The pH behavior of a 2-aminoethyl dihydrogen phosphate zwitterion studied with NMR-titrations

Hydrogen atoms in supramolecular chemistry: a structural perspective. Where are they, and why does it matter?

Hydrogen bonding interactions are ubiquitous across the biochemical and chemical sciences, and are of particular interest to supramolecular chemists. They have been used to assemble hydrogen bonded polymers, cages and frameworks, and are the functional motif in many host-guest systems. Single crystal X-ray diffraction studies are often used as a key support for proposed structures, although this presents challenges as hydrogen atoms interact only weakly with X-rays. In this Tutorial Review, we discuss the information that can be gleaned about hydrogen bonding interactions through crystallographic experiments, key limitations of the data, and emerging techniques to overcome these limitations.

The Influence of pH on Complexation Process of Copper(II) Phosphoethanolamine to Pyrimidine Nucleosides

The influence of pH on the complex formation of phosphoethanolamine and pyrimidine nucleosides (uridine, cytidine and thymidine) with copper(II) ions was studied. All investigations were performed in aqueous solution. The overall stability constants of the complexes and non-covalent compounds were obtained using the potentiometric method with computer calculation of the data. Moreover, equilibrium constants of the reaction were determined. The mode of coordination was obtained using spectroscopic methods. Analysis of the potentiometric and spectroscopic data confirmed the involvement and effectiveness of phosphate groups in species formation as well as the influence of pH on the mode of coordination of the investigated biomaterials. In the next step, studied complexes will be applied as potential biomaterials with biological applications.

An efficient and sensitive fluorescent pH sensor based on amino functional metal–organic frameworks in aqueous environment

In this work, an amino group functionalized MOF (Al-MIL-101-NH₂), which shows strong blue luminescence, is used as pH sensor. Due to the protonated amino group, the fluorescence intensity of Al-MIL-101-NH₂almost increases with increasing pH and gives a good linear relationship (R²= 0.99688) with the pH value.

Kinetic characterization of the human O-phosphoethanolamine phospho-lyase reveals unconventional features of this specialized pyridoxal phosphate-dependent lyase

Human O-phosphoethanolamine (PEA) phospho-lyase is a pyridoxal 5'-phosphate (PLP) dependent enzyme that catalyzes the degradation of PEA to acetaldehyde, phosphate and ammonia. Physiologically, the enzyme is involved in phospholipid metabolism and is expressed mainly in the brain, where its expression becomes dysregulated in the course of neuropsychiatric diseases. Mechanistically, PEA phospho-lyase shows a remarkable substrate selectivity, strongly discriminating against other amino compounds structurally similar to PEA. Herein, we studied the enzyme under steady-state and pre-steady-state conditions, analyzing its kinetic features and getting insights into the factors that contribute to its specificity. The pH dependence of the catalytic parameters and the pattern of inhibition by the product phosphate and by other anionic compounds suggest that the active site of PEA phospho-lyase is optimized to bind dianionic groups and that this is a prime determinant of the enzyme specificity towards PEA. Single- and multiple-wavelength stopped-flow studies show that upon reaction with PEA the main absorption band of PLP (λmax  = 412 nm) rapidly blue-shifts to ~ 400 nm. Further experiments suggest that the newly formed and rather stable 400-nm species most probably represents a Michaelis (noncovalent) complex of PEA with the enzyme. Accumulation of such an early intermediate during turnover is unusual for PLP-dependent enzymes and appears counterproductive for absolute catalytic performance, but it can contribute to optimize substrate specificity. PEA phospho-lyase may hence represent a case of selectivity-efficiency tradeoff. In turn, the strict specificity of the enzyme seems important to prevent inactivation by other amines, structurally resembling PEA, that occur in the brain.