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
HMCS H257 13.0 Acetonitrile
KMUS K214 16.7 Acetonitrile, Methyl alcohol

(2) Homo-bifunctional Reagents
Product Name Code Length (Å) Solvent
DSP D629 8.5 DMSO, DMF
SPDP S291 4.1 Acetonitrile

(3) other
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
Sulfo-SMCC S330 8.0

(2) Homo-bifunctional Reagents
Product Name Code Length (Å)
BS3 B574 8.9
DTSSP D630 8.5

(3) other
Product Name Code Length (Å)
Sulfo-AC5-SPDP S359 12.6




Biotin labeling
Application Products
Amine Reactive Ab-10 Rapid Biotin Labeling Kit
Biotin Labeling Kit-NH2
Biotin-OSu
Biotin-AC5-OSu
Biotin-(AC5)2-OSu
Biotin Sulfo-OSu
Biotin-AC5 Sulfo-OSu
Biotin-(AC5)2 Sulfo-OSu
Biotin-SS-Sulfo-OSu
Thiol Reactive Biotin Labeling Kit-SH
Biotin-PEAC5-maleimide
Biotin-PE-maleimide
Biotin-HPDP
Aldehyde Reactive ARP (Aldehyde Reactive Probe)
Enzyme labeling
Application Products
Amine Reactive Ab-10 Peroxidase Labeling Kit
Alkaline Phosphatase Labeling Kit-NH2
Peroxidase Labeling Kit-NH2
Thiol Reactive Alkaline Phosphatase Labeling Kit-SH
Peroxidase Labeling Kit-SH


Fluorophore labeling
Application Products
Amine Reactive Ab-10 Fluorescein Labeling Kit
Ab-10 R-Phycoerythrin Labeling Kit
Ab-10 Rapid HiLyte Fluor 555 Labeling Kit
Ab-10 Rapid HiLyte Fluor 647 Labeling Kit
Allophycocyanin Labeling Kit-NH2
Fluorescein Labeling Kit-NH2
HiLyte Fluor 555 Labeling Kit-NH2
HiLyte Fluor 647 Labeling Kit-NH2
HiLyte Fluor 750 Labeling Kit-NH2
R-Phycoerythrin Labeling Kit-NH2
IC3-OSu special packaging
IC5-OSu special packaging
ICG Labeling Kit - NH2
ICG-Sulfo-OSu
ICG-EG4-Sulfo-OSu
ICG-EG8-Sulfo-OSu
Thiol Reactive Allophycocyanin Labeling Kit-SH
R-Phycoerythrin Labeling Kit-SH
Cross-Linking Reagents
Application Products
Homo-Bifunctional Reagents BS3
DSP
DTSSP
Hetero-Bifunctional Reagents EMCS
GMBS
HMCS
KMUS
Sulfo-EMCS
Sulfo-GMBS
Sulfo-HMCS
Sulfo-KMUS
SPDP
Sulfo-SMCC
Sulfo-AC5-SPDP


HPLC Derivertization Reagents
Application Products
Amine Reactive NBD-F
Thiol Reactive ABD-F
NAM
SBD-F
Alcohol Reactive DMEQ-COCl
Alpha-keto Reactive MDB
Aromatic Aldehyde Reactive DDB
Carboxylic Acid Reactive Br-DMEQ
Chelate Labeling
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


Protein-DNA Interaction
Application Products
Chelate Labeling of Proteins Molecules with Sulfhydryl Groups BABE
- FeBABE