After figuring out that the images from one particular publication are between 15 and 20% larger than the micron marker accompanying the figure indicates, I went back to re-determine how much dodecamer arm length that the mini-SP-D lost when exons 3 and 4 were deleted from the collagen domain.  Again measuring the full SP-D in the micrograph and then using other images of SP-D and their respective bar markers I think that after several sets of measurements the miniSP-D has been reduced to about 35% of its original arm length. I am measuring the center portion (which surely contains more amino acids than just the N terminal) where it bifurcates.  Different sets of measurements sort of come in around 25 or 6 nm. The CRD are pretty close, and measurements indicate that the top left figure (which is the one which has the out of sorts micron marker (indicated by the different measurements for the diameter of the  underlying SP-D dodecamer… the red circle being what was given as 100nm (clearly too short) and the green circle indicating a diameter that would intersect the CRD in 3 different locations (typically I have used intersection of 2, but this one has three by chance) and is a much more accurate indicator of a 100nm.  Using the later, the center is N term plus whatever of the collagen portion is associatiated) is about 26 hm..  in the full length AND the mini-SP-D  so this suggests that the measurements are more in line, and also that the central X of the dodecamer hasn’t changed much with the deletion of the C3 and C4 regions.   Bars used to measure the arm length are the thin black lines in the lower right.

I am not putting these numbers out as anything but approximate, but they are similar to earlier posts, and a general indication of size.

One thing that is kind of interesting to me is that the collagen-like domain is often referred to as “disorganized” and often referred to as “braided” or like the helix of collagen.  There really should not be much discussion on whether it is organized or not… haha…  just looking at the pictures.