Basic electron microscopy of aquatic viruses
For high - resolution images , samples should be sterile and free from bacteria and other large particles .
Filter through membrane filters of 0.22–0.45 µm pore size .
Wash in a buffer , e . g . , 0.1 M ammonium acetate ( pH 7 ) , in an ultracentrifuge with a fixed - angle rotor ( 25,000g or 25,000 rpm for 1 h ) .
Deposit a drop of virus suspension on a grid Leave for 30s for adsorption of viruses .
Add a drop of stain .
Withdraw liquid using filter paper .
Operate transmission electron microscopes ( TEMs ) at 60–80 kV .
Cool the object stage with liquid nitrogen to limit contamination by hydrocarbon molecules present in the column ( and hence loss of resolution ) .
