Improved PRESS sequence for lactate detection in the human vitreous body

in Proceedings of the International Society for Magnetic Resonance in Medicine (2006), 14

Guanidinium chloride denaturation of the dimeric Bacillus licheniformis Blal repressor highlights an independent domain unfolding pathway

in Biochemical Journal (2004), 384(Pt 1), 179-190

The Bacillus licheniformis 74911 BlaI repressor is a prokaryotic regulator that, in the absence of a P-lactam antibiotic, prevents the transcription of the blaP gene, which encodes the BlaP beta-lactamase ... [more ▼]

The Bacillus licheniformis 74911 BlaI repressor is a prokaryotic regulator that, in the absence of a P-lactam antibiotic, prevents the transcription of the blaP gene, which encodes the BlaP beta-lactamase. The BlaI repressor is composed of two structural domains. The 82-residue NTD (N-terminal domain) is a DNA-binding domain, and the CTD (C-terminal domain) containing the next 46 residues is a dimerization domain. Recent studies have shown the existence of the monomeric, dimeric and tetrameric forms of BlaI in solution. In the present study, we analyse the equilibrium unfolding of BlaI in the presence of GdmCl (guanidinium chloride) using different techniques: intrinsic and ANS (8-anilinonaphthalene-1-sulphonic acid) fluorescence, far- and near-UV CD spectroscopy, cross-linking, analytical ultracentrifugation, size exclusion chromatography and NMR spectroscopy. In addition, the intact NTD and CTD were purified after proteolysis of BlaI by papain, and their unfolding by GdmCl was also studied. GdmCl-induced equilibrium unfolding was shown to be fully reversible for BlaI and for the two isolated fragments. The results demonstrate that the NTD and CTD of BlaI fold/unfold independently in a four-step process, with no significant cooperative interactions between them. During the first step, the unfolding of the Blal CTD occurs, followed in the second step by the formation of an 'ANS-bound' intermediate state. Crosslinking and analytical ultracentrifugation experiments suggest that the dissociation of the dimer into two partially unfolded monomers takes place in the third step. Finally, the unfolding of the Blal NTD occurs at a GdmCI concentration of approx. 4 M. In summary, it is shown that the Blal CTD is structured, more flexible and less stable than the NTD upon GdmCI denaturation. These results contribute to the characterization of the Blal dimerization domain (i.e. CTD) involved in the induction process. [less ▲]

Solution structural study of BlaI: Implications for the repression of genes involved in beta-lactam antibiotic resistance

in Journal of Molecular Biology (2003), 333(4), 711-720

Solution structural study of BlaI: implications for the repression of genes involved in beta-lactam antibiotic resistance.

in Journal of Molecular Biology (2003), 333(4), 711-20

beta-Lactamase and penicillin-binding protein PBP2' mediate staphylococcal resistance to beta-lactam antibiotics, which are otherwise highly clinically effective. Two repressors (BlaI and MecI) regulate ... [more ▼]

beta-Lactamase and penicillin-binding protein PBP2' mediate staphylococcal resistance to beta-lactam antibiotics, which are otherwise highly clinically effective. Two repressors (BlaI and MecI) regulate expression of these inducible proteins. Here, we present the first solution structure of the 82 amino acid residue DNA-binding domain of Bacillus licheniformis BlaI which is very similar in primary sequence to the medically significant Staphyloccocal BlaI and MecI proteins. This structure is composed of a compact core of three alpha-helices and a three-stranded beta-sheet typical of the winged helix protein (WHP) family. The protein/DNA complex was studied by NMR chemical shift comparison between the free and complexed forms of BlaI. Residues involved in DNA interaction were identified and a WHP canonical model of interaction with the operators is proposed. In this model, specific contacts occur between the base-pairs of the TACA motif and conserved amino acid residues of the repressor helix H3. These results help toward understanding the repression and induction mechanism of the genes coding for beta-lactamase and PBP2'. [less ▲]

Ent-Trachyloban-3beta-ol, a new cytotoxic diterpene frm Croton zambesicus

in Planta Medica (2002), 68

The dichloromethane extract of leaves of Croton Zambesicus (Euphorbiaceae) showing in vitro cytotoxicity against huma cervix carcinoma cells was investigated in order to identify its active compounds. A ... [more ▼]

The dichloromethane extract of leaves of Croton Zambesicus (Euphorbiaceae) showing in vitro cytotoxicity against huma cervix carcinoma cells was investigated in order to identify its active compounds. A bio-guided fractionation by HSCCC followed by MPLC led us to isolate a trachylobane diterpene, ent-trachyloban-3beta-ol, with cytotoxic properties (IC50 on HeLa cells = 7.3 ùg/ml). This is the first report on the cytotoxicity of a trachylobane diterpene. [less ▲]

Cytotoxic aporphine alkaloids from Cassytha filiformis L

Poster (2001)

New Antimalarial and Cytotoxic Sungucine Derivatives from Strychnos Icaja Roots

in Planta Medica (2000), 66(3), 262-9

Reinvestigation of Strychnos icaja Baillon resulted in the isolation of vomicine, isostrychnine and of three new sungucine derivatives, named isosungucine (8), 18-hydroxy-sungucine (9) and 18-hydroxy ... [more ▼]

Reinvestigation of Strychnos icaja Baillon resulted in the isolation of vomicine, isostrychnine and of three new sungucine derivatives, named isosungucine (8), 18-hydroxy-sungucine (9) and 18-hydroxy-isosungucine (10). They were identified by detailed spectroscopic methods. The complete 1H- and 13C-NMR study of sungucine was also realized. Some of these compounds were highly active against Plasmodium falciparum in vitro and more particularly against the chloroquine-resistant strain. Compound 10 showed a selective antiplasmodial activity, with > 100-fold greater toxicity towards Plasmodium falciparum, relative to cultured human cancer cells (KB and HeLa lines) or fibroblasts (WI38). [less ▲]

Development of a parenteral and of an oral formulation of albendazole with cyclodextrins

in STP Pharma Sciences (1999), 3

L'albendazole est une dérivé benzimidazole à large spectre d'activité contre les parasites helminthiques de l'homme et de l'animal. L'albendazole est très faiblement soluble dans l'eau. Il a été démontré ... [more ▼]

L'albendazole est une dérivé benzimidazole à large spectre d'activité contre les parasites helminthiques de l'homme et de l'animal. L'albendazole est très faiblement soluble dans l'eau. Il a été démontré que les cyclodextrines sont capables de former des complexes d'inclusion avec l'albendazole et d'en augmenter la solubilité. La solubilité aqueuse de l'albendazole est dépendante du pH. Le but de ce travail est d'étudier l'influence combinée des cyclodextrines et de différents acides sur la solubilité de l'albendazole. Il a été démontré qu'il existe un véritable effet synergique entre les cyclodextrines et les différents acides. L'utilisation combinée d'hydroxypropyl-b-cyclodextrine (200 mM) et d'acide lactique ou acide citrique (50 mM) permet de dissoudre plus de 1 mg/ml d'albendazole. Des études RMN ont démontré l'inclusion de l'albendazole dans la b-cyclodextrine en milieu acide. Ces résultats montrent qu'il est possible de réaliser une solution injectable et une solution orale d'albendazole grâce aux cyclodextrines. [less ▲]

Development of a non-surfactant parenteral formulation of miconazole by the use of cyclodextrins

in International Journal of Pharmaceutics (1998), 169

Miconazole is an antimycotic drug exhibiting a very poor water solubility (B1.03 mg:ml). It has been shown that cyclodextrins (CDs) are able to form inclusion complexes with miconazole and that they are ... [more ▼]

Miconazole is an antimycotic drug exhibiting a very poor water solubility (B1.03 mg:ml). It has been shown that cyclodextrins (CDs) are able to form inclusion complexes with miconazole and that they are able to increase its aqueous solubility. Miconazole is a weak base whose solubility depends of the pH. The purpose of this study was to investigate the influence of both CDs and different acids on the solubility of miconazole. It was found that a synergistic effect existed between CDs and different acids. The combination of hydroxypropyl-bCD (HP-bCD) (100 mM) or sulfobutylether 7-bCD (SBE7-bCD) (50 mM) and lactic acid (50 mM) allowed to dissolve more than 10 mg of miconazole per ml. NMR studies confirmed the formation of an inclusion complex miconazole–CD in an acidic medium. It was also shown by the NMR studies that the complex formed was a 1:1 complex. These results demonstrate that it is possible to develop a parenteral aqueous solution of miconazole without surfactant. [less ▲]

Study of the Influence of Both Cyclodextrins and L-Lysine on the Aqueous Solubility of Nimesulide; Isolation and Characterization of Nimesulide-L-Lysine-Cyclodextrin Complexes

in Journal of Pharmaceutical Sciences (1997), 86(4), 475-80

Nimesulide is a nonsteroidal antiinflammatory drug that exhibits a very poor water solubility (0.01 mg.mL-1). A nimesulide-beta-cyclodextrin complex prepared according to patent application WO 94/ 02177 ... [more ▼]

Nimesulide is a nonsteroidal antiinflammatory drug that exhibits a very poor water solubility (0.01 mg.mL-1). A nimesulide-beta-cyclodextrin complex prepared according to patent application WO 94/ 02177 has an aqueous solubility of approximately 16 mg.mL-1 of nimesulide. A nimesulide-L-lysine salt has also been prepared and increases the aqueous solubility of nimesulide to approximately 5.0-7.5 mg.mL-1. The purpose of the present study was to investigate the interaction of both cyclodextrins and L-lysine on the aqueous solubility of nimesulide. Nimesulide-L-lysine-beta- or gamma-cyclodextrin complexes were prepared by spray-drying. The inclusion of the nimesulide-L-lysine salt into the cyclodextrin cavity was confirmed by differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy. These complexes offered remarkable aqueous solubility. The incorporation of nimesulide in a nimesulide-L-lysine-beta-cyclodextrin complex increased its water solubility by a factor of 10 at pH 1.5 (0.050 mg.mL-1 for the complex versus 0.005 mg.mL-1 for nimesulide), 160 at pH 6.8 (2.373 mg.mL-1 for the complex versus 0.015 mg.mL-1 for nimesulide), and 3600 in purified water (36.400 mg.mL-1 for the complex versus 0.01 mg.mL-1 for nimesulide). [less ▲]