Monthly Archives: November 2018

Center and arc angles of SP-D molecules

surfactant proteins A and D, Ultimate order, the cell

ADDED several new dodecamers to the measure of arc angle of the individual trimeric arms of a dodecamer of SP-D.
N 39
Sum: 1425.97
Mean (Average): 36.563333333333
Standard Error of the Mean (SEx̄): 1.5825376081318
Center angles for surfactant protein D, grouped by degrees (10) do show a tendency to be organized into two sets. You can see that acute and obtuse angles are present. It did require the measurement of more than 30 randomly found TEMs of SP-D to arrive at this graph. Initially no division was seen, the angles looked more like a continuum.

Picture below has several dodecamers added from yesterdays post and it represents several (probably at least 4) different laboratories and at least a few molecules from each. I have created a second “quintessential” SP-D molecule with measures. See bottom figure. It becomes pretty critical to measure the arc angles from the edge of the N +whatever portion of the collagen-like domain remains closely tethered in the center of the SP-D dodecamer.  The arc angle changes dramatically with that adjustment.  I will measure N terminals of these same molecules (or what everyone describes as the tethered N terminals) and compare with actual TEMs.  I can tell you from the diagrams I have found, no one gets that one right when they draw their dodecamers.  haha.
surfactant protein D dodecamer angles
surfactant protein D dodecamer angles
surfactant protein D dodecamer angles

Center angles and arc angles: Surfactant protein D

surfactant proteins A and D

Here is a summary chart for the images I measured central and arc angles on.  There is clearly a lot of variation. The bottom line is that the collagen-like portion is flexible, and likely relates to the ability of even mutant (missing small parts of the collagen-like domain) to still function, but with the collagen-like domain is totally missing…. the function changes considerably.  This was research by ……a long list of scientists other than myself.

Here you can see for yourself that there is an acute angle and an obtuse angle in almost every view. That there is also an arc to the collagen portion of the molecule. So while the diagrammers got part of it right (see this post for a summary of the SP-D diagrams)…. straight arms for SP-D molecules are “fake news”.

summary chartg for arc angles and center angles for surfactant protein D