The calculation of parameters of the Moffitt equation for rotatory dispersion data.
The least squares calculation of the best values of the parameters of the Moffitt equation and of the Drude equation is examined. It is proved that the least squares evaluation of all three parameters of the Moffitt equation becomes indeterminate as the b(o) term approaches zero. Estimates of low helical content based on the Moffitt relationship are therefore also indeterminate and of dubious value. Both the size of b(o) and the range of wavelengths chosen affect the standard deviations of the parameters. The magnitude of the effects is illustrated by selected examples. The computer program OPTROT is available for evaluating the extent to which data may be correlated by the equations.
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Department of Chemistry and the Institute of Molecular Biophysics, Florida State University, Tallahassee, USA.