Binding Of Lead Ions Research Articles

Analytic and chemometric assessments of the native probiotic bacteria and inulin effects on bioremediation of lead salts.

Lead (Pb2+ ) is one of the most toxic heavy metals and can be found in various quantities in the environment. The five native probiotic bacteria and inulin were used to assess in vitro lead nitrate and lead acetate binding capacities, as well as removal potentials. The highest decrease in media pH was seen for samples containing a combination of Lactobacillus paracasei IRBC-M 10784, lead nitrate and inulin (5.30 ± 0.012). The presence of inulin in the environment accelerated decreases in the pH of all samples with no significance. In all groups, lead nitrate-containing samples included maximum pH decreases. From the highest to the lowest, the ability of lead removal was linked to Lactobacillus acidophilus PTCC-1932 (88.48%), Bifidobacterium bifidum BIA-7 (85.32%), Bifidobacterium lactis BIA-6 (85.24%), Lactobacillus rhamnosus IBRC-M 10782 (83.18%) and L. paracasei IRBC-M 10784 (80.66%). Most species included the highest decrease in lead nitrate. Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated that various functional groups (hydroxyl, carboxylic, carbonyl, amino and amide binds) on the bacterial cell wall were involved in lead ion binding during incubation. Principal component analysis of the FTIR results showed differences with respect to treated groups and control groups. The results obtained in the present study reveal that the simultaneous use of native probiotics and inulin can be an effective and safe approach for removing various toxic substances, especially Pb. © 2021 Society of Chemical Industry.

Pb arachidate Langmuir-Blodgett coatings of silicon wafers: relation between Pb particle density and subphase composition

The formation of lead arachidate (Pb(AA)2) coatings produced by Langmuir tensiometry (LT) was studied in dependence of lead nitrate (Pb(NO3)2) concentration in the aqueous subphase at pH 5.5. The stable Pb(AA)2 monolayers were transferred to Si wafers and TEM grids at 35 mN/m in the liquid condensed phase of the AA monolayer applying the Langmuir-Blodgett (LB) (ten monolayers) or the Langmuir-Schaefer (LS) technique, respectively. The most homogeneous monolayer was obtained at a Pb(NO3)2 concentration of 0.1 mM by using the LS method. Most homogeneous films (five bilayers) were obtained for a Pb(NO3)2 concentration of 0.01 mM by using the LB method. The formed films are investigated by transmission electron microscopy (monolayer produced by LS), X-ray reflectivity (XRR), and atomic force microscopy (films produced by LB). These methods revealed the formation of homogeneously distributed lead inclusions in the formed monolayers and films. Pb aggregates increase in number whereas their average size stays constant at ≈ 50 nm2 with increasing Pb(NO3)2 concentration. Thickness parameters were determined by XRR. With increasing Pb(NO3)2 concentration, the bilayer thickness was found to increase. Furthermore, the patterns (111) and (200) for a cubic lead structure were found. The experimental results are compared with simulations obtained from geometry optimization on a semi-empirical quantum level to discuss the lead-ion binding to the AA molecules at pH 5.5.

Crown Ether Functionalized Lipid Membranes: Lead Ion Recognition and Molecular Reorganization

A fluorescent lipid bilayer, functionalized with 18-crown-6, was developed to examine the mechanism of chemical recognition-induced molecular reorganization events in a membrane system. The synthetic receptor-lipid, PS18C6, was prepared with the crown ether at the headgroup position and a pyrene fluorescent tag on the hydrophobic tail. When incorporated into bilayers of distearylphosphatidylcholine, the receptor-lipid aggregated into domains, evidenced by the relatively large pyrene excimer emission from the bilayer. Langmuir pressure−area (π−A) isotherm measurements and atomic force microscopy (AFM) further aided in characterizing the receptor aggregation at the macro- and nanoscale, respectively. The functionalized bilayer exhibited selective affinity for mercuric and lead ions in aqueous buffered solution (pH 7.4), with a fluorescence response that was linear over the concentration range 10-7 to 10-4 M metal ions. 1H NMR studies established that the binding stoichiometry of PS18C6 with lead was 1:1, with Ka = 105 M-1 in methanol. Recognition and binding of lead ions at the membrane surface resulted in a rapid and prominent reorganization of the receptor-lipids in the membrane that was measurable at both the macro- and nanoscales. Removal of the lead ions, through the addition of EDTA, resulted in recovery of the original fluorescence and the reaggregation of structures in the membrane.

Lead ion binding and RNA chain hydrolysis in phenylalanine tRNA.

Crystalline complexes of yeast phenylalanine tRNA and Lead (II) ion were prepared by soaking pregrown orthorhombic crystals of tRNA in saturated lead chloride solutions. The locations of tightly bound lead ions on the tRNA were determined by difference Fourier methods. There are three major lead binding sites; two of these replace tightly bound magnesium ions in the native tRNA structure. Site I is located in the dihydrouridine loop of the molecule adjacent to phosphate P18 which is specifically cleaved by lead. This is evident from changes observed in the Pb-native difference electron density maps. A possible mechanism for lead ion hydrolysis of the polynucleotide chain is proposed.