Emission spectra from copper proteins containing type-3 centres

Bio-doping of regenerated silk fibroin solution and films: a green route for biomanufacturing

Optically active silk fibroin films could be successfully obtained by biodoping, i.e. from cocoons of Bombyx mori fed with a rhodamine B-added diet.

UV excitable fluorescence of lumirubin

Solutions of bilirubin in different solvents show negligible fluorescence when they are excited with UV light. After irradiation, blue-violet fluorescence (400-450 nm) is observed, whose intensity and peak position depend on the irradiation time. The isolation of pure lumirubin led us to attribute this fluorescence specifically to this photoisomer, even if small contributions from other photoproducts cannot be ruled out. The emission peak of the pure lumirubin in aqueous solution (phosphate buffer) is at 415 nm while the main excitation peak is at 315 nm. Finally, an interpretation of the observed fluorescence is proposed on the basis of the similarity of the present results with previously reported experimental data.

Fluorescence-based assay of estrogen receptor using 12-oxo-9(11)-dehydroestradiol-17 beta

12-Oxo-9(11)-dehydroestradiol-17 beta (12-oxo-E2) was used to assay estrogen receptor binding in uterine cytosol preparations by an indirect fluorescence assay. In alkaline solution, 12-oxo-E2 has a fluorescence excitation maximum at 402 nm (epsilon = 24,000) and an emission maximum at 480 nm (phi f = 0.57), and its fluorescence can be observed down to 5 X 10(-11) M. The minimum detection limit of 12-oxo-E2 is 25 fmol by spectrofluorometry and 5 fmol by HPLC-fluorometry. Although this compound is not appreciably fluorescent at neutral pH (i.e., at conditions under which it binds to the estrogen receptor), receptor binding by fluorometry can be measured indirectly: After equilibration of 12-oxo-E2 with the receptor preparation and removal of excess free ligand, the receptor-12-oxo-E2 complex is disrupted, and fluorescence measurements are made on the dissociated 12-oxo-E2 in alkaline medium. This fluorometric assay was validated quantitatively by performing simultaneously, on the same receptor preparation, radiometric and fluorometric assays with [3H]E2 and [3H]-12-oxo-E2. The radiometric determinations with both compounds gave nearly equivalent estimates of receptor site concentrations, but the fluorometric estimate of binding site concentration was somewhat less (70-85%) than that expected on the basis of the [3H]E2 radiometric assay. The use of 12-oxo-E2 in an indirect spectro- or HPLC-fluorometric assay provides a means for assaying estrogen receptor concentrations by fluorescence with a sensitivity approaching that of radiometric techniques.