Spectroscopic properties of dipicolinic acid and its dianion

Detection of anthrax biomarker and metallic ions in aqueous media using spherical-shaped lanthanide infinite coordination polymers

We report a lanthanide-based infinite coordination polymer (ICP) system synthesized using pyrazole-3,5-dicarboxylic acid as linker, malonic acid as coordination modulator and water as solvent. The precursors self-assembly into microspherical particles, which are water-stable and exhibit excellent dispersibility. Bimetallic samples based on Tb³⁺ doped with Eu³⁺ were investigated as ratiometric dipicolinic acid (DPA) sensors, which is a biomarker for Bacillus anthracis spores. Along with the calibration curves, a detection in a real sample extracted from Bacillus subtilis (model organism) was performed. The samples proved to be highly sensitive and selective for ratiometric DPA detection. In a secondary study, the monometallic sample containing only Tb³⁺ was also investigated as a sensor for ionic species in aqueous media. The Cr³⁺, Fe³⁺, Cu²⁺, and Cr₂O₇^2- ionic species could be detected in water by luminescence quenching mechanism. Therefore, we found that the reported ICP system can be judiciously constructed in order to act as a multimodal probe for several chemical species.

Synthesis, structure, spectroscopy of four novel supramolecular complexes and cytotoxicity study by application of multiple parallel perfused microbioreactors

Synthesis of four supramolecular complexes and study of their cytotoxicity using multiple parallel perfused microbioreactors.

Penetration of negatively charged lipid interfaces by the doubly deprotonated dipicolinate

The possibility that a negatively charged organic molecule penetrates the lipid interface in a reverse micellar system is examined using UV-vis absorption and NMR spectroscopy. The hypothesis that deprotonated forms of dipicolinic acid, H(2)dipic, such as Hdipic(-) and dipic(2-), can penetrate the lipid interface in a microemulsion is based on our previous finding that the insulin-enhancing anionic [VO(2)dipic](-) complex was found to reside in the hydrophobic layer of the reverse micelle (Crans et al. J. Am. Chem. Soc. 2006, 128, 4437-4445). Penetration of a polar and charged compound, namely Hdipic(-) or dipic(2-), into a hydrophobic environment is perhaps unexpected given the established rules regarding the fundamental properties of compound solubility. As such, this work has broad implications in organic chemistry and other disciplines of science. These studies required a comprehensive investigation of the different dipic species and their association in aqueous solutions at varying pH values. Combining the aqueous studies using absorption and NMR spectroscopy with those in microemulsions defines the differences observed in the heterogeneous environment. Despite the expected repulsion between the surfactant head groups and the dianionic probe molecule, these studies demonstrate that dipic resides deep in the hydrophobic portion of the reverse micellar interface. In summary, these results provide evidence that ionic molecules can reside in nonpolar locations in microheterogeneous environments. This suggests that additional factors such as solvation are important to molecule location. Documented ability to penetrate lipid surfaces of similar charge provides a rationale for why specific drugs with less than optimal hydrophobicity are successful even though they violate Lipinski's rules.

Effect of nuclear motion on the absorption spectrum of dipicolinic acid

Using semiclassical electron-radiation-ion dynamics, the authors have examined the effect of nuclear motion, resulting from both finite temperature and the response to a radiation field, on the line broadening of the excitation profile of 2,6-pyridinedicarboxylic acid (dipicolinic acid). With nuclei fixed, there is a relatively small broadening associated with the finite time duration of an applied laser pulse. When the nuclei are allowed to move, the excitation spectrum exhibits a much larger broadening, and is also reduced in height and shifted toward lower frequencies. In both cases, the excitation is due to well-defined pi to pi* transitions. The further inclusion of thermal motion at room temperature broadens the linewidth considerably because of variations in the molecular geometry: Transitions that had zero or negligible transition probabilities in the ground state geometry are weakly excited at room temperature.

Sensitive femtosecond coherent anti-Stokes Raman spectroscopy discrimination between dipicolinic acid and dinicotinic acid

We demonstrate that femtosecond ultraviolet and visible coherent anti-Stokes Raman spectroscopy provides the sensitivity and specificity needed to distinguish between two similar molecules of pyridinedicarboxylic acid. The Fourier transforms of the temporal measurements provide the energy difference between the ground state vibrational modes. Quantum chemical calculations provide theoretical predictions that agree well with the measurements. The present technique allows us to distinguish 10 cm(-1) frequency shifts by using pulses ten times broader than the shifts.