Antibodies, conjugates and markers: how can specific targeting and a detectable signal be achieved?

At the heart of immunoassays and imaging, antibodies, conjugates and labels turn a biological target into a measurable signal. Primary and secondary antibodies, enzyme systems (HRP, AP), high-brightness fluorescent dyes, the biotin–streptavidin pair, protein markers for electrophoresis, biotinylation and conjugation reagents… all tools for the detection, quantification and localisation of proteins, tags and small molecules in Western blotting, ELISA, IHC/ICC, flow cytometry or microscopy. Dutscher guides you to the best-performing combination for your instrument and sample matrix.

Which types are available, and how do you choose the right one for your application?

• Primary antibodies: monoclonal, polyclonal or recombinant, they recognise the epitope of interest. Selection is based on the host species, clonality, isotype, application validation (WB, IHC, IF, FC) and fixation/denaturation compatibility.

• Secondary antibodies: raised against the primary’s species, often conjugated to HRP/AP or fluorophores (CF). F(ab’)2 formats limit background; cross-adsorbed versions reduce cross-reactivity in multiplex assays.

• Anti-tag antibodies & streptavidin: standardised detection of tags (His, HA, Myc, GFP). The streptavidin–biotin pair offers exceptional affinity for signal amplification in ELISA, IHC and blots.

• Protein markers: molecular weight standards, coloured or fluorescent, for SDS-PAGE and Western, streamlining migration, transfer and calibration.

• Fluorescent labels and labelling reagents: NHS esters (amines), maleimides (thiols), click chemistry (azide/alkyne) to conjugate antibodies, proteins or small molecules, with control over the degree of labelling (F/P) and photostability.

• Biotinylation reagents: NHS-biotin with spacers, site-specific variants to preserve affinity. Ideal for avidin/streptavidin platforms and magnetic capture.

• Small molecules and other conjugates: fluorescent proteins (GFP, mCherry) for expression, labelled nucleotides for probes and qPCR, haptens and tracers for cell tracking.

Selection criteria: target and species, application, type of conjugation (HRP/AP, fluorophore, biotin), instrument compatibility (lasers 405/488/561/640 nm, channels), management of background and spectral overlap, stability (light protection, azide), and quality considerations (lot-to-lot, traceability, animal-free options for sustainability).

Quick comparison table

Type	Principle	Applications
Primary antibodies	Specific epitope binding	WB, IHC/ICC, IF, FC
Conjugated secondaries	Anti-species + enzyme/fluorophore	Signal amplification, multiplexing
Anti-tag & streptavidin	Tag or biotin recognition	ELISA, purification, imaging
Labelling reagents	NHS, maleimide, click	Custom conjugation
Protein markers	Coloured/fluorescent MW standards	SDS-PAGE, Western

In which application areas are these antibodies, conjugates and markers used?

• Life sciences: protein mapping, biomarker validation, confocal and super-resolution imaging, cell sorting by flow cytometry.
• Pharma/biotech: therapeutic antibody characterisation, host-cell protein (HCP) monitoring, ELISA for batch-release testing.
• Food & beverage: detection of allergens and pathogens using rapid immunoassays and ELISA.
• Environmental: monitoring of toxins, cyanobacteria and biological contaminants.
• Cosmetics: evaluation of actives on cell lines; multiplex labelling for signalling pathways.
• Chemistry/analytical: custom conjugations, fluorescent probes and biotinylation for targeted capture and enrichment.

Available sub-categories of antibodies, conjugates and markers

Primary antibody

Frequently asked questions about antibodies, conjugates and markers

How do I choose a reliable primary antibody?
Check host species, clonality, isotype, application-specific validation datasheets, representative data images and literature citations. Favour traceable, recombinant batches.

HRP or AP for detection?
HRP is fast and highly sensitive; AP tolerates inhibitors better and gives low background for prolonged blots. Choose based on substrate, incubation time and sample/membrane matrix.

Which fluorophore suits my instrument?
Match excitation to the lasers (405/488/561/640 nm), maximise brightness and photostability, and minimise spectral overlap in multiplex panels.

What is F/P (degree of labelling)?
It is the number of fluorophores per IgG. An appropriate F/P optimises signal without quenching or loss of affinity. Avoid over-labelling.

Is azide compatible?
NaN3 inhibits HRP and is unsuitable for live cells. Use azide-free formulations for HRP, flow cytometry or conjugations.

How can I reduce cross-reactivity of secondary antibodies?
Choose highly cross-adsorbed secondaries matched to the primary’s host species, and favour F(ab’)2 fragments in complex tissues.

Same antibody for WB and IF?
Sometimes yes, but check application validation. Denaturation (WB) or fixation (IF/IHC) can mask the epitope; adjust the protocol.

Good storage practices?
Store at 2–8 °C or with glycerol at -20 °C, avoid freeze–thaw cycles, protect fluorophores from light, and observe expiry dates.