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Amide proton transfer

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https://www.readbyqxmd.com/read/28729292/amide-proton-transfer-imaging-allows-detection-of-glioma-grades-and-tumor-proliferation-comparison-with-ki-67-expression-and-proton-mr-spectroscopy-imaging
#1
C Su, C Liu, L Zhao, J Jiang, J Zhang, S Li, W Zhu, J Wang
BACKGROUND AND PURPOSE: Prognosis in glioma depends strongly on tumor grade and proliferation. In this prospective study of patients with untreated primary cerebral gliomas, we investigated whether amide proton transfer-weighted imaging could reveal tumor proliferation and reliably distinguish low-grade from high-grade gliomas compared with Ki-67 expression and proton MR spectroscopy imaging. MATERIALS AND METHODS: This study included 42 patients with low-grade (n = 28) or high-grade (n = 14) glioma, all of whom underwent conventional MR imaging, proton MR spectroscopy imaging, and amide proton transfer-weighted imaging on the same 3T scanner within 2 weeks before surgery...
July 20, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/28717802/a-computational-study-on-the-mechanism-of-ynamide-mediated-amide-bond-formation-from-carboxylic-acids-and-amines
#2
Song-Lin Zhang, Hai-Xing Wan, Zhu-Qin Deng
This paper reports a computational study elucidating the reaction mechanism for ynamide-mediated amide bond formation from carboxylic acids and amines. The mechanisms have been studied in detail for ynamide hydrocarboxylation and the subsequent aminolysis of the resulting adduct by an amine. Ynamide hydrocarboxylation is kinetically favorable and thermodynamically irreversible, resulting in the formation of a key low-lying intermediate CP1 featuring geminal vinylic acyloxy and sulfonamide groups. The aminolysis of CP1 by the amine is proposed to be catalyzed by the carboxylic acid itself that imparts favourable bifunctional effects...
July 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28714279/predicting-idh-mutation-status-in-grade-ii-gliomas-using-amide-proton-transfer-weighted-aptw-mri
#3
Shanshan Jiang, Tianyu Zou, Charles G Eberhart, Maria A V Villalobos, Hye-Young Heo, Yi Zhang, Yu Wang, Xianlong Wang, Hao Yu, Yongxing Du, Peter C M van Zijl, Zhibo Wen, Jinyuan Zhou
PURPOSE: To assess the amide proton transfer-weighted (APTw) MRI features of isocitrate dehydrogenase (IDH)-wildtype and IDH-mutant grade II gliomas and to test the hypothesis that the APTw signal is a surrogate imaging marker for identifying IDH mutation status preoperatively. METHODS: Twenty-seven patients with pathologically confirmed low-grade glioma, who were previously scanned at 3T, were retrospectively analyzed. The Mann-Whitney test was used to evaluate relationships between APTw intensities for IDH-mutant and IDH-wildtype groups, and receiver operator characteristic (ROC) analysis was used to assess the diagnostic performance of APTw...
July 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28708326/loss-of-benzaldehyde-in-the-fragmentation-of-protonated-benzoylamines-benzoyl-cation-as-a-hydride-acceptor-in-the-gas-phase
#4
Yunfeng Chai, Yunlong Shao, Lu Wang, Lin Wang
In electrospray ionization tandem mass spectrometry of protonated 1-benzoylamines (1-benzoylpiperadine, 1-benzoylmorpholine, and 1-benzoyl-4-methylpiperazine), the dominant fragmentation pathway was amide bond cleavage to form benzoyl cation and neutral amine. Meanwhile, in their fragmentations, an interesting loss of benzaldehyde (106 Da) was observed and identified to derive from hydride transfer reaction between the benzoyl cation and amine. A stepwise mechanism for loss of 106 Da (benzene and CO) could be excluded with the aid of deuterium labeling experiment...
July 14, 2017: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/28707688/probing-the-excited-state-chemical-shifts-and-exchange-parameters-by-nitrogen-decoupled-amide-proton-chemical-exchange-saturation-transfer-hn-dec-cest
#5
Qinglin Wu, Benjamin A Fenton, Jessica L Wojtaszek, Pei Zhou
CEST-NMR spectroscopy is a powerful tool for probing the conformational dynamics of macromolecules. We present a HN(dec)-CEST experiment that simplifies the relaxation matrix, reduces fitting parameters, and enhances signal resolution. Importantly, fitting of HN(dec)-CEST profiles enables robust extraction of exchange rates as well as excited-state chemical shifts and populations.
July 14, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28704644/amide-proton-transfer-weighted-magnetic-resonance-image-guided-stereotactic-biopsy-in-patients-with-newly-diagnosed-gliomas
#6
Shanshan Jiang, Charles G Eberhart, Yi Zhang, Hye-Young Heo, Zhibo Wen, Lindsay Blair, Huamin Qin, Michael Lim, Alfredo Quinones-Hinojosa, Jon D Weingart, Peter B Barker, Martin G Pomper, John Laterra, Peter C M van Zijl, Jaishri O Blakeley, Jinyuan Zhou
PURPOSE: Pathological assessment using World Health Organization (WHO) criteria is the gold standard for diagnosis of gliomas. However, the accuracy of diagnosis is limited by tissue sampling, particularly for infiltrating, heterogeneous tumours. We assessed the accuracy of amide proton transfer-weighted (APTw) magnetic resonance imaging (MRI)-guided tissue sampling to identify regions of high-grade glioma via radiographic-histopathologic correlation in patients with newly suspected glioma...
July 10, 2017: European Journal of Cancer
https://www.readbyqxmd.com/read/28687916/amide-proton-transfer-imaging-for-differentiation-of-benign-and-atypical-meningiomas
#7
Bio Joo, Kyunghwa Han, Yoon Seong Choi, Seung-Koo Lee, Sung Soo Ahn, Jong Hee Chang, Seok-Gu Kang, Se Hoon Kim, Jinyuan Zhou
PURPOSE: To investigate the difference in amide proton transfer (APT)-weighted signals between benign and atypical meningiomas and determine the value of APT imaging for differentiating the two. METHODS: Fifty-seven patients with pathologically diagnosed meningiomas (benign, 44; atypical, 13), who underwent preoperative MRI with APT imaging between December 2014 and August 2016 were included. We compared normalised magnetisation transfer ratio asymmetry (nMTR asym ) values between benign and atypical meningiomas on APT-weighted images...
July 7, 2017: European Radiology
https://www.readbyqxmd.com/read/28639301/improving-the-detection-sensitivity-of-ph-weighted-amide-proton-transfer-mri-in-acute-stroke-patients-using-extrapolated-semisolid-magnetization-transfer-reference-signals
#8
Hye-Young Heo, Yi Zhang, Tina M Burton, Shanshan Jiang, Yansong Zhao, Peter C M van Zijl, Richard Leigh, Jinyuan Zhou
PURPOSE: To quantify amide protein transfer (APT) effects in acidic ischemic lesions and assess the spatial-temporal relationship among diffusion, perfusion, and pH deficits in acute stroke patients. METHODS: Thirty acute stroke patients were scanned at 3 T. Quantitative APT (APT(#) ) effects in acidic ischemic lesions were measured using an extrapolated semisolid magnetization transfer reference signal technique and compared with commonly used MTRasym (3.5ppm) or APT-weighted parameters...
June 21, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28613875/modeling-of-polarization-transfer-kinetics-in-protein-hydration-using-hyperpolarized-water
#9
Jihyun Kim, Mengxiao Liu, Christian Hilty
Water-protein interactions play a central role in protein structure, dynamics, and function. These interactions, traditionally, have been studied using nuclear magnetic resonance (NMR) by measuring chemical exchange and nuclear Overhauser effect (NOE). Polarization transferred from hyperpolarized water can result in substantial transient signal enhancements of protein resonances due to these processes. Here, we use dissolution dynamic nuclear polarization and flow-NMR for measuring the pH dependence of transferred signals to the protein trypsin...
June 29, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28602944/enhancing-sensitivity-of-ph-weighted-mri-with-combination-of-amide-and-guanidyl-cest
#10
Tao Jin, Ping Wang, T Kevin Hitchens, Seong-Gi Kim
Amide-proton-transfer weighted (APTw) MRI has emerged as a non-invasive pH-weighted imaging technique for studies of several diseases such as ischemic stroke. However, its pH-sensitivity is relatively low, limiting its capability to detect small pH changes. In this work, computer simulations, protamine phantom experiments, and in vivo gas challenge and experimental stroke in rats showed that, with judicious selection of the saturation pulse power, the amide-CEST at 3.6ppm and guanidyl-CEST signals at 2.0ppm changed in opposite directions with decreased pH...
June 7, 2017: NeuroImage
https://www.readbyqxmd.com/read/28582725/investigations-of-vibrational-spectra-and-bioactivity-of-novel-anticancer-drug-n-6-ferrocenyl-2-naphthoyl-gamma-amino-butyric-acid-ethyl-ester
#11
Geethu Sudhi, S R Rajina, S G Praveen, T S Xavier, Peter T M Kenny, D Jaiswal-Nagar, J Binoy
The bioactivity of compounds is mainly dependent on molecular structure and the present work aims to explore the bonding features responsible for biological activity of novel anticancer drug N-(6-ferrocenyl-2-naphthoyl)-gamma-amino butyric acid ethyl ester (FNGABEE). In the present study, we investigate the molecular structural properties of newly synthesized title compound through experimental and quantum chemical studies. The detailed vibrational analysis has been performed using FT IR and FT Raman spectrum, aided by DFT computed geometry, vibrational spectrum, Eigen vector distribution and PED, at B3LYP/6-311++G(d,p) level...
May 28, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28578873/mechanism-informed-refinement-reveals-altered-substrate-binding-mode-for-catalytically-competent-nitroreductase
#12
Warintra Pitsawong, Chad A Haynes, Ronald L Koder, David W Rodgers, Anne-Frances Miller
Nitroreductase (NR) from Enterobacter cloacae reduces diverse nitroaromatics including herbicides, explosives, and prodrugs, and holds promise for bioremediation, prodrug activation, and enzyme-assisted synthesis. We solved crystal structures of NR complexes with bound substrate or analog for each of its two half-reactions. We complemented these with kinetic isotope effect (KIE) measurements elucidating H-transfer steps essential to each half-reaction. KIEs indicate hydride transfer from NADH to the flavin consistent with our structure of NR with the NADH analog nicotinic acid adenine dinucleotide (NAAD)...
July 5, 2017: Structure
https://www.readbyqxmd.com/read/28566586/b1-power-optimization-for-chemical-exchange-saturation-transfer-imaging-a-phantom-study-using-egg-white-for-amide-proton-transfer-imaging-applications-in-the-human-brain
#13
Yuki Kanazawa, Yasutaka Fushimi, Naotaka Sakashita, Tomohisa Okada, Yoshiki Arakawa, Mitsue Miyazaki
The chemical exchange saturation transfer (CEST) effect on an egg white (EW) suspension was investigated for optimization of magnetization transfer (MT) power (B1,rms) and pH dependency with the addition of lactic acid. Applying a higher MT pulse, B1,rms, Z-spectrum shows higher asymmetry and the magnetisation transfer ratio (MTR)asym signal increases to around 1-3.5 ppm, indicating a higher CEST effect. Amide proton transfer (APT) at 3.5 ppm shows a signal elevation in MTRasym with the application of higher B1,rms power and high pH...
May 31, 2017: Magnetic Resonance in Medical Sciences: MRMS
https://www.readbyqxmd.com/read/28558170/collision-induced-dissociation-of-phenethylamides-role-of-ion-neutral-complex
#14
Dejan Nikolić, Carmen Macias, David C Lankin, Richard B van Breemen
RATIONALE: Phenethylamides are a large group of naturally occurring molecules found both in the plant and animal kingdoms. In addition, they are used as intermediates for the synthesis of pharmaceutically important dihydro- and tetrahydroisoquinolines. To enable efficient characterization of this class of molecules, a detailed mass spectrometric fragmentation study of a broad series of analogs was carried out. METHODS: The test compounds were synthesized using standard methods for amide bond formation...
May 30, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28544035/chemical-exchange-sensitive-mri-of-amide-amine-and-noe-at-9-4%C3%A2-t-versus-15-2%C3%A2-t
#15
Julius Juhyun Chung, Wonmin Choi, Tao Jin, Jung Hee Lee, Seong-Gi Kim
Chemical exchange (CE)-sensitive MRI benefits greatly from stronger magnetic fields; however, field effects on CE-sensitive imaging have not yet been studied well in vivo. We have compared CE-sensitive Z-spectra and maps obtained at the fields of 9.4 T and 15.2 T in phantoms and rats with off-resonance chemical-exchange-sensitive spin lock (CESL), which is similar to conventional chemical exchange saturation transfer. At higher fields, the background peak at water resonance has less spread and the exchange rate relative to chemical shift decreases, thus CESL intensity is dependent on B0 ...
May 22, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28534162/applying-protein-based-amide-proton-transfer-mr-imaging-to-distinguish-solitary-brain-metastases-from-glioblastoma
#16
Hao Yu, Huiling Lou, Tianyu Zou, Xianlong Wang, Shanshan Jiang, Zhongqing Huang, Yongxing Du, Chunxiu Jiang, Ling Ma, Jianbin Zhu, Wen He, Qihong Rui, Jianyuan Zhou, Zhibo Wen
OBJECTIVES: To determine the utility of amide proton transfer-weighted (APTw) MR imaging in distinguishing solitary brain metastases (SBMs) from glioblastomas (GBMs). METHODS: Forty-five patients with SBMs and 43 patients with GBMs underwent conventional and APT-weighted sequences before clinical intervention. The APTw parameters and relative APTw (rAPTw) parameters in the tumour core and the peritumoral brain zone (PBZ) were obtained and compared between SBMs and GBMs...
May 22, 2017: European Radiology
https://www.readbyqxmd.com/read/28526431/measurement-of-apt-using-a-combined-cert-arex-approach-with-varying-duty-cycles
#17
Zhongliang Zu, Hua Li, Junzhong Xu, Xiao-Yong Zhang, Moritz Zaiss, Ke Li, Mark D Does, John C Gore, Daniel F Gochberg
The goal is to develop an imaging method where contrast reflects amide-water magnetization exchange, with minimal signal contributions from other sources. Conventional chemical exchange saturation transfer (CEST) imaging of amides (often called amide proton transfer, or APT, and quantified by the metric MTRasym) is confounded by several factors unrelated to amides, such as aliphatic protons, water relaxation, and macromolecular magnetization transfer. In this work, we examined the effects of combining our previous chemical exchange rotation (CERT) approach with the non-linear AREX method while using different duty cycles (DC) for the label and reference scans...
May 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28474409/amide-proton-transfer-cest-of-the-cervical-spinal-cord-in-multiple-sclerosis-patients-at-3t
#18
Samantha By, Robert L Barry, Alex K Smith, Bailey D Lyttle, Bailey A Box, Francesca R Bagnato, Siddharama Pawate, Seth A Smith
PURPOSE: The ability to evaluate pathological changes in the spinal cord in multiple sclerosis (MS) is limited because T1 - and T2 -w MRI imaging are not sensitive to biochemical changes in vivo. Amide proton transfer (APT) chemical exchange saturation transfer (CEST) can indirectly detect amide protons associated with proteins and peptides, potentially providing more pathological specificity. Here, we implement APT CEST in the cervical spinal cord of healthy and MS cohorts at 3T. METHODS: APT CEST of the cervical spinal cord was obtained in a cohort of 10 controls and 10 MS patients using a novel respiratory correction methodology...
May 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28455264/using-functional-and-molecular-mri-techniques-to-detect-neuroinflammation-and-neuroprotection-after-traumatic-brain-injury
#19
Wenzhu Wang, Hong Zhang, Doon-Hoon Lee, Jintao Yu, Tian Cheng, Michael Hong, Shanshan Jiang, Heng Fan, Xi Huang, Jinyuan Zhou, Jian Wang
This study was designed to investigate whether functional and molecular MRI techniques are sensitive biomarkers for assessment of neuroinflammation and drug efficacy after traumatic brain injury (TBI) in rats. We subjected rats to a controlled cortical impact model and used behavioral tests, histology, and immunofluorescence to assess whether flavonoid pinocembrin provides cerebral protection and improves functional recovery. Most importantly, we used multiple noninvasive structural, functional, and molecular MRI techniques to examine whether the pinocembrin-related neuroprotection and attenuation of neuroinflammation can be detected in vivo...
April 26, 2017: Brain, Behavior, and Immunity
https://www.readbyqxmd.com/read/28453291/amide-group-directed-protonolysis-of-cyclopropane-an-approach-to-2-2-disubstituted-pyrrolidines
#20
Marija Skvorcova, Aigars Jirgensons
Regioselective protonolytic C-C bond cleavage of acylated aminomethyl cyclopropanes can be achieved using trifluoroacetic acid. The intermediate tertiary carbenium ion undergoes an intramolecular amination to give 2,2-substituted pyrrolidines. The strength of the acid and the amine substituent are important factors to achieve high regioselectivity, suggesting intramolecular proton transfer from the protonated amide function. Preliminary mechanistic studies revealed that cyclopropane cleavage proceeds with retention of configuration at the carbon to which the proton is attached...
April 28, 2017: Organic Letters
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