Molecular imaging of membrane proteins and microfilaments using atomic force microscopy

Abstract

Atomic force microscopy (AFM) is an emerging technique for a variety of uses involving the analysis of cells. AFM is widely applied to obtain information about both cellular structural and subcellular events. In particular, a variety of investigations into membrane proteins and microfilaments were performed with AFM. Here, we introduce applications of AFM to molecular imaging of membrane proteins, and various approaches for observation and identification of intracellular microfilaments at the molecular level. These approaches can contribute to many applications of AFM in cell imaging.

Figure 1

Principle of operation and operation modes in AFM. (A) Schematics of atomic force microscopy principle. (B-E) Four widely used atomic force microscopy operation modes: (B) DC mode, (C) AC mode, (D) lateral force microscopy, and (E) Force spectroscopy. A typical force-distance curve is shown (E). The cantilever is not deflected yet (1). As the tip approaches to the surface, the cantilever bends upward by repulsive forces (2). As the tip retracts from the surface, the cantilever bends downward by attractive forces between the tip and sample (3).

Figure 2

Identification of microfilaments by on-stage labeling/imaging. Samples mounted on the scanner tube are sequentially imaged in aqueous solution by AFM before (pre-imaging) and after (post-labeling) labeling with molecular probes including antibodies. Line profiles from pre-imaging (from a to b) and post-imaging (from a' to b') are compared.