Membrane fusion is a basic biophysical process involved in cell's physiological activities. The value of studying the exocytosis of mammalian cells and yeast cells lies in that a highly conserved SNARE (Soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein super family mediates this process and is proposed to be the core protein machinery for the membrane. The SNARE proteins located on plasma membrane and vesicle membrane are assembled together to form a trans-SNARE bridging two separate membranes and initiating membrane.;My research centers on how SNARE assembly involved in yeast cells' exocytosis promotes membrane fusion between yeast vesicle and plasma membrane. Site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) are well established techniques in membrane protein structural study. Fluorescent labeled Lipid mixing assay is employed to test the functional activity of SNARE. The data from trans-SNARE assembly on membrane indicates its potential catalyst role in membrane fusion; The transmembrane organization of neural syntaxin-analogue Sso1p is a well defined alpha helix across membrane based on accessibility profile of magnetic reagents; Transmembrane domain of Sso1p tends to form oligomers of stoichiometries ranging from 3 to 6 in the membrane, which likely act as a scaffold of formation and clustering of multimeric trans-SNARE supra complex prior to lipid mixing; Sso1p TMD conformational change involved in the transition from trans- to cis-SNARE is also disclosed by EPR spectra, shedding light on the structural and temporal relationship between SNARE assembly intermediates and substeps of membrane fusion.