내용요약(Abstract)
Since its invention in 1931, transmission electron microscope (TEM) has established itself as one of the most powerful tools available to biologists. Superior resolving power of TEM enabled direct visualization of viruses, cellular ultrastructures and large protein complexes. Most notable technical developments in the early days include heavy metal staining for enhanced image contrast and preparation of cellar specimen. More recently, advancement in sample preparation techniques and development of algorithms for image processing as well as availability of computation power pivoted rapid improvement of resolution limit of the analysis and widened the range of biological events that can be studied. In particular, preservation of biological specimen in frozen-hydrated state, namely cryo-electron microscopy (Cryo-EM), allows for rapid immobilization of biological macromolecules in near-physiological state, and therefore subtle structural changes from varying environment can be detected. In addition, merging of projection images obtained from TEM into a dataset enables 3D reconstruction of biological specimen, and averaging of images that contain identical particles greatly improves achievable resolution. Through molecular docking, moderate resolution TEM 3D reconstruction can directly complement x-ray crystallography and NMR data, and enables structural analysis of large biological macromolecules in near-atomic level. Growing efforts are now put into the combination of various TEM techniques such as electron tomography, electron crystallography and single particle analysis in order to reveal complex biological event that could not be elucidated before. Moreover, new concept of direct visualization of live biological specimen under vacuum condition of TEM is receiving a spotlight in a hope to study molecular dynamics in situ.