Magnetically Levitated Plasma Proteins

Surprisingly,
the densities of proteins in solution, which are
important fundamental biophysical quantities, have not been accurately
measured. The lack of such data can limit meaningful interpretation
of physical and chemical features of proteins and enzymes. Here, we
demonstrate a new technique using superparamagnetic iron oxide nanoparticles
(SPIONs) for magnetic levitation (MagLev), which promises to more
precisely measure the density of proteins in solution. As a test of
our new technique, we have levitated human plasma proteins using MagLev.
By using standard density glass beads for calibration, MagLev showed
that the levitated plasma proteins have a measured density in solution
of 1.03 ± 0.02 g/cm3, which is much lower than those
reported or assumed in the past literature (i.e., ∼1.35 g/cm3). Our findings suggest that MagLev may provide useful insights
into the measurement of densities for better understanding the solution
properties of proteins and their interactions both with other proteins
in solution and with solvating water molecules.

令人意外的是，溶液中蛋白质的密度作为重要的基础生物物理参数，尚未得到精准测定。此类数据的缺失，会限制对蛋白质与酶的理化特性进行有意义的阐释。本研究提出一种利用超顺磁性氧化铁纳米颗粒（superparamagnetic iron oxide nanoparticles, SPIONs）构建磁悬浮（MagLev）体系的新技术，有望实现溶液中蛋白质密度的精准测定。为验证该新技术的可行性，我们利用MagLev体系实现了人血浆蛋白质的磁悬浮。通过标准密度玻璃微珠进行校准，MagLev体系测得悬浮血浆蛋白的溶液密度为1.03 ± 0.02 g/cm³，远低于既往文献中报道或假定的数值（约1.35 g/cm³）。本研究结果表明，MagLev技术可为蛋白质密度测定提供有价值的研究思路，有助于更深入地理解蛋白质的溶液特性，以及蛋白质与溶液中其他蛋白质、溶剂化水分子之间的相互作用。