The interactions of human serum albumin (HSA) with four cationic gemini surfactants and four single-chain surfactants have been investigated from the measurements of fluorescence spectroscopy, dynamic lights scattering (DLS), zeta potential, and circular dichroism (CD). The fluorescence results show the binding strength of surfactants to HSA, along with the blue shift under the maximum emission wavelength ( λ max ) which is sensitive to the protein conformations. It has been found that the hydrodynamic diameters of the protein aggregates are enlarged and the electrokinetic potentials of them get positive with increasing the concentration of the surfactants. The conformational transformation of the secondary structures of surfactant–HSA aggregates has been confirmed through the quantitative analysis of the CD spectra. The isothermal titration microcalorimetry (ITC) has been employed to further analyze the binding process of single-chain surfactants to HSA. The comprehensive results obtained from various approaches have shown that both hydrophobic and electrostatic interactions are present in the cationic surfactant–HSA systems. Compared with the corresponding single-chain surfactants, the gemini ones have much stronger binding ability to induce the unfolding of HSA. These investigations on the interactions between HSA and surfactants with the altered chain architecture in different concentration regimes can facilitate the application of surfactant-protein systems in pharmaceutical, biotechnology and related fields.
In the propagating process along metal surface, surface plasmon polaritons (SPPs) mainly decay into thermal loss or release into photons, while a part of them were converted into electrons with high energy termed as hot electrons, which have great significance in photonics and electronics. In this work, the generation of plasmonic hot electrons was ascertained in the nanoparticle-film system through plasmon-driven surface catalysis (PDSC) reactions. The surface-enhanced Raman scattering (SERS) spectra of p,p'-dimercaptoazobenzene (DMAB) catalyzed by 4-nitrobenzenethiol (4NBT) experimentally demonstrated the essential catalysis electrons were generated in this hybrid plasmon mode. The results pointed out the priority of plasmonic hot electron generation in the dimer-film gap compared to the monomer-film gap which was analyzed by the surface electric and charge distribution. Furthermore, the SERS spectra of 4NBT in the metal nanoparticle-dielectric film system confirmed the necessity of hybrid plasmon mode in the generation of plasmonic hot electrons in the nanoparticle-film system. Because of the simple configuration and convenient fabrication of nanoparticle-film system, the work on this hybrid plasmon mode has a significant role in promoting the application of plasmonic hot electrons.
危险品化学品经营许可证（带存储）