White Gaye F, Litvinenko Konstantin L, Meech Stephen R, Andrews David L, Thomson Andrew J
School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UKNR4 7TJ.
Photochem Photobiol Sci. 2004 Jan;3(1):47-55. doi: 10.1039/b306760b. Epub 2003 Sep 9.
The Tb(iii) complex of the iron-transport protein transferrin (Tb(2)-Tfr) exhibits strongly sensitised, sharp line luminescence from f-f states following multiphoton excitation via two tyrosinate residues directly co-ordinated to the lanthanide ion. Using an ultrafast Ti:sapphire laser system, a quadratic dependence of the Tb(iii) luminescence intensity was observed on excitation with photons at 503 and 566 nm, and a cubic dependence with photons at 800 nm. The two-photon cross-sections at 503 and 566 nm are 7.4 x 10(-50) and 0.37 x 10(-50) cm(4) s photon(-1) mol(-1), respectively, which compare favourably with values reported for the green fluorescent protein. Three-photon excitation at 800 nm gives rise to a Tb(iii) emission spectrum with excellent signal to noise ratios. These results lead to a proposal that if a Tb(iii)-protein complex with similar luminescent properties could be formed in vivo, an intra-cellular imaging system that uses multiphoton-excited, long-lived lanthanide ion luminescence could be developed. This offers the prospect of multiphoton imaging in tight focal planes using sharp line emission with long lifetimes for wavelength and time discrimination against background fluorescence.
铁转运蛋白转铁蛋白的铽（III）配合物（Tb(2)-Tfr）在通过两个直接与镧系离子配位的酪氨酸残基进行多光子激发后，呈现出强烈敏化的、来自f-f态的锐线发光。使用超快钛宝石激光系统，观察到铽（III）发光强度在503和566 nm处的光子激发下呈二次方依赖关系，在800 nm处的光子激发下呈三次方依赖关系。503和566 nm处的双光子截面分别为7.4×10⁻⁵⁰和0.37×10⁻⁵⁰ cm⁴ s photon⁻¹ mol⁻¹，与报道的绿色荧光蛋白的值相比具有优势。800 nm处的三光子激发产生了具有出色信噪比的铽（III）发射光谱。这些结果提出了一个设想，即如果能在体内形成具有类似发光特性的铽（III）-蛋白质配合物，那么就可以开发一种利用多光子激发、长寿命镧系离子发光的细胞内成像系统。这为在紧密焦平面上进行多光子成像提供了前景，利用锐线发射和长寿命进行波长和时间分辨，以区分背景荧光。
