Exploiting And Application Of Spectral Features On Structure And Interaction Characterization In Complex Interfacial Systems

Structure and interaction characterizations within complex interfacial systems are the basis of understanding related physical and chemical issues.Yet few experimental techniques are able to accurately characterize complex interfaces at the molecular level.Sum frequency generation vibrational spectroscopy(SFG-VS),which is known as a second order nonlinear spectroscopic technique that is sensitive to surface and interface,can reflect the microstructure and ultrafast dynamics of molecules within complex interfacial systems.SFG-VS is a robust tool for investigations on the physical and chemical processes at surfaces and interfaces.Therefore,in this thesis,we carry out spectroscopic researches by using both picosecond and femtosecond SFG-VS,aiming to deal with scientific problems associated with interfacial proteins and interfacial water molecules.Exploiting of new spectral features and the application of the existing ones offer us a unique chance to get more details on the structure and interaction of proteins at the interface,and help us find out the mechanism behind the inconsistency between the micro-scale hydrophilic behavior and the macro-scale hydrophobic property of material’s surface.The dissertation contains 6 chapters.In chapter one,we clarify the importance of structure and interaction characterizations within complex interfacial systems,summarize SFG-VS studies on protein and water molecules within complex interfacial systems,and briefly introduce the ideas and main contents of this thesis.In chapter two,human islet amyloid polypeptide(hIAPP)is taken as an example to help illustrate the development and application of amide Ⅱ and amide Ⅲ spectral features on protein structure characterization within biological interfacial systems.The combination of spectral information from multiple amide backbone vibrational modes permits us to differentiate the secondary structures of intermediate species during hIAPP misfolding at the surface of negatively charged lipid membrane,to unravel the structural evolution of hIAPP misfolding and aggregation,and to investigate the association between protein misfolding and cytotoxicity.On the basis of these understandings,the influence of environmental factors(including protein concentration and pH value)on protein structural evolution and membrane perturbation is further explored.In chapter three,we introduce the development and application of protein N-D spectral feature.Fermi resonance effect of amide backbone vibration in deuterated proteins can be used as an effective method to measure the hydrogen-bonding interactions within protein molecules.In chapter four,we present a spectroscopic study on Teflon film with macro-scale dewetting behavior and micro-scale hydrophilic property at the same time.By analysing the static structure and vibrational relaxation dynamics of H2O molecules at Teflon/air interface,we find the reason behind the "macro-scale hydrophobic,while micro-scale hydrophilic" phenomenon on Teflon surface.In addition,negatively charged hydroxide ions(OH-)are found on Teflon surface,thus providing direct experimental evidence for the existence of charged species on Teflon surface.In chapter five,we investigate the interactions at the interface between Teflon and bulk water.The interactions between water-water and Teflon-water at the Teflon/bulk water interface mediated by environmental factors(including ionic strength,solution pH,and hydrogen-bonding coupling strength)are systematically studied.In chapter six,we summarize the main conclusions in the thesis and offer prospects for futher works.