Visualization of molecular binding sites at the nanoscale in the lift-up mode by amplitude-modulation atomic force microscopy.

We report a new approach to visualize the local distribution of molecular recognition sites with nanoscale resolution by amplitude-modulation atomic force microscopy. By integrating chemical modification of probes, photothermal excitation to drive a cantilever, and lift-up scanning over surface topography, we successfully visualized binding sites provided by streptavidin on a solid surface for biotin attached on an AFM probe. The optimization of measurement conditions was discussed in detail, and the application of the technique was verified with a different ligand-receptor system.

Real-time and observation of structural evolution of giant block copolymer thin film under solvent vapor annealing by atomic force microscopy.

An instrumentation technique for real-time, and real space observation of microphase separation was proposed for ultra-high molecular weight block copolymer thin films (1010 kg mol, domain spacing of 180 nm) under high solvent vapor swelling conditions. This is made possible by a combination of a homebuilt chamber which is capable of supplying sufficient amount of vapor, and force-distance curve measurements which gives real-time swollen film thickness and allow active feedback for controlling the degree of swelling. We succeeded in monitoring the domain coarsening of perpendicular lamellar structures in polystyrene--poly(methyl methacrylate) thin films for eight hours tapping mode imaging.

Detection of streptavidin-biotin intermediate metastable states at the single-molecule level using high temporal-resolution atomic force microscopy.

Although the streptavidin-biotin intermolecular bond has been extensively used in many applications due to its high binding affinity, its exact nature and interaction mechanism have not been well understood. Several reports from previous studies gave a wide range of results in terms of the system's energy potential landscape because of bypassing some short-lived states in the detection process. We employed a quasi-static process of slowly loading force onto the bond (loading rate = 20 pN s) to minimize the force-induced disruption and to provide a chance to explore the system in near-equilibrium.

Molecular diffusion and nano-mechanical properties of multi-phase supported lipid bilayers.

Understanding the properties of cell membranes is important in the fields of fundamental and applied biology. While the characterization of simplified biological membrane mimics comprising liquid phase lipids has been routinely performed due to the ease of fabrication, the characterization of more realistic membrane mimics comprising multi-phase lipids remains challenging due to more complicated fabrication requirements. Herein, we report a convenient approach to fabricate and characterize multi-phase supported lipid bilayers (SLBs).