Fibroblast growth factor 21 alleviates diabetes-induced cognitive decline.

Diabetes mellitus (DM) causes damage to the central nervous system, resulting in cognitive impairment. Fibroblast growth factor 21 (FGF21) exhibits the potential to alleviate neurodegeneration. However, the therapeutic effect of intracerebroventricular (i.c.v) FGF21 infusion on diabetes-induced cognitive decline (DICD) and its potential mechanisms remain unclear. In this study, the impact of FGF21 on DICD was explored, and 1H nuclear magnetic resonance (NMR)-based metabolomics plus 13C NMR spectroscopy in combine with intravenous [1-13C]-glucose infusion were used to investigate the underlying metabolic mechanism. Results revealed that i.c.v FGF21 infusion effectively improved learning and memory performance of DICD mice; neuron loss and apoptosis in hippocampus and cortex were significantly blocked, suggesting a potential neuroprotective role of FGF21 in DICD. Metabolomics results revealed that FGF21 modulated DICD metabolic alterations related to glucose and neurotransmitter metabolism, which are characterized by distinct recovered enrichment of [3-13C]-lactate, [3-13C]-aspartate, [4-13C]-glutamine, [3-13C]-glutamine, [4-13C]-glutamate, and [4-13C]- γ-aminobutyric acid (GABA) from [1-13C]-glucose. Moreover, diabetes-induced neuron injury and metabolic dysfunctions might be mediated by PI3K/AKT/GSK-3ß signaling pathway inactivation in the hippocampus and cortex, which were activated by i.c.v injection of FGF21. These findings indicate that i.c.v FGF21 infusion exerts its neuroprotective effect on DICD by remodeling cerebral glucose and neurotransmitter metabolism by activating the PI3K/AKT/GSK-3ß signaling pathway.

Targeted removal of the FA2 site on human albumin prevents fatty acid-mediated inhibition of Zn2+ binding.

Zinc is required for virtually all biological processes. In plasma, Zn2+ is predominantly transported by human serum albumin (HSA), which possesses two Zn2+-binding sites of differing affinities (sites A and B). Fatty acids (FAs) are also transported by HSA, with seven structurally characterized FA-binding sites (named FA1-FA7) known. FA binding inhibits Zn2+-HSA interactions, in a manner that can impact upon hemostasis and cellular zinc uptake, but the degree to which binding at specific FA sites contributes to this inhibition is unclear. Wild-type HSA and H9A, H67A, H247A, and Y150F/R257A/S287A (FA2-KO) mutant albumins were expressed in Pichia pastoris. Isothermal titration calorimetry studies revealed that the Zn2+-binding capacity at the high-affinity Zn2+ site (site A) was reduced in H67A and H247A mutants, with site B less affected. The H9A mutation decreased Zn2+ binding at the lower-affinity site, establishing His9 as a site B ligand. Zn2+ binding to HSA and H9A was compromised by palmitate, consistent with FA binding affecting site A. 13C-NMR experiments confirmed that the FA2-KO mutations prohibited FA binding at site FA2. Zn2+ binding to the FA2-KO mutant was unaffected by myristate, suggesting binding at FA2 is solely responsible for inhibition. Molecular dynamics studies identified the steric obstruction exerted by bound FA in site FA2, which impedes the conformational change from open (FA-loaded) to closed (FA-free) states, required for Zn2+ to bind at site A. The successful targeting of the FA2 site will aid functional studies exploring the interplay between circulating FA levels and plasma Zn2+ speciation in health and disease.

Controlling the Activation at NiII-CO2 2- Moieties through Lewis Acid Interactions in the Second Coordination Sphere.

Nickel complexes with a two-electron reduced CO2 ligand (CO2 2-, "carbonite") are investigated with regard to the influence alkali metal (AM) ions have as Lewis acids on the activation of the CO2 entity. For this purpose complexes with NiII(CO2)AM (AM=Li, Na, K) moieties were accessed via deprotonation of nickel-formate compounds with (AM)N(iPr)2. It was found that not only the nature of the AM ions in vicinity to CO2 affect the activation, but also the number and the ligation of a given AM. To this end the effects of added (AM)N(R)2, THF, open and closed polyethers as well as cryptands were systematically studied. In 14 cases the products were characterized by X-ray diffraction and correlations with the situation in solution were made. The more the AM ions get detached from the carbonite ligand, the lower is the degree of aggregation. At the same time the extent of CO2 activation is decreased as indicated by the structural and spectroscopic analysis and reactivity studies. Accompanying DFT studies showed that the coordinating AM Lewis acidic fragment withdraws only a small amount of charge from the carbonite moiety, but it also affects the internal charge equilibration between the LtBuNi and carbonite moieties.

Penicimides A and B, two novel diels-alder [4 + 2] cycloaddition ergosteroids from Penicillium herquei.

Two novel naturally occurring [4 + 2] Diels-Alder cycloaddition ergosteroids (1 and 2), three undescribed oxidized ergosteroids (3-5), and eleven known analogs (6-16) were isolated from Penicillium herquei. Compounds 1 and 2 represent the first reported cycloadducts of a steroid with 1,4,6-trimethyl-1,6-dihydropyridine-2,5-dione or 4,6-dimethyl-1,6-dihydropyridine-2,5-dione to date. Compound 3 is the C-15 epimer of (22E,24R)-9α,11ß-dihydroxyergosta-4,6,8(14),22-tetraen-3-one (14). The chemical structures of these compounds were elucidated through widespread spectroscopic analyses, mainly including HRESIMS and 1D and 2D NMR data, calculated 13C NMR-DP4+ analysis, and electronic circular dichroism (ECD) data analyses. Biological evaluations of Compounds 1-16 revealed that 3, 9-11, and 15 inhibited the production of NO in LPS-induced RAW264.7 cells with an IC50 value from 7.37 ± 0.69 to 38.9 ± 2.25 µM (the positive control dexamethasone IC50: 9.54 ± 0.71 µM). In addition, Compound 3 exhibited a potent inhibitory effect on the secretion of the proinflammatory cytokines TNF-α and IL-6, the transcription level of the proinflammatory macrophage markers TNF-α, and the expression of the iNOS protein.

Phenolic syringyl end groups in 13C-enriched hardwoods detected and quantified by solid-state NMR.

While syringyl units are the most abundant monolignols in hardwood lignin, their phenolic (i.e. hydroxyl) end group concentration has not been measured. In two uniformly 13C-enriched young hardwoods, from beech and oak, the syringyl units were quantitatively investigated by advanced solid-state 13C NMR. Small signals of OH-terminated syringyl units were resolved in spectrally edited two-dimensional 13C-13C NMR spectra of the two hardwoods. Their distinct peak positions predicted based on literature data were validated via the abundant OH-terminated syringyl units in hydrolyzed 13C-beechwood. In a two-dimensional 13C-13C exchange spectrum with diagonal-ridge suppression, a well-resolved peak of phenolic syringyl units was observed at the characteristic C-H peak position of syringyl rings, without significant overlap from guaiacyl peaks. Accurate 13C chemical shifts of regular and end-group syringyl units were obtained. Through spectrally edited 2D NMR after 1H inversion recovery, phenols of condensed tannin complexed with arginine were carefully analyzed and shown to overlap minimally with signals from phenolic syringyl units. The local structure and resulting spin dynamics of ether (chain) and hydroxyl (end-group) syringyl units are nearly the same, enabling quantification by peak integration or deconvolution, which shows that phenolic syringyl end groups account for 2 ± 1 % of syringyl units in beechwood and 5 ± 2 % in oakwood. The observed low end-group concentration needs to be taken into account in realistic molecular models of hardwood lignin structure.

Exploring the role of neutral ligands in modulating the photoluminescence of samarium complexes with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.

Four eight-coordinated luminescent samarium complexes of type [Sm(hfpd)3L2] and [Sm(hfpd)3L'] [where hfpd = 1,1,1,5,5,5-Hexafluoro-2,4-pentanedione L = tri-octyl-phosphine oxide (TOPO) and L' = 1,10-phenanthroline (phen), neocuproine (neoc) and bathocuproine (bathoc) were synthesized via a stoichiometrically controlled approach. This allows for precise control over the stoichiometry of the complexes, leading to reproducible properties. This investigation focuses on understanding the impact of secondary ligands on the luminescent properties of these complexes. Infrared (IR) spectra provided information about the molecular structures, whereas 1H and 13C nuclear magnetic resonance (NMR) spectra confirmed these structural details along with the coordination of ligands to trivalent Sm ion. The UV-vis spectra revealed the molar absorption coefficient and absorption bands associated with the hfpd ligand and photoluminescence (PL) spectroscopy demonstrated intense orange-red emission (648 nm relative to 4G5/2 → 6H9/2) from the complexes. The Commission Internationale de l'Éclairage (CIE) triangles indicated that the complexes emitted warm orange red light with color coordinates (x, y) ranging from (0.62, 0.36) to (0.40, 0.27). The investigation of the band gap as well as color parameters confirms the utility of these complexes in displays and LEDs.

13 C NMR as an analytical tool for the detection of carbonic acid and pKa determination.

NMR spectroscopy has become a standard technique in studies both on carbon capture and storage. 13 C NMR allows the detection of two peaks for carbonated aqueous samples: one for CO2(aq) and another one for the species H2 CO3 , HCO3 - , and CO3 2- -herein collectively named Hx CO3 x-2 . The chemical shift of this second peak depends on the molar fraction of the three species in equilibrium and has been used to assess the equilibrium between HCO3 - and CO3 2- . The detection of H2 CO3 at low pH solutions is hindered, because of the concurrent liberation of CO2 when the medium is acidified. Herein, a valved NMR tube facilitates the detection of the Hx CO3 x-2 peak across a wide pH range, even at pH 1.8 where the dominant species is H2 CO3 . The method employed the formation of frozen layers of NaH13 CO3 and acid solutions within the tube, which are mixed as the tube reaches room temperature. At this point, the tube is already securely sealed, preventing any loss of CO2 to the atmosphere. A spectrophotometry approach allowed the measurement of the actual pH inside the pressurized NMR tube. The chemical shift for H2 CO3 was determined as 160.33 ± 0.03 ppm, which is in good agreement with value obtained by DFT calculations combined with Car-Parrinello molecular dynamics. The H2 CO3 pKa value determined by the present method was 3.41 ± 0.03, for 15% D2 O aqueous medium and 0.8 mol/L ionic strength. The proposed method can be extended to studies about analogs such as alkyl carbonic and carbamic acids.

Computational NMR Study of Benzothienoquinoline Heterohelicenes.

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon-carbon bonds in the interior of the helical turn of the molecule based on the progressive upfield shift of 13C resonances toward the center of the helical turn. We now report a comprehensive analysis of the optimized geometry and a comparison of the calculated vs. observed 1H and 13C NMR chemical shifts of nineteen representative benzothienoquinoline heterohelicenes. As was initially hypothesized on the basis of the progressive upfield shift of carbon resonances toward the center of the interior helical turn, the present computational study has demonstrated that carbon-carbon bonds indeed have more sp3 character and are longer than normal sp2 bonds to accommodate the helical twist of the molecule, as expected.

Isolation and Structure Analysis of Chitin Obtained from Different Developmental Stages of the Mulberry Silkworm (Bombyx mori).

Chitin, a ubiquitous biopolymer, holds paramount scientific and economic significance. Historically, it has been primarily isolated from marine crustaceans. However, the surge in demand for chitin and the burgeoning interest in biopolymers have necessitated the exploration of alternative sources. Among these methods, the mulberry silkworm (Bombyx mori) has emerged as a particularly intriguing prospect. To isolate chitin from Bombyx mori, a chemical extraction methodology was employed. This process involved a series of meticulously orchestrated steps, including Folch extraction, demineralization, deproteinization, and decolorization. The resultant chitin was subjected to comprehensive analysis utilizing techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 13C nuclear magnetic resonance (NMR) spectroscopy, and wide-angle X-ray scattering (WAXS). The obtained results allow us to conclude that the Bombyx mori represents an attractive alternative source of α-chitin.

Spatial arrangements of cyclodextrin host-guest complexes in solution studied by 13C NMR and molecular modelling.

13C NMR spectroscopic analyses of Cs symmetric guest molecules in the cyclodextrin host cavity, combined with molecular modelling and solid-state X-ray analysis, provides a detailed description of the spatial arrangement of cyclodextrin host-guest complexes in solution. The chiral cavity of the cyclodextrin molecule creates an anisotropic environment for the guest molecule resulting in a splitting of its prochiral carbon signals in 13C NMR spectra. This signal split can be correlated to the distance of the guest atoms from the wall of the host cavity and to the spatial separation of binding sites preferred by pairs of prochiral carbon atoms. These measurements complement traditional solid-state analyses, which rely on the crystallization of host-guest complexes and their crystallographic analysis.

Paramagnetic NMR to study iron sulfur proteins: 13C detected experiments illuminate the vicinity of the metal center.

The robustness of NMR coherence transfer in proximity of a paramagnetic center depends on the relaxation properties of the nuclei involved. In the case of Iron-Sulfur Proteins, different pulse schemes or different parameter sets often provide complementary results. Tailored versions of HCACO and CACO experiments significantly increase the number of observed Cα/C' connectivities in highly paramagnetic systems, by recovering many resonances that were lost due to paramagnetic relaxation. Optimized 13C direct detected experiments can significantly extend the available assignments, improving the overall knowledge of these systems. The different relaxation properties of Cα and C' nuclei are exploited in CACO vs COCA experiments and the complementarity of the two experiments is used to obtain structural information. The two [Fe2S2]+ clusters containing NEET protein CISD3 and the one [Fe4S4]2+ cluster containing HiPIP protein PioC have been taken as model systems. We show that tailored experiments contribute to decrease the blind sphere around the cluster, to extend resonance assignment of cluster bound cysteine residues and to retrieve details on the topology of the iron-bound ligand residues.

13 C NMR quantification of polyamine syntheses in rat prostate.

Currently, many prostate cancer patients, detected through the prostate specific antigen test, harbor organ-confined indolent disease that cannot be differentiated from aggressive cancer according to clinically and pathologically known measures. Spermine has been considered as an endogenous inhibitor for prostate-confined cancer growth and its expression has shown correlation with prostate cancer growth rates. If established clinically, measurements of spermine bio-synthesis rates in prostates may predict prostate cancer growth and patient outcomes. Using rat models, we tested the feasibility of quantifying spermine bio-synthesis rates with 13 C NMR. Male Copenhagen rats (10 weeks, n = 6) were injected with uniformly 13 C-labeled L-ornithine HCl, and were sacrificed in pairs at 10, 30, and 60 min after injection. Another two rats were injected with saline and sacrificed at 30 min as controls. Prostates were harvested and extracted with perchloric acid and the neutralized solutions were examined by 13 C NMR at 600 MHz. 13 C NMR revealed measurable ornithine, as well as putrescine-spermidine-spermine syntheses in rat prostates, allowing polyamine bio-synthetic and ornithine bio-catabolic rates to be calculated. Our study demonstrated the feasibility of 13 C NMR for measuring bio-synthesis rates of ornithine to spermine enzymatic reactions in rat prostates. The current study established a foundation upon which future investigations of protocols that differentiate prostate cancer growth rates according to the measure of ornithine to spermine bio-synthetic rates may be developed.

Oxidation of hyperpolarized [1-13 C]pyruvate in isolated rat kidneys.

Kidneys play a central role in numerous disorders but current imaging methods have limited utility to probe renal metabolism. Hyperpolarized (HP) 13 C magnetic resonance imaging is uniquely suited to provide metabolite-specific information about key biochemical pathways and it offers the further advantage that renal imaging is practical in humans. This study evaluated the feasibility of hyperpolarization examinations in a widely used model for analysis of renal physiology, the isolated kidney, which enables isolation of renal metabolism from the effects of other organs and validation of HP results by independent measurements. Isolated rat kidneys were supplied with either HP [1-13 C]pyruvate only or HP [1-13 C]pyruvate plus octanoate. Metabolic activity in both groups was confirmed by stable renal oxygen consumption. HP [1-13 C]pyruvate was readily metabolized to [13 C]bicarbonate, [1-13 C]lactate, and [1-13 C]alanine, detectable seconds after HP [1-13 C]pyruvate was injected. Octanoate suppressed but did not eliminate the production of HP [13 C]bicarbonate from [1-13 C]pyruvate. Steady-state flux analyses using non-HP 13 C substrates validated the utilization of HP [1-13 C]pyruvate, as observed by HP 13 C NMR. In the presence of octanoate, lactate is generated from a tricarboxylic acid cycle intermediate, oxaloacetate. The isolated rat kidney may serve as an excellent model for investigating and establishing new HP 13 C metabolic probes for future kidney imaging applications.

Drivers of microbially and plant-derived carbon in topsoil and subsoil.

Plant- and microbially derived carbon (C) are the two major sources of soil organic matter (SOM), and their ratio impacts SOM composition, accumulation, stability, and turnover. The contributions of and the key factors defining the plant and microbial C in SOM along the soil profile are not well known. By leveraging nuclear magnetic resonance spectroscopy and biomarker analysis, we analyzed the plant and microbial C in three soil types using regional-scale sampling and combined these results with a meta-analysis. Topsoil (0-40 cm) was rich in carbohydrates and lignin (38%-50%), whereas subsoil (40-100 cm) contained more proteins and lipids (26%-60%). The proportion of plant C increases, while microbial C decreases with SOM content. The decrease rate of the ratio of the microbially derived C to plant-derived C (CM:P ) with SOM content was 23%-30% faster in the topsoil than in the subsoil in the regional study and meta-analysis. The topsoil had high potential to stabilize plant-derived C through intensive microbial transformations and microbial necromass formation. Plant C input and mean annual soil temperature were the main factors defining CM:P in topsoil, whereas the fungi-to-bacteria ratio and clay content were the main factors influencing subsoil CM:P . Combining a regional study and meta-analysis, we highlighted the contribution of plant litter to microbial necromass to organic matter up to 1-m soil depth and elucidated the main factors regulating their long-term preservation.

Molecular Conformations of Shape Anisometrically Variant Mesogens in Liquid Crystalline Phase Studied by 13 C NMR Spectroscopy.

Mesogens that vary in shape anisometry have been investigated by 13 C solid-state NMR in the liquid crystalline phase to inspect the conformations. The molecules examined comprise of (i) rod-like mesogen with three-phenyl ring core and terminal hexyloxy chains, (ii) three-ring core linked to the fourth phenyl ring via a spacer, and (iii) trimesic acid connected to three side arms core units through a spacer. The order parameter (Szz ) values for the phenyl rings of the rod-like mesogen are 0.65-0.68, while the mesogen with a three-ring core linked to a phenyl ring via spacer showed dissimilarity. Consequently, for the core unit phenyl rings, Szz is ~0.70, and the terminal phenyl ring showed a low value of 0.12. For the trimesic acid based mesogen, the Szz value for the side arm phenyl rings is ~0.53, and for the central phenyl ring, a very low value of 0.11 is witnessed. By considering the ordering of the rod-like mesogen as a yardstick and employing the ratios of Szz values of the phenyl rings, the average conformations of other mesogens are arrived. Accordingly, for the trimesic acid based mesogen, a tripod-like conformation instead of λ shape is proposed in the liquid crystalline phase.

Differential Effects of Chronic Ethanol Use on Mouse Neuronal and Astroglial Metabolic Activity.

Chronic alcohol use disorder, a major risk factor for the development of neuropsychiatric disorders including addiction to other substances, is associated with several neuropathology including perturbed neuronal and glial activities in the brain. It affects carbon metabolism in specific brain regions, and perturbs neuro-metabolite homeostasis in neuronal and glial cells. Alcohol induced changes in the brain neurochemical profile accompany the negative emotional state associated with dysregulated reward and sensitized stress response to withdrawal. However, the underlying alterations in neuro-astroglial activities and neurochemical dysregulations in brain regions after chronic alcohol use are poorly understood. This study evaluates the impact of chronic ethanol use on the regional neuro-astroglial metabolic activity using 1H-[13C]-NMR spectroscopy in conjunction with infusion of [1,6-13C2]glucose and sodium [2-13C]acetate, respectively, after 48 h of abstinence. Besides establishing detailed 13C labeling of neuro-metabolites in a brain region-specific manner, our results show chronic ethanol induced-cognitive deficits along with a reduction in total glucose oxidation rates in the hippocampus and striatum. Furthermore, using [2-13C]acetate infusion, we showed an alcohol-induced increase in astroglial metabolic activity in the hippocampus and prefrontal cortex. Interestingly, increased astroglia activity in the hippocampus and prefrontal cortex was associated with a differential expression of monocarboxylic acid transporters that are regulating acetate uptake and metabolism in the brain.

Computational studies of [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline.

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon-carbon bonds in the interior of the helical turn of the molecule based on the progressive more shielded nature of 13 C resonances toward the center of the helical turn. Computational chemistry capabilities when those NMR studies were performed were primitive in comparison to what is now possible. We now report the optimized geometry and a comparison of the calculated versus observed 1 H and 13 C NMR chemical shift assignments for [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline that confirms these suspicions.

Corrected solid-state 13 C nuclear magnetic resonance peak assignment and side-group quantification of hydroxypropyl methylcellulose acetyl succinate pharmaceutical excipients.

Hydroxypropyl methylcellulose acetyl succinate (HPMCAS) is widely used as a pharmaceutical excipient, making a detailed understanding of its tunable structure important for formulation design. Several recently reported peak assignments in the solid-state 13 C NMR spectrum of HPMCAS have been corrected here using peak integrals in quantitative spectra, spectral editing, empirical chemical-shift predictions based on solution NMR, and full spectrum simulation analogous to deconvolution. Unlike in cellulose, the strong peak at 84 ppm must be assigned to C2 and C3 methyl ethers, instead of regular C4 of cellulose. The proposed assignment of signals at <65 ppm to OCH sites, including C5 of cellulose, could not be confirmed. CH2 spectral editing showed two resolved OCH2 bands, a more intense one from O-CH2 ethers of C6 at >69 ppm and a smaller one from its esters and possibly residual CH2 -OH groups, near 63 ppm. The strong intensities of resolved signals of acetyl, succinoyl, and oxypropyl substituents indicated the substitution of >85% of the OH groups in HPMCAS. The side-group concentrations in three different grades of HPMCAS were quantified.

Acrylamide derivatives: A dynamic nuclear magnetic resonance study.

Substituted acrylamides have found an extensive application in organic and medical chemistry; therefore, it is very important to get insight into their features such as electronic structure, spectral properties, and stereochemical transformations. A correct interpretation of the chemical behavior and biological activity of these heteroatomic systems is impossible without knowledge of the structure of stereodynamic forms and factors determining their relative stability. The structure and peculiarities of stereodynamic behavior of substituted acrylamides and their model compounds were studied by dynamic and multinuclear 1 H, 13 C, and 15 N nuclear magnetic resonance (NMR) spectroscopy in CDCl3 and DMSO-d6 solution. It has been established that acrylamides in solution are realized as Z- and E-isomers, with the E-rotamer being somewhat predominant. The obtained experimental values of the free activation energy of rotamers vary within 15-17 kcal/mol, depending on the stereochemical structure of the molecule. 15 N NMR spectroscopy is the most reliable and fastest method for determining the structural and stereochemical features of nitrogen-containing compounds.

Composition and Chemical Variability of the Essential Oil from Aerial Parts of Cladanthus scariosus, an Endemic Species to the Moroccan High Atlas.

Cladanthus scariosus (Ball) Oberpr. & Vogt is endemic to Moroccan High Atlas. It is known under the vernacular names Irezghi or Irezgui. Three essential oil samples have been isolated from aerial parts and analyzed by combination of chromatographic and spectroscopic techniques [gas chromatography (GC) in combination with retention indices (RI), gas chromatography-mass spectrometry (GC/MS) and 13 C-NMR spectroscopy]. The compositions of oil samples were dominated by monoterpenes: α-pinene sabinene, and terpinen-4-ol. Chamazulene and dihydrochamazulene isomers as well as various hemiterpene esters and analogs have been identified. To evidence a chemical variability, statistical analysis performed on 13 oil sample compositions allowed partitioning into three groups, mainly differentiated by their contents of sabinene, camphor, borneol, terpinen-4-ol, and germacrene D.