350 - Topic 8 (Staining Theory) Flashcards
Most stains in histology are dyes but other techniques are used as well…
metal impregnation
and histochemical rxn for example
what is a dye?
it is a coloured substance that has an affinity for particular substrate
4 examples of natural dyes used in histo today
Haematoxylum campechianum
carmine (female cochineal insect, Dactylopius coccus)
orcein (found in several lichens, esp. Rocella tinctoria)
saffron (from the stifma of the saffron crocus, Crocus sativus)
synthetic dyes all begin as…
aromatic hydrocarbons (derivatives of benzene) which are subbed with various functional groups to absorb different wavelengths of light, which are perceived as different colours
this is a molecular structure that absorbs visible wavelengths of light, which makes it appear to be a particular colour
chromophore
T or F. The more ‘spread out’ the electrons are in an organic molecule, the more likely it is to absorb visible wavelengths of light
T!
the part of the dye that contains the chromophore is called the
chromogen
- colour generator
what is an auxochrome?
molecular structure that allows dye to attach to the tissue
- usually by forming salts with tissue anions or cations
- auxochromes are ionized (either + or -)
dye that has an anionic auxochrome
anionic or acid dye
anionic auxochromes
carboxyl (-COOH)
hydroxyl (-OH)
sulphonic (-SO3H)
they ionize to form…
COO-
O-
SO3-
common binding sites of anionic dyes
specific amino acids such as lysine, histidine, arginine
common anionic dyes
eosin
orange G
Biebrich scarlet
acid fuchsin
cationic auxochrome
AMINO GROUP -NH2
common binding sites of -NH3+ (cation)
phosphate groups of nucleic acids and sulfated polysaccharides (such as cartilage, basophil granules and acid mucins)
common cationic dyes
hematoxylin
crystal violet
methylene blue
basic fuchsin
