Staining theory Flashcards
what is a dye
coloured substance that has affinity for a substrate
what is a chromophore
structure that absorbs visible wavelengths of light causing delocalization of electrons
T/F double and triple bonds are more delocalized than single bonds
T
what is a chromogen
part of dye that contains chromophore
what is an auxochrome
allows dye to attach to tissue by ionization
what do anionic (acid) dyes contain
anionic auxochrome
T/F categorization of acidic and basic dyes are based on their pH
F
what chemical groups are anionic auxochromes
COOH
OH
SO3H
what groups do anionic auxochromes bind to
positively charged tissue like lysine, histidine, and arginine
what are common anionic dyes
eosin, orange G, Biebrich scarlet, acid fuchsin
what chemical groups are cationic auxochromes
NH2
what do cationic auxochromes bind to
negatively charged tissue like cartilage, granules, and mucins
what are common cationic dyes
hematocylin
crystal violet
methylene blue
what chemical group is yellow
nitro (NO2)
what requirement does a dye need
auxochromes (COOH, OH, NH2)
what is a mordant and what does it do
links the dye to tissue
what is a dye lake
a dye with a mordant. eg hematoxylin
what does an accentuator do
incrrease intensity of a dye
what is a neutral dye
mix of acid and basic dyes eg. romanowsky
what step is NOT used in progressive staining
differentiator NOT used
what is regressive staining
overstained tissue is differentiated
what is metachromasia
staining a different colour than the solution
how does a metachromatic stain work
cationic dyes form aggregates with negatively charged sites in close proximity
what substances stain metachromatic
mucins and amyloid
what is polychromasia
solution contains several dyes to make many colours
common polychromatic dye
methylene blue
what are 3 chemiacl stianing mechanisms
covalent
ionic
hydrogen bonding
what is covalent bonding
sharing of electrons eg schiff in PAS
what is ionic bonding
attraction between unlike charges that are weaker than covalent but stronger than hydrogen bonding
what will interfere with hydrogen bonding
water
what stain uses hydrogen bonds
congo red for amyloid
what are two physical staining mechanisms
selective solubility and porosity
what is selective solubility
demonstrates lipids by migrating from solvent into tissue
what is porosity
stains connective tissue as smallest dye applied first then bumped by larger dye
what are vander waals forces
intermolecular attraction due to polarity
what stain demonstrates vander waals
congo red
what are histochemical stains
do not employ a dye or stain but use chemical reactions to form a color
stain that demonstrates histochemical staining
perls prussian blue
what silver staining methods are there
argentaffin
argyrophil
metallic substitution
what is an argentaffin
substance that bind and reduce silver
what are examples of argentaffin substances
melanin, formalin, and neurosecretory granules
what in an argyrophil
bind but NO reduce silver
reducing agent needed to help visualize the bound silver
T/F argyrophil methods demonstrate argentaffin substancves
T
examples of argyrophil substances
urates, granules, and reticulin fibers
what is metallic substitution
silver will replace calcium and bright light is used to reduce the silver
silver shown = calcium was present (indirect method)
what stain uses metallic substiution
Von Kossa
What happens if a chemical compound contains even numbers of cationic and anion groups
anionic always wins (shown in an iline blue)
what stain uses the direct method of metallic substitution
alizarin red S stain
why does Bouins fluid stain intensely compared to others
NO2 groups are mordants
