Biomedical subjects

B Di Blasio

Publications and source records attributed to B Di Blasio.

At least 19 recordsLinked to original sources

PubMed2005

Primary chemotherapy in operable breast carcinoma comparing CMF (cyclophosphamide, methotrexate, 5-fluorouracil) with an anthracycline-containing regimen: short-term responses translated into long-term outcomes.

BACKGROUND: The role of anthracyclines has been extensively studied in adjuvant chemotherapy, but much less in the primary chemotherapy of early breast carcinoma. This study, comparing CMF (cyclophosphamide, methotrexate, 5-fluorouracil) with the rotational anthracycline-containing regimen CMFEV (CMF plus epirubicin and vincristine) administered as primary chemotherapy, demonstrated a significant increase in clinical complete response in premenopausal women. We report the long-term results. PATIENTS AND METHODS: Two hundred and eleven patients with stage I or II palpable breast carcinoma and a tumour diameter of >2.5 cm were randomised to receive CMF or CMFEV for four cycles before surgery. After surgery, the patients in both arms received adjuvant CMF for three cycles. RESULTS: In the study population as a whole, there was a non-significant 20% reduction in mortality and relapse rates in the CMFEV arm. However, the effect of the experimental regimen was only found in premenopausal patients, especially in terms of relapse-free survival (P=0.07) and locoregional relapse-free survival (P=0.0009), thus mirroring the effect on response rates. After 10 years, the proportions of premenopausal patients free from locoregional relapse as a first event in the CMF and CMFEV groups were 68% and 97%, respectively. No relevant differences were found in postmenopausal patients. CONCLUSION: The overall results of this study showed that the greater activity of the experimental anthracycline-containing combination over CMF as primary chemotherapy in premenopausal patients translated into long-term effects in the same subgroup.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2000

Solid state structural analysis of the cyclooctapeptide cyclo- (Pro1-Pro-Phe-Phe-Ac6c-Ile-D-Ala-Val8).

A solid state analysis of the cyclic octapeptide c(-Pro(1)-Pro-Phe-Phe-Ac(6)c-Ile-D-Ala-Val(8)-) (C8-CLA), containing the Pro-Pro-Phe-Phe sequence, followed by the bulky helicogenic C(alpha,alpha)-dialkylated 1-aminocyclohexane-1-carboxylic acid (Ac(6)c) residue and a D-Ala residue in position 7, has been carried out by x-ray diffraction. The crystals, grown from a DMSO solution, are monoclinic, space group P2(1) with a = 13.458(3) A, b = 19. 404(5) A, c = 21.508(4) A, and beta = 90.83(6) degrees, with two independent cyclic molecules in the asymmetric unit, two DMSO molecules, and three water molecules. The structure has been solved using the half and bake procedure by Sheldrick, and refined to final R1 and wR2 indices of 0.0613 and 0.1534 for 9867 reflections with I > 2sigma(I). This cyclic peptide, a deletion analogue of the naturally occurring cyclic nonapeptide cyclolinopeptide A [c(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val), CLA] has been designed to study the influence of the ring size reduction on the conformational behavior of CLA and more in general to obtain structural information on asymmetric cyclic octapeptides. The compound exhibits, in the solid state, a "banana-twisted" conformation with a cis peptide bond located between the two proline residues. Five intramolecular H bonds stabilize the structure: one type VIa beta-turn, two consecutive type III/I beta-turns, one gamma-turn, and one C(16) bend. The structure has also been compared with either the solution structure previously reported by us and obtained by nmr and computational analysis, and with solid state structural data reported in the literature on cyclic octapeptides.

Amino Acid Sequence↗

PubMed1999

Three new active cisplatin-containing combinations in the neoadjuvant treatment of locally advanced and locally recurrent breast carcinoma: a randomized phase II trial.

We designed three new four-drug cisplatin-containing combinations and evaluated their activity in a randomized phase II study including patients with locally advanced (stage III) and locally recurrent breast carcinoma. All combinations included methotrexate (M) on day 1 and cisplatin (P) on day 2 (MVAC-like combinations) and differed from one another by the addition of Epirubicin (Epi), Vincristine (V), Etoposide (E), Mitomycin (Mi). Based on the administered agents, they were named MPEMi, MPEpiE, MPEpiV. The combinations were randomly assigned to 101 patients, 57 with locally advanced and 44 with locally recurrent breast carcinoma. Response was evaluated after 4 cycles. The complete response (CR) rates were 7% and 43% and the CR plus partial response (PR) rates were 84% and 89% in locally advanced and in locally recurrent disease, respectively. In locally advanced disease, a pathologic CR (pCR) was assessed in seven of 57 patients (12%). There were no significant differences among the three combinations. The toxicities were at times severe, but generally tolerable, as demonstrated by the high cumulative doses of the drugs received by the patients. In conclusion, these three innovative chemotherapy regimens induced high CR plus PR rates in the neoadjuvant treatment of stage III and of locally recurrent breast carcinoma, and a high rate of pCR in stage III disease. These regimens warrant testing in phase III trials.

Adult↗

PubMed1999

Mature results of a prospective randomized trial comparing a three-weekly with an accelerated weekly schedule of cisplatin in advanced ovarian carcinoma.

In a retrospective analysis of a series of clinical trials by Levin and Hryniuk in 1987, the average relative dose intensity of first-line chemotherapy for advanced ovarian cancer correlated significantly with clinical response and survival, and cisplatin was the only drug for which the outcome correlated with the individual drug relative dose intensity. There was a need to test whether and to what extent this evidence would be confirmed in a prospective evaluation. In this study 101 patients with advanced ovarian carcinoma were randomized to receive the same total dose of cisplatin but at the conventional 3-weekly schedule (CTWS) (100 mg/m2 every 3 weeks for six cycles) (51 patients) or at an experimental accelerated weekly schedule (AWS) (100 mg/m2 every week for two triplets of three cycles separated by a 5-week interval) (50 patients). To benefit from a multidrug regimen at the same extent, patients in both arms sequentially received four cycles of doxorubicin and cyclophosphamide. The median follow-up period of this study is 9.7 years. In 42 and 40 patients of the two arms having evaluable response, the clinical complete response rates to cisplatin were 14% and 22% and the complete plus partial response rates were 48% and 55% in the CTWS and in the AWS arm, respectively. These differences were not statistically significant. However, the survival curves were similar during the first 2 years but clearly diverged thereafter in favor of the AWS arm (p = 0.07). At 5 years, 12% and 30% of the patients were still alive in the CTWS and in the AWS arm, respectively. Hematologic toxicity was not relevant in either arm of the study. Nonhematologic toxicity, especially ototoxicity, was substantial and significantly higher in the AWS arm. Although statistically nonsignificant, this AWS regimen of cisplatin is associated with long-term better survival compared to the CTWS regimen in advanced ovarian carcinoma. This accelerated approach administering cisplatin should be further investigated, especially in patients with low residual disease after primary surgery.

Adult↗

PubMed1998

Structure and dynamics of elastin building blocks. Boc-LG-OEt, Boc-VGG-OH.

Short di- and tripeptides such as Boc-LG-OEt, Boc-VG-OEt and Boc-VGG-OH, corresponding to abundant repetitive sequences in elastin, have been extensively studied both in solid state, by X-ray diffraction, and in solution by circular dicroism and nuclear magnetic resonance. Furthermore, theoretical procedures such as simulated annealing and molecular dynamics were also performed on these peptides. In general, the results indicate that no one single structure (be folded or extended) could be representative for these sequences in the protein, but rather that a multiplicity of interconverting conformers, ranging from folded to extended structures, should be considered. In any case, these structures, e.g. beta-turns, polyglycine II and beta-conformations, are those previously suggested to participate to conformational equilibria of elastin.

Circular Dichroism↗

PubMed1996

Synthesis and structural characterization of 6I,6II-diamino-6I,6II-dideoxy-cyclomaltoheptaose, a difunctionalized beta-cyclodextrin.

6I,6II-Diamino-6I,6II-dideoxy-cyclomaltoheptaose was prepared using the regioselective procedure described by Tabushi. The difunctionalized beta-cyclodextrin crystallizes as hexadecahydrate in the orthorhombic space group P2(1)2(1)2(1), with a = 11.395(3), b = 32.989(9), c = 17.560(5) A, V = 6601 A3, Z = 4. The structure was solved by molecular replacement techniques using the program PATSEE and was refined to a conventional final R = 0.058 for the 5031 observed reflections with I > or = 3 sigma(I). The beta-CD macrocycle presents only slight differences with respect to uncomplexed hydrated or methylated beta-CD. The macrocycle structure maintains an approximate seven-fold symmetry. The round shape of the cyclodextrin ring is stabilized by intramolecular O-H ... O H-bonds between the secondary hydroxyl groups of neighbouring glucose residues. Along the a axis, the beta-CD molecules are arranged in columns; the macrocycles form a herring-bone pattern, so that the cavity of each beta-CD molecule is closed at each end by neighbouring molecules. The macrocycles are directly linked to each other by H-bonds involving either primary and secondary hydroxyl or amino groups of symmetry-related molecules. The resulting layers are connected to each other by a dense intermolecular hydrogen-bond network, in which solvent molecules participate.

Carbohydrate Sequence↗

PubMed1996

Solution and solid state structure of an aib-containing cyclodecapeptide inhibiting the cholate uptake in hepatocytes.

The conformational analysis of synthetic cyclodecapeptide c(Pro-Phe-phe-Aib-Leu)2 related to the cyclolinopeptide A, in the solid state and solution, has been carried out by x-ray diffraction and nmr spectroscopy. The structure of the monoclinic form obtained from methanol [a = 11.351 (5) A, b = 27.455 (2) A, c = 12.716 (8) A, beta = 99.65 (3) degrees; space group P2(1); Z = 2] shows the presence of six intramolecular NH...CO hydrogen bonds, with formation of four turns (three of type I and one of type III) and two C16 ring structures. All peptide units are trans. The solution structure, as found by nmr, indicates that, at room temperature, the peptide is conformationally homogeneous; the structure determined is perfectly symmetrical and topologically similar to that found in the solid state. The cyclodecapeptide exhibits similar biological activity to cyclolinopeptide A.

Animals↗

PubMed1995

[Aib5,6-D-Ala8]-cyclolinopeptide A, grown from a benzene/acetonitrile mixture.

cyclo-(Prolyl-prolyl-phenylalanyl-phenylalanyl- alpha-aminoisobutyryl-alpha-aminoisobutyryl-isoleucyl-D-alan yl-valyl) ([Aib5,6-D-Ala8]-cyclolinopeptide A), grown from benzene/acetonitrile mixture, crystallizes with one acetonitrile and two water molecules. The molecular structure is almost identical to that obtained from methanol/water. The dimension of the solvent channels found in these structures is reduced in the present one, but the intramolecular hydrogen-bond pattern is preserved. The Pro1-Pro2 peptide unit is cis (omega = 8 degrees); all others are trans.

Acetonitriles↗

PubMed1995

Conformational studies of heterochiral peptides with diastereoisomeric residues: crystal and molecular structures of linear dipeptides derived from leucine, isoleucine, and allo-isoleucine.

The x-ray diffraction analyses of three N- and C-terminally blocked L,D dipeptides, namely t-Boc-D-Leu-L-Leu-OMe (1), t-Boc-L-Ile-D-aIle-OMe (2), and t-Boc-D-aIle-L-Ile-OMe (3) containing enantiomeric or diastereomeric amino acid residues have been carried out. The structures were determined by direct methods and refined anisotropically to final Rf actors of 0.077, 0.058, and 0.072 for (1), (2), and (3), respectively. Peptides 1-3 all assume a similar U-shaped structure with phi and psi torsion angles corresponding to one of the possible calculated minimum energy regions (regions E and G for L residues, and F*, D* and H* for D residues). The peptide backbones of 1-3 are almost superimposable [provided that the appropriate inversion of the chiral centers of (2) is made]. Side-chain conformations of Leu residues in peptide (1) are g- (tg-) for the L-Leu residue and the mirrored g+ (tg+) for the D-Leu residue; however, in peptides (2) and (3) the conformations of the isoconfigurational side chains of the Ile or allo-Ile residues are (g-t) t and (tg+) t for the L-Ile and the D-allo-Ile moieties, respectively. In all cases, these conformations correspond to the more populated conformers of beta-branched residues statistically found in crystal structures of small peptides. The results seem to indicate that, at least in short peptides with enantiomeric or diastereoisomeric residues, the change in chirality in the main-chain atoms perturbs the backbone conformation to a lesser extent and the side chain conformation to a greater extent.

Crystallography, X-Ray↗

PubMed1995

Bioactive peptides: conformational studies of [Tyr4] cyclolinopeptide A.

The solid state conformational analysis of [Tyr4] cyclolinopeptide A has been carried out by x-ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane-water mixture [alpha = 9.849 (5) A, b = 20.752 (4) A, c = 16.728 (5) A, beta = 98.83 (3) degrees, space group P21, Z = 2], shows the presence of five intramolecular N-H...O = C hydrogen bonds, with formation of one C17 ring structure, one alpha-turn (C13), one inverse gamma-turn (C7), and two beta-turns (C10, one of type III and one of type I). The Pro1-Pro2 peptide unit is cis (omega = 5 degrees), all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 A.

Amino Acid Sequence↗

PubMed1995

The polypeptide 3(10)-helix as a template for molecular recognition studies. Structural characterization of a side-chain functionalized octapeptide.

A N alpha-blocked, Aib-rich octapeptide methylamide containing two N omega-benzoylated L-Lys residues at positions 3 and 6 was synthesized by solution methods and fully characterized. A solution and crystal-state conformational analysis, performed by using FT-IR, 1H NMR, CD, and X-ray diffraction techniques, showed that the peptide is folded into a regular, right-handed 3(10)-helix stabilized by seven consecutive N-H...O=C intramolecular H-bonds of the beta-turn III type. The two benzamidobutyl L-Lys side chains, located on the same side of the helix after one complete turn, generate a cleft the minimal width of which was found to be 3.47 A.

Amino Acid Sequence↗

PubMed1995

Conformation and structure of linear peptides with regularly alternating L- and D-residues: structure of the blocked hexapeptide tert-butyloxycarbonyl-(D-alloisoleucyl-L-isoleucyl)3 methyl ester monohydrate.

Peptides with a regular sequence of enantiomeric residues (L and D) along the chain have received considerable attention because of their accessibility to unique conformations and because they are model compounds for the naturally occurring peptide gramicidin A, which shows monovalent cation selective transmembrane transport. The solid-state structure of the linear hexapeptide t-Boc-(D-alle-L-Ile)3-OMe has been determined by X-ray diffraction techniques and refined to a final R factor of 0.068. The molecule shows a bent U-shaped conformation stabilized by three intramolecular H-bonds of the N-H...O = C type: a type II beta-bend (4-->1 bend or C10 ring structure) with L-Ile2 and D-aIle3 at positions 2 and 3 of the bend, an alpha-turn (5-->1 bend or C13 ring structure) and a 1-->5 bend or C17 ring structure. The first two 10-membered and 13-membered bends are enclosed in the latter 17-membered hydrogen-bonded ring structure. This structural motif is common to hepta- and octa-peptide cyclic molecules, showing that ring closure is not required to achieve a particular topology in the molecular design of specific bended conformations.

Amino Acid Sequence↗

PubMed1995

The preferred solid-state conformation of (alpha Me)Trp peptides.

The two Z-L-Ala-DL-(alpha Me)Trp-NH2 diastereomeric dipeptides were synthesized from (Z-L-Ala)2(O) and H-DL-(alpha Me)Trp-NH2. The latter racemate, prepared by phase-transfer catalyzed alkylation of the N alpha-benzylidene derivative of alanine amide followed by acidic hydrolysis of the resulting Schiff base, was characterized by X-ray diffraction. The molecular and crystal structure of Z-L-Ala-L-(alpha Me)Trp-NH2, separated from its diastereomer by silica-gel column chromatography, was determined by X-ray diffraction analysis. Both independent molecules in the asymmetric unit of the dipeptide adopt a type-II beta-bend conformation. However, only the more regularly folded conformation of molecule B is stabilized by a 1<--4 C = O...H--N intramolecular H bond. The present results indicate that: (i) the C alpha-methylated (alpha Me)Trp residue is a strong beta-bend and helix former, and (ii) the relationship between (alpha Me)Trp chirality and helix screw sense tends to be opposite to that of protein amino acids. The implications for the use of the (alpha Me)Trp residue in designing conformationally restricted analogs of bioactive peptides are briefly discussed.

Amino Acid Sequence↗

PubMed1994

Bioactive peptides: solid state, solution and molecular dynamics studies of a cyclolinopeptide A-related cystinyl cyclopentapeptide.

The conformational analysis of [sequence: see text] the disulphide cyclopeptide-related cyclolinopeptide A, has been carried out by solid state methods using x-ray diffraction techniques, in solution by nmr, CD, ir spectroscopies, and by molecular dynamics (MD) analysis. The structure of the monoclinic form, obtained from ethanol (a = 11.303(2) A, b = 14.467(8) A, c = 12.355(2) A, beta(degree) = 109.40(1), space group P2(1), Z = 2) presents two transannular H bonds with the formation of one type VIa beta-turn involving the C = O of the urethane moiety and the Phe3 NH, and an intramolecular H bond between the C = O of urethane group and the Phe4 NH. In the solid state all the peptide bonds are in the trans configuration with the exception of a cis peptide bond occurring between the Cys1 and Pro2 residues; the linkage S-S assumes right-handed chirality. The conformational study in solution by nmr spectroscopy indicates that the peptide is very flexible and that some conformer families are present at room temperature both in polar and apolar solvents. CD studies confirm that this cyclic system tends to give rise to a complex mixture of quasi-isoenergetic conformations, favored by the flexibility of the disulphide bridge and by the isomerism of the Xxx-Pro bond. MD studies carried out in vacuo and in solution shows that the structure determined by solid state represents a energy minimum. All hydrogen bonds found in the crystalline state are correctly reproduced in vacuo and in solution simulations.

Amino Acid Sequence↗

PubMed1994

Defect peptide chemistry: perturbations in the structure of a homopentapeptide induced by a guest residue interrupting side-chain regularity.

The fully blocked pentapeptide Tfa-(Deg)2-L-Abu-(Deg)2-OtBu (Tfa: triflouroacetyl; Deg: C alpha, alpha-diethylglycine; Otbu: tert-butoxy) adopts in the crystal state a regular, right-handed 3(10)-helical structure stabilized by three N--H...O=C intramolecular 1 < 4 (or C10) H bonds, as determined by an x-ray diffraction analysis. However, a Fourier transform ir absorption and 1H-nmr study strongly supports the view that in deuterochloroform solution the four Deg residues at both termini of the peptide main chain are involved in successive, fully extended C5 forms. A comparison with the stable, fully developed, multiple C5 conformation of Tfa-(Deg)5-OtBu indicates that incorporation of an Abu guest residue, interrupting the side-chain uniformity of the host (Deg)5 homopeptide, while altering only marginally the conformation in a solvent of low polarity, is responsible for a dramatic perturbation of the crystal-state structure.

Amino Acid Sequence↗

PubMed1994

A crystal structure with features of an antiparallel alpha-pleated sheet.

A single-crystal x-ray diffraction analysis of Boc-L-Ala-D-aIle-L-Ile-OMe has been carried out. The analysis has shown (a) that the tripeptide molecules have in part an alpha-extended conformation, the torsion angles of the L-Ala and D-aIle residues being psi 1 = -75.1 degrees and psi 1 = -25.8 degrees and psi 2 = 67.3 degrees and psi 2 = 44.1 degrees, respectively, and (b) that the molecules are organized in rippled planes where they occur in relative antiparallel orientation linked together side by side by H bonds. This molecular organization of the tripeptide corresponds closely to that of an antiparallel alpha-pleated sheet, and likely constitutes the first example of a structure of this kind for which a characterization at the atomic level has been achieved. A molecular dynamics study has shown that the molecular conformation of the tripeptide in the crystalline state is determined primarily by intermolecular interactions.

Amino Acid Sequence↗

PubMed1994

Beta-alanine containing cyclic peptides with predetermined turned structure. V.

In the present paper we describe the synthesis, purification, single crystal x-ray analysis, and solution structural characterization by nmr spectroscopy, combined with restrained molecular dynamic simulations, of the cyclic hexapeptide cyclo-(Pro-Phe-beta-Ala-Phe-Phe-beta-Ala). The peptide was synthesized by classical solution methods and the cyclization of the free hexapeptide was accomplished in good yields in diluted methylenechloride solution using N,N-dicyclohexyl-carbodiimide. The compound crystallizes in the monoclinic space group P2(1) from methanol/ethyl acetate. The molecule adopts in the solid state a conformation characterized by cis beta-Ala6-Pro1 peptide bond. The alpha-amino acid residues are at the corner positions of turned structures. The Pro1-Phe2 segment is incorporated in a pseudo type I beta-turn, while Phe4-Phe5 is in a typical type I beta-turn. Assignment of all 1H and 13C resonances was achieved by homo- and heteronuclear two-dimensional techniques in dimethylsulfoxide (DMSO) solutions. The conformational analysis was based on interproton distances derived from rotating frame nuclear Overhauser effect spectroscopy spectra and homonuclear coupling constants. Restrained molecular dynamic simulation in vacuo was also performed to built refined molecular models. The molecule is present in DMSO solution as two slowly interconverting conformers, characterized by a cis-trans isomerism around the beta-Ala6-Pro1 peptide bond. This work confirms our expectations on the low propensity of beta-alanyl residues to be positioned at the corners of turned structure.

Amino Acid Sequence↗

PubMed1994

Mixed conformation in C alpha, alpha-disubstituted tripeptides: x-ray crystal structures of Z-Aib-Dph-Gly-OMe and Bz-Dph-Dph-Gly-OMe.

We report here the synthesis and molecular structure in the solid state of fully protected tripeptides containing C alpha, alpha-diphenylglycine (Dph), namely Z-Aib-Dph-Gly-OMe (Aib: C alpha, alpha-dimethylglycine) and Bz-Dph-Dph-Gly-OMe. The molecular conformation around the Dph residue, containing two bulky substituents, is fully extended, while the Aib residue, containing two smaller groups on the C alpha atom, adopts the typical 3(10)/alpha-helical conformation. Gly residues, without substituents on the C alpha atom, show different conformational preferences. Each residue seems to behave, from a conformational point of view, independently from the presence of the other residues, and thus mixed local conformations (folded and extended) are present in the crystals. The nonconventional peptide synthesis, using the Ugi reaction, is also reported.

Amino Acid Sequence↗