Comments in a Discussion: Differential Rates of d- and l-tyrosine Crystallization

Shinitzky, Meir; Deamer, David W.

doi:10.1007/s11084-008-9129-2

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…For instance, it was recently seen that d - and l -tyrosine had different solubilities in water . The authors of this study reached for an extraordinary explanation, parity violating energy differences; however, Ockham would search elsewhere, and other philosophers reasonably ascribed the observations on tyrosine to undetected chiral impurities that can surely affect crystal growth and dissolution in small quantities . Similar effects may well account for the differences seen herein.…”

Section: Discussionmentioning

confidence: 56%

Triplet States of the Nonlinear Optical Chromophore DCM in Single Crystals of Potassium Hydrogen Phthalate and Their Relationship to Single-Molecule Dark States

et al. 2009

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Single-molecule dark states are often attributed to photoexcited triplets with scant evidence of the participation of paramagnetic molecules. The photodynamics of blinking single molecules of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) in crystals of potassium hydrogen phthalate (KAP) were compared with the lifetimes of DCM triplet states, likewise in KAP, whose zero-field splitting (ZFS) tensors were fully characterized by time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy. Luminescent mixed crystals of KAP were grown from solutions containing 10(-4) -10(-9) M DCM, a model optically nonlinear chromophore. The luminescent dye was localized in the {111} crystalline growth sectors. The photoexcited triplets states of DCM in the heavily dyed (10(-4) M) crystals were analyzed by TR-EPR spectroscopy. The photoexcited singlet states of DCM in lightly dyed crystals (10(-9) M) were analyzed by single-molecule microscopy. Large blue shifts in the absorption and emission spectra of DCM in KAP were interpreted as a consequence of protonation at the dimethylamino nitrogen atom, an assignment supported by calculations of the zero-field splitting (ZFS) tensors of molecules in their triplet states. Experimental ZFS tensors with eigenvalues comparable to those of the computed tensors were determined from the angular dependence of the EPR spectra of DCMH(+) triplets within KAP single crystals with respect to the applied magnetic field. Data from individual growth sectors failed to show magnetically equivalent site occupancies, evidence of the kinetic ordering during growth. The intermittent fluorescence of individual chromophores was analyzed. The distributions of on(off) times were characterized by distributed rates fit to power laws. The lifetime of the triplet states was analyzed from the time decay of the EPR signals between 100 and 165 K. The data were well fit with a single time constant for the signal decay, a result wholly inconsistent with the blinking of single molecules with off times commonly of tens of seconds. Triplet decay was extrapolated to approximately 25 micros at room temperature. Therefore, the assumption that single-molecule dark states originate with triplet excited states is not sustainable for single DCM molecules in KAP.

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Section: Discussionmentioning

confidence: 56%

Triplet States of the Nonlinear Optical Chromophore DCM in Single Crystals of Potassium Hydrogen Phthalate and Their Relationship to Single-Molecule Dark States

et al. 2009

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“…Both [221] and [222] concluded that the discrepancy of D/L-tyrosine solubility was due to different contaminants, such as fungal spores being present in the D/L-tyrosine powders purchased from various vendors. The authors of [223] contested this interpretation, arguing that the solubility differences were due to the parity violation energy difference between enantiomers (a topic which falls outside of the scope of this review).…”

Section: Mineral-organic Interactions For Driving Enantiomeric Excessmentioning

confidence: 99%

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

et al. 2022

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Chirality is a central feature in the evolution of biological systems, but the reason for biology’s strong preference for specific chiralities of amino acids, sugars, and other molecules remains a controversial and unanswered question in origins of life research. Biological polymers tend toward homochiral systems, which favor the incorporation of a single enantiomer (molecules with a specific chiral configuration) over the other. There have been numerous investigations into the processes that preferentially enrich one enantiomer to understand the evolution of an early, racemic, prebiotic organic world. Chirality can also be a property of minerals; their interaction with chiral organics is important for assessing how post-depositional alteration processes could affect the stereochemical configuration of simple and complex organic molecules. In this paper, we review the properties of organic compounds and minerals as well as the physical, chemical, and geological processes that affect organic and mineral chirality during the preservation and detection of organic compounds. We provide perspectives and discussions on the reactions and analytical techniques that can be performed in the laboratory, and comment on the state of knowledge of flight-capable technologies in current and future planetary missions, with a focus on organics analysis and life detection.

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“…Intriguingly, recent work has shown that the two might be related in that L-amino acids can also catalyse the formation of D-glyceraldehyde, and hence D-sugars, in plausible planetary environments. 6 Proposed mechanisms for the origin of biochiral specificity include the templating of organic precursors on the surfaces of non-centrosymmetric minerals such as quartz and calcite; [7][8][9] chance selection of one isomer followed by sequential replication by the resulting living process; 10 asymmetry at the central Cu ion of the complex involved in the salt-induced peptide formation reaction; 11 differential crystallization rates of D-and L-isomers, [12][13][14][15] seeding from space with non-racemic precursors [16][17][18] synthesised under conditions involving circularly polarised ultra-violet light 19,20 and even mechanisms involving possible quantum mechanical condensation phenomena at low temperature and the weak nuclear force. 21,22 There is, however, no consensus as to how such near-perfect enantiomeric separation occurred in biology and in the absence of a net chiral symmetry operator, no simple fractionation mechanism can lead to overall chiral selectivity.…”

Section: Introductionmentioning

confidence: 99%

Selective adsorption and chiral amplification of amino acids in vermiculite clay-implications for the origin of biochirality

Fraser

Fitz

Jakschitz

et al. 2011

Phys. Chem. Chem. Phys.

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Smectite clays are hydrated layer silicates that, like micas, occur naturally in abundance. Importantly, they have readily modifiable interlayer spaces that provide excellent sites for nanochemistry. Vermiculite is one such smectite clay and in the presence of small chain-length alkyl-NH 3 Cl ions, forms sensitive, 1-D ordered model clay systems with expandable nano-pore inter-layer regions. These inter-layers readily adsorb organic molecules. N-propyl NH 3 Cl vermiculite clay gels were used to determine the adsorption of alanine, lysine and histidine by chiral HPLC. The results show that during reaction with fresh vermiculite interlayers, significant chiral enrichment of either L-and D-enantiomers occurs depending on the amino acid. Chiral enrichment of the supernatant solutions is up to about 1% per pass. In contrast, addition to clay interlayers already reacted with amino acid solutions resulted in little or no change in D/L ratio during the time of the experiment. Adsorption of small amounts of amphiphilic organic molecules in clay inter-layers is known to produce Layer-by-Layer or Langmuir-Blodgett films. Moreover atomistic simulations show that self-organization of organic species in clay interlayers is important. These noncentrosymmetric, chirally active nanofilms may cause clays to act subsequently as chiral amplifiers, concentrating organic material from dilute solution and having different adsorption energetics for D-and L-enantiomers. The additional role of clays in RNA oligomerization already postulated by Ferris and others, together with the need for the organization of amphiphilic molecules and lipids noted by Szostak and others, suggests that such chiral separation by clays in lagoonal environments at normal biological temperatures might also have played a significant role in the origin of biochirality.2

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Comments in a Discussion: Differential Rates of d- and l-tyrosine Crystallization

Cited by 6 publications

References 13 publications

Triplet States of the Nonlinear Optical Chromophore DCM in Single Crystals of Potassium Hydrogen Phthalate and Their Relationship to Single-Molecule Dark States

Triplet States of the Nonlinear Optical Chromophore DCM in Single Crystals of Potassium Hydrogen Phthalate and Their Relationship to Single-Molecule Dark States

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

Selective adsorption and chiral amplification of amino acids in vermiculite clay-implications for the origin of biochirality

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