PDF(Pubmed)
Abstract：
This work is the first one that provides not only evidence for the existence of free volumes in the human stratum corneum but also focuses on comparing these experimental data, obtained through the unique positron annihilation lifetime spectroscopy (PALS) method, with theoretical values published in earlier works. The mean free volume of 0.269 nm was slightly lower than the theoretical value of 0.4 nm. The lifetime τ3 (1.83 ns with a coefficient of variation CV of 3.21%) is dependent on the size of open sites in the skin. This information was used to calculate the free volume radius R (0.269 nm with CV 2.14%), free volume size Vf (0.081 nm3 with CV 4.69%), and the intensity I3 (9.01% with CV 10.94%) to estimate the relative fractional free volume fv (1.32 a.u. with CV 13.68%) in human skin ex vivo. The relation between the lifetime of o-Ps (τ3) and the radius of free volume (R) was formulated using the Tao-Eldrup model, which assumes spherical voids and applies to sites with radii smaller than 1 nm. The results indicate that PALS is a powerful tool for confirming the existence of free volumes and determining their size. The studies also focused on describing the probable locations of these nanospaces in SC lipid bilayers. According to the theory, these play an essential role in dynamic processes in biological systems, including the diffusion of low-molecular-weight hydrophobic and moderately hydrophilic molecules. The mechanism of their formation has been determined by the molecular dynamics of the lipid chains.
摘要：
这项工作是第一个不仅提供了人类角质层中存在自由体积的证据，而且还着重于比较这些实验数据，通过独特的正电子湮没寿命光谱(PALS)方法获得，与早期作品中发表的理论价值。0.269nm的平均自由体积略低于0.4nm的理论值。寿命τ3（1.83ns，变异系数CV为3.21％）取决于皮肤中开放部位的大小。此信息用于计算自由体积半径R（0.269nm，CV为2.14%），自由体积尺寸Vf（0.081nm3，CV4.69%），和强度I3(9.01%,CV10.94%)来估计离体人皮肤中的相对游离体积分数fv(1.32a.u.,CV13.68%)。使用Tao-Eldrup模型建立了o-Ps的寿命（τ3）与自由体积半径（R）之间的关系，假定球形空隙，适用于半径小于1nm的位点。结果表明，PALS是确认自由卷的存在和确定其大小的有力工具。研究还集中于描述SC脂质双层中这些纳米空间的可能位置。根据理论,这些在生物系统的动态过程中起着至关重要的作用，包括低分子量疏水分子和中等亲水分子的扩散。它们的形成机制已由脂质链的分子动力学决定。
