Niwa HARUKI (丹羽 治樹)

In preclinical cancer research, bioluminescence imaging with firefly luciferase and D-luciferin has become a standard to monitor biological processes both in vitro and in vivo. However, the emission maximum (λmax) of bioluminescence produced by D-luciferin is 562 nm where light is not highly penetrable in biological tissues. This emphasizes a need for developing a red-shifted bioluminescence imaging system to improve detection sensitivity of targets in deep tissue. Here we characterize the bioluminescent properties of the newly synthesized luciferin analogue, AkaLumine-HCl. The bioluminescence produced by AkaLumine-HCl in reactions with native firefly luciferase is in the near-infrared wavelength ranges (λmax=677 nm), and yields significantly increased target-detection sensitivity from deep tissues with maximal signals attained at very low concentrations, as compared with D-luciferin and emerging synthetic luciferin CycLuc1. These characteristics offer a more sensitive and accurate method for non-invasive bioluminescence imaging with native firefly luciferase in various animal models.

Boron difluoride (BF2) complexes of N-(5-phenyl-2-pyrazinyl)pivalamide and its derivatives having a substituent on the phenyl group were prepared and their spectroscopic properties were investigated. It was found that the BF2 complexes show fluorescence in solution and the solid state. The origins of the fluorescence properties are discussed on the basis of the fluorescence yields and lifetimes, crystal structures and DFT calculations. The present work would provide a guide to design BF2 complexes of amidopyrazines exhibiting solid state fluorescence.