5'-4-Formylbenzamide (4FB) Modification

5'-4-Formylbenzamide (4FB) is an aldehyde-functionalized oligonucleotide modification designed for highly selective, site-specific bioconjugation. The 4-formylbenzamide moiety introduces a reactive aromatic aldehyde at the 5' terminus of an oligonucleotide, providing a versatile chemical handle for coupling with hydrazine-, hydrazide-, or aminooxy-functionalized molecules. These reactions proceed efficiently under mild aqueous conditions to form stable hydrazone or oxime bonds, making 4FB one of the most widely used chemistries for controlled biomolecule conjugation.

Unlike amine- or thiol-based coupling chemistries that may require multiple activation steps or compete with endogenous functional groups, the aldehyde functionality of 4FB offers exceptional chemoselectivity. This enables the preparation of well-defined conjugates with minimal side reactions and excellent control over conjugation stoichiometry.

The 4FB modification is frequently used for conjugating oligonucleotides to antibodies, peptides, proteins, polymers, nanoparticles, enzymes, and other biomolecules that have been functionalized with complementary hydrazine, hydrazide, or aminooxy groups. The resulting conjugates exhibit excellent stability and are widely employed in molecular diagnostics, targeted drug delivery, biosensor development, imaging probes, and nucleic acid therapeutics.

Typical applications include:

• Antibody-oligonucleotide conjugates (AOCs)

• Peptide-oligonucleotide conjugates

• Protein-DNA and protein-RNA conjugation

• Oxime ligation chemistry

• Hydrazone ligation chemistry

• Site-specific bioconjugation

• Molecular diagnostics

• Biosensor development

• Surface immobilization

• Nanoparticle functionalization

• Therapeutic oligonucleotide conjugates

Bio-Synthesis offers 5'-4FB-modified DNA, RNA, PNA, antisense oligonucleotides, aptamers, and siRNA synthesized using optimized solid-phase chemistry. The modification can be combined with additional functional groups including fluorophores, quenchers, biotin, PEG linkers, GalNAc, peptides, lipids, click chemistry handles, and other custom conjugates to produce multifunctional oligonucleotide constructs tailored to specific research applications.

Each 4FB-modified oligonucleotide is manufactured under stringent quality standards and is available with optional HPLC or PAGE purification together with analytical characterization by LC-MS, MALDI-TOF, UV spectroscopy, and additional quality control testing as required.

Because of its high chemoselectivity, efficient conjugation kinetics, and compatibility with aqueous bioconjugation conditions, 5'-4-Formylbenzamide (4FB) has become a preferred modification for researchers developing next-generation bioconjugates, molecular imaging agents, targeted therapeutics, and advanced diagnostic platforms.

Product Information

 

Product Name:

5'-4-Formylbenzamide (4FB) Modification

Modification Code:

[5-4FB]

Structure:

Purification:

HPLC

Delivery Format:

Lyophilized

Shipping Conditions:

Room Temperature

Storage Conditions:

-20°C To -70°C
Oligonucleotides are stable in solution at 4°C for up to 2 weeks. Properly reconstituted material stored at -20°C should be stable for at least 6 months. Dried DNA (when kept at 20°C) in a nuclease-free environment should be stable for years.

References/Citations:

Selected References

1. Hermanson GT. Bioconjugate Techniques. 3rd ed. Academic Press; 2013.
2. Dirksen A, Dawson PE. Rapid oxime and hydrazone ligations with aromatic aldehydes for biomolecular conjugation. Bioconjugate Chemistry.
3. Jencks WP. Catalysis of hydrazone and oxime formation. Journal of the American Chemical Society.
4. Thermo Fisher Scientific. Hydrazone and Oxime Ligation Chemistry. Technical resource on aldehyde-based bioconjugation.

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