OKANO Teruo    Department   Research Institutes and Facilities, Research Institutes and Facilities    Position
Article types	Original article
Language	English
Peer review	Peer reviewed
Title	Temperature-responsive molecular recognition chromatography using phenylalanine and tryptophan derived polymer modified silica beads.
Journal	Formal name：The Analyst Abbreviation：Analyst ISSN code：13645528/00032654
Domestic / Foregin	Foregin
Volume, Issue, Page	141(3),pp.910-917
Author and coauthor	HIRUTA Yuki†, KANAZASHI Ryosuke, AYANO Eri, OKANO Teruo, KANAZAWA Hideko*
Publication date	2016/02
Summary	Temperature-responsive polymers incorporating molecular-recognition sites were developed as stationary phases for high-performance liquid chromatography (HPLC). The grafted stationary phases consisted of functional copolymers composed of N-isopropylacrylamide (NIPAAm) and N-acryloyl aromatic amino acid methyl esters, i.e., phenylalanine and tryptophan methyl esters (Phe-OMe and Trp-OMe). Three novel temperature-responsive polymers, P(NIPAAm-co-Phe-OMe5), P(NIPAAm-co-Phe-OMe10), and P(NIPAAm-co-Trp-OMe5), were synthesized. These copolymers exhibited a reversible hydrophilic/hydrophobic phase transition at their lower critical solution temperatures (LCSTs). The polymers were grafted onto aminopropyl silica using an activated ester-amine coupling method, and were packed into a stainless steel column, which was connected to an HPLC system. Temperature-responsive chromatography was conducted using water as the sole mobile phase. More hydrophobic analytes were retained longer, and the retention times of aromatic steroids and aromatic amino acids were dramatically increased. This indicated that π-π interactions occurred between the phenyl or indole moieties of phenylalanine or tryptophan, respectively, and the aromatic compounds. Furthermore, the retention times of compounds with hydrogen bond acceptors were higher with P(NIPAAm-co-Trp-OMe5), which contained indole as a hydrogen bond donor, than with P(NIPAAm-co-Phe-OMe5). This indicated that hydrogen bonding occurred between the stationary phase and the analytes. These results indicate that hydrophobic, π-π, and hydrogen bonding interactions all affected the separation mode of the temperature-responsive chromatography, and led to selective separation with molecular recognition. Both temperature-response and molecular recognition characteristics are present in the proposed separation system that utilizes a temperature-responsive polymer bearing aromatic amino acid derivatives.
DOI	10.1039/c5an01996f
PMID	26646169