DIRECT OBSERVATION OF UNCOATED SPECTRIN WITH ATOMIC-FORCE MICROSCOPE

Spectrin molecules extracted from human blood cell membrane have been examined by atomic force microscopy (AFM) without using shadowing or s taining procedures. A drop of the solution containing spectrin molecul es was deposited on the freshly cleaved mica substrate. After about 1 min, the residual solution was removed with a piece of filter paper. A fterwards the sample was imaged with a home-made atomic force microsco pe (AFM) in air in a constant force mode. The obtained AFM images reve aled that the spectrin molecules prepared from the above procedures ex hibit several kinds of structures as follows: (i) the compact rod-like spectrin heterodimers with a length of around 100 nm; (ii) bent or cu rved linear tetramers with a length of around 200 nm; (iii) somewhat c urved spectrin hexamers, octomers or decamers with lengths of about 30 0, 400, or 500 nm; and (iv) high oligomers with a length above 1 000 n m.