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Chemical exchange saturation transfer

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https://www.readbyqxmd.com/read/28317074/probing-conformational-dynamics-in-biomolecules-via-chemical-exchange-saturation-transfer-a-primer
#1
Pramodh Valluruapalli, Ashok Sekhar, Tairan Yuwen, Lewis E Kay
Although Chemical Exchange Saturation Transfer (CEST) type NMR experiments have been used to study chemical exchange processes in molecules since the early 1960s, there has been renewed interest in the past several years in using this approach to study biomolecular conformational dynamics. The methodology is particularly powerful for the study of sparsely populated, transiently formed conformers that are recalcitrant to investigation using traditional biophysical tools, and it is complementary to relaxation dispersion and magnetization transfer experiments that have traditionally been used to study chemical exchange processes...
March 19, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28283707/evaluating-the-cartilage-adjacent-to-the-site-of-repair-surgery-with-glycosaminoglycan-specific-magnetic-resonance-imaging
#2
Ulrich Koller, Sebastian Apprich, Benjamin Schmitt, Reinhard Windhager, Siegfried Trattnig
PURPOSE: The glycosaminoglycan (GAG) chemical exchange saturation transfer (CEST) imaging method (gagCEST) makes it possible to assess and quantify the GAG concentration in human cartilage. This biochemical imaging technique facilitates detection of the loss of GAG in the course of osteoarthritis. The gagCEST technique was used to analyse the perilesional zone (PLZ) adjacent to repair tissue after cartilage repair surgery, to determine whether there are biochemical changes present in the sense of degeneration...
March 10, 2017: International Orthopaedics
https://www.readbyqxmd.com/read/28273886/quantitative-chemical-exchange-saturation-transfer-cest-mri-of-glioma-using-image-downsampling-expedited-adaptive-least-squares-ideal-fitting
#3
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
https://www.readbyqxmd.com/read/28272785/cest-imaging-of-fast-exchanging-amine-pools-with-corrections-for-competing-effects-at-9-4%C3%A2-t
#4
Xiao-Yong Zhang, Feng Wang, Hua Li, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
Chemical exchange saturation transfer (CEST) imaging of fast exchanging amine protons at 3 ppm offset from the water resonant frequency is of practical interest, but quantification of fast exchanging pools by CEST is challenging. To effectively saturate fast exchanging protons, high irradiation powers need to be applied, but these may cause significant direct water saturation as well as non-specific semi-solid magnetization transfer (MT) effects, and thus decrease the specificity of the measured signal. In addition, the CEST signal may depend on the water longitudinal relaxation time (T1w ), which likely varies between tissues and with pathology, further reducing specificity...
March 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28272761/accuracy-in-the-quantification-of-chemical-exchange-saturation-transfer-cest-and-relayed-nuclear-overhauser-enhancement-rnoe-saturation-transfer-effects
#5
Xiao-Yong Zhang, Feng Wang, Hua Li, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
Accurate quantification of chemical exchange saturation transfer (CEST) effects, including dipole-dipole mediated relayed nuclear Overhauser enhancement (rNOE) saturation transfer, is important for applications and studies of molecular concentration and transfer rate (and thereby pH or temperature). Although several quantification methods, such as Lorentzian difference (LD) analysis, multiple-pool Lorentzian fits, and the three-point method, have been extensively used in several preclinical and clinical applications, the accuracy of these methods has not been evaluated...
March 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28248966/a-magnesium-induced-triplex-pre-organizes-the-sam-ii-riboswitch
#6
Susmita Roy, Heiko Lammert, Ryan L Hayes, Bin Chen, Regan LeBlanc, T Kwaku Dayie, José N Onuchic, Karissa Y Sanbonmatsu
Our 13C- and 1H-chemical exchange saturation transfer (CEST) experiments previously revealed a dynamic exchange between partially closed and open conformations of the SAM-II riboswitch in the absence of ligand. Here, all-atom structure-based molecular simulations, with the electrostatic effects of Manning counter-ion condensation and explicit magnesium ions are employed to calculate the folding free energy landscape of the SAM-II riboswitch. We use this analysis to predict that magnesium ions remodel the landscape, shifting the equilibrium away from the extended, partially unfolded state towards a compact, pre-organized conformation that resembles the ligand-bound state...
March 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28244138/b1-inhomogeneity-mitigation-in-cest-using-parallel-transmission
#7
Desmond H Y Tse, Nuno Andre da Silva, Benedikt A Poser, N Jon Shah
PURPOSE: In order to benefit from the increased spectral bandwidth at ultrahigh field (UHF), the use of parallel transmission (pTx) to mitigate flip-angle inhomogeneity in chemical exchange saturation transfer (CEST) imaging is investigated. THEORY AND METHODS: A pTx basis pulse is homogenised by magnitude least-squares (MLS) optimization and expanded to form a frequency-selective saturation pulse for CEST. The pTx saturation pulse was simulated with a three-pool Bloch-McConnell equation to evaluate the impact of pTx on CEST contrast...
February 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28240443/heteronuclear-1d-and-2d-nmr-resonances-detected-by-chemical-exchange-saturation-transfer-to-water
#8
Ricardo P Martinho, Mihajlo Novakovic, Gregory L Olsen, Lucio Frydman
A method to detect NMR spectra from heteronuclei through the modulation that they impose on a water resonance is exemplified. The approach exploits chemical exchange saturation transfers, which can magnify the signal of labile protons through their influence on a water peak. To impose a heteronuclear modulation on water, an HMQC-type sequence was combined with the FLEX approach. 1D (15) N NMR spectra of exchanging sites could thus be detected, with about tenfold amplifications over the (15) N modulations afforded by conventionally detected HMQC NMR spectroscopy...
February 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28220538/on-bead-combinatorial-synthesis-and-imaging-of-europium-iii-based-paracest-agents-aids-in-identification-of-chemical-features-that-enhance-cest-sensitivity
#9
Jaspal Singh, Vineeta Rustagi, Shanrong Zhang, A Dean Sherry, D Gomika Udugamasooriya
The rate of water exchange between the inner-sphere of a paramagnetic ion and bulk water is an important parameter in determining the magnitude of the chemical exchange saturation transfer signal from paramagnetic CEST agents (paraCEST). This is governed by various geometric, steric, and ligand field factors created by macrocyclic ligands surrounding the paramagnetic metal ion. Our previous on-bead combinatorial studies of di-peptoid-europium(III)-DOTA-tetraamide complexes revealed that negatively charged groups in the immediate vicinity of the metal center strongly enhances the CEST signal...
February 21, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28218877/reliability-of-measurement-of-chemical-exchange-saturation-transfer-effects-for-lung-lesions
#10
Panki Kim, Ha-Kyu Jeong, Byoung Wook Choi
No abstract text is available yet for this article.
March 2017: Radiology
https://www.readbyqxmd.com/read/28192930/mitochondria-targeted-and-intracellular-biothiol-triggered-hyperpolarized-129-xe-magnetofluorescent-biosensor
#11
Qingbin Zeng, Qianni Guo, Yaping Yuan, Yuqi Yang, Bin Zhang, Lili Ren, Xiaoxiao Zhang, Qing Luo, Maili Liu, Louis-S Bouchard, Xin Zhou
Biothiols such as gluthathione (GSH), cysteine (Cys), homocysteine (Hcy), and thioredoxin (Trx) play vital roles in cellular metabolism. Various diseases are associated with abnormal cellular biothiol levels. Thus, the intracellular detection of biothiol levels could be a useful diagnostic tool. A number of methods have been developed to detect intracellular thiols, but sensitivity and specificity problems have limited their applications. To address these limitations, we have designed a new biosensor based on hyperpolarized xenon magnetic resonance detection, which can be used to detect biothiol levels noninvasively...
February 9, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28179167/mri-and-mrs-of-the-human-brain-at-magnetic-fields-of-14t-to-20t-technical-feasibility-safety-and-neuroscience-horizons
#12
Thomas F Budinger, Mark D Bird
The three goals of this paper are: 1) to evaluate the improvements in technology for increasing magnetic flux density (magnetic field) to 14T in the next few years and eventually to 20T; 2) to highlight neuroscience opportunities enabled by these advances; and, 3) to evaluate the physiological and biophysical effects associated with MRI at very high performance levels. Substantial recent advances in magnet technology including superconductor developments enable neuroscience goals that are not obtainable at contemporary magnetic fields...
February 5, 2017: NeuroImage
https://www.readbyqxmd.com/read/28150877/spectral-characteristics-of-semisolid-protons-in-human-brain-white-matter-at-7-t
#13
Xu Jiang, Peter van Gelderen, Jeff H Duyn
PURPOSE: To inform the quantification of MRI magnetization transfer contrast at high field by measuring the spectral characteristics of (1) H protons in semisolids in human brain at 7 T, while avoiding prohibitive radiofrequency (RF) tissue heating and confounding effects from chemical exchange. METHODS: Saturation-recovery type experiments were performed using brief, frequency-specific RF pulses that saturate semisolid proton magnetization. Analysis of the subsequent recovery of water proton magnetization with a two-pool model of exchange allowed the study of spectral characteristics of semisolid protons...
February 2, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28111824/on-the-transmit-field-inhomogeneity-correction-of-relaxation-compensated-amide-and-noe-cest-effects-at-7%C3%A2-t
#14
Vitaliy Khlebnikov, Johannes Windschuh, Jeroen C W Siero, Moritz Zaiss, Peter R Luijten, Dennis W J Klomp, Hans Hoogduin
High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1 inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1 correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed...
January 23, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28106110/in-vivo-detection-of-cucurbit-6-uril-a-hyperpolarized-xenon-contrast-agent-for-a-xenon-magnetic-resonance-imaging-biosensor
#15
Francis T Hane, Tao Li, Peter Smylie, Raiili M Pellizzari, Jennifer A Plata, Brenton DeBoef, Mitchell S Albert
The Hyperpolarized gas Chemical Exchange Saturation Transfer (HyperCEST) Magnetic Resonance (MR) technique has the potential to increase the sensitivity of a hyperpolarized xenon-129 MRI contrast agent. Signal enhancement is accomplished by selectively depolarizing the xenon within a cage molecule which, upon exchange, reduces the signal in the dissolved phase pool. Herein we demonstrate the in vivo detection of the cucurbit[6]uril (CB6) contrast agent within the vasculature of a living rat. Our work may be used as a stepping stone towards using the HyperCEST technique as a molecular imaging modality...
January 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28096729/advanced-mri-for-pediatric-brain-tumors-with-emphasis-on-clinical-benefits
#16
REVIEW
Hyun Woo Goo, Young-Shin Ra
Conventional anatomic brain MRI is often limited in evaluating pediatric brain tumors, the most common solid tumors and a leading cause of death in children. Advanced brain MRI techniques have great potential to improve diagnostic performance in children with brain tumors and overcome diagnostic pitfalls resulting from diverse tumor pathologies as well as nonspecific or overlapped imaging findings. Advanced MRI techniques used for evaluating pediatric brain tumors include diffusion-weighted imaging, diffusion tensor imaging, functional MRI, perfusion imaging, spectroscopy, susceptibility-weighted imaging, and chemical exchange saturation transfer imaging...
January 2017: Korean Journal of Radiology: Official Journal of the Korean Radiological Society
https://www.readbyqxmd.com/read/28096269/differentiation-between-radiation-necrosis-and-tumor-progression-using-chemical-exchange-saturation-transfer
#17
Hatef Mehrabian, Kimberly L Desmond, Hany Soliman, Arjun Sahgal, Gregory J Stanisz
PURPOSE: Stereotactic radiosurgery (SRS) is a common treatment used in patients with brain metastases and is associated with high rates of local control, however, at the risk of radiation necrosis. It is difficult to differentiate radiation necrosis from tumor progression using conventional MRI making it a major diagnostic dilemma for practitioners. This prospective study investigated whether chemical exchange saturation transfer (CEST) was able to differentiate these two conditions. MATERIALS & METHODS: Sixteen patients with brain metastases who had been previously treated with SRS were included...
January 17, 2017: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
https://www.readbyqxmd.com/read/28089939/chemical-exchange-saturation-transfer-imaging-advances-and-applications-by-michael-t-mcmahon-assaf-a-gild-jeff-w-m-bulte-and-peter-c-m-van-zijl-publisher-pan-stanford-publishing-pte-ltd-singapore
#18
https://www.readbyqxmd.com/read/28075559/one-component-supramolecular-filament-hydrogels-as-theranostic-label-free-magnetic-resonance-imaging-agents
#19
Lye Lin Lock, Yuguo Li, Xinpei Mao, Hanwei Chen, Verena Staedtke, Renyuan Bai, Wang Ma, Ran Lin, Yi Li, Guanshu Liu, Honggang Cui
Gadolinium (Gd)-based compounds and materials are the most commonly used magnetic resonance imaging (MRI) contrast agents in the clinic; however, safety concerns associated with their toxicities in the free ionic form have promoted the development of new generations of metal-free contrast agents. Here we report a supramolecular strategy to convert an FDA-approved anticancer drug, Pemetrexed (Pem), to a molecular hydrogelator with inherent chemical exchange saturation transfer (CEST) MRI signals. The rationally designed drug-peptide conjugate can spontaneously associate into filamentous assemblies under physiological conditions and consequently form theranostic supramolecular hydrogels for injectable delivery...
January 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28035783/separating-dipolar-and-chemical-exchange-magnetization-transfer-processes-in-1-h-cest
#20
Tairan Yuwen, Ashok Sekhar, Lewis E Kay
An amide (1) H-Chemical Exchange Saturation Transfer (CEST) experiment is presented for studies of conformational exchange in proteins. The approach, exploiting spin-state-selective magnetization transfer, completely suppresses undesired NOE-based dips in CEST profiles so that chemical exchange processes can be studied. The methodology is demonstrated with applications involving proteins that interconvert on the millisecond timescale between major and invisible minor states, and accurate amide (1) H chemical shifts of the minor conformer are obtained in each case...
December 30, 2016: Angewandte Chemie
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