Key points are not available for this paper at this time.
Diatom shells (see picture of cell of Stephanopyxis turris) contain long-chain polyamines attached either to putrescine or to phosphorylated silaffin peptides. These polyamines direct the in vitro formation of silica nanospheres from silicic acid. The concentration of multivalent anions (such as phosphate) defines the diameter of the nanospheres produced.
Sumper et al. (Thu,) studied this question.