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Amide proton transfer

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https://www.readbyqxmd.com/read/28613875/modeling-of-polarization-transfer-kinetics-in-protein-hydration-using-hyperpolarized-water
#1
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 14, 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
#2
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 3.6 ppm and guanidyl-CEST signals at 2.0 ppm 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
#3
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
#4
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)...
May 30, 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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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 25, 2017: Brain, Behavior, and Immunity
https://www.readbyqxmd.com/read/28453291/amide-group-directed-protonolysis-of-cyclopropane-an-approach-to-2-2-disubstituted-pyrrolidines
#12
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
https://www.readbyqxmd.com/read/28436068/dinitrogen-splitting-coupled-to-protonation
#13
Gleb A Silantyev, Moritz Förster, Bastian Schluschaß, Josh Abbenseth, Christian Würtele, Christian Volkmann, Max C Holthausen, Sven Schneider
The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N2 splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N-N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo-N2 -Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N-N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation...
April 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28433532/exci-cest-exploiting-pharmaceutical-excipients-as-mri-cest-contrast-agents-for-tumor-imaging
#14
Dario Livio Longo, Fatima Zzahra Moustaghfir, Alexandre Zerbo, Lorena Consolino, Annasofia Anemone, Martina Bracesco, Silvio Aime
Chemical Exchange Saturation Transfer (CEST) approach is a novel tool within magnetic resonance imaging (MRI) that allows visualization of molecules possessing exchangeable protons with water. Many molecules, employed as excipients for the formulation of finished drug products, are endowed with hydroxyl, amine or amide protons, thus can be exploitable as MRI-CEST contrast agents. Their high safety profiles allow them to be injected at very high doses. Here we investigated the MRI-CEST properties of several excipients (ascorbic acid, sucrose, N-acetyl-d-glucosamine, meglumine and 2-pyrrolidone) and tested them as tumor-detecting agents in two different murine tumor models (breast and melanoma cancers)...
April 20, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28374993/removable-backbone-modification-method-for-the-chemical-synthesis-of-membrane-proteins
#15
Jia-Bin Li, Shan Tang, Ji-Shen Zheng, Chang-Lin Tian, Lei Liu
Chemical synthesis can produce water-soluble globular proteins bearing specifically designed modifications. These synthetic molecules have been used to study the biological functions of proteins and to improve the pharmacological properties of protein drugs. However, the above advances notwithstanding, membrane proteins (MPs), which comprise 20-30% of all proteins in the proteomes of most eukaryotic cells, remain elusive with regard to chemical synthesis. This difficulty stems from the strong hydrophobic character of MPs, which can cause considerable handling issues during ligation, purification, and characterization steps...
April 4, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28374764/amide-proton-transfer-magnetic-resonance-imaging-in-detecting-intracranial-hemorrhage-at-different-stages-a-comparative-study-with-susceptibility-weighted-imaging
#16
Xiaoyue Ma, Yan Bai, Yusong Lin, Xiaohua Hong, Taiyuan Liu, Lun Ma, E Mark Haacke, Jinyuan Zhou, Jian Wang, Meiyun Wang
Amide proton transfer (APT) imaging is a noninvasive molecular magnetic resonance imaging (MRI) technique based on the chemical exchange-dependent saturation transfer mechanism. The purpose of this study was to investigate the diagnostic performance of APT MRI in detecting intracranial hemorrhage (ICH) at hyperacute, acute and subacute stages by comparing with susceptibility weighted imaging (SWI). APT MRI and SWI were performed on 33 included patients with ICH by using a 3-T MRI unit. A two-sided Mann-Whitney U test was used to detect differences in APT-weighted (APTw) and SWI signal intensities of ICH at hyperacute, acute and subacute stages...
April 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28358208/imidazole-appended-macrocyclic-complexes-of-fe-ii-co-ii-and-ni-ii-as-paracest-agents
#17
Patrick J Burns, Jordan M Cox, Janet R Morrow
The solution chemistry and solid state structures of the Co(II), Fe(II), and Ni(II) complexes of N,N'-bis(imidazole-2-ylmethyl)-4,10-diaza-15-crown-5 (HINO) are reported. The Co(II) and Ni(II) complexes of HINO are the first examples of paraCEST agents (paramagnetic chemical exchange saturation transfer) that feature exchangeable imidazole NH protons. The crystal structures of [Co(HINO)]CoCl4·H2O and [Fe(HINO)](CF3SO3)2 have the metal ions coordinated to four nitrogen and three oxygen donor atoms of the macrocyclic ligand in a distorted pentagonal bipyramidal geometry...
March 30, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28357518/longitudinal-relaxation-optimized-amide-1-h-cest-experiments-for-studying-slow-chemical-exchange-processes-in-fully-protonated-proteins
#18
Tairan Yuwen, Lewis E Kay
Chemical Exchange Saturation Transfer (CEST) experiments are increasingly used to study slow timescale exchange processes in biomolecules. Although (15)N- and (13)C-CEST have been the approaches of choice, the development of spin state selective (1)H-CEST pulse sequences that separate the effects of chemical and dipolar exchange [T. Yuwen, A. Sekhar and L. E. Kay, Angew Chem Int Ed Engl 2016 doi: 10.1002/anie.201610759 (Yuwen et al. 2017)] significantly increases the utility of (1)H-based experiments. Pulse schemes have been described previously for studies of highly deuterated proteins...
March 29, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28303115/evolution-of-cerebral-ischemia-assessed-by-amide-proton-transfer-weighted-mri
#19
Guodong Song, Chunmei Li, Xiaojie Luo, Xuna Zhao, Shuai Zhang, Yi Zhang, Shanshan Jiang, Xianlong Wang, Yuhui Chen, Haibo Chen, Tao Gong, Jinyuan Zhou, Min Chen
Amide proton transfer-weighted (APTW) magnetic resonance imaging (MRI) has recently become a potentially important tool for evaluating acidosis in ischemic stroke. The purpose of this study was to evaluate the dynamic pH-related changes in the lesions in patients with ischemia. Thirty-nine patients with ischemic stroke (symptom onset to imaging time ranging 2 h-7 days) were examined with a 3.0-T MRI system. Patients were divided into four groups: at the hyperacute stage (onset time ≤ 6 h), at the acute stage (6 h < onset time ≤ 48 h), at the early subacute stage (48 h < onset time ≤ 96 h), and at the late subacute stage (96 h < onset time ≤ 168 h)...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/28273886/quantitative-chemical-exchange-saturation-transfer-cest-mri-of-glioma-using-image-downsampling-expedited-adaptive-least-squares-ideal-fitting
#20
Iris Yuwen Zhou, Enfeng Wang, Jerry S Cheung, Xiaoan Zhang, Giulia Fulci, Phillip Zhe Sun
Chemical Exchange Saturation Transfer (CEST) MRI is sensitive to dilute metabolites with exchangeable protons, allowing tissue characterization in diseases such as acute stroke and tumor. CEST quantification using multi-pool Lorentzian fitting is challenging due to its strong dependence on image signal-to-noise ratio (SNR), initial values and boundaries. Herein we proposed an Image Downsampling Expedited Adaptive Least-squares (IDEAL) fitting algorithm that quantifies CEST images based on initial values from multi-pool Lorentzian fitting of iteratively less downsampled images until the original resolution...
December 2017: Scientific Reports
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