practicals Flashcards
stages of capture ELISA
- Capturing Ig absorbed onto solid phase
- Ag added (transporter protein)
- labelled detection Ig added > binding in presence of Ag
- substrate added w HRP label
HRP label
catalyses oxidation of substrate for color change
Ag conc proportional to color produced
horse radish peroxidase
characteristic of capture and detector antibody
cross-reactive
total protein concentration determination in ELISA
Colorimetric assay
determination of novel protein percentage of total protein in test sample
use of 2 assays > capture ELISA/ colorimetric assay
what does ELISA stand for
Enzyme-linked immunosorbent assay
ELISA error factors
insufficient plate washing
oversaturation of wells with conjugate
contamination
incubation timing
standard curve range too high
ELISA advantages
high efficiency
simultaneous analysis w/o pre-sample treatment
safe/ eco-friendly
ELISA disadvantages
antibody instability
refridgerated storage and transport of antibody
tween-20 in ELISA
non-ionic detergent decreasing asorption of non-specific Ig to ELISA wells. Block vacant binding sites by *H bonds/ Van der Waals. *
Use of calf serum in ELISA
contains albumin
blocks non-specific binding
need for 2 antibodies in ELISA
primary antibody is specific/ facilitates immbolisation of antigen
secondary antibody contains enzyme and has wider range of targets> facilitates Ag detection
5 classes of antibodies
IgA/ IgE/ IgD/ IgG/ IgM
IgA
protects against pathogens
Found in mucous, saliva, tears, and breast milk.
IgD
activates basophils and mast cells
part of BCR
IgE
role in allergic reactions
protects against parasitic worms
IgG
can cross placenta into foetus
secreted by plasma cells into blood
IgM
early stages of immunity
secreted into blood / surface of B cell
what does practical 1 entail?
plasmid isolation, PCR and electrophoretic analysis of restriction digested DNA
recombinant plasmid in practical 1
cDNA sequence cloned into spec EcoR1 site
blt101 cDNA insert
miniprep
isolation of plasmid DNA from small-scale bacterial culture
how do you make E.coli cell competent?
CaCl2/ low temperature treatment of cells
making cell wall permeable to DNA> plasmid uptake
transformation
frequency in E.Coli cells
plasmid uptake
1 in 100 cells maximum
plC19H
non-recombinant/ no novel gene inserted in lacz
carries gene enabling ampicillin resistance
enables detection of transformants in ampicillin medium
MCS of plc19H
multiple cloning site
contains LacZ
recombinant plasmids carry inserts cloned into MCS > disrupts LacZ
LacZ gene
encodes alpha peptide of beta galactosidase whose substrate is lactose
non-recombinant plc19H produce functional beta galactosidase
beta galactosidase detection
agar inclusion of X-gal> cleaved and accumulates in cells producing blue colonies
blue colonies
contain non-recombinants
white colonies
contain lacZ
miniprep
solutions (detergent/ alkali mixture) lyse bacterial cells, denature/ solubilise cellular components/ allow RNAase to degrade RNA.
Plasmid DNA trapped on matrix, contaminants washed away.
plasmid DNA released/ eluted from miniprep column.
EcoR1 restriction endonuclease in transformation
cuts target gene/ plasmids for matching sticky ends
gene can be inserted in either direction
reverse= nonsense