scholarly journals Polyelectrolyte Gels Formed by Filamentous Biopolymers: Dependence of Crosslinking Efficiency on the Chemical Softness of Divalent Cations

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 41
Author(s):  
Katrina Cruz ◽  
Yu-Hsiu Wang ◽  
Shaina A. Oake ◽  
Paul A. Janmey
Keyword(s):  
Alkaline Earth ◽  
Divalent Cations ◽  
Transition Metal Ions ◽  
Atomic Weight ◽  
Mechanical Resistance ◽  
Flexible Polymers ◽  
Interpenetrating Networks ◽  
Charge Densities ◽  
Polyelectrolyte Gels ◽  
Different Types

Filamentous anionic polyelectrolytes are common in biological materials. Some examples are the cytoskeletal filaments that assemble into networks and bundled structures to give the cell mechanical resistance and that act as surfaces on which enzymes and other molecules can dock. Some viruses, especially bacteriophages are also long thin polyelectrolytes, and their bending stiffness is similar to those of the intermediate filament class of cytoskeletal polymers. These relatively stiff, thin, and long polyelectrolytes have charge densities similar to those of more flexible polyelectrolytes such as DNA, hyaluronic acid, and polyacrylates, and they can form interpenetrating networks and viscoelastic gels at volume fractions far below those at which more flexible polymers form hydrogels. In this report, we examine how different types of divalent and multivalent counterions interact with two biochemically different but physically similar filamentous polyelectrolytes: Pf1 virus and vimentin intermediate filaments (VIF). Different divalent cations aggregate both polyelectrolytes similarly, but transition metal ions are more efficient than alkaline earth ions and their efficiency increases with increasing atomic weight. Comparison of these two different types of polyelectrolyte filaments enables identification of general effects of counterions with polyelectrolytes and can identify cases where the interaction of the counterions and the filaments exhibits stronger and more specific interactions than those of counterion condensation.

Stardust

2010 ◽  
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Oxygen Atom ◽  
Simple Formula ◽  
Atomic Weight ◽  
Protons And Neutrons ◽  
Different Types ◽  
A Minor ◽  
Tiny Part

What is a pebble? It is a wave-smoothed piece of rock, and a complex mineral framework, and a tiny part of a beach, and a capsule of history too. All these guises have their own stories, and these we shall come to. But from yet another viewpoint the pebble is a collection of atoms of different kinds—of many, many atoms—and that might be the best way to start. Considering it at this level, it is a little like taking the equivalent of a large sack of mixed sweets and separating them out into their different types. How big a sack, though? Or, to put it another way, how many atoms in our pebble? There is a simple formula for estimating the number of atoms in a piece of anything. The basic idea was first glimpsed by Amadeo Avogadro, Count of Quereta and Cerreto in Piedmont, now Italy: scholar, savant and teacher (though his teaching was briefly interrupted because of his revolutionary and republican leanings—a little impolitic when the king lives nearby). Avogadro was interested in how the particles (atoms, molecules) in matter are related to the volume and mass of that matter. Years later, his early studies were refined by other scientists and the upshot, a century or so later, came to be called Avogadro’s constant. Thus, in what is called the mole of any element there are a little over 600,000 million million million—or, to put it more briefly, 623—atoms. A mole here is not a small furry burrowing quadruped, or a minor skin blemish, but the atomic weight of any element expressed in grams. For oxygen a mole would therefore be 16 grams, as 16 is its atomic weight, an oxygen atom having a total of 16 protons and neutrons in its nucleus. The kitchen scales tell us that our pebble weighs some 50 grams. About half of it is made up of oxygen, and much of the rest is silicon (atomic weight 28) and aluminium (atomic weight 27) with a scattering of other elements, most somewhat heavier. A judiciously averaged atomic weight might therefore reasonably be something like 25.

scholarly journals P-selectin mediates Ca(2+)-dependent adhesion of activated platelets to many different types of leukocytes: detection by flow cytometry

Blood ◽  
1992 ◽  
Vol 80 (1) ◽  
pp. 134-142 ◽  
Author(s):  
LG de Bruijne-Admiraal ◽  
PW Modderman ◽  
AE Von dem Borne ◽  
A Sonnenberg
Keyword(s):  
T Cells ◽  
Divalent Cations ◽  
Phosphatidyl Inositol ◽  
Cell Types ◽  
Inhibitory Effect ◽  
Immunofluorescence Assay ◽  
Cd8 Cells ◽  
Activated Platelets ◽  
Selectin Ligands ◽  
Different Types

Abstract Previous studies have shown that thrombin-activated platelets interact through the P-selectin with neutrophils and monocytes. To identify other types of leukocytes capable of such an interaction, eosinophils, basophils, and lymphocytes were isolated from whole blood. Binding of these cells to activated platelets was examined in a double immunofluorescence assay and the results show that activated platelets not only bind to neutrophils and monocytes, but also to eosinophils, basophils, and subpopulations of T lymphocytes. Using monoclonal antibodies (MoAbs) specific for subsets of T cells, we could further demonstrate that the T cells which bind activated platelets are natural killer (NK) cells and an undefined subpopulation of CD4+ and CD8+ cells. All these interactions were dependent on divalent cations and were completely inhibited by an MoAb against P-selectin. Thus, P- selectin mediates the binding of activated platelets to many different types of leukocytes. Studies with leukocytes treated with proteases or neuraminidase have shown that the structures recognized by P-selectin are glycoproteins carrying sialic acid residues. Because the loss of binding of activated platelets to neuraminidase-treated neutrophils was almost complete, but only partial to treated eosinophils, basophils, and monocytes, the latter cell types may have different P-selectin ligands in addition to those present on neutrophils. We found that two previously identified ligands for P-selectin, the oligosaccharides Le(x) and sialyl-Le(x), had little or no inhibitory effect on adhesion of activated platelets to leukocytes and that binding was not inhibited by MoAbs against these oligosaccharides. In addition, there was no correlation between the expression of Le(x) on several cell types and their capacity to bind activated platelets. In contrast, the expression of sialyl-Le(x) on cells was almost perfectly correlated with their ability to bind activated platelets. Thus, while Le(x) cannot be a major ligand for P-selectin, a possible role for sialyl-Le(x) in P- selectin-mediated adhesion processes cannot be dismissed. Finally, activated platelets were found to bind normally to monocytes and neutrophils of patients with paroxysmal nocturnal hemoglobulinuria (PNH) and to neutrophils from which phosphatidyl inositol (PI)-linked proteins had been removed by glycosylphosphatidyl inositol-specific phospholipase C (GPI-PLC) digestion. This suggests that at least part of the P-selectin ligands on these cells are not GPI-anchored.

Endonuclease Active Site Plasticity Allows DNA Cleavage with Diverse Alkaline Earth and Transition Metal Ions

2011 ◽  
Vol 6 (9) ◽  
pp. 934-942 ◽  
Author(s):  
Kommireddy Vasu ◽  
Matheshwaran Saravanan ◽  
Valakunja Nagaraja
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Active Site ◽  
Dna Cleavage ◽  
Alkaline Earth ◽  
Transition Metal Ions

Behavior of Polyelectrolyte Gels in Concentrated Solutions of Highly Soluble Salts

MRS Advances ◽  
2020 ◽  
Vol 5 (17) ◽  
pp. 907-915 ◽  
Author(s):  
Jessica L. Sargent ◽  
Xunkai Chen ◽  
Mitchell C. Brezina ◽  
Sebastian Aldwin ◽  
John A. Howarter ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
High Performance Concrete ◽  
Group Versus ◽  
Transition Metal Ions ◽  
Main Group ◽  
Ion Concentration ◽  
Polyelectrolyte Gels ◽  
Counter Ion ◽  
Versus Transition

ABSTRACTIonic hydrogels are an abundant class of materials with applications ranging from drug delivery devices to high performance concrete to baby diapers. A more thorough understanding of interactions between polyelectrolyte networks and ionic solutes is critical as these materials are further tailored for performance applications in highly targeted ionic environments. In this work, we seek to develop structure-property relationships between polyelectrolyte gels and environments containing high concentrations of multivalent ions. Specifically, this work seeks to elucidate the causes behind differences in hydrogel response to divalent ions of main group metals versus transition metals. PANa-co-PAM hydrogels containing low and high fractions of ionic groups are investigated in solutions of DI water, NaCl, CaCl2, and CuSO4 at concentrations ranging from 5 to 100 mM in order to understand 1) the transient or permanent nature of crosslinks produced in these networks by divalent counter-ions, 2) the role of polymer ionic content in these interactions, and 3) how these interactions scale with salt concentration. Gravimetric swelling and mechanical compression testing are employed to characterize water and salt-swollen hydrogels in order to develop guiding principles to control and manipulate material properties through polymer-counter-ion interactions. The work presented here confirms the formation of permanent crosslinks by transition metal ions, offers explanation for the behavioral discrepancy observed between ionic hydrogels and main group versus transition metal ions, and illustrates how such hydrogel properties scale with counter-ion concentration.

scholarly journals Exchange of Some Divalent Metal Cations and Their Effect on the Dissociation of Iron(III) Phosphate

1996 ◽  
Vol 13 (4) ◽  
pp. 241-260 ◽  
Author(s):  
S. Mustafa ◽  
A. Naeem ◽  
N. Rehana ◽  
T. Hussain
Keyword(s):  
Transition Metal ◽  
Thermodynamic Parameters ◽  
Alkaline Earth ◽  
Dissociation Constants ◽  
Ph Value ◽  
Transition Metal Ions ◽  
Divalent Metal ◽  
Solution Ph ◽  
Divalent Metal Cations ◽  
Titration Data

Potentiometric titrations of iron(III) phosphate have shown an apparently weak monobasic acid behaviour towards alkali, alkaline earth and divalent transition metal ions. The selectivity sequence and dissociation of the exchanger was found to increase in the order Cu2+ > Zn2+ > Ni2+ > Ca2+ > K+. The dissociation constants of iron(III) phosphate have been determined from Potentiometric titration data in the temperature range 303–323 K. In addition, the exchange of Cu2+, Zn2+ and Co2+ on iron(III) phosphate and the effect of these ions on dissociation were also studied as a function of concentration, temperature and solution pH value. The thermodynamic parameters ΔH0, ΔS0 and ΔG0 for the dissociation of iron(III) phosphate are also presented.

scholarly journals Structure-guided DNA–DNA attraction mediated by divalent cations

2020 ◽  
Author(s):  
Amit Srivastava ◽  
Raju Timsina ◽  
Seung Heo ◽  
Sajeewa W Dewage ◽  
Serdal Kirmizialtin ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Alkaline Earth ◽  
Divalent Cations ◽  
Random Sequence ◽  
Earth Metal ◽  
Alkaline Earth Metal ◽  
Sequence Dependent ◽  
Phosphate Backbone ◽  
Alkaline Earth Metal Ions

Abstract Probing the role of surface structure in electrostatic interactions, we report the first observation of sequence-dependent dsDNA condensation by divalent alkaline earth metal cations. Disparate behaviors were found between two repeating sequences with 100% AT content, a poly(A)-poly(T) duplex (AA-TT) and a poly(AT)-poly(TA) duplex (AT-TA). While AT-TA exhibits non-distinguishable behaviors from random-sequence genomic DNA, AA-TT condenses in all alkaline earth metal ions. We characterized these interactions experimentally and investigated the underlying principles using computer simulations. Both experiments and simulations demonstrate that AA-TT condensation is driven by non-specific ion–DNA interactions. Detailed analyses reveal sequence-enhanced major groove binding (SEGB) of point-charged alkali ions as the major difference between AA-TT and AT-TA, which originates from the continuous and close stacking of nucleobase partial charges. These SEGB cations elicit attraction via spatial juxtaposition with the phosphate backbone of neighboring helices, resulting in an azimuthal angular shift between apposing helices. Our study thus presents a distinct mechanism in which, sequence-directed surface motifs act with cations non-specifically to enact sequence-dependent behaviors. This physical insight allows a renewed understanding of the role of repeating sequences in genome organization and regulation and offers a facile approach for DNA technology to control the assembly process of nanostructures.

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