Conjugate Chemistry
Citrate’s role in gold conjugation is _________
what is Acts as a reducing & stabilizing agent; imparts negative charge.
This buffer is typically used in conjugate storage
what is Tris or PBS + 0.05 % Tween-20.
The strip is most sensitive to humidity is
what is the Conjugate pad.
An accelerated stability test is what
What is an elevated-temperature test predicting shelf life.
The test line fades after storage because
What is antibody denaturation or AuNP aggregation.
Loss of functional antibody reduces capture efficiency.
Adding salt too soon to a gold conjugation causes _____.
Aggregation.
Ionic strength important for stability because
What is ionic strength balances charge and reduces aggregation risk.
How does poor drying impact flow time
What is causing delayed release & uneven migration.
Water content changes viscosity & flow kinetics.
37C or 45 °C for stress testing are commonly used because
What is they approximates months of storage at 4 °C.
A “tailing” conjugate front indicates what
What is uneven release or over-hydrated pad.
Check surfactant level / drying profile
pH affect antibody adsorption by blank
What controls ionization of amino / carboxyl groups;
Tween-20 improve conjugate mobility by
What is Providing steric hindrance & reducing surface binding.
Sugars like trehalose improve stability by
What is forming a glassy matrix upon drying
Immobilizes proteins and prevents aggregation
The failure appears first under high humidity is what
What is conjugate aggregation / color fade.
Moisture triggers rehydration → AuNP clustering.
How would oxidation affect gold color?
What is causing darkening or signal loss.
Oxidized AuNPs scatter less light.
Over-blocking reduce sensitivity by
Excess BSA / casein masks binding domains.
What occurs when buffer pH drifts over time?
What is Protein denaturation or loss of binding activity
Describe the mechanism of thermal denaturation.
What is heat unfolds antibody secondary / tertiary structure.
Loss of affinity → weak or absent signal.
Using Arrhenius, 13 days @ 37 °C ≈ how many @ 5 °C
What is ~8 months (Q₁₀ ≈ 2.5)
The root cause & fix for pH-induced aggregation
Give me the cause and fix
What is Cause: buffer drift; Fix: stronger buffering / adjust pH to 8.5.
Prevents charge collapse on AuNP surface.