Self-similar patterns from abiotic decarboxylation metabolism through chemically oscillating reactions: a prebiotic model for the origin of life

The origin of life must have included an abiotic stage of carbon redox reactions that involved electron transport chains and the production of lifelike patterns. Chemically oscillating reactions (COR) are abiotic, spontaneous, out-of-equilibrium, and redox reactions that involve the decarboxylation of carboxylic acids with strong oxidants and strong acids to produce CO2 and characteristic self-similar patterns. Those patterns have circular concentricity, radial geometries, characteristic circular twins, colour gradients, cavity structures, and branching to parallel alignment. We propose that COR played a role during the prebiotic cycling of carboxylic acids, furthering the new model for geology where COR can also explain the patterns of diagenetic spheroids in sediments. The patterns of COR in Petri dishes are first considered and compared to those observed in some eukaryotic lifeforms. The molecular structures and functions of reactants in COR are then compared to key biological metabolic processes. We conclude that the newly recognised similarities in compositions and patterns warrant future research to better investigate the role of halogens in biochemistry; COR in life-forms, including in humans; and the COR-stage of prebiotic carbon cycling on other planets, such as Mars

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Structural and Spectroscopic Characterization of Hydantoins, Investigation of their Thermal Properties, and of their Photochemistry in Cryogenic Matrices

In this Thesis, the structural and vibrational study of 1-methylhydantoin (1-MH, C4H6N2O2), 5- methylhydantoin (5-MH, C4H6N2O2), and 5-hydantoin acetic acid (5-HAA, C5H6N2O4) was performed by matrix isolation infrared (IR) spectroscopy (in argon matrix; 10 K), complemented by quantum chemical calculations performed at the DFT (B3LYP)/6-311++G(d,p) level of approximation. The theoretical calculations yielded the Cs symmetry for 1-MH and the C1 symmetry for 5-MH and 5-HAA minimum energy structures on the ground state potential energy surfaces of the molecules. The electronic structure of these minimum energy species were then studied by means of the natural bond orbital (NBO) approach, allowing the elucidation of the main characteristics of the σ and π electronic systems of the molecules. The IR spectra of the matrix-isolated 1-MH, 5-MH and 5-HAA were fully assigned, also with the help of the theoretically predicted spectra of the compounds. The UV-induced photochemistry (λ ≥ 230 nm) of the 1-MH matrix-isolated monomer was also studied. The 1-MH molecule was found into fragment to carbon monoxide, isocyanic acid, N-methyl-methylenimine and methylenimine, via two different reaction pathways. The investigation of the thermal properties of 1-MH, 5-MH and 5-HAA was undertaken by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM) and infrared and Raman spectroscopies. A new polymorph of 1-MH was identified and characterized structurally for the first time by single crystal X-ray diffraction. Four different polymorph of 5-MH were identified and characterized spectroscopically by Raman spectroscopy. PLTM experiments allowed the observation of five different polymorphs of 5-HAA, four of them being characterized by Raman spectroscopy. Finally, three novel coordination complexes of 1-MH were synthesized. The different types of bonds between the metal ion and the 1-MH ligand were investigated and identified by Raman spectroscopy, and found to be in agreement with the HSAB principle.Neste trabalho foi realizado o estudo estrutural e vibracional da 1-metil-hidantoína (1-MH, C4H6N2O2), 5-metil-hidantoína (5-MH, C4H6N2O2), e 5-carboximetil-hidantoína (5-HAA, C5H6N2O4) por espectroscopia de infravermelho com isolamento em matriz (matriz de árgon; 10 K) complementado por cálculos de química quântica DFT (B3LYP)/6-311++G(d,p). Os cálculos teóricos apresentaram a simetria Cs para 1-MH e a simteria C1 para 5-MH e 5-HAA como as estruturas de energia mínima na superfície de energia potencial destas moléculas. As estruturas electrónicas destes mínimos energéticos de cada moléula foram estudadas em detalhe por análise das suas orbitais naturais de ligação, permitindo a caracterização dos seus sistemas electrónicos σ e π. As atribuições completas dos espectros de infravermelho das moléculas 1-MH, 5-MH e 5-HAA foram feitas com a ajuda dos espectros dos compostos previstos teoricamente. A fotoquímica induzida por UV (λ ≥ 230 nm) dos monómeros da 1-MH também foi estudada. Foi constatado que a molécula da 1-MH se fragmenta em monóxido de carbono, ácido isociânico, N-metilmetilenimina e em metilenimina por dois caminhos de reacção diferentes. A investigação das propriedades térmicas dos três compostos foi realizada por calorimetria diferencial de varrimento (DSC), termomicroscopia da luz polarizada (PLTM) e espectroscopias de infravermelho e de Raman. Foi identificada uma nova forma polimórfica do composto 1-MH, que foi caracterizada estruturalmente pela primeira vez por difração de raios-X de monocristal. Foram também identificados quatro polimorfos diferentes da 5-MH, tendo sido caracterizados por spectroscopia de Raman. Por último, por PLTM foi possível observar a existência de cinco formas polimórficas da 5-HAA, sendo que quatro desses polimorfos foram caracterizados por espectroscopia de Raman. Foram sintetizados três novos complexos de coordenação com o composto 1-MH. Os diferentes tipos de ligação do ião metálico com o ligando 1-MH foram investigados e identificados por espectroscopia de Raman, tendo-se verificado que as ligações de coordenação nos complexos estudados estão de acordo com o conceito HSAB

Self-Similar Patterns from Abiotic Decarboxylation Metabolism through Chemically Oscillating Reactions: A Prebiotic Model for the Origin of Life

The origin of life must have included an abiotic stage of carbon redox reactions that involved electron transport chains and the production of lifelike patterns. Chemically oscillating reactions (COR) are abiotic, spontaneous, out-of-equilibrium, and redox reactions that involve the decarboxylation of carboxylic acids with strong oxidants and strong acids to produce CO2 and characteristic self-similar patterns. Those patterns have circular concentricity, radial geometries, characteristic circular twins, colour gradients, cavity structures, and branching to parallel alignment. We propose that COR played a role during the prebiotic cycling of carboxylic acids, furthering the new model for geology where COR can also explain the patterns of diagenetic spheroids in sediments. The patterns of COR in Petri dishes are first considered and compared to those observed in some eukaryotic lifeforms. The molecular structures and functions of reactants in COR are then compared to key biological metabolic processes. We conclude that the newly recognised similarities in compositions and patterns warrant future research to better investigate the role of halogens in biochemistry; COR in life-forms, including in humans; and the COR-stage of prebiotic carbon cycling on other planets, such as Mars

The correlation between experimental polarized Raman spectra and their density functional theory prediction in the LCAO framework: The R

In this study, the polarized Raman spectra of the R3c LiNbO3 crystal are used as a benchmark test for density functional theory (DFT) full periodic boundary conditions linear combination of atomic orbitals (LCAO) calculation of the Raman tensors, according to the implementation in the CRYSTAL software. The theoretical approach used proved to provide excellent results regarding wavenumbers and relative intensities predictions for the transverse optical modes of both A1 and E symmetry, considerably improving over previously reported data based on the plane waves approach. Overall, the present investigation demonstrates that the LCAO approach, as implemented in the CRYSTAL software, gives excellent results regarding the calculation of Raman tensors and polarized Raman spectra. The possibility to put in correspondence the individual Raman tensors components and bands intensities in the different back-scattering experimental configurations revealed that the computed Raman tensors are very accurate, not only considering their average values (tensors invariant in the combination suitable for the description of Raman scattering of isotropic materials) but also when the tensors individual components are considered. Based on the present results, a reassignment of the E (TO) modes of the R3c LiNbO3 crystal is proposed, in particular for the 2 E and 9 E modes, which have been a matter of discussion in the recent years