IN-SITU AND EX-SITU STRUCTURAL-ANALYSIS OF PHOSPHOLIPID-SUPPORTED PLANAR BILAYERS USING INFRARED-SPECTROSCOPY AND ATOMIC-FORCE MICROSCOPY

We report here both the in-situ and ex-situ study of phospholipids inc orporated into supported planar bilayers using spectroscopic and imagi ng techniques. We have demonstrated the feasibility of using attenuate d total. reflectance infrared (ATR-IR) spectroscopy for the insitu stu dy of Langmuir monolayers at the air-water interface. This method resu lts in a higher signal-to-noise ratio and more easily measured molecul ar orientation when compared with the external reflection infrared met hod previously developed. For ex-situ studies, we have demonstrated th at a combination of IR spectroscopy and atomic force microscopy (AFM) provides detailed information concerning the conformation and distribu tion of the bilayer components. Our AFM images of the phospholipid 1,2 -dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) show molecularly-resol ved phospholipid headgroups existing in a well-ordered, hexagonal-type lattice with unit cell areas obtained from these images corresponding to molecular areas commensurate with those obtained by X-ray diffract ion from analogous phospholipid single crystals. Our results demonstra te that the combination of IR and AFM is a powerful tool for structura l investigation of supported planar bilayers.