| Interface is a transition region of two adjacent phases,existing widely in nature.The composition of interface is different from that of the adjacent phases.The molecules or atoms at interface form an ordered structure by forces of the adjacent phases.Biochemical processes usually occur at interfaces or surfaces,thus surface/interface is one of the most important areas in scientific research.Both second harmonic generation(SHG)and sum frequency generation(SFG)are secondorder nonlinear processes,the intensity of which depends upon the nature of the anisotropic charge distribution and the degree of asymmetry of the studied material structure.SHG/SFG is highly sensitive to surface/interface because the central symmetry is broken on surface/interface.Due to the surface-specificity of SHG,derived technique—second harmonic light scattering(SHS)has been reported to measure the adsorption and transport of molecules on membranes.Due to the surface/interface-sensitivity of SFG,SFGvibrational spectroscopy(SFG-VS)has been used to measure the molecular structure and orientation of the model cell membrane—phospholipid bilayer.Membrane fusion is a momentous biological phenomenon,which refers to the process of two opposed membranes touching and merging.Membrane fusion is integrant for numerous basic vital movements,such as fusion between enveloped viruses and host cells,vesicle trafficking,mitochondrial fusion,fertilization,etc.Membrane fusion is also of great application value in the development of biomedicine,such as the use of liposomes to deliver drugs to focal cells for therapeutic effect.In this paper,SHS,SFG-VS and dynamic light scattering(DLS)were applied to study the membrane fusion induced by calcium ions.The specific work content is divided into the following several parts:(1)SHS was used to study the effects of different phospholipid components on the adsorption and transport of malachite green on liposomes,and SFG-VS was applied to detect the different characteristics of the model cell membrane composed of different phospholipid molecules complexed with calcium ions.(2)SHS and DLS were used to detect and validate calcium ion-induced fusion of liposomes.(3)SFG-VS was used to measure the orientation of related functional groups of phospholipid molecules and to analyze the possible mechanisms of calcium ion-induced fusion at the sub-molecular level.The results showed that the dehydration of phospholipid molecules caused by calcium ions is the key factor for membrane fusion.Chirality is one of the main forms of asymmetry.Many behaviors of organisms are carried out through chiral selection.Chirality at the biological interface is closely related to complex biochemical processes.Different chiral interfaces have different effects on molecular adsorption and cell growth.The occurrence of protein adsorption at different interfaces has a great influence on specific biological function.Due to the influence of steric hindrance,the modification of different chiral amino acids on the surface can affect the adsorption of proteins or cells on the surface,resulting in different behaviors of proteins or cells.In this paper,SFG-VS and microscopy were used to study the effects of different chiral surfaces on protein adsorption.The specific work content is divided into the following parts:(1)SFG-VS was applied to confirm the construction of the chiral surface.(2)SFG-VS was used to measure the difference of interaction between proteins and surface modified by different chiral amino acids.(3)Optical microscopy and fluorescence confocal microscopy were used to observe the difference of cell adhesion and cell growth on the surfaces modified by different chiral amino acids,revealing the effects of modification by different chiral amino acids on the protein adsorption.The results showed that the modification of L-Cysteine could promote the protein adsorption on the surface,while the modification of D-Cysteine could inhibit the protein adsorption on the surface. |
