scholarly journals Unravelling the origins of ice nucleation on organic crystals

2018 ◽  
Vol 9 (42) ◽  
pp. 8077-8088 ◽  
Author(s):  
Gabriele C. Sosso ◽  
Thomas F. Whale ◽  
Mark A. Holden ◽  
Philipp Pedevilla ◽  
Benjamin J. Murray ◽  
...  
Keyword(s):  
Phase Transition ◽  
Amino Acids ◽  
Organic Molecules ◽  
Ice Nucleation ◽  
Organic Crystals

Organic molecules such as steroids or amino acids form crystals that can facilitate the formation of ice – arguably the most important phase transition on earth.

scholarly journals Peculiarities of promiscuous l-threonine transaldolases for enantioselective synthesis of β-hydroxy-α-amino acids

2021 ◽  
Author(s):  
Shan Wang ◽  
Hai Deng
Keyword(s):  
Amino Acids ◽  
Organic Molecules ◽  
Stereoselective Synthesis ◽  
Enantioselective Synthesis ◽  
General Mechanism ◽  
Future Developments ◽  
Key Points ◽  
Biomaterial Science ◽  
One Step ◽  
Harsh Conditions

Abstract The introduction of β-hydroxy-α-amino acids (βHAAs) into organic molecules has received considerable attention as these molecules have often found widespread applications in bioorganic chemistry, medicinal chemistry and biomaterial science. Despite innovation of asymmetric synthesis of βHAAs, stereoselective synthesis to control the two chiral centres at Cα and Cβ positions is still challenging, with poor atomic economy and multi protection and deprotection steps. These syntheses are often operated under harsh conditions. Therefore, a biotransformation approach using biocatalysts is needed to selectively introduce these two chiral centres into structurally diverse molecules. Yet, there are few ways that enable one-step synthesis of βHAAs. One is to extend the substrate scope of the existing enzyme inventory. Threonine aldolases have been explored to produce βHAAs. However, the enzymes have poor controlled installation at Cβ position, often resulting in a mixture of diastereoisomers which are difficult to be separated. In this respect, l-threonine transaldolases (LTTAs) offer an excellent potential as the enzymes often provide controlled stereochemistry at Cα and Cβ positions. Another is to mine LTTA homologues and engineer the enzymes using directed evolution with the aim of finding engineered biocatalysts to accept broad substrates with enhanced conversion and stereoselectivity. Here, we review the development of LTTAs that incorporate various aldehyde acceptors to generate structurally diverse βHAAs and highlight areas for future developments. Key points • The general mechanism of the transaldolation reaction catalysed by LTTAs • Recent advances in LTTAs from different biosynthetic pathways • Applications of LTTAs as biocatalysts for production of βHAAs

scholarly journals Chiroptical activity of hydroxycarboxylic acids with implications for the origin of biological homochirality

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jana Bocková ◽  
Nykola C. Jones ◽  
Uwe J. Meierhenrich ◽  
Søren V. Hoffmann ◽  
Cornelia Meinert
Keyword(s):  
Amino Acids ◽  
Lactic Acid ◽  
Organic Molecules ◽  
Building Blocks ◽  
Aliphatic Chain ◽  
Monocarboxylic Acids ◽  
Hydroxycarboxylic Acids ◽  
Polarised Light ◽  
Suitable Target ◽  
Anisotropy Spectra

AbstractCircularly polarised light (CPL) interacting with interstellar organic molecules might have imparted chiral bias and hence preluded prebiotic evolution of biomolecular homochirality. The l-enrichment of extra-terrestrial amino acids in meteorites, as opposed to no detectable excess in monocarboxylic acids and amines, has previously been attributed to their intrinsic interaction with stellar CPL revealed by substantial differences in their chiroptical signals. Recent analyses of meteoritic hydroxycarboxylic acids (HCAs) – potential co-building blocks of ancestral proto-peptides – indicated a chiral bias toward the l-enantiomer of lactic acid. Here we report on novel anisotropy spectra of several HCAs using a synchrotron radiation electronic circular dichroism spectrophotometer to support the re-evaluation of chiral biomarkers of extra-terrestrial origin in the context of absolute photochirogenesis. We found that irradiation by CPL which would yield l-excess in amino acids would also yield l-excess in aliphatic chain HCAs, including lactic acid and mandelic acid, in the examined conditions. Only tartaric acid would show “unnatural” d-enrichment, which makes it a suitable target compound for further assessing the relevance of the CPL scenario.

scholarly journals Adsorption on graphene: flat to edge to end transitions of phenyl hydroquinone

2017 ◽  
Vol 19 (27) ◽  
pp. 17521-17525 ◽  
Author(s):  
Lifu Chen ◽  
Eden E. L. Tanner ◽  
Richard G. Compton
Keyword(s):  
Phase Transition ◽  
Organic Molecules ◽  
Graphene Surface

A concentration driven three-stage phase transition of large organic molecules on the graphene surface is revealed.

scholarly journals Simple and efficient modifications of well known techniques for reliable growth of high-quality crystals of small bioorganic molecules

2014 ◽  
Vol 47 (4) ◽  
pp. 1435-1442 ◽  
Author(s):  
Denis A. Rychkov ◽  
Sergey G. Arkhipov ◽  
Elena V. Boldyreva
Keyword(s):  
Amino Acids ◽  
Secondary School ◽  
Organic Molecules ◽  
Poor Quality ◽  
Chemical Degradation ◽  
School Level ◽  
Chemistry Curriculum ◽  
High Quality ◽  
Small Organic Molecules ◽  
Secondary School Level

A number of modifications to traditional techniques are suggested in order to overcome problems that frequently arise when growing crystals from solution. These improvements, and their combination, help to avoid problems such as poor nucleation, the spontaneous precipitation of many poor-quality small powder-like crystals, crystals adhering to the crystallization vessel or to each other, and chemical degradation of the solution. The proposed techniques can be used to crystallize desirable metastable polymorphs reliably. None of the suggested methods demands the usage of any special or expensive equipment, or specific skills, and they can be implemented in the chemistry curriculum even at secondary school level. Examples are given for the crystallization of small organic molecules such as carboxylic acids, amino acids, pharmaceuticals etc., but the same techniques are applicable to other classes of compound.

Absorption of L-alanine and other dissolved nutrients by the spines of Paracentrotus lividus (Echinoidea)

1977 ◽  
Vol 57 (4) ◽  
pp. 1031-1045 ◽  
Author(s):  
M. E. de Burgh ◽  
A. B. West ◽  
F. Jeal
Keyword(s):  
Amino Acids ◽  
Organic Molecules ◽  
Marine Invertebrates ◽  
Analytical Techniques ◽  
Paracentrotus Lividus ◽  
Direct Absorption ◽  
Dissolved Nutrients ◽  
Recent Developments ◽  
Modern Analytical

The possibility that marine invertebrates might obtain part of their nutritional requirements by direct absorption of dissolved molecules through the epidermis has recently received considerable attention. This revival of interest in a field which had been virtually abandoned since the early part of the century was led by the findings of Stephens & Schinske (1957, 1958, 1961). Modern analytical techniques have revealed that the amount of dissolved nutrients in coastal waters is much greater than was formerly realized; total amino acids have been recorded in concentrations of up to 10-4 mole/litre in south-east Alaskan waters (Schell, 1974) and 7 x 10-5 mole/litre off Helgoland (Bohling, 1970). Direct absorption of amino acids has been conclusively established in several phyla (see reviews by Stephens, 1968,1972), and one of the major aims of current research is to show that dissolved organic molecules taken up from available concentrations could be of nutritional significance. Recent developments concerning the possible roles of uptake in marine ecosystems have been reviewed by West, de Burgh & Jeal (1977).

scholarly journals Enantioselective organocatalysis in the synthesis of biologically relevant compounds

2016 ◽  
Author(s):  
Lukasz Albrecht
Keyword(s):  
Organic Chemistry ◽  
Amino Acids ◽  
Organic Molecules ◽  
Asymmetric Induction ◽  
Chiral Catalyst ◽  
Biologically Relevant ◽  
Enantioselective Reactions ◽  
Asymmetric Organocatalysis ◽  
Biologically Relevant Molecules ◽  
Operational Simplicity

The development of methods for the preparation of biologically relevant compounds in an enantiomerically enriched form constitutes one of the most significant tasks in the contemporary organic chemistry. In particular, enantioselective reactions where prochiral substrates are converted into enantiomerically enriched products in the presence of chiral catalyst are of great importance. Recently, asymmetric organocatalysis, where simple organic molecules are used as catalysts of various enantiodifferentiating reactions, has become a highly useful synthetic tool enabling for the efficient asymmetric induction based on diverse activation modes. Herein, we report our studies on organocatalytic, enantioselective strategies for the synthesis of biologically relevant molecules such as: quaternary α-amino acids and their isoelectronic analogs α-aminophosphonates, benzo[1,5]oxazocines, α-methylidene-δ-lactones, α-alkylidene-ketones, furfural derivatives, and benzothiophenes. The devised approaches utilize readily available chiral organocatalysts to control stereo-chemical reaction outcomes. Operational simplicity, efficiency and high enantio- and diastereoselectivities are the main benefits of the developed strategies.

scholarly journals The Impact of (bio-)organic substances on the ice nucleation activity of the K-feldspar microcline in aqueous solutions

2021 ◽  
Author(s):  
Kristian Klumpp ◽  
Claudia Marcolli ◽  
Thomas Peter
Keyword(s):  
Amino Acids ◽  
Citric Acid ◽  
Carboxylic Acids ◽  
Water Activity ◽  
Active Sites ◽  
Ice Nucleation ◽  
Organic Substances ◽  
Nucleation Activity ◽  
Ice Nucleation Activity ◽  
The Impact

Abstract. Potassium-feldspars (K-feldspars), such as microcline, are considered key dust minerals inciting ice nucleation in mixed phase clouds. Besides the high ice nucleation activity of microcline, recent studies also revealed a high sensi-tivity of microcline towards interaction with solutes on its surface. Here, we investigate the effect of organic and bio-organic substances on the ice nucleation activity of microcline, with the aim to better understand the underlying sur-face interactions. We performed immersion freezing experiments with microcline in solutions of three carboxylic acids, five amino acids and two polyols to represent these compound classes. By means of a differential scanning calorimeter we investigated the freezing of emulsified droplets of microcline suspended in various solutions. Depend-ing on the type of solute, different effects were observed. In the case of carboxylic acids (acetic, oxalic and citric acid), the measured heterogeneous onset temperatures, Thet, showed no significant deviation from the behavior pre-dicted by the water activity criterion, Thet(aw) = Tmelt(aw+Δaw), which relates Thet with the melting point temperature Tmelt via a constant water activity offset Δaw. While this behavior could be interpreted as a lack of interaction of the solute molecules with the surface, the carboxylic acids caused the fraction of heterogeneously frozen water, Fhet(aw), to decrease by up to 40 % with increasing solute concentrations. In combination, unaltered Thet(aw) and reduced Fhet(aw) suggest that active sites were largely deactivated by the acid molecules, but amongst those remaining active are also the best sites with the highest Thet. A deviation from this behavior is citric acid, which showed not only a de-crease in Fhet, but also a decrease in Thet of up to 4 K for water activities below 0.99, pointing to a depletion of the best active sites by interactions with the citrate ions. When neutralized solutions of the acids were used instead, the de-crease in Fhet became even more pronounced. The slope of Thet(aw) was different for each of the neutralized acid solu-tions. In the case of amino acid solutions, we found a decrease in Thet (up to 10 K), significantly below the Δaw-criterion, as well as a reduction in Fhet (up to 60 %). Finally, in case of the investigated polyols, no significant devia-tion of Thet from the Δaw-criterion was observed, and no significant deviation of Fhet in comparison to a pure water suspension was found. Furthermore, we measured the effects of aging on the ice nucleation activity in experiments with microcline suspended in solutions for up to seven days, and tested the reversibility of the interaction with the solutes after aging for 10 days. For citric acid, an ongoing irreversible degradation of the ice nucleation activity was observed, whereas the amino acids showed completely reversible effects. In summary, our experiments demonstrate a remarkable sensitivity of microcline ice nucleation activity to surface interactions with various solutes, underscoring the importance of the history of such particles from source to frozen cloud droplet in the atmosphere.

Search for molecular biosignatures on Mars: laboratory simulations of UV irradiation of molecule-mineral complexes

2021 ◽  
Author(s):  
Teresa Fornaro ◽  
Giovanni Poggiali ◽  
Maria Angela Corazzi ◽  
Cristina Garcia ◽  
Giulia Dimitri ◽  
...  
Keyword(s):  
Amino Acids ◽  
Organic Compounds ◽  
Uv Irradiation ◽  
Organic Molecules ◽  
Spectroscopic Characterization ◽  
Sample Return ◽  
Laboratory Simulations ◽  
Prebiotic Molecules

<div> </div> <p><strong>Abstract</strong></p> <p>We present laboratory activities of preparation, characterization, and UV irradiation processing of Mars soil analogues, which are key to support both in situ exploration and sample return missions devoted to detection of molecular biosignatures on Mars.</p> <p>In detail we prepared analog mineral samples relevant to the landing sites of past, present and future Mars exploration missions, such as Gale Crater, Jezero Crater, and Oxia Planum. We doped these samples with a large variety of organic molecules (both biotic and prebiotic molecules) like amino acids, nucleotides, monosaccharides, aldehydes, lipids. We investigated molecular photostability under UV irradiation by monitoring in situ possible modifications of infrared spectroscopic features. These investigations provide pivotal information for ground analysis carried out by rovers on Mars.</p> <p><strong>Introduction</strong></p> <p>Laboratory simulations of Mars are key to support the scientific activity and technology development of life detection instruments on board present and upcoming rover missions such as Mars2020 Perseverance [1] and ExoMars2022 Rosalind Franklin [2]. Studies about the stability of organic molecules in a Martian-like environment allow us to explore the conditions for the preservation of molecular biosignatures and develop models for their degradation in the Martian geological record. A systematic study of the effects of UV radiation on a variety of molecule-mineral complexes mimicking Martian soil can be key for the selection of the most interesting samples to analyse in situ or/and collect for sample return. Testing the sensitivity of different techniques for detection of the diagnostic features of molecular biosignatures embedded into mineral matrices as a function of the molecular concentration helps the choice, design and operation of flight instruments, as well as the interpretation of data collected on the ground during mission operative periods.</p> <p><strong>Methods</strong></p> <p>Experimental analyses were conducted in the Astrobiology Laboratory at INAF-Astrophysical Observatory of Arcetri (Firenze, Italy). Laboratory activities pertain to: (i) synthesis of Mars soil analogues doped with organic compounds that are considered potential molecular biosignatures; (ii) UV-irradiation processing of the Mars soil analogues under Martian-like conditions; and (iii) spectroscopic characterization of the Mars soil analogues.</p> <p><strong>Results</strong></p> <p>Such studies have shown to be very informative in identifying mineral deposits most suitable for preservation of organic compounds, while highlighting the complementarity of different techniques for biomarkers detection, which is critical for ensuring the success of space missions devoted to the search for signs of life on Mars.</p> <p>We will present a series of laboratory results on molecular degradation caused by UV on Mars and possible application to detection of organics by Martian rovers [3,4,5,6]. In detail, we investigated the photostability of several amino acids like glycine, alanine, methionine, valine, tryptophan, phenylalanine, glutamic acid, prebiotic molecules like urea, deoxyribose and glycolaldehyde, and biomarkers like nucleotides and phytane adsorbed on relevant Martian analogs. We monitored the degradation of these molecule-mineral complexes through in situ spectroscopic analysis, investigating the reflectance properties of the samples in the NIR/MIR spectral region. Such spectroscopic characterization of molecular alteration products provides support for two upcoming robotic missions to Mars that will employ NIR spectroscopy to look for molecular biosignatures, through the instruments SuperCam on board Mars 2020, ISEM, Ma_MISS and MicrOmega on board ExoMars 2022.</p> <p><strong>Acknowledgements</strong></p> <p>This research was supported by the Italian Space Agency (ASI) grant agreement ExoMars n. 2017-48-H.0.</p> <p><strong>References</strong></p> <p>[1] Farley K. A. et al. (2020) Space Sci. Rev. 216, 142.</p> <p>[2] Vago, J. L. et al. (2017) Astrobiology 6, 309–347.</p> <p>[3] Fornaro T. et al. (2013) Icarus 226, 1068–1085.</p> <p>[4] Fornaro T. et al. (2018) Icarus 313, 38-60.</p> <p>[5] Fornaro T. et al. (2020) Front. Astron. Space Sci. 7:539289.</p> <p>[6] Poggiali G. et al. (2020) Front. Astron. Space Sci. 7:18.</p>

Frameworks of Transition Metals and Linkers with Two or More Functional Groups

2000 ◽  
Vol 658 ◽  
Author(s):  
Slavi C. Sevov
Keyword(s):  
Amino Acids ◽  
Transition Metals ◽  
Functional Groups ◽  
Organic Molecules ◽  
Layered Structures ◽  
Amino Groups ◽  
Effect Of Ph ◽  
Open Framework ◽  
Acidic Conditions ◽  
New Compounds

ABSTRACTHybrid inorganic/organic materials with open-framework or layered structures are known for many transition metals linked by functionalized organic molecules such as organic diphosphonates, polycarboxylates, polynitriles, etc., species with more than one equivalent functional groups. We have studied the effect of pH on such a system of cobaltmethylenediphosphonate and report three new compounds, Na3Co[(O3PCH2PO3)(OH)],Na2Co(O3PCH2PO3)•H2O, and Co2[(O3PCH2PO3)(H2O)], that form at very basic, moderately basic, and acidic conditions, respectively. More interestingstructural chemistry should be expected from linkers with two or more different functionalities. Both the carboxylic and phosphonic groups in carboxyethylphosphonic acid are used to coordinate to cobalt or calcium atoms in the new compounds Co3(O3PCH2CH2COO)2•6H2O and Ca(O3PCH2CH2COOH)•H2O. Taking one more step further in complexity we have also studied linkers with three different functional groups, phosphonated amino acids. The structures of two new compounds, Zn(O3PCH2CH(NH3)COO) and Zn(O3PCH2CH2CH(NH3)COO), are threedimensional frameworks made of zinccoordinated by both the carboxylic and phosphonic ends of the organic molecules. The amino groups are protonated and terminal in the voids of the frameworks.

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