Bihari-Varga M, Sztatisz J, Gál S
Atherosclerosis. 1981 Apr;39(1):19-23. doi: 10.1016/0021-9150(81)90084-8.
Temperature dependent techniques - differential scanning calorimetry (DSC), polarizing microscopy - were used to study the properties of human serum low density lipoprotein (LDL) and its glycosaminoglycan (GAG) complexes, and to investigate the influence of the addition of high density lipoprotein (HDL) to the complex system. In the LDL molecule a reversible endothermic transition took place with its peak at 33 degrees C. Cholesteryl esters within the LDL core existed as an isotropic solution above this temperature (i.e. around body temperature), and in the form of smectic liquid crystals below it. When LDL was converted in vitro into GAG-LDL complexes by the addition of chondroitin-6-sulfate, dermatan sulfate, heparin or heparan sulfate, the DSC curves showed an evaluation of the transition temperature: the peak values in these samples were found at 40 degrees C and under the polarizing microscope a birefringence developed, typical of smectic liquid crystals. In chondroitin-4-sulfate-LDL complexes no alteration of the physical structure of the LDL molecule could be demonstrated. HDL decreased the transition temperature of GAG-LDL complexes and the disappearance of birefringence indicated that in the presence of HDL the lipids within the GAG-LDL complexes existed in a liquid phase at a temperature in the vicinity of body temperature.
采用温度依赖性技术——差示扫描量热法（DSC）、偏光显微镜——来研究人血清低密度脂蛋白（LDL）及其糖胺聚糖（GAG）复合物的性质，并考察向复合体系中添加高密度脂蛋白（HDL）的影响。在LDL分子中发生了一个可逆的吸热转变，其峰值出现在33℃。LDL核心内的胆固醇酯在该温度以上（即接近体温）以各向同性溶液的形式存在，在该温度以下以近晶型液晶的形式存在。当通过添加硫酸软骨素-6、硫酸皮肤素、肝素或硫酸乙酰肝素在体外将LDL转化为GAG-LDL复合物时，DSC曲线显示转变温度有所升高：这些样品中的峰值出现在40℃，并且在偏光显微镜下出现了近晶型液晶特有的双折射现象。在硫酸软骨素-4-LDL复合物中，未证实LDL分子的物理结构有改变。HDL降低了GAG-LDL复合物的转变温度，双折射现象的消失表明在HDL存在的情况下，GAG-LDL复合物中的脂质在接近体温的温度下以液相形式存在。
