Gels physical integrity

Alkaline solntions are detrimental to the physical integrity of preparations containing Spirulina silica dne to the propensity of silica gel to hydrolyze in alkaline solntion. The addition of aluminnm ions represents one approach for overcoming the instabihty of this algal silica polymer at high pH. 

If one accepts that the physical integrity of these gels is attributable to some form of self-association of solvated polymer, as suggested by the earlier investigators, then it follows that a must be an averaged value of two polymer fractions, [182], i.e. the fraction (y) that underwent self-association, and the rest (1 — y) that did not. Thus a should be expressed by ... 

In addition to measurements of how much and what type of chemical species are present, modification of the MR experiment allows us to identify the physical state of a given species (e.g., gas, liquid, gel, and solid) and to quantify temperature and any incoherent and/or coherent transport processes within the system. By integrating any of these measurements into an imaging experiment, we can spatially map these quantities or exploit the effect of these characteristics on the magnitude or frequency of the MR signal to preferentially observe sub-populations of spins within the system. In this latter application we are exploiting the so-called contrast mechanisms in the image acquisition. These concepts are illustrated in Sections II.B II.D. 

Although DSC and other physical techniques have made considerable contributions to the elucidation of the nature of lipid-protein interactions, several outstanding questions remain. For example, it remains to be dehnitively determined whether some integral, transmembrane proteins completely abolish the cooperative gel-to-liquid-crystalline phase transition of lipids with which they are in direct contact or whether only a partial abolition of this transition occurs, as is suggested by the studies of the interactions of the model transmembrane peptides with phospholipids bilayers (see above). The mechanism by which some integral, transmembrane proteins perturb the phase behavior of very large numbers of phospholipids also remains to be determined. Finally, the molecular basis of the complex and unusual behavior of proteins such as the concanavalin A receptor and the Acholeplasma laidlawii B ATPase is still obscure (see Reference 17). 

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