Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition‐ and size‐dependent absorption and emission, a broad absorption spectrum, photostability, and single‐dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long‐term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD‐labeled DNA probes was developed by attaching thiol‐ssDNA to QDs via a metal–thiol bond. The as‐prepared QD‐labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.

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Semiconductor nanocrystals, also called quantum dots (QDs), are novel inorganic fluorophores which are brighter and more photostable than organic fluorophores. In the present study, highly dispersive QD-labeled oligonucleotide (TAG)(8) (QD-deoxyribonucleic acid [DNA]) conjugates were constructed via the metal-thiol bond, which can be used as fluorescence in situ hybridization (FISH) probes. FISH analysis of maize metaphase chromosomes using the QD-DNA probes showed that the probes could penetrate maize chromosomes and nuclei and solely hybridized to complementary target DNAs. Compared with the conventional organic dyes such as Cy3 and fluorescein isothiocyanate, this class of luminescent labels bound with oligonucleotides is brighter and more stable against photobleaching on the chromosomes after FISH. These results suggest that QD fluorophores may be a more stable and useful fluorescent label for FISH applications in plant chromosome mapping considering their size-tunable luminescence spectra.

Simple, controllable and repeatable procedures to biosynthesize CdSe in Saccharomyces cerevisiae are systematically demonstrated.