lecture 15 cell/tissue staining Flashcards
what is chromophore
arrangement of atoms that absorb light and produce colour. double bonds or NO2 groups
what is auxochrome
functional group that attaches to tissue by chemical bonding/association
diff btw oversight stain vs selective stain
oversight for cell morphology e.g. H&E, Wright Geisma. selective stain enhance components e.g. pentachrome stain
what makes a good chemical staining method
- good color differentiation
- gives insoluble and stable color
- reproducible
- selective or specific when required
- semi quantitative
relationship btw pka, pH and ionization of tissue acidic group
acidic group: pH greater than pka ionization is favoured, more than 50% groups -ive
relationship btw staining pH and net tissue protein charge
can influence what tissue groups are ionized
effect of changing pH for Alcian Blue
pH 1-sulfated mucin stained
ph 2 sulfated and carboxylated mucin
pH 5 sulfate/carboxylated mucin and proteins stained
why changing staining pH affects intensity of cationic and anionic dye
eg more -ive charges mean more group for cationic dye to attach to. cationic stain intensity increases
why 100% of a cationic dye’s auxochromes remain ionized at the pH used for staining tissue anionic groups
n
why 100% of an anionic dye’s auxochromes remain ionized at the pH used for staining tissue cationic groups
auxochromes of anionic dyes are carboxyl or sulfonyl groups pka less than 2. pH for staining cationic tissue groups ph greater than 2
ionized acid groups are ___ charged
negatively
cationic dyes that have a positive charge when ionized (basic)
Alcian Blue and Azure B
anionic dye that has a negative charge when ionized (acidic)
Eosin Y. stains orange pink
as pH decreases ionization of ___ is favoured
basic amine groups. ionized amine are +ive charge (cationic tissue group) (anionic dye is favour red eosin Y)
when is ionization favoured for acidic fnal groups
when pka is lower acid will lose H atom and more than 50% will be negative
