Discipline of Chemistry, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 453552, M.P., India.
Discipline of Chemistry, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 453552, M.P., India.
J Colloid Interface Sci. 2016 Sep 15;478:29-35. doi: 10.1016/j.jcis.2016.05.055. Epub 2016 May 28.
Exploring and understanding the fundamental interaction between protein and surfactant is utmost important for various pharmaceutical and biomedical applications. However, very less is known about the arrangement of individual negatively charged sodium dodecyl sulfate (SDS) molecules on the human serum albumin (HSA). Here, we have investigated the morphology and mechanistic insights of complexation between HSA and SDS by means of photoluminescence (PL) spectroscopy, circular dichroism (CD) and PL microscopy using amine-functionalized silicon quantum dot (Si QD) as an external luminescent marker. The present study is based on a unique and dynamic SDS-Si QD system. The synthesized allylamine-functionalized Si QDs show a distinct PL band centered at 455nm upon excitation at 375nm. At neutral pH, these Si QDs form ordered aggregates in the presence of 1mM SDS due to the hydrogen bonding interaction with the sulfate head groups of surfactants, which is manifested in the appearance of a large Stokes shifted luminescence band centered at 610nm. It has been observed that the PL intensity of SDS-Si QD aggregates at 610nm decreases gradually with concomitant increase in the PL intensity of monomeric Si QDs at 455nm upon increasing the concentration of HSA from 1 to 10μM. These observations combined with PL lifetime, PL microscopy and CD results reveal that SDS forms micelle-like aggregates on the partially unfolded HSA mainly via electrostatic interaction between negatively charged sulfate head groups and positively charged residues of partially unfolded HSA. For the present HSA-SDS system, our results fit a model with type I "necklace and bead"-like structures, where micelle-like SDS aggregates wrap around by the partially unfolded HSA backbone.
探索和理解蛋白质与表面活性剂之间的基本相互作用对于各种药物和生物医学应用至关重要。然而，人们对单个带负电荷的十二烷基硫酸钠（SDS）分子在人血清白蛋白（HSA）上的排列知之甚少。在这里，我们通过荧光光谱法、圆二色性（CD）和使用胺功能化硅量子点（Si QD）作为外部发光标记的荧光显微镜研究了 HSA 与 SDS 之间的络合形态和机制见解。本研究基于独特且动态的 SDS-Si QD 系统。合成的烯丙胺功能化 Si QD 在 375nm 激发时显示出独特的 455nm 处的 PL 带。在中性 pH 下，由于与表面活性剂的硫酸根基团的氢键相互作用，这些 Si QD 在存在 1mM SDS 时会形成有序的聚集体，这表现在 610nm 处出现大斯托克斯位移发光带。已经观察到，随着 HSA 浓度从 1 增加到 10μM，610nm 处的 SDS-Si QD 聚集体的 PL 强度逐渐降低，同时 455nm 处单体 Si QD 的 PL 强度增加。这些观察结果与 PL 寿命、PL 显微镜和 CD 结果相结合，表明 SDS 通过带负电荷的硫酸根基团与部分展开的 HSA 上的带正电荷的残基之间的静电相互作用在部分展开的 HSA 上形成胶束样聚集体。对于目前的 HSA-SDS 系统，我们的结果符合具有 I 型“项链和珠子”样结构的模型，其中胶束样 SDS 聚集体围绕部分展开的 HSA 骨架包裹。
