Biotin-dPEG®₃-NH₃+TFA-

Biotin-dPEG®3-NH3+TFA- (Biotin-dPEG®3-ammonium trifluoroacetate), product number 10193, is one of several biotinylation products offered by Quanta BioDesign, Ltd. The product reacts with activated esters (N-hydroxysuccinimide, 2,3,5,6-tetrafluorophenyl) of carboxylic acids under mildly basic conditions. It can be coupled directly to a carboxylic acid using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) chemistry. Also, the product can react with carbonyl groups (aldehydes or ketones) to form a Schiff base. The Schiff base can be reduced to a secondary amine using sodium cyanoborohydride if additional conjugate stability is necessary.

Biotinylation
Biotinylation is the process of covalently attaching biotin to a molecule such as a peptide, protein, or nucleic acid, or a surface such as glass or gold. Bioconjugation research, product development, and many types of clinical tests use biotinylated products.

Biotin usually is poorly soluble in water, but the amphiphilic dPEG® linker imparts excellent solubility in water or aqueous buffer and organic solvents. In the past, there have not been many choices for carbonyl- and carboxylic acid-reactive biotinylation reactions. The most popular choices were biotin-hydrazide, biocytin-hydrazide (biotin-lysine hydrazide), and biotin-LC-hydrazide (biotin-aminocaproic acid hydrazide), but all of these choices are unfortunately quite hydrophobic. These older, hydrophobic reagents required solvation in an organic solvent such as N,N'-dimethylformamide (DMF) or dimethylsulfoxide (DMSO) before using in an aqueous buffer. When conjugated to proteins or other biomacromolecules, the hydrophobic interactions caused or exacerbated by these reagents triggered aggregation and precipitation of conjugated molecules and increased background noise through non-specific binding.

Amphiphilic biotin-dPEG®3-NH3+TFA- dissolves equally well in aqueous buffers and organic solvents. There is no need to dissolve this product in an organic solvent before using it in aqueous reaction media. Furthermore, biotinylation of biomacromolecules with PN10193 will not cause aggregation and precipitation. Eliminating aggregation should consequently improve signal-to-noise ratios in applications developed with this product. Reaction with a carboxylic acid or active ester of a carboxylic acid will yield a stable amide bond. Aldehydes are uncommon in biomacromolecules, but they form through the oxidation of reducing sugars in glycosylated proteins. Reactions with aldehydes will produce imines that can be reduced under mild conditions to secondary amines with sodium cyanoborohydride.

Any application that can take advantage of the powerful biotin-avidin/streptavidin affinity can use Biotin-dPEG®3-NH3+TFA-. The terminal amine of PN10193 offers the opportunity to biotinylate (1) the carbohydrate coat of glycoproteins, and (2) surfaces consisting of carboxylic acids or their active esters. Thus, Biotin-dPEG®3-NH3+TFA- expands the range of molecules and nanoparticles for which dPEG®-biotin is useful.

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