Expanding Reaction Horizons: Evidence of the 5-Deazaflavin Radical Through Photochemically Induced Dynamic Nuclear Polarization.

Deazaflavins are important analogues of the naturally occurring flavins: riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). The use of 5-deazaflavin as a replacement coenzyme in a number of flavoproteins has proven particularly valuable in unraveling and manipulating their reaction mechanisms. It was frequently reported that one-electron-transfer reactions in flavoproteins are impeded with 5-deazaflavin as the cofactor. Based on these findings, it was concluded that the 5-deazaflavin radical is significantly less stable compared to the respective flavin semiquinone and quickly re-oxidizes or undergoes disproportionation. The long-standing paradigm of 5-deazaflavin being solely a two-electron/hydride acceptor/donor-"a nicotinamide in flavin clothing"-needs to be re-evaluated now with the indirect observation of a one-electron-reduced (paramagnetic) species using photochemically induced dynamic nuclear polarization (photo-CIDNP) 1 H nuclear magnetic resonance (NMR) under biologically relevant conditions.

Lifetime of Parahydrogen in Aqueous Solutions and Human Blood.

Molecular hydrogen has unique nuclear spin properties. Its nuclear spin isomer, parahydrogen (pH2 ), was instrumental in the early days of quantum mechanics and allows to boost the NMR signal by several orders of magnitude. pH2- induced polarization (PHIP) is based on the survival of pH2 spin order in solution, yet its lifetime has not been investigated in aqueous or biological media required for in vivo applications. Herein, we report longitudinal relaxation times (T1 ) and lifetimes of pH2 ( τPOC ) in methanol and water, with or without O2 , NaCl, rhodium-catalyst or human blood. Furthermore, we present a relaxation model that uses T1 and τPOC for more precise theoretical predictions of the H2 spin state in PHIP experiments. All measured T1 values were in the range of 1.4-2 s and τPOC values were of the order of 10-300 minutes. These relatively long lifetimes hold great promise for emerging in vivo implementations and applications of PHIP.

Non-classical disproportionation revealed by photo-chemically induced dynamic nuclear polarization NMR.

Photo-chemically induced dynamic nuclear polarization (photo-CIDNP) was used to observe the light-induced disproportionation reaction of 6,7,8-trimethyllumazine starting out from its triplet state to generate a pair of radicals comprising a one-electron reduced and a one-electron oxidized species. Our evidence is based on the measurement of two marker proton hyperfine couplings, Aiso(H(6α)) and Aiso(H(8α)), which we correlated to predictions from density functional theory. The ratio of these two hyperfine couplings is reversed in the oxidized and the reduced radical species. Observation of the dismutation reaction is facilitated by the exceptional C-H acidity of the methyl group at position 7 of 6,7,8-trimethyllumazine and the slow proton exchange associated with it, which leads to NMR-distinguishable anionic (TML-) and neutral (TMLH) protonation forms.

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.

A 1-phytase type III effector interferes with plant hormone signaling.

Most Gram-negative phytopathogenic bacteria inject type III effector (T3E) proteins into plant cells to manipulate signaling pathways to the pathogen's benefit. In resistant plants, specialized immune receptors recognize single T3Es or their biochemical activities, thus halting pathogen ingress. However, molecular function and mode of recognition for most T3Es remains elusive. Here, we show that the Xanthomonas T3E XopH possesses phytase activity, i.e., dephosphorylates phytate (myo-inositol-hexakisphosphate, InsP6), the major phosphate storage compound in plants, which is also involved in pathogen defense. A combination of biochemical approaches, including a new NMR-based method to discriminate inositol polyphosphate enantiomers, identifies XopH as a naturally occurring 1-phytase that dephosphorylates InsP6 at C1. Infection of Nicotiana benthamiana and pepper by Xanthomonas results in a XopH-dependent conversion of InsP6 to InsP5. 1-phytase activity is required for XopH-mediated immunity of plants carrying the Bs7 resistance gene, and for induction of jasmonate- and ethylene-responsive genes in N. benthamiana.