2D NMR Research Articles

Structurally diverse bufadienolides from the skins of Bufo bufo gargarizans and their cytotoxicity

Natural products, with their extensive chemical diversity, distinctive biological activities, and vast reservoirs, provide a robust foundation for advancing cancer therapeutics. A comprehensive phytochemical investigation of the skins from Bufo bufo gargarizans afforded two new bufadienolide derivatives identified as bufalactamides A and B (1–2), along with six known compounds: argentinogenin (3), desacetylcinobufagin (4), desacetylcinobufaginol (5), cinobufaginol (6), bufalin (7) and gamabufalin (8). The structural elucidation of these compounds was meticulously carried out by analyses of spectroscopic data (1D and 2D NMR, HR-ESIMS), and comparison with the literature data. Plausible biosynthetic pathways for the new compounds were also discussed. Moreover, the cytotoxicity of the compounds was investigated using various cancer cell lines, including lung cancer (A549), colon cancer (HCT-116), liver cancer (SK-Hep-1), and ovarian cancer (SKOV3). Our research findings indicated that compounds 3, and 6–8 exhibit potent cytotoxic activity (IC50 < 2.5 µM). In contrast, compounds 4 and 5 display moderate cytotoxic activity (IC50 < 50 µM) while compounds 1 and 2 show no cytotoxic activity (IC50 > 100 µM). From this data, we conducted a comprehensive analysis of the structure-activity relationships among these compounds.

Structure Characterization of Four New Sesquiterpene Pyridine Alkaloids from Tripterygium wilfordii Hook. f. and Anti-Inflammatory Activity Evaluations

Sesquiterpene pyridine alkaloids (SPAs), as a main class of components in Tripterygium wilfordii Hook. f., possess a variety of bioactivities, such as immunosuppressive, insecticidal, and anti-tumor activities. SPAs can be structurally classed into four subtypes: wilfordate-, evoninate-, iso-wilfordate-, and iso-evoninate types. Our previous study unveiled ten new wilfordate-type SPAs, named wilfordatine A–J, isolated from the roots of Tripterygium wilfordii Hook. f., several of which exhibited significant immunosuppressive activities. As an extension and augmentation of the previous findings, we have now isolated one new iso-wilfordate-type SPA, wilfordatine K (1), alongside three new iso-evoninate-type SPAs, wilfordatines L–N (3–5), and six known analogs. Their structures were characterized by the extensive use of 1D and 2D NMR spectroscopic analysis, as well as HRMS data. Interestingly, compounds 4 and 6 were found to exhibit potent inhibitory effects on the nuclear factor-kappa B (NF-κB) pathway in lipopolysaccharide (LPS)-induced HEK293/NF-κB-Luc cells, with IC50 values of 1.64 μM and 9.05 μM, respectively. Notably, these two compounds had no influence on the cell viability at a concentration of 100 μM. Consequently, they hold significant promise as potential anti-inflammatory candidates for further exploration and development.

Insight into the dynamics of protected and non-protected carbon pools in four soils with different land uses

Abstract Background and aims To provide insight into the patterns of soil organic matter decomposition, changes in the quantity of biopolymers and the correlation between them were followed using 2D correlation spectroscopy (2DCOS) FTIR. Methods Soil organic matter fractions with different vegetation/land use (grass, spruce, oak and arable) were examined in a 1-year laboratory incubation. The non-protected organic matter fraction was calculated in terms of particulate organic matter (POM), the carbon stabilized in aggregates as S + A (sand + aggregates), and the mineral-associated organic matter (MAOM) as the s + c (silt and clay) fraction. Results Forest soils (spruce, oak) exhibited high C and N accumulation in the POM fraction (48, 43% and 29, 22% for spruce and oak, respectively) due to the limited decomposition, caused by low pH and high soil C/N ratio. The 2DCOS analysis revealed that carbohydrate-protein and carbohydrate-lignin correlations could be observed most frequently during incubation. The carbohydrate-protein correlation was negative in all cases, for all fractions and for all vegetation types, which suggests biogeochemical linkage between these biopolymers. The temporal order of the spectral changes was widely varied for the vegetation types and especially for the SOM fractions. Lipid/Lignin → Carbohydrate or Lipid → Lignin/Carboxyl/Protein sequences were found for the protected carbon pools (S + A and s + c), possibly because of the readily available abundant N compounds present in MAOM. Conclusion Although lipids and lignin are considered as chemically stable materials that commonly remain constant during decomposition, these compounds were found to be very susceptible in all the fractions.

P-Terphenyl and Orsellinic Acid Derivatives from the European Polyporales Terana coerulea and Sparassis brevipes.

Investigation of the secondary metabolites of the solid-state rice cultures from the European basidiomycetes Terana coerulea and Sparassis brevipes afforded three previously undescribed secondary metabolites identified as two p-terphenyl derivatives (1 and 2) and one orsellinic acid congener (3) in addition to another known, isoeverninic acid (4). Chemical structures of the isolated compounds were elucidated through comprehensive 1D and 2D NMR spectroscopic analyses, coupled with HR-MS and other spectral methods. The isolated compounds were assessed for their cytotoxic and antimicrobial activities. Compound 1 revealed weak antimicrobial properties, whereas the inseparable mixture of 3 and 4 featured moderate cytotoxic and antimicrobial effects.

Evidence for Nanostructures of at Least 20 nm in a Phosphonium Ionic Liquid at Room Temperature Using Fluorescence Correlation Spectroscopy.

Fluorescence correlation spectroscopy (FCS) measurements are performed on the ionic liquid (IL), tetradecyl(trihexyl) phosphonium chloride, [P66614+][Cl-], using fluorescent probes of varying sizes: ATTO 532, ∼2 nm; and 20- and 40 nm fluorescent beads. The fluorescence correlation function, G(t), is analyzed in terms of a distribution of diffusion coefficients using a maximum entropy method (MEM). For ATTO 532 and the 20 nm beads, the fit to G(t) yields two well-defined distributions; for the 40 nm beads, however, only one is obtained. These results are consistent with the existence of two nanodomains whose size is greater than or equal to 20 nm and less than 40 nm. The origin of such nanodomains is attributed to a liquid-liquid phase transition. Other groups have observed liquid-liquid phase transitions experimentally in a number of systems, including [P66614+][Cl-]. We suggest that because large regions (i.e., greater than 1-2 nm) resulting from the liquid-liquid phase transition would be expected to have different properties, such as viscosity, and because their presence would necessarily increase the number of interfaces in the IL, these regions may provide an explanation for the exceptional behavior of ILs in various separation systems.

Three new spirocyclic terpenoids from Euphorbia amygdaloides exhibit cytotoxicity against cancerous cell lines through early and late apoptosis

Bioassay-guided fractionation led to the isolation of three new spirocyclic terpenoid compounds from Euphorbia amygdaloides L., named Zagrosin I–III. Their structures were identified by 1D and 2D NMR (1H NMR, 13C NMR, DEPT 135, HMBC, and HSQC-TOCSY) and LC-MS-MS spectrometry. The cytotoxicity of the isolated spirocyclic terpenoids (Zagrosin I-III) was assessed against human breast cancer (MCF-7), human fibrosarcoma (HT1080), and normal human foreskin fibroblast cells with MTT assays (24, 48, and 72 h treatments). The FITC-Annexin V apoptosis flow cytometry assays and cell cycle analysis were performed for Zagrosin I–III.These isolated compounds were identified as: (9)-8a-((benzoyloxy)methyl)-2-methoxy-4,9-dimethyltetrahydro-4H,5H-2,4a-methanobenzo[d] [1,3] dioxine-4-carboxylate (Zagrosin I), ((9)-4-hydroxy-2-methoxy-4,9-dimethyltetrahydro-4H,8aH-2,4a-methanobenzo[d] [1,3] dioxin-8a-yl) methyl benzoate (Zagrosin II), and (9)-2-methoxy-4,9-dimethyl-8a-(phenoxy methyl) tetrahydro-4H,5H-2,4a-methanobenzo[d][1,3]dioxin-4-yl 4-methylpentanoate (Zagrosin III).The IC50 of Zagrosin I on 48-h-treated MCF-7 was calculated as 1.5 μg/mL. Zagrosin II and III exhibited cytotoxicity on 48-h-treated MCF-7 with IC50s of 14.04 and 12.50 μg/mL, respectively. The IC50 of Zagrosin I on human fibrosarcoma (HT1080) was 115.5 μg/mL, Zagrosin III, 16.81 μg/mL (48 h treatment), and Zagrosin II, 142.7 μg/mL (72 h treatment). Zagrosin I-III exhibited significant cytotoxicity against the MCF-7 cell line and human fibrosarcoma (HT1080), with the mechanism of early and late apoptosis affecting cells mostly in G0/G1 fallowed by S and G2 phases. MCF-7 had a higher rate of phosphatidyl serine exposure on the cell membrane than two other studied cells. The cytotoxicity on normal human foreskin fibroblasts was low. Zagrosin I-III can be considered an effective chemical backbone for anticancer drug development.Abbreviations: 2D NMR: Two-Dimensional Nuclear Magnetic Resonance Spectroscopy; API: Atmospheric Pressure Ionization; DEPT: Distortionless Enhancement by Polarization Transfer; ELISA: Enzyme-Linked Immunosorbent assay; ERK: Extracellular signal-regulated kinase; ESI: Electrospray ionization; FBS: Fetal Bovine Serum; FITC: Fluorescein isothiocyante; fr: fraction; HMBC: Heteronuclear Multiple Bond Correlation; HPLC: High-Performance Liquid Chromatography; HSQC: Heteronuclear Single Quantum Coherence; HT1080: Human fibrosarcoma cell line; IC50: Half-maximal inhibitory concentration; MCF-7: Human breast cancer cell line; MHz: Megahertz; MTT: 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide; NMR: Nuclear Magnetic Resonance; PBS: Phosphate Buffered Saline; PI: Propidium Iodide; ppm: Part Per Million; Rf: Retention Factor; TLC: Thin-layer chromatography; TOCSY: Total Correlation Spectroscopy; VLC: Vacuum Liquid Chromatography.

Capsular polysaccharide structure of Acinetobacter baumannii K58 from clinical isolate MRSN31468

Capsular polysaccharides (CPS) of Acinetobacter baumannii is a virulence factor with diverse structures. CPS are produced by the CPS biosynthesis gene cluster in their K locus (KL). However, CPS variations may occur due to insertion of additional genes from external sources, e.g., prophages. Recently, the CPS structure from a clinical isolate, BAL062 which includes KL58 locus, was found to have a pseudaminic acid isomer (8ePse5NAc7NAc) as a result of prophage inserted epaA/epaB genes. Here, we report a CPS structure produced by A. baumannii strain MRSN31468 which also belongs to a KL58 type. The K58 CPS structure was determined by 1D and 2D NMR analysis of the oligosaccharides derived from the CPS by a phage depolymerase, and supported by the sugar composition analysis. The K58 CPS structure has the following tetra saccharide repeating unit: [Display omitted] The K58 CPS differs from the CPS from BAL062 only by replacing 8-epimerized β-8ePse5NAc7NAc with β-Pse5NAc7NAc.

Improved 2D hydride detection for NMR-chemosensing via p‐H2 Hyperpolarization

2D NMR zero-quantum spectroscopy offers a robust and convenient way to resolve hydride resonances in non-hydrogenative ParaHydrogen Induced Polarization experiments. This approach has been recently applied to the detection and quantification of dilute components in biofluids and natural extracts. For certain classes of analytes, however, modulation of the zero-quantum coherence occurs at several kiloHertz frequency, which determines long measurement times for attaining the desired resolution in the indirect dimension. Here, we propose an alternative 2D approach to measure high-resolution NMR spectra that affords enhanced sensitivity and reduced experimental time for optimal sample throughput.

Essential magnetosome proteins MamI and MamL from magnetotactic bacteria interact in mammalian cells

To detect cellular activities deep within the body using magnetic resonance platforms, magnetosomes are the ideal model of genetically-encoded nanoparticles. These membrane-bound iron biominerals produced by magnetotactic bacteria are highly regulated by approximately 30 genes; however, the number of magnetosome genes that are essential and/or constitute the root structure upon which biominerals form is largely undefined. To examine the possibility that key magnetosome genes may interact in a foreign environment, we expressed mamI and mamL as fluorescent fusion proteins in mammalian cells. Localization and potential protein-protein interaction(s) were investigated using confocal microscopy and fluorescence correlation spectroscopy (FCS). Enhanced green fluorescent protein (EGFP)-MamI and the red fluorescent Tomato-MamL displayed distinct intracellular localization, with net-like and punctate fluorescence, respectively. Remarkably, co-expression revealed co-localization of both fluorescent fusion proteins in the same punctate pattern. An interaction between MamI and MamL was confirmed by co-immunoprecipitation. In addition, changes in EGFP-MamI distribution were accompanied by acquisition of intracellular mobility which all Tomato-MamL structures displayed. Analysis of extracts from these cells by FCS was consistent with an interaction between fluorescent fusion proteins, including an increase in particle radius. Co-localization and interaction of MamI and MamL demonstrate that select magnetosome proteins may associate in mammalian cells.

Enhancing the accuracy of blood-glucose tests by upgrading FTIR with multiple-reflections, quantum cascade laser, two-dimensional correlation spectroscopy and machine learning

The accuracy of screening diabetes from non-diabetes is drastically enhanced by strategically upgrading the bench-marking infrared spectroscopy technique for non-invasive tests of blood-glucose, both with state-of-the-art instrumentation-retrofits and with intelligent spectral-datamining tools. First, the signal-to-noise performance of FTIR in measuring the spectral features of a glucose solution containing bovine serum albumin is improved by 2–3 times with the common single-pass attenuated total-reflection setup replaced by a multi-passes-reflections setup. Second, replacing the ordinary infrared lamp with a quantum cascade laser further improves the signal-to-noise by 3 times. The performance of the upgraded spectrometer in screening hyperglycemia is gauged by the accuracy of such screens derived from 100 repetitive spectral-measurements per glucose concentration, for 24 glucose concentrations spanning the range of 70–300 mg/dL, a range which covers the blood-glucose contents of all non-diabetic and diabetic human-subjects. Third, intelligent datamining methods are exploited to implement decision trees for screening hyperglycemia. Their decisions are mapped into a confusion matrix and the matrix-elements are used to calculate the accuracy merits of each method. Evidently, the accuracy of the multi-passes-FTIR with the standard principal-components datamining method is 80 %. The adoptions of the quantum cascade laser and two-dimensional correlation spectroscopy datamining technique raises this to 96.3 %. Finally, a novel machine learning method, which comprises three different decision-tree tools to generate trial screening decisions and a “majority-voting” datamining tool to reach a final screening decision, yields the best accuracy of 98.8 % ever reported in the literature.

A New 19(10→9)Abeo-Euphane Triterpenoid with other Terpenoid Components from Trichilia dregeana Leaves and their NO Production Inhibitory Activities in LPS-Stimulated RAW264.7 Macrophages.

Trichilia dregeana Sond. (Meliaceae) is a plant used in traditional medicine to treat wounds. The anti-inflammatory potential of the ethyl acetate leaf extract and the presence of euphane-type triterpenes in this extract have recently been reported by our group. Further investigation of the remaining subfractions of the ethyl acetate fraction afforded a new 19(10→9)abeo-euphane-type triterpenoid (1), along with six known terpenoids (2-7). The structure of the new compound was elucidated by analyses of the HR-ESI-MS, 1D and 2D NMR data and by comparison with previously reported data. We investigated the ability of the compounds to modulate the production of nitric oxide (NO) in LPS-stimulated RAW264.7 macrophages. The known compounds 3 and 6 exhibited moderate (IC50 72.06 μM) and mild (IC50 98.84 μM) inhibitory activities, respectively, without cytotoxic effects on the cells. These results, in conjunction with our previous findings, emphasize the significant role of terpenoid components in the anti-inflammatory efficacy of T. dregeana leaves and indicate that the rare 3,10-epoxy-19(10→9)abeo-euphane triterpenoids could serve as a chemotaxonomic marker for T. dregeana.

Simple Parameters and Data Processing for Better Signal-to-Noise and Temporal Resolution in In Situ 1D NMR Reaction Monitoring.

In situ 1D NMR spectroscopic reaction monitoring allows detailed investigation of chemical kinetics and mechanism. Concentration versus time data are derived from a time series of NMR spectra. Each spectrum in the series is obtained by Fourier transform of the corresponding FID. When the spectrometer outputs FIDs recorded from multiple scans, the spectra benefit from an increase in signal-to-noise (S/N). However, this reduces the number of FIDs and, thus, kinetic data points. We report a simple alternative in which the same number of scans is acquired by the spectrometer, but each scan is saved independently. Signal averaging is then conducted by postacquisition processing. This leads to an increase in both the S/N and the number of kinetic data points and can avoid "overaveraging" effects. The entire series of single-scan FIDs spanning the reaction lifetime can be summed to yield a "total reaction spectrum" in which intermediates can be identified. The method can be applied in coherence with phase cycling to minimize spectral distortion during solvent signal suppression. Overall, the approach simplifies the preacquisition parameters to the estimation of the reaction duration and T1max and then the selection of the pulse angle, θ, and scan repetition time, τR, without the need to set the signal averaging before the experiment.

Doubly Homologated Tyrosine-Containing Peptides from the Cyanobacterium Microcystis aeruginosa NIES-4285 and Their Biosynthesis.

Chemical investigation of the cyanobacterium Microcystis aeruginosa NIES-4285 led to the isolation of six new natural products, microginins 705 (1), 719 (2), 733A (3), 733B (4), and 733C (5), and anabaenopeptin 885 (7), and three known compounds, anabaenopeptins 871 (6), B (8), and F (9). Planar structures and absolute configurations for 1-7 were determined by 2D NMR, HRMS, and Marfey's analyses. Microginin 733C (5), and anabaenopeptins 871 (6) and 885 (7) contained a unique residue of 2-amino-5-(4-hydroxyphenyl)pentanoic acid (Ahppa): doubly homologated tyrosine (di-hTyr). The biosynthetic origin of this nonproteinogenic amino acid di-hTyr was investigated, and it was found that MaHphABCDE are involved in the production of di-hTyr. In addition, biochemical characterization of aminotransferase MaHphE showed that it is a promiscuous enzyme. This result expanded the biocatalytic toolbox for amino acid homologation.

Study the effect of Convolvulus pilosellifolius Desr. as antialzheimer and identification of its active compounds

The phenolic pattern of the plant using chromatographic and spectroscopic methods. Three flavonoid and two phenolic compounds were isolated for first time from the alcoholic plant extract which identified as; Quercetin-3’-galactoside, Quercetin-7-glucoside, Quercetin −3-glucoside and two phenolic compounds identified as Methyl-trans-dihydroxy cinnamic acid and Methyl-cis-dihydroxy cinnamic acid, they were isolated and purified using classical and modern chromatographic methods; (PC, TLC, CC and HPLC); identified by Rf, UV,1H NMR,13C NMR and 2D NMR (HMQC) spectroscopy. The activity of total alcoholic extract of Convolvulus pilosellifolius as antialzheimer was investigated concerning its activity as acetylcholine esterase inhibitor. The recorded IC50 was 0.391 and 0.131 µg/mL for the extract and donepezil respectively. The activity of isolated compounds as acetylcholine esterase inhibitor were evaluated by Autodock Vina software to perform the docking protocol. This revealed that the most active compound was Quercetin-3Ì· galactoside.

In-situ FTIR spectroscopy of epoxy resin degradation: kinetics and mechanisms

We report on an in situ FTIR study of the thermo-oxidative degradation of a flexible epoxy resin. Different and complementary approaches to the analysis of the spectral data were employed, providing a detailed description of the process in terms of kinetics and mechanisms. A preliminary normal coordinate analysis, based on the DFT method, allowed for a reliable interpretation of the observed spectrum, increasing the amount of available structural information. Two-dimensional correlation spectroscopy provided details on the evolution of the reacting network structure. The relative stability of the various functional groups was ranked, and the most likely sites of initiation were identified. Oxygen fixation on the network chains produced amide and ketone groups, with the latter developing at a higher rate. The kinetic profiles of various functional groups were accurately simulated by a first-order, biexponential model, which allowed a quantitative comparison among their relative stabilities. The spectroscopic analysis allowed us to propose likely mechanisms and to identify those that occur preferentially.

Wheat Flour Discrimination Using Two-Dimensional Correlation Spectroscopy and Deep Learning.

The continuous evolution of deep learning has garnered significant attention in spectroscopy. This study focuses on identifying wheat flour, presenting a more efficient and accurate method by combining two-dimensional correlation spectroscopy (2D-COS) and deep learning techniques. A data set of 316 near-infrared (NIR) spectral samples of four types of wheat flour was collected. By applying three disparate 2D-COS techniques, i.e., synchronous, asynchronous, and integrated, we crafted 948 2D-COS images. These images, obtained by transforming the original one-dimensional spectra into 2D representations, offer richer information for deep learning analysis. The study introduced an 18-layer residual network incorporating a convolutional attention mechanism, specifically tailored for the 2D-COS analysis of wheat flour, aimed at enhancing the model's discriminative capabilities by refining the residual neural network's structure. Achieving an unprecedented recognition accuracy of 100% through methodical optimization and rigorous training on the synchronous 2D-COS data set of wheat flour, the proposed model is a testament to the efficacy of deep learning in spectroscopic analysis. To further exhibit the confluence of 2D-COS with deep learning, t-distributed stochastic neighbor embedding was employed to visualize the distinctive 2D-COS features within the deep learning architecture. Additionally, the model's performance was juxtaposed with prevailing NIR spectral recognition methods, including random forest, gradient boosting decision tree, and artificial neural network. This comparison cemented the proposed approach's superiority in wheat flour categorization. The findings of this study not only introduce a novel and efficient solution for wheat flour quality analysis but also underscore the significant potential of deep learning techniques in spectroscopy applications.

Synthesis and Docking Studies of Novel Spiro[5,8-methanoquinazoline-2,3′-indoline]-2′,4-dione Derivatives

In this study, a set of spiro[5,8-methanoquinazoline-2,3′-indoline]-2′,4-dione derivatives 3a–p were synthesized starting from unsubstituted and N-methyl-substituted diendo- and diexo-2-aminonorbornene carboxamides, as well as various substituted isatins. The typical method involves a condensation reaction of alicyclic aminocarboxamide and isatin in the presence of a catalyst, using a solvent and an acceptable temperature. We developed a cost-effective and ecologically benign high-speed ball milling (HSBM), microwave irradiation (MW), and continuous flow (CF) technique to synthesize spiroquinazolinone molecule 3a. The structures of the synthesized compounds 3a–p were determined using 1D and 2D NMR spectroscopies. Furthermore, docking studies and absorption, distribution, metabolism, and toxicity (ADMET) predictions were used in this work. In agreement with the corresponding features found in the case of both the SARS-CoV-2 main protease (RCSB Protein Data Bank: 6LU7) and human mast cell tryptase (RCSB Protein Data Bank: 2ZA5) based on the estimated total energy and binding affinity, H bonds, and hydrophobicity in silico, compound 3d among our 3a–g, 3i–k, and 3m derivatives was found to be our top-rated compound.

4hJCHOCH Spin Coupling in a Lewisx Trisaccharide as Evidence of Inter-Residue C-H···O Hydrogen Bonding in Aqueous Solution.

Prior studies of the solution conformation of the Lewisx (Lex) trisaccharide, αFuc-(1→3)[βGal-(1→4)]-βGlcNAc, suggest that nonclassical inter-residue C-H···O hydrogen bonding in aqueous solution contributes to the stabilization of its 3D structure and affects its biological properties. Experimental evidence for this hydrogen bond in aqueous solution has been reported in the form of a 4hJCHOCH NMR spin-coupling constant between C5'Fuc and H1″Gal measured by 2D NMR methods in unlabeled samples. A methyl glycoside of Lex (MeβLex) was prepared containing selective 13C-labeling at C5'Fuc, and the H1″Gal signal was examined in high-field 1H NMR spectra for evidence of splitting or line-broadening caused by the 13C at C5'Fuc. High-resolution 1H NMR spectra obtained at high field and at different temperatures using different FID processing parameters showed no resolved splitting of the H1″Gal signal or evidence of line-broadening. Spectral simulation showed that this splitting and/or line-broadening would be observable if the reported J-value (∼1.1 Hz) is correct. DFT calculations on MeβLex and a carbon analog (O5″Gal replaced by a CH2 group) gave very small and nearly identical calculated 4hJC5',H1″ values, suggesting that the coupling is essentially zero. DFT calculations also showed that an alternate inter-residue 3hJH5',H1″ is small. Based on NMR analyses and DFT calculations, we found that 4hJC5',H1″ in MeβLex has an upper limit of ∼0.4 Hz and that the value could be lower, possibly zero, calling into question its value as experimental proof of persistent nonclassical hydrogen bonding in aqueous solutions of MeβLex and related structures.

Wavelet and time-based cerebral autoregulation analysis using diffuse correlation spectroscopy on adults undergoing extracorporeal membrane oxygenation therapy.

Adult patients who have suffered acute cardiac or pulmonary failure are increasingly being treated using extracorporeal membrane oxygenation (ECMO), a cardiopulmonary bypass technique. While ECMO has improved the long-term outcomes of these patients, neurological injuries can occur from underlying illness or ECMO itself. Cerebral autoregulation (CA) allows the brain to maintain steady perfusion during changes in systemic blood pressure. Dysfunctional CA is a marker of acute brain injury and can worsen neurologic damage. Monitoring CA using invasive modalities can be risky in ECMO patients due to the necessity of anticoagulation therapy. Diffuse correlation spectroscopy (DCS) measures cerebral blood flow continuously, noninvasively, at the bedside, and can monitor CA. In this study, we compare DCS-based markers of CA in veno-arterial ECMO patients with and without acute brain injury. Adults undergoing ECMO were prospectively enrolled at a single tertiary hospital and underwent DCS and arterial blood pressure monitoring during ECMO. Neurologic injuries were identified using brain computerized tomography (CT) scans obtained in all patients. CA was calculated over a twenty-minute window via wavelet coherence analysis (WCA) over 0.05 Hz to 0.1 Hz and a Pearson correlation (DCSx) between cerebral blood flow measured by DCS and mean arterial pressure. Eleven ECMO patients who received CT neuroimaging were recruited. 5 (45%) patients were found to have neurologic injury. CA indices WCOH, the area under the curve of the WCA, were significantly higher for patients with neurological injuries compared to those without neurological injuries (right hemisphere p = 0.041, left hemisphere p = 0.041). %DCSx, percentage of time DCSx was above a threshold 0.4, were not significantly higher (right hemisphere p = 0.268, left hemisphere p = 0.073). DCS can be used to detect differences in CA for ECMO patients with neurological injuries compared to uninjured patients using WCA.

The oligonucleotides containing N7-regioisomer of guanosine. Influence on thermodynamic properties and structure of RNA duplexes.

During chemical synthesis of the purine riboside, the N7-regioisomer is kinetically formed whereas the N9-regioisomer is a thermodynamically formed product. We have studied the effect of substituting the N9-regioisomer of guanosine with its N7-regioisomer (N7-guanosine, 7G) at a central position of several RNA duplexes. We found that this single substitution by 7G severely diminished their thermodynamic stabilities when 7G paired with C and U, but remarkably, led to a significant amount of stabilization in most of the duplexes when forming mismatches with G and A. The extent of stabilization was observed to be dependent on the sequence and orientation of neighboring base pairs of N7-guanosine. 1D and 2D NMR studies on the duplexes along with extensive molecular dynamics simulations revealed the conformational differences occurring due to substitution of G by 7G and it was observed that the thermodynamic results were largely explainable by considering the formation of stable non-canonical hydrogen bonding interactions, although other interactions such as stacking and electrostatic interactions could also play a role. These observations can have important applications in the design of RNA-based disease diagnostics and therapeutics.