Molecular Interactions between Methylene Blue and Sodium Alginate Studied by Molecular Orbital Calculations

Pasika Temeepresertkij; Michio Iwaoka; Satoru Iwamori

doi:10.3390/molecules26227029

Molecular Interactions between Methylene Blue and Sodium Alginate Studied by Molecular Orbital Calculations

Molecules. 2021 Nov 21;26(22):7029. doi: 10.3390/molecules26227029.

Authors

Pasika Temeepresertkij¹, Michio Iwaoka², Satoru Iwamori¹

Affiliations

¹ Graduate School of Science and Technology, Tokai University, Hiratsuka 259-1292, Kanagawa, Japan.
² Department of Chemistry, Tokai University, Hiratsuka 259-1292, Kanagawa, Japan.

Abstract

A methylene blue (MB) indicator embedded in sodium alginate (SA) film was previously examined for detecting active oxygen species. In a previous study, spectrometry was used to identify and characterize the MB/SA complex. However, the decolorization mechanism was not fully assessed. In this study, our aim is to conduct computational calculations at the B3LYP/6-31G(d) level to clarify the exact types and positions of the interaction that cause the decolorization in MB. The results demonstrate that MB/SA interacts with carboxylates (-COO(superscript)-(superscript)) of SA and the N, C, and S atoms of MB, confirming previous experimental observations.

Keywords: binding affinity energy; interaction position; methylene blue; molecular orbital calculations; sodium alginate.