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Local response coefficients
Often we can collect data files which pertain only to individual chemical species. The most simple case is when the chemical species are first separated by using a physico-chemical separation technique (chromatography, electrophoresis), and subsequently some instrumental signal is measured for each species separately.
Another possibility is to have available a spectroscopic technique which (without separation of chemical components) can provide individual signals for several species present in the reaction mixture (e.g., multi-wavelength UV/VIS spectroscopy).
In both cases we can use the keyword response listed after the name of the corresponding datafile to assign molar response coefficients.
Example: Gel shift assay.
A mixture of radioactive DNA, a DNA-binding protein, and two different types of protein-DNA complexes (PDNA and PDNA) is separated by electrophoresis. Radioactive areas of the gel plate, each corresponding to a different chemical species, are quantified by using a phosporimetric technique. Each datafile (P-DNA.TXT and P2-DNA.TXT) then contains pairs of data point, where the independent variable is the total concentration of the protein, and the dependent variable is the experimental signal from the phosphorimeter.
[mechanism] DNA + P <==> P.DNA : K1 dissoc P.DNA + P <==> P2.DNA : K2 dissoc ... [equilibria] variable P file P-DNA.TXT | response P.DNA = 1234.00 file P2-DNA.TXT | response P2.DNA = 5678.00
In the above example, it is important that the species for which response coefficients are not listed are assumed to be spectroscopically ``invisible'' in the given datafile (zero response coefficient).
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Petr Kuzmic | Jul 12 2005