Nonspecific promoters

Base deamination is accelerated by nitrous acid and sodium bisulfite. Nitrous acid nonspecifically promotes base deamination in both double-stranded and single-stranded DNA. In contrast, sodium bisulfite specifically promotes cytosine deamination in single-stranded DNA. Some single-stranded regions do exist in cellular DNA, at least temporarily—for example, during transcription. In some cases, sodium bisulfite is used as a food additive. It is also used in the wine industry. 

A common choice of crosslinker for this type of reaction is sulfo-SMCC, which has been used extensively for antibody conjugation (Chapter 20, Section 1.1). A better option for dendrimer conjugation is to use a similar crosslinker design, but one that contains a hydrophilic PEG spacer arm to promote dendrimer hydrophilicity after modification. Derivatization of an amine-dendrimer with a NHS-PEG-maleimide can create an intermediate that is coated with water-soluble PEG spacers. This modification helps to mask any potential for nonspecific interactions that the PAMAM surface may have, while providing terminal thiol-reactive maleimides for coupling ligands (Figure 7.10). 

Hydrophobin-protein interactions include those bacterial surface components that promote adhesion to host cell surfaces via hydrophobic moieties that are often thought to be nonspecific (Rosenberg and Doyle, 1990 Rosenberg and Kjelleberg, 1986 Rosenberg et al, 1996). 

For QM-MSP, first the promoter regions of several genes will be amplified using primes that correspond to the CG-free regions (45). Then, 1 pL of the diluted PCR product (30-50 times) is used as the template in real-time QM-MSP to quantify the methylated and unmethylated template in separate reactions using methylation- or nonmethylation-specific primers. The benefits of this method are that (1) the instability of bisulfite-modified DNA is remedied using an initial round of PCR (2) nonspecific products that compromise the accuracy of SYBR green-based real-time PCR are eliminated in the second-round PCR (3) the likelihood of the development of primer dimers is minimized as the first-round PCR product is diluted 50 times and a minimal amount of MSP primers is used in the second-round PCR (4) the amount of the precious DNA used in this approach is substantially less than in the other methods. 

Pauli, T.T., Haykinson, M.J., and Johnson, R.C. (1993) The nonspecific DNA-binding and -bending proteins HMGl and HMG2 promote the assembly of complex nucleoprotein structures. Genes Dev. 7, 1521-1534. 

Mice were treated twice weekly for 42 weeks by application of one drop of a 10% solution of phenol in benzene to the shaved dorsal skin after 52 weeks, there were papillomas in 5 of 14 mice, and a single fibrosarcoma appeared at 72 weeks. Phenol, as a nonspecific irritant, may promote development of tumors when applied repeatedly to the skin in large amounts. ... 

The idea of solvent polarity refers not to bonds, nor to molecules, but to the solvent as an assembly of molecules. Qualitatively, polar solvents promote the separation of solute moieties with unlike charges and they make it possible for solute moieties with like charges to approach each other more closely. Polarity affects the solvent s overall solvation capability (solvation power) for solutes. The polarity depends on the action of all possible, nonspecific and specific, intermolecular interactions between solute ions or molecules and solvent molecules. It covers electrostatic, directional, inductive, dispersion, and charge-transfer forces, as well as hydrogen-bonding forces, but excludes interactions leading to definite chemical alterations of the ions or molecules of the solute. 

Another factor influencing nonspecific tissue distribution is the carbohydrate portion of the IgG molecule, which is attached to the therapeutic protein via an N-linked glycan in the constant domain (Fc). Loss of terminal sialylated residues on the carbohydrate of IgG exposes galactose and promotes receptor-mediated binding of IgG to hepatocytes. Consequently this results in an increase in nonspecific distribution to the liver. Details of desialyation of IgG and its consequences are discussed in Chapter 10. Other glycoproteins may exert similar mechanisms of nonspecific distribution. 

Lactose appears to promote the absorption of calcium but this is probably due to a nonspecific increase in intestinal osmotic pressure, an effect common to many sugars and other carbohydrates, rather than a specific effect of lactose. 

Administration of streptomycin intramuscularly is the method of choice for treating systemic infections. Oral forms of streptomycin or dihydrostreptomycin, frequently combined with sulfonamide drugs and other compounds, are also used in animals for treatment of enteric infections. In addition, streptomycin is used as a feed additive for growth promotion purposes. In some countries, the combination of streptomycin with procaine penicillin is used as an initial nonspecific therapy in farm animals, and in intramammary applications for treatment of mastitis. Intramuscular dosages are in the range 5-10 mg/kg bw, while oral dosages are 20 mg/kg bw. Dihydrostreptomycin is also used in veterinary medicine in intramammary and topical treatments. 

Poirier, M.C., De Cicco, B.T. Lieverman. M.W (1975) Nonspecific inhibition of DNA repair synthesis by tumor promoters in human diploid fibroblasts damaged with V-acetoxy-2-acetylaminofluorene. Cancer Res.. 35. 1392-1397... 

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