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Amide proton transfer

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https://www.readbyqxmd.com/read/29424463/spin-lock-imaging-of-early-tissue-ph-changes-in-ischemic-rat-brain
#1
Zhongliang Zu, Aqeela Afzal, Hua Li, Jingping Xie, John C Gore
We have previously reported that the dispersion of spin-lattice relaxation rates in the rotating frame (R1ρ ) of tissue water protons at high field can be dominated by chemical exchange contributions. Ischemia in brain causes changes in tissue pH, which in turn may affect proton exchange rates. Amide proton transfer (APT, a form of chemical exchange saturation transfer) has been shown to be sensitive to chemical exchange rates and able to detect pH changes non-invasively following ischemic stroke. However, the specificity of APT to pH changes is decreased because of the influence of several other factors that affect magnetization transfer...
February 9, 2018: NMR in Biomedicine
https://www.readbyqxmd.com/read/29412653/inner-sphere-and-outer-sphere-water-interactions-in-co-ii-paracest-agents
#2
Samira M Abozeid, Eric M Snyder, Timothy Y Tittiris, Charles M Steuerwald, Alexander Y Nazarenko, Janet R Morrow
High-spin Co(II) complexes are promising for development as paraCEST agents (paraCEST = paramagnetic chemical exchange saturation transfer) for magnetic resonance imaging applications. The first examples of Co(II) paraCEST agents with bound water ligands are presented here. Four Co(II) macrocyclic complexes based on 1,4,7-triazacyclononane and containing either pendent alcohol or pendent amide groups were prepared. Two of the macrocycles encapsulate the Co(II) and contain no water ligands as shown by X-ray crystallographic studies, and two complexes have macrocycles with only five ligand donor groups to leave an open coordination site for bound water...
February 7, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29392952/effect-of-hydrogen-bonding-and-partial-deprotonation-on-the-oxidation-of-peptides
#3
Bun Chan, Christopher J Easton, Leo Radom
In a recent computational study, we found that hydrogen bonding/partial deprotonation facilitates subsequent electron transfer from amides to HO•. We have now analyzed these and related reactions with a glycine derivative as a model peptide, investigating not only reaction energies but also barriers for the individual steps. We find that partial deprotonation not only assists subsequent electron transfer (a sequential proton-loss electron-transfer (SPLET)-type reaction pathway) but also promotes sequential hydrogen-atom transfer (HAT, in a sequential proton-loss hydrogen-atom-transfer (SPLHAT)-type process), both being potential alternatives to direct HAT as routes for peptide oxidation...
February 2, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29385345/thermodynamic-acidity-studies-of-6-6-dihydroxy-2-2-bipyridine-a-combined-experimental-and-computational-approach
#4
Dalton B Burks, Monica Vasiliu, David A Dixon, Elizabeth T Papish
The organic ligand 6,6'-dihydroxy-2,2'-bipyridine (6,6'-dhbp) is frequently used to bind transition metals in order to form catalysts for many organic and inorganic transformations. 6,6'-dhbp exists in two tautomeric forms, the pyridinol tautomer and the amide (lactam) tautomer with each tautomer having two rotational conformers: cis or trans. Only the cis-pyridinol tautomer has the proper configuration to bind transition metals. The pendant OH (or O- groups when deprotonated) in 6,6'-dhbp typically do not bind the metal when forming the metal catalyst but can facilitate the proton transfer steps in the catalysis process...
January 31, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29326984/using-parahydrogen-to-hyperpolarize-amines-amides-carboxylic-acids-alcohols-phosphates-and-carbonates
#5
Wissam Iali, Peter J Rayner, Simon B Duckett
Hyperpolarization turns weak nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) responses into strong signals, so normally impractical measurements are possible. We use parahydrogen to rapidly hyperpolarize appropriate 1H, 13C, 15N, and 31P responses of analytes (such as NH3) and important amines (such as phenylethylamine), amides (such as acetamide, urea, and methacrylamide), alcohols spanning methanol through octanol and glucose, the sodium salts of carboxylic acids (such as acetic acid and pyruvic acid), sodium phosphate, disodium adenosine 5'-triphosphate, and sodium hydrogen carbonate...
January 2018: Science Advances
https://www.readbyqxmd.com/read/29313159/improved-differentiation-of-low-grade-and-high-grade-gliomas-and-detection-of-tumor-proliferation-using-apt-contrast-fitted-from-z-spectrum
#6
Jiaxuan Zhang, Wenzhen Zhu, Rongwen Tain, Xiaohong Joe Zhou, Kejia Cai
PURPOSE: The purpose of the study is to demonstrate the value of quantitative amide proton transfer (APT) imaging for differentiating glioma grades and detecting tumor proliferation. PROCEDURES: This study included 32 subjects with 16 low-grade gliomas (LGG) and 16 high-grade gliomas (HGG) confirmed by histopathology. Chemical exchange saturation transfer (CEST) magnetic resonance imaging with APT weighting was performed on a 3 T scanner. After B0 correction, Z-spectra were fitted with Lorentzian functions corresponding to the upfield semi-solid magnetization transfer and nuclear overhauser enhancement (MT&NOE) effect, the direct saturation (DS) effect, and the downfield APT effect centered at around - 1...
January 8, 2018: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/29301781/addition-of-amide-proton-transfer-imaging-to-fdg-pet-ct-improves-diagnostic-accuracy-in-glioma-grading-a-preliminary-study-using-the-continuous-net-reclassification-analysis
#7
A Sakata, T Okada, Y Yamamoto, Y Fushimi, T Dodo, Y Arakawa, Y Mineharu, B Schmitt, S Miyamoto, K Togashi
BACKGROUND AND PURPOSE: Amide proton transfer imaging has been successfully applied to brain tumors, however, the relationships between amide proton transfer and other quantitative imaging values have yet to be investigated. The aim was to examine the additive value of amide proton transfer imaging alongside [18F] FDG-PET and DWI for preoperative grading of gliomas. MATERIALS AND METHODS: Forty-nine patients with newly diagnosed gliomas were included in this retrospective study...
January 4, 2018: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/29234914/discriminating-mgmt-promoter-methylation-status-in-patients-with-glioblastoma-employing-amide-proton-transfer-weighted-mri-metrics
#8
Shanshan Jiang, Qihong Rui, Yu Wang, Hye-Young Heo, Tianyu Zou, Hao Yu, Yi Zhang, Xianlong Wang, Yongxing Du, Xinrui Wen, Fangyao Chen, Jihong Wang, Charles G Eberhart, Jinyuan Zhou, Zhibo Wen
OBJECTIVES: To explore the feasibility of using amide proton transfer-weighted (APTw) MRI metrics as surrogate biomarkers to identify the O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status in glioblastoma (GBM). METHODS: Eighteen newly diagnosed GBM patients, who were previously scanned at 3T and had a confirmed MGMT methylation status, were retrospectively analysed. For each case, a histogram analysis in the tumour mass was performed to evaluate several quantitative APTw MRI metrics...
December 12, 2017: European Radiology
https://www.readbyqxmd.com/read/29193448/increased-cest-specificity-for-amide-and-fast-exchanging-amine-protons-using-exchange-dependent-relaxation-rate
#9
Xiao-Yong Zhang, Feng Wang, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
Chemical exchange saturation transfer (CEST) imaging of amides at 3.5 ppm and fast-exchanging amines at 3 ppm provides a unique means to enhance the sensitivity of detection of, for example, proteins/peptides and neurotransmitters, respectively, and hence can provide important information on molecular composition. However, despite the high sensitivity relative to conventional magnetic resonance spectroscopy (MRS), in practice, CEST often has relatively poor specificity. For example, CEST signals are typically influenced by several confounding effects, including direct water saturation (DS), semi-solid non-specific magnetization transfer (MT), the influence of water relaxation times (T1w ) and nearby overlapping CEST signals...
November 29, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/29154463/establishing-upper-limits-on-neuronal-activity-evoked-ph-changes-with-apt-cest-mri-at-7-t
#10
Vitaliy Khlebnikov, Jeroen C W Siero, Alex A Bhogal, Peter R Luijten, Dennis W J Klomp, Hans Hoogduin
PURPOSE: To detect neuronal activity-evoked pH changes by amide proton transfer-chemical exchange saturation transfer (APT-CEST) MRI at 7 T. METHODS: Three healthy subjects participated in the study. A low-power 3-dimensional APT-CEST sequence was optimized through the Bloch-McConnell equations. pH sensitivity of the sequence was estimated both in phantoms and in vivo. The feasibility of pH-functional MRI was tested in Bloch-McConnell-simulated data using the optimized sequence...
November 20, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29150896/stereospecific-control-of-peptide-gas-phase-ion-chemistry-with-cis-and-trans-cyclo-ornithine-residues
#11
Aleš Marek, Huong T H Nguyen, Břetislav Brož, František Tureček
We report non-chiral amino acid residues cis- and trans-1,4-diaminocyclohexane-1-carboxylic acid (cyclo-ornithine, cO) that exhibit unprecedented stereospecific control of backbone dissociations of singly charged peptide cations and hydrogen-rich cation radicals produced by electron-transfer dissociation (ETD). Upon collision-induced dissociation (CID) in the slow heating regime, peptide cations containing trans-cO residues undergo facile backbone cleavages of amide bonds C-terminal to trans-cO. In contrast, peptides with cis-cO residues undergo dissociations at several amide bonds along the peptide ion backbone...
November 18, 2017: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/29111410/the-z-spectrum-from-human-blood-at-7t
#12
Simon M Shah, Olivier E Mougin, Andrew J Carradus, Nicolas Geades, Richard Dury, William Morley, Penny A Gowland
Chemical Exchange Saturation Transfer (CEST) has been used to assess healthy and pathological tissue in both animals and humans. However, the CEST signal from blood has not been fully assessed. This paper presents the CEST and nuclear Overhauser enhancement (NOE) signals detected in human blood measured via z-spectrum analysis. We assessed the effects of blood oxygenation levels, haematocrit, cell structure and pH upon the z-spectrum in ex vivo human blood for different saturation powers at 7T. The data were analysed using Lorentzian difference (LD) model fitting and AREX (to compensate for changes in T1), which have been successfully used to study CEST effects in vivo...
October 27, 2017: NeuroImage
https://www.readbyqxmd.com/read/29098732/differentiating-the-histologic-grades-of-gliomas-preoperatively-using-amide-proton-transfer-weighted-aptw-and-intravoxel-incoherent-motion-mri
#13
Tianyu Zou, Hao Yu, Chunxiu Jiang, Xianlong Wang, Shanshan Jiang, Qihong Rui, Yingjie Mei, Jinyuan Zhou, Zhibo Wen
The purpose of this work was to investigate the diagnostic performance of amide proton transfer-weighted (APTW) and intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in the preoperative grading of gliomas. Fifty-one patients with suspected gliomas were recruited and underwent a preoperative MRI examination that included APTW and IVIM sequences. All cases were confirmed by postsurgical histopathology. APTW signal intensity, true diffusion coefficient (D), perfusion fraction (f) and pseudo-diffusion coefficient (D*) were applied to assess the solid tumor component and contralateral normal-appearing white matter...
November 3, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/29083987/amide-proton-transfer-mr-imaging-of-endometrioid-endometrial-adenocarcinoma-association-with-histologic-grade
#14
Yukihisa Takayama, Akihiro Nishie, Osamu Togao, Yoshiki Asayama, Kousei Ishigami, Yasuhiro Ushijima, Daisuke Okamoto, Nobuhiro Fujita, Kenzo Sonoda, Tomoyuki Hida, Yoshihiro Ohishi, Jochen Keupp, Hiroshi Honda
Purpose To evaluate the utility of amide proton transfer (APT) imaging in estimating histologic grades of endometrioid endometrial adenocarcinoma (EEA). Materials and Methods The institutional review board approved this prospective study. Between June 2012 and March 2016, 32 patients with EEA underwent magnetic resonance (MR) imaging. After their surgical procedures, their EEAs were confirmed pathologically and classified into histologic grades: grade 1 (n = 11), grade 2 (n = 11), and grade 3 (n = 10). The APT signal intensities (SIs) and the mean and minimum apparent diffusion coefficients (ADCs) of the three grades were calculated and compared...
October 30, 2017: Radiology
https://www.readbyqxmd.com/read/29067395/toward-inert-paramagnetic-ni-ii-based-chemical-exchange-saturation-transfer-mri-agents
#15
Laura Caneda-Martínez, Laura Valencia, Isabel Fernández-Pérez, Martín Regueiro-Figueroa, Goran Angelovski, Isabel Brandariz, David Esteban-Gómez, Carlos Platas-Iglesias
The Ni(2+) complexes with hexadentate ligands containing two 6-methylpicolinamide groups linked by ethane-1,2-diamine (dedpam) or cyclohexane-1,2-diamine (chxdedpam) spacers were investigated as potential contrast agents in magnetic resonance imaging (MRI). The properties of the complexes were compared to that of the analogues containing 6-methylpicolinate units (dedpa(2-) and chxdedpa(2-)). The X-ray structure of the [Ni(dedpam)](2+) complex reveals a six-coordinated metal ion with a distorted octahedral environment...
November 7, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29063304/applying-amide-proton-transfer-mr-imaging-to-hybrid-brain-pet-mr-concordance-with-gadolinium-enhancement-and-added-value-to-18-f-fdg-pet
#16
Hongzan Sun, Jun Xin, Jinyuan Zhou, Zaiming Lu, Qiyong Guo
PURPOSE: The purpose of this study is to evaluate the diagnostic concordance and metric correlations of amide proton transfer (APT) imaging with gadolinium-enhanced magnetic resonance imaging (MRI) and 2-deoxy-2-[(18)F-]fluoro-D-glucose ([(18)F]FDG) positron emission tomography (PET), using hybrid brain PET/MRI. PROCEDURES: Twenty-one subjects underwent brain gadolinium-enhanced [(18)F]FDG PET/MRI prospectively. Imaging accuracy was compared between unenhanced MRI, MRI with enhancement, APT-weighted (APTW) images, and PET based on six diagnostic criteria...
October 23, 2017: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/29059929/assessment-of-chemoradiotherapy-response-in-glioma-with-magnetic-resonance-amide-proton-transfer-imaging-in-a-rodent-model
#17
Jing Zhao, Yinsheng Chen, Yiying Zhao, Shasha Yang, Zhongping Chen, Yin Wu
Magnetic resonance amide proton transfer (APT) imaging has proved its potential for detecting tumors and evaluating treatment response by depicting chemical exchange saturation transfer effect between the endogenous protein/peptide amide proton and bulk water. However, conventional asymmetry analysis for APT effect measurement is susceptible to concomitant contributions, particular semisolid magnetic transfer (MT) and nuclear overhauser effect. In this study, dominant saturation transfer (ST) effects, including direct water saturation and MT, were estimated from a sum of two Lorentzian functions...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29034505/in-vivo-characterization-of-the-downfield-part-of-1-h-mr-spectra-of-human-brain-at-9-4-t-magnetization-exchange-with-water-and-relation-to-conventionally-determined-metabolite-content
#18
Nicole D Fichtner, Ioannis-Angelos Giapitzakis, Nikolai Avdievich, Ralf Mekle, Daniel Zaldivar, Anke Henning, Roland Kreis
PURPOSE: To perform exchange-rate measurements on the in vivo human brain downfield spectrum (5-10 ppm) at 9.4 T and to compare the variation in concentrations of the downfield resonances and of known upfield metabolites to determine potential peak labels. METHODS: Non-water-suppressed metabolite cycling was used in combination with an inversion transfer technique in two brain locations in healthy volunteers to measure the exchange rates and T1 values of exchanging peaks...
October 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29030880/direct-saturation-corrected-chemical-exchange-saturation-transfer-mri-of-glioma-simplified-decoupling-of-amide-proton-transfer-and-nuclear-overhauser-effect-contrasts
#19
Iris Yuwen Zhou, Enfeng Wang, Jerry S Cheung, Dongshuang Lu, Yang Ji, Xiaoan Zhang, Giulia Fulci, Phillip Zhe Sun
PURPOSE: Chemical exchange saturation transfer (CEST) MRI has shown promise in tissue characterization in diseases like stroke and tumor. However, in vivo CEST imaging such as amide proton transfer (APT) MRI is challenging because of concomitant factors such as direct water saturation, macromolecular magnetization transfer, and nuclear overhauser effect (NOE), which lead to a complex contrast in the commonly used asymmetry analysis (MTRasym). Here, we propose a direct saturation-corrected CEST (DISC-CEST) analysis for simplified decoupling and quantification of in vivo CEST effects...
October 13, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29028326/ratiometric-ph-imaging-with-a-co-ii-2-mri-probe-via-cest-effects-of-opposing-ph-dependences
#20
Agnes E Thorarinsdottir, Kang Du, James H P Collins, T David Harris
We report a Co2-based magnetic resonance (MR) probe that enables the ratiometric quantitation and imaging of pH through chemical exchange saturation transfer (CEST). This approach is illustrated in a series of air- and water-stable Co(II)2 complexes featuring CEST-active tetra(carboxamide) and/or hydroxyl-substituted bisphosphonate ligands. For the complex bearing both ligands, variable-pH CEST and NMR analyses reveal highly shifted carboxamide and hydroxyl peaks with intensities that increase and decrease with increasing pH, respectively...
October 30, 2017: Journal of the American Chemical Society
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