Abstract
We have applied quantum dot (Qdot) antibody conjugates as a biomolecular probe for cellular proteins important in biogeochemical cycling in the sea. Conventional immunological methods have been hampered by the strong autofluorescence found in cyanobacteria cells. Qdot conjugates provide an ideal alternative for studies that require long-term imaging of cells such as detection of low abundance cellular antigens by fluorescence microscopy. The advantage of Qdot labeled probes over conventional immunological methods is the photostability of the probe. Phycoerythrin bleaches in cyanobacterial cells under prolonged UV or blue light excitation, which means that the semiconducting nanocrystal probe, the Qdot, can yield a strong fluorescent signal without interference from cellular pigments.
Highlights
Detecting proteins by epifluorescence microscopy in whole-cells of cyanobacteria has been problematic and sometimes impossible due to the presence of highly autofluorescent natural pigments [1,2,3]
We describe the use of quantum dot (Qdot) antibody conjugates for detection of nitrogenase in highly autofluorescent unicellular cyanobacteria Crocosphaera watsonii (WH8501) and in the filamentous cyanobacteria Trichodesmium erythraeum (IMS101) cells
Iron stressed C. watsonii cells probed with the IdiA antibody and labeled with Qdot 605 secondary antibody probe that were exposed to blue light for 60 s displayed a bright fluorescent signal from the photostable nanocrystal conjugate (Figure 1B)
Summary
Detecting proteins by epifluorescence microscopy in whole-cells of cyanobacteria has been problematic and sometimes impossible due to the presence of highly autofluorescent natural pigments [1,2,3]. This strong autofluorescence from natural pigments, such as phycoerythrin, can mask probes consisting of organic fluorophores. Semiconducting nanocrystals or quantum dots (Qdots) can be conjugated to antibody probes and in this study we use this technology to detect proteins in situ in highly autofluorescent unicellular and filamentous cyanobacteria. Qdots (CdSe/ZnS) exhibit a size-dependent tunable bright photoluminescence that spans the visible spectrum
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