Journal of Magnetic Resonance, Series B最新文献_第10页

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0101

引用次数: 0

Oxygen-Centered Spin Adducts of 5,5-Dimethyl-1-pyrrolineN-oxide (DMPO) and 2H-Imidazole 1-Oxides 5,5-二甲基-1-吡咯胺-氧化物(DMPO)和2h -咪唑1-氧化物的氧中心自旋加合物

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0093

Arkadi G. Krainev , Todd D. Williams , Diana J. Bigelow

{"title":"Oxygen-Centered Spin Adducts of 5,5-Dimethyl-1-pyrrolineN-oxide (DMPO) and 2H-Imidazole 1-Oxides","authors":"Arkadi G. Krainev , Todd D. Williams , Diana J. Bigelow","doi":"10.1006/jmrb.1996.0093","DOIUrl":"10.1006/jmrb.1996.0093","url":null,"abstract":"<div>The hydroxyl and some alkoxyl spin adducts of 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) are difficult to assign due to the remarkable similarity of their EPR spectra. The utility of resolving superhyperfine (SHF) structure followed by computer simulations has been demonstrated to assist in the assignment of EPR spectra with close values of hyperfine splitting constants, e.g., DMPO/·OH and DMPO/·OR. Here,·OR is the alkoxyl radical derived from thermal decomposition of 2,2′-azobis (2-amidinopropane) hydrochloride (AAPH). In addition, two other spin traps, derivatives of 2H-imidazole 1-oxide, namely, 2,2,4-trimethyl-2H-imidazole 1-oxide (TMIO) and 2,2-dimethyl-4-phenyl-2H-imidazole 1-oxide (DMPIO), have been used in a model study to develop a procedure for distinguishing between oxygen-centered spin adducts. These results are compared with those for DMPO. TMIO and DMPIO spin traps provide more distinguishable individual spectra with·OH and AAPH-derived·OR radicals than the DMPO spin trap. The formation of DMPO/·OR(AAPH) and DMPIO/·OR(AAPH) spin adducts was confirmed by mass spectrometry. The comparison of spin trapping by DMPO and 2H-imidazole 1-oxides using typical biological sources of other oxygen-centered radicals reveals application limits of these spin traps. For example, 2H-imidazole 1-oxides do not form superoxide spin adducts in the xanthine/xanthine oxidase system. Also, for the first time, experimental evidence is presented for SHF structure in spectra of TMIO and DMPIO spin adducts with·OH/·OD and·CH3/·CD3radical species.</div>","PeriodicalId":16130,"journal":{"name":"Journal of Magnetic Resonance, Series B","volume":"111 3","pages":"Pages 272-280"},"PeriodicalIF":0.0,"publicationDate":"1996-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmrb.1996.0093","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19638168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 23

Temporal Dynamics of Hyperpolarized129Xe Resonances in Living Rats 活体大鼠超极化129xe共振的时间动力学

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0098

Kuniyoshi Sakai , Anastacia M. Bilek , Eduardo Oteiza , Ronald L. Walsworth , Dilip Balamore , Ferenc A. Jolesz , Mitchell S. Albert

引用次数: 108

Simulations and Demonstrations of Localized Tagging Experiments 局部标记实验的模拟与演示

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0095

Sudeep Chandra , Yihong Yang

引用次数: 8

Separation of NOEs from Degenerate Amide Protons in13C/15N-Labeled Proteins Using a 3D13C′-Edited NOESY-H(N)CO Experiment 用3D13C ' -编辑noesi - h (N)CO实验分离13c / 15n标记蛋白中简并酰胺质子中的NOEs

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0099

Weixing Zhang, Thomas E. Smithgall, William H. Gmeiner

引用次数: 7

17O NMR Studies of the Solvation State of cis/trans Isomers of Amides and Model Protected Peptides 酰胺和模型保护肽顺/反式异构体溶剂化状态的核磁共振研究

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0087

Ioannis P. Gerothanassis , Constantina Vakka , Anastasios Troganis

{"title":"17O NMR Studies of the Solvation State of cis/trans Isomers of Amides and Model Protected Peptides","authors":"Ioannis P. Gerothanassis , Constantina Vakka , Anastasios Troganis","doi":"10.1006/jmrb.1996.0087","DOIUrl":"10.1006/jmrb.1996.0087","url":null,"abstract":"<div>17O shielding constants have been utilized to investigate solvation differences of the cis/trans isomers ofN-methylformamide (NMF),N-ethylformamide (NEF), andtert-butylformamide (TBF) in a variety of solvents with particular emphasis on aqueous solution. Comparisons are also made with protected peptides of the formulas CH3CO–YOH, CH3CO–Y–NHR (Y = Pro, Sar), and CH3CO–Y–Z–NHR (Y = Pro; Z =D-Ala) selectively enriched in17O at the acetyl oxygen atom. Hydration at the amide oxygen induces large and specific modifications of the17O shielding constants, which are practically the same for the cis and trans isomers of NMF, NEF, and the protected peptides. Fortert-butylformamide, the strong deshielding of the trans isomer compared to that of the cis isomer may be attributed to an out-of-plane (torsion-angle) deformation of the amide bond and/or a significant reduction of solvation of the trans isomer due to steric inhibition of the bulkytert-butyl group. Good linear correlation between δ(17O) of amides and δ(17O) of acetone was found for different solvents which have varying dielectric constants and solvation abilities. Sum-over-states calculations, within the solvaton model, underestimate effects of the dielectric constant of the medium on17O shielding, while finite-perturbation-theory calculations give good agreement with the experiment.</div>","PeriodicalId":16130,"journal":{"name":"Journal of Magnetic Resonance, Series B","volume":"111 3","pages":"Pages 220-229"},"PeriodicalIF":0.0,"publicationDate":"1996-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmrb.1996.0087","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19638231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Detection of Anisotropic Pulsating Flow and Its Velocity-Fluctuation Rate in Fertilized Bird Eggs by NMR Microimaging 利用核磁共振微成像技术检测鸟蛋中各向异性脉动流及其速度波动率

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0089

U. Görke, R. Kimmich, J. Weis

{"title":"Detection of Anisotropic Pulsating Flow and Its Velocity-Fluctuation Rate in Fertilized Bird Eggs by NMR Microimaging","authors":"U. Görke, R. Kimmich, J. Weis","doi":"10.1006/jmrb.1996.0089","DOIUrl":"10.1006/jmrb.1996.0089","url":null,"abstract":"<div>Coherent and incoherent flows in fertilized quail and bantam eggs have been studied with the aid of NMR microimaging techniques in the course of incubation until the end of the sixth day. The methods employed were multiplane tagging NMR imaging and a NMR gradient-echo imaging pulse sequence supplemented by bipolar gradient pulses in the coherence-evolution interval. The latter technique is suited for recording of velocity maps as well as for localizing of regions with enhanced echo attenuation by incoherent motions. Slight coherent displacements in the middle of the upper part of the egg white were found after the fourth day of incubation with the aid of both pulse schemes. The maximum velocity was estimated to be 1 mm/s. More pronounced effects revealed themselves in the examination of incoherent motions. After the same time of incubation and in a somewhat more restricted area of the upper part of the egg white, distinct motions could be localized consistently with either technique. It is shown that these motions are directed to and from the yolk. Furthermore, the analysis of the time fluctuations of the local signals with the aid of a Fourier transformation showed that the flow is largely of a pulsating nature. The pulsation frequency was found to be 0.4 Hz.</div>","PeriodicalId":16130,"journal":{"name":"Journal of Magnetic Resonance, Series B","volume":"111 3","pages":"Pages 236-242"},"PeriodicalIF":0.0,"publicationDate":"1996-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmrb.1996.0089","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19638233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Water Self-Diffusion Measurements in Excised Rat Lungs 水在切除大鼠肺中的自扩散测量

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0090

G. Laicher , D.C. Ailion , A.G. Cutillo

{"title":"Water Self-Diffusion Measurements in Excised Rat Lungs","authors":"G. Laicher , D.C. Ailion , A.G. Cutillo","doi":"10.1006/jmrb.1996.0090","DOIUrl":"10.1006/jmrb.1996.0090","url":null,"abstract":"<div>Water self diffusion in excised rat lungs has been measured using pulsed-field-gradient (PFG) techniques. The apparent diffusion coefficient,Dapp, was measured from a plot of the magnetizationMvsg2ato be 4.0 × 10−6cm2/s in the limit of small γδga, where γ is the gyromagnetic ratio, δ is the duration of the applied gradient pulses, andgais the applied gradient strength.Dappis independent of the diffusion time,t, for values oftbetween 18 and 106 ms. For larger values of γδga, an additional smaller value of the slope ofMvsg2awas observed, indicating the existence of other, more slowly dephasing spins. Variation oftrevealed that the relative magnetization associated with the more slowly dephasing spins decreases astis increased. In addition, the relative magnetization of the slowly dephasing spins decreases as the temperature,T, of the excised rat lung is increased. Slow exchange from the compartment of the more rapidly to that of the more slowly dephasing spins may explain some of the observed dependence of the relative magnetizations ontandT. Measurements of water self diffusion in rat lung at various levels of water content indicate a correlation betweenT2components and diffusion components. A new technique that combines the PFG with the Carr–Purcell–Meiboom–Gill technique is presented. The application of this technique to excised rat lung confirms the correlation betweenT2and diffusion components.</div>","PeriodicalId":16130,"journal":{"name":"Journal of Magnetic Resonance, Series B","volume":"111 3","pages":"Pages 243-253"},"PeriodicalIF":0.0,"publicationDate":"1996-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmrb.1996.0090","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19638234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

The Spin Dynamics of Heteronuclear Multiple-Spin Systems Formulated in the Extended Strong-Narrowing Limit 扩展强窄极限下异核多自旋系统的自旋动力学

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0092

Leiming Zhu

{"title":"The Spin Dynamics of Heteronuclear Multiple-Spin Systems Formulated in the Extended Strong-Narrowing Limit","authors":"Leiming Zhu","doi":"10.1006/jmrb.1996.0092","DOIUrl":"10.1006/jmrb.1996.0092","url":null,"abstract":"<div>Employing the perturbation approach directly in the multiply rotating frame, the master equation governing the spin dynamics of scalar-coupled heteronuclear multiple-spin systems has been derived. The resulting equation for the spin-density operator and the matrix form of the relaxation superoperator are relatively simple under the conditions of the “extended” strong-narrowing limit. The extended strong-narrowing limit, which requires that ωIiτc<< 1 and 2πJijτc<< 1 [where I represents one of the spin types in the heteronuclear spin system, ωIiis the chemical-shift range of spin type I in radians per second,Jijis the coupling constantJbetween spiniand spinj(like or unlike) in hertz, and τcis the correlation time in seconds per radian], can be applied to heteronuclear spin systems of both small molecules and biopolymers in high-resolution liquid NMR. This newly developed formalism is used to investigate the effect of transverse cross relaxation on the apparent coupling constants in a heteronuclear1H–1H–13C three-spin system. The calculation shows that, despite the strong dipolar interaction between directly bonded1H and13C, this perturbation on the apparent couplings is trivial. This result is in contrast to the homonuclear proton spin system, where the scalar coupling constants between two protons are significantly modulated if one proton is strongly dipole coupled to another proton. The underlying physical reasons for the different behavior of heteronuclear and homonuclear systems are explained.</div>","PeriodicalId":16130,"journal":{"name":"Journal of Magnetic Resonance, Series B","volume":"111 3","pages":"Pages 262-271"},"PeriodicalIF":0.0,"publicationDate":"1996-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmrb.1996.0092","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19638236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Author Index for Volume 111 第111卷作者索引

Journal of Magnetic Resonance, Series B Pub Date : 1996-06-01 DOI: 10.1006/jmrb.1996.0102

引用次数: 0