Probing into methylene blue interaction with polyglutamic acid: Spectroscopic and molecular dynamics simulation studies

Poonam Mishra Chatterjee, Deepika Pandey Tiwari, Silpi Datta, Suman Chakrabarty, Ritu Raval, Ashok Kumar Dubey

Research output: Contribution to journalArticle


Polyglutamic acid (PGA) is an anionic biopolymer which is stained with methylene blue (MB) in agar or polyacrylamide gels for analysis. Polyglutamic acid identification involves a tedious extraction and analytical process. The molecular association of polyglutamic acid and methylene blue can be used for rapid spectroscopic detection of polyglutamic acid production during fermentation. This triggered the study on investigation of polymer-dye interaction mechanism. Concentration range of polyglutamic acid, 0.001 to 0.06 µM with a fixed methylene blue concentration of 25 µM exhibited significant differences in the spectra. Preferential higher order aggregate formation of methylene blue molecules was substantiated with molecular dynamics simulation results. Fluorescence spectroscopy demonstrated a quenching effect of polyglutamic acid on methylene blue fluorescence until a certain concentration range, beyond which the Stern-Volmer (SV) plot shows a negative deviation. Polyglutamic acid was observed to promote higher order of intramolecular stacking interactions of methylene blue, possibly due to interplay of electrostatic and hydrophobic interactions between polyglutamic acid, methylene blue alone and PGA-MB systems.

Original languageEnglish
Pages (from-to)1949-1958
Number of pages10
JournalAsian Journal of Chemistry
Issue number9
Publication statusPublished - 01-01-2019


All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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