title: Metrics from nonlinear dynamics adapted for characterizing the behavior of nonequilibrium enzymatic rate functions.
abstract: Several metrics from nonlinear dynamics and statistical mechanics have been characterized on computer-generated number series with various signal-to-noise ratios, demonstrating their individual reliability as a function of sample size and their relationships to each other. The root mean square (RMS) evaluates amplitude, and the power spectral density (PSD) provides a visual display of the frequency spectrum; both measures have very high reliability even for an N as low as 50. The Fractal Dimension (D) is shown to converge rapidly and also to be reliable when N is as low as 50. These three measures (RMS, PSD, and D) have been applied to the complex kinetics of tyrosine hydroxylase time courses (50-point curves) at various BH4 concentrations (near physiological, but far from equilibrium levels). Recently developed measures of spectral entropy and the Liapunov Exponent, -lambda are also characterized.
mesh_terms: D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives / Q000494:pharmacology; D001921:Brain / Q000201:enzymology; D003201:Computers; D004295:Dihydroxyphenylalanine / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D004798:Enzymes / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D051381:Rats; D013223:Statistics as Topic; D014443:Tyrosine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D004798:Enzymes; D001708:Biopterins; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D014446:Tyrosine 3-Monooxygenase; C003402:sapropterin