Equilibrium constant expression approximation method calculations with

Various physical considerations can be used for preliminary estimation of mathematic expressions and parameter values (rather simplified considerations were used in O Eqs. 9.2-9.S). It is important to emphasize that neither dependences nor values of parameters can be derived (directly calculated) from imiversal principles or measured by any experimental method. The stretch and bend constants (of O Eqs. 9.2 and O 9.3) can be evaluated using infra-red spectra equilibrium bond lengths and valence angles can be estimated from X-ray data for simple molecules. The Aij coefficients of the attraction part of van der Waals interactions can be evaluated (and really were calculated and used without refinement in the first MM works) via approximate formulae for dispersion interactions however, their exact values for the certain dass of the systems should be adjusted by comparison with experimental data... 

For most SPR appHcations the dissociation constant is calculated from the Kd = koff/kon proportion. It can also be evaluated from the steady-state phase (equilibrium). This method, however, is apphcable only for kinetically fast interactions. The time required for reaching the equihbrium at a protein concentration equal to JCj can be expressed as l/ko . For an interaction with off =1x10 s it will take approximately 1 h to reach equilibrium. The steady state is reached faster with increased protein concentrations. Using a high protein concentration results, however, in the collection of only a narrow range of Req points, close to saturation (Rmax)- In this situation the Kj is... 

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