Affinity of Smectite and Divalent Metal Ions (Mg(2+), Ca(2+), Cu(2+)) with L-leucine: An Experimental and Theoretical Approach Relevant to Astrobiology.

Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg(2+), Ca(2+) and Cu(2+)) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu(2+)- exchanged SMT and minimal affinity for Mg(2+)- exchanged SMT. The vibrational frequency shifts of -NH3 (+) and -COO(-) favor Van der Waal's forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu-M(2+) complex, M = Mg(2+), Ca(2+), Cu(2+)) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu-M(2+) × (H2O)n, (n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of biomarkers.

Evaluation of trace element contents in Swertia paniculata Wall..

Important mineral elements (Fe, Zn, Mn, Cu, Co, Na, K, Ca and Li) were determined in the leaves and roots of Swertia paniculata collected from three different altitudes in three seasons using atomic absorption spectroscopy. The highest concentrations of Zn, Cu, Mn, Fe, Co, Na, K, Ca and Li were found to be 193.0 ± 5.6, 26.0 ± 7.6, 303.0 ± 8.5, 1507.0 ± 2.5, 88.0 ± 1.2, 345.0 ± 1.2, 11622.0 ± 6.4, 3461.0 ± 3.5 and 48.0 ± 4.5 mg kg(-1), respectively. The overall concentration of K was found to be the highest, whereas the level of Cu was the lowest. The concentrations of Cu and Li were quite low in all samples, whereas Zn, Mn, Co and Na were found in moderate concentration and K, Ca and Fe were found in very high concentrations in all the samples tested.