Biomedical subjects

C Toniolo

Publications and source records attributed to C Toniolo.

184 records · Page 11Linked to original sources

PubMedDate not supplied

A second polymorph of a helical decapeptide.

A crystal-state structural analysis of the terminally blocked apolar decapeptide pBrBz-(Aib-L-Ala)5-OMe bis-dimethylsulfoxide solvate was performed by x-ray diffraction. The peptide molecules are basically alpha-helical with five 1<--5 C = O... H-N intramolecular H bonds. Near the C terminus the regularity of the alpha-helix is disrupted in favor of the formation of intramolecular H bonds of the 1<--4 (beta-bend) and 1<--6 (pi-bend) types. Differences in conformation, solvation and association with the published structure of the tetrahydrate decapeptide polymorph are discussed.

Chemical Phenomena↗

PubMedDate not supplied

Synthesis and conformational analysis of (alpha Me)Leu/Aib model peptides.

We have synthesized by solution methods and fully characterized a variety of (alpha Me)Leu/Aib model peptides to the octapeptide level. A solution conformational analysis was performed by using infrared absorption. 1H nuclear magnetic resonance, and circular dichroism. The crystal-state structures of Z-D-(alpha Me)Leu-(Aib)2-OtBu, pBrBz-(Aib)2-D-(alpha Me)Leu-(Aib)2-OtBu, and Ac-(Aib)2-D-(alpha Me)Leu-(Aib)2-OtBu monohydrate were solved by x-ray diffraction. The results indicate that the (alpha Me)Leu residue may be easily incorporated into beta-bends and 3(10)-helical structures, and suggest that this residue tends to induce a helix handedness opposite to that promoted by its unmethylated counterpart (Leu) of the same optical configuration.

Aminoisobutyric Acids↗

PubMedDate not supplied

(S)-C alpha-ethyl, C alpha-benzylglycine [(S)-(alpha Et)Phe] peptides fold in left-handed helical structures.

The first x-ray diffraction structure analysis of a C alpha-ethyl, C alpha-benzylglycine [(alpha Et)Phe]-containing peptide, N alpha-benzyloxycarbonyl-alpha-aminoisobutyryl-alpha-amino-isobutyr yl-(S)- C alpha-benzylglycyl-alpha-aminoisobutyric acid (methanol solvate), has been performed. In the crystal state the N alpha-protected tetrapeptide is folded in an incipient, left-handed 3(10)-helical structure. This finding confirms that the relationship between (alpha Et)Phe alpha-carbon chirality and screw sense of the helix that is formed is opposite to that exhibited by protein amino acids, including Phe.

Chemical Phenomena↗

PubMedDate not supplied

Crystallographic characterization of tryptophan-containing peptide 3(10)-helices.

The molecular and crystal structures of four peptides containing one L-Trp guest residue in Aib (alpha-aminoisobutyric acid or C alpha-methyl alanine) host oligopeptide chains have been determined by X-ray diffraction. The peptides are Z-Aib-L-Trp-Aib-OMe, Z-(Aib)2-L-Trp-Aib-OMe, Z-(Aib)3-L-Trp-Aib-OtBu and Boc-(Aib)3-L-Trp-Aib-OMe. Right-handed beta-turns and incipient and fully developed 3(10)-helices are formed in the crystal state by the tri-, tetra- and pentapeptides, respectively. The Trp residue is easily accommodated in these folded structures. The average geometry and preferred conformation for the Trp indolyl side chain are also discussed.

Crystallography, X-Ray↗