Nuclear Magnetic Resonance Spectroscopy Methods Research Articles

Cycling of labile and recalcitrant carboxyl-rich alicyclic molecules and carbohydrates in Baffin Bay

Marine dissolved organic matter (DOM) is an important, actively cycling carbon reservoir (662 GtC). However, the chemical structure and cycling of DOM within rapidly warming, polar environments remains largely unconstrained. Previous studies have shown rapid surface cycling of carbohydrates as biologically-labile DOM (LDOM). Conversely, carboxyl-rich alicyclic molecules (CRAM) are often used as examples of biologically-recalcitrant DOM (RDOM). Traditional DOM isolation methods (e.g., ultrafiltration (10–30% of DOM) and solid-phase extraction (40–60% of DOM) induce chemical-, size- and compositional-bias – complicating inferences to total DOM cycling. Here, we use a total DOM proton (1H) nuclear magnetic resonance (NMR) spectroscopy method to show carbohydrates and CRAM have high concentrations in the surface ocean and low concentrations at depth in Baffin Bay. Between 21–43% of surface CRAM is removed at depth. These results suggest both CRAM and carbohydrates are major LDOM constituents – contradicting the existing CRAM cycling paradigm and further constraining the long-term persistence of deep ocean DOM.

Quantification of CH and NH/π-Stacking Interactions in Cells Using Nuclear Magnetic Resonance Spectroscopy.

π-Stacking, a type of noncovalent interactions involving aromatic residues, plays an important role in protein folding and function. In this work, an attempt has been made to measure CH/π and NH/π stacking interactions in a protein in Escherichia coli cells using a combined double-mutant cycle and nuclear magnetic resonance spectroscopy method. The results show that the CH/π and NH/π stacking interactions are generally weaker in cells than those in the buffer. The transient intermolecular noncovalent interactions between the protein and the complex cellular environment may compete with and thus weaken the stacking interactions in the protein. The weakening of stacking interactions can enhance the local conformational opening of proteins in E. coli cells. This is evident from the faster rates of amide hydrogen/deuterium exchange observed in cells than in the buffer, for residues that undergo local conformational opening. This study highlights the influence of the cellular environment on π-stacking and the conformational dynamics of proteins.

Comprehensive phytochemical profiling of Phyllanthus emblica L. flowers on UHPLC/MS quadrupole time of flight, HPTLC, HPLC, and NMR analytical platforms reveals functional metabolites with potent anti-inflammatory effects in human (THP-1) macrophages.

Phyllanthus emblica L., renowned for its pharmacological benefits found in its fruits and leaves, has received considerable attention. However, there is a notable lack of research on its flowers, specifically on metabolite profiling and pharmacological activity. The present study aims to delineate the phytochemical constituents of hydromethanolic extract of P.emblica flowers by ultra-high-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UHPLC-QToF-MS), high-performance thin layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), infrared and nuclear magnetic resonance spectroscopic methods and subsequent evaluation of its anti-inflammatory potential. The identification and characterization of phytochemicals in P.emblica flowers was performed by UHPLC/MS-QToF in both positive and negative ionization modes. Additionally, marker compounds present in flower extract were analyzed using HPTLC, HPLC, FT-IR, and NMR methods. The anti-inflammatory potential was evaluated in lipopolysaccharide-stimulated THP-1 macrophages by evaluating inflammatory biomarkers. UHPLC/MS-QToF analysis facilitated the identification of 51 compounds from P.emblica flowers including gallic acid derivatives, flavonoid glycosides, and tannins based on their fragmentation patterns and previous literature reports. Notably, the study also identified spermidine compounds for the first time in this species. Optimization of HPTLC and HPLC methods marked the presence of corilagin as major compound followed by FT-IR and NMR spectral methods. Moreover, treatment with hydromethanolic extract of P.emblica flowers resulted in decreased levels of proinflammatory cytokines, TNF-α, IL-1β, and IL-6, alongside modulation of nuclear factor-κB activity in lipopolysaccharide-induced THP-1 macrophages. Chromatographic techniques in conjunction with spectral methods found robust prevalence in the identification of signature phytometabolites present in P. emblica flowers, which sets the basis for its anti-inflammatory potentials. The studies established a foundation for further exploration of potential applications of P. emblica flowers across various domains.

Three new diterpenoids, plectalibertellenones A–C, isolated from endolichenic fungi Pseudoplectania sp. EL000327

Three new pimarane diterpenoids, plectalibertellenones A−C (1–3), along with six known compounds, 9α-hydroxy-1,8(14),15-isopimaratrien-3,7,11-trione (4), 9α-hydroxy-1,8(14),15-isopimaratrien-3,11-dione (5), phomenone B (6), (−)-pestalotin (7), (+)-pestalotin (8), and 6-pentyl-4-methoxy-pyran-2-one (9) were isolated from the crude extract of an endolichenic fungus, Pseudoplectania sp. EL000327. The planar structures of metabolites 1–3 were elucidated using UV, mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopic data. The relative and absolute configurations of 1–3 were deduced from an interpretation of circular dichroism (CD) spectroscopic data, application of an advanced Mosher’s method, DP4+ calculations, and combination of NMR spectroscopic methods. Compounds 1–9 did not display any significant anti-bacterial activity; however, compounds 1–4 were cytotoxic to Caco2 cells, with IC50 values 54.8, 80.7, 76.4, and 19.6 µM, respectively.

Metabolic Deficits in the Retina of a Familial Dysautonomia Mouse Model.

Neurodegenerative retinal diseases such as glaucoma, diabetic retinopathy, Leber's hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA) are marked by progressive death of retinal ganglion cells (RGC). This decline is promoted by structural and functional mitochondrial deficits, including electron transport chain (ETC) impairments, increased oxidative stress, and reduced energy (ATP) production. These cellular mechanisms associated with progressive optic nerve atrophy have been similarly observed in familial dysautonomia (FD) patients, who experience gradual loss of visual acuity due to the degeneration of RGCs, which is thought to be caused by a breakdown of mitochondrial structures, and a disruption in ETC function. Retinal metabolism plays a crucial role in meeting the elevated energetic demands of this tissue, and recent characterizations of FD patients' serum and stool metabolomes have indicated alterations in central metabolic processes and potential systemic deficits of taurine, a small molecule essential for retina and overall eye health. The present study sought to elucidate metabolic alterations that contribute to the progressive degeneration of RGCs observed in FD. Additionally, a critical subpopulation of retinal interneurons, the dopaminergic amacrine cells, mediate the integration and modulation of visual information in a time-dependent manner to RGCs. As these cells have been associated with RGC loss in the neurodegenerative disease Parkinson's, which shares hallmarks with FD, a targeted analysis of the dopaminergic amacrine cells and their product, dopamine, was also undertaken. One dimensional (1D) proton (1H) nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and retinal histology methods were employed to characterize retinae from the retina-specific Elp1 conditional knockout (CKO) FD mouse model (Pax6-Cre; Elp1LoxP/LoxP). Metabolite alterations correlated temporally with progressive RGC degeneration and were associated with reduced mitochondrial function, alterations in ATP production through the Cahill and mini-Krebs cycles, and phospholipid metabolism. Dopaminergic amacrine cell populations were reduced at timepoints P30-P90, and dopamine levels were 25-35% lower in CKO retinae compared to control retinae at P60. Overall, this study has expanded upon our current understanding of retina pathology in FD. This knowledge may apply to other retinal diseases that share hallmark features with FD and may help guide new avenues for novel non-invasive therapeutics to mitigate the progressive optic neuropathy in FD.

Fingerprinting Organofluorine Molecules via Position-Specific Isotope Analysis.

Organofluorine substances are found in a wide range of materials and solvents commonly used in industry and homes, as well as pharmaceuticals and pesticides. In the environment, organofluorine molecules are now recognized as an important class of anthropogenic pollutants. Fingerprinting organofluorine compounds via their carbon isotope ratios (13C/12C) is crucial for correlating molecules with their source. Here we apply a 19F nuclear magnetic resonance spectroscopy (NMR) technique to obtain the first position-specific carbon isotope ratios for a diverse set of organofluorine molecules. In contrast to traditional isotope ratio mass spectrometry, the 19F NMR method provides 13C/12C isotope ratios at each carbon position where a C-F bond is present, and does not require fragmentation or combustion to CO2, overcoming challenges posed by the robust C-F covalent bonds. The method was validated with 2,2,2-trifluoroethanol, and applied to analyze heptafluorobutanoic acid, 5-fluorouracil and fipronil. Results reveal distinct intramolecular carbon isotope distributions, enabling differentiation of chemically identical molecules. Notably, the NMR method accurately analyzes carbon isotopes within target molecules despite impurities. Potential applications include the detection of counterfeit products and drugs, and ultimately pollution tracking in the environment.

IN VITRO CYTOTOXIC ACTIVITIES OF PLATINUM(II) COMPLEXES CONTAINING 1H-BENZO[d]IMIDAZOLE AND 1H-1,3-DIAZOLE DERIVATIVES

Objective: This study aimed to synthesize and evaluate the cytotoxic activities of four platinum(II) complexes with 2-substituted or nonsubstituted 1H-benzo[d]imidazole and 1H-1,3-diazole derivatives as carrier ligands (L1-L4), which may have potent cytotoxic activity and low side effects. Material and Method: K1-K4 complexes were synthesized by heating and mixing K2PtCl4 and the appropriate L1-L4. The chemical structures of K1-K4 were elucidated by Infrared and 1H Nuclear Magnetic Resonance spectroscopic methods. In vitro, cytotoxic effects of K1-K4 complexes against prostate (DU-145), endometrial adenocarcinoma (Ishikawa), and breast cancer (MCF-7) cell lines were tested by the MTT method. Result and Discussion: According to the IC50 values of the tested cell lines, K1 and K2 derivatives bearing unsubstituted 1H-benzo[d]imidazole (L1) and 1H-1,3-diazole (L2) were found to be the most effective compounds among these synthesized complexes.

NMR spectroscopic investigations of transition metal complexes in organometallic and bioinorganic chemistry

AbstractThe field of coordination chemistry has evolved to intersect with organic chemistry and biochemistry, giving rise to the disciplines of organometallic and bioinorganic chemistry. Nuclear magnetic resonance (NMR) spectroscopy can be applied for characterizing transition metal complexes, spanning both diamagnetic and paramagnetic complexes prevalent in organometallic compounds and metalloproteins. This review offers a comprehensive overview of a wide variety of characterization techniques, ranging from basic 1H and 13C NMR spectroscopy to advanced methods such as heteronuclear experiments, polarization transfer techniques, relaxometry, and multidimensional NMR spectroscopy. The diverse array of NMR spectroscopic methods outlined here promises to enhance our comprehension of transition metal complexes, facilitating the development of innovative catalysts and therapeutics.

Position-specific carbon stable isotope analysis of glyphosate: isotope fingerprinting of molecules within a mixture.

Glyphosate [N-(phosphonomethyl) glycine] is a widely used herbicide and a molecule of interest in the environmental sciences, due to its global use in agriculture and its potential impact on ecosystems. This study presents the first position-specific carbon isotope (13C/12C) analyses of glyphosates from multiple sources. In contrast to traditional isotope ratio mass spectrometry (IRMS), position-specific analysis provides 13C/12C ratios at individual carbon atom positions within a molecule, rather than an average carbon isotope ratio across a mixture or a specific compound. In this work, glyphosate in commercial herbicides was analyzed with only minimal purification, using a nuclear magnetic resonance (NMR) spectroscopy method that detects 1H nuclei with bonds to either 13C or 12C, and isolates the signals of interest from other signals in the mixture. Results demonstrate that glyphosate from different sources can have significantly different intramolecular 13C/12C distributions, which were found to be spread over a wide range, with δ13C Vienna Peedee Belemnite (VPDB) values of -28.7 to -57.9‰. In each glyphosate, the carbon with a bond to the phosphorus atom was found to be depleted in 13C compared to the carbon at the C2 position, by 4 to 10‰. Aminomethylphosphonic acid (AMPA) was analyzed for method validation; AMPA contains only a single carbon position, so the 13C/12C results provided by the NMR method could be directly compared with traditional isotope ratio mass spectrometry. The glyphosate mixtures were also analyzed by IRMS to obtain their average 13C/12C ratios, for comparison with our position-specific results. This comparison revealed that the IRMS results significantly disguise the intramolecular isotope distribution. Finally, we introduce a 31P NMR method that can provide a position-specific 13C/12C ratio for carbon positions with a C-P chemical bond, and the results obtained by 1H and 31P for C3 carbon agree with one another within their analytical uncertainty. These analytical tools for position-specific carbon isotope analysis permit the isotopic fingerprinting of target molecules within a mixture, with potential applications in a range of fields, including the environmental sciences and chemical forensics.

Update on chiral recognition mechanisms in separation science.

The stereospecific analysis of chiral molecules is an important issue in many scientific fields. In separation sciences, this is achieved via the formation of transient diastereomeric complexes between a chiral selector and the selectand enantiomers driven by molecular interactions including electrostatic, ion-dipole, dipole-dipole, van der Waals or π-π interactions as well as hydrogen or halogen bonds depending on the nature of selector and selectand. Nuclear magnetic resonance spectroscopy and molecular modeling methods are currently the most frequently applied techniques to understand the selector-selectand interactions at a molecular level and to draw conclusions on the chiral separation mechanism. The present short review summarizes some of the recent achievements for the understanding of the chiral recognition of the most important chiral selectors combining separation techniques with molecular modeling and/or spectroscopic techniques dating between 2020 and early 2024. The selectors include polysaccharide derivatives, cyclodextrins, macrocyclic glycopeptides, proteins, donor-acceptor type selectors, ion-exchangers, crown ethers, and molecular micelles. The application of chiral ionic liquids and chiral deep eutectic solvents, as well as further selectors, are also briefly addressed. A compilation of all published literature on chiral selectors has not been attempted.

Design, synthesis, and investigation of biological activities of new triazole derivatives with antifungal effect

Fungal infections pose a significant threat to both morbidity and mortality, especially in immunocompromised patients, notably those with conditions such as AIDS. In the last two decades, the incidence of such fungal infections has increased significantly, especially due to Candida species. The increasing incidence of life-threatening fungal infections has increased the need for new drugs to treat these infections. In this study, 10 novel oxadiazole-triazole hybrid compounds were synthesized. Analysis of the obtained compounds provided by 1H NMR (proton nuclear magnetic resonance), 13C NMR (carbon nuclear magnetic resonance) spectroscopic methods and HRMS (high resolution mass spectrometry) spectrometric method. The inhibition effects of the obtained compounds on the 14α-demethylase enzyme were investigated. Among the synthesized compounds, 4a (contains 4-methyl substituent), 4c (contains 4-cyano substituent), 4d (contains 4-nitro substituent), 4e (contains 4-fluoro substituent), 4 g (contains 4‑bromo substituent) and 4j (contains 3,4-dichloro substituent) coded compounds were useful against C. parapsilosis strain; Compounds 4c, 4f and 4 g also showed significant inhibitory effect against C. albicans strain. Within the scope of the study, the interactions of 14α-demethylase enzyme active site and our compound were elucidated by molecular modeling and molecular dynamics studies. Binding points were determined by docking studies for the selected compounds in enzyme active site. The strongest interaction with 14α-demethylase enzyme active sites was observed in 4c and 4 g coded compounds.

Abstract 5775: Structure and dynamics of the major PDGFR-β oncogene promoter G-quadruplex and insights into its cellular regulation

Abstract Overexpression of the receptor tyrosine kinase PDGFR-β promotes cancer growth and metastasis. PDGFR-β is a validated cancer target but PDGFR-β kinase inhibitors suffer from lack of selectivity and side effects. G-quadruplexes are an exciting class of non-B DNA secondary structures with functional importance. The G-quadruplex formed in the PDGFR-β promoter is a transcription repressor and targetable by small molecules. Therefore, the PDGFR-β promoter G-quadruplex is an attractive molecular target for anticancer drugs. Structural information of the PDGFR-β promoter G-quadruplex is crucial for understanding its cellular function and rational drug design. Herein, we used nuclear magnetic resonance (NMR) spectroscopy and biophysical methods to determine the structure and dynamics of the major G-quadruplex formed in the human PDGFR-β promoter. Unlike canonical G-quadruplexes formed by four runs of three continuous guanines (G), the major PDGFR-β G-quadruplex adopts a novel broken-strand structure where a two-G segment is continued by a non-adjacent guanine. The broken-strand G-quadruplex has a vacancy-G-tetrad (vG4) which is filled-in intramolecularly by a distal guanine. Interestingly, we discovered that the major PDGFR-β G-quadruplex is a novel mixture of two equilibrating broken-strand G-quadruplexes. Both structures adopt overall parallel-stranded folding with all 1-nt chain-reversal loops. However, a different 3’-filled-in guanine is delivered by a lateral loop, which forms structurally similar hairpin with a unique capping G-G base-pair. The formation of the equilibrating broken-strand G-quadruplexes and unique capping structures are both specific to the PDGFR-β promoter sequence. Intriguingly, the observed dynamic equilibrium between the two co-existing structures with different intramolecular fill-in guanines indicates a novel vG4 intermediate, which could be filled-in by cellular guanine metabolites such as cGMP. Therefore, our study provides critical insights into how the dynamics of the major PDGFR-β G-quadruplex lead to vG4 formation and potential regulation of gene transcription by cellular guanine metabolites. The determined molecular structures of the novel broken-strand G-quadruplexes provide a structural basis for rational design of small molecules to specifically target the major PDGFR-β promoter G-quadruplex for cancer therapeutics. Citation Format: Yichen Han, Jonathan Dickerhoff, Danzhou Yang. Structure and dynamics of the major PDGFR-β oncogene promoter G-quadruplex and insights into its cellular regulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5775.

New Strategy for the Synthesis of Some Valuable Chiral 1,3-Diols with High Enantiomeric Purity: New Organocatalyst, Asymmetric Aldol Reaction, and Reduction.

Chiral 1,3-diols are highly valuable molecules used in industries such as pharmaceuticals, cosmetics, and agriculture. Therefore, in this study, a new strategy was developed to synthesize enantiomerically pure (>99% ee) 1,3-diols. New chiral 1,3-diols (5a-5q) with high enantiomeric purity were synthesized from aldol products chiral 1,3-keto alcohols (4a-4q), which are aldol products with different structures. Chiral 1,3-keto alcohols (4a-4q) were synthesized by a new asymmetric aldol method in the first step. This method was developed using a new proline-derived organocatalyst (3g) and Cu(OTf)2 as an additive in DMSO-H2O for the first time. Almost >99% ee was obtained using our developed aldol procedure. In the second step, original chiral diols (5a-5q) of high enantiomeric purity were obtained by asymmetric reduction of chiral keto alcohols with chiral oxazaborolidine reagents. In this way, a two-step asymmetric reaction was developed for chiral 1,3-diol enantiomers with high enantiomeric purity. The structures of all the original chiral compounds obtained were elucidated by infrared and nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis methods. Their enantiomeric excesses were determined by the chiral high-performance liquid chromatography method. Both keto alcohols and their corresponding chiral diols synthesized can be used as chiral starting materials and chiral source materials or intermediates in the synthesis of many biologically active molecules, or they can be used as chiral ligands in asymmetric synthesis, serving as organocatalysts.

Novel biologically active paddlewheel-like palladium thiocyanate complex catalyzed cyanation of alkyl bromide utilizing Q-tube system: A green perspective

A novel paddlewheel-like complex of [Pd(SCN)2(3-Acpy)2], (1) was produced at ambient temperature by adding an aqueous solution of palladium chloride to an aqueous acetonitrile solution of 3-acetylpyridine (3-Acpy) and potassium thiocyanate. Elemental analysis, Fourier-transform infrared (FT-IR), ultraviolet–visible (UV–vis), and nuclear magnetic resonance (NMR) spectroscopic methods were used to characterize complex 1 comprehensively. Single crystal X-ray diffraction was used to analyze the crystal structure of complex 1. The palladium atom is bonded to two 3-Acpy ligands and two thiocyanates groups in trans mode giving square planer geometry in complex 1. The discrete units of paddlewheel-like complex 1 through hydrogen bonding extend to form a 3D supramolecular network structure. The synthesized and characterized new palladium complex 1 was utilized as a precatalyst for the cyanation of alkyl bromide using potassium ferrocyanide as a benign cyanide source reagent. The suggested catalytic test reaction under high-pressure conditions via a Q-tube system in green solvent cyclopentyl methyl ether introduced high yields and a short reaction time. Moreover, the cytotoxic activity of complex 1 was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against HePG-2 of liver cancer and MCF7 of breast cancer cell lines. According to the findings, complex 1 has significant strong activity against the cancer cell lines HePG-2 and MCF-7. Additionally, the luminescence spectra of complex 1 were investigated.

Structure, Physicochemical Properties and Biological Activity of Lipopolysaccharide from the Rhizospheric Bacterium Ochrobactrum quorumnocens T1Kr02, Containing d-Fucose Residues.

Lipopolysaccharides (LPSs) are major components of the outer membranes of Gram-negative bacteria. In this work, the structure of the O-polysaccharide of Ochrobactrum quorumnocens T1Kr02 was identified by nuclear magnetic resonance (NMR), and the physical-chemical properties and biological activity of LPS were also investigated. The NMR analysis showed that the O-polysaccharide has the following structure: →2)-β-d-Fucf-(1→3)-β-d-Fucp-(1→. The structure of the periplasmic glucan coextracted with LPS was established by NMR spectroscopy and chemical methods: →2)-β-d-Glcp-(1→. Non-stoichiometric modifications were identified in both polysaccharides: 50% of d-fucofuranose residues at position 3 were O-acetylated, and 15% of d-Glcp residues at position 6 were linked with succinate. This is the first report of a polysaccharide containing both d-fucopyranose and d-fucofuranose residues. The fatty acid analysis of the LPS showed the prevalence of 3-hydroxytetradecanoic, hexadecenoic, octadecenoic, lactobacillic, and 27-hydroxyoctacosanoic acids. The dynamic light scattering demonstrated that LPS (in an aqueous solution) formed supramolecular particles with a size of 72.2 nm and a zeta-potential of -21.5 mV. The LPS solution (10 mkg/mL) promoted the growth of potato microplants under in vitro conditions. Thus, LPS of O. quorumnocens T1Kr02 can be recommended as a promoter for plants and as a source of biotechnological production of d-fucose.

Preparation and characterization of the aflatoxin B1 purity certified reference material (GBW (E) 100599)

Aflatoxin B1 (AFB1), the most harmful mycotoxin, is widely distributed in many important foodstuffs, especially in peanuts, maize, and oil products. AFB1 certified reference material (CRM), essential for an accurate and reliable detection, is not easily obtained due to the difficulty of preparing high purity candidate. In this study, the high-purity AFB1 candidate was prepared by the preparative high performance liquid chromatography (Pre-HPLC) after high-yields of AFB1 on the maize medium by Aspergillus flavus. The structure of AFB1 was successively characterized by UV, IR, LC-TOF-MS/MS, 1H NMR, and 13C NMR. According to the principle of ISO 17034: 2016 and ISO guide 35: 2017, the purity of the candidate was accurately determined by the mass balance method (MB) and the quantitative nuclear magnetic resonance spectroscopy method (qNMR), while the homogeneity, long-term stability, short-term stability, and uncertainty were systematically studied by the MB method. Under the optimum conditions, the certified purity value for the AFB1 CRM was 99.53 % with an extended uncertainty of 0.56 % (k = 2, 95 % confidence interval), which was also sufficiently homogeneous and stable for 6 months at 4 °C and −20 °C. After approval by State Administration for Market Regulation, a new AFB1 purity CRM (GBW (E) 100599) was finally prepared. This is the first report for the preparation of a reliable AFB1 purity CRM, benefit for enhancing the accuracy, traceability, and comparability of measurements of AFB1 in various foodstuffs, and finally ensure the food quality and safety.

The Isolation of 5-Hydroxymethylfuran Metabolites from the Broth Extract of Fomitopsis meliae (Agaricomycetes)

This study aimed to identify antibacterial compounds from the broth extract of <i>Fomitopsis meliae</i> (MSUCC009). From small-scale fermentation, the broth extract of <i>F. meliae</i> showed antibacterial activity. Therefore, the fermentation of this fungal strain was scaled up and the broth extract was chemically investigated. Purification of the broth extract led to the isolation of two 5-hydroxymethylfuran metabolites, 5-hydroxymethyl-2- furoic acid methyl ester and 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) together with a pyrimidine base, uracil. This is the first isolation report of 5-hydroxymethylfuran derivatives from the genus <i>Fomitopsis</i>. The structures of isolated compounds were elucidated based on nuclear magnetic resonance (NMR) and mass spectrometry (MS) spectroscopic methods, and comparison with previous reports. 5-Hydroxymethyl-2-furancarboxylic acid exhibited antibacterial activity against methicillin-susceptible <i>Staphylococcus aureus</i> with MIC and MBC values of > 0.25 mg/mL. 5-Hydroxymethyl-2-furoic acid methyl ester and 5-hydroxymethyl-2-furancarboxylic acid were also tested against A549 cancer cell lines. These two compounds were inactive in this cytotoxicity assay.

Experimental Studies of Schiff Base (E)-4-methoxy-2-(((2-phenoxyphenyl)imino)methyl) phenol Compound with Various Spectroscopic Methods

Schiff-based compounds, which represent an important class in the field of organic compounds, form the basis of this research article. This research article aims to investigate the synthesized compound (E)-4-methoxy-2-(((2-phenoxyphenyl) imino) methyl) phenol using experimental methods.FT-IR, UV-Vis, 13C and 1H Nuclear Magnetic Resonance (NMR) Spectroscopy and X-ray diffraction methods were used to elucidate the structural properties of the compound synthesized at the end of chemical processes. The structure solution was carried out from the data obtained as a result of X-ray analysis. According to these results, one of the two compounds in the asymmetric cell completed their formation in the enol-imine form and the other in the keto-amine form. This structural situation, which is rare in the literature, was supported and explained by FT-IR, 13C and 1H Nuclear Magnetic Resonance (NMR) spectroscopy studies.According to the results obtained as a result of UV-Vis spectroscopy, the structure revealed that the enol-imine form was dominant. The reasons for this situation were explained.

Study on the affinity sites of cadmium's binding to ligands by thermodynamics and nuclear magnetic resonance spectroscopy.

The affinity sites of cadmium (Cd(II)) when binding to cysteine (Cys) and glutathione (GSH) were studied via thermodynamics and nuclear magnetic resonance (NMR) spectroscopy methods. The results showed that the Cd(II) binding sites of Cys and GSH were -SH (exothermic), -NH2 (endothermic) and -COOH (endothermic). The thermodynamic behaviour of Cd(II) binding to Cys/GSH in boric acid and HEPES buffers differed, with the former being mainly endothermic and the latter mainly exothermic. It could be inferred that, in the boric acid system, the main binding site of Cd(II) with Cys and GSH is changed from -SH in HEPES to -COOH and -NH2 in boric acid. This was confirmed by the results of NMR experiments of Cd(II) with Cys/GSH. 1D 1H-NMR experiments showed that, after the combination of Cd(II) and Cys, the changes in the chemical shifts and peak strengths of protons near the -SH group for the reaction in HEPES were greater than when boric acid buffer was used. Changes in the chemical shift and peak strength of the -NH2 protons due to the binding of Cd(II) to GSH were evident in the boric acid buffer but not in HEPES. The screening of functional monomers is very important in the process of preparation of cadmium ion-imprinted materials. This research provides important theoretical and experimental guidance for the screening of functional monomers.

Methods for Cultivation of Bacteroides thetaiotaomicron and Analysis of Heme Metabolism by Mass Spectrometry and Spectroscopic Approaches.

Traditional studies of cellular metabolism have relied on the use of radioisotopes. These have clear disadvantages associated with safety and waste generation. Furthermore, detection of the labeled species by scintillation counting provides only a quantification of its presence or absence. The use of stable isotopes, by contrast, allows the application of powerful, orthogonal spectroscopic approaches such as nuclear magnetic resonance spectroscopy (NMR) and various mass spectrometric methods. Using stable isotope labeling to study heme metabolism requires integrating methods for (a) generating the heme in labeled forms, (b) cultivating and quantifying the organism of choice in chemically defined media, to which labeled compounds can be added, (c) recovering cellular components and/or spent growth media, and (d) analyzing these materials for the labeled species using spectroscopic and mass spectrometric methods. These methods are summarized here in the context of Bacteroides thetaiotaomicron, a generallynonpathogenic anaerobe and heme auxotroph.