Summing up dynamics: modelling biological processes in variable temperature scenarios

The interest of modelling biological processes with dynamically changing ex ternal conditions (temperature, relative humidity, gas conditions) increase s. Several modelling approaches are currently available. Among them are app roaches like modelling under standard conditions, temperature sum models an d dynamic modelling. While the first two approaches require huge simplifica tions that endanger the applicability of the results, the latter requires a substantial modelling and computational effort. In this paper the often ve ry successful method of temperature sum is improved and enhanced to reflect fundamental insights in biochemical processes. Knowing that reaction rates depend on temperature according to Arrhenius' law, a rate sum calculation for each active process is proposed. While the temperature sum approach is in practice restricted to polynomial models, the rate sum approach allows t he building and application of more fundamental and process-oriented models . The method is computationally feasible. Model calculations on simulated d ata show that this approach is at least equivalent to existing approaches, and often outperforms them in terms of statistical fit (R-adj(2) of over 90 %, and often 99.5%). Moreover, it has the major advantage of estimating par ameters that have an interpretation in the biochemical reality. Another maj or advantage is that all the normal rules, techniques and procedures of sta tistics remain applicable. (C) 2000 Elsevier Science Ltd. All rights reserv ed.