3.4 Differential Scanning Calorimetry (DSC)
Thermal property is major physical property in biomembrane, and measurement of
thermal property provides useful information of structure and physical property of
samples. Principle of heat-compensation method for DSC is as follows. When
reference and sample are heated by the same electric power, difference of temperature occurs because of difference of specific heat of them. And additional electric
power is supplied to keep the same temperature of them, and the electric power is
measured as excess specific heat (Fig. 3.3). Thermogram of DSC is shown by the
following equation.
C difference ¼ C sample À C refereence ¼ E sample À E reference
À
Á dt
dT ¼ E difference Á
dt
dT , where
dT
dt is rate of temperature increase. When the rate is controlled to be constant, c ifference
is proportional to E difference and measurement of c difference gives c difference Thermal
denaturation of protein is observed by DSC measurement. In case of lipid bilayer,
lipid assembly in aqueous environment shows phase transition by DSC
measurement.
Fracturing
EF surface
PF surface
Ice
Ice
Integral protein
Lipid bilayer
Cytoplasm side
Fig. 3.2 Method of freeze-fractured electron microscopy
Process
1. Specimen(cell, liposome) Freezed at À150
C
2. Fractured at À110
C under high vacuum
3. Depositing platinum in oblique angle to make shadow
4. Reinforcing by deposition of carbon
5. Preparing replica by melting the specimen
6. Observation of the replica by electron microscope
32
3 Methods for Physical Properties of Biomembranes and Cells
Thermal property is major physical property in biomembrane, and measurement of
thermal property provides useful information of structure and physical property of
samples. Principle of heat-compensation method for DSC is as follows. When
reference and sample are heated by the same electric power, difference of temperature occurs because of difference of specific heat of them. And additional electric
power is supplied to keep the same temperature of them, and the electric power is
measured as excess specific heat (Fig. 3.3). Thermogram of DSC is shown by the
following equation.
C difference ¼ C sample À C refereence ¼ E sample À E reference
À
Á dt
dT ¼ E difference Á
dt
dT , where
dT
dt is rate of temperature increase. When the rate is controlled to be constant, c ifference
is proportional to E difference and measurement of c difference gives c difference Thermal
denaturation of protein is observed by DSC measurement. In case of lipid bilayer,
lipid assembly in aqueous environment shows phase transition by DSC
measurement.
Fracturing
EF surface
PF surface
Ice
Ice
Integral protein
Lipid bilayer
Cytoplasm side
Fig. 3.2 Method of freeze-fractured electron microscopy
Process
1. Specimen(cell, liposome) Freezed at À150
C
2. Fractured at À110
C under high vacuum
3. Depositing platinum in oblique angle to make shadow
4. Reinforcing by deposition of carbon
5. Preparing replica by melting the specimen
6. Observation of the replica by electron microscope
32
3 Methods for Physical Properties of Biomembranes and Cells