Fractal organisation in biological macromolecular lattices

Macromolecular solutions of proteic, glycoproteic or polysaccharidic nature in the presence of salt gave rise (when slowly dried) to dendritic-like fractal patterns. A fractal dimension D= 1.79 ±0.018 was obtained for dendritic patterns of a sonicated ovomucin gel (40% ovomucin- 60% ovalbumin) in the presence of 0.1 M NaCl. The calculated D is similar to that described in percolation clusters. The appearance of fractal patterns was dependent upon the pro- tein:salt ratio with an optimum in the range 0.75-1.25. Patterns disappeared at either lower or higher ratios. We conclude that the salt percolates through the macromolecular lattice and precipitates in fractal clusters during the drying process. Dendritic-like fractal patterns with similar D and morphologies were obtained with solutions of fetuin, ovalbumin, albumin or starch suggesting that fractal patterning is a general property of biological polymers. That cellular polymers would also aggregate in a fractal way was implied from the analysis of cellular cytoskeleton and microtrabecular lattices.