Merck

Progressive fuzzy cation-π assembly of biological catecholamines.

Science advances (2018-09-12)
Seonki Hong, Younseon Wang, Sung Young Park, Haeshin Lee
ABSTRACT

Biological functions depend on biomolecular assembly processes. Assemblies of lipid bilayers, actins, microtubules, or chromosomes are indispensable for cellular functions. These hierarchical assembly processes are reasonably predictable by understanding chemical structures of the defined building blocks and their interactions. However, biopigment assembly is rather fuzzy and unpredictable because a series of covalently coupled intermediates from catecholamine oxidation pathways progressively form a higher-level hierarchy. This study reports a different yet unexplored type of assembly process named "cation-π progressive assembly." We demonstrated for the first time that the cation-π is the primary mechanism for intermolecular assembly in dopamine-melanin biopigment. We also found that the self-assembled products physically grow and chemically gain new functions "progressively" over time in which cation-π plays important roles. The progressive assembly explains how biological systems produce wide spectra of pigment colors and broad wavelength absorption through energy-efficient processes. Furthermore, we also demonstrate surface-independent wettability control using cation-π progressive assembly.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Potassium hydroxide, ≥85% KOH basis, pellets, white
Sigma-Aldrich
Dopamine hydrochloride
Sigma-Aldrich
Potassium chloride, BioXtra, ≥99.0%
Sigma-Aldrich
Tetramethylammonium chloride, reagent grade, ≥98%
Sigma-Aldrich
Melamine, 99%