Non electrostatic attraction

Polyelectrolytes. The most striking feature of polyelectrolytes is that due to the electrostatic repulsion between the segments, the formation of thick adsorbed layers is prevented. Polyelectrolytes tend to adsorb in rather flat conformations. If adsorbent and polyelectrolyte bear opposite charges, this attraction can be of an electric (coulombic) nature if the charges have the same sign, adsorption takes place only if the non-electrostatic attraction outweighs the electrostatic repulsion (Lyklema, 1985). 

Further, in the case of virtually non-existent ion-solvent interactions (low degree of solvation), so that solute-solute interactions become more important, Kraus and co-workers47 confirmed that in dilute solutions ion pairs and some simple ions occurred, in more concentrated solutions triple ions of type M+ X M+ orX M+X andinhighly concentrated solutions even quadrupoles the expression triple ions was reserved by Fuoss and Kraus48 for non-hydrogen-bonded ion aggregates formed by electrostatic attraction. 

These electrostatic attractions act in all directions. Thus, ionic crystalline solids consist of metal ions are surrounded by non-metal ions and non-metal ions surrounded by metal ions. Therefore, ionic solids do not have a molecular structure. 

Nonspecific binding of probe to nontarget DNA and RNA. may provide interfering background. Also, cellular electrostatic forces may non specifically attract the probe. 

The most frequently used protein assay is based on a method after Bradford (Bradford, 1976), which combines a fast and easily performed procedure with reliable results. However, the Bradford assay has sensitivity limitations and its accuracy depends on comparison of the protein to be analyzed with a standard curve using a protein of known concentration, commonly bovine serum albumin (BSA). Many commercially available protein assays such as those from Pierce or BioRad rely on the Bradford method. The assay is based on the immediate absorbance shift from 465 nm (brownish-green) to 595 nm (blue) that occurs when the dye Coomassie Brilliant Blue G-250 binds to proteins in an acidic solution. Coomassie dye-based assays are known for their non-linear response over a wide range of protein concentrations, requiring comparison with a standard. The dye is assumed to bind to protein via an electrostatic attraction of the dye s sulfonic groups, principally to arginine, histidine, and lysine residues. It also binds weakly to the aromatic amino acids, tyrosine, tryptophan, and phenylalanine via van der Waals forces and hydrophobic interactions. 

DFT studies on the facial selectivities of six Johnson-Claisen rearrangements (Scheme 5) analogous to those used in the synthesis of gelsemine have reproduced experimental results in five out of the six cases, but have predicted formation of the same product (21) in all six reactions. The selectivity in these cases has been attributed to a combination of steric repulsions between vinylic proton H(l) and allylic proton H(7) or H(14), and electrostatic attractions between C(l) and the oxetane hydrogens C(5)-H and C(16)-H. Both of these factors, however, apparently predicted the non-observed product in the conversion of (22) into (23)22... 

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