Living Rainbow H2O by Mae-Wan Ho

Author:Mae-Wan Ho [Ho, Mae-Wan]
Language: eng
Format: epub, azw3, pdf
Tags: Science, Life Sciences, Biochemistry, Biophysics, Cell Biology
ISBN: 9789814390897
Google: M1bR3LLnv5kC
Amazon: 9814390895
Publisher: World Scientific
Published: 2012-07-14T22:00:00+00:00

stability and interactions between proteins in alkali salt solutions are predominantly through hydration water molecules. But this turns out not to be true, as we shall see in Chapter 23.

Why Quantum Jazz is Possible The most important explanation offered by Collins’ theory is of why the ions present inside cells are so different from those outside, which has long puzzled biologists (see Table 17.1).7 Intracellular fluid has high concentrations of potassium and magnesium cations and phosphate and sulphate anions, and very low concentrations of sodium and chloride. The converse is true of extracellular fluid: low in potassium, magnesium, phosphate, and sulphate, and high in sodium and chloride. While there appears to be not much difference between extracellular and intracellular calcium, most of the intracellular calcium is bound, with only 10−7 M free Ca2+ most of the time, except for very transient, local increases associated with signal transduction.

Apart from the inorganic ions, there are some 6.5 mM of proteins present in the cytoplasm rich in carboxylate anions in their side chains (equivalent to ten times in ionic concentration). As Collins pointed out,8 the intracellular ions are optimized for mismatches in water affinities, so as to maintain high solubility of the proteins and other constituents of the cytoplasm at all times. That’s why quantum jazz of the rainbow ensemble is possible.

Increasingly, protein-folding disorders are being identified, including Alzheimer’s disease, Parkinson’s disease, transmissible spongiform encephalopathies (mad cow disease), Huntington’s disease, and type II diabetes, which have been linked to ligand binding and hydration.9 In all likelihood, these diseases represent different failures in keeping almost all the molecular participants in cellular biochemistry dancing with water at any one time, so some of them end up salting out at inappropriate places. (That’s why the structure of water is so important, and everyone should be reading this book!)

In view of the high affinity of sodium ions for carboxylate, the intracellular concentration of sodium is kept very low, and, it is generally believed, by an Na+/K+-ATPase that pumps sodium out of the cell in exchange for potassium. RNA and DNA and membrane phospholipids are phosphate diesters built upon the phosphate anion. Phosphate and carboxylate anions are the fundamental ions of the cell. Phosphate is also important in metabolism, where many small molecules are phosphorylated to keep them in the cell and to provide a “handle” for enzymes to bind onto (very likely mediated by water). The nucleotide triphosphates (adenosine triphosphate, ATP, and others) play an apparently critical and essential role in energy metabolism. (We shall see how critical ATP is in Chapter 23.) Phosphate functions as a reversible marker in signal transduction, with phosphorylation activating or deactivating proteins. As seen in Chapter 16, phosphate groups bind strongly to water as hydrogen acceptors, and Ca2+, which is well matched to carboxylate, as well as to phosphate, acts as a dehydrating agent. This suggests that hydration and dehydration of proteins and metabolites may be one important avenue to signal transduction.

Ca2+ readily pairs with carbonates and inorganic phosphates, forming insoluble complexes that organisms need, but only in the right place and at the right time.

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