Singh S, Gupta J
Division of Biopolymers, Central Drug Research Institute, Lucknow.
Indian J Biochem Biophys. 1993 Jun;30(3):166-71.
Hydrophobic nature of human plasma low density lipoprotein surface has been studied by fluorescence spectroscopic method. Enhancement in 8-anilino-1-naphthalene sulphonate (ANS) fluorescence quantum yield from 0.004 to 0.114 at 470 nm has suggested that the ANS binding sites are fairly low in polarity. LDL has been found to have 77 homogeneous binding sites for ANS (Ka = 2.5 x 10(5) M-1). The binding of an ANS molecule does not affect the successive binding sites. Variation in temperature from 15 degrees to 45 degrees C did neither alter the number of binding sites nor association constant. Quenching of protein fluorescence (lambda exc 286 nm, lambda ems 336 nm) indicated the occurrence of energy transfer in LDL-ANS complex arising from conformational changes capable of bringing charge acceptor segments near to other ANS site. About 30-fold increase in ANS quantum yield and large shift in the emission maximum are characteristic features of large hydrophobic environment on the surface of LDL particle.
采用荧光光谱法研究了人血浆低密度脂蛋白表面的疏水性。8-苯胺基-1-萘磺酸（ANS）在470nm处的荧光量子产率从0.004提高到0.114，这表明ANS结合位点的极性相当低。已发现低密度脂蛋白对ANS有77个均匀的结合位点（Ka = 2.5×10⁵ M⁻¹）。一个ANS分子的结合不会影响后续的结合位点。温度从15℃变化到45℃既不会改变结合位点的数量，也不会改变缔合常数。蛋白质荧光猝灭（激发波长286nm，发射波长336nm）表明，在LDL-ANS复合物中发生了能量转移，这是由构象变化引起的，这种变化能够使电荷受体片段靠近其他ANS位点。ANS量子产率增加约30倍以及发射最大值发生较大位移是LDL颗粒表面存在大疏水环境的特征。
