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Photodissociation of Sodium Iodide Clusters Doped with Small Hydrocarbons.

ABSTRACT: Marine aerosols consist of a variety of compounds and play an important role in many atmospheric processes. In the present study, sodium iodide clusters with their simple isotope pattern serve as model systems for laboratory studies to investigate the role of iodide in the photochemical processing of sea-salt aerosols. Salt clusters doped with camphor, formate and pyruvate are studied in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) coupled to a tunable laser system in both UV and IR range. The analysis is supported by ab initio calculations of absorption spectra and energetics of dissociative channels. We provide quantitative analysis of IRMPD measurements by reconstructing one-photon spectra and comparing them with the calculated ones. While neutral camphor is adsorbed on the cluster surface, the formate and pyruvate ions replace an iodide ion. The photodissociation spectra revealed several wavelength-specific fragmentation pathways, including the carbon dioxide radical anion formed by photolysis of pyruvate. Camphor and pyruvate doped clusters absorb in the spectral region above 290?nm, which is relevant for tropospheric photochemistry, leading to internal conversion followed by intramolecular vibrational redistribution, which leads to decomposition of the cluster. Potential photodissociation products of pyruvate in the actinic region may be formed with a cross section of <2×10^-20 ?cm² , determined by the experimental noise level.

SUBMITTER: Bersenkowitsch NK

PROVIDER: S-EPMC6120481 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Photodissociation of Sodium Iodide Clusters Doped with Small Hydrocarbons.

Bersenkowitsch Nina K NK Ončák Milan M Heller Jakob J van der Linde Christian C Beyer Martin K MK

Chemistry (Weinheim an der Bergstrasse, Germany) 20180727 47

Marine aerosols consist of a variety of compounds and play an important role in many atmospheric processes. In the present study, sodium iodide clusters with their simple isotope pattern serve as model systems for laboratory studies to investigate the role of iodide in the photochemical processing of sea-salt aerosols. Salt clusters doped with camphor, formate and pyruvate are studied in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) coupled to a tunable laser system i ...[more]

PMID: 29979470

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Project description:Background: The ability of thyroid follicular epithelial cells to accumulate iodide via the sodium/iodide symporter (NIS) is exploited to successfully treat most thyroid cancers, although a subset of patients lose functional NIS activity and become unresponsive to radioiodide therapy, with poor clinical outcome. Our knowledge of NIS regulation remains limited, however. While numerous membrane proteins are functionally regulated via dimerization, there is little definitive evidence of NIS dimerization, and whether this might impact upon radioiodide uptake and treatment success is entirely unknown. We hypothesized that NIS dimerizes and that dimerization is a prerequisite for iodide uptake. Methods: Coimmunoprecipitation, proximity ligation, and Förster resonance energy transfer (FRET) assays were used to assess NIS:NIS interaction. To identify residues involved in dimerization, a homology model of NIS structure was built based on the crystal structure of the dimeric bacterial protein vSGLT. Results: Abundant cellular NIS dimerization was confirmed in vitro via three discrete methodologies. FRET and proximity ligation assays demonstrated that while NIS can exist as a dimer at the plasma membrane (PM), it is also apparent in other cellular compartments. Homology modeling revealed one key potential site of dimeric interaction, with six residues <3Å apart. In particular, NIS residues Y242, T243, and Q471 were identified as critical to dimerization. Individual mutation of residues Y242 and T243 rendered NIS nonfunctional, while abrogation of Q471 did not impact radioiodide uptake. FRET data show that the putative dimerization interface can tolerate the loss of one, but not two, of these three clustered residues. Conclusions: We show for the first time that NIS dimerizes in vitro, and we identify the key residues via which this happens. We hypothesize that dimerization of NIS is critical to its trafficking to the PM and may therefore represent a new mechanism that would need to be considered in overcoming therapeutic failure in patients with thyroid cancer.

Dataset Information

Photodissociation of Sodium Iodide Clusters Doped with Small Hydrocarbons.

Publications

Photodissociation of Sodium Iodide Clusters Doped with Small Hydrocarbons.

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