Snowflake in the same micro-environment does not guarantee that each arm grow the same; indeed, for some crystal forms it does not because the underlying crystal growth mechanism also affects how fast each surface region of a crystal grows. Empirical studies suggest less than 0.1% of snowflakes exhibit the ideal six-fold symmetric shape. Very occasionally twelve branched snowflakes are observed; they maintain the six-fold symmetry. Snowflakes form in a wide variety of intricate shapes, leading to the notion that "no two are alike". Although nearly-identical snowflakes have been made in laboratory, they are very unlikely to be found in nature. Initial
Bis(5'-nucleosyl)-tetraphosphatase (symmetrical) As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and . Bis(5'-nucleosyl)-tetraphosphatase (symmetrical) In enzymology, a bis(5'-nucleosyl)-tetraphosphatase (symmetrical) () is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are P1,P4-bis(5'-adenosyl) tetraphosphate and HO, whereas its product is ADP. This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is P1,P4-bis(5'-nucleosyl)-tetraphosphate nucleosidebisphosphohydrolase. Other names in common use include diadenosinetetraphosphatase (symmetrical), dinucleosidetetraphosphatasee (symmetrical), symmetrical diadenosine tetraphosphate hydrolase, adenosine tetraphosphate phosphodiesterase, Ap4A hydrolase, bis(5'-adenosyl)