Oligonucleotides of adenine (A20), guanine (G20), cytosine
(C20),
thymine (T20), cytosine–guanine ((CG)20), and adenine–thymine
((AT)20) were investigated as model compounds for ice recrystallization
inhibition (IRI). Dehydroxy uracil (dU20), U20, and T20 were also
compared to investigate the effect of minute changes in the hydrophobicity
of the oligonucleotides on the IRI activity. Among the oligonucleotides
considered in this study, T20 exhibited the best performance for IRI.
In addition, the degree of polymerization of oligothymines varied
over 5, 10, 20, 30, 50, and 100, and T20 was found to be the most
effective for IRI. The IRI mechanism was investigated by comparing
U20 and T20, which exhibited the lowest and highest IRI activity,
respectively, among the oligonucleotides for their dynamic ice-shaping,
thermal hysteresis, and ice nucleation inhibition. Little or no dynamic
ice-shaping activity and small thermal hysteresis were observed for
both nucleotides. All of the findings suggest that not the ice–polymer
adhesion but the hydrophobic interactions of T20 in the interface
layer might interfere with the water deposition on the ice crystal
surfaces and contribute to the IRI activity of the T20 oligonucleotide.