L4 Flashcards
How does NA increase?
With wider and closer lenses
Replacing air with oil
whats the most efficient way of sterilizing
autoclaving
what is spectrophotometry
measures how much a particular color of light passes through a substance to identify and quantify the substance
what are the units of absorbance
there are none
what are units of transmittance
unitless
whats a direct measurement
counting exact amount of the thing you want
indirect measure
might not be exact, but could be more convenient
(ie, count shoes in room but not people, what if someone has more than one pair? )
what do bacteria cell walls do in spectrophotometry
they scatter light
do bigger cells scatter more light than small cells in spectrophotometry
yes
what part of DNA/RNA absorbs light
the bases (not sugars)
where do RNA/DNA absorb light best
260nm
do different DNA from different species change in regards to absorbance
no - all sequences of DNA use the same E value for double stranded DNA
where do proteins absorb light best
280 nm
when working with DNA and protein, what happens
there’s normally overlap because their absorbance optimum is around the same value (contamination)
by comparing 260 (DNA) and protein (280), what can we determine
the purity of each of them
what is the ration of pure DNA In 260/280 conditions?
2
what is the ration of pure protein In 260/280 conditions?
0.55
Is protein in spectrophotometry variable?
yes because of the different amino acids
what an indirect measurement for protein
Bradford assay
what is the Bradford assay
measurement of color change when coomassie blue dye binds proteins
(blue = protein)
not perfect though
what is the biuret assay
measurement of colour change when Copper II sulfate reacts with proteins under alkaline conditions
reaction turns purple when copper reacts with peptide bonds
for color to chnage in a biuret assay, what is required?
protein, not amino acids because they dont have peptide bonds
what is technological miniaturization
cuvette less spectrophotometry that doesn’t require diluted sample and only requires a drop
whats the first identification of Bacteria
looking at it under the microscope
