Journal of Magnetic Resonance, Series A最新文献

{"title":"NMR Microscopy by Strong Radiofrequency-Field Gradients with Spatial Resolution Better Than Five Micrometers","authors":"F. Humbert , B. Diter , D. Canet","doi":"10.1006/jmra.1996.0245","DOIUrl":"10.1006/jmra.1996.0245","url":null,"abstract":"","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 2","pages":"Pages 242-245"},"PeriodicalIF":0.0,"publicationDate":"1996-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0245","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90104144","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}

{"title":"Accurate Rate Constants for Chemical Exchange from Improved Weighted Linear-Least-Squares Analysis of Multiple 1D-EXSY Data","authors":"Charles L. Perrin ,&nbsp;Richard E. Engler","doi":"10.1006/jmra.1996.0234","DOIUrl":"10.1006/jmra.1996.0234","url":null,"abstract":"<div><p>The 1D-EXSY pulse sequence 90°—<em>t</em>₁—90°—<em>t</em>_m—90°—<em>t</em>₂(obs), with a minimum number of judiciously chosen<em>t</em>₁values and a series of mixing times<em>t</em>_m, can provide NMR data for measurement of site-to-site rate constants in multisite systems undergoing chemical exchange. A condition can be specified for optimizing the choice of<em>t</em>₁values. The data are analyzed by an improved weighted linear-least-squares fitting procedure that uses matrix algebra to help evaluate the weighting factors. This method is capable of providing highly accurate rate constants and realistic error estimates, without an inordinate demand on instrument time. Three experimental applications, to E/Z methyl exchange in<em>N</em>,<em>N</em>-dimethylpropionamide, to H_E/H_Z/H_Solventproton exchange in acrylamide, and to methoxy exchange between stereoisomeric 4,6-dimethyl-2-methoxy-1,3-dioxanes and methanol, are demonstrated.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 2","pages":"Pages 188-195"},"PeriodicalIF":0.0,"publicationDate":"1996-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0234","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81253721","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}

{"title":"A Selective-Echo Method for Chemical-Shift Imaging of Two-Component Systems","authors":"Rex E. Gerald II,&nbsp;Anatoly O. Krasavin,&nbsp;Robert E. Botto","doi":"10.1006/jmra.1996.0236","DOIUrl":"10.1006/jmra.1996.0236","url":null,"abstract":"<div><p>A simple and effective method for selectively imaging either one of two chemical species in a two-component system is presented and demonstrated experimentally. The pulse sequence employed,<em>s</em>elective-<em>e</em>cho<em>c</em>hemical-<em>s</em>hift<em>i</em>maging (SECSI), is a hybrid (frequency-selective/<em>T</em>₁-contrast) technique that is executed in a short period of time, utilizes the full Boltzmann magnetization of each chemical species to form the corresponding image, and requires only hard pulses of quadrature phase. This approach provides a direct and unambiguous representation of the spatial distribution of the two chemical species. In addition, the performance characteristics and the advantages of the SECSI sequence are compared on a common basis to those of other pulse sequences.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 2","pages":"Pages 201-206"},"PeriodicalIF":0.0,"publicationDate":"1996-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0236","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86009335","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}

{"title":"Determination of Long-RangeJXHCouplings Using “Excitation-Sculpting” Gradient-Enhanced Heteronuclear Correlation Experiments","authors":"Guangzhao Xu,&nbsp;John Spencer Evans","doi":"10.1006/jmra.1996.0219","DOIUrl":"10.1006/jmra.1996.0219","url":null,"abstract":"","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 105-110"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0219","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-Resolution NMR Probe for Experiments at High Pressures","authors":"L. Ballard,&nbsp;C. Reiner,&nbsp;J. Jonas","doi":"10.1006/jmra.1996.0216","DOIUrl":"10.1006/jmra.1996.0216","url":null,"abstract":"<div><p>A 300 MHz high-resolution, high-pressure NMR probe which operates in the pressure range of 1 bar to 9 kbar at temperatures of −30 to 100°C is described. Specialized novel design features of the probe are discussed and test spectra showing resolution better than 1 Hz (&lt;3.0 × 10⁻⁹) for 8 mm samples are presented. Potential biochemical applications of this probe are illustrated by experiments dealing with the pressure-induced unfolding of hen egg white lysozyme.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 81-86"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0216","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940712","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}

{"title":"Curious Consequences of Strong Coupling in NMR Experiments Involving Selective Pulses","authors":"Johannes Huth ,&nbsp;Riqiang Fu ,&nbsp;Geoffrey Bodenhausen","doi":"10.1006/jmra.1996.0217","DOIUrl":"10.1006/jmra.1996.0217","url":null,"abstract":"<div><p>This study is concerned with the effects of applying selective pulses to systems with strong second-order scalar couplings in isotropic phase, where different transitions (<em>rs</em>) are associated with different transition matrix elements<em>F</em>⁺_{(<em>rs</em>)}. Two unusual features can be distinguished: the nutation angle (“flip angle”) depends on the matrix element of the irradiated transition (<em>rs</em>), and, in contrast to the behavior of an isolated spin-<span><math><mtext>1</mtext><mtext>2</mtext></math></span> system, the norm of the three single-transition operators [<em>I</em>^{(<em>rs</em>)}_<em>x</em>,<em>I</em>^{(<em>rs</em>)}_<em>y</em>,<em>I</em>^{(<em>rs</em>)}_<em>z</em>] associated with the fictitious spin-<span><math><mtext>1</mtext><mtext>2</mtext></math></span> space of the irradiated transition (<em>rs</em>) is generally not conserved. It is necessary to consider the single-transition operators [<em>I</em>^{(<em>rp</em>)}_<em>x</em>,<em>I</em>^{(<em>rp</em>)}_<em>y</em>,<em>I</em>^{(<em>rp</em>)}_<em>z</em>] and [<em>I</em>^{(<em>sq</em>)}_<em>x</em>,<em>I</em>^{(<em>sq</em>)}_<em>y</em>,<em>I</em>^{(<em>sq</em>)}_<em>z</em>] associated with all connected transitions (<em>rp</em>) and (<em>sq</em>) that share a common energy level<em>r</em>or<em>s</em>with the irradiated transition (<em>rs</em>). If the pulse applied to the (<em>rs</em>) transition is sufficiently selective, the transverse components<em>I</em>^{(<em>rp</em>)}_<em>x</em>,<em>I</em>^{(<em>rp</em>)}_<em>y</em>,<em>I</em>^{(<em>sq</em>)}_<em>x</em>, and<em>I</em>^{(<em>sq</em>)}_<em>y</em>, can be neglected, since their expectation values remain equal to zero after application of a selective pulse to the (<em>rs</em>) transition, but the longitudinal components<em>I</em>^{(<em>rp</em>)}_<em>z</em>and<em>I</em>^{(<em>sq</em>)}_<em>z</em>acquire nonvanishing expectation values. When the selective pulse affects several transitions simultaneously, the response varies from one transition to another, depending on the matrix elements and the connectivities. These effects manifest themselves in unusual amplitudes and phases of signals excited by selective pulses, in particular in selective two-dimensional correlation spectra.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 87-94"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0217","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940713","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}

{"title":"The Tolerance toJMismatch and the Symmetry Properties of INADEQUATE CR","authors":"Niels Chr. Nielsen ,&nbsp;Ole Winneche SØrensen","doi":"10.1006/jmra.1996.0226","DOIUrl":"10.1006/jmra.1996.0226","url":null,"abstract":"","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 135-139"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0226","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940722","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}

{"title":"A Study of Solvation-Shell Symmetry in Electrolyte Solutions Using Quadrupolar NMR Relaxation of the Nuclei of Monoatomic Ions","authors":"V.I. Chizhik,&nbsp;I.S. Podkorytov,&nbsp;A.P. Kaikkonen,&nbsp;V.I. Mikhailov","doi":"10.1006/jmra.1996.0207","DOIUrl":"10.1006/jmra.1996.0207","url":null,"abstract":"<div><p>The spin–lattice relaxation rates of⁷Li,²³Na,²⁷Al,⁷¹Ga, and¹³⁹La nuclei in electrolyte solutions have been investigated as functions of the isotopic composition of the solvent. The results show that quadrupolar relaxation of the nuclei of monoatomic ions is extremely sensitive to the symmetry of the solvation shells. The data are compared to the results for the²H and¹⁷O nuclei of the solvent molecules and the¹⁴N nucleus of the nitrate anion. A semiquantitative description of the observed effects is given.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 1-6"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0207","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19941449","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}

{"title":"An Efficient Method for Calculating Powder Patterns","authors":"Samuel J. Varner ,&nbsp;Robert L. Vold ,&nbsp;Gina L. Hoatson","doi":"10.1006/jmra.1996.0215","DOIUrl":"10.1006/jmra.1996.0215","url":null,"abstract":"<div><p>A novel approach to the calculation of powder lineshapes is presented. Lineshapes from asymmetric second-rank tensor interactions are produced by summing lineshapes from symmetric tensors. This approach significantly reduces the calculation time, greatly facilitating iterative nonlinear least-squares fitting of experimental spectra. Results are reported for anisotropic¹³C NMR lineshapes of glycine, benzoic acid, and octanoic acid in a urea inclusion compound. Lineshapes from nonuniform distributions of crystallite orientations can also be calculated by using distributions of the Euler angles that define the orientation of the principal-axis system of the chemical-shielding tensor with respect to the magnetic field.</p></div>","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 72-80"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0215","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940711","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}

{"title":"Peak Power and Efficiency in Hyperbolic-Secant Decoupling","authors":"Thomas E. Skinner ,&nbsp;M.Robin Bendall","doi":"10.1006/jmra.1996.0220","DOIUrl":"10.1006/jmra.1996.0220","url":null,"abstract":"","PeriodicalId":16165,"journal":{"name":"Journal of Magnetic Resonance, Series A","volume":"123 1","pages":"Pages 111-115"},"PeriodicalIF":0.0,"publicationDate":"1996-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1006/jmra.1996.0220","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19940716","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}