Completing the Picture: Determination of 13C Hyperfine Coupling Constants of Flavin Semiquinone Radicals by Photochemically Induced Dynamic Nuclear Polarization Spectroscopy.

We investigate the electronic structure of flavin semiquinone radicals in terms of their 13C hyperfine coupling constants. Photochemically induced dynamic nuclear polarization (photo-CIDNP) spectroscopy was used to study both the neutral and anionic radical species of flavin mononucleotide (FMN) in bulk aqueous solution. Apart from universally 13C-labeled FMN, partially labeled isotopologues are used to increase sensitivity for nuclei exhibiting very small hyperfine couplings and to cope with spectral overlap. In addition, experimental findings are supported by quantum chemical calculations, and implications for the spin density distribution in free flavin radicals are discussed.

J-Edited DIffusional Proton Nuclear Magnetic Resonance Spectroscopic Measurement of Glycoprotein and Supramolecular Phospholipid Biomarkers of Inflammation in Human Serum.

Proton nuclear magnetic resonance (NMR) N-acetyl signals (Glyc) from glycoproteins and supramolecular phospholipids composite peak (SPC) from phospholipid quaternary nitrogen methyls in subcompartments of lipoprotein particles) can give important systemic metabolic information, but their absolute quantification is compromised by overlap with interfering resonances from lipoprotein lipids themselves. We present a J-Edited DIffusional (JEDI) proton NMR spectroscopic approach to selectively augment signals from the inflammatory marker peaks Glyc and SPCs in blood serum NMR spectra, which enables direct integration of peaks associated with molecules found in specific compartments. We explore a range of pulse sequences that allow editing based on peak J-modulation, translational diffusion, and T2 relaxation time and validate them for untreated blood serum samples from SARS-CoV-2 infected patients (n = 116) as well as samples from healthy controls and pregnant women with physiological inflammation and hyperlipidemia (n = 631). The data show that JEDI is an improved approach to selectively investigate inflammatory signals in serum and may have widespread diagnostic applicability to disease states associated with systemic inflammation.

Metabolic alterations in meningioma reflect the clinical course.

BACKGROUND: Meningiomas are common brain tumours that are usually defined by benign clinical course. However, some meningiomas undergo a malignant transformation and recur within a short time period regardless of their World Health Organization (WHO) grade. The current study aimed to identify potential markers that can discriminate between benign and malignant meningioma courses. METHODS: We profiled the metabolites from 43 patients with low- and high-grade meningiomas. Tumour specimens were analyzed by nuclear magnetic resonance analysis; 270 metabolites were identified and clustered with the AutoPipe algorithm. RESULTS: We observed two distinct clusters marked by alterations in glycine/serine and choline/tryptophan metabolism. Glycine/serine cluster showed significantly lower WHO grades and proliferation rates. Also progression-free survival was significantly longer in the glycine/serine cluster. CONCLUSION: Our findings suggest that alterations in glycine/serine metabolism are associated with lower proliferation and more recurrent tumours. Altered choline/tryptophan metabolism was associated with increases proliferation, and recurrence. Our results suggest that tumour malignancy can be reflected by metabolic alterations, which may support histological classifications to predict the clinical outcome of patients with meningiomas.

pH Tuning of Water-Soluble Arylazopyrazole Photoswitches.

Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermal half-lives and facile synthetic access. Understanding pathways for a simple modulation of the thermal half-lives, while keeping other parameters of interest constant, is an important aspect for out-of-equilibrium systems design and applications. Here, it is demonstrated that the thermal half-life of a water-soluble PEG-tethered arylazo-bis(o-methylated)pyrazole (AAP) can be tuned by more than five orders of magnitude using simple pH adjustment, which is beyond the tunability of azobenzenes. The mechanism of thermal relaxation is investigated by thorough spectroscopic analyses and density functional theory (DFT) calculations. Finally, the concepts of a tunable half-life are transferred from the molecular scale to the material scale. Based on the photochromic characteristics of E- and Z-AAP, transient information storage is showcased in form of light-written patterns inside films cast from different pH, which in turn leads to different times of storage. With respect to prospective precisely tunable materials and time-programmed out-of-equilibrium systems, an externally tunable half-life is likely advantageous over changing the entire system by the replacement of the photoswitch.

Detection of magnetic field effects by confocal microscopy.

Certain pairs of paramagnetic species generated under conservation of total spin angular momentum are known to undergo magnetosensitive processes. Two prominent examples of systems exhibiting these so-called magnetic field effects (MFEs) are photogenerated radical pairs created from either singlet or triplet molecular precursors, and pairs of triplet states generated by singlet fission. Here, we showcase confocal microscopy as a powerful technique for the investigation of such phenomena. We first characterise the instrument by studying the field-sensitive chemistry of two systems in solution: radical pairs formed in a cryptochrome protein and the flavin mononucleotide/hen egg-white lysozyme model system. We then extend these studies to single crystals. Firstly, we report temporally and spatially resolved MFEs in flavin-doped lysozyme single crystals. Anisotropic magnetic field effects are then reported in tetracene single crystals. Finally, we discuss the future applications of confocal microscopy for the study of magnetosensitive processes with a particular focus on the cryptochrome-based chemical compass believed to lie at the heart of animal magnetoreception.

Influence of the cofactor structure on the photophysical processes initiating signal transduction in a phototropin-derived LOV domain.

Due to their biological importance, the photochemistry of blue-light photoreceptor proteins has been studied extensively over the last few decades. Most blue-light photoreceptors, such as cryptochromes and phototropins, utilize flavin chromophores as their cofactors. After irradiation with light, the chromophore undergoes electron transfer with nearby redox-active amino-acid residues within the protein, whereby this first step of signal transduction may be initiated either from the flavin's excited singlet or triplet state. Despite the collective effort of theoreticians and experimentalists to characterize and understand the photochemistry of flavoproteins, the mechanistic details of the excited state processes initiating signal transduction are yet to be revealed. Here, we use a light-oxygen-voltage-sensing domain from Avena sativa phototropin to get additional insight into the excited state photochemistry of flavoproteins. The influence of structural variations of the cofactor flavin mononucleotide (FMN) is explored by varying the methyl substitution pattern in positions 7 and 8 of the flavin core. The photophysical properties of the FMN derivatives, in the absence and presence of the protein environment, are investigated by UV-vis absorption, fluorescence, and electron paramagnetic resonance spectroscopies as well as cyclic voltammetry. The comparison of the properties of the modified flavin cofactors with those of FMN shows that the rates of the different excited state reactions, and therefore also the singlet/triplet yields, can be modulated substantially by only minor structural modifications of the flavin core.

Methyl groups matter: Photo-CIDNP characterizations of the semiquinone radicals of FMN and demethylated FMN analogs.

In this contribution, the relative hyperfine couplings are determined for the 1H nuclei of the flavin mononucleotide (FMN) radical in an aqueous environment. In addition, three structural analogs with different methylation patterns are characterized and the influence of the substituents at the isoalloxazine moiety on the electronic structure of the radicals is explored. By exploiting nuclear hyperpolarization generated via the photo-CIDNP (chemically induced dynamic nuclear polarization) effect, it is possible to study the short-lived radical species generated by in situ light excitation. Experimental data are extracted by least-squares fitting and supported by quantum chemical calculations and published values from electron paramagnetic resonance and electron-nuclear double resonance. Furthermore, mechanistic details of the photoreaction of the investigated flavin analogs with l-tryptophan are derived from the photo-CIDNP spectra recorded at different pH values. Thereby, the neutral and anionic radicals of FMN and three structural analogs are, for the first time, characterized in terms of their electronic structure in an aqueous environment.

Synergetic effects of Fe3+ doped spinel Li4Ti5O12 nanoparticles on reduced graphene oxide for high surface electrode hybrid supercapacitors.

In this work, reduced graphene oxide (rGO) based electrode materials were developed to achieve a hybrid supercapacitor (SC) function. Therefore, several synthesis methods were developed to prepare a cost effective and environmentally friendly rGO. Additionally, to maintain the high surface area, spinel lithium titanate (sLTO) nanoparticles (NPs) were synthesized and deposited on the rGO surface to inhibit the restacking of the rGO layers on graphite. Furthermore, the adequate Fe-doping of sLTO increased the ionic conductivity and the intercalation capacity, which is necessary for a SC performance. The sLTO/rGO-composites were electrochemically analysed by chronopotentiometry and electrochemical impedance spectroscopy (EIS) to determine the stability during charge/discharge cycling and the capacity, respectively. To overcome the drawback of LTO's low conductivity values, its value has been drastically increased by Fe-doping. The results demonstrated the remarkable cycling performance of the Fe:LTO/rGO composite as well as a higher capacity compared to LTO/rGO and pure rGO-electrodes. The thermal stability, degradation and weight loss of the sLTO/rGO in the temperature range between 20 °C and 800 °C were investigated by thermogravimetry (TG)/DTA. As a conclusion, it can be stated that, increasing the ionic conductivity by Fe-doping drastically increases the hybrid capacity of the SC electrodes.

Microenvironment-Derived Regulation of HIF Signaling Drives Transcriptional Heterogeneity in Glioblastoma Multiforme.

The evolving and highly heterogeneous nature of malignant brain tumors underlies their limited response to therapy and poor prognosis. In addition to genetic alterations, highly dynamic processes, such as transcriptional and metabolic reprogramming, play an important role in the development of tumor heterogeneity. The current study reports an adaptive mechanism in which the metabolic environment of malignant glioma drives transcriptional reprogramming. Multiregional analysis of a glioblastoma patient biopsy revealed a metabolic landscape marked by varying stages of hypoxia and creatine enrichment. Creatine treatment and metabolism was further shown to promote a synergistic effect through upregulation of the glycine cleavage system and chemical regulation of prolyl-hydroxylase domain. Consequently, creatine maintained a reduction of reactive oxygen species and change of the α-ketoglutarate/succinate ratio, leading to an inhibition of HIF signaling in primary tumor cell lines. These effects shifted the transcriptional pattern toward a proneural subtype and reduced the rate of cell migration and invasion in vitroImplications: Transcriptional subclasses of glioblastoma multiforme are heterogeneously distributed within the same tumor. This study uncovered a regulatory function of the tumor microenvironment by metabolism-driven transcriptional reprogramming in infiltrating glioma cells. Mol Cancer Res; 16(4); 655-68. ©2018 AACR.

The integrative metabolomic-transcriptomic landscape of glioblastome multiforme.

The purpose of this study was to map the landscape of metabolic-transcriptional alterations in glioblastoma multiforme. Omic-datasets were acquired by metabolic profiling (1D-NMR spectroscopy n=33 Patient) and transcriptomic profiling (n=48 Patients). Both datasets were analyzed by integrative network modeling. The computed model concluded in four different metabolic-transcriptomic signatures containing: oligodendrocytic differentiation, cell-cycle functions, immune response and hypoxia. These clusters were found being distinguished by individual metabolism and distinct transcriptional programs. The study highlighted the association between metabolism and hallmarks of oncogenic signaling such as cell-cycle alterations, immune escape mechanism and other cancer pathway alterations. In conclusion, this study showed the strong influence of metabolic alterations in the wide scope of oncogenic transcriptional alterations.