Polyethylene glycol (PEG) FAQs

Answers to your frequently asked questions on PEG.

For additional information, please contact our scientific support to learn more.


Detecting different forms of PEG


PEG ELISA kit (ab215546)


What is PEG?

PEG is the common abbreviation for polyethylene glycol – or, more properly, poly (ethylene glycol) – which refers to a chemical compound composed of repeating ethylene glycol units. PEG is an O-CH2-CH2 polymer, which is water-soluble, non-toxic, non-antigenic, and biocompatible. Purified PEG is most defined by their molecular weight (MW) ranges.

For example, PEG600 is PEG polymer with MW of 600.

PEG 10K or PEG 10,000 denotes a mixture of PEG molecules (about 195-265 PEG molecules) having an average MW of 10,000 g/mol.

PEG has several chemical properties that make it especially useful in various biological, chemical and pharmaceutical settings:

  • Non-toxic and non-immunogenic – can be added to media and attached to surfaces and conjugated to molecules without interfering with cellular functions or target immunogenicities
  • Hydrophilic (aqueous-soluble) – attachment to proteins and other biomolecules decreases aggregation and increases solubility
  • Highly flexible – provides for surface treatment or bioconjugation without steric hindrance

Due to these unique properties, PEG is commonly used to PEGlyate various protein and drug molecules (1).

Why would I use an anti-PEG antibody?

An anti-PEG antibody can be used to monitor a drug’s pharmacokinetics, including distribution, metabolism, and excretion. It can also be used for the quality control of PEGylated proteins or molecules, such as nanoparticles. Our antibodies are suitable for use in ELISA, WB, and IHC.

What PEG products are available? What is their binding specificity (e.g. PEG chain length)?

We offer various PEG antibodies as well as kits for the detection of PEG, including our high-affinity rabbit monoclonal PEG antibodies:

Anti-Polyethylene glycol antibody [PEG-B-47] (ab51257)
- Recognises the PEG terminal methoxy group.
- Recognises PEG from 750 - 40,000 Da.
- Made up of rabbit IgG.

Anti-Polyethylene glycol antibody [PEG-B-47b] (Biotin) (ab53449)
- Recognises the PEG terminal methoxy group.
- ab51257 and ab53449 are the same clones (PEG-b-47). ab53449 is the biotinylated version of ab51257.
- ab53449 is purified before biotinylation. Protein A was used to purify this antibody.

Anti-Polyethylene glycol antibody [PEG-2-128] ( ab133471
- PEG backbone-specific.
- Recognises PEG from 5000 - 40,000 Da.
- Made up of rabbit IgM.

PEG ELISA Kit (ab215546)
- Competitive quantitative ELISA kit.
- ab51257 is also used in the PEG ELISA kit (ab215546) as the capture antibody.

What are the smallest and largest PEG molecules your antibodies can detect?

Smallest detected - PEG 750
Largest detected - PEG 40K

Which PEG products do you recommend for detecting linear PEG and branched PEG?

ab51257 and ab53449 detect both linear and branched PEG based on our in-house ELISA results.

ab51257 is also used in the PEG ELISA kit (ab215546) as the capture antibody and therefore detects both linear and branched PEG.

What antibodies would you recommend to detect the PEG backbone?

ab133471 is specific to the backbone of the PEG molecule and is made up of rabbit monoclonal IgM. In contrast, ab51257 is specific to the terminal methoxy group of the PEG molecule and is made up of rabbit  IgG.

Which PEG antibodies do you recommend when detecting the free (unconjugated) form of PEG?

Since free PEG and conjugated PEG have different MW, these two forms can be distinguished by western blot using the anti-PEG (backbone-specific) antibody, ab133471.

As ab133471 recognizes the PEG backbone, PEG is not required to be bound to other molecules. We have direct ELISA data using PEG5K, 6K, 20K to confirm this.

Our RabMAb PEG ELISA kit (ab215546) cannot be used in detecting free PEG.

Will your PEG antibodies work on my sample? Such as mouse and rat tissue?

If there is a PEG molecule present, our anti-PEG antibodies will detect the PEGylated molecule. Our PEG products are independent of sample or species used.

What is the recommended IHC protocol for use with a PEG antibody?

We recommend our standard IHC protocol, with a dilution factor or 1:50 - 1:100.

What is the volume of PEG antibody per vial?

Our RabMAb PEG antibodies are provided as 100 ug, so you can calculate the volume using the following calculation:

(0.1mg) divided by the current concentration of antibody (mg/ml)
= volume (ml)

How do I calculate PEG size using "N"?

The numbers that are often included in the names of PEGs indicate their average molecular weights, e.g. a PEG with n=9 would have an average molecular weight of approximately 400 daltons and would be labeled PEG 400. Most PEGs include molecules with a distribution of molecular weights; i.e. they are polydisperse.

Therefore, N/Daltons is 9/400.  You can use this ratio to figure out either N or size in Dalton as long as you have either N or Dalton value.

What kind of buffer should be used to dilute my sample when using the PEG ELISA kit (ab215546)?

Use antigen/antibody diluent buffer in the kit. Any PBS-based buffer with BSA and/or Tween can be used.

What type of detection does the PEG ELISA kit (ab215546) use?

The PEG ELISA kit (ab215546) operates on the basis of competition between the enzyme (HRP) conjugated PEG and PEG labeled molecules for a limited number of binding sites on the surface of 96-wells coated with anti-PEG antibody.

The extent of color development resulted from the interaction between HRP and substrate TMB is inversely proportional to the amount of PEGylated molecules in the sample.

Is the PEG ELISA kit (ab215546) reactive with fluorocarbons containing PEG?

We have not tested fluorocarbons containing PEG so we do not know for certain. However, we tested H2N-PEG6000-OCH3 using the kit and it did not compete with HRP-PEG.

Can the PEG backbone-specific antibody (ab133471) be used with the PEG ELISA kit (ab215546)?

ab133471 cannot be used with our PEG ELISA kit.

Is the PEG BSA reference sample provided in the PEG ELISA kit (ab215546) a single PEG conjugated to BSA, or a PEG polymer conjugated to the BSA?

The PEG BSA reference sample in this kit has about 5 moles of PEG5K conjugated to 1 mole of BSA.