Biomedical Engineering Reference
In-Depth Information
FIGURE 12.7
Molecular recognition at the air-water interface: (a) ATP recognition, (b) thymine recogni-
tion, and (c) adenine recognition.
FAD molecule binds two guanidinium molecules at phosphate groups, one orotate molecule at
adenine sites, and diaminotriazine at isoalloxiazine ring [51]. Such multipoint binding of aqueous
biomolecule to Langmuir monolayer leads to a novel strategy for molecular pattern formation in a
two-dimensional 2-D plane, as illustrated in Figure 12.8 [52-54], where two kinds of amphiphiles,
guanidinium-amphiphile and orotate-amphiphile, were used for pattern formation (Figure 12.8A).
The monolayer transferred on a mica surface was observed by AFM. Repeated height differences
in the angstrom range were observed for the orotate or guanidinium-mixed monolayer transferred
from aqueous FAD solution as a resulting molecular pattern (Figure 12.8B). As illustrated in a
molecular model in Figure 12.8A, the binding of FAD with the orotate or guanidinium-mixed
monolayer would dispose two functional units at the same level, resulting in a height difference
between the two terminal methyl groups. The methodology to prepare artifi cial patterns in 2-D
planes has not been well developed so far, especially in molecular size, and the approach demon-
strated above would lead to develop novel fabrication in 2-D molecular patterning.
The formation of complicated recognition sites upon self-assemblies of several components is
a useful strategy for biomolecular hybridization. Similar concepts have been already accomplished
by biological polymers such as enzymes and antibodies. For example, the immune system can treat
numerous antigens by genetically tuning the recognition sites in antibodies. A variation of the amino
acid sequence in several small hypervariable regions provides diversity in antigen-binding sites.
