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Biomedical subjects

B Di Blasio

Publications and source records attributed to B Di Blasio.

61 records · Page 4Linked to original sources
PubMed1982

Randomized comparison of 5-FU alone or combined with mitomycin and cytarabine (MFC) in the treatment of advanced gastric cancer.

In a prospective randomized study, 53 patients with advanced gastric cancer previously untreated by chemotherapy were randomly assigned to treatment with 5-FU alone or combined with mitomycin and cytarabine (MFC). The response rate with MFC was higher (28%) than with 5-FU alone (21%). The difference, however, was not statistically significant. Median response duration was practically identical with 5-FU (16 weeks) and MFC (17 weeks). There was no difference in median survival between the two groups (39 and 43 weeks, respectively).

Aged↗
PubMed1981

Structure of N-acetyl-D-alanyl-D-alanine hydrate. An analogue of the COOH-terminal segment of peptidoglycan of bacterial cell walls.

The solid state conformational analysis of Ac-D-Ala-D-Ala-OH.H2O, carried out by infrared absorption and X-ray diffraction, has indicated that the molecules are not extended in a regular beta conformation, but rather that they are partially folded, the phi, psi torsional angles of the COOH-terminal residue in particular being in the region of the left-handed alpha helix of the Ramachandran map. The acetylamino and peptide groups ar found in the usual trans conformation, the latter, however, exhibiting a deviation from rigid planarity. Only intermolecular hydrogen bonds occur in the crystal state. The solution conformational analysis, performed by infrared absorption and CD, has revealed that the amount of intramolecular N--H ... O==C hydrogen-bonded folded forms, if any, should be extremely small, even in deuteriochloroform at high dilution. In water, solvated, unordered species largely predominate.

Bacteria↗
PubMedDate not supplied

Conformational characterization of the 1-aminocyclobutane-1-carboxylic acid residue in model peptides.

A series of N- and C-protected, monodispersed homo-oligopeptides (to the dodecamer level) from the small-ring alicyclic C alpha, alpha-dialkylated glycine 1-aminocyclobutane-1-carboxylic acid (Ac4c) and two Ala/Ac4c tripeptides were synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives Z-Ac4c-OH and Z2-Ac4c-OH, the tripeptides Z-(Ac4c)3-OtBu, Z-Ac4c-(L-Ala)2-OMe and Z-L-Ala-Ac4c-L-Ala-OMe, and the tetrapeptide Z-(Ac4c)4-OtBu were determined in the crystal state by X-ray diffraction. The average geometry of the cyclobutyl moiety of the Ac4c residue was assessed and the tau(N-C alpha-C') bond angle was found to be significantly expanded from the regular tetrahedral value. The conformational data are strongly in favour of the conclusion that the Ac4c residue is an effective beta-turn and helix former. A comparison with the structural propensities of alpha-aminoisobutyric acid, the prototype of C alpha, alpha-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n = 3, 5-8) is made and the implications for the use of the Ac4c residue in conformationally constrained peptide analogues are briefly examined.

Amino Acids↗
PubMedDate not supplied

Inversion of 3(10)-helix screw sense in a (D-alpha Me)Leu homo-tetrapeptide induced by a guest D-(alpha Me)Val residue.

The terminally blocked tetrapeptide pBrBz-[D-(alpha Me)Leu]2-D-(alpha Me)Val-D-(alpha Me)Leu-OfBu is folded in the crystal state in a left-handed 3(10)-helical structure stabilized by two consecutive 1<--4 C = O...H-N intramolecular H-bonds, as determined by X-ray diffraction analysis. A CD study strongly supports the view that this conformation is also that largely prevailing in MeOH solution. A comparison with the published conformation of pBrBz-[D-(alpha Me)Leu]4-OfBu indicates that incorporation of a single internal beta-branched (alpha Me)Val guest residue into the host homo-tetrapeptide from the gamma-branched (alpha Me)Leu residue is responsible for a dramatic structural perturbation, i.e. an inversion of the 3(10) screw sense from right to left-handed.

Amino Acid Sequence↗
PubMedDate not supplied

Preferred conformation of peptides rich in Ac8c, a medium-ring alicyclic C (alpha,alpha)-disubstituted glycine.

A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic C (alpha,alpha)-disubstituted glycine 1-aminocyclooctane-1-carboxylic acid (Ac8c), and two Ala/Ac8c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and 1H-NMR. The molecular structures of the amino acid derivative Z-Ac8c-OH, the dipeptide pBrBz-(Ac8c)2-OH and the tripeptide pBrBz-(Ac8c)3-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac8c-NHMe. Taken together, the results obtained strongly support the view that the Ac8c residue is an effective beta-turn and helix former. A comparison is also made with the conformational preferences of alpha-aminoisobutyric acid, the prototype of C (alpha,alpha)-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc with n = 3, 5-7) investigated so far. The implications for the use of the Ac8c residue in peptide conformational design are considered.

Amino Acids↗
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↗