我们已经研究了在存在淀粉样β肽Aβ(25-35)的情况下,各种浓度的钙离子(Ca2)对脂质囊泡结构的影响。特别是,我们已经研究了钙离子对Aβ(25-35)触发的膜崩解引起的最近记录的二节样结构(BLS)形成的影响。首先,我们通过使用小角度X射线和中子散射表明,肽分子使凝胶相DPPC单层囊泡(ULVs)的脂质双层硬化,而向系统中添加钙离子会阻碍Aβ的这种作用(25-35)。其次,Aβ(25-35)显示了临界肽浓度,在该浓度下BLS由于加热和冷却样品通过脂质主要相变温度(Tm)而从ULV重组。然而,钙离子的添加不会显着影响Aβ诱导的BLS的形成及其结构参数,虽然肽的二级结构发生了变化,例如增加的α-螺旋分数,已通过圆二色性光谱法记录。最后,根据31P核磁共振(NMR)测量,钙离子不影响BLS中的脂质-肽排列及其在NMR光谱仪磁场中对齐的能力。各种浓度的钙离子对脂质-肽相互作用的影响可能在生物学上很重要,因为它们的局部浓度在体内条件下变化很大。在目前的工作中,研究了钙离子作为调节脂质-肽相互作用的可能工具,该工具证明了Aβ(25-35)对脂质膜的破坏作用。
We have studied the effect of calcium ions (Ca2+) at various concentrations on the structure of lipid vesicles in the presence of amyloid-beta peptide Aβ(25-35). In particular, we have investigated the influence of calcium ions on the formation of recently documented bicelle-like structures (BLSs) emerged as a result of Aβ(25-35) triggered membrane disintegration. First, we have shown by using small-angle X-ray and neutron scattering that peptide molecules rigidify the lipid bilayer of gel phase DPPC unilamellar vesicles (ULVs), while addition of the calcium ions to the system hinders this effect of Aβ(25-35). Secondly, the Aβ(25-35) demonstrates a critical peptide concentration at which the BLSs reorganize from ULVs due to heating and cooling the samples through the lipid main phase transition temperature (Tm). However, addition of calcium ions does not affect noticeably the Aβ-induced formation of BLSs and their structural parameters, though the changes in peptide\'s secondary structure, e.g. the increased α-helix fraction, has been registered by circular dichroism spectroscopy. Finally, according to 31P nuclear magnetic resonance (NMR) measurements, calcium ions do not affect the lipid-peptide arrangement in BLSs and their ability to align in the magnetic field of NMR spectrometer. The influences of various concentrations of calcium ions on the lipid-peptide interactions may prove biologically important because their local concentrations vary widely in in-vivo conditions. In the present work, calcium ions were investigated as a possible tool aimed at regulating the lipid-peptide interactions that demonstrated the disruptive effect of Aβ(25-35) on lipid membranes.