Schisanwilsonin H

Spectroscopic characteristics of Rubricoccus marinus xenorhodopsin (RmXeR) and a putative model for its inward H(+) transport mechanism.[Pubmed:29034950]

Phys Chem Chem Phys. 2018 Jan 31;20(5):3172-3183.

A new group of microbial rhodopsins named xenorhodopsins (XeR), which are closely related to the cyanobacterial Anabaena sensory rhodopsin, show a light-driven "inward" proton transport activity, as reported for one representative of this group from Parvularcula oceani (PoXeR). In this study, we functionally and spectroscopically characterized a new member of the XeR clade from a marine bacterium Rubricoccus marinus SG-29(T) (RmXeR). Escherichia coli cells expressing recombinant RmXeR showed a light-induced alkalization of the cell suspension, which was strongly impaired by a protonophore, suggesting that RmXeR is a light-driven "inward" proton pump as is PoXeR. The spectroscopic properties of purified RmXeR were investigated and compared with those of PoXeR and a light-driven "outward" proton pump, bacteriorhodopsin (BR) from the archaeon Halobacterium salinarum. Action spectroscopy revealed that RmXeR with all-trans retinal is responsible for the light-driven inward proton transport activity, but not with 13-cis retinal. From pH titration experiments and mutational analysis, we estimated the pKa values for the protonated Schiff base of the retinal chromophore and its counterion as 11.1 +/- 0.07 and 2.1 +/- 0.07, respectively. Of note, the direction of both the retinal composition change upon light-dark adaptation and the acid-induced spectral shift was opposite that of BR, which is presumably related to the opposite directions of ion transport (from outside to inside for RmXeR and from inside to outside for BR). Flash photolysis experiments revealed the appearances of three intermediates (L, M and O) during the photocycle. The proton uptake and release were coincident with the formation and decay of the M intermediate, respectively. Together with associated findings from other microbial rhodopsins, we propose a putative model for the inward proton transport mechanism of RmXeR.

In vivo characterization of the downfield part of (1) H MR spectra of human brain at 9.4 T: Magnetization exchange with water and relation to conventionally determined metabolite content.[Pubmed:29034505]

Magn Reson Med. 2018 Jun;79(6):2863-2873.

PURPOSE: To perform exchange-rate measurements on the in vivo human brain downfield spectrum (5-10 ppm) at 9.4 T and to compare the variation in concentrations of the downfield resonances and of known upfield metabolites to determine potential peak labels. METHODS: Non-water-suppressed metabolite cycling was used in combination with an inversion transfer technique in two brain locations in healthy volunteers to measure the exchange rates and T1 values of exchanging peaks. Spectra were fitted with a heuristic model of a series of 13 or 14 Voigt lines, and a Bloch-McConnell model was used to fit the exchange rate curves. Concentrations from non-water-inverted spectra upfield and downfield were compared. RESULTS: Mean T1 values ranged from 0.40 to 0.77 s, and exchange rates from 0.74 to 13.8 s(-1) . There were no significant correlations between downfield and upfield concentrations, except for N-acetylaspartate, with a correlation coefficient of 0.63 and P < 0.01. CONCLUSIONS: Using ultrahigh field allowed improved separation of peaks in the 8.2 to 8.5 ppm amide proton region, and the exchange rates of multiple downfield resonances including the 5.8-ppm peak, previously tentatively assigned to urea, were measured in vivo in human brain. Downfield peaks consisted of overlapping components, and largely missing correlations between upfield and downfield resonances-although not conclusive-indicate limited contributions from metabolites present upfield to the downfield spectrum. Magn Reson Med 79:2863-2873, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.

Cu(I) Coordination Polymers as the Green Heterogeneous Catalysts for Direct C-H Bonds Activation of Arylalkanes to Ketones in Water with Spatial Confinement Effect.[Pubmed:29035050]

Inorg Chem. 2017 Nov 6;56(21):13329-13336.

To develop coordination polymers (CPs) as catalysts to selectively catalyze the reaction of C-H bond activation of arylalkanes to their homologous ketones, three new Cu(I)-based coordination polymers (Cu(I)-CPs) [CuI(aas-TPB)]n (1), [CuBr(ass-TPB)CH3CN]n (2), and {[Cu(ass-TPB)]Cl}n (3) (TPB = N,N,N-tris(3-pyridinyl)-1,3,5-benzenetricarboxamide) were synthesized. Structural variations from a herringbone fashion one-dimensional framework of 1 to a two-dimensional framework of 2 containing a 48-membered macrocycle and a cationic three-dimensional framework of 3 filled with Cl(-) anions were observed arising from the different halogen ions (I(-), Br(-), and Cl(-)). 1-3 were used as the green heterogeneous catalysts to catalyze direct C-H bond activation reactions of arylalkanes to ketones under mild reaction conditions with water as solvent. Handy product separation, convenient reaction procedures, and recyclability of these catalysts make the catalytic system fascinating. Moreover, the Cu(I)-CPs performed the reaction with high regioselectivity due to the unique spatial confinement effect of CPs.