scholarly journals DNA Compaction and Charge Neutralization Regulated by Divalent Ions in very Low pH Solution

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 337 ◽  
Author(s):  
Tianyong Gao ◽  
Wei Zhang ◽  
Yanwei Wang ◽  
Guangcan Yang
Keyword(s):  
Electrophoretic Mobility ◽  
Divalent Cations ◽  
Low Ph ◽  
Dna Conformation ◽  
Divalent Ions ◽  
Critical Charge ◽  
Charge Neutralization ◽  
Charge Fraction ◽  
Dna Compaction

DNA conformation is strongly dependent on the valence of counterions in solution, and a valence of at least three is needed for DNA compaction. Recently, we directly demonstrated DNA compaction and its regulation, mediated by divalent cations, by lowering the pH of a solution. In the present study, we found that the critical electrophoretic mobility of DNA is promoted to around −1.0 × 10−4 cm2 V−1 s−1 to incur DNA compaction or condensation in a tri- and tetravalent counterions solution, corresponding to an about 89% neutralized charge fraction of DNA. This is also valid for DNA compaction by divalent counterions in a low pH solution. It is notable that the critical charge neutralization of DNA for compaction is only about 1% higher than the saturated charge fraction of DNA in a mild divalent ion solution. We also found that DNA compaction by divalent cations at low pH is weakened and even decondensed with an increasing concentration of counterions.

Coagulation with Prepolymerized Aluminium Salts and their Influence on Particle and Phosphate Removal

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1229-1237 ◽  
Author(s):  
H. Ratnaweera ◽  
H. Ødegaard ◽  
J. Fettig
Keyword(s):  
Wastewater Treatment ◽  
Electrophoretic Mobility ◽  
Phosphate Removal ◽  
Particle Removal ◽  
Initial Formation ◽  
Dominant Mechanism ◽  
Charge Neutralization ◽  
Phosphate Ions ◽  
Hydroxo Complexes ◽  
Hydrolysis Products

Based on coagulation experiments, electrophoretic mobility measurements, and literature studies, mechanisms for particle and phosphate removal during coagulation with coagulants of different basicities are discussed. In wastewater treatment, particles are expected to be removed by both the adsorption -charge neutralization and sweep floc mechanisms. However, when coagulating with low basicity coagulants, the dominant mechanism for particle removal is suggested to be the sweep floc mechanism, while the dominant mechanism for phosphate removal is adsorption-precipitation by initial formation of aluminium - hydroxo -complexes. When coagulants with high basicities are used, the particles are removed dominantly by the adsorption - charge neutralization mechanism, while phosphate removal will be favoured by adsorption of phosphate ions on to the hydrolysis products.

scholarly journals Stabilization of Curcumin by Complexation with Divalent Cations in Glycerol/Water System

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Bachar Zebib ◽  
Zéphirin Mouloungui ◽  
Virginie Noirot
Keyword(s):  
Divalent Cations ◽  
Water System ◽  
Mechanical Mixture ◽  
Divalent Ions ◽  
Glycerol Water ◽  
Water Solvent ◽  
Metal Metal ◽  
Sulfate Salts ◽  
In Vitro Stability

The purpose of present study was to stabilize curcumin food pigment by its complexation with divalent ions like , in “green media” and evaluate its stability in vitro compared to curcumin alone. The curcumin complexes were prepared by mechanical mixture of curcumin and sulfate salts of each metal (metal : curcumin 1/1mol) into unconventional and nontoxic glycerol/water solvent. Two stoichiometry of complex were obtained, 1 : 1 and 1 : 2 (metal/curcumin), respectively. On evaluation of in vitro stability, all complexes were found to provide a higher stability from curcumin alone.

scholarly journals Coat proteins isolated from clathrin coated vesicles can assemble into coated pits.

1989 ◽  
Vol 108 (5) ◽  
pp. 1615-1624 ◽  
Author(s):  
D T Mahaffey ◽  
M S Moore ◽  
F M Brodsky ◽  
R G Anderson
Keyword(s):  
Ionic Strength ◽  
Plasma Membranes ◽  
Divalent Cations ◽  
Low Ph ◽  
Coated Vesicles ◽  
Coat Proteins ◽  
Coated Pits ◽  
Ph Buffer ◽  
Solid Substratum ◽  
Low Ionic Strength

Isolated human fibroblast plasma membranes that were attached by their extracellular surface to a solid substratum contained numerous clathrin coated pits that could be removed with a high pH buffer (Moore, M.S., D.T. Mahaffey, F.M. Brodsky, and R.G.W. Anderson. 1987. Science [Wash. DC]. 236:558-563). When these membranes were incubated with coat proteins extracted from purified bovine coated vesicles, new coated pits formed that were indistinguishable from native coated pits. Assembly was dependent on the concentration of coat protein with half maximal assembly occurring at 7 micrograms/ml. Assembly was only slightly affected by the presence of divalent cations. Whereas normal appearing lattices formed in a low ionic strength buffer, when assembly was carried out in a low pH buffer, few coated pits were evident but numerous small clathrin cages decorated the membrane. Coated pits did not form randomly on the surface; instead, they assembled at differentiated regions of membrane that could be distinguished in carbon/platinum replicas of frozen and etched membranes by the presence of numerous particles clustered into patches the size and shape of a coated pit.

scholarly journals Charge neutralization and collapse of the C-terminal tail of alpha-synuclein at low pH

2009 ◽  
Vol 18 (7) ◽  
pp. 1531-1540 ◽  
Author(s):  
Sebastian McClendon ◽  
Carla C. Rospigliosi ◽  
David Eliezer
Keyword(s):  
Alpha Synuclein ◽  
Low Ph ◽  
Charge Neutralization

scholarly journals Charge density of cation determines inner versus outer shell coordination to phosphate in RNA

2020 ◽  
Author(s):  
Hung T. Nguyen ◽  
D. Thirumalai
Keyword(s):  
Charge Density ◽  
Divalent Cations ◽  
Outer Shell ◽  
Divalent Ions ◽  
High Charge Density ◽  
Specific Manner ◽  
Effective Charges ◽  
Modes Of Interaction ◽  
Prevailing View ◽  
Phosphate Groups

Divalent cations are often required to fold RNA, which is a highly charged polyanion. Condensation of ions, such as Mg2+ or Ca2+, in the vicinity of RNA renormalizes the effective charges on the phosphate groups, thus minimizing the intra RNA electrostatic repulsion. The prevailing view is that divalent ions bind diffusively in a non-specific manner. In sharp contrast, we arrive at the exact opposite conclusion using a theory for the interaction of ions with the phosphate groups using RISM theory in conjunction with simulations based on an accurate Three Interaction Site RNA model. The divalent ions bind in a nucleotide-specific manner using either the inner (partially dehydrated) or outer (fully hydrated) shell coordination. The high charge density Mg2+ ion has a preference to bind to the outer shell whereas the opposite is the case for Ca2+. Surprisingly, we find that bridging interactions, involving ions that are coordinated to two or more phosphate groups, play a crucial role in maintaining the integrity of the folded state. Their importance could become increasingly prominent as the size of the RNA increases. Because the modes of interaction of divalent ions with DNA are likely to be similar, we propose that specific inner and outer shell coordination could play a role in DNA condensation, and perhaps genome organization as well.

scholarly journals Molecular mechanisms of human P2X3 receptor channel activation and modulation by divalent cation bound ATP

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Mufeng Li ◽  
Yao Wang ◽  
Rahul Banerjee ◽  
Fabrizio Marinelli ◽  
Shai Silberberg ◽  
...  
Keyword(s):  
Sensory Neurons ◽  
Molecular Mechanisms ◽  
Divalent Cations ◽  
Binding Pocket ◽  
P2x3 Receptor ◽  
Channel Activity ◽  
Divalent Ions ◽  
P2x3 Receptors ◽  
Channel Activation ◽  
Receptor Channel

P2X3 receptor channels expressed in sensory neurons are activated by extracellular ATP and serve important roles in nociception and sensory hypersensitization, making them attractive therapeutic targets. Although several P2X3 structures are known, it is unclear how physiologically abundant Ca2+-ATP and Mg2+-ATP activate the receptor, or how divalent cations regulate channel function. We used structural, computational and functional approaches to show that a crucial acidic chamber near the nucleotide-binding pocket in human P2X3 receptors accommodates divalent ions in two distinct modes in the absence and presence of nucleotide. The unusual engagement between the receptor, divalent ion and the γ-phosphate of ATP enables channel activation by ATP-divalent complex, cooperatively stabilizes the nucleotide on the receptor to slow ATP unbinding and recovery from desensitization, a key mechanism for limiting channel activity. These findings reveal how P2X3 receptors recognize and are activated by divalent-bound ATP, aiding future physiological investigations and drug development.

scholarly journals Effect of divalent ions on cariogenic biofilm formation

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Elena Laura Steiger ◽  
Julia Rahel Muelli ◽  
Olivier Braissant ◽  
Tuomas Waltimo ◽  
Monika Astasov-Frauenhoffer
Keyword(s):  
Biofilm Formation ◽  
Growth Parameters ◽  
Divalent Cations ◽  
Self Regulation ◽  
Antimicrobial Properties ◽  
Mutans Streptococci ◽  
Tooth Surface ◽  
Divalent Ions ◽  
Dental Biofilm ◽  
Calcium Magnesium

Abstract Background Divalent cations are able to interact with exopolysaccharides (EPS) and thus are capable to modify the structure and composition of dental biofilm. At the moment, little is known about the adsorption of metals by cariogenic EPS; thus, the aim of the present study was to evaluate the effect of divalent ions (calcium, magnesium, and zinc) on the growth and biofilm formation of mutans streptococci and on the dissolution of hydroxyapatite as well as to investigate their binding to the bacterial EPS. Results S. mutans strains used in this study show the highest tolerance towards calcium of the ions tested. Growth parameters showed no differences to control condition for both strains up to 100 mM; revealing natural tolerance to higher concentration of calcium in the surroundings. Although excessive levels of calcium did not impair the growth parameters, it also did not have a positive effect on biofilm formation or its binding affinity to EPS. Magnesium-saturated environment proved to be counterproductive as strains were able to dissolve more Ca2+ from the tooth surface in the presence of magnesium, therefore releasing excessive amounts of Ca2+ in the environment and leading to the progression of the disease. Thus, this supports the idea of self-regulation, when more Ca2+ is released, more calcium is bound to the biofilm strengthening its structure and however, also less is left for remineralization. Zinc inhibited bacterial adhesion already at low concentrations and had a strong antibacterial effect on the strains as well as on calcium dissolution; leading to less biofilm and less EPS. Additionally, Zn2+ had almost always the lowest affinity to all EPS; thus, the unbound zinc could also still remain in the surrounding environment and keep its antimicrobial properties. Conclusion It is important to maintain a stable relationship between calcium, magnesium and zinc as excessive concentrations of one can easily destroy the balance between the three in cariogenic environment and lead to progression of the disease.

scholarly journals Inhibition of K transport by divalent cations in sickle erythrocytes

Blood ◽  
1987 ◽  
Vol 70 (6) ◽  
pp. 1810-1815 ◽  
Author(s):  
C Brugnara ◽  
DC Tosteson
Keyword(s):  
Volume Regulation ◽  
Divalent Cations ◽  
Cell Swelling ◽  
Ionophore A23187 ◽  
Divalent Ions ◽  
Normal Cells ◽  
A Value ◽  
Sickle Erythrocytes ◽  
Mg Content ◽  
K Transport

Abstract We report experiments on the effect of intracellular divalent cations (Mg, Ca, Mn) on K transport and cell volume in erythrocytes from patients with homozygous hemoglobin S disease (SS cells). When CO- treated SS erythrocytes are exposed to the ionophore A23187, removal of cell Mg markedly stimulates K efflux, whereas increasing cell Mg inhibits K efflux. The Ki for the inhibition by internal free Mg is 0.38 +/- 0.10 mmol/L, a value comparable to the concentration of free Mg in normal cells (0.3 to 0.4 mmol/L). When swollen SS cells with increased Mg content were incubated in plasma-like medium, they shrunk much less than swollen SS cells with normal Mg content. Thus, elevation of cell Mg produces inhibition of swelling-induced K movement from SS cells. Internal Ca and Mn also inhibit K movement from SS cells. The inhibition of volume regulation by divalent cations suggests that increases in intracellular divalent ions, especially Mg, could induce a persistent degree of cell swelling in SS RBCs and thereby inhibit intracellular polymerization.

scholarly journals Gap junction dynamics: reversible effects of hydrogen ions.

1980 ◽  
Vol 87 (3) ◽  
pp. 719-727 ◽  
Author(s):  
C Peracchia ◽  
L L Peracchia
Keyword(s):  
Gap Junctions ◽  
Divalent Cations ◽  
Structural Characteristics ◽  
Freeze Fracture ◽  
Low Ph ◽  
Hydrogen Ions ◽  
Intact Cells ◽  
Lens Fibers ◽  
Fracture Appearance ◽  
Particle Packings

Reversible crystallization of intramembrane particle packings is induced in gap junctions isolated from calf lens fibers by exposure to 3 x 10(-7) M or higher [H+] (pH 6.5 or lower). The changes from disordered to crystalline particle packings induced by low pH are similar to those produced in junctions of intact cells by uncoupling treatments, indicating that H+, like divalent cations, could be an uncoupling agent. The freeze-fracture appearance of both control and low pH-treated gap junctions is not altered by glutaraldehyde fixation and cryoprotective treatment, as suggested by experiments in which gap junctions of both intact cells and isolated fractions are freeze-fractured after rapid freezing to liquid N2 temperature according to Heuser et al. (13). In junctions exposed to low pH, the particles most often form orthogonal and rhombic arrays, frequently fused with each other. A number of structural characteristics of these arrays suggest that the particles of lens fiber gap junctions may be shaped as tetrameres.

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