Labeling Chemistry

Protein labeling reagents are used for various assays that are coupled with antigen-antibody reactions. Of these, fluorescent, biotin, and enzyme labeling reagents are used most frequently for antibody labeling. Most protein labeling reagents have similar reactive sites, such as succinimidyl ester (NHS) for amino groups and maleimide or bromoacetamide for sulfhydryl groups. Dojindo offers a wide variety of protein labeling kits. These kits can be used to prepare conjugates with enzymes, fluorophore, and biotin. Dojindo’s labeling kits contain centrifugal filtration tubes, which are used for protein purification, conjugation reaction, condensation, and buffer exchange.
Our newest addition, Ab-10 Rapid Labeling Kits allows simple and rapid preparation of enzyme or fluorophore conjugates with a smaller quantity of antibody.

Table1 Antibody labeling procedure comparison





Fig.1 Periodate method


Fig.2 NHS method


Fig.3 Labeling kit procedures


Fig.4 Ab-10 Rapid Labeling Kits Procedures



*Ab-10:Some additives in the antibody solution may interfere with the labeling if the concentration is too high. The maximum compatible concentrations of such additives are indicated in on Table 2.

Table 2 Compatible concentrations of the additives




What are Cross-Lining Reagents ?

Cross-Linking Reagents are widely used for both immune assays and protein analysis. Dojindo offers a variety of reagents that have different spacer arm lengths or functional groups. The two different types are:

  1. Hetero-bifunctional Reagents contain different reactive groups on each end of the spacer arm. Dojindo offers the reagents which have a NHS ester group (amine reactive) and a maleimide group (sulfhydryl reactive) on each end. They can be used for binding proteins that have sulfhydryl groups (such as Fab’) to enzymes such as POD and ALP.
  2. Homo-bifunctional Reagents contain the same reactive group on both ends of the spacer arm. Dojindo offers reagents that have 2 NHS ester groups. They can be used to bind proximate proteins or to introduce NHS ester group to compounds that have amino groups.

Water Insoluble Type

(1) Hetero-bifunctional Reagents
Product Name Code Length (Å) Solvent
EMCS E018 9.4 DMSO
GMBS G005 6.9 Chloroform, DMF
KMUS K214 16.7 Acetonitrile, Methyl alcohol

(2) Homo-bifunctional Reagents
Product Name Code Length (Å) Solvent
SPDP S291 4.1 Acetonitrile


Water Soluble Type

(1) Hetero-bifunctional Reagents
Product Name Code Length (Å)
Sulfo-EMCS S024 9.4
Sulfo-GMBS S025 6.9
Sulfo-HMCS S026 13.0
Sulfo-KMUS S250 16.7


Application Products
Amine Reactive NBD-F
Thiol Reactive ABD-F
SBD-F
Alpha-keto Reactive MDB
Application Products
Chelate Labeling AB-NTA free acid
Chelate Labeling of Proteins DTPA anhydride
Isothiocyanobenzyl-NTA
Isothiocyanobenzyl-EDTA
Chelate Labeling of Proteins Surfaces with Sulfhydryl Groups Maleimido-C3-NTA
Application Products
Chelate Labeling of Proteins Molecules with BABE
Sulfhydryl Groups FeBABE