Protein methods Flashcards
Digestion of proteins to measure nitrogen
Kjeldahl
TP reference method
Kjeldahl
2 steps in Kjeldahl
Kjeldahlization
Ammonia measurement (colorimetric)
conversion of N to NH3
Kjeldahlization
agents used in Kjeldahlization
Sulfuric acid
Cupric sulfate
Potassium sulfate
digesting agent (340-360C)
*kjeldahlization
Sulfuric acid
catalyst
*kjeldahlization
Cupric sulfate
increase boiling pt
*kjeldahlization
Potassium sulfate
2 reactions that may be used in ammonia measurement
*kjeldahl
Nessler’s reaction
Berthelot reaction
use of double iodide of Hg and K
Nessler’s reaction
Nessler’s reaction
Ammonia + Nessler’s rgt –> Ammonium dimercuric iodide (YELLOW)
Berthelot reaction
Ammonia + Alk. Hypochlorite –> Indophenol BLUE
measurement of RI
refractometry
formation of violet-colored chelate betw. cupric ions and peptide bonds (measured at 540 nm)
Biuret
Biuret reagent composition
Cupric ions
Tartrate salt
Potassium iodide
Biuret rgt:
Breaks peptide bonds
Cupric ions
Biuret rgt:
Keeps copper in soln
Tatrate salt
Biuret rgt:
Stabilizes cupric ions
Potassium iodide
Protein binds to dye and causes spectral shift in the absorbance max of dye
Dye binding
Used dyes for Total protein measurement
Bromphenol blue
Coomassie brilliant blue
Lissamine green
Amido black 10B
Ponceau S
Methods for Albumin measurement
Salt precipitation
Dye binding
Electrophoresis
precipitating agent in Salt Precipitation
Sodium sulfate (precipitates Globulin)
precipitated in high salt conc.
Globulin
left in supernatant which will be measured using Biuret reaction
Albumin
Dyes for Albumin measurement
Methyl orange
HABA (2,4-Hydroxybenzone benzoic acid)
Bromcresol green
Bromcresol purple
nonspecific dye for albumin
Methyl orange
albumin dye with many interferences (salicylates, bilirubin)
HABA (2,4-Hydroxybenzone benzoic acid)
Sensitive dye for albumin
Overestimates low alb lvl
Bromcresol Green
Most commonly used dye for Albumin
Bromcresol GREEN
Specific, sensitive, and precise dye for Albumin
Bromcresol Purple
inc. negativity inc. number (conc.) = ?
Inc. migration distance
most anodic protein
albumin
least anodic protein
gamma globulin
support media for protein electrophoresis
Cellulose acetate
Agarose gel
Inc. conc. of fractionated protein = ?
Darker band fraction
Used to compute the area under the absorbance where the medium is placed after electrophoresis
Scanning densitometer
Normal: Alb, a1, a2, B
INCREASED: y
monoclonal gammopathy
Decreased: Alb, a1, B, y
Increased: a2
Nephrotic syndrome
Normal: B, y
Decreased: Alb
Increased: a1, a2
Acute inflammation
Normal: Alb, a1, a2, B
Severely decreased/none: y
Hypogamma globulinemia
Normal: Alb, a2, B, y
Severely decreased: a1
a1 antitrypsin deficiency
Fused increase of B and y
all are decreased
Cirrhosis (B-y bridging)
*diagnostic
Normal: Albumin
Increased: a1, a2, B, y
Chronic inflammation
Demonstrate other specific proteins IN THE GLOBULIN FRACTION, outside albumin fraction
High resolution protein electrophoreis
uses higher voltage couple with a cooling system and more concentrated buffer
High resolution protein electrophoreis
Turbidimetric methods for proteins
SSA
TCA
Benzethonium chloride
Proteins are precipitated as particles and turbidity measured spectrophotometrically
Turbidimetric methods:
SSA
TCA
Benzethonium chloride
Rapid test easy to use and perform
Turbidimetric methods:
SSA
TCA
Benzethonium chloride
Has unequal sensitivity for individual protein
Turbidimetric methods
Dye binding
Accurate method for urine protein
Biuret
Initial biuret reaction
Folin Lowry
Oxidation of AA residues by a reagent with a blue resulting color
Folin Lowry
Reagent used in Folin Lowry
Folin Phenol reagent
Resulting color in Folin Lowry method
blue
Very sensitive test for urine protein
Folin Lowry
Has limited linearity of the reaction
Dye binding for proteins in other body fluids
(Coomassie blue, Ponceau S)
diagnostic method for MS
CSF protein electrophoresis
diagnostic result for MS
Oligoclonal banding in CSF protein electrophoresis
conditions in the blood and tissues outside the CNS
Multiple myeloma (serum/urine)
Monoclonal and Polyclonal gammopathies
Ave nitrogen content in proteins
16%