Four dodecamers of SP-D, four databases, mean grayscale peak height for the N term peak is about 238.6 +/ 3.75 nm.  The grayscale given in the plots made for the images in ImageJ, and then subjected to a variety of image and signal processing algorithms.  The column indicated with the title NEW, is a smaller dataset taken from four dodecamers (8 trimers, put plotted as trimers) so every n= is a value for a trimer. The N term peak is plotted in its completeness for each trimer, not divided in half.  Dividing the N term in half didn’t really fit the images, as many cases there is a small peak, or valley in the center of the N trimer, and that complicates where it should be divided into two or four. So the peak of the N trimer below is the tallest point (not necessarily in the center) of the N peak.

Bottom line for me (maybe not for you) but for me is that the value of 238.6 is just fine for creating one point on the “training plot” to use for supervised learning in AI to apply to the remaining SP-D images I have obtained from published literature.

The four dodecamers used in this training plot are among the better images of SP-D (from Arroyo et al).