The Quant-iT (Qubit) protein assay provides rapid, sensitive quantification of total protein using a fluorescence dye with minimal interference from common buffers. We use it for quick expression titer estimates in crude lysates and purified samples.

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How It Works

A protein-selective fluorescent dye binds to proteins with high specificity. After mixing sample with working reagent and incubating briefly, fluorescence is measured on a fluorometer and converted to concentration using a standard curve. Signal is proportional to protein mass within the kit’s linear dynamic range.

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Applications

Rapid Titer Estimation

Fast quantification of expression levels across constructs and conditions.

Low-Abundance Detection

Higher sensitivity and specificity than colorimetric assays in many buffers.

Crude Lysate Compatibility

Tolerates typical expression buffers; simple workflows and small volumes.

Calibration to Purified Standard

Improves accuracy by matching dye response to the target protein class.

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Performance & Notes

  • Linear dynamic ranges depend on kit (e.g., HS vs BR); choose to match expected titer.
  • Minimal interference versus Bradford/BCA; some detergents/chaotropes still affect signal.
  • Requires standard curve each run; protein-to-dye response can vary across protein classes.

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Integration

Quant-iT complements split-GFP and CE by enabling rapid, sensitive total-protein quantification to triage expression conditions before detailed purity/heterogeneity analyses.