Nucleic acids Macromolecules with components

Pentoses are of prime importance for contemporary organisms as structural components of nucleic acids. The existence of the primordial RNA world, in which RNA is suggested to act as a catalyst as well as an informational macromolecule, assumes a large prebiotic source of ribose. Alternatively, the possible existence of pre-RNA molecules with backbones different from ribose phosphate has been considered [3]. 

Structural models of protein and nucleic acid molecules derived by X-ray crystallography are exttemely interesting in themselves, each being a representative member of some architectural class of macromolecule shaped by evolutionary time and process toward the optimal completion of a specific cellular or metabolic task. They are nevertheless static objects. Because the catalytic functions they perform depend on dynamic events involving the interaction of the macromolecules with substrates, effectors, inhibitors, and other cellular components, we are constantly searching for techniques that will allow us to visualize the macromolecules in some intermediate stages of a biochemical or physiological activity. 

Biotransformation begins with the transient formation of a reactive intermediate, whose lifetime is long enough to allow an attack on cellular components. This occurs when a reactive intermediate (such as a radical or a carbenium ion) is formed and reacts rapidly with nucleophilic functions in cellular macromolecules (such as unsaturated lipids, proteins, nucleic acids), thus leading to their degradation and finally to cellular necrosis. 

The basis of RAMs is the simultaneous size exclusion of macromolecules and extraction/enrichment of low-molecular-weight compounds into the interior phase via partition. The outer surface of the particles, which is in contact with biological matrix components such as proteins and nucleic acids, possesses a special chemistry to prevent adsorption of these molecules. Macromolecules can be excluded by a physical barrier, the pore diameter, or by a chemical diffusion barrier created by a protein (or polymer) network at the outer surface of the particle. RAMs can be classified according to the protein exclusion mechanism used into the following two groups RAM with a... 

The study of membrane and nucleic acid systems presents greater complexities. The study of lipids and insoluble membrane proteins in association with them can be achieved in solution scattering [75,76] by the use of lipid vesicles to solubilize the system of interest. Membrane proteins can alternatively be studied by solubilization using detergent micelles. The exception to this generalization is the group of plasma hpoproteins which are readily soluble in aqueous buffers. Systems with nucleic acids (i.e. protein-nucleic acid complexes, viruses, ribosomes and chromatin) [24-27,77,78] are not affected by these solubihty problems. However, lipid and nucleic acid systems are both further complicated in their analyses by the polyionic character of these macromolecules. Particular care is required concerning the partial specific volumes of the individual components to be used within the system of interest. 

---