Outstanding effects on antithrombin activity of modified TBA diastereomers containing an optically pure acyclic nucleotide analogue.

Herein, we report optically pure modified acyclic nucleosides as ideal probes for aptamer modification. These new monomers offer unique advantages in exploring the role played in thrombin inhibition by a single residue modification at key positions of the TBA structure.

Old and new targets for innovative antimalarial compounds: the different strategies of the Italian Malaria Network.

Clinical treatment-failures to affordable drugs encouraged new investigation for discovery and development of new prophylactic and therapeutic interventions against malaria. The Drug Discovery Cluster (DDcl) of the Italian Malaria Network gathers several highly integrated and complementary laboratories from different Italian Institutions to identify, synthesise, screen in vitro and in vivo new antimalarial molecules directed against the intraerythrocytic stage of P. falciparum parasites and/or with transmission blocking activity to select lead compounds for further development. Complementary research activities, both in vitro and in the clinics, aim at investigating the pathogenetic mechanisms of severe malaria anaemia and the different manifestations of the disease in malaria-HIV co-infected patients to identify new therapies and improve survival.

Solution conformation of a potent cyclic analogue of tuftsin: low- temperature nuclear magnetic resonance study in a cryoprotective mixture.

Tuftsin, a linear tetrapeptide (Thr-Lys-Pro-Arg), corresponding to the sequence 289-292 of the heavy chain of leukokinin, has been the object of intensive SAR studies during the past 30 years, owing to its numerous biological activities and to the possibility of generating a novel anticancer drug. A cyclic tuftsin analogue, c-[T-K-P-R-G], has biological activity 50 times higher than that of the parent linear peptide. Here we present a conformational study of c-[T-K-P-R-G] based on NMR data in a cryoprotective DMSO/water mixture. The preferred conformation is a type VIa turn centered on the K-P residues. The orientation of the side chains of the two basic residues (K and R) may represent the essential feature of the bioactive conformation of tuftsin. A possible role of tuftsin as a DNA binding motif is suggested by the similarity of the bioactive conformation of c-[T-K-P-R-G] and of the beta-turn conformation proposed by Suzuki for the [T,S]-P-K-R motif.

Characterization of the 1H-cyclopentapyrimidine-2,4(1H,3H)-dione derivative (S)-CPW399 as a novel, potent, and subtype-selective AMPA receptor full agonist with partial desensitization properties.

(S)-CPW399 (2b) is a novel, potent, and subtype-selective AMPA receptor full agonist that, unlike (S)-willardiine and related compounds, in mouse cerebellar granule cells, stimulated an increase in [Ca(2+)](i), and induced neuronal cell death in a time- and concentration-dependent manner. Compound 2b appears to be a weakly desensitizing, full agonist at AMPA receptors and therefore represents a new pharmacological tool to investigate the role of AMPA receptors in excitotoxicity and their molecular mechanisms of desensitization.

Shape-dependent effects in a series of aromatic nitro compounds acting as mutagenic agents on S. typhimurium TA98.

The steric properties modulating the mutagenic activity on S. typhimurium TA98 of a set of nitroaromatic compounds have been investigated using the CoMFA method. In addition to steric probe-ligand interaction energies, the overall lipophilicity and the energy of the lowest occupied molecular orbital have been employed as molecular descriptors.

Construction of a model of the Candida albicans lanosterol 14-alpha-demethylase active site using the homology modelling technique.

On the basis of all hitherto known P450 X-ray structures and applying standard homology modelling procedures a three-dimensional model of the lanosterol-14 alpha-demethylase active site was constructed. The modelled active site nicely hosts the natural substrate lanosterol and the substrate-enzyme complex displayed stability in a 70 ps molecular dynamics simulation. The importance of Thr 122 of lanosterol 14 alpha-demethylase for hydrogen bond formation with the 3-hydroxyl group of lanosterol was found to be a characteristic feature of the interaction geometry.

Conformational studies on a synthetic C-terminal fragment of the alpha subunit of G(S) proteins.

It has recently been reported that synthetic peptides corresponding to the C-terminal sequence of G alpha, can be used to study the molecular mechanisms of interaction between this protein and G protein coupled receptors (Hamm et al., Science, 1988, Vol. 241, pp. 832-835). A conformational analysis on a 11 amino acids peptide from the G alpha(S) C-terminus, G alpha(S)(384-394) (H-QRMHLRQYELL-OH), was performed by nmr spectroscopy and molecular modeling methods. Two-dimensional nmr spectra, recorded in hexafluoroacetone/water, a mixture with structure stabilizing properties, showed an unusually high number of nuclear Overhauser effects, forming significative pattern to the drawing of a secondary structure. Conformations consistent with experimental NOE distances were obtained through molecular dynamics and energy minimization methods. These calculations yielded two stable conformers corresponding to an alpha-turn and a type III beta-turn involving the last five C-terminal residues. Interestingly, the alpha-turn conformation was found to overlap with good agreement the crystallographic structure of the same fragment in the G alpha(S) protein.

Novel and potent tacrine-related hetero- and homobivalent ligands for acetylcholinesterase and butyrylcholinesterase.

Based upon synthetic and biochemical results, a novel and potent tacrine analogue and heterobivalent analogues of tacrine, were designed. The role played by the amino groups of homo- and heterobivalent ligands in the interaction with the peripheral and catalytic sites of AChE and BuChE were investigated. The syntheses of these materials together with the results of AChE/BuChE inhibition assays are detailed.

Pyrrolo-1,5-benzoxazepines induce apoptosis in chronic myelogenous leukemia (CML) cells by bypassing the apoptotic suppressor bcr-abl.

Expression of the transforming oncogene bcr-abl in chronic myelogenous leukemia (CML) cells is reported to confer resistance against apoptosis induced by many chemotherapeutic agents such as etoposide, ara-C, and staurosporine. In the present study some members of a series of novel pyrrolo-1,5-benzoxazepines potently induce apoptosis, as shown by cell shrinkage, chromatin condensation, DNA fragmentation, and poly(ADP-ribose) polymerase (PARP) cleavage, in three CML cell lines, K562, KYO.1, and LAMA 84. Induction of apoptosis by a representative member of this series, PBOX-6, was not accompanied by either the down-regulation of Bcr-Abl or by the attenuation of its protein tyrosine kinase activity up to 24 h after treatment, when approximately 50% of the cells had undergone apoptosis. These results suggest that down-regulation of Bcr-Abl is not part of the upstream apoptotic death program activated by PBOX-6. By characterizing the mechanism in which this novel agent executes apoptosis, this study has revealed that PBOX-6 caused activation of caspase 3-like proteases in only two of the three CML cell lines. In addition, inhibition of caspase 3-like protease activity using the inhibitor z-DEVD-fmk blocked caspase 3-like protease activity but did not prevent the induction of apoptosis, suggesting that caspase 3-like proteases are not essential in the mechanism by which PBOX-6 induces apoptosis in CML cells. In conclusion, this study demonstrates that PBOX-6 can bypass Bcr-Abl-mediated suppression of apoptosis, suggesting an important potential use of these compounds in the treatment of CML.

Pyrrolo-1,5-benzoxazepines: a new class of apoptotic agents.

Some members of a series of novel pyrrolo-1,5-benzoxazepines (PBOXs) potently induce apoptosis in a number of human cancerous cell lines including HL-60 cells and the drug-resistant chronic myelogenous leukaemia cell line, K562. The apoptotic induction seems to be independent of the mitochondrial peripheral-type benzodiazepine receptor (PBR), which binds these PBOXs with high affinity, due to a lack of correlation between their affinities for the receptor and their apoptotic potencies and their high apoptotic activity in PBR-deficient cells. PBOX-6, a potent member of the series, induces a transient activation of c-Jun N-terminal kinase (JNK) in a dose-dependent manner, which correlates with induction of apoptosis. Expression of a cytoplasmic inhibitor of the JNK signal transduction pathway, Jip-1, prevents JNK activity and significantly reduces the extent of apoptosis induced by PBOX-6. This demonstrates the requirement for JNK in the cellular response to this apoptotic agent. In addition, PBOX-6 activates caspase-3-like proteases in K562 and HL-60 cells. The caspase-3 inhibitor, Z-Asp-Glu-Val-Asp-fluoromethylketone (z-DEVD-fmk), blocks caspase-3-like protease activity in both cell types but only prevents PBOX-6-induced apoptosis in HL-60 cells, suggesting that the requirement for caspase-3-like proteases in the apoptotic pathway is dependent on the cell type.