PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Lithium Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,585 records · Page 88Linked to original sources
PubMed2005

Electrophilic attack on sulfur-sulfur bonds: coordination of lithium cations to sulfur-rich molecules studied by ab initio MO methods.

Complex formation between gaseous Li+ ions and sulfur-containing neutral ligands, such as H2S, Me2Sn (n = 1-5; Me = CH3) and various isomers of hexasulfur (S6), has been studied by ab initio MO calculations at the G3X(MP2) level of theory. Generally, the formation of LiS(n) heterocycles and clusters is preferred in these reactions. The binding energies of the cation in the 29 complexes investigated range from -88 kJ mol(-1) for [H2SLi]+ to -189 kJ mol(-1) for the most stable isomer of [Me2S5Li]+ which contains three-coordinate Li+. Of the various S6 ligands (chair, boat, prism, branched ring, and triplet chain structures), two isomeric complexes containing the S5==S ligand have the highest binding energies (-163+/-1 kJ mol(-1)). However, the global minimum structure of [LiS6]+ is of C(3v) symmetry with the six-membered S(6) homocycle in the well-known chair conformation and three Li--S bonds with a length of 256 pm (binding energy: -134 kJ mol(-1)). Relatively unstable isomers of S6 are stabilized by complex formation with Li+. The interaction between the cation and the S6 ligands is mainly attributed to ion-dipole attraction with a little charge transfer, except in cations containing the six sulfur atoms in the form of separated neutral S2, S3, or S4 units, as in [Li(S3)2]+ and [Li(S2)(S4)]+. In the two most stable isomers of the [LiS6]+ complexes, the number of S--S bonds is at maximum and the coordination number of Li+ is either 3 or 4. A topological analysis of all investigated complexes revealed that the Li--S bonds of lengths below 280 pm are characterized by a maximum electron-density path and closed-shell interaction.

Cations↗
PubMed2006

Electromigration of ions across the skin: determination and prediction of transport numbers.

In iontophoresis, an electric field across the skin induces electromigration of exogenously applied and endogenously present ions. The approach can be used to improve dramatically drug delivery by elimination of competing co-ions in the externally applied formulation, as this maximizes the fraction of current carried by (i.e., the transport number of) the drug. In this study, the dependence of the transport number on the nature of the ions present at the anode and cathode was examined using 12 different combinations of ions (4 cations x 3 anions). Cationic transport numbers (t(C+) (o)) were a function of their inherent mobilities and depended upon those of the single anion at the cathode; however, t(C+) (o) was independent of the counter-ion concentration. The extensive data obtained agreed well, furthermore, with a theoretical framework previously developed for this so-called "single-ion" situation. In addition, there was a strong correlation between ionic transport numbers in the skin and those in aqueous solution, which are easily estimated from measurements of ionic mobility. It follows that it should be possible, from the framework developed here, to establish a predictive tool, combining theory with simple experiments, for the optimization of iontophoretic drug delivery.

Acetates↗
PubMed1998

Ribosomal protein L15 as a probe of 50 S ribosomal subunit structure.

L15, a 15 kDa protein of the large ribosomal subunit, interacts with over ten other proteins during 50 S assembly in vitro. We have probed the interaction L15 with 23 S rRNA in 50 S ribosomal subunits by chemical footprinting, and have used localized hydroxyl radical probing, generated from Fe(II) tethered to unique sites of L15, to characterize the three-dimensional 23 S rRNA environment of L15. Footprinting of L15 was done by reconstituting purified, recombinant L15 with core particles derived from Escherichia coli 50 S subunits by treatment with 2 M LiCl. The cores migrate as compact 50 S-like particles in sucrose gradients, contain 23 S and 5 S rRNA, and lack a subset of the 50 S proteins, including L15. Using both Fe(II).EDTA and dimethyl sulfate, we have identified a strong footprint for L15 in the region spanning nucleotides 572-654 in domain II of 23 S rRNA. This footprint cannot be detected when L15 is incubated with "naked" 23 S rRNA, indicating that formation of the L15 binding site requires a partially assembled particle.Protein-tethered hydroxyl radical probing was done using mutants of L15 containing single cysteine residues at amino acid positions 68, 71 and 115. The mutant proteins were derivatized with 1-[p-(bromo-acetamido)benzyl]-EDTA. Fe(II), bound to core particles, and hydroxyl radical cleavage was initiated. Distinct but overlapping sets of cleavages were obtained in the footprinted region of domain II, and in specific regions of domains I, IV and V of 23 S rRNA. These data locate L15 in proximity to several 23 S rRNA elements that are dispersed in the secondary structure, consistent with its central role in the latter stages of 50 S subunit assembly. Furthermore, these results indicate the proximity of these rRNA regions to one another, providing constraints on the tertiary folding of 23 S rRNA.

Edetic Acid↗
PubMed1987

Cationic interactions with Na+-H+ exchange and passive Na+ flux in cardiac sarcolemmal vesicles.

Na+-H+ exchange and passive Na+ flux were investigated in cardiac sarcolemmal vesicles as a function of changing the ionic composition of the reaction media. The inclusion of EGTA in the reaction medium resulted in a potent stimulation of Na+ uptake by Na+-H+ exchange. It was found that millimolar concentrations of Mg2+ and Li+ were capable of inhibiting Na+-H+ exchange by 80%. One mechanism by which these ions may inhibit intravesicular Na+ accumulation by Na+-H+ exchange is via an increase in Na+ efflux. An examination of Na+ efflux kinetics from vesicles pre-loaded with Na+ revealed that Na+, Ca2+, Mg2+ and Li+ could stimulate Na+ efflux. Na+-H+ exchange was potently inhibited by an organic divalent cation, dimenthonium, which screens membrane surface charge. This would suggest that Na+-H+ exchange occurs in the diffuse double layer region of cardiac sarcolemma and this phenomenon is distinctly different from other Na+ transport processes. The results in this study indicate that in addition to a stimulation of Na+ efflux, the inhibitory effects of Mg2+, Ca2+ and Li+ on Na+-H+ exchange may also involve a charge dependent screening of Na+ interactions with the membrane.

Animals↗
PubMed1997

Thiol group modulation of sodium-lithium countertransport kinetics in diabetic nephropathy.

Abnormal erythrocyte sodium-lithium countertransport (Na-Li CT) activity, traditionally measured at a single sodium concentration of 140 mmol.l-1 (V140), may represent an inherited risk marker for diabetic nephropathy. The membrane defect underlying this association is poorly understood, though modulation by key protein thiol groups appears to be important in essential hypertension. To improve understanding of this abnormality, Na-Li CT kinetics in untreated erythrocytes and after thiol group alkylation with N-ethylmaleimide were investigated in 18 subjects with diabetic nephropathy, 20 normoalbuminuric insulin-dependent diabetic (IDDM) subjects and 18 non-diabetic individuals. Using the traditional assay, V140 was similar in subjects with diabetic nephropathy compared to IDDM control subjects vs 0.311 (0.152-0.475) (0.247 (0.111-0.498) mmol Li.h-1.l erythrocytes-1). Kinetic parameters were abnormal in subjects with diabetic nephropathy compared with diabetic and non-diabetic control subjects with both Vmax (maximal Na-Li CT activity) (0.454 (0.257-0.963) vs 0.338 (0.183-0.972) vs 0.332 (0.213-0.603) mmol Li.h-1.l erythrocytes-1, p < 0.05), and Vmax/Km(So) ratio, reflecting ion association (6.03 (2.3-9.6) vs 4.73 (2.0-10.4) vs 4.48 (1.5-7.1), p < 0.01), significantly higher. N-ethylmaleimide decreased K(m)(So) and Vmax abolishing differences in Vmax/Km(So) ratio between groups (2.45 (1.18-4.21) vs 2.23 (0.96-4.3) vs 2.44 (1.4-3.7), but enhancing the differences in Vmax (0.186 (0.090-0.315) vs 0.120 (0.051-0.256) vs 0.128 (0.080-0.206) mmol Li.h-1.l erythrocytes-1, p < 0.0001). Of subjects with diabetic nephropathy, 78% were outside the 75th percentile of the non-diabetic control subjects when Vmax and Vmax/Km(So) ratio were combined, compared to 20% of the normoalbuminuric control subjects. We conclude that the traditional assay, V140, is poor at detecting individuals with diabetic nephropathy. Study of the kinetic parameters of the transporter, including thiol group modulation, suggests that increased ion association, Vmax/Km(So) ratio may represent the inherited defect and improves identification of subjects with diabetic nephropathy.

Adult↗