Streptavidin Quantum Dots

What it means: Quantum Dots (QDs) are semiconductor nanocrystals (typically 2–10 nm core diameter) whose optical emission wavelength is determined by particle size — smaller dots emit at shorter (bluer) wavelengths, larger dots at longer (redder) wavelengths. This "size-tunable" emission is a unique property not shared by organic fluorophores.

Why it matters:

• Far superior photostability compared to organic dyes — enabling long time-lapse imaging and repetitive scanning.
• Narrow emission peaks (FWHM < 35 nm) reduce spectral crosstalk in multiplexed detection panels.
• Multiple QD colors can be excited simultaneously from a single UV or blue light source.
• High molar extinction coefficient gives bright signal per molecule.

How to interpret here: This product is a Quantum Dot format. The emission wavelength value shown is the peak output wavelength — select it to match your detector filter/laser combination. All wavelengths can be excited together for multiplexed assay panels.

Tip: QDs are larger than organic dye molecules (~10–20 nm total diameter with coating). This may affect steric accessibility in some applications — test at pilot scale before full assay build-out.

What it means: Streptavidin is a tetrameric protein that binds biotin with one of the highest known non-covalent affinities in biology (Kd ≈ 10⁻¹⁵ M). Streptavidin is covalently coupled to the particle surface, making most of the four biotin-binding sites sterically available.

Why it matters:

• Captures any biotinylated molecule — antibodies, nucleic acids, peptides, small molecules, and ligands — without additional coupling reagents.
• Essentially irreversible binding under physiological conditions supports stable complex formation across washes.
• Covalent coupling prevents streptavidin leaching, ensuring consistent biotin-binding activity.
• Low non-specific binding surface reduces background in immunoassay and flow cytometry applications.

How to interpret here: This product has Streptavidin surface chemistry — it is pre-conjugated and ready to capture biotinylated targets directly. No additional activation is needed. Simply mix with your biotinylated ligand and magnetically separate.

Tip: The biotin–streptavidin bond is essentially irreversible at physiological pH. If you need reversible biotin capture (e.g., for elution), consider monomeric avidin or nitrated streptavidin variants with reduced affinity.

What it means: Emission Wavelength is the peak fluorescence output of the quantum dot. Available wavelengths: 425 nm–620 nm.

Why it matters:

• Each wavelength corresponds to a specific detector filter/laser channel in your instrument.
• Multiple QD wavelengths can be detected simultaneously with a single UV or blue excitation source — enabling multiplexed panels.
• All wavelengths from 425 nm–620 nm are available as individual products and as a combo pack.
• Narrow emission peaks (FWHM < 35 nm) minimize spectral crosstalk between detection channels.

How to interpret here: Select the emission wavelength that matches your available detector filter set. For multiplex assays, select one wavelength per detection channel. The full range 425 nm–620 nm can be combined in the same experiment with a single excitation source.

Tip: Always verify the exact filter transmittance of your instrument to confirm the selected wavelength is centered within the bandpass. A slight mismatch can reduce signal intensity significantly.

What it means: Pre-conjugated means the binding ligand (streptavidin, Protein G, or another affinity ligand) has already been covalently coupled to the particle surface during manufacturing. No additional conjugation step is needed before use in your assay.

Why it matters:

• Ready-to-use for target capture immediately after resuspension — fastest path to assay results.
• Covalent ligand attachment prevents leaching or dissociation under assay conditions.
• Quality-controlled coupling ensures consistent binding capacity lot-to-lot.
• Saves time and reduces protocol variability compared to performing your own coupling.

How to interpret here: This product is Pre-conjugated. Simply resuspend (bath sonication recommended) and use directly in your capture protocol. No EDC, NHS, or crosslinker is needed. Confirm working concentration in your specific assay format.

Tip: Store at 2–8°C without freezing. Binding activity can be verified by a simple pull-down test using a known amount of biotinylated or IgG target before committing to full assay development.

What it means: Aqueous dispersion means this product is supplied as a colloidal suspension in an aqueous buffer (typically PBS, DI water, or a proprietary storage buffer). The particles are dispersed and ready for use in water-based biological applications without any solvent exchange step.

Why it matters:

• Compatible directly with cell culture media, PBS, HEPES, and other standard biological buffers.
• No solvent exchange or phase transfer required before use in aqueous assay protocols.
• Aqueous colloidal stability maintained by surface coating (polymer, PEG, or functional group layer).
• Bath sonication before use ensures complete resuspension after storage sedimentation.

How to interpret here: This product is in Aqueous dispersion. It can be used directly in your assay buffer after resuspension. Confirm compatibility with your specific buffer conditions (ionic strength, pH, protein concentration) by checking the product specification sheet or running a small-scale stability test.

Tip: High ionic strength buffers (>500 mM) or pH extremes outside the specification range may compromise colloidal stability. Always validate in your specific matrix.

What it means: Applications list the primary experimental workflows this product has been used for: Immunoassay, Nucleic Acid Isolation, Cell Separation, Immunoprecipitation.

Why it matters:

• Immunoassay: this product can directly support this workflow based on its surface chemistry and particle properties.
• Nucleic Acid Isolation: this product can directly support this workflow based on its surface chemistry and particle properties.
• Cell Separation: this product can directly support this workflow based on its surface chemistry and particle properties.

How to interpret here: This product is suited for the listed applications. The most relevant for this product are Immunoassay, Nucleic Acid Isolation. Review the application-specific protocol in the Documents section before beginning workflow development.

Tip: Application suitability depends on specific experimental conditions (buffer, sample matrix, target concentration). Always validate at pilot scale before full assay development.