[12]. On the other hand, preferential interaction between cholesterol and
sphingomyelin was investigated in living CHO cells using environment sensitive
fluorescence dye, laurdan. Effect of cholesterol on biomembranes is lowering
membrane fluidity, which is used for detecting preferential interaction between
cholesterol and sphingomyelin. When sphingomyelin molecules in CHO cells
were converted to ceramide by sphingomyelinase treatment, G.P. value of laurdan
in the cell membranes decreased by successive treatment by β-cyclodextrin. The
result suggests that cholesterol molecules removed from cell membranes by
β-cyclodextrin because of no specific interaction between cholesterol and ceramide.
And The lowering G.P. value was observed in concentration dependent fashion of
β-cyclodextrin shown in Fig. 6.2 [13]. The preferential interaction between cholesterol and sphingomyelin was observed in giant liposome of artificial membrane
system under G.P. imaging microscopic instrument. Disappearance of micro domain
of liquid-ordered phase was observed in this experiment, which also suggested
strong interaction between cholesterol and sphingomyelin [14]. Mechanism of
gathering specific protein related to signaling into raft is still unclear, and possibility
of matching between hydrophobic regions of lipid membrane and membrane protein
is examined as a candidate of the gathering mechanism [15].
6.4 Conversion of Membrane Lipid with Receiving
Stimulus and Functions of a Cell
A lot of number of cells composing multi-cellular organism are concerted by both
neural and hormonal control systems to integrate individual living organism. Control
factors such as neurotransmitter and hormone are bound by receptor on cell surface,
Sphingomyelinase [U/ml]
0
0.02
0.04
0.06
0.08
1.0
1.2
1.4
G.P.value
0.14
0.18
0.22
0.26
0.30
Fig. 6.2 Change of G.P. value by conversion of sphingomyelin to ceramide by sphingomyelinase
in living CHO cells
Decrease of G,P, value was observed in sequential treatment of living CHO cells. The cells were
treated with 1 mM β-cyclodextrin for 30 min at 37
C after treatment of various concentrations of
sphingomyelinase for 10 min at 37
C. Decrease of G.P. value in sphingomyelinase concentration
dependent manner, which supposed to increase membrane fluidity because of removal of cholesterol from the cell membrane
84
6 Physical Properties of Biomembranes and Cellular Functions
sphingomyelin was investigated in living CHO cells using environment sensitive
fluorescence dye, laurdan. Effect of cholesterol on biomembranes is lowering
membrane fluidity, which is used for detecting preferential interaction between
cholesterol and sphingomyelin. When sphingomyelin molecules in CHO cells
were converted to ceramide by sphingomyelinase treatment, G.P. value of laurdan
in the cell membranes decreased by successive treatment by β-cyclodextrin. The
result suggests that cholesterol molecules removed from cell membranes by
β-cyclodextrin because of no specific interaction between cholesterol and ceramide.
And The lowering G.P. value was observed in concentration dependent fashion of
β-cyclodextrin shown in Fig. 6.2 [13]. The preferential interaction between cholesterol and sphingomyelin was observed in giant liposome of artificial membrane
system under G.P. imaging microscopic instrument. Disappearance of micro domain
of liquid-ordered phase was observed in this experiment, which also suggested
strong interaction between cholesterol and sphingomyelin [14]. Mechanism of
gathering specific protein related to signaling into raft is still unclear, and possibility
of matching between hydrophobic regions of lipid membrane and membrane protein
is examined as a candidate of the gathering mechanism [15].
6.4 Conversion of Membrane Lipid with Receiving
Stimulus and Functions of a Cell
A lot of number of cells composing multi-cellular organism are concerted by both
neural and hormonal control systems to integrate individual living organism. Control
factors such as neurotransmitter and hormone are bound by receptor on cell surface,
Sphingomyelinase [U/ml]
0
0.02
0.04
0.06
0.08
1.0
1.2
1.4
G.P.value
0.14
0.18
0.22
0.26
0.30
Fig. 6.2 Change of G.P. value by conversion of sphingomyelin to ceramide by sphingomyelinase
in living CHO cells
Decrease of G,P, value was observed in sequential treatment of living CHO cells. The cells were
treated with 1 mM β-cyclodextrin for 30 min at 37
C after treatment of various concentrations of
sphingomyelinase for 10 min at 37
C. Decrease of G.P. value in sphingomyelinase concentration
dependent manner, which supposed to increase membrane fluidity because of removal of cholesterol from the cell membrane
84
6 Physical Properties of Biomembranes and Cellular Functions