BIS-PEG21-NHS ESTER is a very important heterogeneous bifunctional crosslinking agent in the fields of biocoupling chemistry and drug development. Its core value lies in its ability to simultaneously and step by step connect two different molecules (such as proteins, antibodies, polypeptides, small molecule drugs, nucleic acids, etc.) to achieve precise coupling.


The full English name is Bis-PEG21-NHS Ester

Molecular weight: approximately 1,056 Da (PEG part is about 924 Da)

The number of PEG units is 21

Functional Group 1 N-hydroxysuccinimide (NHS Ester)

Functional group 2 n-hydroxysuccinimide (NHS Ester)

Reactivity reacts with primary amino groups (-NH₂)

It appears as a white to off-white solid powder

Solubility: Readily soluble in DMSO and DMF, and soluble in water (but prone to hydrolysis in aqueous solution).

Storage conditions: Store at -20°C in a dry and dark place. Prevent deliquescence strictly. It is recommended to fill with nitrogen for protection.



⚙️ Core functions and mechanisms of action

BIS-PEG21-NHS ESTER is a homogeneous bifunctional crosslinker, but its long-chain PEG structure endows it with special uses. Its core function is:

Reaction with primary amino group:

Both NHS ester groups can react efficiently with the primary amino group (-NH₂) on biomolecules to form stable amide bonds.

These primary amino groups are widely present in:

Protein/Antibody: Side chains of Lysine residues.

Polypeptide: N-terminal amino or lysine side chain.

Nucleic acids with amino modifications (such as amino-modified DNA/RNA).

Amino groups on various small molecule drugs or compounds.

Introduce long PEG spacer arms:

This is its most crucial function. The 21-unit PEG chain provides a flexible long chain approximately 2.65 nanometers in length.

Function One: Overcome steric hindrance. When connecting two macromolecules (such as antibodies and enzymes), long-chain PEG can effectively overcome the spatial barrier between them and avoid mutual interference with activity due to the molecules being too close.

Function Two: Enhance water solubility and flexibility. The PEG chain greatly enhances the water solubility of the entire coupling product and, due to its flexibility, increases the conformational freedom of the molecule, which is conducive to maintaining biological activity.

Function Three: Reduce immunogenicity. PEG chains can shield certain antigenic epitopes on conjugates and reduce immunogenicity.

Main application fields

The application of BIS-PEG21-NHS ESTER is very specific and important:

Protein-protein crosslinking

It is used to link two different proteins, for example, to link enzymes with antibodies, to prepare detection reagents for immunoassays (such as ELISA).

Synthesis of antibody-drug conjugates (ADCs)

In ADC research and development, it can be used to link antibodies and small molecule toxins containing amino groups. Its long-chain PEG arms help maintain the solubility of the ADC and may affect its pharmacokinetic properties.

Peg-ylation modification

Although the typical peG-ylation reagent is mPEG-NHS (single-function), Bis-PEG-NHS can be used to introduce branched or network-like PEG layers on the surface of molecules such as proteins, which may achieve better shielding and stabilizing effects.

Construction of biosensors

Biometric molecules (such as antibodies, aptamers) are fixed at one end on the electrode or chip surface, while the other end is connected to reporter molecules (such as enzymes, fluorescent dyes) to construct a highly sensitive biosensing interface.

Functionalization of nanomaterials

Modify nanoparticles (such as gold nanoparticles and quantum dots), and simultaneously introduce two different functional molecules on their surfaces to achieve multifunctionalization.