Different combinations of amino acids give different properties to proteins. Therefore, the main feature that should be used in distinguishing proteins from each other is the amino acid sequence of proteins. However, proteins can be distinguished by their size and the biochemical properties as well.
Microscopes are one of the laboratory tools used to maximize the visual acuity of a certain specimen, it maybe a living or non-living organism or object. Thus, microscopes are widely used in these laboratories to increase microscopic observation with entities that cannot be perceived thru the naked eye. However, for scientisits to determine such specimen is a living thing if there's a presence of cell. Cell cannot be viewed via the visual organs alone but with the microscope a living specimen can be discerned with its characteristics such as cellular structure, slight and fidgety movement and other particular details..
The physical distance that separates them on the chromosome.
Gel electrophoresis separates fragments on the basis of weight and electric charge. Heavier and/or positively charged fragments don't go as far as lighter and/or negatively charged ones.