Molecular weight determination of lipoprotein(a) [Lp(a)] in solutions containing either NaBr or D2O: relevance to the number of apolipoprotein(a) subunits in Lp(a).
Molecular weight determination of lipoprotein(a) [Lp(a)] in solutions containing either NaBr or D2O: relevance to the number of apolipoprotein(a) subunits in Lp(a).
复制标题
含有 NaBr 或 D2O 的溶液中脂蛋白 (a) [Lp(a)] 的分子量测定：与 Lp(a) 中载脂蛋白 (a) 亚基数量的相关性。
DOI：
10.1021/bi961941k
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Santiago,JY
中科院分区：
文献类型：
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作者：
Fless,GM;Santiago,JY
低密度脂蛋白（LDL）的分子量测定通常在含有高浓度盐（高达13.4 M NaBr）的溶液中通过沉降速度和扩散实验进行，因为它不会优先结合盐或水。考虑到脂蛋白（a）[Lp（a）]在结构上与LDL相似，不同之处仅在于存在Apo（a），因此还在含有高浓度NaBr的溶液中测量了Lp（a）的分子量M。我们通过比较在含NaBr的三组分体系中通过沉降和浮选平衡测定的Lp（a）的表观分子量Mapp和分体积ε ′与在含D2 O的双组分体系中测定的类似参数M和分比容ν ε ′，对这种做法的适用性提出了质疑。LDL作为对照。与以前用不同方法得到的结果一致，我们的结果表明四种不同LDL样品的M和ν ε无显著差异，显然溶剂组分没有明显的优先结合。与此相反，在NaBr中测得的Lp（a）的Map和Δ ′值显著大于M和ν ′。溶剂组分的优先结合似乎是Apo（a）质量或Kringle IV结构域数量的函数，如两组参数之间的百分比差异增加所表示的，具有15−27个Kringle IV结构域的Apo（a）的Lp（a）物质的M范围为4 - 13%，ν范围为0.2 - 0.5%。此外，我们的研究结果表明，可变的Apo（a）kringle IV结构域比Apo（a）的恒定结构域更多地参与这一过程。这些结果表明，Lp（a）分子量应在D2 O中测定，应避免使用高浓度的NaBr，因为它们的使用会导致高估分子量和部分比容。将该方法应用于Lp（a）还原后释放多少Apo（a）的问题导致Lp（a）仅含有一个Apo（a）分子的结论。
Molecular weight determination of low-density lipoprotein (LDL) is usually performed in solutions containing high concentrations of salt (up to 13.4 M NaBr) by sedimentation velocity and diffusion experiments, because it does not preferentially bind salt or water. Considering that lipoprotein(a) [Lp(a)] is structurally similar to LDL, differing only by the presence of Apo(a), the molecular weight,M, of Lp(a) has also been measured in solutions containing high concentrations of NaBr. We questioned the suitability of this practice by comparing the apparent molecular weight,Mapp, and partial volume,ϕ‘, of Lp(a) determined by sedimentation and flotation equilibrium in a three-component system containing NaBr with the analogous parameters,Mand partial specific volume, ν̄, determined in a two-component system containing D2O. LDL served as a control. In agreement with previous findings obtained with different methods, our results indicate no significant differences inMand ν̄ of four different LDL samples and apparently no significant preferential binding of solvent components. In contrast, values ofMappandϕ‘ of Lp(a) evaluated in NaBr are significantly greater thanMand ν̄. Preferential binding of solvent components appeared to be a function of Apo(a) mass or the number of kringle IV domains, as expressed by increasing percentage differences between the two sets of parameters, ranging from 4 to 13% inMand 0.2 to 0.5% in ν̄ of Lp(a) species having Apo(a) with 15−27 kringle IV domains. Furthermore, our results indicate that the variable Apo(a) kringle IV domains are more involved in this process than the constant domain of Apo(a). These findings indicate that the Lp(a) molecular weight should be determined in D2O and that high concentrations of NaBr should be avoided as their use would lead to overestimated molecular weights and partial specific volumes. Application of this method to the question of how much Apo(a) is released upon the reduction of Lp(a) led to the conclusion that Lp(a) contains only one Apo(a) molecule.