Evidence for Potassium-Sucrose Interaction in Biological Mid-Infrared Spectra by Multidimensional Analysis

Complex-formation between carbohydrates and cations could have important biological implications. In this work, Mid-Infrared spectra of pure sucrose solutions and of biological solutions containing sucrose and potassium ions (K+) were investigated by Principal Component Analysis (PGA). By direct examination of the Mid-Infrared spectra of the biological solutions containing K+ ions, no interactions between the cations and sucrose molecules could be observed. However, when the spectral pattern obtained by PCA and which is associated with sucrose, was examined, splitting and shifts in the characteristic absorption bands were observed owing to interactions between sucrose molecules and K+ ions. The 997 cm-1 peak which had a visible shoulder at 991 cm-1 and that is observed in pure solutions, was decomposed in the biological solutions into 3 distinct peaks at 1004, 996 and 990 cm-1. The two peaks centered at 1053 cm-1 were split into 3 peaks: 1060, 1051, 1045 cm-1. Hence by PCA, shoulders were characterized in biological solutions and more distinct peaks could be observed. These split and shift phenomena are similar to those obtained when crystalline sugar salts were investigated. This type of interaction, involving potassium ions and sucrose molecules, would be responsible for the storage of this cation which role is essential in plant metabolism.