Open-and-Shut Case

Dr. Shawn Burdette tweeted up the chem-blognoscenti earlier tonight to ask about some "funny business" between two papers. The first (JACS 2009, Pierre) predates the second (Chem. Eur. J. 2013, Yan) by about 4 years, and yet their "Figures 1" both look strangely, well, similar...

Well, OK, folks who play in the same sandbox sometimes use the same shovel, right? Maybe the 2013 paper became so enamored of its predecessor that it couldn't help itself.

But then, I started through the text. Since I didn't have my pink highlighter handy to cantrill them (sorry, Stu!), I decided just to clip out phrases I thought sounded Déjà vu-ish:

Pierre (p. 1): "Time-gated luminescence imaging presents an elegant solution to the problem of background luminescence by setting a time delay between the excitation pulse and the luminescence detection, thereby allowing the luminescence of the media to decay before measuring that of the probe. This technique, however, requires chemical probes with luminescence lifetimes significantly longer than that of the biological medium."


Yan (p. 1): "Time-gated luminescence imaging presents an elegant solution to the problem of background luminescence by setting a time delay between the excitation pulse and luminescence detection; this allows the luminescence of the media to decay before that of the probe is measured. However, this technique requires chemical probes with luminescence lifetimes significantly longer than that of the biological medium."

Or how about this?

Pierre (p. 2): "Notably, the observed selectivity cannot result solely from selective binding of K+ by the diaza-18-crown-6. The selectivities of the lariat ether for K+ over Na+ and Ca2+ in anhydrous alcohol are barely 5- to 10-fold.(7) Tb derivatives of these ethers also demonstrate poor selectivity (4-fold)."

Yan (p. 3): "Notably, the observed selectivity cannot result solely from selective binding of potassium(I) by the diaza-18-crown-6. The selectivities of the lariat ether for potassium(I) over sodium(I) and calcium(II) in solution are barely five- to tenfold.[16] Tb derivatives of these ethers also demonstrate poor selectivity (fourfold)."

One more for posterity:

Pierre (p. 1): "...the flexible structure of the ligand results in an overall large separation between the Tb ion and its sensitizing azaxanthone, resulting in weak Tb luminescence the aryl ether, thereby locking the complex in a conformation where the antenna is significantly closer to the Tb center. Consequently, the efficiency of energy transfer from the azaxanthone to the Tb and the resulting luminescence from the complex are increased."

Yan (buried in the Figure 1 legend!): "...The flexible structure of the ligand results in an overall large separation between the Tb center and its sensitizing antenna, BP, resulting in weak Tb luminescence [snip] The locking conformation causes the antenna to be significantly closer to the Tb center. Consequently, the efficiency of energy transfer from BP to Tb and the luminescence from the complex are increased..."

Cherry on top? The 2013 authors bury the 2009 authors' paper in Ref. 14d. Sigh.

Well, kids, I think we have our answers. While I don't have any skin in the "fluorescent K+ sensors" game, I also abhor unfair play. To this end, I've sent a cheerful email to the Editorial staff of both journals, and will print here any response I obtain.

Thanks for playing!
-SAO

Update (1/23/13): CJ adds his thoughts and a pretty (damning) picture.