The group’s results were published in the March 25 issue of Science, the nation’s premier science journal. Liu was lead author on the article, which was titled "Self-Recognition Among Different Polyprotic Macroions During Assembly Processes in Dilute Solution."

“Publication of this work in Science is important recognition of the research being conducted in Tianbo’s lab,” said Robert Flowers, department chair and professor of chemistry. “His ability to succeed at such a high level shows that first-rate science is being done at Lehigh.”
Liu’s group has spent several years exploring the fascinating solutions of large, soluble ions called macroions. The behavior of these ions is completely different from the behavior of small ions, such as sodium chloride.

Despite being water-soluble and carrying the same type of charge, macroions tend to attract each other with surprising strength, says Liu, and to form very stable, uniform, single-layered hollow spheres known as “blackberry structures.” The structures are common when ions become large, and they mimic some biological processes such as the virus capsid shell formation.

Forming two distinct blackberry structures

Exciting discoveries have been generated from blackberry solutions. Liu’s group found that, when mixed into the same solution, two different types of 2.5-nm spherical macroions ({Mo72Fe30} and {Mo72Cr30}) with almost identical size, shape and molecular structures tend to form two types of individual blackberries instead of mixed ones.

The macroions—Bucky ball-shaped inorganic compounds—were synthesized by a research team led by Achim Müller, professor of chemistry at the University of Bielefeld, Germany. Müller was a coauthor on the Science article.
This result, says Liu, suggests that even in dilute solutions these two macroions can self-recognize during assembly.

This level of “intelligence,” he adds, is usually believed to be achievable only by complex biological molecules. Self-recognition by large inorganic ions could lead to more opportunities for understanding the nature of biological interactions.

Liu’s group believes the self-recognition results from the very slow formation of the dimers in the first step of the assembly. The slow speed ensures the formation of dimers with the lowest free energy, such as A-A and B-B dimers.
The differences in charge density between the two types of macroions play an important role in the recognition, says Liu, as does their surface water mobility difference.

Source: PhysOrg