed 3(10)-helical conformation stabilized by two intramolecular hydrogen bonds between CO of Val1 and NH of delta Phe4, and between CO of delta Phe2 and NH of Val5, respectively. NMR measurements are consistent with the presence of 3(10)-helical structures also in acetonitrile and dimethylsulphoxide solution: the distances between backbone protons estimated from NOE connectivities are in overall agreement with those observed in the solid state; the chemical shifts of the amide protons show the smaller temperature coefficients for the NHs that in solid state are involved in intramolecular hydrogen bonds. The CD spectra in acetonitrile, chloroform, methanol and dimethylsulphoxide display exciton couplets of bands corresponding to the delta Phe electronic transition at 280 nm; the sign of the bands is consistent with the presence of helical structures having a prevalent left-handed screw sense. Addition of 1,1,1,3,3,3-hexafluoro-propan-2-ol gives rise to the gradual appearance of a couplet of opposite sign, suggesting the helix reversal from left-handed sense to right-handed sense. The conformational behaviour is discussed on the basis of the specific sequence of the peptide.

Circular Dichroism↗
PubMedDate not supplied

[Fukuyama-type congenital muscular dystrophy with the presence of ocular anomalies].

The authors report a case with Fukuyama type congenital muscular dystrophy (FCMD) and severe ocular abnormalities. Muscular dystrophy was confirmed by EMG, high muscle enzyme value and muscular biopsy. Computed tomography (CT) of the brain at 15 months of life showed mild central and cortical atrophy. Repeated CT scans at 22 and 32 months showed progressive character of the atrophy, with preservation of the cerebellar areas and the central grey matter only. Ophthalmologist examination revealed nystagmus, severe visual deficit, optic nerve atrophy and irregular color of the retina, especially in the peripheric areas. Electroretinography (ERG) was normal, cortically evoked visual responses (PEV) were absent. The association of congenital muscular dystrophy with brain changes and ocular abnormalities were found in FCMD, muscle-eye-brain disease (MEB) and Walker-Walburg syndrome (WWS). Our report, according to the recent literature, suggests that ocular lesions are caused by the same mechanism that provokes the central nervous system anomalies. It is probably of genetic origin: FCMD, MEB and WWS could be development abnormalities with a continual spectrum of disease severity.

Brain↗