Unravelling the Keto-Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone

Avobenzone (AB) is a widely used UVA filter known to undergo irreversible photodegradation. Here, we investigate the detailed pathways by which AB photodegrades by applying UV laser-interfaced mass spectrometry to protonated AB ions. Gas-phase infrared multiple-photon dissociation (IRMPD) spectra obtained with the free electron laser for infrared experiments, FELIX, (600-1800 cm-1) are also presented to confirm the geometric structures. The UV gas-phase absorption spectrum (2.5-5 eV) of protonated AB contains bands that correspond to selective excitation of either the enol or diketo forms, allowing us to probe the resulting, tautomer-dependent photochemistry. Numerous photofragments (i.e. photodegradants) are directly identified for the first time, with m/z 135 and 161 dominating, and m/z 146 and 177 also appearing prominently. Analysis of the production spectra of these photofragments reveals that that strong enol to keto photoisomerism is occurring, and that protonation significantly disrupts the stability of the enol (UVA active) tautomer. Close comparison of fragment ion yields with the TDDFT-calculated absorption spectra give detailed information on the location and identity of the dissociative excited state surfaces, and thus provide new insight into the photodegradation pathways of avobenzone, and photoisomerisation of the wider class of β-diketone containing molecules.<br>

Download Full-text

Crystallographic evidence of Watson–Crick connectivity in the base pair of anionic adenine with thymine

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2008379117 ◽

2020 ◽

Vol 117 (31) ◽

pp. 18224-18230

Author(s):

Manish Kumar Mishra ◽

Steven P. Kelley ◽

Volodymyr Smetana ◽

David A. Dixon ◽

Ashley S. McNeill ◽

...

Keyword(s):

Gas Phase ◽

Base Pair ◽

Phase Reaction ◽

Base Pairs ◽

Gas Phase Reaction ◽

Neutral Base ◽

The Stability ◽

Structure Calculations ◽

Insight Into ◽

Stable Formation

Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N4444]+) or tetrabutylphosphonium ([P4444]+) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N4444][Ad]·2H2O, and thymine, [P4444][Thy]·2H2O, as well as the double salt cocrystal, [P4444]2[Ad][Thy]·3H2O·2HThy. The cocrystal includes the anionic [Ad−(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson–Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.

Download Full-text

The Stability and Decomposition of Gaseous [Mn(CO)5]2(μ-SiH2)

Zeitschrift für Naturforschung A ◽

10.1515/zna-1988-8-908 ◽

1988 ◽

Vol 43 (8-9) ◽

pp. 758-764 ◽

Cited By ~ 3

Author(s):

G.T. Stauf ◽

D. La Graffe ◽

P. A. Dowben ◽

K. Emrich ◽

S. Barfuss ◽

...

Keyword(s):

Gas Phase ◽

Mass Spectroscopy ◽

Potential Application ◽

Organometallic Compound ◽

Thermodynamic Cycle ◽

Decomposition Process ◽

Ionization Mass ◽

Uv Laser ◽

Ionization Mass Spectroscopy ◽

The Stability

Abstract The ionic decomposition of gaseous bridge-bonded dimanganese silyl carbonyl [Mn(CO)5]2(μ-SiH2) has been investigated via photon and electron induced ionization mass spectroscopy, as well as gas-phase photoabsorption measurements. The thermodynamic cycle incorporating ionic fragments has been constructed from these results. The thermodynamic cycle illuminates the decomposition process of this organometallic compound. This has potential application in the production of silicide Mn2Si coatings by both pyrolysis and by patterned photolysis using an UV laser.

Download Full-text

Gas-phase vibrational spectroscopy of triphenylamine: the effect of charge on structure and spectra

Physical Chemistry Chemical Physics ◽

10.1039/c7cp02638b ◽

2017 ◽

Vol 19 (30) ◽

pp. 19881-19889 ◽

Cited By ~ 14

Author(s):

Musleh Uddin Munshi ◽

Giel Berden ◽

Jonathan Martens ◽

Jos Oomens

Keyword(s):

Gas Phase ◽

Vibrational Spectroscopy ◽

Ir Spectrum ◽

Free Electron ◽

Free Electron Laser ◽

Irmpd Spectroscopy ◽

Infrared Multiple Photon Dissociation

The effect of ionization by oxidation and protonation on the structure and IR spectrum of isolated, gas-phase triphenylamine (TPA) has been investigated by infrared multiple photon dissociation (IRMPD) spectroscopy in the fingerprint range from 600 cm−1 to 1800 cm−1 using an infrared free electron laser.

Download Full-text

Aleksey Peshkov as an editor of Samarskaya Gazeta

Voprosy literatury ◽

10.31425/0042-8795-2020-4-128-138 ◽

2020 ◽

pp. 128-138

Author(s):

A. S. Bik-Bulatov

Keyword(s):

Local History ◽

Organizational Skills ◽

First Time ◽

New Evidence ◽

Insight Into ◽

Shed Light

The article uses little known letters of M. Gorky, many of which were published for the first time in 1997, as well as findings of Samara-based experts in local history to shed light on the writer’s work as editor-in-chief of the Samarskaya Gazeta newspaper in 1895. The researcher introduces hitherto unstudied reminiscences of the journalist D. Linyov (Dalin) about this period, which reference a letter by Gorky, now lost. The paper details a newly discovered episode of Gorky’s professional biography as a journalist: it concerns his campaign against a Samara ‘she-wolf,’ the madam of a local brothel A. Neucheva. Linyov’s reminiscences turn out to be an important and interesting source, offering an insight into the daily grind of the young editor Gorky, providing new evidence of his excellent organizational skills, and describing his moral and social stance. The author presents his work in the context of a recently initiated broader discussion about the need to map out all Russian periodicals for the period until 1917, as well as all research devoted to individual publications.

Download Full-text

Comparative Study of Chemical Compositions and Antioxidant Capacities of Oils Obtained from 15 Macadamia (Macadamia integrifolia) Cultivars in China

Foods ◽

10.3390/foods10051031 ◽

2021 ◽

Vol 10 (5) ◽

pp. 1031

Author(s):

Xixiang Shuai ◽

Taotao Dai ◽

Mingshun Chen ◽

Ruihong Liang ◽

Liqing Du ◽

...

Keyword(s):

Palmitoleic Acid ◽

Linear Regression Analysis ◽

Monounsaturated Fatty Acids ◽

Multiple Linear Regression Analysis ◽

Chemical Compositions ◽

Macadamia Integrifolia ◽

Antioxidant Capacities ◽

Squalene Content ◽

First Time ◽

Insight Into

The planting area of macadamia in China accounted for more than one third of the world’s planted area. The lipid compositions, minor components, and antioxidant capacities of fifteen varieties of macadamia oil (MO) in China were comparatively investigated. All varieties of MO were rich in monounsaturated fatty acids, mainly including oleic acid (61.74–66.47%) and palmitoleic acid (13.22–17.63%). The main triacylglycerols of MO were first time reported, including 19.2–26.1% of triolein, 16.4–18.2% of 1-palmitoyl-2,3-dioleoyl-glycerol, and 11.9–13.7% of 1-palmitoleoyl-2-oleoyl-3-stearoyl-glycerol, etc. The polyphenol, α-tocotrienol and squalene content varied among the cultivars, while Fuji (791) contained the highest polyphenols and squalene content. Multiple linear regression analysis indicated the polyphenols and squalene content positively correlated with the antioxidant capacity. This study can provide a crucial directive for the breeding of macadamia and offer an insight into industrial application of MO in China.

Download Full-text

ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab139 ◽

2021 ◽

Vol 502 (3) ◽

pp. 3294-3311

Author(s):

Yuanming Wang ◽

Artem Tuntsov ◽

Tara Murphy ◽

Emil Lenc ◽

Mark Walker ◽

...

Keyword(s):

Physical Properties ◽

Angular Width ◽

Scattering Medium ◽

Central Frequency ◽

Linear Arrangement ◽

Plasma Filament ◽

Kinematic Models ◽

Tidal Stream ◽

First Time ◽

Insight Into

ABSTRACT We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-h observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-min model-subtracted images with sensitivity of $\sim\! 200\, \mu$Jy/beam; two of them are extreme intra-hour variables with modulation indices up to $\sim 40{{\ \rm per\ cent}}$ and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼1 arcmin and length ∼2 degrees, revealing the existence of a huge plasma filament in front of them. We derived kinematic models of this plasma from the annual modulation of the scintillation rate of our sources, and we estimated its likely physical properties: a distance of ∼4 pc and length of ∼0.1 pc. The characteristics we observe for the scattering screen are incompatible with published suggestions for the origin of intra-hour variability leading us to propose a new picture in which the underlying phenomenon is a cold tidal stream. This is the first time that multiple scintillators have been detected behind the same plasma screen, giving direct insight into the geometry of the scattering medium responsible for enhanced scintillation.

Download Full-text

Rapid systemic surge of IL-33 after severe human trauma: a prospective observational study

Molecular Medicine ◽

10.1186/s10020-021-00288-1 ◽

2021 ◽

Vol 27 (1) ◽

Author(s):

Olav Sundnes ◽

William Ottestad ◽

Camilla Schjalm ◽

Peter Lundbäck ◽

Lars la Cour Poulsen ◽

...

Keyword(s):

High Resolution ◽

Prospective Observational Study ◽

Tissue Injury ◽

Trauma Patients ◽

Decoy Receptor ◽

Interleukin 33 ◽

Injured Patients ◽

First Time ◽

Kinetics Of ◽

Insight Into

Abstract Background Alarmins are considered proximal mediators of the immune response after tissue injury. Understanding their biology could pave the way for development of new therapeutic targets and biomarkers in human disease, including multiple trauma. In this study we explored high-resolution concentration kinetics of the alarmin interleukin-33 (IL-33) early after human trauma. Methods Plasma samples were serially collected from 136 trauma patients immediately after hospital admission, 2, 4, 6, and 8 h thereafter, and every morning in the ICU. Levels of IL-33 and its decoy receptor sST2 were measured by immunoassays. Results We observed a rapid and transient surge of IL-33 in a subset of critically injured patients. These patients had more widespread tissue injuries and a greater degree of early coagulopathy. IL-33 half-life (t1/2) was 1.4 h (95% CI 1.2–1.6). sST2 displayed a distinctly different pattern with low initial levels but massive increase at later time points. Conclusions We describe for the first time early high-resolution IL-33 concentration kinetics in individual patients after trauma and correlate systemic IL-33 release to clinical data. These findings provide insight into a potentially important axis of danger signaling in humans.

Download Full-text

Insight into the Secondary Metabolites of Geum urbanum L. and Geum rivale L. Seeds (Rosaceae)

Plants ◽

10.3390/plants10061219 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1219

Author(s):

Marek Bunse ◽

Peter Lorenz ◽

Florian C. Stintzing ◽

Dietmar R. Kammerer

Keyword(s):

Fatty Acids ◽

Phenolic Compounds ◽

Unsaturated Fatty Acids ◽

Asiatic Acid ◽

Cosmetic Products ◽

Nutritional Properties ◽

First Time ◽

Derivatives Of ◽

Geum Urbanum ◽

Insight Into

The present study aimed at the identification and quantitation of phenolic compounds, fatty acids, and further characteristic substances in the seeds of Geum urbanum L. and Geum rivale L. For this purpose, individual components of extracts recovered with MeOH, CH2Cl2, and by cold-pressing, respectively, were characterized by HPLC-DAD/ESI-MSn and GC/MS and compared with reference compounds. For both Geum species, phenolic compounds, such as flavonoids and gallic acid derivatives, and triterpenes, such as saponins and their aglycones, were detected. Surprisingly, both Geum species revealed the presence of derivatives of the triterpenoid aglycons asiatic acid and madecassic acid, which were characterized for the first time in the genus Geum. Furthermore, the fatty acids of both species were characterized by GC–MS after derivatization. Both species showed a promising fatty-acid profile in terms of nutritional properties because of high proportions of unsaturated fatty acids. Linoleic acid and linolenic acid were most abundant, among other compounds such as palmitic acid and stearic acid. In summary, the present study demonstrates the seeds of G. urbanum and G. rivale to be a valuable source of unsaturated fatty acids and bioactive phenolics, which might be exploited for nutritional and cosmetic products and for phytotherapeutic purposes.

Download Full-text

An insight into the gas-phase inhibition mechanism of polymers by addition of triphenyl phosphate flame retardant

10.1063/5.0033887 ◽

2020 ◽

Author(s):

S. A. Trubachev ◽

O. P. Korobeinichev ◽

S. A. Kostritsa ◽

V. D. Kobtsev ◽

A. A. Paletsky ◽

...

Keyword(s):

Flame Retardant ◽

Gas Phase ◽

Inhibition Mechanism ◽

Triphenyl Phosphate ◽

Insight Into

Download Full-text