Water structuring centers of mammalian cell surfaces

Cultured mammalian cells appeared to express specific particles on their surface, which could be detected by their ability to nucleate ice crystals (I-centers) in a newly developed, two-dimensional crystallization assay. Their expression required approximately 24 h independent of cell density, and metabolic energy, and the number and distribution of the I-centers were cell-type specific. Their characteristic ability to nucleate ice crystals was highly sensitive to dehydration, to hyaluronidase and phospholipase C, but not to a number of proteases such as trypsin, chymotrypsin, collagenase, and pronase. However, these proteases, especially pronase, were able to detach the I-centers from the cell surface, without destroying their ability to nucleate ice crystals. I-centers were specific products of live cells, located in relatively small numbers at the cell surface organized in a detachable, sheet-like structure. We propose to consider the ice nucleating ability of I-centers as an expression of their ability to influence the water structure in the surface of cells. Even though their biological function is not known at this time, as water-structuring centers they appear remarkable enough to warrant our attention.