Paper accepted: “Unraveling the impact of acetylation patterns in chitosan oligomers on Cu2+ ion binding: insights from DFT calculations”

Today, Dr. Ratna Singh's manuscript on quantum mechanics based in depth in silico-analysis of copper ion binding to chitosan has been accepted for publication in the International Journal of Molecular Sciences. This paper has been long in the making, Ratna started working on the subject in the framework of the Indo-German Bioeconomy International project smartBioS in which we aimed to develop a synergistically acting combination of plant strengthening chitosans and antimicrobial copper ions. The ultimate goal is to reduce the amount of copper required to efficiently prevent fungal and oomycete diseases on crop plants, to protect the environment and the consumers from excessive copper residues in the soil and on the agricultural products. The combination, however, is not a trivial one, as chitosan can bind copper ions efficiently, leading to precipitation which can block nozzles of spraying equipment. Thus, it is essential to understand this interaction on a molecular and atomic level to be able to control it. Our idea was that the binding of a copper ion to a deacetylated glucosamine unit within the chitosan chain might be influenced by the acetylation status of the neighbouring units; in other words, that the binding affinity might be influenced by the acetylation pattern. Using sophisticated density functional theory, Ratna was now able to show that this is indeed the case! One more example that "patterns matter"! In fact, our calculations showed that the presence of an acetylated subunit in a chitosan affects the structural and electronic properties of the molecule by generating new intramolecular interactions with the free amino group of neighbouring deacetylated subunits, thereby influencing its polarity and explaining the influence on - and certainly far beyond! - copper binding.