Polyethylene glycol (PEG) FAQs

Answers to your most frequently asked questions about our RabMAb® PEG products.

For additional information, please submit an inquiry or contact
our scientific support 
to learn more.


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 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 use an anti-PEG antibody?

An Anti-PEG antibody can be used to monitor a drug’s pharmacokinetics, including distribution, metabolism, and excretion. Also, it can be used for the quality control of pegylated molecules in ELISA, WB, and IHC.

What type of RabMAB PEG products are available from Abcam?

We offer various PEG antibodies and kits for PEG detection, including our high-quality rabbit monoclonal PEG antibodies.

For PEG antibody to PEG methoxy group, please see Anti-Polyethylene glycol antibody [PEG-B-47] (ab51257).
For PEG antibody to PEG methoxy group, conjugated to Biotin, please see Anti-Polyethylene glycol antibody [PEG-B-47b] (Biotin) (ab53449).
For PEG antibody to PEG backbone, please see Anti-Polyethylene glycol antibody [PEG-2-128] (  ab133471)

For PEG ELISA kit, please see PEG ELISA Kit (ab215546).

Which PEG antibody do you recommend in detecting linear PEG? When detecting branched PEG?

Ab51257 and ab53449 both detect linear and branched PEG (based on our in-house ELISA results).

Can PEG ELISA kit (ab138914) be used with both linear and branched PEG?

Yes, ab51257 is used in the kit as the capture antibody in the kit and it has been shown to detect both linear and branched PEG.

What is the difference between ab51257 and ab53449?

Ab51257 and ab53449 are the same clones (PEG-b-47). Ab53449 is a biotinlyated version of ab51257.

Is ab53449 purified?

Yes, ab53449 is purified before biotinylation. Protein A was used to purify this antibody.

What is the difference between ab51257 and ab133471?

Ab51257 is specific to the terminal of PEG molecule and is made up of rabbit  IgG. In contrast, ab133471 is specific to the backbone of the PEG molecule and is made up of rabbit monoclonal IgM.

Will your PEG antibodies work on my sample?

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

Will your PEG antibodies work on mouse and rat?

It works in all species as long as a PEG molecule is present.

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 smallest PEG molecule your PEG antibodies can detect? What is the largest PEG molecule your PEG antibodies can detect?

What is the smallest PEG molecule your PEG antibodies can detect? What is the largest PEG molecule your PEG antibodies can detect?

  • Smallest detected - PEG 750
  • Largest detected - PEG 40K

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

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

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

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

What is the volume of PEG antibody per vial?

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

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

What kind of buffer should be used to dilute my sample when using the PEG ELISA kit (ab138914)?

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 (ab138914) 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 (ab138914) 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 antibody (ab133471) be used with the PEG ELISA kit (ab138914)?

Ab133471 cannot be used with our PEG ELISA kit.

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.

Is the PEG BSA a single PEG conjugated to BSA, or a PEG polymer conjugated to the BSA?

About 5 moles of PEG5K are conjugated to 1 mole of BSA.

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