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Chemical exchange saturation transfer

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https://www.readbyqxmd.com/read/29345807/targeting-a-dark-excited-state-of-hiv-1-nucleocapsid-by-anti-retroviral-thioesters-revealed-by-nmr
#1
Lalit Deshmukh, Vitali Tugarinov, Daniel H Appella, G Marius Clore
HIV-1 nucleocapsid (NCp7) is a two Cys2HisCys zinc knuckle (N-Zn and C-Zn) protein that plays a key role in viral replication. Here we characterize NCp7 conformational dynamics by NMR relaxation dispersion and chemical exchange saturation transfer measurements. While the N-Zn knuckle is conformationally stable, the C-Zn knuckle interconverts on the millisecond time scale between the major state, in which the zinc is coordinated by three cysteines and a histidine, and two folded minor species (with populations around 1%) in which one of the coordination bonds (Cys413-S---Zn or His421-N2---Zn) is hydrolysed...
January 18, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29341020/mri-in-the-study-of-animal-models-of-stroke
#2
Pedro Ramos-Cabrer, Daniel Padro
Stroke consists of the loss of cerebral functions resulting from the interruption of blood supply to a region of the brain, and represents the second cause of death and the leading cause of major disability in adults in Europe. Stroke is a very active field of research at preclinical and clinical levels, and Magnetic Resonance Imaging (MRI) is one of the most powerful tools that scientist and clinicians have for the study of the onset, evolution and consequences of this devastating disease, as well as for the monitoring of the success of available treatments, or for the development of novel therapeutic strategies...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29336150/chemical-exchange-saturation-transfer-in-chemical-reactions-a-mechanistic-tool-for-nmr-detection-and-characterization-of-transient-intermediates
#3
N Lokesh, Andreas Seegerer, Johnny Hioe, Ruth M Gschwind
The low sensitivity of NMR and transient key intermediates below detection limit are the central problems studying reaction mechanisms by NMR. Sensitivity can be enhanced by hyperpolarization techniques such as dynamic nuclear polarization or the incorporation/interaction of special hyperpolarized molecules. However, all of these techniques require special equipment, are restricted to selective reactions or undesirably influence the reaction pathways. Here, we apply the Chemical Exchange Saturation Transfer (CEST) technique for the first time to NMR detect and characterize previously unobserved transient reaction intermediates in organocatalysis...
January 16, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29330386/on-the-detection-of-cerebral-metabolic-depression-in-experimental-traumatic-brain-injury-using-chemical-exchange-saturation-transfer-cest-weighted-mri
#4
Tsang-Wei Tu, Wael G Ibrahim, Neekita Jikaria, Jeeva P Munasinghe, Jaclyn A Witko, Dima A Hammoud, Joseph A Frank
Metabolic abnormalities are commonly observed in traumatic brain injury (TBI) patients exhibiting long-term neurological deficits. This study investigated the feasibility and reproducibility of using chemical exchange saturation transfer (CEST) MRI to detect cerebral metabolic depression in experimental TBI. Phantom and in vivo CEST experiments were conducted at 9.4 Tesla to optimize the selective saturation for enhancing the endogenous contrast-weighting of the proton exchanges over the range of glucose proton chemical shifts (glucoCEST) in the resting rat brain...
January 12, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29322559/cest-dixon-for-human-breast-lesion-characterization-at-3-t-a-preliminary-study
#5
Shu Zhang, Stephen Seiler, Xinzeng Wang, Ananth J Madhuranthakam, Jochen Keupp, Emily E Knippa, Robert E Lenkinski, Elena Vinogradov
PURPOSE: Chemical exchange saturation transfer (CEST) MRI for breast lesion characterization is promising. However, artifacts are prone to develop in breast CEST imaging as a result of strong lipid signals. The aims of the study are (i) to develop and validate the CEST-Dixon imaging sequence for simultaneous water-fat separation and B0 mapping; and (ii) use the CEST-Dixon method to characterize suspicious lesions in patients undergoing percutaneous biopsy. METHODS: The gradient-echo multi-echo Dixon acquisition is used to create fat-free CEST and B0 maps...
January 10, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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/29276882/deciphering-the-dynamic-interaction-profile-of-an-intrinsically-disordered-protein-by-nmr-exchange-spectroscopy
#7
Elise Delaforge, Jaka Kragelj, Laura Tengo, Andrés Palencia, Sigrid Milles, Guillaume Bouvignies, Nicola Salvi, Martin Blackledge, Malene Ringkjøbing Jensen
Intrinsically disordered proteins (IDPs) display a large number of interaction modes including folding-upon-binding, binding without major structural transitions or binding through highly dynamic, so-called fuzzy, complexes. The vast majority of experimental information about IDP binding modes have been inferred from crystal structures of proteins in complex with short peptides of IDPs. However, crystal structures provide a mainly static view of the complexes and do not give information about the conformational dynamics experienced by the IDP in the bound state...
December 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29193448/increased-cest-specificity-for-amide-and-fast-exchanging-amine-protons-using-exchange-dependent-relaxation-rate
#8
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/29193288/characterization-of-tumor-vascular-permeability-using-natural-dextrans-and-cest-mri
#9
Yuguo Li, Yuan Qiao, Hanwei Chen, Renyuan Bai, Verena Staedtke, Zheng Han, Jiadi Xu, Kannie W Y Chan, Nirbhay Yadav, Jeff W M Bulte, Shibin Zhou, Peter C M van Zijl, Guanshu Liu
PURPOSE: To investigate the use of natural dextrans as nano-sized chemical exchange saturation transfer (CEST) MRI probes for characterizing size-dependent tumor vascular permeability. METHODS: Dextrans of different molecular weight (10, 70, 150, and 2000 kD) were characterized for their CEST contrast. Mice (N = 5) bearing CT26 subcutaneous colon tumors were injected intravenously with 10 kD (D10, 6 nm) and 70 kD (D70, 12 nm) dextran at a dose of 375 mg/kg...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29191206/optimized-cest-cardiovascular-magnetic-resonance-for-assessment-of-metabolic-activity-in-the-heart
#10
Zhengwei Zhou, Christopher Nguyen, Yuhua Chen, Jaime L Shaw, Zixin Deng, Yibin Xie, James Dawkins, Eduardo Marbán, Debiao Li
BACKGROUND: Previous studies have linked cardiac dysfunction to loss of metabolites in the creatine kinase system. Chemical exchange saturation transfer (CEST) is a promising metabolic cardiovascular magnetic resonance (CMR) imaging technique and has been applied in the heart for creatine mapping. However, current limitations include: (a) long scan time, (b) residual cardiac and respiratory motion, and (c) B0 field variations induced by respiratory motion. An improved CEST CMR technique was developed to address these problems...
November 30, 2017: Journal of Cardiovascular Magnetic Resonance
https://www.readbyqxmd.com/read/29189927/solvent-saturation-transfer-to-proteins-sstp-for-structural-and-functional-characterization-of-proteins
#11
Pushpa Mishra, C Ashley Barnes, Madeleine Strickland, Nico Tjandra
Protein structure determination using NMR is dependent on experimentally acquired distance restraints. Often, however, an insufficient number of these restraints are available for determining a protein's correct fold, much less its detailed three-dimensional structure. In consideration of this problem, we propose a simple means to acquire supplemental structural restraints from protein surface accessibilities using solvent saturation transfer to proteins (SSTP), based on the principles of paramagnetic chemical-exchange saturation transfer...
November 30, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/29171604/sensitivity-enhanced-detection-of-non-labile-proton-and-carbon-nmr-spectra-on-water-resonances
#12
Mihajlo Novakovic, Ricardo P Martinho, Gregory L Olsen, Michael S Lustig, Lucio Frydman
Chemical exchange saturation transfer (CEST) experiments enhance the NMR signals of labile protons by continuously transferring these protons' saturation to an abundant solvent pool like water. The present study expands these principles by fusing into these experiments homonuclear isotropic mixing sequences, enabling the water-enhanced detection of non-exchangeable species. Further opportunities are opened by the addition of coupling-mediated heteronuclear polarization transfers, which then impose on the water resonance a saturation stemming from non-labile heteronuclear species like (13)C...
November 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29170533/equilibrium-folding-dynamics-of-meacp-in-water-heavy-water-and-low-concentration-of-urea
#13
Yang Zhou, Daiwen Yang
Many proteins fold in apparent two-state behavior, as partially folded intermediates only transiently accumulate and easily escape detection. Besides a native form and a mainly unfolded form, we captured a partially unfolded form of an acyl carrier protein from Micromonospora echinospora (meACP) in the folding/unfolding equilibrium using chemical exchange saturation transfer NMR experiments. The C-terminal region of the partially unfolded form is mainly folded and the N-terminal is unfolded. Furthermore, to understand how the folding process of meACP is influenced by solvent environments, we compared the folding dynamics of meACP in D2O, H2O and low concentration of urea...
November 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29157492/biomolecular-mri-reporters-evolution-of-new-mechanisms
#14
REVIEW
Arnab Mukherjee, Hunter C Davis, Pradeep Ramesh, George J Lu, Mikhail G Shapiro
Magnetic resonance imaging (MRI) is a powerful technique for observing the function of specific cells and molecules inside living organisms. However, compared to optical microscopy, in which fluorescent protein reporters are available to visualize hundreds of cellular functions ranging from gene expression and chemical signaling to biomechanics, to date relatively few such reporters are available for MRI. Efforts to develop MRI-detectable biomolecules have mainly focused on proteins transporting paramagnetic metals for T1 and T2 relaxation enhancement or containing large numbers of exchangeable protons for chemical exchange saturation transfer...
November 2017: Progress in Nuclear Magnetic Resonance Spectroscopy
https://www.readbyqxmd.com/read/29154463/establishing-upper-limits-on-neuronal-activity-evoked-ph-changes-with-apt-cest-mri-at-7-t
#15
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/29149466/microsecond-timescale-protein-dynamics-a-combined-solid-state-nmr-approach
#16
Petra Rovó, Rasmus Linser
Conformational exchange in proteins is a major determinant in protein functionality. In particular, the μs-ms timescale is associated with enzymatic activity and interactions between biological molecules. We show here that a comprehensive data set of R1ρ relaxation dispersion profiles employing multiple effective fields and tilt angles can be easily obtained in perdeuterated, partly back-exchanged proteins at fast magic-angle spinning and further complemented with chemical-exchange saturation transfer NMR experiments...
November 17, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29143921/dichloroacetate-induced-intracellular-acidification-in-glioblastoma-in-vivo-detection-using-aacid-cest-mri-at-9-4%C3%A2-tesla
#17
Mohammed Albatany, Alex Li, Susan Meakin, Robert Bartha
Intracellular pH (pHi) plays an important role in the maintenance of normal cell function, and is maintained within a narrow range by the activity of transporters located at the plasma membrane. Modulation of tumor pHi may influence proliferation, apoptosis, chemotherapy resistance, and thermosensitivity. Chemical exchange saturation transfer (CEST) is a novel MRI contrast mechanism that is dependent on cellular pH. Amine and amide concentration-independent detection (AACID) is a recently developed CEST contrast method that is intracellular pH (pHi) weighted...
November 16, 2017: Journal of Neuro-oncology
https://www.readbyqxmd.com/read/29133469/an-invisible-ubiquitin-conformation-is-required-for-efficient-phosphorylation-by-pink1
#18
Christina Gladkova, Alexander F Schubert, Jane L Wagstaff, Jonathan N Pruneda, Stefan M V Freund, David Komander
The Ser/Thr protein kinase PINK1 phosphorylates the well-folded, globular protein ubiquitin (Ub) at a relatively protected site, Ser65. We previously showed that Ser65 phosphorylation results in a conformational change in which Ub adopts a dynamic equilibrium between the known, common Ub conformation and a distinct, second conformation wherein the last β-strand is retracted to extend the Ser65 loop and shorten the C-terminal tail. We show using chemical exchange saturation transfer (CEST) nuclear magnetic resonance experiments that a similar, C-terminally retracted (Ub-CR) conformation also exists at low population in wild-type Ub...
November 13, 2017: EMBO Journal
https://www.readbyqxmd.com/read/29111410/the-z-spectrum-from-human-blood-at-7t
#19
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/29067395/toward-inert-paramagnetic-ni-ii-based-chemical-exchange-saturation-transfer-mri-agents
#20
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
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