The reactivity of molecules towards water, the most abundant constituent of cells, is designated hydropathy. Hydrophilic parts of molecules mix well with water and the hydrophobic parts repel or are repelled by water (Kyte and Doolittle, 1982). Nucleotides are amphiphilic, containing the hydrophilic sugars and phosphates and the more hydrophobic nucleobases. Amino acids span the whole hydropathy range so that proteins depict complex organization. Protein aggregates tend to form globules with membrane-like surfaces, for which the contribution of lipids may be accessory. The same principles governing the internal organization and folding of the macromolecules apply to the formation of associations between proteins or between proteins and nucleic acids. The nucleoprotein system is tightly associated: proteins and nucleic acids are both very sticky and form aggregates, the components communicating with each other in almost contiguity.
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