DNA functions

Deoxyribonucleic acid (DNA) serves as a template for the synthesis of nucleic acids. Ribonucleic acid (RNA) executes protein synthesis and thus permits cell growth. Synthesis of new DNA is a prerequisite for cell division. Substances that inhibit reading of genetic information at the DNA template damage the regulatory center of cell metabolism. The substances listed below are useful as antibacterial drugs because they do not affect human cells. 

Azomydn (nitroimidazole] derivatives, such as metronidazole, damage Ltillmann, Color Atlas of Pharmacology 

Rifampin inhibits the bacterial enzyme that catalyzes DNA template-directed RNA transcription, i.e DNA-de-pendent RNA polymerase. Rifampin acts bactericidally against mycobacteria (M. tuberculosis, M. leprae), as well as many gram-positive and gram-negative bacteria It is well absorbed after oral ingestion. Because resistance may develop with frequent usage, it is restricted to the treatment of tuberculosis and leprosy (p. 280). 

Rifampin is contraindicated in the first trimester of gestation and during lactation. 

Rifabutin resembles rifampin but may be effective in infections resistant to the latter. 

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Mitchell GP, Mirkin CA, Letsinger RL (1999) Programmed assembly of DNA functionalized quantum dots. J Am Chem Soc 121 8122-8123... 

Dwyer C, Guthold M, Falvo M, Washburn S, Superfine R, Erie D (2002) DNA-functionalized single-walled carbon nanotubes. Nanotechnology 13 601-604. 

Hazani M, Naaman R, Hennrich F, Kappes MM (2003) Confocal fluorescence imaging of DNA-functionalized carbon nanotubes. Nano Lett. 3 153-155. 

Any interference with protein synthesis, through alteration of DNA function, as just mentioned, or by damage to the structures called endoplasmic reticulum, the site of such synthesis, can be devastating in many ways, because proteins are not only essential for the many structures of cells, but also because they are the body s catalysts (enzymes) for all its essential biochemical processes. 

The nucleic acids play a central role in the storage and expression of genetic information (see p. 236). They are divided into two major classes deoxyribonucleic acid (DNA) functions solely in information storage, while ribonucleic acids (RNAs) are involved in most steps of gene expression and protein biosynthesis. All nucleic acids are made up from nucleotide components, which in turn consist of a base, a sugar, and a phosphate residue. DNA and RNA differ from one another in the type of the sugar and in one of the bases that they contain. 

DNA, functional groups of nucleic acid bases are completely dehydrated and located inside the hydrophobic domain of duplex, forming efficient interhelix hydrogen bonds as shown in Figure 6. 

DNA-functionalized Au NPs have been prepared using nucleic acids bearing n-alkylthiol groups [154]. Another study showed that thiolated single-stranded nucleic acids of different lengths (8 to 135 bases) can be attached to 10 nm size Au NPs at different Au nucleic acid ratios [155]. 

Size is a key parameter for DNA-functionalized particles in that it dictates the strategy needed to achieve the desired particle functionalization. 

Fig. 37 Linear chain formation of DNA-coated paramagnetic polystyrene colloids with the different self-protection schemes displayed in Fig. 33. By using an external magnetic field, DNA-functionalized particles were brought together into linear chains, after which the temperature was lowered below the association temperature for beads, and the field turned off. (a) Representative microscopy picture of the resulting chain structures immediately after switching off the magnetic field, (b-d) Chains after 1 h at the specified temperature for particles functionalized with sticky end sequences able to form both loops and hairpins (b, c) or only loops (d). The degree of aggregation of chains in (d) is intermediate between the unprotected, branched chains in (b) and the perfectly linear, protected chains in (c). Adapted with permission from [157]...

In most of the cases, one is interested in having a relatively high DNA coverage of the particle surface. However, very recently some interest arose as to whether DNA functionalization could be used to achieve a completely different aim the realization of colloidal particles with a limited number of active spots, so to break the spherical symmetry of the interaction potential. Within this limit a strong directionality of the bonds is introduced, which mimics the chemical valence of molecules at much longer length-scales [166, 167]. 

Mechanism of Action. Primaquine appears to impair DNA function in susceptible parasites. The exact manner in which this occurs is unknown. 

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