Relative binding energies of organic molecules to aluminum(+) ion in the gas phase

1982 ◽  
Vol 104 (5) ◽  
pp. 1235-1238 ◽  
Author(s):  
Jack S. Uppal ◽  
Ralph H. Staley
Keyword(s):  
Gas Phase ◽  
Organic Molecules ◽  
Binding Energies ◽  
Aluminum Ion ◽  
Relative Binding

Serine–Ca2+ versus serine–Cu2+ complexes — A theoretical perspective

2010 ◽  
Vol 88 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Al Mokhtar Lamsabhi ◽  
Otilia Mó ◽  
Manuel Yáñez
Keyword(s):  
Gas Phase ◽  
Electron Density ◽  
Potential Energy Surfaces ◽  
Metal Ion ◽  
Theoretical Perspective ◽  
Binding Energies ◽  
Interacting Systems ◽  
Intramolecular Hydrogen ◽  
Energy Surfaces ◽  
Doubly Charged

The association of Ca2+ and Cu2+ to serine was investigated by means of B3LYP DFT calculations. The [serine–M]2+ (M = Ca, Cu) potential energy surfaces include, as does the neutral serine, a large number of conformers, in which a drastic reorganization of the electron density of the serine moiety is observed. This leads to significant changes in the number and strength of the intramolecular hydrogen bonds existing in the neutral serine tautomers. In some cases, a proton is transferred from the carboxylic OH group to the amino group and accordingly, some of the more stable [serine–M]2+ complexes can be viewed as the result of the interaction of the zwiterionic form of serine with the doubly charged metal ion. Whereas the interaction between Ca2+ and serine is essentially electrostatic, that between Cu2+ and serine has a non-negligible covalent character, reflected in larger electron densities at the bond critical points between the metal and the base, in the negative values of the electron density between the two interacting systems, and in much larger Cu2+ than Ca2+ binding energies. More importantly, the interaction with Cu2+ is followed by a partial oxidation of the base, which is not observed when the metal ion is Ca2+. The main consequence is that in Cu2+ complexes a significant acidity enhancement of the serine moiety takes place, which strongly favors the deprotonation of the [serine–Cu]2+ complexes. This is not the case for Ca2+ complexes. Thus, [serine–Ca]2+ complexes, like those formed by urea, thiourea, selenourea, or glycine, should be detected in the gas phase. Conversely, the complexes with Cu2+ should deprotonate spontaneously and therefore only [(serine–H)–Cu]+ monocations should be experimentally accessible.

scholarly journals Electronic Spectroscopy of Isolated DNA Polyanions

2018 ◽  
Author(s):  
Steven Daly ◽  
Massimiliano Porrini ◽  
Frédéric Rosu ◽  
Valerie Gabelica
Keyword(s):  
Gas Phase ◽  
Absorption Spectra ◽  
Ion Mobility ◽  
Photoelectron Spectroscopy ◽  
Binding Energies ◽  
Action Spectroscopy ◽  
Action Spectra ◽  
Vis Spectroscopy ◽  
Electron Binding Energies ◽  
Electron Binding

In solution, UV-vis spectroscopy is often used to investigate structural changes in biomolecules (i.e., nucleic acids), owing to changes in the environment of their chromophores (i.e., the nucleobases). Here we address whether action spectroscopy could achieve the same for gas-phase ions, while taking the advantage of additional mass spectrometry and ion mobility separation of complex mixtures. We therefore systematically studied the action spectroscopy of homo-base 6-mer DNA strands (dG6, dA6, dC6, dT6), and discuss the results in light of gas-phase structures validated by ion mobility spectrometry and infrared ion spectroscopy, and in light of electron binding energies measured by photoelectron spectroscopy, and calculated electronic photo-absorption spectra. When UV photons interact with oligonucleotide polyanions, two main actions may take place: (1) fragmentation and (2) electron detachment. The action spectra reconstructed from fragmentation follow the absorption spectra well, and result from multiple cycles of absorption and internal conversion. The action spectra reconstructed from the electron photodetachment (EPD) efficiency reveal interesting phenomena: EPD depends on the charge state in a manner depending on electron binding energies, and is particularly efficient for purines but not pyrimidines. EPD thus reflects not only absorption, but also particular relaxation pathways of the electronic excited states. As these pathways lead to photo-oxidation, their investigation on model gas-phase systems may prove useful to elucidate mechanisms of photo-oxidative damages, which are linked to mutations and cancers.

Calixarene receptors of environmentally hazardous and biorelevant molecules and ions

2008 ◽  
Vol 80 (7) ◽  
pp. 1449-1458 ◽  
Author(s):  
Vitaly I. Kalchenko
Keyword(s):  
Drug Design ◽  
Gas Phase ◽  
Crystalline State ◽  
Rational Design ◽  
Organic Molecules ◽  
Supramolecular Complexes

In the paper, a report on the rational design of the calixarene receptors bearing ligating, H-donor, H-acceptor fragments at the wide and/or narrow rim of the macrocycle is presented. The calixarenes form supramolecular complexes with various cations, anions, organic molecules, and biomolecules in solution, in the crystalline state and even in the gas phase. The calixarenes or their complexes can be used as materials for radionuclide extraction, construction of chemosensors, and drug design.

scholarly journals Molecules in nearby and primordial supernovae

2008 ◽  
Vol 4 (S251) ◽  
pp. 221-226
Author(s):  
Isabelle Cherchneff ◽  
Simon Lilly
Keyword(s):  
Gas Phase ◽  
Early Universe ◽  
Organic Molecules ◽  
Molecular Form ◽  
Chemical Kinetic ◽  
Kinetic Approach ◽  
Dust Formation ◽  
Core Collapse ◽  
Chemical Models ◽  
Upper Limits

AbstractWe present new chemical models of supernova (SN) ejecta based on a chemical kinetic approach. We focus on the formation of inorganic and organic molecules including gas phase dust precursors, and consider zero-metallicity progenitor, massive supernovae and nearby core-collapse supernovae such as SN1987A. We find that both types are forming large amounts of molecules in their ejecta at times as early as 200 days after explosion. Upper limits on the dust formation budget are derived. Our results on dust precursors do not agree with existing studies on dust condensation in SN ejecta. We conclude that PMSNe could be the first non-primodial molecule providers in the early universe, ejecting up to 34% of their progenitor mass under molecular form to the pristine, local gas.

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