The nitrodibenzofuran chromophore: a new caging group for ultra-efficient photolysis in living cells

Atsuya Momotake^1, 4, Nicolas Lindegger², Ernst Niggli², Robert J Barsotti³ & Graham C R Ellis-Davies¹

¹  Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th St., Philadelphia, Pennsylvania 19102, USA.

²  Department of Physiology, University of Bern, Buhlplatz 5, Bern, CH-3012, Switzerland.

³  Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust St., Philadelphia, Pennsylvania 19107, USA.

⁴  Present address: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba-shi Ibaraki-ken, 305-8577, Japan.

Photochemical uncaging of bio-active molecules was introduced in 1977, but since then, there has been no substantial improvement in the properties of generic caging chromophores. We have developed a new chromophore, nitrodibenzofuran (NDBF) for ultra-efficient uncaging of second messengers inside cells. Photolysis of a NDBF derivative of EGTA (caged calcium) is about 16–160 times more efficient than photolysis of the most widely used caged compounds (the quantum yield of photolysis is 0.7 and the extinction coefficient is 18,400 M^-1 cm^-1). Ultraviolet (UV)-laser photolysis of NDBF-EGTA:Ca²⁺ rapidly released Ca²⁺ (rate of 20,000 s^-1) and initiated contraction of skinned guinea pig cardiac muscle. NDBF-EGTA has a two-photon cross-section of 0.6 GM and two-photon photolysis induced localized Ca²⁺-induced Ca²⁺ release from the sarcoplasmic recticulum of intact cardiac myocytes. Thus, the NDBF chromophore has great promise as a generic and photochemically efficient protecting group for both one- and two-photon uncaging in living cells.

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