Question 1

How is mass transport limitation detected and avoided?

Accepted Answer

If the measured on-rate falls as loading density rises, transport rather than binding is limiting the signal. Running the same analyte at two or three loading levels, and at different agitation speeds, reveals the effect. Working at the lowest density that still gives usable signal keeps the measurement in the kinetically controlled region.

Question 2

Which references must be subtracted before fitting?

Accepted Answer

Two are standard: a sensor prepared identically but without ligand, which reports non-specific binding of analyte to the surface, and a ligand-loaded sensor exposed to buffer alone, which reports baseline drift and any ligand loss. Double referencing with both is expected practice, and omitting either can produce apparent binding that is entirely artefact.

Question 3

How should a kinetic model be justified?

Accepted Answer

More complex models fit better by construction, so improved residuals alone justify nothing. A one-to-one model should be the default unless there is an independent reason, such as known avidity or conformational change, to expect otherwise. Global fitting across a concentration series, with consistent parameters between sensors, is the practical test.

Question 4

What concentration range should the analyte series cover?

Accepted Answer

A series spanning roughly a tenfold range either side of the expected equilibrium constant, in at least five steps, constrains both rate constants properly. Fitting a single concentration cannot separate association from dissociation reliably. A zero-analyte injection within the series provides an internal control for the fit.

Question 5

How is regeneration validated?

Accepted Answer

After each regeneration cycle, a repeat injection at the same analyte concentration should give the same response amplitude and kinetics. Progressive loss indicates the ligand is being damaged, and results from later cycles are then unreliable. Where no gentle condition works, single-use sensors are preferable to a compromised regeneration protocol.

Question 6

How are thermodynamic parameters obtained from this method?

Accepted Answer

Repeating the kinetic measurement across a temperature series and applying transition state analysis to the rate constants yields activation and binding thermodynamics. Baseline stability degrades with temperature changes, so equilibration time at each setting must be generous and drift documented, otherwise the extracted values carry more uncertainty than reported.

Biotechnology

Biotechnology

Research Frontiers in Biolayer Interferometry Kinetics Measurement