Atomic Force Microscopy to Visualize Phage–Antigen Interactions

Abstract

Source: Williams, S. M. et al. Novel Atomic Force Microscopy Based Biopanning for Isolation of Morphology Specific Reagents against TDP-43 Variants in Amyotrophic Lateral Sclerosis. J. Vis. Exp. (2015)

This video demonstrates tapping-mode AFM to visualize phage–antigen interactions on a mica surface. It outlines the steps for antigen immobilization, phage binding, and high-resolution nanoscale imaging.

Protocol

1. Atomic Force Microscopy (AFM) Process

1. Add 10-20 μl of the target antigen to cleaved mica and incubate for 5-10 min. Wash the mica 5 times with water. Add 10-20 μl of the phages to the mica and incubate for 5-10 min.
2. Wash the mica 5 times again with water and allow the mica to air dry. Visualize phage binding using AFM. Execute the AFM imaging process using AFM tapping mode with a Nanoscope IIIa controller in air at room temperature (RT). The silicon AFM probes have a resonant frequency of 300 kHz and a spring constant of 40 N/m. Use a scan rate of 3.05 Hz and a scan resolution of 512 samples/line.
3. Process the images by basic flatt....

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Tomlinson I and J Libraries	MRC (Cambridge, England)
Sheets Library	MRC (Cambridge, England)
KM13 Helper Phage	MRC (Cambridge, England)
Sodium Chloride	Macron	7647-14-5
Sodium Phosphate Dibasic	Amresco	0404-1KG	Irritant
Potassium Chloride	EMD	PX1405-1	Irritant
Potassium Phosphate Monobasic	Amresco	0781-500G	Irritant
Mica	Spruce Pine Mica	24365
Centrifuge	Thermo Scientific	Sorvall RC 6+
Nanoscope IIIa Atomic Force Microscope	Veeco
AFM Probes	VistaProbes	T300R-10