TABLE 1.
List of parameters (Cmax, Keq, koff, and kon) in the Langmuir adsorption model, membrane permeability values of alcohols P, and ratio of membrane area change to surface density constant q
| Methanol | Ethanol | Propanol | Butanol | |
|---|---|---|---|---|
| Cmax (molecules/Å2) | 0.15 ± 0.01 | 0.07 ± 0.01 | 0.06 ± 0.01 | 0.05 ± 0.01 |
| Keq (1/M) | 0.04 ± 0.01 | 0.21 ± 0.01 | 0.90 ± 0.07 | 2.64 ± 0.26 |
| koff (1/s) | 300 ± 100 | 400 ± 400 | 800 ± 400 | >1000 |
| kon (1/(M × s)) | 10 ± 5 | 80 ± 80 | 700 ± 360 | >2600 |
| qestimate (Å2/molecules) | 5.3 ± 0.8 | 4.6 ± 0.7 | 6.3 ± 0.9 | 6.5 |
| qfit (Å2/molecules) | 5.3 ± 0.6 | 3.0 ± 1.3 | 3.4 ± 0.8 | 4.1 ± 1.1 |
| P (cm/s) | 1.2 ± 0.4 × 10−5 | 3.8 ± 3.0 × 10−5 | 2.8 ± 1.4 × 10−4 | 1.2 ± 1.4 × 10−3 |
Values for koff, qfit, and P are averages based on six vesicles or more for vesicles in 4.94 M methanol, 1.70 M ethanol, 2.56 M ethanol, 0.19 M propanol, 0.39 M propanol, and 0.11 M butanol aqueous mixtures. The value qestimate was determined from the slopes in the studied concentration range from Fig. 15. The qfit and P-values for ethanol at 1.70 M and 2.56 M and propanol at 0.19 M and 0.39 M showed no concentration dependence so averages of these values are presented here. For butanol, the model predictions of area expansion (ΔA/Ao)mod with koff values between 103 and 105 were indistinguishable within the experimental error of measured membrane expansion (ΔA/Ao)exp-dir (due to image resolution limitation) so a minimum value of >1000 is reported. The value kon was computed simply from the relation Keq = kon/koff.