| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2002: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 2001: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Research Abstract |
(1) The state of super-cooled water in the water layer of multilamellar L- α , distearoyl phosphatidylcholine (DSPC) containing 11wt% water remains unchanged even down to -190℃. Experimental results of differential scanning calorimeter(DSC), x-ray diffraction and Raman scattering prove that the super-cooled water in the water layer does not freeze even down to -190℃. Water layer is roughly divided into at least two regions : One region (tightly bound water layer) is precisely affected by the inner surface conditions such as hydrophilic interaction between the head group of DSPC and the water molecule, and the other region (loosely bound water layer) is bulk-like free water or is affected by relatively weak interactions correlated with distance from the surface. In the case of multilamellar phospholipid, the thickness of the water layer is estimated as 12〜30A equivalent to 4〜10 mono-layer thickness of water, however, multilamellar DSPC with 11wt% water contents is composed of only "tigh
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tly bound water layer" that is adsorbed on the surface of the polar head groups. This water region has a strong interaction with polar segments containing N^+ and O_-, and it modified their H-bonded network structure. The tightly bound water is considered to be nonfreezing water, because the attractive energy between bound water and hydrophilic head groups is greater than the ice nucleation energy.
(2) Although the water layer of multilamellar L- α, dilauroyl (C_n = 12 : DLPC_<12>) phosphatidylcholine with water contents less than 10wt% is freezing during temperature decreasing down to - 140℃, the effect of hydrocarbon's length is relatively easy to remain the super-cooled water in the water layer in the case of multilamellar L - α , dilignoceroyl (C_n = 24 : DLPC_<24>) phosphatidylcholine. DSC thermal data are indicated that the state of super-cooled water or crystallization in water layer depends on the length of hydrocarbon chain in phospholipids.
(3) Experimental results of Raman scattering show that a slight conformational change of multilamellar DSPC occurs at about - 130 ℃ on decreasing temperature process independently of whether the water layer is freezing or not. Less
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