| 1. |
- Heimdal Nilsson, Elna, et al.
(författare)
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Tropospheric Photolysis Rates of the Acetaldehyde Isotopologues CD3CHO and CD3CDO Relative to CH3CHO Measured at the European Photoreactor Facility.
- 2015
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 119:11, s. 2562-2567
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Tidskriftsartikel (refereegranskat)abstract
- Acetaldehyde is a hazardous pollutant found in indoor and ambient air. Acetaldehyde photolysis is pressure- and wavelength-dependent with three distinct product channels. In this study, the photolysis rates of CH3CHO, CD3CDO, and CD3CHO are studied in natural tropospheric conditions using long path FTIR spectroscopy, at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. The average relative photolysis rate as an average of four experiments for the fully deuterated isotopologue is jCH3CHO/jCD3CDO = 1.75 ± 0.04, and as a result of a single experiment jCH3CHO/jCD3CHO = 1.10 ± 0.10. These results, combined with our previous determination of jCH3CHO/jCH3CDO = 1.26 ± 0.03, provide mechanistic insight into the photodissociation dynamics of the photoexcited species. Despite the extensive isotopic scrambling in photoexcited acetaldehyde that has recently been reported, the position of the substitution has a clear effect on the relative photolysis rates.
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| 2. |
- Andersen, J, et al.
(författare)
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Spectroscopic identification of ethanol-water conformers by large-amplitude hydrogen bond librational modes.
- 2015
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 143:22
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with ethanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic H/D-substitution of the ethanol subunit enabled by a dual inlet deposition procedure enables the observation and unambiguous assignment of the intermolecular high-frequency out-of-plane and the low-frequency in-plane donor OH librational modes for two different conformations of the mixed binary ethanol/water complex. The resolved donor OH librational bands confirm directly previous experimental evidence that ethanol acts as the O⋯HO hydrogen bond acceptor in the two most stable conformations. In the most stable conformation, the water subunit forces the ethanol molecule into its less stable gauche configuration upon dimerization owing to a cooperative secondary weak O⋯HC hydrogen bond interaction evidenced by a significantly blue-shift of the low-frequency in-plane donor OH librational band origin. The strong correlation between the low-frequency in-plane donor OH librational motion and the secondary intermolecular O⋯HC hydrogen bond is demonstrated by electronic structure calculations. The experimental findings are further supported by CCSD(T)-F12/aug-cc-pVQZ calculations of the conformational energy differences together with second-order vibrational perturbation theory calculations of the large-amplitude donor OH librational band origins.
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| 3. |
- Andersen, J., et al.
(författare)
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The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol-water complexes
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:37, s. 23761-23769
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol-water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol is a superior hydrogen bond acceptor. The class of large-amplitude donor OH librational motion is shown to account for up to 5.1 kJ mol(-1) of the destabilizing change of vibrational zero-point energy upon intermolecular OH center dot center dot center dot O hydrogen bond formation. The experimental findings are supported by complementary electronic structure calculations at the CCSD(T)-F12/aug-cc-pVTZ level of theory.
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| 4. |
- Lindgren, Johan, et al.
(författare)
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Interpreting melanin-based coloration through deep time : A critical Review
- 2015
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society of London. - 0962-8452 .- 1471-2954. ; 282:1813
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Forskningsöversikt (refereegranskat)abstract
- Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their ‘mouldic impressions’) as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues.We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.
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| 5. |
- Lindgren, Johan, et al.
(författare)
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Molecular composition and ultrastructure of Jurassic paravian feathers
- 2015
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers.
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