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Deamer D. Perspective: Protocells and the Path to Minimal Life. J Mol Evol 2024; 92:530-538. [PMID: 39230713 PMCID: PMC11458682 DOI: 10.1007/s00239-024-10197-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 08/20/2024] [Indexed: 09/05/2024]
Abstract
The path to minimal life involves a series of stages that can be understood in terms of incremental, stepwise additions of complexity ranging from simple solutions of organic compounds to systems of encapsulated polymers capable of capturing nutrients and energy to grow and reproduce. This brief review will describe the initial stages that lead to populations of protocells capable of undergoing selection and evolution. The stages incorporate knowledge of chemical and physical properties of organic compounds, self-assembly of membranous compartments, non-enzymatic polymerization of amino acids and nucleotides followed by encapsulation of polymers to produce protocell populations. The results are based on laboratory simulations related to cyclic hydrothermal conditions on the prebiotic Earth. The final portion of the review looks ahead to what remains to be discovered about this process in order to understand the evolutionary path to minimal life.
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Affiliation(s)
- David Deamer
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA, USA.
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2
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Volosatova AD, Tyurin DA, Feldman VI. The Radiation Chemistry of NH 3···CO Complex in Cryogenic Media as Studied by Matrix Isolation. J Phys Chem A 2022; 126:3893-3902. [PMID: 35696324 DOI: 10.1021/acs.jpca.2c01774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The NH3···CO complex can be considered an important building block for cold synthetic astrochemistry leading to the formation of complex organic molecules, including key prebiotic species. In this work, we have studied the radiation-induced transformations of this complex in Ar, Kr, and Xe matrices using FTIR spectroscopy. On the basis of comparison with the quantum chemical calculations at the CCSD(T)/L2a_3 level of theory, it was found that the initial complex had the configuration with hydrogen bonding through the carbon atom of CO. Irradiation of the matrix isolated complex with X-rays at 6 K leads to the formation of a number of synthetic products, namely, HNCO (in all matrices), formamide NH2CHO, NH2CO, and HNCO-H2 (in argon and krypton). The matrix effect on the product distribution was explained by the involvement of different excited states of the complex in their formation. It was suggested that formamide results from the singlet excited states while other species mainly originate from triplet excited states. The latter states are efficiently populated through ion-electron recombination (in all matrices) and through intersystem crossing (particularly, in xenon). High yield of the recombination triplet states is a feature of the processes induced by high-energy radiation (in contrast to direct photolysis). NCO, CN, and NO were found as minor secondary products at high adsorbed doses. The astrochemical implications of the obtained results are discussed.
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Affiliation(s)
| | - Daniil A Tyurin
- Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Vladimir I Feldman
- Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
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3
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Baiano C, Lupi J, Barone V, Tasinato N. Gliding on Ice in Search of Accurate and Cost-Effective Computational Methods for Astrochemistry on Grains: The Puzzling Case of the HCN Isomerization. J Chem Theory Comput 2022; 18:3111-3121. [PMID: 35446575 PMCID: PMC9097295 DOI: 10.1021/acs.jctc.1c01252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Indexed: 11/28/2022]
Abstract
The isomerization of hydrogen cyanide to hydrogen isocyanide on icy grain surfaces is investigated by an accurate composite method (jun-Cheap) rooted in the coupled cluster ansatz and by density functional approaches. After benchmarking density functional predictions of both geometries and reaction energies against jun-Cheap results for the relatively small model system HCN···(H2O)2, the best performing DFT methods are selected. A large cluster containing 20 water molecules is then employed within a QM/QM' approach to include a realistic environment mimicking the surface of icy grains. Our results indicate that four water molecules are directly involved in a proton relay mechanism, which strongly reduces the activation energy with respect to the direct hydrogen transfer occurring in the isolated molecule. Further extension of the size of the cluster up to 192 water molecules in the framework of a three-layer QM/QM'/MM model has a negligible effect on the energy barrier ruling the isomerization. Computation of reaction rates by the transition state theory indicates that on icy surfaces, the isomerization of HNC to HCN could occur quite easily even at low temperatures thanks to the reduced activation energy that can be effectively overcome by tunneling.
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Affiliation(s)
- Carmen Baiano
- Scuola Normale Superiore, Piazza Dei Cavalieri 7, I-56126 Pisa, Italy
| | - Jacopo Lupi
- Scuola Normale Superiore, Piazza Dei Cavalieri 7, I-56126 Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza Dei Cavalieri 7, I-56126 Pisa, Italy
| | - Nicola Tasinato
- Scuola Normale Superiore, Piazza Dei Cavalieri 7, I-56126 Pisa, Italy
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4
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M Wallace A, C Fortenberry R. Computational UV spectra for amorphous solids of small molecules. Phys Chem Chem Phys 2021; 23:24413-24420. [PMID: 34693942 DOI: 10.1039/d1cp03255k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ices in the interstellar medium largely exist as amorphous solids composed of small molecules including ammonia, water, and carbon dioxide. Describing gas-phase molecules can be readily accomplished with current high-level quantum chemical calculations with the description of crystalline solids becoming more readily accomplished. Differently, amorphous solids require more novel approaches. The present work describes a method for generating amorphous structures and constructing electronic spectra through a combination of quantum chemical calculations and statistical mechanics. The structures are generated through a random positioning program and DFT methods, such as ωB97-XD and CAM-B3LYP. A Boltzmann distribution weights the excitations to compile a final spectrum from a sampling of molecular clusters. Three ice analogs are presented herein consisting of ammonia, carbon dioxide, and water. Ammonia and carbon dioxide provide semi-quantitative agreement with experiment for CAM-B3LYP/6-311++G(2d,2p) from 30 clusters of 8 molecules. Meanwhile, the amorphous water description improves when the sample size is increased in cluster size and count to as many as 105 clusters of 32 water molecules. The described methodology can produce highly comparative descriptions of electronic spectra for ice analogs and can be used to predict electronic spectra for other ice analogs.
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Affiliation(s)
- Austin M Wallace
- Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, USA.
| | - Ryan C Fortenberry
- Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, USA.
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5
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Khatri J, Roy TK, Chatterjee K, Schwaab G, Havenith M. Vibrational Spectroscopy of Benzonitrile-(Water) 1-2 Clusters in Helium Droplets. J Phys Chem A 2021; 125:6954-6963. [PMID: 34355893 DOI: 10.1021/acs.jpca.1c04553] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Polycyclic aromatic hydrocarbons are considered as primary carriers of the unidentified interstellar bands. The recent discovery of the first interstellar aromatic molecule, benzonitrile (C6H5CN), suggests a repository of aromatic hydrocarbons in the outer earth environment. Herein, we report an infrared (IR) study of benzonitrile-(D2O)n clusters using mass-selective detection in helium nanodroplets. In this work, we use isotopically substituted water, D2O, instead of H2O because of our restricted IR frequency range (2565-3100 cm-1). A comparison of the experimental and predicted spectra computed at the MP2/6-311++G(d,p) level of benzonitrile-(water)1-2 clusters reveals the formation of a unique local minimum structure, which was not detected in previous gas-phase molecular beam experiments. Here, the solvent water forms a nearly linear hydrogen bond (H-bond) with the nitrile nitrogen of benzonitrile, while the previously reported most stable cyclic H-bonded isomer is not observed. This can be rationalized by the stepwise aggregation process of precooled monomers. The addition of a second water molecule results in the formation of two different isomers. In one of the observed isomers, a H-bonded water chain binds linearly to the nitrile nitrogen similar to the monohydrated benzonitrile-water complex. In the other observed isomer, the water dimer forms a ring-type structure, where a H-bonded water dimer simultaneously interacts with the nitrile nitrogen and the adjacent ortho CH group. Finally, we compare the water-binding motif in the neutral benzonitrile-water complex with the corresponding positively and negatively charged benzonitrile-water monohydrates to comprehend the charge-induced alteration of the solvent binding motif.
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Affiliation(s)
- Jai Khatri
- Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Tarun Kumar Roy
- Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Kuntal Chatterjee
- Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Gerhard Schwaab
- Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Martina Havenith
- Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
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Lietard A, Mensa-Bonsu G, Verlet JRR. The effect of solvation on electron capture revealed using anion two-dimensional photoelectron spectroscopy. Nat Chem 2021; 13:737-742. [PMID: 33941903 DOI: 10.1038/s41557-021-00687-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 03/24/2021] [Indexed: 02/02/2023]
Abstract
The reaction of low-energy electrons with neutral molecules to form anions plays an important role in chemistry, being involved in, for example, various biological and astrochemical processes. However, key aspects of electron-molecule interactions, such as the effect of incremental solvation on the initially excited electronic resonances, remain poorly understood. Here two-dimensional photoelectron spectroscopy of anionic anthracene and nitrogen-substituted derivatives-solvated by up to five water molecules-reveals that for an incoming electron, resonances red-shift with increasing hydration; but for the anion, the excitation energies of the resonances remain essentially the same. These complementary points of view show that the observed onset of enhanced anion formation for a specific cluster size is mediated by a bound excited state of the anion. Our findings suggest that polycyclic aromatic hydrocarbons may be more efficient at electron capture than previously predicted with important consequences for the ionization fraction in dense molecular clouds.
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Affiliation(s)
- Aude Lietard
- Department of Chemistry, Durham University, Durham, UK
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Smith RS, Tylinski M, Kimmel GA, Kay BD. Crystallization kinetics of amorphous acetonitrile nanoscale films. J Chem Phys 2021; 154:144703. [PMID: 33858151 DOI: 10.1063/5.0045461] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We measure the isothermal crystallization kinetics of amorphous acetonitrile films using molecular beam dosing and reflection adsorption infrared spectroscopy techniques. Experiments on a graphene covered Pt(111) substrate revealed that the crystallization rate slows dramatically during long time periods and that the overall kinetics cannot be described by a simple application of the Avrami equation. The crystallization kinetics also have a thickness dependence with the thinner films crystallizing much slower than the thicker ones. Additional experiments showed that decane layers at both the substrate and vacuum interfaces can also affect the crystallization rates. A comparison of the crystallization rates for CH3CN and CD3CN films showed only an isotope effect of ∼1.09. When amorphous films were deposited on a crystalline film, the crystalline layer did not act as a template for the formation of a crystalline growth front. These overall results suggest that the crystallization kinetics are complicated, indicating the possibility of multiple nucleation and growth mechanisms.
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Affiliation(s)
- R Scott Smith
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - M Tylinski
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Greg A Kimmel
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Bruce D Kay
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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8
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Santoro G, Sobrado JM, Tajuelo-Castilla G, Accolla M, Martínez L, Azpeitia J, Lauwaet K, Cernicharo J, Ellis GJ, Martín-Gago JÁ. INFRA-ICE: An ultra-high vacuum experimental station for laboratory astrochemistry. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:124101. [PMID: 33379937 PMCID: PMC7116743 DOI: 10.1063/5.0027920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Laboratory astrochemistry aims at simulating, in the laboratory, some of the chemical and physical processes that operate in different regions of the universe. Amongst the diverse astrochemical problems that can be addressed in the laboratory, the evolution of cosmic dust grains in different regions of the interstellar medium (ISM) and its role in the formation of new chemical species through catalytic processes present significant interest. In particular, the dark clouds of the ISM dust grains are coated by icy mantles and it is thought that the ice-dust interaction plays a crucial role in the development of the chemical complexity observed in space. Here, we present a new ultra-high vacuum experimental station devoted to simulating the complex conditions of the coldest regions of the ISM. The INFRA-ICE machine can be operated as a standing alone setup or incorporated in a larger experimental station called Stardust, which is dedicated to simulate the formation of cosmic dust in evolved stars. As such, INFRA-ICE expands the capabilities of Stardust allowing the simulation of the complete journey of cosmic dust in space, from its formation in asymptotic giant branch stars to its processing and interaction with icy mantles in molecular clouds. To demonstrate some of the capabilities of INFRA-ICE, we present selected results on the ultraviolet photochemistry of undecane (C11H24) at 14 K. Aliphatics are part of the carbonaceous cosmic dust, and recently, aliphatics and short n-alkanes have been detected in situ in the comet 67P/Churyumov-Gerasimenko.
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Affiliation(s)
- Gonzalo Santoro
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Jesús. M. Sobrado
- Centro de Astrobiología (CAB, INTA-CSIC). Crta. de Torrejón a Ajalvir km4, E-28850, Torrejón de Ardoz, Madrid, Spain
| | - Guillermo Tajuelo-Castilla
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Mario Accolla
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Lidia Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Jon Azpeitia
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Koen Lauwaet
- IMDEA Nanociencia. Ciudad Universitaria de Cantoblanco, E-28049 Cantoblanco, Madrid, Spain
| | - José Cernicharo
- Instituto de Física Fundamental (IFF, CSIC). Group of Molecular Astrophysics. c/ Serrano 123, 28006 Madrid, Spain
| | - Gary J. Ellis
- Instituto de Ciencia y Tecnología de Polímeros (ICTP, CSIC). c/ Juan de la Cierva 3, E-28006 Madrid, Spain
| | - José Ángel Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
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Morrison SM, Hazen RM. An evolutionary system of mineralogy. Part II: Interstellar and solar nebula primary condensation mineralogy (>4.565 Ga). THE AMERICAN MINERALOGIST 2020; 105:1508-1535. [PMID: 33958805 PMCID: PMC8098038 DOI: 10.2138/am-2020-7447] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The evolutionary system of mineralogy relies on varied physical and chemical attributes, including trace elements, isotopes, solid and fluid inclusions, and other information-rich characteristics, to understand processes of mineral formation and to place natural condensed phases in the deep-time context of planetary evolution. Part I of this system reviewed the earliest refractory phases that condense at T > 1000 K within the turbulent expanding and cooling atmospheres of highly evolved stars. Part II considers the subsequent formation of primary crystalline and amorphous phases by condensation in three distinct mineral-forming environments, each of which increased mineralogical diversity and distribution prior to the accretion of planetesimals >4.5 billion years ago. INTERSTELLAR MOLECULAR SOLIDS (1)Varied crystalline and amorphous molecular solids containing primarily H, C, O, and N are observed to condense in cold, dense molecular clouds in the interstellar medium (10 < T < 20 K; P < 10-13 atm). With the possible exception of some nanoscale organic condensates preserved in carbonaceous meteorites, the existence of these phases is documented primarily by telescopic observations of absorption and emission spectra of interstellar molecules in radio, microwave, or infrared wavelengths. NEBULAR AND CIRCUMSTELLAR ICE (2)Evidence from infrared observations and laboratory experiments suggest that cubic H2O ("cubic ice") condenses as thin crystalline mantles on oxide and silicate dust grains in cool, distant nebular and circumstellar regions where T ~100 K. PRIMARY CONDENSED PHASES OF THE INNER SOLAR NEBULA (3)The earliest phase of nebular mineralogy saw the formation of primary refractory minerals that solidified through high-temperature condensation (1100 < T < 1800 K; 10-6 < P < 10-2 atm) in the solar nebula more than 4.565 billion years ago. These earliest mineral phases originating in our solar system formed prior to the accretion of planetesimals and are preserved in calcium-aluminum-rich inclusions, ultra-refractory inclusions, and amoeboid olivine aggregates.
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Affiliation(s)
- Shaunna M. Morrison
- Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U. S. A
| | - Robert M. Hazen
- Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U. S. A
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Abstract
Clathrate hydrates (CHs) are ubiquitous in earth under high-pressure conditions, but their existence in the interstellar medium (ISM) remains unknown. Here, we report experimental observations of the formation of methane and carbon dioxide hydrates in an environment analogous to ISM. Thermal treatment of solid methane and carbon dioxide-water mixture in ultrahigh vacuum of the order of 10-10 mbar for extended periods led to the formation of CHs at 30 and 10 K, respectively. High molecular mobility and H bonding play important roles in the entrapment of gases in the in situ formed 512 CH cages. This finding implies that CHs can exist in extreme low-pressure environments present in the ISM. These hydrates in ISM, subjected to various chemical processes, may act as sources for relevant prebiotic molecules.
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Chatterjee K, Dopfer O. Microhydration of PAH + cations: evolution of hydration network in naphthalene +-(H 2O) n clusters ( n ≤ 5). Chem Sci 2018; 9:2301-2318. [PMID: 29719704 PMCID: PMC5903421 DOI: 10.1039/c7sc05124g] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 01/24/2018] [Indexed: 12/15/2022] Open
Abstract
The interaction of polycyclic aromatic hydrocarbon molecules with water (H2O = W) is of fundamental importance in chemistry and biology. Herein, size-selected microhydrated naphthalene cation nanoclusters, Np+-W n (n ≤ 5), are characterized by infrared photodissociation (IRPD) spectroscopy in the C-H and O-H stretch range to follow the stepwise evolution of the hydration network around this prototypical PAH+ cation. The IRPD spectra are highly sensitive to the hydration structure and are analyzed by dispersion-corrected density functional theory calculations (B3LYP-D3/aug-cc-pVTZ) to determine the predominant structural isomers. For n = 1, W forms a bifurcated CH···O ionic hydrogen bond (H-bond) to two acidic CH protons of the bicyclic ring. For n ≥ 2, the formation of H-bonded solvent networks dominates over interior ion solvation, because of strong cooperativity in the former case. For n ≥ 3, cyclic W n solvent structures are attached to the CH protons of Np+. However, while for n = 3 the W3 ring binds in the CH···O plane to Np+, for n ≥ 4 the cyclic W n clusters are additionally stabilized by stacking interactions, leading to sandwich-type configurations. No intracluster proton transfer from Np+ to the W n solvent is observed in the studied size range (n ≤ 5), because of the high proton affinity of the naphthyl radical compared to W n . This is different from microhydrated benzene+ clusters, (Bz-W n )+, for which proton transfer is energetically favorable for n ≥ 4 due to the much lower proton affinity of the phenyl radical. Hence, because of the presence of polycyclic rings, the interaction of PAH+ cations with W is qualitatively different from that of monocyclic Bz+ with respect to interaction strength, structure of the hydration shell, and chemical reactivity. These differences are rationalized and quantified by quantum chemical analysis using the natural bond orbital (NBO) and noncovalent interaction (NCI) approaches.
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Affiliation(s)
- Kuntal Chatterjee
- Institut für Optik und Atomare Physik , Technische Universität Berlin , Hardenbergstr. 36 , 10623 Berlin , Germany . ; Tel: +49 30 31423018
| | - Otto Dopfer
- Institut für Optik und Atomare Physik , Technische Universität Berlin , Hardenbergstr. 36 , 10623 Berlin , Germany . ; Tel: +49 30 31423018
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Dworkin J, Deamer D, Sandford S, Allamandola L. Self-assembling amphiphilic molecules: Synthesis in simulated interstellar/precometary ices. Proc Natl Acad Sci U S A 2001; 98:815-9. [PMID: 11158552 PMCID: PMC14665 DOI: 10.1073/pnas.98.3.815] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interstellar gas and dust constitute the primary material from which the solar system formed. Near the end of the hot early phase of star and planet formation, volatile, less refractory materials were transported into the inner solar system as comets and interplanetary dust particles. Once the inner planets had sufficiently cooled, late accretionary infall seeded them with complex organic compounds [Oró, J. (1961) Nature (London) 190, 389-390; Delsemme, A. H. (1984) Origins Life 14, 51-60; Anders, E. (1989) Nature (London) 342, 255-257; Chyba, C. F. & Sagan, C. (1992) Nature (London) 355, 125-131]. Delivery of such extraterrestrial compounds may have contributed to the organic inventory necessary for the origin of life. Interstellar ices, the building blocks of comets, tie up a large fraction of the biogenic elements available in molecular clouds. In our efforts to understand their synthesis, chemical composition, and physical properties, we report here that a complex mixture of molecules is produced by UV photolysis of realistic, interstellar ice analogs, and that some of the components have properties relevant to the origin of life, including the ability to self-assemble into vesicular structures.
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Affiliation(s)
- J Dworkin
- Astrochemistry Laboratory, National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035-1000, USA
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