Why Do Biologists Use Specific Dyes for Different Cell Types?

[FrancisZ]

Quick Questions...


Why do Biologists use different dyes for different slide samples?

I've heard of iodine, and methylene blue being used for plant and animal cells respectively.
Does it matter? And how come?


Does it have to do with the reaction? Would Iodine dissolve an animal cell like Cheek cells if you used it instead of Methylene blue?

 

[Bacat]

Different stains are used to highlight different structures in the cell. By using the appropriate stain you could improve visibility of cell components depending on their make-up. If I remember right methylene blue is most useful for studying the nuclei of cells. Iodine is good for tagging starches, among other things. Using the right stain will improve the quality of information the biologist gets.

Microbiologists also use a gram-negative and a gram-positive stain to identify which class of bacteria they have. In general, gram-positive bacteria are not harmful but gram-negative bacteria are (to humans), so this is a good way for us to determine which is which. The stain selectively adheres to different types of cell-walls.

In modern days biologists often use fluorescent markers also. Here, the color of the dye is defined by the molecules of dye themselves. The biologist can excite the fluorescent dyes selectively using specific wavelengths of light and thus pick out which parts of the cell have been tagged. This is particularly useful for in vitro (live) microscopy where a biologist might want to study how certain markers move within a cell. The dyes do not harm the cell and yet provide useful information.