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Protein Modification Reagents
Protein modification reagents are chemical agents used to modify amino acid side chains to alter the native charges, block or expose reactive binding sites, inactivate functional groups, or change functional groups to create targets for crosslinking and labeling. Various reagents are available to meet your protein modification strategy. Additionally, we offer activated linear and branched derivatives of polyethylene glycol (PEG) reagents for PEGylation and PEG-modification of peptides and proteins.
What is protein modification?
Modification of proteins or other biomolecules is often required before direct conjugation with a crosslinker or labeling reagent. Types of protein modification reagents include blocking specific amino acids, creating heterobifunctional crosslinkers, immobilization by crosslinking, and PEGylating proteins. Protein modifications can block amino acids reversibly or irreversibly regulating protein structure and function by inhibiting the interaction of a specific functional group. Protein modifications can also create heterobifunctional crosslinkers by modifying functional groups (i.e., amine group) by attaching another functional group (i.e., sulfhydryl-containing group) which subsequently are used for protein crosslinking. Additionally, PEGylation reagents are available for protein modification and are typically used to increase solubility, prolong stability, and reduce immunogenicity.
Selection guide for protein modification
| Chemical reactivity | Order products | Function | Reversible |
|---|---|---|---|
| Amine | Sulfo-NHS-Acetate | Amine-reactive (NHS ester) compound to permanently block primary amines (e.g., protein lysine side chains) to prevent interactions or later conjugation | No |
| Sulfhydryl | NEM (N-Ethylmalemide) | Small, sulfhydryl-reactive (maleimide) compound to permanently block the reduced cysteines of proteins or peptides to prevent disulfide bond formation | No |
| MMTS (methyl methanethiosulfonate) | Reversibly block cysteines (sulfhydryl groups) to help facilitate the study of enzyme activation and protein function | Yes | |
| IAA (Iodoacetic acid) | Used to S-carboxymethylate sulfhydryls (reduced cysteines) at slightly alkaline pH for use in various protein biology methods | No | |
| Iodoacetamide, No-Weigh Format | Sulfhydryl-reactive alkylating reagent used to block reduced cysteine residues for protein characterization and peptide mapping. Alkylation after cystine reduction results in the covalent addition of a carbamidomethyl group (57.07 Da) and prevents the formation of disulfide bonds | No | |
| Chloroacetamide, No-Weigh Format | Sulfhydryl-reactive alkylating reagent used to block reduced cysteine residues for protein characterization. Alkylation with chloroacetamide after cysteine reduction results in the covalent addition of a carbamidomethyl group (57.07 Da) and prevents the formation of disulfide bonds | No |
| Chemical reactivity | Products | Function | Spacer arm (Å) |
|---|---|---|---|
| Amine | SATP | Short (4.1A), amine-reactive (NHS ester) sulfhydryl-addition reagent; creates stable (protected yet exposable) -SH group for protein crosslinking strategies. | 4.1 |
| SAT(PEG)4 | Long (18.2A), PEGylated form of SATA, an amine-reactive (NHS ester) sulfhydryl-addition reagent; contains 4-unit polyethylene glycol spacer arm. | 18.2 | |
| SATA | SATA is a short-chain (2.8 angstrom spacer arm) reagent for covalent modification of primary amines and addition of a protected yet exposable sulfhydryl group, enabling heterobifunctional crosslinking strategies. | 2.8 | |
| SATA Sulfhydryl Addition Kit | A complete kit with SATA reagent and hydroxylamine to modify protein primary amines to create free sulfhydryl groups for crosslinking techniques. | 2.8 | |
| Traut's Reagent | 2-Iminothiolane-HCl (CAS 4781-83-3) is an amine-reactive thiolation reagent to cap protein primary amines with sulfhydryl groups for immediate crosslinking. | 8.1 |
Click image to enlarge
Reaction and modification scheme for NHS-activated S-acetyl reagents. A stable, covalent amide bond is formed from the reaction of the NHS ester with primary amines, with N-hydroxysuccinimide being released as a by-product. Hydroxylamine deprotection (deacylation) generates a sulfhydryl for use in cross-linking and other applications.
Click image to enlarge
Reaction scheme of Traut's Reagent (2-iminothiolane). A cyclic thioimidate compound, Traut’s reagent, reacts with primary amines to add sulfhydryl (-SH) groups for use in labeling, crosslinking and immobilization procedures.
| Order products | Function |
|---|---|
| APTS | Silylation reagent for coating glass and silica surfaces to add primary amines, which can be used to crosslink and immobilize proteins and other molecules |
| NaIO4 | Gently oxidize glycoprotein carbohydrate sugars to create reactive aldehydes (carbonyls) for crosslinking and immobilization |
| GlycoLink Coupling Catalyst | Two component kit with aniline and sodium acetate buffer to enhance aldehyde-hydrazide crosslinking efficiency for glycoprotein immobilization and conjugation |
Reaction of 3-aminopropyltriethoxysilane with glass surface. Derivatize and coat glass surfaces with a silane containing an amino group. Numerous crosslinking agents can be used to immobilize proteins or other molecules to the surface.
Click image to enlarge
Reaction of GlycoLink Coupling Catalyst. Labeling of oxidized glycoprotein and a hydrazide functional group.
| Reactive Chemistry/ Group | Products | Spacer Arm (Å) | Pegylation application |
|---|---|---|---|
| Amine-reactive (NHS) | MS(PEG)4 | 16.4Å | Protein or surface, terminating with a methyl group |
| MS(PEG)8 | 30.8Å | ||
| MS(PEG)12 | 44.9Å | ||
| MS(PEG)24 | 88.2Å | ||
| TMS(PEG)12 | 77.5Å | ||
| Sulfhydryl-reactive (Maleimide) | MM(PEG)12 | 51.9Å | Protein or surface (branched), terminating with a methyl group |
| MM(PEG)24 | 95.3Å | ||
| Carboxy-PEG-amine (Amine or carboxylic acid) | CA(PEG)4 | 18.1Å | Protein or surface, terminating with a carboxylic acid or primary amine |
| CA(PEG)8 | 33.6Å | ||
| CA(PEG)12 | 46.8Å | ||
| CA(PEG)24 | 89.8Å | ||
| Carboxy-PEG-lipoamide (Bidentate thiol) | CL(PEG)12 | 56Å | Gold or metal surface, terminating with a methyl group |
| Carboxy-PEG-thiol (Carboxylic acid or thiol) | CT(PEG)12 | 47.8Å | Gold or metal surface, terminating with a carboxylic acid |
| Methyl-PEG-amine (Amine) | MA(PEG)4 | 15.5Å | Protein, oxidized carbohydrate or surface, terminating with a methyl group |
| MA(PEG)8 | 29.7Å | ||
| MA(PEG)12 | 43.9Å | ||
| MA(PEG)24 | 86.1Å | ||
| Methyl-PEG-lipoamide (Bidentate thiol) | ML(PEG)4 | 23.6Å | Gold or metal surface, terminating with a methyl group |
| Methyl-PEG-thiol (Thiol) | MT(PEG)4 | 15.8Å | Protein or inert material surface, terminating with a methyl group |
| Chemical reactivity | Order products | Function | Reversible |
|---|---|---|---|
| Amine | Sulfo-NHS-Acetate | Amine-reactive (NHS ester) compound to permanently block primary amines (e.g., protein lysine side chains) to prevent interactions or later conjugation | No |
| Sulfhydryl | NEM (N-Ethylmalemide) | Small, sulfhydryl-reactive (maleimide) compound to permanently block the reduced cysteines of proteins or peptides to prevent disulfide bond formation | No |
| MMTS (methyl methanethiosulfonate) | Reversibly block cysteines (sulfhydryl groups) to help facilitate the study of enzyme activation and protein function | Yes | |
| IAA (Iodoacetic acid) | Used to S-carboxymethylate sulfhydryls (reduced cysteines) at slightly alkaline pH for use in various protein biology methods | No | |
| Iodoacetamide, No-Weigh Format | Sulfhydryl-reactive alkylating reagent used to block reduced cysteine residues for protein characterization and peptide mapping. Alkylation after cystine reduction results in the covalent addition of a carbamidomethyl group (57.07 Da) and prevents the formation of disulfide bonds | No | |
| Chloroacetamide, No-Weigh Format | Sulfhydryl-reactive alkylating reagent used to block reduced cysteine residues for protein characterization. Alkylation with chloroacetamide after cysteine reduction results in the covalent addition of a carbamidomethyl group (57.07 Da) and prevents the formation of disulfide bonds | No |
| Chemical reactivity | Products | Function | Spacer arm (Å) |
|---|---|---|---|
| Amine | SATP | Short (4.1A), amine-reactive (NHS ester) sulfhydryl-addition reagent; creates stable (protected yet exposable) -SH group for protein crosslinking strategies. | 4.1 |
| SAT(PEG)4 | Long (18.2A), PEGylated form of SATA, an amine-reactive (NHS ester) sulfhydryl-addition reagent; contains 4-unit polyethylene glycol spacer arm. | 18.2 | |
| SATA | SATA is a short-chain (2.8 angstrom spacer arm) reagent for covalent modification of primary amines and addition of a protected yet exposable sulfhydryl group, enabling heterobifunctional crosslinking strategies. | 2.8 | |
| SATA Sulfhydryl Addition Kit | A complete kit with SATA reagent and hydroxylamine to modify protein primary amines to create free sulfhydryl groups for crosslinking techniques. | 2.8 | |
| Traut's Reagent | 2-Iminothiolane-HCl (CAS 4781-83-3) is an amine-reactive thiolation reagent to cap protein primary amines with sulfhydryl groups for immediate crosslinking. | 8.1 |
Click image to enlarge
Reaction and modification scheme for NHS-activated S-acetyl reagents. A stable, covalent amide bond is formed from the reaction of the NHS ester with primary amines, with N-hydroxysuccinimide being released as a by-product. Hydroxylamine deprotection (deacylation) generates a sulfhydryl for use in cross-linking and other applications.
Click image to enlarge
Reaction scheme of Traut's Reagent (2-iminothiolane). A cyclic thioimidate compound, Traut’s reagent, reacts with primary amines to add sulfhydryl (-SH) groups for use in labeling, crosslinking and immobilization procedures.
| Order products | Function |
|---|---|
| APTS | Silylation reagent for coating glass and silica surfaces to add primary amines, which can be used to crosslink and immobilize proteins and other molecules |
| NaIO4 | Gently oxidize glycoprotein carbohydrate sugars to create reactive aldehydes (carbonyls) for crosslinking and immobilization |
| GlycoLink Coupling Catalyst | Two component kit with aniline and sodium acetate buffer to enhance aldehyde-hydrazide crosslinking efficiency for glycoprotein immobilization and conjugation |
Reaction of 3-aminopropyltriethoxysilane with glass surface. Derivatize and coat glass surfaces with a silane containing an amino group. Numerous crosslinking agents can be used to immobilize proteins or other molecules to the surface.
Click image to enlarge
Reaction of GlycoLink Coupling Catalyst. Labeling of oxidized glycoprotein and a hydrazide functional group.
| Reactive Chemistry/ Group | Products | Spacer Arm (Å) | Pegylation application |
|---|---|---|---|
| Amine-reactive (NHS) | MS(PEG)4 | 16.4Å | Protein or surface, terminating with a methyl group |
| MS(PEG)8 | 30.8Å | ||
| MS(PEG)12 | 44.9Å | ||
| MS(PEG)24 | 88.2Å | ||
| TMS(PEG)12 | 77.5Å | ||
| Sulfhydryl-reactive (Maleimide) | MM(PEG)12 | 51.9Å | Protein or surface (branched), terminating with a methyl group |
| MM(PEG)24 | 95.3Å | ||
| Carboxy-PEG-amine (Amine or carboxylic acid) | CA(PEG)4 | 18.1Å | Protein or surface, terminating with a carboxylic acid or primary amine |
| CA(PEG)8 | 33.6Å | ||
| CA(PEG)12 | 46.8Å | ||
| CA(PEG)24 | 89.8Å | ||
| Carboxy-PEG-lipoamide (Bidentate thiol) | CL(PEG)12 | 56Å | Gold or metal surface, terminating with a methyl group |
| Carboxy-PEG-thiol (Carboxylic acid or thiol) | CT(PEG)12 | 47.8Å | Gold or metal surface, terminating with a carboxylic acid |
| Methyl-PEG-amine (Amine) | MA(PEG)4 | 15.5Å | Protein, oxidized carbohydrate or surface, terminating with a methyl group |
| MA(PEG)8 | 29.7Å | ||
| MA(PEG)12 | 43.9Å | ||
| MA(PEG)24 | 86.1Å | ||
| Methyl-PEG-lipoamide (Bidentate thiol) | ML(PEG)4 | 23.6Å | Gold or metal surface, terminating with a methyl group |
| Methyl-PEG-thiol (Thiol) | MT(PEG)4 | 15.8Å | Protein or inert material surface, terminating with a methyl group |
Free download
Bioconjugation and crosslinking technical handbook
Everything you need to bioconjugate, crosslink, biotinylate, and modify proteins and peptides.
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Need larger quantities of our protein labeling, crosslinking or modification reagents? We offer bulk and custom fill sizes.
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