Radiation & Photochemistry Division, Bhabha Atomic Research Centre Trombay, Mumbai, 400 085, India.
Amity Institute of Biotechnology, Amity University, Mumbai-Pune Expressway, Bhatan Panvel, Mumbai, 410206, India.
Chemphyschem. 2023 Feb 14;24(4):e202200421. doi: 10.1002/cphc.202200421. Epub 2022 Nov 28.
Sulfated cyclodextrins have recently emerged as potential candidates for producing host-induced guest aggregation with properties better than p-sulfonatocalixarenes that have previously shown numerous applications involving the phenomena of host-induced guest aggregation. In the class of sulfated cyclodextrins (SCD), sulfated β-cyclodextrin (β-SCD) remains the most extensively investigated host molecule. Although it is assumed that the host-induced guest aggregation is predominantly an outcome of interaction of the guest molecule with the charges on the exterior of SCD cavity, it has not been deciphered whether the variation in the cavity size will make a difference in the efficiency of host-induced guest-aggregation process. In this investigation, we present a systematic study of host-induced guest aggregation of a cationic molecular rotor dye, Thioflavin T (ThT) with three different sulfated cyclodextrin molecules, α-SCD, β-SCD and γ-SCD, which differ in their cavity size, using steady-state emission, ground-state absorption and time-resolved emission measurements. The obtained photophysical properties of ThT, upon interaction with different SCD molecules, indicate that the binding strength of ThT with different SCD molecules correlate with the cavity size of the host molecule, giving rise to the strongest complexation of ThT with the largest host molecule (γ-SCD). The binding affinity of ThT towards different host molecules has been supported by molecular docking calculations. The results obtained are further supported with the temperature and ionic strength dependent studies performed on the host-guest complex. Our results indicate that for host-induced guest aggregation, involving oppositely charged molecules, the size of the cavity also plays a crucial role beside the charge density on the exterior of host cavity.
硫酸化环糊精最近成为产生主体诱导客体聚集的潜在候选物，其性质优于先前表现出涉及主体诱导客体聚集现象的众多应用的对磺基杯[4]芳烃。在硫酸化环糊精（SCD）类中，硫酸化β-环糊精（β-SCD）仍然是研究最广泛的主体分子。尽管假定主体诱导客体聚集主要是客体分子与 SCD 腔体外表面电荷相互作用的结果，但尚未确定腔室尺寸的变化是否会对主体诱导客体聚集过程的效率产生影响。在这项研究中，我们使用稳态发射、基态吸收和时间分辨发射测量对阳离子分子转子染料硫代黄素 T（ThT）与三种不同的硫酸化环糊精分子（α-SCD、β-SCD 和 γ-SCD）的主体诱导客体聚集进行了系统研究，它们在空腔尺寸上有所不同。与不同 SCD 分子相互作用后获得的 ThT 光物理性质表明，ThT 与不同 SCD 分子的结合强度与主体分子的空腔尺寸相关，导致 ThT 与最大主体分子（γ-SCD）的最强络合。分子对接计算支持了 ThT 对不同主体分子的结合亲和力。通过对主体-客体配合物进行的温度和离子强度依赖性研究进一步支持了这些结果。我们的结果表明，对于涉及带相反电荷的分子的主体诱导客体聚集，除了主体腔体外表面的电荷密度外，腔室尺寸也起着至关重要的作用。
