Yano J, Sato K, Kaneko F, Small D M, Kodali D R
Faculty of Applied Biological Science, Hiroshima University, Higashi-Hiroshima, 739-8528 Japan.
J Lipid Res. 1999 Jan;40(1):140-51.
Polymorphic transformations in two saturated-unsaturated mixed acid triacylglycerols, SOS (sn -1,3-distearoyl-2-oleoylglycerol) and OSO (sn -1,3-dioleoyl-2-stearoylglycerol), have been studied by FT-IR spectroscopy using deuterated specimens in which stearoyl chains are fully deuterated. A reversible phase transition between sub alpha and alpha and a series of irreversible transitions (alpha-->gamma-->beta'-->beta (beta2, beta1) for SOS and alpha-->beta'-->beta for OSO) were studied with an emphasis on the conformational ordering process of stearoyl and oleoyl chains. The alpha-->sub alpha reversible transition was due to the orientational change of stearoyl chains in the lateral directions from the hexagonal subcell to a perpendicularly packed one. As the first stage of the series of irreversible transitions from alpha to beta, the conformational ordering of saturated chains took place in the alpha-->gamma transition of SOS and in the alpha-->beta' transition of OSO; one stearoyl chain in SOS and OSO takes the all-trans conformation and the second stearoyl chain in SOS takes the bent conformation like those observed in the most stable beta-type. As the final stage, the ordering of unsaturated chains occurred in the beta'-->beta transition both for SOS and OSO. A conversion in the layered structure from bilayer to trilayer was also accompanied by the conformational ordering in the alpha-->gamma transition of SOS and in the beta'-->beta transition of OSO.
利用硬脂酰链完全氘代的氘代样品，通过傅里叶变换红外光谱（FT-IR）研究了两种饱和-不饱和混合酸三酰甘油SOS（sn-1,3-二硬脂酰-2-油酰甘油）和OSO（sn-1,3-二油酰-2-硬脂酰甘油）中的多晶型转变。研究了亚α和α之间的可逆相变以及一系列不可逆转变（SOS为α→γ→β'→β（β2，β1），OSO为α→β'→β），重点关注硬脂酰和油酰链的构象有序化过程。α→亚α可逆转变是由于硬脂酰链在横向方向上从六方亚晶胞到垂直堆积的取向变化。作为从α到β的一系列不可逆转变的第一阶段，饱和链的构象有序化发生在SOS的α→γ转变和OSO的α→β'转变中；SOS和OSO中的一条硬脂酰链呈全反式构象，SOS中的第二条硬脂酰链呈弯曲构象，类似于在最稳定的β型中观察到的构象。作为最后阶段，SOS和OSO在β'→β转变中都发生了不饱和链的有序化。在SOS的α→γ转变和OSO的β'→β转变中，层状结构从双层到三层的转变也伴随着构象有序化。
