Chem Path Flashcards

0
Q

Define avidity

A

Function of strength and number of binding sites

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1
Q

Define affinity

A

Strength of association

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2
Q

Define immunoassay

A

Any analytical method which uses Abs as reagents, the results from which assist in diagnostic interpretation

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3
Q

What is an homogenous assay

A

Signal changes when Ab and Ag bind. Therefore no separation step is required

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4
Q

What is an heterogenous assay

A

Requires separation of bound and unreacted molecules to determine/assess result

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5
Q

What are the three types of assay and an eg of each

A

Immunometric assay - ELISA, IFMA, IRMA
Equivalence precipitation - gel diffusion
Immunoassay (competitive) - RIA, FIA

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6
Q

How does one produce polyclonal antisera?

A

Inject animal with Ag (possibly needs to be bound to haptogen to increase immunogenicity)
Gives rise to mixed/polyclonal population = greater affinity than monoclonal Abs

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7
Q

How does one produce monoclonal Abs?

A

Inject animal with Ag.
Isolate one plasma cell and fuse that cell to a tumour cell.
Screen hybridoma and allow clonal expansion

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8
Q

Advantage of monoclonal Ab

A

Highly specific

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9
Q

Disadvantage of monoclonal Ab

A

Lower affinity

Not truly representative of analytes with multiple molecular forms

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10
Q

Why characterize Abs?

A

Determine diagnostic performance of test

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11
Q

What factors are assessed when characterizing Abs

A

Affinity
No. of binding sites
Specificity

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12
Q

How do we characterize Abs practically

A
Titre (affinity and concentration using dilution curve)
Scatchard analysis (higher the affinity constant [K] better the sensitivity, also looks at no of binding sites)
Cross reaction studies (use structurally related molecules)
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13
Q

Methods of Ab purification

A
Ig precipitation
Ion-exchange chromatography
Affinity chromatography 
Ab fragments
Protein A/G chromatography
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14
Q

Types of label

A
Enzyme linked
Flourophores
Chemiluminescense
Radioisotopes
Particle precipitatates 
Etc etc
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15
Q

Eg of a homogenous assay

A

EMIT

Enzyme-multiplied immunoassay technique

16
Q

What is turbidimetry

A

Measure of loss of intensity of transmitted light due to the scattering effect of particles in a solution

17
Q

What is Nephelometry

A

The measure of scattered light at a given angle to the transmitted light

18
Q

Eggs of substances that can cause assay interference

A

Human anti mouse Ab
Complement
Rheumatoid factor

19
Q

What is the hook effect

A

Production of artefactually low results from samples that have very high level of Ag.
Most commonly found in immunometric assays

20
Q

What is only prerequisite for analyte in capillary GC

A

Analyte must be volatile

21
Q

Pros of GC-MS

A

Reliable and reproducible
Wide range of analytes
Technically straight forward

22
Q

Cons of GC-MS

A

Some analytes require time consuming extraction etc

Cost (equipment, training, libraries, isotopes)

23
Q

What is Trinder’s reagent

A

Contains mercuric chloride and HCl to precipitate proteins

24
Q

Five causes of FH

A
LDLR mutation
ApoB mutation
PCSK9 gof
Phytosterolaemia (ABCG5G8)
ARH def
25
Q

What does ApoE bind to

A

LRP
LDLR
Heparin sulphate proteoglycans

26
Q

How to diagnose dysBlipoproteinaemia

A

Ultracentrifuge
Broad B band on gel electrophoresis
Sequence gene
ApoE concentration

27
Q

How do abn ApoE become hyperlipidaemic

A

Overproduction (diabetes, nephrotic, obesity, renal disease, pregnancy, alcohol)
Underexcretion (hypothyroid, post menopausal, low HL activity, autoantibodies)

28
Q

How to quantify compounds in GC-MS

A

Semiquantitation - ratio between peak of interest and know internal standard (serial)

Isotope dilution MS - known [] of pure isotope

29
Q

What to do if sample is too large or hydrophilic to be volatilised

A

Derivitisation - dry under inert gas, then volition to form TMS esters

30
Q

How does one identify compounds in MS

A

Libraries
Ion chromatograms
Deconvolution software

31
Q

Five causes of FH

A
LDLR mutation
ApoB mutation
PCSK9 gof
Phytosterolaemia (ABCG5G8)
ARH def
32
Q

What does ApoE bind to

A

LRP
LDLR
Heparin sulphate proteoglycans

33
Q

How to diagnose dysBlipoproteinaemia

A

Ultracentrifuge
Broad B band on gel electrophoresis
Sequence gene
ApoE concentration

34
Q

How do abn ApoE become hyperlipidaemic

A

Overproduction (diabetes, nephrotic, obesity, renal disease, pregnancy, alcohol)
Underexcretion (hypothyroid, post menopausal, low HL activity, autoantibodies)

35
Q

How to quantify compounds in GC-MS

A

Semiquantitation - ratio between peak of interest and know internal standard (serial)

Isotope dilution MS - known [] of pure isotope

36
Q

Diagnosis of dysbetalipoproteinaemia

A
  • ultracentrifugation for VLDL and demonstration of B-VLDL
  • ultracentrifugation for VLDL, cholesterol enriched
  • remnants (IDL) on no denaturing acrylamide electrophoresis
  • broad b band on agarose electrophoresis
  • apoE conc