Molecular Probes

About: Molecular Probes is a based out in . It is known for research contribution in the topics: Fluorescence & Fluorophore. The organization has 296 authors who have published 455 publications receiving 36415 citations.

Self-assembled nanoscale biosensors based on quantum dot FRET donors

Abstract: The potential of luminescent semiconductor quantum dots (QDs) to enable development of hybrid inorganic-bioreceptor sensing materials has remained largely unrealized. We report the design, formation and testing of QD‐protein assemblies that function as chemical sensors. In these assemblies, multiple copies of Escherichia coli maltose-binding protein (MBP) coordinate to each QD by a C-terminal oligohistidine segment and function as sugar receptors. Sensors are selfassembled in solution in a controllable manner. In one configuration, a β-cyclodextrin-QSY9 dark quencher conjugate bound in the MBP saccharide binding site results in fluorescence resonance energy-transfer (FRET) quenching of QD photoluminescence. Added maltose displaces the β-cyclodextrin-QSY9, and QD photoluminescence increases in a systematic manner. A second maltose sensor assembly consists of QDs coupled with Cy3-labelled MBP bound to β-cyclodextrin-Cy3.5. In this case, the QD donor drives sensor function through a two-step FRET mechanism that overcomes inherent QD donor‐acceptor distance limitations. Quantum dot‐biomolecule assemblies constructed using these methods may facilitate development of new hybrid sensing materials.

Alexa Dyes, a Series of New Fluorescent Dyes that Yield Exceptionally Bright, Photostable Conjugates:

Abstract: Alexa 350, Alexa 430, Alexa 488, Alexa 532, Alexa 546, Alexa 568, and Alexa 594 dyes are a new series of fluorescent dyes with emission/excitation spectra similar to those of AMCA, Lucifer Yellow, fluorescein, rhodamine 6G, tetramethylrhodamine or Cy3, lissamine rhodamine B, and Texas Red, respectively (the numbers in the Alexa names indicate the approximate excitation wavelength maximum in nm). All Alexa dyes and their conjugates are more fluorescent and more photostable than their commonly used spectral analogues listed above. In addition, Alexa dyes are insensitive to pH in the 4-10 range. We evaluated Alexa dyes compared with conventional dyes in applications using various conjugates, including those of goat anti-mouse IgG (GAM), streptavidin, wheat germ agglutinin (WGA), and concanavalin A (ConA). Conjugates of Alexa 546 are at least twofold more fluorescent than Cy3 conjugates. Proteins labeled with the Alexa 568 or Alexa 594 dyes are several-fold brighter than the same proteins labeled with lissamine rhodamine B or Texas Red dyes, respectively. Alexa dye derivatives of phalloidin stain F-actin with high specificity. Hydrazide forms of the Alexa dyes are very bright, formaldehyde-fixable polar tracers. Conjugates of the Alexa 430 (ex 430 nm/em 520 nm) and Alexa 532 (ex 530 nm/em 548 nm) fluorochromes are spectrally unique fluorescent probes, with relatively high quantum yields in their excitation and emission wavelength ranges.