期刊文献+
共找到7篇文章
< 1 >
每页显示 20 50 100
Evaluation of Glycosaminoglycan in the Lumbar Disc Using Chemical Exchange Saturation Transfer MR at 3.0 Tesla:Reproducibility and Correlation with Disc Degeneration 被引量:8
1
作者 Deng Min Yuan Jing +3 位作者 Chen Wei Tian Queenie Chan James F Griffith Wang Yi Xiang 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2016年第1期47-55,共9页
Objective This study aims to explore the clinical applicability and relevance of giycosaminoglycan Chemical Exchange Saturation Transfer (gagCEST) for intervertebral disc. Methods 25 subjects ranging in age from 24 ... Objective This study aims to explore the clinical applicability and relevance of giycosaminoglycan Chemical Exchange Saturation Transfer (gagCEST) for intervertebral disc. Methods 25 subjects ranging in age from 24 yrs to 74 yrs were enrolled, gagCEST was acquired using a single-slice TSE sequence on a 3T. Saturation used a continuous rectangular RF pulse with B1=0.8 I^T and a fixed duration time =1100 ms. Sagittal image was obtained firstly without saturation pulse, and then saturated images were acquired at 52 offsets ranging from +0.i25 to +_7 parts per million (ppm). MR T2 relaxivity map was acquired at the identical location. Six subjects were scanned twice to assess scan-rescan reproducibility. Results GagCEST intraclass correlation coefficient (ICC) of six subjects was 0.759 for nucleus pulposus (NP) and 0.508 for annulus fibrosus (AF). Bland-Altman plots showed NP had a mean difference of 0.10% (95% limits of agreement: -3.02% to 3.22%); while that of AF was 0.34% (95% limits of agreement: -2.28% to 2.95%). For the 25 subjects, gag CEST in NP decreased as disc degeneration increased, with a similar trend to T2 relaxivity. Gag CEST of AF showed a better correlation with disc degeneration than T2 relaxivity. Conclusion GagCEST in NP and AF decreased as disc degeneration increased, while gagCEST in AF showed a better correlation than T2 relaxivity. 展开更多
关键词 GLYCOSAMINOGLYCAN chemical exchange Saturation Transfer (CEST) REPRODUCIBILITY Discdegeneration
下载PDF
Noninvasive Characterization of Metabolic Changes in Ischemic Stroke Using Z-spectrum-fitted Multiparametric Chemical Exchange Saturation Transfer-weighted Magnetic Resonance Imaging 被引量:1
2
作者 Zhen-xiong WANG Xin-hua WEI +2 位作者 Ke-jia CAI Wen-zhen ZHU Chang-liang SU 《Current Medical Science》 SCIE CAS 2023年第5期970-978,共9页
Objective This study aimed to noninvasively characterize the metabolic alterations in ischemic brain tissues using Z-spectrum-fitted multiparametric chemical exchange saturation transfer-weighted magnetic resonance im... Objective This study aimed to noninvasively characterize the metabolic alterations in ischemic brain tissues using Z-spectrum-fitted multiparametric chemical exchange saturation transfer-weighted magnetic resonance imaging(CEST-MRI).Methods Three sets of Z-spectrum data with saturation power(B_(1))values of 1.5,2.5,and 3.5µT,respectively,were acquired from 17 patients with ischemic stroke.Multiple contrasts contributing to the Z-spectrum,including fitted amide proton transfer(APT_(fitted)),+2 ppm peak(CEST@2ppm),concomitantly fitted APT_(fitted) and CEST@2ppm(APT&CEST@2ppm),semisolid magnetization transfer contrast(MT),aliphatic nuclear Overhauser effect(NOE),and direct saturation of water(DSW),were fitted with 4 and 5 Lorentzian functions,respectively.The CEST metrics were compared between ischemic lesions and contralateral normal white matter(CNWM),and the correlation between the CEST metrics and the apparent diffusion coefficient(ADC)was assessed.The differences in the Z-spectrum metrics under varied B1 values were also investigated.Results Ischemic lesions showed increased APTfitted,CEST@2ppm,APT&CEST@2ppm,NOE,and DSW as well as decreased MT.APT&CEST@2ppm,MT,and DSW showed a significant correlation with ADC[APT&CEST@2ppm at the 3 B_(1) values:R=0.584/0.467/0.551;MT at the 3 B_(1) values:R=−0.717/−0.695/−0.762(4-parameter fitting),R=−0.734/−0.711/−0.785(5-parameter fitting);DSW of 4-/5-parameter fitting:R=0.794/0.811(2.5µT),R=0.800/0.790(3.5µT)].However,the asymmetric analysis of amide proton transfer(APT_(asym))could not differentiate the lesions from CNWM and showed no correlation with ADC.Furthermore,the Z-spectrum contrasts varied with B_(1).Conclusion The Z-spectrum-fitted multiparametric CEST-MRI can comprehensively detect metabolic alterations in ischemic brain tissues. 展开更多
关键词 chemical exchange saturation transfer Z-spectrum ischemic stroke
下载PDF
Detecting water-protein chemical exchange in membrane- bound proteins/peptides by solid-state NMR spectroscopy--Dedicated to Professor Xiuwen Han on the occasion of her 80th birthday
3
作者 Rongfu Zhang Timothy A.Cross Riqiang Fu 《Magnetic Resonance Letters》 2021年第2期99-111,共13页
Water plays an important role in many essential biological processes of membrane proteins in hydrated lipid environments.In general,the 1H polarization transfers berween water molecules and site--specific protons in p... Water plays an important role in many essential biological processes of membrane proteins in hydrated lipid environments.In general,the 1H polarization transfers berween water molecules and site--specific protons in proteins can be classified as coherent(via dipolar spin diffusion)and incoherent(via chemical exchange and nuclear Overhauser effect)transfers.Solid-state NMR is the technique of choice for studying such water-protein interactions in membrane-bound proteins/peptides through the detection of'H polarization transfers from water to the proteins.These polarization transfer mechanisms often exist simultaneously and are difficult to quantify individually.Here,we review water-protein polarization transfer techniques in solid state NMR with a focus on the recent progress for the direct detection of site-specific kinetic water-protein chemical exchange processes on the sub-millisecond time scale in membrane-bound proteins.The measurements of the pure chemical exchange ki-netics provide a unique opportunity to understand the role that water plays in the structure-function relationships of membrane bound species at the water-bilayer interface.In addi-tion,the perspective of chemical exchange saturation transfer(CEST)experiments in membrane-bound proteins/peptides is further discussed. 展开更多
关键词 chemical exchange Spin diffusion HETCOR CEST Water-protein interactions Solid-state NMR
下载PDF
Kinetic characterization of a slow chemical exchange between two sites in N,N-dimethylacetylamide by CEST NMR spectroscopy
4
作者 Lixia Wang Jikun Li +2 位作者 Junfeng Xiang Jie Cui Yalin Tang 《Chinese Chemical Letters》 SCIE CAS CSCD 2022年第9期4335-4338,共4页
Nuclear magnetic resonance(NMR)spectroscopy has provided many powerful tools for the study of dynamic processes.Among the reported methods,chemical exchange saturation transfer(CEST)is more suitable for systems with s... Nuclear magnetic resonance(NMR)spectroscopy has provided many powerful tools for the study of dynamic processes.Among the reported methods,chemical exchange saturation transfer(CEST)is more suitable for systems with slow exchange rates,and there will be promising in the detection and dynamic mechanism of metastable substances.It has been widely used in magnetic resonance imaging(MRI),however whether it is applicable in the field of chemical kinetics needs more examples.Here we studied,as a proof of concept,the kinetics of the slow chemical exchange between the two N-methyl protons of N,N-dimethylacetylamide(DMA),exploiting QUantifying Exchange using Z-spectrum(QUEZS)and QUantifying Exchange using Saturation Time(QUEST)methods.It turned out that both of QUEZS and QUEST could give the corresponding exchange rates,showcasing the capability of this method to provide accurate kinetic data under a range of temperatures.Our results clearly demonstrated the reliability of CEST-based techniques as a tool for dynamic kinetics by NMR. 展开更多
关键词 chemical exchange saturation transfer(CEST) chemical exchange N N-Dimethylacetylamid Bloch-Mc Connell equation Dynamic kinetics
原文传递
The buffering effects of aquatic sediments against acidic deposition
5
作者 Liao Bohan Tang Hongxiao(Researeh Center for Eco-Environmental Sciences. Chinese Academy of Sciences, Beijing 100085, China) 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 1994年第1期21-28,共8页
The cation exchange and the chemical weathering are two important processes for sedi-ments to buffer the acidification of surface water. In this paper, for sediments these two processeshave been studied. The relations... The cation exchange and the chemical weathering are two important processes for sedi-ments to buffer the acidification of surface water. In this paper, for sediments these two processeshave been studied. The relationship between BFC of sediments and ANC of the surface waters andthe weathering characteristics of sediments were discussed. The buffering effect and mechanism of sedi-ments against acidic deposition have also been studied. The results show that BFC of sediments arepositively correlative to ANC of the surface waters. the chemical weathering rate of sediments can beexpressed as R=k×[H ̄ +] ̄m. 展开更多
关键词 acidic deposition sediment surface water cation exchange chemical weathering.
下载PDF
Label-Free Chemically and Molecularly Selective Magnetic Resonance Imaging
6
作者 Tianhe Wu Claire Liu +4 位作者 Anbu Mozhi Thamizhchelvan Candace Fleischer Xingui Peng Guanshu Liu Hui Mao 《Chemical & Biomedical Imaging》 CAS 2023年第2期121-139,共19页
Biomedical imaging,especially molecular imaging,has been a driving force in scientific discovery,technological innovation,and precision medicine in the past two decades.While substantial advances and discoveries in ch... Biomedical imaging,especially molecular imaging,has been a driving force in scientific discovery,technological innovation,and precision medicine in the past two decades.While substantial advances and discoveries in chemical biology have been made to develop molecular imaging probes and tracers,translating these exogenous agents to clinical application in precision medicine is a major challenge.Among the clinically accepted imaging modalities,magnetic resonance imaging(MRI)and magnetic resonance spectroscopy(MRS)exemplify the most effective and robust biomedical imaging tools.Both MRI and MRS enable a broad range of chemical,biological diagnosis and characterization of many diseases and image-guided interventions.Using chemical,biological,and nuclear magnetic resonance properties of specific endogenous metabolites and native MRI contrast-enhancing biomolecules,label-free molecular and cellular imaging with MRI can be achieved in biomedical research and clinical management of patients with various diseases.This review article outlines the chemical and biological bases of several label-free chemically and molecularly selective MRI and MRS methods that have been applied in imaging biomarker discovery,preclinical investigation,and image-guided clinical management.Examples are provided to demonstrate strategies for using endogenous probes to report the molecular,metabolic,physiological,and functional events and processes in living systems,including patients.Future perspectives on label-free molecular MRI and its challenges as well as potential solutions,including the use of rational design and engineered approaches to develop chemical and biological imaging probes to facilitate or combine with label-free molecular MRI,are discussed. 展开更多
关键词 Magnetic resonance imaging Magnetic resonance spectroscopy Molecular imaging LABEL-FREE Metabolic imaging chemical exchange DIFFUSION PERFUSION Imaging probe
原文传递
Theoretical investigations on the thiol–thioester exchange steps of different thioesters
7
作者 Xiao-Hui Sun Hai-Zhu Yu +1 位作者 Shu-Qi Pei Zhi-Min Dang 《Chinese Chemical Letters》 SCIE CAS CSCD 2015年第10期1259-1264,共6页
As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoreti... As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoretical calculations were carried out on the relationships between the structure of different thioesters and the free energy barriers of the thiol–thioester exchange step. According to the calculation results, the thiol–thioester exchange step is disfavored by the steric hindrance around the carbonyl center, while the electronic effect(i.e. conjugation and hyper-conjugation effects) becomes important when the steric hindrance is insignificant. 展开更多
关键词 Native chemical ligation Thiol–thioester exchange Density functional theory
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部