Table 1.

Summary of DPH fluorescence dynamics in mitochondrial membranes before and after treatment with formaldehyde.

	Florescence Lifetime, <τ>	Average Rotational correlation time, <φ>	Order parameter, S
Control, 30°C, pH 6.0	11.2 ± 0.4 ns	2.67 ± 0.2 ns	0.623 ± 0.005
+ 3.7 % Formaldehyde	11.1 ± 0.4	2.92 ± 0.23	0.626 ± 0.01

Parameters obtained from time-resolved fluorescence measurements of DPH in mitochondrial membranes demonstrate that both acyl chain and head group packing are highly ordered in these membranes. The long fluorescence lifetime shows that these membranes are relatively well sealed with respect to water penetration. The high value of the order parameter, S, and long rotational correlation time show that DPH is highly ordered and rotates relatively slowly in the hydrophobic core of the membrane. The values of all 3 parameters are consistent with a membrane with high protein content. Addition of 3.7% formaldehyde at pH 6.0, 30°C, caused no significant changes in the measured properties of the DPH fluorescence dynamics, suggesting that this treatment has no effect on acyl chain or phospholipid headgroup packing. Values are mean ± SD.