In an ideal world one retains as many independent variables as may be relevant to the behaviour one is seeking to explain, but in practice that advice may be difficult to follow.For example, in studying an enzyme with activity dependent on Mg ATP and the p H in such a way that the concentrations of all relevant ions and molecules vary independently, so that effects due to the different ones can be separated.
They are often violated in published work, however, so apparently they are not perceived as obvious.
The essential point is that an experiment should be capable of supplying the information that the experimenter is seeking to extract.
For example, the method of for assessing whether two competing substrates bind at the same site involves linear combinations of the two substrate concentrations.
In these sorts of experiments one is deliberately suppressing differences between the effects of the two variables in order to shine more light on some effect of the two together, and as long as this is understood there is no objection to the use of linear combinations of concentrations.
Analysis of enzyme kinetic data to obtain valid information requires attention to two details that are often given less attention than they need.
The first is an experimental design that ensures that the variables treated as independent are truly independent, that different interpretations can be distinguished, and that parameter values can be estimated.It is much easier, however, to follow a design in which the total Mg Cl examined four designs for varying the concentrations of glutathione and methylgloxal for distinguishing between models for glyoxalase I.He showed that maintaining one or other constant, or varying them in constant relation to one another, showed poor discriminatory power, but varying them independently was very powerful.The necessary design, therefore, must depend on the context in which the experiment is being used.If the aim is to obtain kinetic parameters to be used for elucidating an enzyme mechanism, the conditions need to be varied in ranges in which the results vary with the parameter of interest.Instead I shall concentrate on three aspects closer to the aims of STRENDA.