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. 2003 May 1;5:108–115. doi: 10.1251/bpo52

Table 3.

Kinetic parameters for the plasma membrane H+-ATPase in the presence of glycerol, trehalose or sucrose

Polyol Concentration (M) Mass Fraction (c) Viscosity (cP) Vmax
μmols ATP mg-1 min-1 		S0.5
mM
Trehalose 0.0
0.2
0.4
0.5
0.6
0.8		 0.00
0.07
0.13
0.16
0.19
0.25		 1.03
1.39
1.58
1.78
2.08
2.41		 6.91
5.80
5.59
5.22
4.49
3.73		 1.08
1.21
1.29
1.38
1.87
2.29
Sucrose 0.0
0.2
0.4
0.5
0.6
0.8		 0.00
0.07
0.13
0.17
0.20
0.25		 1.03
1.24
1.53
1.74
2.02
2.56		 6.91
6.26
5.62
5.25
4.83
4.17		 1.08
1.10
1.16
1.37
1.57
1.95
Glycerol 0.0
1.0
2.0
3.0
3.5
4.0		 0.00
0.09
0.18
0.27
0.31
0.35		 1.03
1.31
1.71
2.26
2.58
3.05		 6.91
6.24
4.65
4.05
2.88
1.94		 1.08
1.16
1.18
1.27
1.78
2.23

Solutions viscosities were calculated as described in equation [eq 1] by using the measured time of ball descent and solution density at 20ºC. Initial rates of ATP hydrolysis were measured at 20ºC as described in methods in the presence of the indicated concentrations of, trehalose, sucrose or glycerol. Mass fraction (c) was obtained by calculating the grams of solute in the total grams of the mixture in 1 ml. The kinetic parameters (V max, S0.5 and n) were obtained by non-linear regression, fitting the data to the Hill equation [eq 2]. The Hill coefficient (n= 1.7) was not modified by viscosity and thus it is not included in the table. Standard deviations were always less than 5% of the reported values.