8,014 results match your criteria amide proton

Conformational analysis and concentration detection of linuron: Spectroscopic NMR and SERS study.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Jul 24;263:120223. Epub 2021 Jul 24.

Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. Electronic address:

Linuron is a commonly used organic herbicide which is used in plant growth control. Due to its potential health concerns, the characterization and monitoring of linuron have been a subject of several studies. In this work, we employed nuclear magnetic resonance (NMR) and Raman spectroscopic techniques supported with the density functional theory (DFT) to investigate the conformational behavior and electronic aspects of linuron. Read More

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Effect of gastric microbiota on quadruple eradication therapy containing bismuth.

World J Gastroenterol 2021 Jul;27(25):3913-3924

Department of Gastroenterology, Peking University Third Hospital, Beijing 100191, China.

Background: () is an important pathogen that can cause a variety of diseases. Yet, full eradication of remains a significant challenge in clinical practice. and other microbial communities have complex interactions in the unique gastric microecological environment. Read More

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Discrimination of enantiomers of amides with two stereogenic centers enabled by chiral bisthiourea derivatives using H NMR spectroscopy.

Org Biomol Chem 2021 Jul 23. Epub 2021 Jul 23.

College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.

Enantiomers of a few new amides containing two stereogenic centers have been derived from d- and l-α-amino acids as guests for chiral recognition by 1H NMR spectroscopy. A variety of chiral amides with two or more stereogenic centers often exist in the products of catalytic asymmetric synthesis, natural products or their total synthetic products, and chiral drugs. It would be a challenging and meaningful work to explore their chiral recognition. Read More

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Structure and function of an Arabidopsis thaliana sulfate transporter.

Nat Commun 2021 07 22;12(1):4455. Epub 2021 Jul 22.

Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA.

Plant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO) and are essential for plant growth; however, our understanding of their structures and functions remains inadequate. Here we present the structure of a SULTR from Arabidopsis thaliana, AtSULTR4;1, in complex with SO at an overall resolution of 2.8 Å. Read More

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Lanthanide complexes of DOTA-nitroxide conjugates for redox imaging: spectroelectrochemistry, CEST, relaxivity, and cytotoxicity.

Dalton Trans 2021 Jul 22. Epub 2021 Jul 22.

Univ. Grenoble Alpes, CNRS, DCM, 38000 Grenoble, France.

The lanthanide(iii) complexes (Gd, Eu, Dy, and Yb) of DOTA tris(amide) and bis(amide) derivatives (L1 and L2) featuring one redox active TEMPO arm were prepared. Ligand L2 harbours an alkyne fragment for further functionalization. The X-ray crystal structure of ligand L2 in complexation with Na+ was solved. Read More

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Rethinking Transition Metal Catalyzed -Carboxyanhydride Polymerization: Polymerization of Pro and AcOPro -Carboxyanhydrides.

J Am Chem Soc 2021 Jul 20. Epub 2021 Jul 20.

Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah 84112, United States.

Polyproline (PP) based polypeptides have broad applications as protein mimics, ordered materials, hydrogels, and surface coatings. However, a lack of rapid and efficient preparatory methods has challenged synthesis of well-defined high molecular weight materials. Here, we report facile and high-yielding methods for preparation and polymerization of Pro and -4-acetoxy-Pro -carboxyanhdrides (NCAs). Read More

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Predicting Treatment Response of Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer Using Amide Proton Transfer MRI Combined With Diffusion-Weighted Imaging.

Front Oncol 2021 1;11:698427. Epub 2021 Jul 1.

Department of Radiology, The Second Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou, China.

Objective: To evaluate amide proton weighted (APTw) MRI combined with diffusion-weighted imaging (DWI) in predicting neoadjuvant chemoradiotherapy (NCRT) response in patients with locally advanced rectal cancer (LARC).

Methods: 53 patients with LARC were enrolled in this retrospective study. MR examination including APTw MRI and DWI was performed before and after NCRT. Read More

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Multi-parametric Z-spectral MRI may have a good performance for glioma stratification in clinical patients.

Eur Radiol 2021 Jul 17. Epub 2021 Jul 17.

Department of Radiology College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.

Objectives: To comprehensively and noninvasively risk-stratify glioma grade, isocitrate dehydrogenase (IDH) genotype, and 1p/19q codeletion status using multi-contrast Z-spectral magnetic resonance imaging (MRI).

Methods: One hundred and thirteen patients with glioma were retrospectively included. Multiple contrasts contributing to Z-spectra, including direct saturation of water (DSW), semi-solid magnetization transfer contrast (MTC), amide proton transfer (APT) effect, aliphatic nuclear Overhauser effect, and the 2-ppm chemical exchange saturation transfer peak ([email protected]), were fitted with five individual Lorentzian functions. Read More

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Capsaicin-Sensitive Vagal Afferent Nerve-Mediated Interoceptive Signals in the Esophagus.

Molecules 2021 Jun 28;26(13). Epub 2021 Jun 28.

Department of Medicine, Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Ave, Baltimore, MD 21205, USA.

Heartburn and non-cardiac chest pain are the predominant symptoms in many esophageal disorders, such as gastroesophageal reflux disease (GERD), non-erosive reflux disease (NERD), functional heartburn and chest pain, and eosinophilic esophagitis (EoE). At present, neuronal mechanisms underlying the process of interoceptive signals in the esophagus are still less clear. Noxious stimuli can activate a subpopulation of primary afferent neurons at their nerve terminals in the esophagus. Read More

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Fully automated analysis combining [F]-FET-PET and multiparametric MRI including DSC perfusion and APTw imaging: a promising tool for objective evaluation of glioma progression.

Eur J Nucl Med Mol Imaging 2021 Jun 25. Epub 2021 Jun 25.

Department of Neuroradiology, TUM School of Medicine, Klinikum Rechts Der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: To evaluate diagnostic accuracy of fully automated analysis of multimodal imaging data using [F]-FET-PET and MRI (including amide proton transfer-weighted (APTw) imaging and dynamic-susceptibility-contrast (DSC) perfusion) in differentiation of tumor progression from treatment-related changes in patients with glioma.

Material And Methods: At suspected tumor progression, MRI and [F]-FET-PET data as part of a retrospective analysis of an observational cohort of 66 patients/74 scans (51 glioblastoma and 23 lower-grade-glioma, 8 patients included at two different time points) were automatically segmented into necrosis, FLAIR-hyperintense, and contrast-enhancing areas using an ensemble of deep learning algorithms. In parallel, previous MR exam was processed in a similar way to subtract preexisting tumor areas and focus on progressive tumor only. Read More

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Near-Ambient-Temperature Dehydrogenative Synthesis of the Amide Bond: Mechanistic Insight and Applications.

ACS Catal 2021 Jun 7;11(12):7383-7393. Epub 2021 Jun 7.

Department of Molecular Chemistry and Materials Science, The Weizmann Institute of Science, Rehovot 76100, Israel.

The current existing methods for the amide bond synthesis acceptorless dehydrogenative coupling of amines and alcohols all require high reaction temperatures for effective catalysis, typically involving reflux in toluene, limiting their potential practical applications. Herein, we report a system for this reaction that proceeds under mild conditions (reflux in diethyl ether, boiling point 34.6 °C) using ruthenium PNNH complexes. Read More

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Enabling Cysteine-Free Native Chemical Ligation at Challenging Junctions with a Ligation Auxiliary Capable of Base Catalysis.

Angew Chem Int Ed Engl 2021 Jun 24. Epub 2021 Jun 24.

Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany.

Ligation auxiliaries are used in chemical protein synthesis to extend the scope of native chemical ligation (NCL) beyond cysteine. However, auxiliary-mediated ligations at sterically demanding junctions have been difficult. Often the thioester intermediate formed in the thiol exchange step of NCL accumulates because the subsequent S→N acyl transfer is extremely slow. Read More

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Hydrogen/Deuterium Exchange and Nuclear Magnetic Resonance Spectroscopy Reveal Dynamic Allostery on Multiple Time Scales in the Serine Protease Thrombin.

Biochemistry 2021 Jun 23. Epub 2021 Jun 23.

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0378, United States.

A deeper understanding of how hydrogen/deuterium exchange mass spectrometry (HDX-MS) reveals allostery is important because HDX-MS can reveal allostery in systems that are not amenable to nuclear magnetic resonance (NMR) spectroscopy. We were able to study thrombin and its complex with thrombomodulin, an allosteric regulator, by both HDX-MS and NMR. In this Perspective, we compare and contrast the results from both experiments and from molecular dynamics simulations. Read More

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Prediction of H3K27M-mutant brainstem glioma by amide proton transfer-weighted imaging and its derived radiomics.

Eur J Nucl Med Mol Imaging 2021 Jun 16. Epub 2021 Jun 16.

Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China.

Purpose: H3K27M-mutant associated brainstem glioma (BSG) carries a very poor prognosis. We aimed to predict H3K27M mutation status by amide proton transfer-weighted (APTw) imaging and radiomic features.

Methods: Eighty-one BSG patients with APTw imaging at 3T MR and known H3K27M status were retrospectively studied. Read More

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Detecting Individual Bond Switching within Amides in a Tunneling Junction.

Nano Lett 2021 06 14;21(12):5409-5414. Epub 2021 Jun 14.

The State Key Laboratory of Refractories and Metallurgy, the Institute of Advanced Materials and Nanotechnology, Wuhan University of Science and Technology, Wuhan, Hubei 430081, China.

Amides are essential in the chemistry of life. Detecting the chemical bond states within amides could unravel the nature of amide stabilization and planarity, which is critical to the structure and reactivity of such molecules. Yet, so far, no work has been reported to detect or measure the bond changes at the single-molecule level within amides. Read More

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Acid-catalyzed proton exchange as a novel approach for relaxivity enhancement in Gd-HPDO3A-like complexes.

Chem Sci 2020 Jul 6;11(30):7829-7835. Epub 2020 Jul 6.

Department of Science and Technological Innovation, Università del Piemonte Orientale Viale T. Michel 11 15121 Alessandria Italy

A current challenge in medical diagnostics is how to obtain high MRI relaxation enhancement using Gd-based contrast agents (CAs) containing the minimum concentration of Gd ions. We report that in GdHPDO3A-like complexes a primary amide group located in close proximity to the coordinated hydroxyl group can provide a strong relaxivity enhancement at slightly acidic pH. A maximum relaxivity of = 9. Read More

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Remote Site-Selective Radical C(sp )-H Monodeuteration of Amides using D O.

Angew Chem Int Ed Engl 2021 Jun 11. Epub 2021 Jun 11.

Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany.

Site-selective incorporation of deuterium into biologically active compounds is of high interest in pharmaceutical industry. We present a mild and environmentally benign metal-free method for the remote selective radical C-H monodeuteration of aliphatic C-H bonds in various amides with inexpensive heavy water (D O) as the deuterium source. The method uses the easily installed N-allylsulfonyl moiety as an N-radical precursor that generates the remote C-radical via site-selective 1,5- or 1,6-hydrogen atom transfer (HAT). Read More

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Generation, Characterization, and Dissociation of Radical Cations Derived from Prolyl-glycyl-glycine.

J Phys Chem B 2021 06 7;125(23):6121-6129. Epub 2021 Jun 7.

Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.

Radical cations of an aliphatic tripeptide prolyl-glycyl-glycine (PGG) and its sequence ions [a + H] and [b - H] have been generated by collision-induced dissociation of the [Cu(Phen)(PGG)] complex, where Phen = 1,10-phenanthroline. Infrared multiple photon dissociation spectroscopy, ion-molecule reaction experiments, and theoretical calculations have been used to investigate the structures of these ions. The unpaired electron in these three radical cations is located at different α-carbons. Read More

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A new method for detecting intramolecular H-bonds of aromatic amides based on the de-shielding effect of carbonyl groups on β-protons.

Phys Chem Chem Phys 2021 Jun;23(23):13284-13291

State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.

Aromatic amide foldamers with highly predictable conformations possess potential for application in the fields of stereoselective recognition, charge transport and catalysis, whose conformations are commonly limited by the intramolecular hydrogen bonding between amide groups and hydrogen-bonding receptors. Herein, on the basis of the de-shielding effect of carbonyl groups on β-protons, we develop a new method for detecting intramolecular hydrogen bonds of aromatic amide compounds. The solvent-related changes in the βH chemical shifts (Δ(δβH)) and NH chemical shifts (Δ(δNH)) of three kinds of amide compounds, which are frequently used as building blocks of aromatic amide foldamers, were recorded in chloroform, nitromethane, acetonitrile and DMSO. Read More

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Formal oxo- and aza-[3 + 2] reactions of α-enaminones and quinones: a double divergent process and the roles of chiral phosphoric acid and molecular sieves.

Chem Sci 2020 Jul 9;11(35):9386-9394. Epub 2020 Jul 9.

Department of Chemistry, University of North Texas Denton TX 76203 USA

A double divergent process has been developed for the reaction of α-enaminones with quinones through facile manipulation of catalyst and additive, leading to structurally completely different products. The two divergent processes, which involve formal aza- and oxo-[3 + 2] cycloaddition reactions, are mediated by chiral phosphoric acid and molecular sieves, respectively. While inclusion of phosphoric acid in the reaction switched the reaction pathway to favor the efficient formation of a wide range of -substituted indoles, addition of 4 Å molecular sieves to the reaction switched the reaction pathway again, leading to enantioselective synthesis of 2,3-dihydrobenzofurans in excellent yields and enantioselectivities under mild conditions. Read More

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Evidence based guidelines for the treatment of Helicobacter pylori infection in Korea 2020.

Korean J Intern Med 2021 07 8;36(4):807-838. Epub 2021 Jun 8.

Division of Healthcare Technology Assessment Research, National Evidence-based Healthcare Collaborating Agency, Seoul, Korea.

Helicobacter pylori infection is one of the most common infectious diseases worldwide. H. pylori is responsible for substantial gastrointestinal morbidity with a high disease burden. Read More

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Facilitated structure verification of the biopharmaceutical peptide exenatide by 2D heteronuclear NMR maps.

J Pharm Biomed Anal 2021 Sep 21;203:114136. Epub 2021 May 21.

Global Biologics, United States Pharmacopeial Convention, 12601 Twinbrook Parkway, Rockville, MD, 20852, United States.

Exenatide is a peptide based anti-diabetic prescription medication. Until now, the literature has lacked a comprehensive atom-specific molecular characterization for this complex large peptide by NMR spectroscopy that can be effortlessly and rapidly utilized for biopharmaceutical structural veracity. Peptide structure verification by NMR is challenging and cumbersome when reliant on traditional proton-based methodology (through-bond and through-space proton connectivity) alone due to increasing complexity, low signal dispersion, and overlap. Read More

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September 2021

Predicting cancer malignancy and proliferation in glioma patients: intra-subject inter-metabolite correlation analyses using MRI and MRSI contrast scans.

Quant Imaging Med Surg 2021 Jun;11(6):2721-2732

Department of Radiology, the University of Illinois at Chicago, Chicago, Illinois, USA.

Background: The non-invasive characterization of glioma metabolites would greatly assist the management of glioma patients in the clinical setting. This study investigated the applicability of intra-subject inter-metabolite correlation analyses for differentiating glioma malignancy and proliferation.

Methods: A total of 17 negative controls (NCs), 39 low-grade gliomas (LGGs) patients, and 25 high-grade gliomas (HGGs) subjects were included in this retrospective study. Read More

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Feasibility evaluation of amide proton transfer-weighted imaging in the parotid glands: a strategy to recognize artifacts and measure APT value.

Quant Imaging Med Surg 2021 Jun;11(6):2279-2291

Department of Stomatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China.

Background: The feasibility and image quality of three-dimensional (3D) amide proton transfer (APT)-weighted (APTw) in parotid tumor lesions have not been well established in previous studies. This study aimed to evaluate the utility of APT imaging in parotid lesions and glands.

Methods: Patients with parotid lesions received 3D turbo spin echo (TSE) APTw on a 3. Read More

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Role of Carbonic Anhydrase in Cerebral Ischemia and Carbonic Anhydrase Inhibitors as Putative Protective Agents.

Int J Mol Sci 2021 May 10;22(9). Epub 2021 May 10.

Department of Neuroscience, Psycology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, 50139 Florence, Italy.

Ischemic stroke is a leading cause of death and disability worldwide. The only pharmacological treatment available to date for cerebral ischemia is tissue plasminogen activator (t-PA) and the search for successful therapeutic strategies still remains a major challenge. The loss of cerebral blood flow leads to reduced oxygen and glucose supply and a subsequent switch to the glycolytic pathway, which leads to tissue acidification. Read More

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Flexibility of Oxidized and Reduced States of the Chloroplast Regulatory Protein CP12 in Isolation and in Cell Extracts.

Biomolecules 2021 May 8;11(5). Epub 2021 May 8.

Aix Marseille Univ, CNRS, BIP, UMR7281, F-13402 Marseille, France.

In the chloroplast, Calvin-Benson-Bassham enzymes are active in the reducing environment created in the light by electrons from the photosystems. In the dark, these enzymes are inhibited, mainly caused by oxidation of key regulatory cysteine residues. CP12 is a small protein that plays a role in this regulation with four cysteine residues that undergo a redox transition. Read More

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ESCASA: Analytical estimation of atomic coordinates from coarse-grained geometry for nuclear-magnetic-resonance-assisted protein structure modeling. I. Backbone and H protons.

J Comput Chem 2021 Aug 28;42(22):1579-1589. Epub 2021 May 28.

Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.

A method for the estimation of coordinates of atoms in proteins from coarse-grained geometry by simple analytical formulas (ESCASA), for use in nuclear-magnetic-resonance (NMR) data-assisted coarse-grained simulations of proteins is proposed. In this paper, the formulas for the backbone H and amide (H ) protons, and the side-chain H protons, given the C -trace, have been derived and parameterized, by using the interproton distances calculated from a set of 140 high-resolution non-homologous protein structures. The mean standard deviation over all types of proton pairs in the set was 0. Read More

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Differentiation of low- and high-grade pediatric gliomas with amide proton transfer imaging: added value beyond quantitative relaxation times.

Eur Radiol 2021 May 28. Epub 2021 May 28.

Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.

Objectives: To evaluate whether amide proton transfer (APT) MRI can be used to characterize gliomas in pediatric patients and whether it provides added value beyond relaxation times.

Methods: In this prospective study, APT imaging and relaxation time mapping were performed in 203 pediatric patients suspected of gliomas from February 2018 to December 2019. The region of interest (ROI) in the tumor was automatically generated with artifact detection and ROI-shrinking algorithms. Read More

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Correlation between amide proton transfer-related signal intensity and diffusion and perfusion magnetic resonance imaging parameters in high-grade glioma.

Sci Rep 2021 May 27;11(1):11223. Epub 2021 May 27.

Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima, 890-8544, Japan.

Amide proton transfer (APT) imaging is a magnetic resonance (MR) molecular imaging technique that is sensitive to mobile proteins and peptides in living tissue. Studies have shown that APT-related signal intensity (APTSI) parallels with the malignancy grade of gliomas, allowing the preoperative assessment of tumor grades. An increased APTSI in malignant gliomas has been attributed to cytosolic proteins and peptides in proliferating tumor cells; however, the exact underlying mechanism is poorly understood. Read More

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Synthesis of Polysubstituted Meta-Halophenols by Anion-Accelerated 2π-Electrocyclic Ring Opening.

Chemistry 2021 Jul 14;27(42):10941-10947. Epub 2021 Jun 14.

Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen Ø, Denmark.

Disrotatory - thermally allowed - 2π-electrocyclic ring-opening reactions require high temperatures to proceed. Herein, we report the first anion-accelerated 2π-electrocyclic ring opening of 6,6-dihalobicyclo[3.1. Read More

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