Electronic and fluorescent studies on the interaction of DNA and BSA with a new ternary praseodymium complex containing 2,9-dimethyl 1,10-phenanthroline and antibacterial activities testing.

In this study, fluorescence emission spectra, UV-vis absorption spectra, ethidium bromide (EB)-competition experiment, and iodide quenching experiment were used for the interaction study of the Fish salmon DNA (FS-DNA) with [Pr(dmp)2Cl3(OH2)] where dmp is 2,9-dimethyl 1,10-phenanthroline. The binding constant and the number of binding sites of the complex with FS-DNA were 6.09 ± 0.04 M-1 and 1.18, respectively. The free energy, enthalpy, and entropy changes (ΔG°, ΔH°, and ΔS°) in the binding process of the Pr(III) complex with FS-DNA were -8.02 kcal mol-1, +39.44 kcal mol-1, and +159.56 cal mol-1 K-1, respectively. Based on these results, the interaction process between FS-DNA with [Pr(dmp)2Cl3(OH2)] was spontaneous and the main binding interaction force was groove binding mode. Also, Fluorescence and electronic absorption spectroscopy were used in order to evaluate the binding characteristics, stoichiometry, and interaction mode of praseodymium(III) (Pr(III)) complex with bovine serum albumin (BSA). Title complex showed good binding propensity to BSA presenting moderately high Kb values. The fluorescence quenching of BSA by Pr(III) complex has been observed to be the static process. The positive ΔH° and ΔS° values showed that the hydrophobic interaction is the main force in the binding of Pr(III) complex and BSA. Eventually, the average aggregation number, , of BSA potentially induced by title complex confirmed the 1:1 stoichiometry for title complex-BSA adducts. In vitro, antimicrobial activity of title complex was indicated that the complex is more active against both Escherichia coli and Enterococcus faecalis bacterial strains than Staphylococcus aureus, and Pseudomonas aeruginosa. Communicated by Ramaswamy H. Sarma.

Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA.

The binding properties on [PrL2(NO3)](NO3)2 (L=9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7Hpyrido[1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) to bovine serum albumin (BSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-Vis absorbance spectroscopy. The results showed that [PrL2(NO3)](NO3)2 strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was about 1, and the efficiency of Förster energy transfer provided a distance of 4.26 nm between tryptophan and [PrL2(NO3)](NO3)2 binding site. At 288, 298, 310 K, the quenching constants of BSA-[PrL2(NO3)](NO3)2 system were 5.11×10(4), 4.33×10(4) and 3.71×10(4) l M(-1). ΔH, ΔS and ΔG were obtained based on the quenching constants and thermodynamic theory (ΔH<0, ΔS>0 and ΔG<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL2(NO3)](NO3)2-BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL2(NO3)](NO3)2 in aqueous solution. Moreover, the interaction between [PrL2(NO3)](NO3)2 and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL2(NO3)](NO3)2 with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL2(NO3)](NO3)2 can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.

Study on fluorescence and DNA-binding of praseodymium(III) complex containing 2,2'-bipyridine.

The fluorescence of praseodymium(III) complex containing 2,2'-bipyridine, [Pr(bpy)2Cl3·OH2] has been investigated in details. Also, the biological activity of [Pr(bpy)2Cl3·OH2] has been evaluated by examining its ability to bind to DNA with UV-vis, fluorescence as well as viscosity measurement. The fluorescence of [Pr(bpy)2Cl3·OH2] is strongly quenched through static mechanism in the presence of DNA. DNA intrinsic binding constant, Kb the binding site number, n the Stern-Volmer quenching constant, KSV and the thermodynamic parameters have been determined by fluorescence spectroscopy. For characterization of bonding mode, the effect of various experimental parameters were investigated on the interaction of [Pr(bpy)2Cl3·OH2] with DNA.

Effect of praseodymium(III) on zinc(II) species in human interstitial fluid.

A multiphase model of metal ion species in human interstitial fluid was constructed under physiological conditions. The effect of Pr(III) on Zn(II) species was studied. At the normal conditions, Zn(II) species mainly distribute in [Zn(HSA)], [Zn(IgG)], and [Zn(Cys)(2)H](+). With the Pr(III) level increased, the apparent competition of Pr(III) for ligands lead to the redistribution of Zn(II) species.

Comparison of energy interaction parameters for the complexation of Pr(III) with glutathione reduced (GSH) in absence and presence of Zn(II) in aqueous and aquated organic solvents using 4f-4f transition spectra as PROBE.

The coordination chemistry of glutathione reduced (GSH) is of great importance as it acts as excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. In our work we have studied two chemically dissimilar metal ions viz. Pr(III), which prefer hard donor site like carboxylic groups and Zn(II) the soft metal ion which prefer peptide-NH and sulphydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic Complexation of GSH with Pr(III) and Zn(II) has been explored in aqueous and aquated organic solvents. The variation in the energy parameters like Slater-Condon (F(K)), Racah (E(K)) and Lande (xi(4f)), Nephelauxetic parameter (beta) and bonding parameter (b(1/2)) are computed to explain the nature of complexation.

Absorption spectroscopic investigations involving 4f-4f transitions to explore the kinetics of complexation of Zn(II) with Pr(III)-glutathione complex.

The kinetics of complexation of Zn(II) with Pr2(GSH)2.(H2O)4 1 (GSH-glutathione) to form Pr2(GSH)2Zn(H2O)6 complex 2 has been investigated at 30 degrees C by following the changes in the intensity (absorbance, molar absorptivity) and intensity (oscillator strength P and Judd-Ofelt-T(lambda) intensity) parameters in equimolar DMF-Water. In order to support kinetics data, the complex 1 and 2 have been synthesized and characterized by elemental analysis, IR and 1H NMR spectral analysis. Molecular weights of 1 and 2 determined by ebullioscopic and cryoscopic methods and preliminary molecular modeling experiments have helped in proposing most probable structures for 1 and 2. Kinetics showed first order dependence, in terms of concentration of Zn(II) and complex 1, on the rate of formation of complex 2. Generally, hypersensitive transitions (the transitions obeying /DeltaJ/ selection rules) were used in spectra-structure correlation studies. We have used the four 4f-4f transitions of Pr(III), which do not obey selection rules, yet are substantially sensitive to coordination changes, for kinetic study. The rate constants evaluated from individual 4f-4f bands are quite close hence supporting our observations on ligand mediated pseudohypersensitivity.

Computer simulation for effect of Pr(III) on Ca(II) speciation in human interstitial fluid.

A multiphase model of metal ion speciation in human interstitial fluid was constructed and the effect of Pr(III) on Ca(II) speciation was studied. Results show that free Ca2+, [Ca(HCO3)], and [Ca(Lac)] are the main species of Ca(II). Because of the competition of Pr(III) for ligands with Ca(II), the percentages of free Ca2+, [Ca(Lac)], and [Ca(His)(Thr)H3] increase gradually and the percentages of CaHPO4(aq) and [Ca(Cit)(His)H2] decrease gradually with the increase in the total concentration of Pr(III). However, the percentages of [Ca(HCO3)] and CaCO3(aq) first increase and then begin to decrease when the total concentration of Pr(III) exceeds 6.070 x 10-4 M.

Preliminary characterization of a light-rare-earth-element-binding peptide of a natural perennial fern Dicranopteris dichotoma.

A light-rare-earth-element (LREE)-binding peptide was isolated from LREE hyperaccumulator Dicranopteris dichotomaleaves and characterized in terms of molecular weight and ultraviolet absorption spectrum. The molecular weight of the LREE-binding peptide was determined to be 2208 Da by matrix-assisted laser-desorption ionization-time of flight mass spectrometry (MALDI-TOFMS). The characteristic ultraviolet absorption spectrum of the peptide was observed at 220-300 nm, suggesting that the peptide chain contained aromatic amino acids. Compared to the unique features of the phytochelatins with a low absorption at 280 nm, the LREE-binding peptide is unlikely to be a typical phytochelatin. The present study suggests that the LREE-binding peptide is probably a natural peptide in D. dichotoma, and it may play an important role in hyperaccumulation of LREEs.

Protection against membrane damage: a 1H-NMR investigation of the effect of Zn2+ and Ca2+ on the permeability of phospholipid vesicles.

1H-NMR spectroscopy of small, unilamellar dipalmitoyl phosphatidylcholine (DPPC) vesicles in conjunction with the lanthanide shift reagent Pr3+ was used to study the effect of Zn2+ and Ca2+ ions on the permeability induced at the lipid phase transition temperature (Tc) of the vesicles and by the bee venom polypeptide melittin. In addition, the effects of Zn2+ and Ca2+ were studied on Triton X-100 stabilized channels at Tc and in the presence of n-alcohols. The results show that the presence of 10 mM Zn2+ and Ca2+ inhibited most of the forms of vesicular permeability investigated. The results are discussed in terms of the nature of the binding of the metal ions to the vesicles and support the proposal that one biological function of Zn2+ and Ca2+ is protection against membrane damage.

NMR study of the interaction of beta-blockers with sonicated dimyristoylphosphatidylcholine liposomes in the presence of praseodymium cation.

The interaction of a series of beta-adrenoreceptor blocking agents with unilamellar dimyristoylphosphatidylcholine (DMPC) liposomes has been studied by proton nuclear magnetic resonance (1H-NMR) in the presence of praseodymium cation (Pr3+) at 30 degrees C. Addition of Pr3+ increased the splitting of the trimethylammonium group signals arising from the phospholipid molecules located at the internal and external surfaces of the bilayers. Adding Pr3+ caused a considerable downfield shift of the external peak but only a slight upfield shift of the internal peak (approximately 3%). The difference in chemical shift of the external and internal peaks (delta Hz) increased linearly as a function of Pr3+ concentration up to 10 mM. The addition of beta-blockers reversed the effect of Pr3+, and propranolol exerted the most pronounced effect, causing complete reversal of the splitting at a concentration of 5 mM. Much higher concentrations of other beta-blockers were required to displace Pr3+. A linear correlation between Pr3+ displacement (P) and logarithm of the apparent partition coefficient (K'm) in DMPC liposomes was obtained for hydrophobic beta-blockers, but hydrophilic beta-blockers did not fit this correlation. It appears that beta-blockers that have ortho or meta substitution require penetration of the liposome bilayers before significant polar group interaction can occur. On the other hand, beta-blockers that have para substitution and low K'm values are able to interact with the polar surfaces of the liposomes without penetration to cause displacement of Pr3+.

Synergistic effects in PR3+ transport mediated by ionophores across phosphatidylcholine vesicles.

Use of a fluorescent probe for the intravesicular pH shows that synergisms previously observed in Pr3+ transport across phosphatidylcholine vesicles are explained by an increase in the proton counter-transport.

Characterization of ATP complexes with lanthanide (III) ions.

Several spectroscopic techniques are used to investigate the stoichiometry and properties of ATP complexes with lanthanide(III) (Ln(III)], ions. The ATP2-lanthanide(III) complex predominates at millimolar ATP levels and dissociates to the 1:1 complex with a Kd of 300 +/- 50 microM for the Eu(III) case. Two independent techniques, viz. field-dependent water proton relaxation for the Gd(III) complex and metal ion luminescence lifetime measurements for the Eu(III) complex, yield a value of approximately 2 for the number of water molecules coordinated to the metal ion. The latter technique yields an approximate metal-ion hydration number of 4 for the 1:1 complex. Dynamic properties of the Gd(III) X ATP2 complex including the temperature dependence of correlation times describing rotation of the complex and ATP exchange have been studied by field-dependent water-proton relaxation and by temperature-dependent 31P NMR relaxation studies. These data are consistent with formation of a 2:1 ATP-lanthanide complex at millimolar ATP concentrations. Other types of complexes are detected under conditions in which there is insufficient ATP to satisfy the 1:2 metal:nucleotide stoichiometry.

Lack of transbilayer coupling in phase transitions of phosphatidylcholine vesicles.

Praseodymium and ytterbium chlorides were used as nuclear magnetic resonance shift reagents to resolve the inner and outer choline methyl resonances of single-walled dimyristoylphosphatidylcholine bilayer vesicles. The gel to liquid-crystalline phase transition of these vesicles was monitored by observing the proton and carbon-13 nuclear magnetic resonance line widths of the choline methyl group nuclei. In the absence of ions the transition occurred at 21.5 degrees C in both halves of the bilayer. With Pr3+ or Yb3+ added to the outside of the vesicles, the phase transition temperature of the outer half of the bilayer was raised several degrees, while the transition temperature of the inner half was unchanged. In vesicles containing 20 mol % cholesterol the phase transition of the outer monolayer was considerably broadened, while the inner half still melted sharply at 21.6 degrees C. By use of dipalmitoylphosphatidylcholine vesicles with UO2(2)+ added to the outside, phase transitions at 41.5 and 44 degrees C were detected by electron spin resonance with the spin-label 2,2,6,6-tetramethylpiperidinyl-l-oxy. These results imply that the two halves of the bilayer in phospholipid vesicles are so weakly coupled that they can undergo the gel to liquid-crystalline phase transition independently.

Erythrocyte alterations in praseodymium-induced lecithin:cholesterol acyltransferase (LCAT) deficiency in the rat: comparison with familial LCAT deficiency in man.

The intravenous administration of praseodymium nitrate (PrN) to rats was associated with parallel decreases in plasma lecithin: cholesterol acyltransferase (LCAT) activity and erythrocyte osmotic fragility at low doses (20 and 40 mg/kg) while higher doses (80 mg/kg) resulted in increases in both. Erythrocyte membranes from rats with PrN-induced LCAT deficiency exhibited small increases in cholesterol content, but not other alterations (e.g., in phospholipid profiles and sulfhydryl group latency) which characterize erythrocytes in familial LCAT deficiency in man. The administration of PrN caused a time- and dose-dependent accumulation of praseodymium in liver with hepatic levels being substantially greater in animals given the high (protective) as compared with the low (toxic) doses of PrN. Hepatic levels of glutathione were not altered by PrN administration, but hexobarbital sleeping time was markedly prolonged in animals receiving a toxic dose of PrN. It is suggested that dose-dependent alterations in the subcellular distribution of praseodymium may explain the paradoxical pathophysiological effects of high and low doses of PrN.

A 1H-NMR investigation of the mechanism for the ionophore activity of the bile salts in phospholipid vesicular membranes and the effect of cholesterol.

A 1H-NMR method previously applied to ionophore-medicated transport is used to investigate a similar behaviour by the bile salts. The permeability of phosphatidylcholine vesicles to Pr3+ is increased by several orders of magnitude over the self-diffusion rate and the kinetics indicate a transbilayer movement of inverted micelles [Pr(bile salt)4]. In vesicles containing 40 mol% cholesterol the mechanism of permeability is radically altered and the di- and trihydroxy bile salts behave differently.

Investigation of polyene macrolide antibiotic-induced permeability changes in vesicles by 31P nuclear magnetic resonance.

The permeability of egg yolk lecithin (EYL) vesicles to Pr3+ has been measured by 31P nuclear magnetic resonance (nmr) spectroscopy. Measurable Pr3+ leakage into the internal aqueous compartment of EYL vesicles at ambient (21 degrees C) temperature required the presence of small (7--10 mol%) amounts of dicetyl phosphate (DCP). The permeability of DCP-containing vesicles is decreased by incorporation of sterol (cholesterol greater than ergosterol approximately 5.6-dihydroergosterol greater than zymosterol) into the lipid bilayer. Addition of the polyene macrolide antibiotic, nystatin, to DCP-containing EYL vesicles with and without sterol resulted in increased Pr3+ permeability at the three temperatures studied (21--37.5 degrees C). Permeability changes observed upon addition of nystatin to sterol-impregnated, DCP-containing vesicles varied with sterol structure: ergosterol approximately 5,6-dihydroergosterol greater than cholesterol approximately zymosterol. These results are compared with other polyene macrolide induced permeability changes on model and natural membrane systems. Permeability changes induced by nystatin in sterol-free EYL vesicles were generally greater than for comparable sterol-containing vesicles. This is attributed to a nonspecific interaction of the antibiotic with the latter vesicles.