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Amide proton transfer

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https://www.readbyqxmd.com/read/29193448/increased-cest-specificity-for-amide-and-fast-exchanging-amine-protons-using-exchange-dependent-relaxation-rate
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
https://www.readbyqxmd.com/read/29024066/a-comparison-of-exogenous-and-endogenous-cest-mri-methods-for-evaluating-in-vivo-ph
#13
Leila R Lindeman, Edward A Randtke, Rachel A High, Kyle M Jones, Christine M Howison, Mark D Pagel
PURPOSE: Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (kex ) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous kex could be used as a proxy for pHe measurements. METHODS: Spatial maps of pHe and kex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model...
October 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28989630/efficient-stabilisation-of-a-dihydrogenphosphate-tetramer-and-a-dihydrogenpyrophosphate-dimer-by%C3%A2-a-cyclic-pseudopeptide-containing-1-4-disubstituted-1-2-3-triazole-moieties
#14
Disha Mungalpara, Arto Valkonen, Kari Rissanen, Stefan Kubik
A cyclic pseudooctapeptide 2 is described containing 1,4-disubstituted 1,2,3-triazole moieties. This compound features eight converging hydrogen bond donors along the ring, namely four amide NH and four triazole CH groups, which enable 2 to engage in interactions with anions. While fully deprotonated sulfate anions exhibit only moderate affinity for 2, protonated anions such as dihydrogenpyrophosphate and dihydrogenphosphate anions are strongly bound. Complexation of the phosphate-derived anions involves sandwiching of a dihydrogenpyrophosphate dimer or a dihydrogenphosphate tetramer between two pseudopeptide rings...
September 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28942555/the-applicability-of-amide-proton-transfer-imaging-in-the-nervous-system-focus-on-hypoxic-ischemic-encephalopathy-in-the-neonate
#15
REVIEW
Yang Zheng, Xiaoming Wang
In recent years, magnetic resonance imaging (MRI) has become more widely used in neonatal hypoxic-ischemic encephalopathy (HIE), involving, for example, evaluation of cerebral edema, white matter fiber bundle tracking, cerebral perfusion status, and assessment of brain metabolites. MRI has many imaging modalities. However, its application for assessing changes in the internal environment at the tissue and cellular level after hypoxia-ischemia remains a challenge and is currently the focus of intense research...
September 23, 2017: Cellular and Molecular Neurobiology
https://www.readbyqxmd.com/read/28932452/crystal-structure-of-a-1-1-2-2-tetra-chloro-ethane-solvated-hydrazinecarbo-thio-amide-compound
#16
Sayed Riyadh, David L Hughes, Musa A Said
The title compound, [(1-{4-[2-(2,4-di-hydroxy-phen-yl)diazen-1-yl]phen-yl}ethyl-idene)amino]-thio-urea, 1,1,2,2-tetra-chloro-ethane monosolvate, C15H15N5O2S·C2H2Cl4, was prepared from 4-(4-acetyl-phenyl-diazendi-yl)resorcinol and thio-semicarbazide and recrystallized from mixed solvents of tetra-chloro-ethane and n-hexane. (1)H NMR and X-ray diffraction data are in support of the thione tautomeric form. The X-ray analysis shows the mol-ecule crystallizes as a zwitterion, with proton transfer from the nominal phenol to the azide group; the N-N bond length is 1...
September 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28921821/iridium-catalyzed-direct-c-h-amidation-polymerization-step-growth-polymerization-by-c-n-bond-formation-via-c-h-activation-to-give-fluorescent-polysulfonamides
#17
Yoon-Jung Jang, Soon-Hyeok Hwang, Tae-Lim Choi
We report a powerful strategy for activation of C-H bonds to produce polysulfonamides by an atom-economical and green method using iridium-catalyzed direct C-H amidation polymerization (DCAP). After screening various directing groups, additives, silver salts, concentrations, and temperatures to optimize DCAP, high-molecular-weight (up to 149 kDa) and defect-free polysulfonamides were synthesized from various bis-sulfonyl azides. Although these polymers do not have conventional fluorescent conjugated cores, they emit blue light with large Stokes shifts and high quantum yields upon photoexcitation owing to an excited-state intramolecular proton-transfer process...
September 15, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28912676/chemical-exchange-saturation-transfer-mri-signal-loss-of-the-substantia-nigra-as-an-imaging-biomarker-to-evaluate-the-diagnosis-and-severity-of-parkinson-s-disease
#18
Chunmei Li, Min Chen, Xuna Zhao, Rui Wang, Haibo Chen, Wen Su, Shuhua Li, Baohui Lou, Guodong Song, Shuai Zhang, Jintao Zhang, Jinyuan Zhou
The early diagnosis of Parkinson's disease (PD) and the accurate evaluation of disease severity are crucial for intervention and treatment in PD patients. In this study, we applied chemical exchange saturation transfer (CEST) imaging to patients at different stages of PD and explored the clinical value of the CEST signal loss of the substantia nigra as an imaging biomarker of PD. The measured CEST signal intensities (including amide proton transfer-weighted or APTw, and total CEST or CESTtotal) of the substantia nigra in PD patients showed a significantly decreased tendency with PD progression...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28833781/catalytic-carbon-carbon-bond-forming-reactions-of-weakly-acidic-carbon-pronucleophiles-using-strong-br%C3%A3-nsted-bases-as-catalysts
#19
Yasuhiro Yamashita, Shu Kobayashi
Catalytic carbon-carbon bond-forming reactions of weakly acidic carbon pronucleophiles with N-aryl imines, α,β-unsaturated amides, and others under proton-transfer conditions were developed by designing strongly basic reaction intermediates known as product bases. The reactions proceed smoothly in the presence of a catalytic amount of strong base such as KH or alkaline metal amides. Modification of the metal cations by using chiral macrocyclic crown ethers allowed catalytic asymmetric 1,4-addition reactions to proceed with high enantioselectivities...
August 23, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28808429/fast-reliable-3d-amide-proton-transfer-imaging-of-brain-tumors-at-3t-with-variably-accelerated-sensitivity-encoding-vsense
#20
Yi Zhang, Hye-Young Heo, Shanshan Jiang, Paul A Bottomley, Jinyuan Zhou
The clinical use of amide proton transfer (APT) imaging is hindered by long scan times. Accuracy generally limits the use of conventional sensitivity encoding (SENSE) methods in APT, to an acceleration factor of 2. A novel variably-accelerated sensitivity encoding (vSENSE) method can provide more accurate results and therefore substantially higher overall acceleration factors than conventional SENSE. Here, vSENSE is further developed to eliminate the requirement that one fully-sampled APT frame be acquired, and extended to three dimensions (3D)...
April 2017: Proceedings of the International Society for Magnetic Resonance in Medicine ... Scientific Meeting and Exhibition
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