High-performance liquid chromatographic determination of biotin in biological materials after crown ether-catalyzed fluorescence derivatization with panacyl bromide

Biotin-phenosafranin as a new photosensitive conjugate for targeted therapy and imaging

A biotinylated phenazine compound as a phenosafranin conjugate (Biot-PSF) was synthesized and reported for the first time.

Electrochemical Sensing of Biotin Using Nafion-Modified Boron-Doped Diamond Electrode

Nafion formed on the surface of a boron-doped diamond electrode allows for a chemosensing system for biotin. The modified electrode is capable of oxidizing biotin and offers a detection limit of 5 nM, the average normal level of biotin in blood plasma. The developed method was successfully applied to determine biotin in human plasma samples and a popular health product as two popular models.

Post-capillary reaction detection in capillary electrophoresis based on the streptavidin-biotin interaction. Optimization and application to single cell analysis

A class-selective post-capillary reaction detection method for capillary electrophoresis is described in which a streptavidin-fluorescein isothiocyanate (streptavidin-FITC) conjugate is used to detect biotin moieties. The selective binding of biotin moieties to the streptavidin-FITC conjugate causes an enhancement of fluorescence proportional to the concentration of biotin present. After capillary electrophoresis the separated analytes react with streptavidin-FITC in a coaxial reactor and are then detected either by a benchtop spectrofluorometer (2.5 microM detection limit) or by an epi-fluorescence microscope (1 x 10(-7) M detection limit). The method is used to examine biotinylated species in a crude mammalian cell lysate which was found to contain 83+/-3 fmol in 3600 cell volumes. In addition, it is used to examine the uptake of biotin by individual sea urchin oocytes. The results indicate that, in the oocytes, biocytin is the prevalent form of biotin and its concentration varies widely between cells (mean=2+/-2 microM).

Analytical techniques for determining biotin

Biotin is a vitamin of the B-complex, which plays an important biochemical role in every living cell. In the recent years, the interest in this vitamin has been rekindled, mainly due to its association with serious human disorders, such as the inherited syndrome multiple carboxylase deficiency, which can be successfully treated with biotin administration. Diagnosis of biotin deficiency as well as monitoring of biotin levels in biological fluids of patients receiving biotin treatment is crucial. Equally important is the determination of biotin levels in pharmaceutical preparations as well as in food and food supplement products, which constitute the main source of biotin in humans. Several analytical methods for measuring biotin in various samples, e.g. human fluids, pharmaceutical formulations, food material etc., have been reported in the literature. In this review, the most representative of these methods are presented, and their characteristics are evaluated.

Fluorescence detection of biotin using post-column derivatization with OPA in high performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic method with post-column derivatization, using o-phthalaldehyde (OPA) and 3-mercaptopropionic acid (3-MPA), is described for the determination of biotin in pharmaceutical preparations. The use of 3-MPA gives intense fluorescent derivative and improves the stability of biotin fluorophore towards oxidation to the picomole level. The fluorophore was detected at 453 nm (excitation at 342 nm). The calibration graph was linear for 20-200 ng per injection. The detection limit of biotin under these conditions was about 10 ng per injection. The RSDs were 1.9-3.4%. This method could be applied to pharmaceutical preparations without interference of other compounds.

Reactivity of p-[18F]fluorophenacyl bromide for radiolabeling of proteins and peptides

Radiolabeling of the somatostatin analog octreotide was attempted with p-[18F]fluorophenacyl bromide ([18F]FPB). Following these unsuccessful trials, the reactivity of FPB was studied using benzyl mercaptan, phenyl acetic acid, benzyl alcohol, and benzyl amine as model compounds for amino acid functional groups. Structure and purity of products, relative reactivity of FPB in competition reactions, and radiolabeling experiments are described. In addition, improvement in labeling efficiency of HSA using [18F]FPB was achieved by pretreatment with 2-iminothiolane.

Tryptophan residues in caldesmon are major determinants for calmodulin binding

Calmodulin has been shown to interact with the COOH-terminal domain of gizzard h-caldesmon at three sites, A (residues 658-666), B (residues 687-695), and B' (residues 717-725), each of which contains a Trp residue [Zhan et al. (1991) J. Biol. Chem. 266, 21810-21814; Marston et al. (1994) J. Biol. Chem. 296, 8134-8139; Mezgueldi et al. (1994) J. Biol. Chem. 269, 12824-12832]. To determine the contribution of each of the three Trp residues in the calmodulin-caldesmon interaction, we have mutated the Trp residues to Ala in the COOH-terminal domain of fibroblast caldesmon (CaD39) and studied the effects on calmodulin binding by fluorescence measurements and using immobilized calmodulin. Wild-type CaD39 binds with a Kd of 0.13 x 10(-6) M and a stoichiometry of 1 mol of calmodulin per mol of caldesmon. Replacing Trp 659 at site A or Trp 692 at site B to Ala reduces binding by 22- and 31-fold (Kd = 2.9 x 10(-6) and 4.0 x 10(-6) M), respectively, and destabilizes the CaD39-calmodulin complex by 1.75 and 1.94 kcal mol-1, respectively. Mutation of both Trp 659 and Trp 692 to Ala further reduces binding with a Kd of 6.1 x 10(-6) M and destabilizes the complex by 2.17 kcal mol-1. On the other hand, mutation of Trp 722 at site B' to Ala causes a much smaller decrease in affinity (Kd = 0.6 x 10(-6) M) and results in a destabilization energy of 0.87 kcal mol-1. To investigate the relative importance of the amino acid residues near each Trp residue in the caldesmon-calmodulin interaction, deletion mutants were constructed lacking site A, site B, and site A + B. Although deletion of site A decreases binding of CaD39 to calmodulin by 13-fold (Kd = 1.7 x 10(-6) M), it results in tighter binding than mutation of Trp 659 to Ala at this site, suggesting that the residues neighboring Trp 659 may contribute negatively to the interaction. Deletion of site B causes a similar reduction in binding (Kd = 4.1 x 10(-6) M) as observed for replacing Trp 692 to Ala at this site, indicating that Trp 692 is the major, if not the only, binding determinant at site B. Deletion of both site A and site B drastically reduces binding by 62-fold. Taken together, these results suggest that Trp 659 and Trp 692 are the major determinants in the caldesmon-calmodulin interaction and that Trp 722 in site B' plays a minor role.

Sensitive and selective liquid chromatographic postcolumn reaction detection system for biotin and biocytin using a homogeneous fluorophore-linked assay

A homogeneous fluorophore-linked assay was used to develop a postcolumn reaction detection system for high-performance liquid chromatography (HPLC). Biotin and biocytin were chosen as the model analytes. The effluent from the HPLC column was merged with a reagent stream containing avidin that was labeled with fluorescein isothiocyanate (avidin-FITC). The binding of the separated analytes by the labeled avidin was accompanied by an enhancement of the fluorescence intensity at 520 nm. This increase in fluorescence was proportional to the concentration of the analytes and constituted the analytical signal. The procedure was optimized with respect to the reagent concentration and the flow-rate of the reagent solution. Analytical characteristics of the method were determined. The procedure was highly selective for biotin and its derivatives. The detection limits for biotin and biocytin were 89 and 94 pg, respectively, for 20-microliters injections. The developed postcolumn reaction detection system was validated by determining biotin in a liquid vitamin preparation and a horse-feed supplement.