Crystallization of bothropstoxin II isolated from the venom of Bothrops jararacussu

A myotoxic phospholipase A(2), bothropstoxin II, which exhibits low hydrolytic activity, was crystallized and X-ray diffraction data were collected to a resolution of 2.2 Angstrom. Preliminary analysis reveals the presence of three molecules in the asymmetric unit. Copyright (C) 1996 Elsevier B.V. Ltd.

Fluorescence study of the interaction between metal ions and methyl methacrylate methacrylic acid copolymers in aqueous solutions: thallium(I), calcium(II), and terbium(III)

The binding of the cations thallium(I), calcium(II) and terbium(III) to methyl methacrylate-methacrylic acid copolymers with different fractions of acid groups (x) has been studied in aqueous solution at, various pH values using the fluorescence of covalently bonded 9-vinyl anthracene as a probe. In all cases, the extent of binding increases as a function of the charge of the polymer with either increasing fraction of carboxylic acids or of pH. However, differences are observed in the behavior of the three cations, With Tl(I), quenching of the anthracene group fluorescence is observed. indicating that the thallium(I) approaches the probe and suggesting that the alkylanthracene is probably in a relatively polar region. Binding constants have been determined from anthracene quenching data and from studies with the fluorescent-probe sodium pyrenetetrasulfonate, Good agreement is obtained between the two methods, and values for the binding constants increase from 250 to 950 M-1 as x increases from 0.39 to 1. It is suggested that the cation is held in the polyelectrolyte domain, partly by Debye-Huckel effects and partly by more specific interactions. Stronger binding is found with calcium(II) and terbium(III), and in this case increases in fluorescence intensity are observed on complexation due to the anthracene group being in a more hydrophobic region, probably as a result of conformational changes in the polymer chain. In the former case the stoichiometry of the interaction was determined from the fluorescence data to involve two carboxylate groups bound per calcium. Association constants were found using murexide as an indicator of free calcium to vary from 8400 to 37 000 M-1 as x increases from 0.39 to 1. It is suggested that in this case specific calcium(II)-carboxylate interactions contribute to the binding. With terbium(III), a greater increase in the probe fluorescence intensity was observed than with calcium, and it is suggested that the interaction with the polymer is even stronger, leading to a more pronounced conformational change in the polymer. It is proposed that the terbium(III) interacts with sis carboxylic groups on the polymer chain, with three being coordinated and three attracted by electrostatic interactions.

Thermal decomposition of crystalline Ni-II-Cr-III layered double hydroxide: A structural study of the segregation process

A structural study of the thermal evolution of Ni0.69Cr0.31(OH)(2)(CO3)(0.155)(.)nH(2)O into NiO and tetragonal NiCr2O4 is reported. The characteristic structural parameters of the two coexisting crystalline phases, as well as their relative abundance, were determined by Rietveld refinement of powder x-ray diffraction (PXRD) patterns. The results of the simulations allowed us to elucidate the mechanism of the demixing process of the oxides. It is demonstrated that nucleation of a metastable nickel chromite within the common oxygen framework of the parent Cr-III-doped bunsenite is the initial step of the cationic redistribution. The role that trivalent cations play in the segregation of crystalline spinels is also discussed.

Cycloaddition reaction of the azido-bridged cyclometallated complex [Pd(dmba)N-3](2) with CS2. Crystal and molecular structure of DI(mu, N,S-1,2,3,4-thiatriazole-5-thiolate) bis[(N,N-dimethylbenzyl-amine-C-2,N)palladium(II)]

The 1,3-dipolar cycloaddition of carbon disulfide to the coordinated azide in the cyclometallated compound [Pd(dmba)(N-3)](2) (1), dmba = N,N-dimethylbenzylamine, was investigated. The compound obtained di(mu, N,S-1,2,3,4-thiatriazole-5-thiolate)-bis[(N,N-dimethylbenzylamine-C-2,N)palladium(II)] (2), was characterized by IR spectroscopy and X-ray diffraction. Complex (2) is dimeric with the two [Pd(N,N-dimethylbenzylamine)] moieties being connected by the two vicinal bridging N,S-1,2,3,4-thiatriazole-5-thiolate anions in a square-planar coordination for the palladium atoms.

An investigation of the thermal behavior of heterobimetallic species containing copper(II) and tetracyanopalladate(II)

Synthesis, characterization and thermal behavior of four compounds that have the general formula [Cu{Pd(CN)(4)}(L)(x)](n), in which en = 1,2-diaminoethane and pn = 1,3-diaminopropane (L = en, x = 1 (I); L = pn, x = 1 (II); L = en, x = 2 (III); L = pn, x = 2 (IV)) were described in this work. The complexes were studied by elemental analysis, infrared spectroscopy (IR), differential thermal analysis (DTA) and thermogravimetry (TG) and the residues of the thermal decomposition were characterized by X-ray powder diffraction and found as a mixture of CuO and PdO. The stoichiometry of the compounds was established via thermogravimetric and elemental analyses and their structures were proposed as coordination polymers based on their infrared spectra. The following thermal stability sequence was found: IV < I=II < III.

A rapid procedure for the isolation of the Lys-49 myotoxin II from Bothrops moojeni (caissaca) venom: Biochemical characterization, crystallization, myotoxic and edematogenic activity

A, M. Soares, V, M, Rodrigues, M. I. Homsi-Brandeburgo, M. H. Toyama, F, R, Lombardi, K. Arni and J. R, Giglio. A rapid procedure for the isolation of the Lys-49 myotoxin II from Bothrops moojeni (caissaca) venom: Biochemical characterization, crystallization, myotoxic and edematogenic activity. Toxicon 36, 503-514, 1998.-Bothrops moojeni snake venom was fractionated on a CM-Sepharose column which was previously equilibrated with 0.05 M ammonium bicarbonate buffer at pH 8.0 and subsequently eluted with an ammonium bicarbonate concentration gradient from 0.05 to 0.5 M at constant pH (8.0) and temperature (25 degrees C). The fraction which eluted last (M-VI) showed, after direct lyophilization, a single band by polyacrylamide gel electrophoresis (PAGE) and SDS-PAGE, indicating an approximate M,. of 14 000 and 77 000, in the presence and absence of dithiothreitol, respectively. Its amino acid composition revealed a high level of hydrophobic and basic amino acids as well as 13 half-cystine residues. Its isoelectric point and extinction coefficient (E-1.0cm(1.0mg/ml) at 278 nm and pH 7.0) were 8.2 and 1.170, respectively. M-VI was devoid of phospholipase A(2) (PLA(2)) activity on egg yolk, as well as of hemorrhagic, anticoagulant and coagulant activities, but could induce drastic necrosis on skeletal muscle fibres as well as rapid and transient edema on the rat paw. Its N-terminal sequence: SLFELGKMILQETGKNPAKSYGVYGCNCGVGGRGKPKDATDRCCYVHKCCYK.... revealed high homology with other Lys 49 PLA(2)-like myotoxins from other bothropic venoms. Orthorhombic crystals of M-VI? which diffracted to a maximal resolution of 1.6 Angstrom. were obtained and indicated the presence of a dimer in the asymmetrical unit. (C) 1998 Elsevier B.V. Ltd. All rights reserved.

Comparative study of the Frankel (FR-2) and bionator appliances in the treatment of Class II malocclusion

The purpose of this investigation was to compare the dentoalveolar and skeletal cephalometric changes produced by the Frankel (FR-2) and bionator appliances in persons with Class 11 malocclusion. Lateral cephalograms were available for 66 patients of both sexes, who were divided into 3 groups of 22. The control group included untreated Class 11 children, with an initial mean age of 8 years 7 months; they were followed without treatment for 13 months. The FR-2 appliance group had an initial mean age of 9 years; those children were treated for a mean period of 17 months. The bionator group initially had a mean age of 10 years 8 months; on average, they were treated for 16 months. The results demonstrated no significant changes in maxillary growth during the evaluation period. Both appliances showed statistically significant increases in mandibular growth and mandibular protrusion, with greater increases in patients treated in the bionator group. Both experimental groups showed an improvement in the maxillomandibular relationship. There were no significant changes in growth direction, while the bionator group had a greater increase in posterior facial height. Both appliances produced similar labial tipping and protrusion of the lower incisors, lingual inclination, retrusion of the upper incisors, and a significant increase in mandibular posterior dentoalveolar height. The major treatment effects of bionator and FR-2 appliances were dentoalveolar, with a smaller, but significant, skeletal effect.

Thermal behavior of the Ti(IV), Zr(IV) and Pb(II) complexes with 5-nitro-8-hydroxyquinoline

Ti(IV), Zr(IV) and Pb(II) complexes with 5-nitro-8-hydroxyquinoline (5-NQ) were obtained by precipitation in acetone/ammonium solution medium. The compounds TiO(C9H5N2O3)(2).0.5H(2)O, ZrO(C9H5N2O3)(2)2H(2)O and Pb(C9H5N2O3)(2) were characterized by Elemental Analysis, X-ray Diffratometry and Infrared Absorption Spectrometry and their thermal behavior followed by TG/DTA. This present study intends to show the variations in the thermal behavior of the compounds and in the composition and/or structure of final oxide residues, in different atmospheres and heating rates.

Model peptides mimic the structure and function of the N-terminus of the pore-forming toxin sticholysin II

To investigate the role of the N-terminal region in the lytic mechanism of the pore-forming toxin sticholysin II (St II), we studied the conformational and functional properties of peptides encompassing the first 30 residues of the protein. Peptides containing residues 1-30 (P1-30) and 11-30 (P11-30) were synthesized and their conformational properties were examined in aqueous solution as a function of peptide concentration, pH, ionic strength, and addition of the secondary structure-inducing solvent trifluoroethanol (TFE). CD spectra showed that increasing concentration, pH, and ionic strength led to aggregation of P1-30; as a consequence, the peptide acquired beta-sheet conformation. In contrast, P11-30 exhibited practically no conformational changes under the same conditions, remaining essentially structureless. Moreover, this peptide did not undergo aggregation. These differences clearly point to the modulating effect of the first 10 hydrophobic residues on the peptides aggregation and conformational properties. In TFE both the first ten hydrophobic peptides acquired alpha-helical conformation, albeit to a different extent, P11-30 displayed lower alpha-helical content. P1-30 presented a larger-fraction of residues in alpha-helical conformation in TFE than that found in St II's crystal structure for that portion of the protein. Since TFE mimics the membrane em,, such increase in helical content could also occur upon toxin binding to membranes and represent a step in the mechanism of pore formation. The peptides conformational properties correlated well with their functional behaviour. Thus, P1-30 exhibited much higher hemolytic activity than P11-30. In addition, P11-30 was able to block the toxin's hemolytic activity. The size of pores formed in red blood cells by P 1-30 was estimated by measuring the permeability PEGs of different molecular mass. The pore radius (0.95 +/- 0.01 nm) was very similar to that of the PEGs of different pore formed by the toxin. The results demonstrate that the synthetic peptide P1-30 is a good model of St 11 conformation and function and emphasize the contribution of the toxin's N-terminal region, and, in particular, the hydrophobic residues 1-10 to pore formation. (c) 2005 Wiley Periodicals, Inc.

Synthesis and X-ray structure of the dinuclear platinum(II) complex with saccharin {K[Pt(sac)(3)(H2O)] center dot H2O}(2): Studies on its antiproliferative activity in aqueous solution

Synthesis and X-ray structure of a dinuclear platinum(II) complex with the ligand saccharin(sac) are described. The structure shows two approximately square-planar platinum centers. Each platinum atom is coordinated to one water molecule and three N-bonded saccharinate ligands. The two centers are linked through two potassium atoms. Each potassium atom interacts with six oxygen atoms from hydration and coordinated water molecules and from carbonyl and sulfonate groups of the ligands. It is suggested that, in aqueous solution, the dimeric structure of the complex is dissociated and the monomeric species K[Pt(sac)(3)(H2O)] is formed. The complex was dissolved in water and submitted to in vitro cytotoxic analyses using HeLa cells (human cervix cancer). It was shown that the monomeric complex elicited a potent cytotoxic activity when compared to the vehicle-treated cells. The IC50 value for the monomeric complex is 6.8 mu M, a little bit higher than that obtained for cisplatin. (c) 2007 Elsevier B.V. All rights reserved.

Nitric oxide and anglotensin II receptors mediate the pressor effect of angiotensin II: A study in conscious and zoletil-anesthetized rats

The circumventricular structures of the central nervous system and nitric oxide are involved in arterial blood pressure control, and general anesthesia may stimulate the central renin-angiotensin system. We therefore investigated the central role of angiotensin 11 and nitric oxide on the regulation of systemic arterial blood pressure in conscious and anesthetized rats. METHODS: Rats with stainless steel cannulae implanted into their lateral ventricle were studied. We injected the AT(1) and AT(2) angiotensin 11 receptor antagonists, losartan and PD123319, L-NAME, 7-nitroindazole (nitric oxide synthetase inhibitors), and FK409 (nitric oxide donor agent) into the lateral ventricles. Mean arterial blood pressure (MAP) was recorded in conscious and zoletil-anesthetized rats. RESULTS: Mean +/- (SEM) baseline MAP was 117.5 +/- 2 mm Hg. Angiotensin II injected into the brain lateral ventricle increased MAP from 136.5 +/- 2 min Hg to 138.5 +/- 4 mm Hg (Delta 16 +/- 3 mm Hg to Delta 21 +/- 3 mm Hg) for all experimental groups versus control from 116 +/- 2 mm Hg to 120 +/- 3 mm Hg (Delta 3 +/- 1 mm Hg to A5 +/- 2 mm Hg) (P < 0.05). L-NAME or 7-nitroindazole enhanced the angiotensin II pressor effect (P < 0.05). Prior injection of losartan and PD123319 decreased the angiotensin 11 pressor effect and the enhancement effect of L-NAME and 7-nitroindazole (P < 0.05). Zoletil anesthesia did not interfere with the effects of angiotensin 11, AT,, AT2 antagonists, or nitric oxide synthetase inhibitors. CONCLUSIONS: Endogenous nitric oxide functions tonically as a central inhibitory modulator of the angiotensinergic system. AT, and AT2 receptors influence the angiotensin 11 central control of arterial blood pressure. Zoletil anesthesia did not interfere with these effects. (Anesth Analg 2007;105:1293-7)

Effects of subtypes alpha- and beta-adrenoceptors of the lateral hypothalamus on the water and sodium intake induced by angiotensin II injected into the subfornical organ

The present experiments were conducted to investigate the role of the alpha (1A)-, alpha (1B), beta (1),- and beta (2)-adrenoceptors of the lateral hypothalamus (LH) on the water and salt intake responses elicited by subfornical organ (SFO) injection of angiotensin II (ANG II) in rats. 5-methylurapidil (an alpha (1A)-adrenergic antagonist), cyclazosin (an alpha (1B)-adrenergic antagonist) and ICI-118,551 (a beta (2)-adrenergic antagonist) injected into the LH produced a dose-dependent reduction, whereas efaroxan (an alpha (2)-antagonist) increased the water intake induced by administration of ANG II into the SFO. These data show that injection of 5-methylurapidil into the LH prior to ANG II into the SFO increased the water and sodium intake induced by the injection of ANG II. The present data also show that atenolol (a beta (1)-adrenergic antagonist), ICI-118,551, cyclazosin, or efaroxan injected into the LH reduced in a dose-dependent manner the water and sodium intake to angiotensinergic activation of SFO. Thus, the alpha (1)- and beta -adrenoceptors of the LH are possibly involved with central mechanisms dependent on ANG II and SFO that control water and sodium intake. (C) 2000 Elsevier B.V. B.V. All rights reserved.