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![[Figure 7]](ig5011fig7mag.jpg)
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Figure 7
Severe clustering of insulin crystals made indexing difficult for 5 µm crystals (seen here on a micro-mesh with 20 µm openings). Frequently, our scanned images were either empty or had multiple overlapping diffraction patterns (inset). The attraction between crystals is predominantly short range. The x, y coordinates were determined for 450 crystals visible on a 700 µm micro-mesh. The distance between each crystal and every other crystal was calculated. The graph shows the relative probability of encountering neighbors as a function of distance (µm). The curve is normalized by dividing the experimental probability distribution by the probability distribution obtained from computer-generated random locations; since the graph is normalized, a random experimental distribution would have a flat probability ratio equal to unity. A polynomial best fit is also shown. The spike at 7 µm (slightly larger than the average crystal size) indicates that there are many crystals located adjacent to other crystals. We hypothesize that surface tension may exert a short-range attractive force that draws crystals together. The relative probability falls below unity for distances of 200 µm or more. |
![[Figure 7]](ig5011fig7.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
