Selection of Receptor

In general terms, a receptor is defined as an ecosystem of interest that is potentially polluted by a certain load of heavy metal. 

Soil microbes. Effects include reduced microbial biomass and/or species diversity, thus affecting microbial processes such as enzyme synthesis and activity, litter decomposition, associated with carbon and nitrogen mineralization, and soil respiration  

Soil fauna, including invertebrates, like nematodes and earthworms. Effects are connected with biodiversity, productivity and biomass changes  

Vascular plants including trees. Effects are related to HM toxicity, such as the reduced growth of roots and shoots, elevated concentrations of starch and total sugar and decreased nutrient contents in foliar tissues and depressed biochemical activity  

Terrestrial fauna, such as birds, mammals, or domestic animals. Effects are heavy metals accumulation followed by possible disturbance of physiological and biochemical reactions and metabolisms. Bioaccumulation ofCd, Hg and Cu in the food web is the most important concern. 

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Such reconstitutional approaches suffer from two problems, however. First, the selectivity of receptor-G-protein coupling in their native cell environment depends not only on the relative affinities of the receptor for different G-proteins, but also on the relative proportions and availability... 

Clapham, D. E. and Neer, E., G-protein Py subunits, Anna. Rev. Pharmacol. Toxicol., 37, 167-203, 1997. Gudermann, T., Kalkbrenner, F., and Schultz, G., Diversity and selectivity of receptor-G-protein interaction, Annu. Rev. Pharmacol. Toxicol., 36, 429-459, 1996. 

FABMS has been used as a semiquantitative indication of the selectivity of receptors for particular guest metal cations (Johnstone and Rose, 1983). The FABMS competition experiment on [7] with equimolar amounts of the nitrates of sodium, potassium, rubidium and caesium gave gas-phase complex ions of ([7] + K)+ ion (m/z 809) and a minor peak ([7] + Rb)+ ion (m/z 855) exclusively. The relative peak intensities therefore suggested a selectivity order of K+ Rb+ Na+, Cs+, indicative of the bis-crown effect, the ability of bis-crown ether ligands to complex a metal cation of size larger than the cavity of a single crown ether unit, forming a sandwich structure. 

Kostenis, E., Degtyarev, M. Y., Conklin, B. R., and Wess, J. (1997a). The N-terminal extension of Gaq is critical for constraining the selectivity of receptor coupling. J. Biol. Chem. 272, 19107-19110. 

However, some receptors are constitutively expressed in the nucleus and this type of receptor would not be amenable to a nuclear translocation assay. The activities of nuclear receptors may be dependent upon complex interactions with a number of coregulatory proteins, commonly known as coactivators or corepressors, and modifications by post-translational means. Cell type-specific expression levels of receptors and coregulators may contribute to some, but not all, of the molecular bases for gene and functional selectivity of receptor activity. Therefore selecting a cell line that expresses both the target receptor and the necessary cofactors may be required to design an appropriate assay. 

A third theme is that viruses are adaptable in their selection of receptors. Given the choice of a wide variety of host cell surface molecules as potential receptors, different strains or serotypes within the same virus... 

Hollenberg, M.D., Saifeddine,M., Al-Ani, B. and Kawabata,A. (1997) Proteinase-activated receptors structural requirements for activity, receptor cross-reactivity, and receptor selectivity of receptor-activating peptides. Can. J. Physiol. Pharmacol. 75 832-841. 

Positive selection of receptors that recognize PC-associated molecular patterns... 

This short review has attempted to summarize recent advances in molecular and ionic recognition. New developments in this exciting field are continuously being made. The possibilities of structural variations in improving the complexation selectivities of receptors toward specific guests will undoubtedly be accomplished in the future, benefiting the construction of new man-made chemical sensors. 

Rogers, G. N., Pritchett, T. J., Lane, J. L., and Paulson, J. C., 1983b, Differential sensitivity of human, avian, and equine influenza A viruses to a glycoprotein inhibitor of infection Selection of receptor specific variants. Virology 131 394-408. 

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