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Journal ArticleDOI: 10.1021/ACS.JPCLETT.1C00258

Condensation Effects on Electron Chiral Asymmetries in the Photoionization of Serine: From Free Molecules to Nanoparticles

04 Mar 2021-Journal of Physical Chemistry Letters (American Chemical Society)-Vol. 12, Iss: 9, pp 2385-2393
Abstract: Structural changes at the molecular level, occurring at the onset of condensation, can be probed by angle-resolved valence photoelectron spectroscopy, which is inherently sensitive to the electroni...

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Topics: Photoionization (58%), Valence (chemistry) (56%), Condensation (51%)

6 results found

Open accessJournal ArticleDOI: 10.1002/ANIE.202107150
Peter Krüger1, Karl-Michael Weitzel1Institutions (1)
16 Jun 2021-Angewandte Chemie
Abstract: The chirality of chemical compounds is of undisputed importance in science and technology. In particular with respect to pharmacological application most molecules of interest cannot be accessed by the powerful techniques developed in recent years for gas phase analytes. Here, we demonstrate that the combination of electrospray ionization (ESI) with the detection of photoelectron circular dichroism (PECD) provides access to chirality information applicable to molecular materials with negligible vapor pressure, for example, amino acids. To this end, glutamic acid and 3,4-dihydroxyphenylalanine (DOPA) have been electrosprayed into the source of a chirality spectrometer, where photodetachment is enforced and the PECD is detected. The technique can be expected to be conceptually applicable to all chemical systems with chirality based on molecular properties.

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2 Citations

Open accessJournal ArticleDOI: 10.1021/ACS.JPCLETT.1C01383
Abstract: The properties of aerosols are of paramount importance in atmospheric chemistry and human health. The hydrogen bond network of glycerol-water aerosols generated from an aqueous solution with different mixing ratios is probed directly with X-ray photoelectron spectroscopy. The carbon and oxygen X-ray spectra reveal contributions from gas and condensed phase components of the aerosol. It is shown that water suppresses glycerol evaporation up to a critical mixing ratio. A dielectric analysis using terahertz spectroscopy coupled with infrared spectroscopy of the bulk solutions provides a picture of the microscopic heterogeneity prevalent in the hydrogen bond network when combined with the photoelectron spectroscopy analysis. The hydrogen bond network is composed of three intertwined regions. At low concentrations, glycerol molecules are surrounded by water forming a solvated water network. Adding more glycerol leads to a confined water network, maximizing at 22 mol %, beyond which the aerosol resembles bulk glycerol. This microscopic view of hydrogen bonding networks holds promise in probing evaporation, diffusion dynamics, and reactivity in aqueous aerosols.

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Topics: Aqueous solution (55%), Hydrogen bond (54%), Molecule (53%) ... read more

2 Citations

Open accessJournal ArticleDOI: 10.1038/S42004-021-00508-Z
20 May 2021-
Abstract: Proline is a unique amino-acid, with a secondary amine fixed within a pyrrolidine ring providing specific structural properties to proline-rich biopolymers. Gas-phase proline possesses four main H-bond stabilized conformers differing by the ring puckering and carboxylic acid orientation. The latter defines two classes of conformation, whose large ionization energy difference allows a unique conformer-class tagging via electron spectroscopy. Photoelectron circular dichroism (PECD) is an intense chiroptical effect sensitive to molecular structures, hence theorized to be highly conformation-dependent. Here, we present experimental evidence of an intense and striking conformer-specific PECD, measured in the vacuum ultraviolet (VUV) photoionization of proline, as well as a conformer-dependent cation fragmentation behavior. This finding, combined with theoretical modeling, allows a refinement of the conformational landscape and energetic ordering, that proves inaccessible to current molecular electronic structure calculations. Additionally, astrochemical implications regarding a possible link of PECD to the origin of life’s homochirality are considered in terms of plausible temperature constraints. Proline plays an important role in determining the structures of proteins and peptides, but the conformer landscape of proline is still not fully mapped. Here, the authors show the conformer-specific cation fragmentation and photoelectron circular dichroism of proline during its vacuum ultraviolet photoionization.

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Topics: Circular dichroism (52%), Photoionization (51%), Homochirality (51%) ... read more

1 Citations

Journal ArticleDOI: 10.1039/D1CP02921E
Abstract: Chiral transition-metal complexes are of interest in many fields ranging from asymmetric catalysis and molecular materials science to optoelectronic applications or fundamental physics including parity violation effects. We present here a combined theoretical and experimental investigation of gas-phase valence-shell photoelectron circular dichroism (PECD) on the challenging open-shell ruthenium(iii)-tris-(acetylacetonato) complex, Ru(acac)$_3$. Enantiomerically pure $\Delta$- or $\Lambda$-Ru(acac)$_3$, characterized by electronic circular dichroism (ECD), were vaporized and adiabatically expanded to produce a supersonic beam and photoionized by circularly-polarized VUV light from the DESIRS beamline at Synchrotron SOLEIL. Photoelectron spectroscopy (PES) and PECD experiments were conducted using a double imaging electron/ion coincidence spectrometer, and compared to density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The open-shell character of Ru(acac)$_3$, which is not taken into account in our DFT approach, is expected to give rise to a wide multiplet structure, which is not resolved in our PES signals but whose presence might be inferred from the additional striking features observed in the PECD curves. Nevertheless, the DFT-based assignment of the electronic bands leads to the characterisation of the ionized orbitals. In line with other recent works, the results confirm that PECD persists independently on the localization and/or on the achiral or chiral nature of the initial orbital, but is rather a probe of the molecular potential as a whole. Overall, the measured PECD signals on Ru(acac)$_3$, a system exhibiting D$_3$ propeller-type chirality, are of similar magnitude compared to those on asymmetric-carbon-based chiral organic molecules which constitute the vast majority of species investigated so far, thus suggesting that PECD is a universal mechanism, inherent to any type of chirality.

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72 results found

Journal ArticleDOI: 10.1063/1.1807578
Abstract: We present an inversion method called pBasex aimed at reconstructing the original Newton sphere of expanding charged particles from its two-dimensional projection by fitting a set of basis functions with a known inverse Abel integral. The basis functions have been adapted to the polar symmetry of the photoionization process to optimize the energy and angular resolution while minimizing the CPU time and the response to the cartesian noise that could be given by the detection system. The method presented here only applies to systems with a unique axis of symmetry although it can be adapted to overcome this restriction. It has been tested on both simulated and experimental noisy images and compared to the Fourier-Hankel algorithm and the original Cartesian basis set used by [Dribinski et al.Rev. Sci. Instrum. 73, 2634 (2002)], and appears to give a better performance where odd Legendre polynomials are involved, while in the images where only even terms are present the method has been shown to be faster and simpler without compromising its accuracy.

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Topics: Basis function (59%), Legendre polynomials (53%), Cartesian coordinate system (52%) ... read more

537 Citations

Journal ArticleDOI: 10.1107/S0909049512010588
Abstract: DESIRS is a new undulator-based VUV beamline on the 2.75 GeV storage ring SOLEIL (France) optimized for gas-phase studies of molecular and electronic structures, reactivity and polarization-dependent photodynamics on model or actual systems encountered in the universe, atmosphere and biosphere. It is equipped with two dedicated endstations: a VUV Fourier-transform spectrometer (FTS) for ultra-high-resolution absorption spectroscopy (resolving power up to 106) and an electron/ion imaging coincidence spectrometer. The photon characteristics necessary to fulfill its scientific mission are: high flux in the 5–40 eV range, high spectral purity, high resolution, and variable and well calibrated polarizations. The photon source is a 10 m-long pure electromagnetic variable-polarization undulator producing light from the very near UV up to 40 eV on the fundamental emission with tailored elliptical polarization allowing fully calibrated quasi-perfect horizontal, vertical and circular polarizations, as measured with an in situ VUV polarimeter with absolute polarization rates close to unity, to be obtained at the sample location. The optical design includes a beam waist allowing the implementation of a gas filter to suppress the undulator high harmonics. This harmonic-free radiation can be steered toward the FTS for absorption experiments, or go through a highly efficient pre-focusing optical system, based on a toroidal mirror and a reflective corrector plate similar to a Schmidt plate. The synchrotron radiation then enters a 6.65 m Eagle off-plane normal-incidence monochromator equipped with four gratings with different groove densities, from 200 to 4300 lines mm−1, allowing the flux-to-resolution trade-off to be smoothly adjusted. The measured ultimate instrumental resolving powers are 124000 (174 µeV) around 21 eV and 250000 (54 µeV) around 13 eV, while the typical measured flux is in the 1010–1011 photons s−1 range in a 1/50000 bandwidth, and 1012–1013 photons s−1 in a 1/1000 bandwidth, which is very satisfactory although slightly below optical simulations. All of these features make DESIRS a state-of-the-art VUV beamline for spectroscopy and dichroism open to a broad scientific community.

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Topics: Undulator (57%), Beamline (54%), Monochromator (53%) ... read more

250 Citations

Journal ArticleDOI: 10.1038/NATURE03306
10 Feb 2005-Nature
Abstract: A comparison of corresponding sets of proteins encoded by closely related genes from organisms representing all three domains of life (Bacteria, Archaea and Eukaryota) suggests that the order in which the genetic code was assembled over 3.5 billion years ago continues to influence the evolution of proteins today. Across these diverse genomes, evolving proteins have accumulated Cys, Met, His, Ser and Phe, and lost many of their Pro, Ala, Glu and Gly residues. The same nine amino acids are currently accrued or lost in human proteins as shown by analysis of nucleotide polymorphisms. The amino acids with declining frequencies were probably among the first incorporated into the genetic code, and most of those with increasing frequencies were probably recruited late. Amino acid composition of proteins varies substantially between taxa and, thus, can evolve. For example, proteins from organisms with (G + C)-rich (or (A + T)-rich) genomes contain more (or fewer) amino acids encoded by (G + C)-rich codons1,2,3,4. However, no universal trends in ongoing changes of amino acid frequencies have been reported. We compared sets of orthologous proteins encoded by triplets of closely related genomes from 15 taxa representing all three domains of life (Bacteria, Archaea and Eukaryota), and used phylogenies to polarize amino acid substitutions. Cys, Met, His, Ser and Phe accrue in at least 14 taxa, whereas Pro, Ala, Glu and Gly are consistently lost. The same nine amino acids are currently accrued or lost in human proteins, as shown by analysis of non-synonymous single-nucleotide polymorphisms. All amino acids with declining frequencies are thought to be among the first incorporated into the genetic code; conversely, all amino acids with increasing frequencies, except Ser, were probably recruited late5,6,7. Thus, expansion of initially under-represented amino acids, which began over 3,400 million years ago8,9, apparently continues to this day.

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Topics: Amino acid (59%), Genetic code (55%)

245 Citations

Journal ArticleDOI: 10.1080/07391102.2004.10506975
Edward N. Trifonov1Institutions (1)
Abstract: Temporal order (“chronology”) of appearance of amino acids and their respective codons on evolutionary scene is reconstructed. A consensus chronology of amino acids is built on the basis of 60 different criteria each offering certain temporal order. After several steps of filtering the chronology vectors are averaged resulting in the consensus order: G, A, D, V, P, S, E, (L, T), R, (I, Q, N), H, K, C, F, Y, M, W. It reveals two important features: the amino acids synthesized in imitation experiments of S. Miller appeared first, while the amino acids associated with codon capture events came last. The reconstruction of codon chronology is based on the above consensus temporal order of amino acids, supplemented by the stability and complementarity rules first suggested by M. Eigen and P. Schuster, and on the earlier established processivity rule. At no point in the reconstruction the consensus amino-acid chronology was in conflict with these three rules. The derived genealogy of all 64 codons sugge...

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210 Citations

Uwe J. Meierhenrich1Institutions (1)
01 Jan 2008-
Abstract: ‘How did life start on Earth?’ and ‘Why were left-handed amino acids selected for the architecture of proteins?’ A new attempt to answer these questions of high public and interdisciplinary scientific interest will be provided by this review. It will describe most recent experimental data on how the basic and molecular building blocks of life, amino acids, formed in a prebiotic setting. Most amino acids are chiral, that is that they cannot be superimposed with their mirror image molecules (enantiomers). In processes triggering the origin of life on Earth, the equal occurrence, i.e. the parity between left-handed amino acids and their right-handed mirror images, was violated. In the case of amino acids, the balance was tipped to the left – as a result of which life's proteins today exclusively implement the left-handed form of amino acids, called l-amino acid enantiomers. Neither plants, nor animals, including humans, make use of d-amino acids for the molecular architecture of their proteins (enzymes). This review addresses the molecular asymmetry of amino acids in living organisms, namely the preference for left-handedness. What was the cause for the violation of molecular parity of amino acids in the emergence of life on Earth? All the fascinating models proposed by physicists, chemists, and biologists will be vividly presented including the scientific conflicts. Special emphasis will be given to amino acid enantiomers that were subjected to chiral photons. The interaction between racemic molecules and chiral photons was shown to produce an enantiomeric enrichment that will be discussed in the context of absolute asymmetric synthesis. The concluding paragraphs will describe the attempt to verify any of those models with the chirality-module of the Rosetta mission. This European space mission contains probe Philae that was launched on board the Rosetta spacecraft with the aim of landing on the icy surface of comet 67P/Churyumov-Gerasimenko and analysing whether chiral organic compounds are present that could have been brought to the Earth by comet impacts.

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Topics: Molecular asymmetry (56%)

209 Citations

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