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Amide proton transfer

Akihiro Nishie, Yoshiki Asayama, Kousei Ishigami, Yasuhiro Ushijima, Yukihisa Takayama, Daisuke Okamoto, Nobuhiro Fujita, Daisuke Tsurumaru, Osamu Togao, Koji Sagiyama, Tatsuya Manabe, Eiji Oki, Yuichiro Kubo, Tomoyuki Hida, Minako Hirahashi-Fujiwara, Jochen Keupp, Hiroshi Honda
BACKGROUND AND AIM: The amount of proteins and peptides can be estimated with amide proton transfer (APT) imaging. Previous studies demonstrated the usefulness of APT imaging to predict tumor malignancy. We determined whether APT imaging can predict the tumor response to neoadjuvant chemotherapy (NAC) in patients with locally advanced rectal cancer (LARC). METHODS: Seventeen patients with LARC who underwent a pretherapeutic magnetic resonance examination including APT imaging and NAC (at least two courses) were enrolled...
June 13, 2018: Journal of Gastroenterology and Hepatology
Erwin Krikken, Vitaliy Khlebnikov, Moritz Zaiss, Rajni A Jibodh, Paul J van Diest, Peter R Luijten, Dennis W J Klomp, Hanneke W M van Laarhoven, Jannie P Wijnen
BACKGROUND: The purpose of this work was to investigate noninvasive early detection of treatment response of breast cancer patients to neoadjuvant chemotherapy (NAC) using chemical exchange saturation transfer (CEST) measurements sensitive to amide proton transfer (APT) at 7 T. METHODS: CEST images were acquired in 10 tumors of nine breast cancer patients treated with NAC. APT signals in the tumor, before and after the first cycle of NAC, were quantified using a three-pool Lorentzian fit of the z-spectra in the region of interest...
June 14, 2018: Breast Cancer Research: BCR
Moritz Zaiss, Mark Schuppert, Anagha Deshmane, Kai Herz, Philipp Ehses, Lars Füllbier, Tobias Lindig, Benjamin Bender, Ulrike Ernemann, Klaus Scheffler
PURPOSE: The high chemical shift separation at 9.4 T allows for selective saturation of proton pools in exchange with water protons. For the first time, highly selective and comprehensive chemical exchange saturation transfer (CEST) experiments were performed in the human brain at 9.4 T. This work provides insight into CEST signals in the human brain in comparison with existing animal studies, as well as with CEST effects in vivo at lower field strengths. METHODS: A novel snapshot-CEST method for human brain scans at 9...
June 9, 2018: NeuroImage
Benjamin King Hong Law, Ann D King, Qi-Yong Ai, Darren M C Poon, Weitian Chen, Kunwar S Bhatia, Anil T Ahuja, Brigette B Ma, David Ka-Wai Yeung, Frankie Kwok Fai Mo, Yi-Xiang Wang, Jing Yuan
Purpose To evaluate the utility of amide proton transfer (APT) imaging in the characterization of head and neck tumors. Materials and Methods This retrospective study of APT imaging included 117 patients with 70 nasopharyngeal undifferentiated carcinomas (NUCs), 26 squamous cell carcinomas (SCCs), eight non-Hodgkin lymphomas (NHLs), and 13 benign salivary gland tumors (BSGTs). Normal tissues were examined in 25 patients. The APT means of malignant tumors, normal tissues, and benign tumors were calculated and compared with the Student t test and analysis of variance...
June 12, 2018: Radiology
Seung Hong Choi
No abstract text is available yet for this article.
June 12, 2018: Radiology
Hatef Mehrabian, Sten Myrehaug, Hany Soliman, Arjun Sahgal, Greg J Stanisz
PURPOSE: To monitor cellular and metabolic characteristics of glioblastoma (GBM) over the course of standard 6-week chemoradiation treatment with chemical exchange saturation transfer (CEST)-MRI; and to identify the earliest time point CEST could determine subsequent therapeutic response. METHODS AND MATERIALS: Nineteen patients with newly diagnosed GBM were recruited, and CEST-MRI was acquired immediately before (Day0 ), 2 weeks (Day14 ) and 4 weeks (Day28 ) into treatment, and 1 month after the end of treatment (Day70 )...
July 1, 2018: International Journal of Radiation Oncology, Biology, Physics
Zhongliang Zu
Amide proton transfer (APT) imaging is a variation of chemical exchange saturation transfer MRI that has shown promise in diagnosing tumors, ischemic stroke, multiple sclerosis, traumatic brain injury, etc. Specific quantification of the APT effect is crucial for the interpretation of APT contrast in pathologies. Conventionally, magnetization transfer ratio with asymmetric analysis (MTRasym ) has been used to quantify the APT effect. However, some studies indicate that MTRasym is contaminated by water longitudinal relaxation time (T1w ), and thus it is necessary to normalize T1w in MTRasym to obtain specific quantification of the APT effect...
May 28, 2018: NMR in Biomedicine
Lu Su, Peiyi Gao, Song Lin, Bing Wu, Wen Qin, Yan Lin, Jing Xue
OBJECTIVE: To demonstrate that certain qualitative amide proton transfer-weighted (APTw) characteristics can provide practical imaging clues for predicting O6-methylguanine-DNA methyltransferase (MGMT) protein expression in primary low and high-grade gliomas, preoperatively and non-invasively. METHODS: Forty-two patients with pathologically confirmed low- and high-grade gliomas were recruited in this study. The MGMT protein expression status was classified by post-surgery specimen immunostaining...
May 23, 2018: World Neurosurgery
Eugene C Lin, Hua Li, Zhongliang Zu, Elizabeth A Louie, Christopher L Lankford, Richard D Dortch, Mark D Does, John C Gore, Daniel F Gochberg
PURPOSE: To test the ability of a novel pulse sequence applied in vivo at 3 Tesla to separate the contributions to the water signal from amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background direct water saturation and semisolid magnetization transfer (MT). The lack of such signal source isolation has confounded conventional chemical exchange saturation transfer (CEST) imaging. METHODS: We quantified APT and rNOE signals using a chemical exchange rotation transfer (CERT) metric, MTRdouble ...
May 25, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Łukasz Kielesiński, Daniel T Gryko, Andrzej L Sobolewski, Olaf W Morawski
The fluorescence intensity of bis-coumarins linked via CONH and COO functionalities are shown to exhibit a strong dependance on solvent polarity. The presence of the intramolecular hydrogen bond between the C[double bond, length as m-dash]O oxygen atom of coumarin and amide-NH moieties reduces the number of thermodynamically populated conformations in both ground and electronically excited states and an anti-arrangement of coumarin units is favored. Additionally, the rigidity of the linker raises the barrier to the conical intersection with the ground state, and in non-polar solvents strong fluorescence is observed...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
Ouri Cohen, Shuning Huang, Michael T McMahon, Matthew S Rosen, Christian T Farrar
PURPOSE: To develop a fast magnetic resonance fingerprinting (MRF) method for quantitative chemical exchange saturation transfer (CEST) imaging. METHODS: We implemented a CEST-MRF method to quantify the chemical exchange rate and volume fraction of the Nα -amine protons of L-arginine (L-Arg) phantoms and the amide and semi-solid exchangeable protons of in vivo rat brain tissue. L-Arg phantoms were made with different concentrations (25-100 mM) and pH (pH 4-6)...
May 13, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Zhanjun Guo, Jiayuan He, Bridgette A Barry
In Photosystem II (PSII), YZ (Tyr161D1) participates in radical transfer between the chlorophyll donor and the Mn4 CaO5 cluster. Under flashing illumination, the metal cluster cycles among five Sn states, and oxygen is evolved from water. The essential YZ is transiently oxidized and reduced on each flash in a proton-coupled electron transfer (PCET) reaction. Calcium is required for function. Of reconstituted divalent ions, only strontium restores oxygen evolution. YZ is predicted to hydrogen bond to calcium-bound water and to His190D1 in PSII structures...
May 11, 2018: Proceedings of the National Academy of Sciences of the United States of America
Bin Zhang, Hengzhao Li, Yuxuan Ding, Yuhao Yan, Jie An
A practical and scalable single electron transfer reduction mediated by sodium dispersions has been developed for the reduction and reductive deuteration of tertiary amides. The chemoselectivity of this method highly depends on the nature of the proton donor. The challenging reduction via C-N bond cleavage has been achieved using Na/EtOH, affording alcohol products, while the use of Na/NaOH/H2O leads to the formation of amines via selective C-O scission. Sodium dispersions with high specific surface areas are crucial to obtain high yields and good chemoselectivity...
May 11, 2018: Journal of Organic Chemistry
Mohammed Albatany, Alex Li, Susan Meakin, Robert Bartha
Glioblastoma is an aggressive brain cancer that is very difficult to treat. Clinically, it is important to be able to distinguish aggressive from non-aggressive brain tumors. Previous studies have shown that some drugs can induce a rapid change in intracellular pH that could help to identify aggressive cancer. The sodium proton exchanger (NHE1) plays a significant role in maintaining pH balance in the tumor microenvironment. Cariporide is a sodium proton exchange inhibitor that is well tolerated by humans in cardiac applications...
May 10, 2018: International Journal of Clinical Oncology
Daniel Paech, Johannes Windschuh, Johanna Oberhollenzer, Constantin Dreher, Felix Sahm, Jan-Eric Meissner, Steffen Goerke, Patrick Schuenke, Moritz Zaiss, Sebastian Regnery, Sebastian Bickelhaupt, Philipp Bäumer, Martin Bendszus, Wolfgang Wick, Andreas Unterberg, Peter Bachert, Mark Edward Ladd, Heinz-Peter Schlemmer, Alexander Radbruch
Background: Early identification of prognostic superior characteristics in glioma patients such as Isocitrate dehydrogenase(IDH)-mutation and O6-methylguanine-DNA-methyltransferase (MGMT) promotor methylation status is of great clinical importance. The study purpose was to investigate the non-invasive predictability of IDH-mutation status, MGMT promotor methylation, and differentiation of lower versus higher grade glioma (LGG vs. HGG) in newly-diagnosed patients employing relaxation-compensated multi-pool Chemical Exchange Saturation Transfer (CEST) magnetic resonance imaging (MRI) at 7...
May 4, 2018: Neuro-oncology
Akihiro Nishie, Yukihisa Takayama, Yoshiki Asayama, Kousei Ishigami, Yasuhiro Ushijima, Daisuke Okamoto, Nobuhiro Fujita, Daisuke Tsurumaru, Osamu Togao, Tatsuya Manabe, Eiji Oki, Yuichiro Kubo, Tomoyuki Hida, Minako Hirahashi-Fujiwara, Jochen Keupp, Hiroshi Honda
PURPOSE: To prospectively investigate the ability of amide proton transfer (APT) imaging, in comparison with that of diffusion-weighted imaging (DWI), to predict pathological factors in rectal cancer. MATERIALS AND METHODS: Twenty-two patients who underwent MR examination including APT imaging and DWI for evaluation of rectal cancer were enrolled. APT signal intensity (SI) was defined as the magnetization transfer asymmetry at 3.5 ppm and was mapped. An apparent diffusion coefficient (ADC) map was generated using b-values of 0, 500 and 1000 s/mm2 ...
May 2, 2018: Magnetic Resonance Imaging
Yuan Liu, Abosede Adejoke Ogunlana, Xiaoguang Bao
The mechanisms of transition metal-catalyzed methylenecyclopropanes (MCPs)-involved reactions are rather complicated due to the diverse pathways for the activation of MCPs. Herein, computational studies were carried out to investigate the detailed mechanisms of Pd(0)-catalyzed intermolecular and intramolecular hydroamination of MCPs. The initial activation of the three-membered ring of MCPs readily occurs via the insertion of Pd(0) into the distal C-C bond, leading to a metallacyclobutane intermediate. The commonly proposed oxidative addition of amine/amide nucleophile (Nu-H) onto the Pd(0) center to afford a hydrido-Pd(ii) complex, however, is less favorable in comparison with the Pd(0)-mediated cleavage of the distal C-C bond of MCPs...
April 24, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yini Zuo, Na Yang, Xunkun Huang, Changwei Hu, Zhishan Su
The mechanism and selectivity of the asymmetric Friedel-Crafts (F-C) alkylation reaction between indole and chalcone catalyzed by chiral N, N'-dioxide-Sc(III) complexes were investigated at the M06/6-311+G(d,p)//M06/[LANL2DZ,6-31G(d)](SMD,CH2 Cl2 ) level. The reaction occurred via a three-step mechanism: (i) the C3 -Cβ bond formation by interacting the most mucleophilic C3 center of indole with the most electrophilic Cβ center of chalcone; (ii) the abstraction of the proton at the C3 atom of indole by counterion OTf- ; (iii) proton transfer from HOTf to the Cα atom of chalcone, generating the F-C alkylation product...
April 20, 2018: Journal of Organic Chemistry
Manisha Bohara, Kiyohisa Kamimura, Masanori Nakajo, Tomohide Yoneyama, Takashi Yoshiura
No abstract text is available yet for this article.
March 13, 2018: Magnetic Resonance in Medical Sciences: MRMS
Or Szekely, Gregory Lars Olsen, Isabella C Felli, Lucio Frydman
This study demonstrates the usefulness derived from relying on hyperpolarized water obtained by dissolution DNP, for site-resolved biophysical NMR studies of intrinsically disordered proteins. Thanks to the facile amide-solvent exchange experienced by protons in these proteins, 2D NMR experiments that like HMQC rely on the polarization of the amide protons, can be enhanced using hyperpolarized water by several orders of magnitude over their conventional counterparts. Optimizations of the DNP procedure and of the subsequent injection into the protein sample are necessary to achieve these gains while preserving state-of-the-art resolution; procedures enabling this transfer of the hyperpolarized water and the achievement of foamless hyperpolarized protein solutions are demonstrated...
May 15, 2018: Analytical Chemistry
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