Invitrogen™ Alexa Fluor™ 430 NHS Ester (Succinimidyl Ester) 

Description

In addition to reactive dye formulations, Invitrogen offers Alexa Fluor™ 430 dye conjugated to a variety of antibodies, peptides, proteins, tracers, and amplification substrates optimized for cellular labeling and detection.

The NHS ester (or succinimidyl ester) of Alexa Fluor™ 430 is the most popular tool for conjugating this dye to a protein or antibody. NHS esters can be used to label to the primary amines (R-NH₂) of proteins, amine-modified oligonucleotides, and other amine-containing molecules. The resulting Alexa Fluor™ conjugate will exhibit brighter fluorescence and greater photostability than the conjugates of other spectrally similar fluorophores.

Detailed information about this AlexaFluor™ NHS ester:
• Fluorophore label: Alexa Fluor™ 430 dye
• Reactive group: NHS ester
• Reactivity: Primary amines on proteins and ligands, amine-modified oligonucleotides
• Excitation/Emission of the conjugate: 430/545 nm
• Extinction coefficient: 15,000 cm-1M-1
• Molecular weight: 701.8
• Typical Conjugation Reaction

Conjugate amine-reactive reagents with virtually any protein or peptide (the provided protocol is optimized for IgG antibodies). You can scale the reaction for any amount of protein, but the concentration of the protein should be at least 2 mg/mL for optimal results. We recommend trying three different degrees of labeling, using three different molar ratios of the reactive reagent to protein.

The Alexa Fluor™ NHS ester is typically dissolved in high-quality anhydrous dimethylformamide (DMF) or dimethylsulfoxide (DMSO) (D12345), and the reaction is carried out in 0.1–0.2 M sodium bicarbonate buffer, pH 8.3, at room temperature for 1 hour. Because the pKa of the terminal amine is lower than that of the lysine epsilon-amino group, you may achieve more selective labeling of the amine terminus using a buffer closer to neutral pH.

Conjugate Purification
Labeled antibodies are typically separated from free Alexa Fluor™ dye using a gel filtration column, such as Sephadex™ G-25, BioGel™ P-30, or equivalent. For much larger or smaller proteins, select a gel filtration media with an appropriate molecular weight cut-off or purify by dialysis. We offer several purification kits optimized for different quantities of antibody conjugate:
• Antibody Conjugate Purification Kit for 0.5-1 mg (Cat. No. A33086)
• Antibody Conjugate Purification Kit for 20-50 μg (Cat. No. A33087)
• Antibody Conjugate Purification kit for 50-100 μg (Cat. No. A33088)

Learn More About Protein and Antibody Labeling
Invitrogen offers a wide selection of Molecular Probes™ antibody and protein labeling kits to fit your starting material and your experimental setup.