scholarly journals Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled <i>R</i><sub>1<i>ρ</i></sub> accordion experiments

2021 ◽  
Vol 2 (2) ◽  
pp. 571-587
Author(s):  
Sven Wernersson ◽  
Göran Carlström ◽  
Andreas Jakobsson ◽  
Mikael Akke
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Mode Analysis ◽  
Parameter Estimates ◽  
Successful Implementation ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Relaxation Experiment ◽  
Indirect Evolution ◽  
Relaxation Experiments

Abstract. Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically requires significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the “relaxation dimension” into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by non-uniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successful implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér–Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS R1ρ relaxation experiment achieves comparable precision in the parameter estimates compared to conventional CPMG (Carr–Purcell–Meiboom–Gill) R2 or spin-lock R1ρ experiments while saving an order of magnitude in experiment time.

scholarly journals Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled R<sub>1ρ</sub> accordion experiments

2021 ◽  
Author(s):  
Sven Wernersson ◽  
Göran Carlström ◽  
Andreas Jakobsson ◽  
Mikael Akke
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Mode Analysis ◽  
Parameter Estimates ◽  
Reconstruction Algorithms ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Relaxation Experiment ◽  
Indirect Evolution ◽  
Relaxation Experiments

Abstract. Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically require significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the 'relaxation dimension' into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by nonuniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successfully implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér-Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS R1ρ relaxation experiment achieves comparable precision in the parameter estimates, compared to conventional CPMG R2 or spin-lock R1ρ experiments, while saving an order of magnitude in experiment time.

scholarly journals In Vivo Quantification of Cerebral R2*-Response to Graded Hyperoxia at 3 Tesla

2015 ◽  
Vol 5 ◽  
pp. 1 ◽  
Author(s):  
Grigorios Gotzamanis ◽  
Roman Kocian ◽  
Pinar S. Özbay ◽  
Manuel Redle ◽  
Spyridon Kollias ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Relaxation Rate ◽  
Tumor Therapy ◽  
Cerebrovascular Reactivity ◽  
Oxygen Intake ◽  
Transverse Relaxation Rate ◽  
Dependent Manner ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Arterial Blood

Objectives: This study aims to quantify the response of the transverse relaxation rate of the magnetic resonance (MR) signal of the cerebral tissue in healthy volunteers to the administration of air with step-wise increasing percentage of oxygen. Materials and Methods: The transverse relaxation rate (R2*) of the MR signal was quantified in seven volunteers under respiratory intake of normobaric gas mixtures containing 21, 50, 75, and 100% oxygen, respectively. End-tidal breath composition, arterial blood saturation (SaO2), and heart pulse rate were monitored during the challenge. R2* maps were computed from multi-echo, gradient-echo magnetic resonance imaging (MRI) data, acquired at 3.0T. The average values in the segmented white matter (WM) and gray matter (GM) were tested by the analysis of variance (ANOVA), with Bonferroni post-hoc correction. The GM R2*-reactivity to hyperoxia was modeled using the Hill's equation. Results: Graded hyperoxia resulted in a progressive and significant (P < 0.05) decrease of the R2* in GM. Under normoxia the GM-R2* was 17.2 ± 1.1 s-1. At 75% O2 supply, the R2* had reached a saturation level, with 16.4 ± 0.7 s-1 (P = 0.02), without a significant further decrease for 100% O2. The R2*-response of GM correlated positively with CO2 partial pressure (R = 0.69 ± 0.19) and negatively with SaO2 (R = -0.74 ± 0.17). The WM showed a similar progressive, but non-significant, decrease in the relaxation rates, with an increase in oxygen intake (P = 0.055). The Hill's model predicted a maximum R2* response of the GM, of 3.5%, with half the maximum at 68% oxygen concentration. Conclusions: The GM-R2* responds to hyperoxia in a concentration-dependent manner, suggesting that monitoring and modeling of the R2*-response may provide new oxygenation biomarkers for tumor therapy or assessment of cerebrovascular reactivity in patients.

scholarly journals A nuclear magnetic resonance study of water in aggrecan solutions

2016 ◽  
Vol 3 (3) ◽  
pp. 150705 ◽  
Author(s):  
Richard J. Foster ◽  
Robin A. Damion ◽  
Thomas G. Baboolal ◽  
Stephen W. Smye ◽  
Michael E. Ries
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Rate ◽  
Activation Energies ◽  
Proton Nuclear Magnetic Resonance ◽  
Water Molecules ◽  
Transverse Relaxation Rate ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Nuclear Magnetic

Aggrecan, a highly charged macromolecule found in articular cartilage, was investigated in aqueous salt solutions with proton nuclear magnetic resonance. The longitudinal and transverse relaxation rates were determined at two different field strengths, 9.4 T and 0.5 T, for a range of temperatures and aggrecan concentrations. The diffusion coefficients of the water molecules were also measured as a function of temperature and aggrecan concentration, using a pulsed field gradient technique at 9.4 T. Assuming an Arrhenius relationship, the activation energies for the various relaxation processes and the translational motion of the water molecules were determined from temperature dependencies as a function of aggrecan concentration in the range 0–5.3% w/w. The longitudinal relaxation rate and inverse diffusion coefficient were approximately equally dependent on concentration and only increased by upto 20% from that of the salt solution. The transverse relaxation rate at high field demonstrated greatest concentration dependence, changing by an order of magnitude across the concentration range examined. We attribute this primarily to chemical exchange. Activation energies appeared to be approximately independent of aggrecan concentration, except for that of the low-field transverse relaxation rate, which decreased with concentration.

Multinuclear NMR study of the pH dependent water state in skim milk and caseinate solutions

1993 ◽  
Vol 60 (2) ◽  
pp. 175-188 ◽  
Author(s):  
François Mariette ◽  
Charles Tellier ◽  
Gerard Brule ◽  
Philippe Marchal
Keyword(s):  
Relaxation Rate ◽  
Skim Milk ◽  
Proton Exchange ◽  
Proton Relaxation ◽  
Transverse Relaxation Rate ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Continuous Increase ◽  
Nmr Study ◽  
Ph Dependent

SummaryThe effects of decreasing pH and micellar calcium concentrations of reconstituted skim milk and caseinate solution were studied by 1H and 17O NMR spectroscopy. The proton transverse relaxation rate 1/T2 of skim milk decreased as the pH decreased, reaching a minimum at pH 5·3. However, as the pH fell sodium caseinate solution showed a continuous increase in 1/T2, with no minimum. Analysis of proton relaxation as a function of the interpulse time in the CPMG (Carr-Purcell-Meiboom-Gill) sequence demonstrated that both the proton exchange mechanism and ‘bound’ water contributed to proton relaxation in skim milk. The study of 17O relaxation rate as a function of pH confirmed the change in protein hydration upon acidification. Increasing the amount of EDTA showed that the proton transverse relaxation rate of skim milk decreased until a plateau was reached when the micellar calcium was totally solubilized. With excess EDTA the relaxation rates of skim milk and caseinate solution were identical. A strong correlation was also found between the pH dependent relaxation rate and the solubilization of micellar phosphorus as detected by 31P NMR. Together, these results suggested that aggregation of caseins by calcium and colloidal calcium phosphate is mainly responsible for the excess hydration in skim milk micelles.

Rotational‐ and vibrational‐state dependence of transverse relaxation rate constants of OCS

1985 ◽  
Vol 82 (7) ◽  
pp. 3127-3131 ◽  
Author(s):  
Yukari Matsuo ◽  
Tatsuya Minowa ◽  
Haruko Komatsu ◽  
Tadao Shimizu
Keyword(s):  
Relaxation Rate ◽  
Rate Constants ◽  
Vibrational State ◽  
State Dependence ◽  
Transverse Relaxation Rate ◽  
Transverse Relaxation

Proton magnetic relaxation of water sorbed by methaemoglobin crystals

1973 ◽  
Vol 331 (1587) ◽  
pp. 457-468 ◽  
Keyword(s):  
Relaxation Rate ◽  
Relaxation Times ◽  
Transverse Relaxation Rate ◽  
Ferric Ions ◽  
Transverse Relaxation ◽  
Water Binding ◽  
Adsorption Sites ◽  
Protein Molecules ◽  
Proton Magnetic Relaxation ◽  
Limiting Value

P. m. r. relaxation times ( T 1 and T 2 ) have been measured as a function of regain and temperature for water sorbed by lyophilized methaemoglobin. The purpose of the work was to gain information regarding the nature and extent of water binding by the protein molecules. The T 1 results are interpreted in terms of an exchange between the sixth ligand position of the Fe (III) and other adsorption sites on the protein. At high temperatures the relaxation rate at a given regain reaches a limiting value which allows the fraction of ferric ions hydrated to be calculated. Above 16% regain all the Fe (III) is hydrated. At 21 and 35% regains a maximum appears in the relaxation rate at about -46 °C indicating a contribution from a more mobile phase which produces a T 1 minimum at that temperature. The T 2 data are consistent with a model in which the main contribution to the transverse relaxation rate comes from a tightly bound fraction of the water with ω 0 Ƭ c ≫1. The temperature dependence of T 2 exhibits three different regions: ( a ) a low temperature region where lg T 2 ∝ T -1 ; ( b ) an intermediate region with a steeper increase of T 2 with temperature; and ( c ) a high temperature where T 2 levels off.

scholarly journals Apparent transverse relaxation rate in human brain varies linearly with tissue iron concentration at 4.7 T

2007 ◽  
Vol 58 (5) ◽  
pp. 1054-1060 ◽  
Author(s):  
Fumiyuki Mitsumori ◽  
Hidehiro Watanabe ◽  
Nobuhiro Takaya ◽  
Michael Garwood
Keyword(s):  
Human Brain ◽  
Relaxation Rate ◽  
Iron Concentration ◽  
Transverse Relaxation Rate ◽  
Transverse Relaxation ◽  
Tissue Iron

NUCLEAR RELAXATION RATES, PENETRATION DEPTH, AND ENERGY-DEPENDENT GAP FUNCTIONS IN HIGH-Tc SUPERCONDUCTORS

1992 ◽  
Vol 06 (18) ◽  
pp. 1145-1150 ◽  
Author(s):  
Q. P. LI ◽  
ROBERT JOYNT
Keyword(s):  
Penetration Depth ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
High Temperature Superconductors ◽  
Gap Function ◽  
Gap Functions ◽  
Nuclear Spin Relaxation ◽  
Relaxation Rates ◽  
Relaxation Experiments ◽  
Energy Dependent

We study the experimental consequences of a gap function which is odd in energy. This type of gap may occur in high temperature superconductors. We show that nuclear spin relaxation experiments can be used to probe the "particle-hole parity" of a gap function. We find that an exponent α=1/3 which characterizes the energy dependence is in agreement with the currently available experimental data of both the nuclear spin relaxation rate (∝T(2-α)/α) and the electromagnetic penetration depth (∝T(1-α)/α).

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