БИОТИН-МАЛЕИМИД

Description

Biotin-maleimide is a heterobifunctional biotinylation reagent that combines a biotin residue with a maleimide group specific for thiol (–SH) groups. CAS 116919-18-7, formula C20H29N5O5S, molecular weight 451.54, exact mass 451.189. The molecule is built from three functional blocks: a bicyclic biotin head, recognized by streptavidin and avidin, a hydrophilic spacer that removes the maleimide group from the bulky biotin core and reduces steric hindrances when binding to the target protein, and the maleimide electrophilic center itself at the end of the molecule.

Basic Attributes

• CAS No: 116919-18-7
• Chemical Formula: C20H29N5O5S
• Molecular weight: 451.54; exact weight: 451.189
• HS code: 29349990
• PSA Specifications: 162
• XLogP3: -0.1

Physico-chemical characteristics

• Appearance: Powder
• Density: 1.286
• Boiling point: 825.0 ± 60.0 °C (predicted)
• Solubility: in acetic acid 20 mg/ml
• Storage conditions: 2–8 °C

Scope of application

The maleimide group of the reagent selectively enters into a Michael addition reaction with free thiol groups of cysteine ​​residues in proteins and peptides, covalently attaching a biotin tag to the target molecule. The resulting biotinylated conjugate is then detected or purified through the high affinity binding of biotin to streptavidin or avidin. The reagent is widely used in bioconjugation, enzyme-linked immunosorbent assay (ELISA), Western blotting, affinity purification of proteins and the creation of biotin-streptavidin sensors, where mild and selective modification of thiol groups without affecting amines and other nucleophilic centers of the protein is required. The thiol specificity of maleimide chemistry is especially valuable when labeling recombinant proteins with a single accessible cysteine ​​residue introduced by site-directed mutagenesis—in this case, the reaction produces a homogeneous, precisely localized conjugate instead of the mixture of products characteristic of amine-reactive tags such as NHS esters.

Safety Information

• WGK Germany: 3

Storage and transportation

Store at a temperature of 2–8 °C, in an airtight container, protected from light and moisture - the maleimide group of the reagent is hydrolytically unstable and gradually loses its reactivity when stored in aqueous solutions or at high humidity. The reagent is sensitive to the presence of free thiols in the storage environment, so working solutions are prepared immediately before use. Buffer solutions for conjugation are selected in the pH range of 6.5–7.5, where the reaction with thiols occurs selectively and quickly, while at higher pH values ​​the risk of side hydrolysis of the maleimide ring and a decrease in the yield of the target conjugate increases, which is important to consider when scaling protein labeling protocols in research and production biochemical laboratories.