Table 3.

Evaluation of goodness-of-fit

	Model
	1	2a	2b	2c	3	4
No. of fitted mass isotopomers	444	384	360	384	324	318
No. of estimated fluxes*	9	9	9	9	9	9
No. of dilution parameters	72	60	72	72	60	59
No. of redundant measurements†	363	315	279	303	255	250
Sum of squared residuals (SSR)	2061	1163	1262	1332	435	197
Fumarate SSR	889	−	881	891	−	−
Sum of citrate SSR	806	791	27	73	63	45
Threshold value for SSR‡	421	368	330	356	303	298
Fit statistically acceptable§	No	No	No	No	No	Yes
Measurements omitted	None	Fum	Cit	CitOAC	Fum & CitOAC	Fum & CitOAC & AKG(1/12)

The complete and reduced data sets were fitted to the metabolic network model in Fig. 1. The fits were statistically evaluated for goodness-of-fit.

^*Number of estimated fluxes equals the number of independent fluxes that were statistically different from zero, as judged by 95% confidence interval. †Number of redundant measurements = (no. of fitted isotopomers) − (no. of estimated flux) − (no. of G-value parameters). ‡Threshold value for the χ²-statistical test of model adequacy at 95% confidence level. §Fit is statistically acceptable if SSR is less than the threshold value for SSR.