Distinct Effects of Avian Egg Derived Anionic Proteoglycans on the Early Stages of Calcium Carbonate Mineralization

This Communication addresses the effects of egg membrane- and shell-associated proteoglycans, namely, keratan sulfate and dermatan sulfate, respectively, on the nascent stages of CaCO 3 mineralization. Composed of calcitic columns intimately associated with a collagen membrane, the mechanisms underlying mineral growth are regulated by biomolecules. Of these, the role of proteoglycans is crucial because of their defined temporal and spatial distributions that direct mineral growth. The proteoglycans analyzed here induce dissimilar effects on the early stages of calcium carbonate mineralization. Egg-membrane associated keratan sulfate has a stabilizing effect toward soluble calcium carbonate prenucleation clusters and promotes formation of phases with lower solubility products after nucleation. In contrast, dermatan sulfate destabilizes prenucleation clusters and leads to more soluble phases of calcium carbonate postnucleation. The distinct effects of proteoglycans on calcium carbonate crystallization elucidate their unique spatiotemporal localization during egg mineralization.