Table of Contents
Journal of Amino Acids
Volume 2014 (2014), Article ID 434056, 10 pages
http://dx.doi.org/10.1155/2014/434056
Research Article

Low-Vacuum Deposition of Glutamic Acid and Pyroglutamic Acid: A Facile Methodology for Depositing Organic Materials beyond Amino Acids

1School of Computer Science, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan
2Graduate School of Bionics, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan
3Shiseido Co., Ltd., Higashi-shimbashi, Minato-ku, Tokyo 105-8310, Japan
4Bionanotechnology Center, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan
5Faculty of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan

Received 30 May 2014; Revised 14 July 2014; Accepted 24 July 2014; Published 1 September 2014

Academic Editor: Sambasivarao Kotha

Copyright © 2014 Iwao Sugimoto et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Thin layers of pyroglutamic acid (Pygl) have been deposited by thermal evaporation of the molten L-glutamic acid (L-Glu) through intramolecular lactamization. This deposition was carried out with the versatile handmade low-vacuum coater, which was simply composed of a soldering iron placed in a vacuum degassing resin chamber evacuated by an oil-free diaphragm pump. Molecular structural analyses have revealed that thin solid film evaporated from the molten L-Glu is mainly composed of L-Pygl due to intramolecular lactamization. The major component of the L-Pygl was in -phase and the minor component was in -phase, which would have been generated from partial racemization to DL-Pygl. Electron microscopy revealed that the L-Glu-evaporated film generally consisted of the 20 nm particulates of Pygl, which contained a periodic pattern spacing of 0.2 nm intervals indicating the formation of the single-molecular interval of the crystallized molecular networks. The DL-Pygl-evaporated film was composed of the original DL-Pygl preserving its crystal structures. This methodology is promising for depositing a wide range of the evaporable organic materials beyond amino acids. The quartz crystal resonator coated with the L-Glu-evaporated film exhibited the pressure-sensing capability based on the adsorption-desorption of the surrounding gas at the film surface.