Protein Crosslinking

Crosslinkers contain reactive ends to specific functional groups, such as primary amines and sulfhydryls on proteins and antibodies, enabling the covalent joining of or two or more biomolecules. Homobifunctional crosslinkers have the same reactive chemistry at both ends and heterobifunctional have different chemistries at each end. PEGylated crosslinkers have enhanced solubility, increased stability, reduced aggregation, and reduced immunogenicity. Use our crosslinker selection tool to find the optimal reagent for your protein function or interaction application, or access our helpful Bioconjugation Technical Handbook to help improve your crosslinking results.

Crosslinker Selection Tool

Learn more about crosslinking chemistries
Learn more about unreactive crosslinker and small molecule removal

Choose the right crosslinker based on reactive chemistry

Amine-to-amine
Sulfhydryl-to-sulfhydryl

Amine-to-amine

Reactive group	Order products	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane-permeable?	Reversible?
NHS ester	DSG	7.7	N/A	No	Yes	No
	DSS	11.4	N/A	No	Yes	No
	BS3	11.4	N/A	Yes	No	No
	TSAT (trifunctional)	4.2	N/A	No	No	No
	BS(PEG)5	21.7	N/A	Yes	No	No
	BS(PEG)9	35.8	N/A	Yes	No	No
	DSP	12.0	Thiols	No	Yes	No
	DTSSP	12.0	Thiols	Yes	No	No
	DST	6.4	Periodate	Yes	Yes	No
	BSOCOES	13.0	Base	No	Yes	No
	EGS	16.1	Hydoxylamine	No	Yes	Yes
	Sulfo-EGS	16.1	Hydoxylamine	Yes	No	Yes
Imidoester	DMA	8.6	N/A	Yes	Yes	Yes
	DMP	9.2	N/A	Yes	Yes	Yes
	DMS	11.0	N/A	Yes	Yes	Yes
	DTBP	11.9	Thiol	Yes	Yes	No
Difluoro	DFDNB	3.0	N/A	No	Yes	Yes

Sulfhydryl-to-sulfhydryl

Sulfhydryl -to-Sulfhydryl Crosslinkers	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
NHS-Haloacetyl Crosslinkers	SIA	1.5	N/A	No	Yes
	SBAP	6.2	N/A	No	Yes
	SIAB	10.6	N/A	No	Yes
	Sulfo-SIAB	10.6	N/A	Yes	No
NHS-Maleimide	AMAS	4.4	N/A	No	Yes
	BMPS	5.9	N/A	No	Yes
	GMBS	7.3	N/A	No	Yes
	Sulfo-GMBS	7.3	N/A	Yes	No
	MBS	7.3	N/A	No	Yes
	Sulfo-MBS	7.3	N/A	Yes	No
	SMCC	8.3	N/A	No	Yes
	Sulfo-SMCC	8.3	N/A	Yes	No
	EMCS	9.4	N/A	No	Yes
	Sulfo-EMCS	9.4	N/A	Yes	No
	SMPB	11.6	N/A	No	Yes
	Sulfo-SMPB	11.6	N/A	Yes	No
	SMPH	14.2	N/A	No	Yes
	LC-SMCC	16.2	N/A	No	Yes
	Sulfo-KMUS	16.3	N/A	No	Yes
NHS-Pyridyldithiol Crosslinkers	SPDP	6.8	Thiol	No	Yes
	LC-SPDP	15.7	Thiol	No	Yes
	Sulfo-LC-SPDP	15.7	Thiol	Yes	No
	SMPT	11.2	Thiol	No	Yes
	PEG4-SPDP	25.7	Thiol	Yes	No
	PEG12-SPDP	54.1	Thiol	Yes	No

Amine-to-sulfhydryl
Carboxyl-to-amine
Sulfhydryl-to-carboxyl
Photoreactive
Chemoselective and Bioorthogonal

Amine-to-sulfhydryl

Reactive group	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
NHS-Haloacetyl	SIA	1.5	N/A	No	Yes
	SBAP	6.2	N/A	No	Yes
	SIAB	10.6	N/A	No	Yes
	Sulfo-SIAB	10.6	N/A	Yes	No
NHS-Maleimide	AMAS	4.4	N/A	No	Yes
	BMPS	5.9	N/A	No	Yes
	GMBS	7.3	N/A	No	Yes
	Sulfo-GMBS	7.3	N/A	Yes	No
	MBS	7.3	N/A	No	Yes
	Sulfo-MBS	7.3	N/A	Yes	No
	SMCC	8.3	N/A	No	Yes
	Sulfo-SMCC	8.3	N/A	Yes	No
	EMCS	9.4	N/A	No	Yes
	Sulfo-EMCS	9.4	N/A	Yes	No
	SMPB	11.6	N/A	No	Yes
	Sulfo-SMPB	11.6	N/A	Yes	No
	SMPH	14.2	N/A	No	Yes
	LC-SMCC	16.2	N/A	No	Yes
	Sulfo-KMUS	16.3	N/A	No	Yes
NHS-Pyridyldithiol Crosslinkers	SPDP	6.8	Thiol	No	Yes
	LC-SPDP	15.7	Thiol	No	Yes
	Sulfo-LC-SPDP	15.7	Thiol	Yes	No
	SMPT	11.2	Thiol	No	Yes
	PEG4-SPDP	25.7	Thiol	Yes	No
	PEG12-SPDP	54.1	Thiol	Yes	No

Carboxyl-to-amine

Reactive group	Order product	Cleavable ?	Water-soluble?	Membrane permeable?
Carbodiimide / NHS ester	DCC	No	No	Yes
	EDC	No	Yes	No
	NHS	No	No	Yes
	Sulfo-NHS	No	Yes	No

Sulfhydryl-to-carboxyl

Reactive group	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
Maleimide / hydrazide	BMPH	8.1A Short	No	Yes	Yes
	EMCH	11.8A Mid	No	Yes	Yes
	MPBH	17.9A Long	No	No	Yes
	KMUH	19.0A Long	No	No	Yes
Pyridyldithiol / hydrazide	PDPH	9.2A Short	Thiols	Yes	Yes

Photoreactive

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble ?	Membrane permeable?
NHS ester/ aryl azide	ANB-NOS	7.7 Short	No	No	No
NHS ester/ aryl azide	Sulfo-SANPAH	18.2 Long	No	Yes	No
NHS ester/ diazirine	SDA	3.9 Short	No	No	Yes
	Sulfo-SDA	3.9 Short	No	Yes	No
	LC-SDA	12.5 Mid	No	No	Yes
	Sulfo-LC-SDA	12.5 Mid	No	Yes	No
	SDAD	13.5 Mid	Thiols	No	Yes
	Sulfo-SDAD	13.5 Mid	Thiols	Yes	No

Chemoselective and Bioorthogonal

Amine or Sulfhydryl to Azide

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble?	Membrane permeable?
TFP Ester/DBCO	TFP Ester-PEG4-DBCO	17.9	No	No	ND*
TFP Ester/DBCO	TFP Ester-PEG12-DBCO	46.3	No	No	ND*
Maleimide/DBCO	Maleimide-PEG4-DBCO	29.7	No	No	ND*

* Not determined

Amine or Sulfhydryl to Alkyne

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble?	Membrane permeable?
NHS ester/azide	NHS-Azide	2.5	No	No	ND*
NHS ester/azide	NHS-PEG4-Azide	18.9	No	No	ND*
Haloacetyl/azide	Iodoacetamide Azide	ND*	No	No	ND*

* Not determined

Heterobifunctional kits

Heterobifunctional kits

These kits contain everything needed conjugate and purify a protein with a reactive maleimide or DBCO label for reaction with a sulfhydryl or azide, respectively.

Reactive group	Order product	Spacer Arm (Å)	Labeling scale	Number of reactions	Labeled protein reactive towards
TFP Ester/DBCO	DBCO Protein Labeling Kit	17.9	0.1–0.5 mg	5	Azides
NHS-Maleimide	Maleimide Protein Labeling Kit	8.3	0.1–1 mg	5	Sulfhydryls

* Not determined

Homobifunctional

Amine-to-amine
Sulfhydryl-to-sulfhydryl

Amine-to-amine

Reactive group	Order products	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane-permeable?	Reversible?
NHS ester	DSG	7.7	N/A	No	Yes	No
	DSS	11.4	N/A	No	Yes	No
	BS3	11.4	N/A	Yes	No	No
	TSAT (trifunctional)	4.2	N/A	No	No	No
	BS(PEG)5	21.7	N/A	Yes	No	No
	BS(PEG)9	35.8	N/A	Yes	No	No
	DSP	12.0	Thiols	No	Yes	No
	DTSSP	12.0	Thiols	Yes	No	No
	DST	6.4	Periodate	Yes	Yes	No
	BSOCOES	13.0	Base	No	Yes	No
	EGS	16.1	Hydoxylamine	No	Yes	Yes
	Sulfo-EGS	16.1	Hydoxylamine	Yes	No	Yes
Imidoester	DMA	8.6	N/A	Yes	Yes	Yes
	DMP	9.2	N/A	Yes	Yes	Yes
	DMS	11.0	N/A	Yes	Yes	Yes
	DTBP	11.9	Thiol	Yes	Yes	No
Difluoro	DFDNB	3.0	N/A	No	Yes	Yes

Sulfhydryl-to-sulfhydryl

Sulfhydryl -to-Sulfhydryl Crosslinkers	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
NHS-Haloacetyl Crosslinkers	SIA	1.5	N/A	No	Yes
	SBAP	6.2	N/A	No	Yes
	SIAB	10.6	N/A	No	Yes
	Sulfo-SIAB	10.6	N/A	Yes	No
NHS-Maleimide	AMAS	4.4	N/A	No	Yes
	BMPS	5.9	N/A	No	Yes
	GMBS	7.3	N/A	No	Yes
	Sulfo-GMBS	7.3	N/A	Yes	No
	MBS	7.3	N/A	No	Yes
	Sulfo-MBS	7.3	N/A	Yes	No
	SMCC	8.3	N/A	No	Yes
	Sulfo-SMCC	8.3	N/A	Yes	No
	EMCS	9.4	N/A	No	Yes
	Sulfo-EMCS	9.4	N/A	Yes	No
	SMPB	11.6	N/A	No	Yes
	Sulfo-SMPB	11.6	N/A	Yes	No
	SMPH	14.2	N/A	No	Yes
	LC-SMCC	16.2	N/A	No	Yes
	Sulfo-KMUS	16.3	N/A	No	Yes
NHS-Pyridyldithiol Crosslinkers	SPDP	6.8	Thiol	No	Yes
	LC-SPDP	15.7	Thiol	No	Yes
	Sulfo-LC-SPDP	15.7	Thiol	Yes	No
	SMPT	11.2	Thiol	No	Yes
	PEG4-SPDP	25.7	Thiol	Yes	No
	PEG12-SPDP	54.1	Thiol	Yes	No

Heterobifunctional

Amine-to-sulfhydryl
Carboxyl-to-amine
Sulfhydryl-to-carboxyl
Photoreactive
Chemoselective and Bioorthogonal

Amine-to-sulfhydryl

Reactive group	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
NHS-Haloacetyl	SIA	1.5	N/A	No	Yes
	SBAP	6.2	N/A	No	Yes
	SIAB	10.6	N/A	No	Yes
	Sulfo-SIAB	10.6	N/A	Yes	No
NHS-Maleimide	AMAS	4.4	N/A	No	Yes
	BMPS	5.9	N/A	No	Yes
	GMBS	7.3	N/A	No	Yes
	Sulfo-GMBS	7.3	N/A	Yes	No
	MBS	7.3	N/A	No	Yes
	Sulfo-MBS	7.3	N/A	Yes	No
	SMCC	8.3	N/A	No	Yes
	Sulfo-SMCC	8.3	N/A	Yes	No
	EMCS	9.4	N/A	No	Yes
	Sulfo-EMCS	9.4	N/A	Yes	No
	SMPB	11.6	N/A	No	Yes
	Sulfo-SMPB	11.6	N/A	Yes	No
	SMPH	14.2	N/A	No	Yes
	LC-SMCC	16.2	N/A	No	Yes
	Sulfo-KMUS	16.3	N/A	No	Yes
NHS-Pyridyldithiol Crosslinkers	SPDP	6.8	Thiol	No	Yes
	LC-SPDP	15.7	Thiol	No	Yes
	Sulfo-LC-SPDP	15.7	Thiol	Yes	No
	SMPT	11.2	Thiol	No	Yes
	PEG4-SPDP	25.7	Thiol	Yes	No
	PEG12-SPDP	54.1	Thiol	Yes	No

Carboxyl-to-amine

Reactive group	Order product	Cleavable ?	Water-soluble?	Membrane permeable?
Carbodiimide / NHS ester	DCC	No	No	Yes
	EDC	No	Yes	No
	NHS	No	No	Yes
	Sulfo-NHS	No	Yes	No

Sulfhydryl-to-carboxyl

Reactive group	Order product	Spacer Arm (Å)	Cleavable?	Water-soluble?	Membrane permeable?
Maleimide / hydrazide	BMPH	8.1A Short	No	Yes	Yes
	EMCH	11.8A Mid	No	Yes	Yes
	MPBH	17.9A Long	No	No	Yes
	KMUH	19.0A Long	No	No	Yes
Pyridyldithiol / hydrazide	PDPH	9.2A Short	Thiols	Yes	Yes

Photoreactive

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble ?	Membrane permeable?
NHS ester/ aryl azide	ANB-NOS	7.7 Short	No	No	No
NHS ester/ aryl azide	Sulfo-SANPAH	18.2 Long	No	Yes	No
NHS ester/ diazirine	SDA	3.9 Short	No	No	Yes
	Sulfo-SDA	3.9 Short	No	Yes	No
	LC-SDA	12.5 Mid	No	No	Yes
	Sulfo-LC-SDA	12.5 Mid	No	Yes	No
	SDAD	13.5 Mid	Thiols	No	Yes
	Sulfo-SDAD	13.5 Mid	Thiols	Yes	No

Chemoselective and Bioorthogonal

Amine or Sulfhydryl to Azide

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble?	Membrane permeable?
TFP Ester/DBCO	TFP Ester-PEG4-DBCO	17.9	No	No	ND*
TFP Ester/DBCO	TFP Ester-PEG12-DBCO	46.3	No	No	ND*
Maleimide/DBCO	Maleimide-PEG4-DBCO	29.7	No	No	ND*

* Not determined

Amine or Sulfhydryl to Alkyne

Reactive group	Order product	Spacer Arm (Å)	Cleavable by?	Water-soluble?	Membrane permeable?
NHS ester/azide	NHS-Azide	2.5	No	No	ND*
NHS ester/azide	NHS-PEG4-Azide	18.9	No	No	ND*
Haloacetyl/azide	Iodoacetamide Azide	ND*	No	No	ND*

* Not determined

Heterobifunctional kits

Heterobifunctional kits

Heterobifunctional kits

These kits contain everything needed conjugate and purify a protein with a reactive maleimide or DBCO label for reaction with a sulfhydryl or azide, respectively.