The Binding Properties Of The Plant Active Ingredients With Serum Albumins And The Effects On The Structure Of Proteins

Under simulative physiological conditions (pH7.4), the interaction betweenseveral plant active ingredients and serum albumins and the effects on the proteins’structure were explored by fluorescence, UV vis absorption, circular dichroism (CD),and Fourier transform infrared (FT IR) spectroscopy, coupled with molecularsimulation. These studies have important theoretical significance for further exploringthe pharmacological actions of natural active ingredients such as absorption,distribution and metabolism in vivo.The main contents and conclusions in the thesis are summarized as follows:1. The structure, physiological functions and biological characteristics of serumalbumin were briefly stated at first in this chapter. Afterwards the research methodsand progress of binding with ligands were epitomized.2. Under simulative physiological conditions, multispectral technologies such asfluorescence, Ultraviolet visible (UV–vis) absorption, circular dichroism (CD) andFourier transform infrared spectroscopy (FT IR) were used to investigate the bindingmechanism of osthole and human serum albumin (HSA). The results manifested thatosthole queched the fluorescence intensity by forming HSA osthole compound.Based on van’t Hoff equation, the results of ΔH°and ΔS°were all positive, whichmeant that the binding of osthole to HSA was driven mainly by hydrophobicinteraction. The site markers competitive experiments revealed that the binding ofosthole to HSA mainly took place in site III. The binding distance between ostholeand HSA was determined to be3.99nm based on the F rster theory. The results ofFT–IR and CD spectra showed that the binding of osthole to HSA could inducepartial changes in the second structure of the protein.3. The binding mechanism between lysionotin and bovine serum albumin (BSA)and BSA conformational change were detected by fluorescence, UV vis absorption,circular dichroism (CD), and Fourier transform infrared (FT IR) spectroscopy,coupled with molecular simulation. Moreover, the influence of the three types of Bvitamins (VB1, VB2, VB3) on the BSA lysionotin system were studied under the same conditions. The results suggested that the the quenching mechanism oflysionotin binding with BSA was probably a static quenching through the formationof lysionotin BSA complex, whose binding process was primarily driven byhydrogen bond and van der Waals forces. The site markers competitive experimentsrevealed that the binding site of lysionotin was in the sub-domain IIA (site I) of BSA.The molecular docking results showed that lysionotin actually bound into thesub-domain IIA of BSA. Moreover, the results of3-D fluorescence, UV visabsorption, CD and FT IR spectra demonstrated that the secondary structure of BSAwas altered in the presence of lysionotin. In addition, the exist of VB1, VB2, VB3made the increase of Ksv, Ka, n, and the decrease of r, which meant VB1, VB2, VB3could all increase the stability of BSA lysionotin system. VB1changed the mainacting forces of BSA lysionotin system from hydrogen bonding and van der Waalsforce to hydrophobic force, while VB2and VB3did not change the type of actingforces. CD results showed the α helix increased. BSA molecular conformationalchange induced by the vitamins BSA binding was the main quomodo of thevitamins．4. Multispectral technologies were used to investigate the transformation of thethermodynamic property and the structure of HSA based on the binding of thecoumarin compound toddalolactone (TDT) to HSA in physiological acidity (pH7.4)and the effects of TDT on the structure of HSA. Fluorescence titration suggested thatthe fluorescence quenching of HSA by TDT was a static procedure via forming theHSA TDT complex. Binding parameters calculated from the modified Stern–Volmerequation showed that TDT bound to HSA with a strong affinity (the binding order of105L mol1). Thermodynamic analysis at different temperatures revealed that thebinding process was primarily driven by hydrophobic interactions and hydrogenbonds. The binding site of TDT to HSA mainly located in the subdomain IIA(Sudlow’s site I), and the molecular docking study visually exhibited the stereobinding modes. The binding distance between TDT and HSA was determined to be4.18nm based on the F rster theory. The surface hydrophobicity of HSA increasedupon interaction with TDT. Analysis of3-D fluorescence，UV vis absorption, CDand FT IR spectra demonstrated that TDT induced an alteration of the protein conformation.