If you wish to report data irregularities, especially a recurrent pattern thereof, one is well adviced not to write to the scientist behind those published papers, but to the institutional Ombudsman. This is also what is recommended by the US Office for Research Integrity (ORI, here) and by two real-life whistleblowers from Sweden:
“Collect evidence, but don’t contact the accused with questions if you are certain that they fabricated data, because they may then hide their tracks. Identify the appropriate authority where misconduct should be reported; this could be at your own or the accused’s institution”.
My own experience with reporting evidence to institutional Ombudspersons is mixed. Some do not reply at all (one of those has actually shady data in his own papers), some eventually write something non-saying back, some do take the issue seriously. A German university Ombudsman quickly put right a professor and dean of her department, and issued an apology on her behalf, after she attacked me for disagreeing with her on the academic merits of predatory conferences and medals issued by the false Linköping University professor Ashutosh Tiwari.
The Ombudsman of the University of Osnabrück in northern Germany, when alerted to PubPeer evidence of some strange image duplications in papers by an Osnabrück plant scientist, acted differently. The Ombudsman, a law professor, indirectly threatened me with a libel lawsuit, and refused to process the notification. The next day, the plant scientist admitted duplications on PubPeer, one paper has been already extensively corrected. This beautiful piece of evidence was posted on PubPeer on September 4th 2017.
The anonymous commenter, under the randomly assigned name Ptychohyla leonhardschultzei (Schultze’s Stream Frog) added: “Reusage of images in 4 articles“. We do see that the same flowers blossomed in four different publications from the lab of the University of Osnabrück botany professor Sabine Zachgo, specialist for developmental genetics of flowering plants. The flowery images re-appear across papers (as visualised by arrows) in different context, often standing in for different plant genotypes, sometimes cropped, rotated or mirrored. The four papers were:
1. Shutian Li , Andrea Lauri , Mark Ziemann , Andrea Busch , Mrinal Bhave , Sabine Zachgo
Nuclear Activity of ROXY1, a Glutaredoxin Interacting with TGA Factors, Is Required for Petal Development in Arabidopsis thaliana. The Plant Cell (2009) doi: 10.1105/tpc.108.064477
The ROXY1 C-Terminal L**LL Motif Is Essential for the Interaction with TGA Transcription Factors PLANT PHYSIOLOGY (2011) doi: 10.1104/pp.111.185199
3. Jhadeswar Murmu , Michael J Bush , Catherine DeLong , Shutian Li , Mingli Xu , Madiha Khan , Caroline Malcolmson , Pierre R Fobert , Sabine Zachgo , Shelley R Hepworth Arabidopsis Basic Leucine-Zipper Transcription Factors TGA9 and TGA10 Interact with Floral Glutaredoxins ROXY1 and ROXY2 and Are Redundantly Required for Anther Development PLANT PHYSIOLOGY (2010) doi: 10.1104/pp.110.159111