PubMed · 13786599
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J D WOODWARD. 1961. Biotin.. https://doi.org/10.1038/scientificamerican0661-139
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A library of bidentate fragments linked through an oligonucleotide duplex was tested for binding to streptavidin. When one fragment was biotin, only biotin-containing duplexes were selected by streptavidin but when heated above the melting temperature, only bidentate biotin ligands were obtained. Thermal denaturation experiments showed that the melting temperature, thus stability, of the monodentate versus bidentate binding ligand increased from 59 to 71 degrees C in the presence of streptavidin. Substituting biotin with 2-iminobiotin led to the exclusion of all other duplexes by the bidentate iminobiotin duplex in binding streptavidin.
Soft landing of singly charged gas-phase ions on dry metal surfaces that were pretreated in situ by oxygen plasma results in 0.1-2% total yields of recovered intact compounds. Lysine, peptides, crystal violet dye, and a biotin conjugate are found to survive soft landing of hyperthermal ions of up to 50-eV kinetic energy. Soft landing at 40-50-eV ion kinetic energies of a fluorescence-labeled biotin conjugate results in an immobilized fraction that cannot be washed from the surface and is found to contain an intact biotin moiety. The present results represent an approximately 10(4) fold improvement in soft-landing efficiency and indicate that plasma-treated metal surfaces can be useful for preparative separation of organic and biological molecules by mass spectrometry. The substantial improvement in soft-landing yields results from a high transmission of electrosprayed ions into the vacuum system, efficient and nondestructive discharge of ions on the metal oxide surface, and facile analyte recovery in the absence of a matrix.
Semiconductor quantum dots (QDs) have been used in a simple fluorometric assay to detect single cells of the pathogenic Escherichia coli O157:H7 serotype. Composed of CdSe/ZnS core/shell QDs conjugated to streptavidin, this system exhibits 2 orders of magnitude more sensitivity than a similar assay using a common organic dye. Selectivity for this pathogenic bacterial strain over a common lab strain (E. coli DH5alpha), which is gained from the use of specific biotinylated antibodies, is also demonstrated for QD labeling. Under continuous excitation, these QDs retain high fluorescence intensities for hours, whereas a typical organic dye bleaches within seconds, allowing for more rapid and accurate identification of E. coli O157:H7 in single-cell fluorescence-based assays. This indirect QD labeling method, based on antibody-antigen and streptavidin-biotin interactions, is flexible enough to expand to other systems and has great potential for use in simultaneous multicolor detection schemes.