Charged patches

Fig. 3. Adsorbed cationic polymer forming charge patch on particle surface (32).

Hays measured the current associated with electrically charged 99 p.m diameter particles of styrene divinylbenzene particles as these particles traversed gaps of 520 and 137 p.m separating two parallel electrodes. Based on these results. Hays [81 ] argued for the existence of locally charged patches on the particles. 

Gady found that, depending on the charge of the particle, van der Waals forces dominated over the forces associated with electrostatically charged patches when the particle-to-substrate separation was between 3 and 10 nm, depending on the particle charge. In addition, he found that the distance at which the snap-together occurred required that van der Waals forces dominate over electrostatic. In all his measurements, however, a component of the total attractive force, even at close separations, was observed to be electrostatic in nature. 

Ren Q, Gorovsky MA (2001) Histone H2A.Z acetylation modulates an essential charge patch. Mol Cell 7 1329-1335... 

For filter belt presses and centrifuges, resistance to shear and mechanical pressure is the most important parameter. In general, floes produced by charge patch neutralization are stronger than those produced by inorganic salts alone. 

However, proteins are almost always charged (Dello Orco et al., 2005), for otherwise they would drop out of the solution, that is, phase separate macroscopically. Indeed, this is what usually happens near the isoelectric point of the proteins, i.e. their point of zero net charge. If two proteins bind to become part of an assembly, charged patches on them get on average closer together and hence repel each other when of the same sign. In other words, Coulomb repulsion between the proteins... 

Crystallographic analysis has provided us with a detailed structure of hCp on the other hand, essentially all of the structure-function analyses have been done on FetSp. Also, except for the copper site structural homology, the two proteins are quite different. hCp is composed of six plastocyanin-like domains (plastocyanin is a type 1 copper-containing protein) that are arranged in a trigonal array (Zaitseva et al., 1996). One result of this domain replication is a conformational fold that produces a distinct, negatively charged patch on the protein surface adjacent to the catalytically active type 1 Cu(II). This copper atom is in domain 6. (Domains 2 and 4 contain type 1-like copper sites that do not participate in the ferroxidase reaction.) Lindley et al. (1997) have proposed that this... 

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