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Nuclear Magnetic Resonance
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Topic review
Updated time: 06 Jul 2021
Submitted by: Ilya Shenderovich
Definition: This review discusses molecular adducts, whose composition allows a symmetric structure. Such adducts are popular model systems, as they are useful for analyzing the effect of structure on the property selected for study since they allow one to reduce the number of parameters. The main objectives of this discussion are to evaluate the influence of the surroundings on the symmetry of these adducts, steric hindrances within the adducts, competition between different noncovalent interactions responsible for stabilizing the adducts, and experimental methods that can be used to study the symmetry at different time scales. This review considers the following central binding units: hydrogen (proton), halogen (anion), metal (cation), water (hydrogen peroxide).
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 12 Jan 2021
Submitted by: Guanshu Liu
Definition: Recently, Chemical Exchange Saturation Transfer (CEST) MRI is emerging as an attractive approach with the capability of directly using low concentration, exchangeable protons-containing agents for generating quantitative MRI contrast. The ability to utilize diamagnetic compounds has been extensively exploited to detect many clinical compounds, such as FDA approved drugs, X-ray/CT contrast agents, nutrients, supplements, and biopolymers. The ability to directly off-label use clinical compounds permits CEST MRI to be rapidly translated to clinical settings.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 07 Jul 2021
Submitted by: Ramon Eritja
Definition: Curaxins and especially the second-generation derivative curaxin CBL0137 have important antitumor activities in multiple cancers such as glioblastoma, melanoma and others. Although most of the authors suggest that their mechanism of action comes from the activation of p53 and inactivation of NF-kB by targeting FACT, there is evidence supporting the involvement of DNA binding in their antitumor activity. In this work, the DNA binding properties of curaxin CBL0137 with model quadruplex DNA oligomers were studied by 1H NMR, CD, fluorescence and molecular modeling. We provided molecular details of the interaction of curaxin with two G-quadruplex structures, the single repeat of human telomere d(TTAGGGT)4 and the c-myc promoter Pu22 sequence.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 25 Jun 2021
Submitted by: Paulo Dani
Definition: One of the most frequently and widely used pyrethroids is deltamethrin, often employed for the control of household insect pests. The presence of three chiral centers translates into eight possible different stereoisomers, with only one of them having insecticidal activity. Active deltamethrin (a-DLM) has an S configuration at the α−benzyl carbon and a 1-R-cis configuration at the cyclopropane ring.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 14 Jul 2021
Submitted by: Dieuwertje Augustijn
Definition: Metabolomics is used to reduce the complexity of plants and to understand the underlying pathways of the plant phenotype. The metabolic profile of plants can be obtained by mass spectrometry or liquid-state NMR. Extraction of metabolites from the sample is necessary for both techniques to obtain the metabolic profile. This extraction step can be eliminated by making use of high-resolution magic angle spinning (HR-MAS) NMR which allows to get metabolic profile directly in intact plant tissues such as intact leaves. An HR-MAS NMR-based metabolomics workflow is thus established that provide a novel platform for obtaining important information of regular metabolic network non-invasively.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 27 Oct 2020
Submitted by: Poul Erik Hansen
Definition: Humic substances are a very important part of our soil. The topic is description of the structure of humic substances using NMR. The NMR part is divided into two parts, liquid and solid state NMR. The assignment of NMR spectra are discussed and the structural elements that can be deduced from the spectral information. Principal Component Analysis is used as a tool to categorize the information. Structural models are discussed.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 22 Apr 2021
Submitted by: Michael Vaeggemose
Definition: MR spectroscopy (MRS) and spectroscopic imaging (MRSI) obtain metabolic information noninvasively from nuclei spins. For in vivo applications, common MR-active nuclei are protons (1H), phosphorus (31P), carbon (13C), sodium (23Na), and xenon (129Xe). The most common are protons due to their high gyromagnetic ratio and natural abundance in the human body. Since most metabolic processes involve carbon, 13C spectroscopy is a valuable method to measure in vivo metabolism noninvasively [1,2,3]. 13C spectra are characterized by a large spectral range (162–185 ppm), narrow line widths, and low sensitivity due to the low gyromagnetic ratio (a quarter as compared to protons) and natural abundance of 1.1% in vivo. However, the sensitivity can be increased with the use of 13C-enriched agents and by hyperpolarization.Hyperpolarized (HP) 13C MRI is a method that magnetizes 13C probes to dramatically increase signal as compared to conventional MRI [3]. Metabolic and functional HP 13C MRI is a promising diagnostic tool for detecting disorders linked to altered metabolism such as cancer, diabetes, and heart diseases [4], increasing sensitivity sufficiently to map metabolic pathways in vivo without the use of ionizing radiation, as in positron emission tomography (PET) imaging. Metabolic imaging using HP 13C compounds has been translated successfully into single-organ examinations in healthy controls and various patient populations.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 08 Jul 2021
Submitted by: Rita Golfieri
Definition: Computed tomography (CT), magnetic resonance imaging (MRI), and 18-fluorideoxyglucose positron emission tomography (18FDG-PET) are historically the most accurate imaging techniques for diagnosing liver metastases. Recently, the combination of diffusion-weighted imaging and hepatospecific contrast media, such as gadoxetic acid in MRI, have been demonstrated to have the highest diagnostic accuracy, sensitivity, and specificity for detecting liver metastases. Various recent meta-analyses have confirmed the diagnostic superiority of this combination (diffusion-weighted imaging and gadoxetic acid-enhanced MRI), especially in terms of per lesion sensitivity, as compared with CT and 18FDG-PET, even for smaller lesions (≤1 cm). However, none of the oncological guidelines have suggested the use of MRI as a first-line technique for liver metastasis detection during the staging process of oncological patients.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 01 Dec 2020
Submitted by: Marcileia Zanatta
Definition: Ionic Liquids (ILs) are organic salts that melt commonly below 100 °C, constituted entirely by charged species. The tunability and versatility of ILs have given rise to several applications at the academic and industrial levels. Here the following topics are highlighted: chemical structure; ILs classification according to the possibility of proton transfer, and the historical generations of ILs.
Entry Collection : Nuclear Magnetic Resonance
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Topic review
Updated time: 12 Jul 2021
Submitted by: Ik-Soo Lee
Definition: Microbial conjugation studies of licochalcones (1–4) and xanthohumol (5) were performed by using the fungi Mucor hiemalis and Absidia coerulea. As a result, one new glucosylated metabolite was produced by M. hiemalis whereas four new and three known sulfated metabolites were obtained by transformation with A. coerulea. Chemical structures of all the metabolites were elucidated on the basis of 1D-, 2D-NMR and mass spectroscopic data analyses. These results could contribute to a better understanding of the metabolic fates of licochalcones and xanthohumol in mammalian systems. Although licochalcone A 4′-sulfate (7) showed less cytotoxic activity against human cancer cell lines compared to its substrate licochalcone A, its activity was fairly retained with the IC50 values in the range of 27.35–43.07 μM.
Entry Collection : Nuclear Magnetic Resonance
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