Proton Magnetic Relaxation Rates Research Articles

Plasma Dynamic Viscosity Determined by NMR

A nuclear magnetic resonance (NMR) based experimental procedure to determine the dynamic viscosity (η) in blood plasma solutions is presented. An equation relating η and the transverse proton magnetic relaxation rate ( $$1/T_{2}$$ ) is obtained after considering plasma an extremely diluted water solution of albumin with no long range hydrodynamics interactions among macromolecules, and a fast exchange of water molecules between the free and associated water. Carr–Purcell–Meiboom–Gill pulse sequence was used to measure the transverse proton magnetic relaxation time (T2) in a magnetic resonance console coupled to one homogeneous magnetic system (0.095 T). A η value of 1.68 ± 0.08 mPa s was obtained in 20 control samples, which statistically matched the value obtained in the same samples using an Ostwald viscometer (1.61 ± 0.04 mPa s). η was determined in 172 patients with multiple myeloma (2.47 ± 0.15 mPa s) and 72 with sickle cell disease (2.45 ± 0.24 mPa s) showing a statistically significant increase over the control individuals. The results show the utility of this NMR method to estimate dynamic viscosity in plasma for medical purposes, and a comparison with other methods is done.

Ion hydration effects in aqueous solutions of strong electrolytes, according to proton magnetic relaxation measurements

The concentration dependences of proton magnetic relaxation (PMR) rates measured at different temperatures in aqueous electrolyte solutions and concentrated seawater (SW) in a wide range of salt concentrations and for different seawater salinities are presented, along with the concentration dependences of PMR rates determined in salts dissolved directly in seawater. The coordination numbers of the basic ions in seawater were determined from the complete solvation limits and compared with those measured in single-component water-salt solutions. The attaining of complete solvation limits was determined using the PMR data for ions of different hydration signs.

Aspects of Ion Hydration. Adiabatic Compressibility Compared to the Dielectric Properties of Aqueous Electrolyte Solutions

Adiabatic compressibility data and principal dielectric relaxation times for aqueous solutions of 1:1 and 2:1 valent electrolytes are evaluated to yield their relative molal shifts Bκ and Bd, respectively, at low solute concentration. Cationic (Bx(+)) and anionic (Bx(–)) contributions to these quantities are calculated and compared to one another. For some ions also the correspondent relative molal shifts (Bm(±)) in the intramolecular proton magnetic relaxation rates are considered. Clear correlations between Bκ(±) and Bd(±) values are found for most series of ions. Within the series of halide ions, for example, Bκ(–) increases, whereas Bd(–) decreases with anion radius. For large hydrophobic cations the opposite is true; that is, Bκ(+) increases and Bd(+) decreases with molar volume of ion. In general, the magnitudes |Bk(±)| in the changes of the compressibility coefficient are smaller than in the shifts of the dielectric relaxation time. The situation is more complicated with dielectrically saturated small ions. Since the apparently irrotationally bound water molecules around such ions do not contribute to the dielectric spectra by reorientation, comparison of compressibility changes with changes in the proton magnetic relaxation rate rather than in the dielectric relaxation time is more appropriate. Some composite ions, such as BF4(–), show special features which can, however, be explained by a nonspherical charge distribution at the ion surface.

1.4T study of proton magnetic relaxation rates, iron concentrations, and plaque burden in Alzheimer's disease and control postmortem brain tissue

We measured proton magnetic longitudinal (R(1)) and transverse (R(2)) relaxation rates at 1.4T, iron concentrations, water contents, and amyloid plaque densities in postmortem brain tissue samples from three Alzheimer's disease (AD), two possible AD, and five control subjects. Iron concentrations and R(1) were significantly higher in the temporal cortex region of our AD group compared to the controls. Frequency analyses showed that the observed trends of higher iron, R(1), and R(2) in AD gray matter regions were statistically significant. Simple regression models indicated that for AD and control gray matter the iron concentrations and water contents have significant linear correlations with R(1) and R(2). Multiple regression models based on iron concentrations and water contents were highly significant for all groups and tissue types and suggested that the effects of iron become more important in determining R(1) and R(2) in the AD samples. At 1.4T R(1) and R(2) are strongly affected by water content and to a lesser extent by variations in iron concentrations. The AD plaque density did not correlate with iron concentrations, water contents, R(1), or R(2), suggesting that increases in AD brain iron are not strongly related to the accumulation of amyloid plaques.

Proton relaxation and intermolecular structure of liquid formic acid: a nuclear magnetic resonance study Dedicated to the memory of the late Hermann Gerhard Hertz.

Proton magnetic relaxation rates in liquid formic acid have been measured and rate contributions have been separated and assigned. The assignment has been ascertained by H/D isotopic dilution series and by temperature-dependent measurements. Proton magnetic relaxation in liquid formic acid between 25 °C and 55 °C is dominated by magnetic dipole–dipole interactions between protons, with a minor contribution due to spin–rotation interactions. Suppositions in previous work of substantial additional relaxation mechanisms could not be confirmed. The intermolecular dipolar relaxation rate contribution has been used in conjunction with a theoretical model to obtain the closest intermolecular distances of proton approach and to construct the formic acid pair configuration of maximum occurrence probability in the liquid. The planar pair configuration is characterised by two intermolecular hydrogen bonds, a strong OH⋯O and a weaker CH⋯O. The pair configuration introduced could be a building block for further molecular association and chain-like structures.

The Problematic Determination of Proton Magnetic Relaxation Rates of Protein-Containing Solutions

16 data points were collected, with the times, , spanning the interval between 1.67 msec and a time at least nine mean half-lives longer. Times between consecutive 180° pulses were at least five mean half-lives. For transverse relaxation, 169 equally spaced data points were collected spanning the interval between time zero and at least 1.75 mean half-lives later. Because the built-in software of the relaxometer used was found to be unsatisfactory for fitting biexponential functions, data were analyzed with more modern commercial software (Statistica, StatSoft, Tulsa, Okla; Excel, Microsoft, Redmond, Wash). RESULTS Water, saline, and solutions of typical paramagnetic chelates of the kind used as extracellular MRI contrast agents showed strictly monoexponential decays of longitudinal and transverse magnetization, justifying the characterization of these decays by single relaxation rates, R1 and R2, respectively. In contrast, the presence of proteins in the same liquids caused biexponential decays. The chemical nature of the sample cell was without influence, arguing against a role of protein absorption to the walls. Here, we illustrate the situation only with protein solutions without contrast agents. The Table shows results for two pure proteins. Monoexponential fits were progressively unsatisfactory with increasing concentrations, although standard errors for the relaxation rates remained below 5%. Biexponential fits revealed a large-amplitude

New non-ionic water-soluble porphyrins: evaluation of manganese(III) polyhydroxylamide porphyrins as MRI contrast agents

A new series of metalloporphyrins (M = zinc(II) and manganese(III)), utilizing polyhydroxylamide substituents to achieve water solubility, has been synthesized and spectroscopically characterized. Two of these compounds, [Mn III(TPPAS)Cl] and (Mn III (TPPIS)Cl], have been evaluated as potential MRI contrast enhancement agents. The water proton magnetic relaxation rate, (1/ T 1), of aqueous [Mn III(TPPAS)Cl] solutions has been measured as a function of field strength over the range of Larmor frequencies from 0.01 to 30 MHz. Results show a typical relaxation rate pattern, similar to other water-soluble manganese (III) porphyrin compounds, over this frequency range. Conductivity and osmolality measurements for [Mn III(TPPAS)Cl] in water demonstrate complete dissociation of the chloride ion to yield [Mn III(TPPAS)(H 2O) 2) +. The two axial water ligands provide a reasonable explanation as to the source of the greater than expected proton relaxation rate of manganese(III) porphyrin compounds, in general. Variable-temperature NMR studies of the H 2TPPAS and H 2TPPIS free ligands reveal the occurrence of proton tautomerism, as indicated by two temperature dependent H β pyrrole proton signals. Actual magnetic resonance images of Sprague-Dawley rats, to which [Mn III(TPPAS))Cl] had been administered, showed significant image enhancement in the heat, liver, lungs and gastrointestinal tract. However, with an acute toxicity of 0.1 mmol kg −1, the cationic [Mn III(TPPAS)(H 2O) 2] + compound is too toxic for clinical use.

A study of the hydration of aluminate minerals based on the measurements of the mean and the variance of the proton magnetic resonance relaxation rate

Mean longitudinal proton relaxation rates and their variances were measured in hydrated mono- and tricalcium aluminates. The results were analysed using a two-site model of bulk and adsorbed water. A formalism for the calculation of the fractions of water in these states and of the relaxation rate in absorbed state was developed. A significant release of water from the adsorption layer occurred at about 400–500 min after hydration of the monocalcium aluminate. The relaxation rate of water protons in the absorbed state increased continously during the cemeny hydration (up to 1200 min). During the induction period this increase is attributed to the growing viscosity of the bulk liquid and to the nucleation. During the later stages of hydration the rate increase is explained by the diminishing number of adsorption layers. The maximal values of the relaxation rate in the adsorption layer of monocalcium aluminate indicated the monomolecular adsoprtion. The hydration of tricalcium aluminate was characterized by higher initial and lower final ( t hydr = 1100 min) values of the relaxation rate in the adsorbed state. After about 500 min of hydration the fraction of adsorbed water molecules and the relaxation rate in the adsorbed state reach a maximum.

AParameter as an Indicator for Water−Water Association in Solutions of Strong Electrolytes

After a short discussion of the formal significance of the association parameter (A), this quantity is calculated from revised experimental results for proton magnetic relaxation rates, deuteron magnetic relaxation rates, and self-diffusion coefficients of the water in aqueous solutions of a number of 1:1 and 2:1 electrolytes. An increase of the A-parameter with decreasing water concentration, which is an indicator for water proton−proton association, was found in solutions of the structure breakers CsCl and CsBr, probably for RbCl and RbBr as well. Decrease of the A-parameter with decreasing water concentration, i.e., water deassociation, was observed for moderately hydrated cations like Li+ and Na+. In 2:1 electrolytes, partly showing complex formation, the water−water association is a more complicated function of the salt concentration.

A nuclear magnetic resonance investigation of the upper airways in ferrets. I. Effects of histamine and methacholine.

Alterations induced in the upper airways of ferrets by intranasal provocation with methacholine (MC) and histamine (HS) were monitored using proton magnetic resonance imaging (MRI) and spin-spin relaxation rate (R2) measurements. Both MC and HS cause a significant increase in the MRI signal intensity and a decrease in R2 in the nasal turbinates. A dose-dependent response is observed for 20 to 315 nmol of HS, with a maximum increase in intensity of ca. 50% occurring above 80 nmol. A single unilateral challenge with MC yields a 62 +/- 3% increase in intensity. Control animals (saline-treated) show little change in image intensity. MC and HS cause decreases in the proton R2 by -27.0 +/- 5.5% and -17.2 +/- 4.3%, respectively. These data are indicative of an accumulation of fluid in the nasal airways. MRI provides an effective means to monitor changes in the nasal airways which occur as a result of pharmacological treatment.

Investigation of Complex Intramolecular Motion in Supercooled Liquids

AbstractAfter a brief résumé of the Woessner theory which treats nuclear magnetic relaxation effects caused by internal and anisotropic motion of molecules in liquids we present proton magnetic relaxation rates of specifically deuterated molecules possessing an interacting group (–OH or –COOH) and a hydrocarbon chain of increasing length, namely methanol and acetic acid, ethanol and propionic acid, n‐propanol. Measurements were done in the range from room temperature to ∼ 15 K. Various interacting substances were added to slow down the movement of the interacting group relative to the internal molecular motions, yielding respective experimental manifestations. Some brief hints are given to show the shortcomings of the Woessner theory.

Using an ultraviolet scanner to determine radiation dose distribution

Aqueous agarose gels containing ferrous ions sustain a radiolytic chain reaction, producing Fe+3. Longitudinal proton magnetic relaxation rates are increased in proportion to ferric production. The distribution of Fe+3, hence the dose, can be revealed as a scanning curve at 304 nm dependent on its extinction, coefficient, permitting visualizing of dose in these gels by a dual wavelength thin layer chromatography scanner. There is a potential for application to radiation therapy treatment planning.

Nuclear magnetic resonance relaxation study of I– and Na+ solvation structure in N-methylformamide (NMF) and preferential solvation of these ions in the mixture NMF—H2O

Proton magnetic relaxation rates of HCONDCD3, DCONHCD3 and DCONDCD2H caused by magnetic dipole–dipole interaction with 127I and 23Na in the ions I– and Na+, respectively, have been measured. These results were obtained by the isotopic H/D substitution technique with extrapolation to the limit proton content → 0. From these data closest distances of approach between the interacting nuclei were derived which, with the geometry of the NMF molecule, yielded the ion–solvent configuration in the solvation sphere. The corresponding measurements for the formyl and methyl protons were performed in NMF–water mixtures over the whole composition range. The approximate degree of preferential solvation or preferential hydration could be derived from these measurements.

NMR Relaxation study of l- and Na+ Solvation structure in dimethyl formamide (DMF)

Proton magnetic relaxation rates of HCON (CD3 )2 and DCON (CD3 ) (D2 H) caused by magnetic dipole-dipole interaction with 127 I and 23 Na in the ion I- and Na+ , respectively, have been measured. These results were obtained by the isotopic H/D substitution technique with extrapolation to the limit proton content xH → O. From these data closest distances of approach between the interacting nuclei were derived which then, with the geometry of the DMF molecule, yielded the ion-solvent configuration in the solvation sphere.

Radiation chemical and magnetic resonance studies of aqueous agarose gels containing ferrous ions

Aqueous agarose gels containing ferrous ions sustain a radiolytic chain reaction, producing Fe 3+. G(Fe 3+)-values up to 156 have been observed, independent of dose rate between 0.434 and 3.74 Gy min -1. Dissolved oxygen is needed to maintain the chain reaction, and initial ferric yields are increased if the gel is oxygen saturated, or if the Fe 2+ concentration is decreased. Longitudinal proton magnetic relaxation rates are increased in proportion to ferric production, permitting visualizing of dose levels in these gels by magnetic resonance imaging techniques. There is a potential for application to radiation therapy treatment planning.

Stereospecificity in the proton magnetic relaxation rate of enantiotopic methyls and the methyl rotation barrier

It is proposed that a distinction should be made between stereospecificity of the first kind, which provides spectral (line assignments in the NMR spectrum) and structural (molecular conformations) information, and stereospecificity of the second kind, which only provides spectral information, on the basis of the relaxation times T1. The nature of the stereospecificity was revealed in detail during analysis of the reasons for the differences in the proton relaxation times of enantiotopic gem-dimethyl groups in the conformationally rigid molecule of 2-oxo-5,5-dimethyl-1,3,2-dioxathiane. It is suggested that the barrier to rotation of the methyl in the geminal CH3-C-H fragment can be assessed from the temperature dependence of the t1 time of the methine proton. The experiment was carried out with the stereoisomeric r-2-tert-butyl-4-methyl-trans-7-methyl[2]1,3-dioxepane.

Effect of strongly interacting solutes on group rotational correlation functions in ethanol

Proton magnetic relaxation rates of solutions of LiCl and LiI in isotopically labelled ethanols CH3CD3OD, CD3CH2OD and CD3CD2OH have been measured as functions of temperature and concentration mostly at v=30 MHz, where 2πλτ≃1. The data were reduced in a way that revealed that CH3 and CH2 relaxation curves contained a residuum from the slow motion of the OH group in many cases. Thus, the rotational time correlation function of the CH3 and CH2 groups contain a residuum term stemming from the slow motion within the same molecule. The data show a threshold of the rotational energy which has to be exceeded in order to make the effect observable.

Rotational, Internal Rotational, and Translational Motion of Liquid i‐Propanol

AbstractDeuteron magnetic relaxation rates of the following isotopically substituted i‐propanols (CH3)2CHOD, (CH3)2CDOH, and (CD3)2CHOH have been measured as a function of the temperature and the frequency. Thus the present investigations were performed in the dispersion range. We have attempted to interpret these relaxation rates within the framework of the Woessner theory of internal rotation. The success was not satisfactory, the quadrupole coupling constants were smaller than expected. Proton magnetic relaxation rates of the two i‐propanols (CD3)2CDOH and (CH3)2CDOD have also been measured as a function of the temperature and the frequency. Separation of intra‐ and intermolecular contributions was performed by usual isotopic dilution technique. With the intramolecular relaxation rates again difficulties to describe internal rotation appeared. The dipole‐dipole coupling constant came out too small. The intermolecular relaxation rates could be related to intermolecular configurations fairly satisfactory, although dynamical descriptions still leaves open questions.

Rotational, internal rotational, and translational motion of acetic acid and dimethyl sulfoxide in their liquid mixture (with some results for DMSO dissolved in MeOH)

The proton magnetic relaxation rate of DMSO in the mixture 33.3 mole % DMSO + 66.7 mole % CD3COOD has been measured in the temperature range 3.5 < 1000/T < 6.0 K and at six frequencies 6 < ν < 144 MHz. The intramolecular relaxation rate was determined by the aid of the isotopic substitution technique. The rotational correlation time of “the molecule” and the time constant of the internal motion have been extracted from these experimental results. The corresponding measurements were also performed on DMSO in the solvent CD3OD (71 mole %) where no internal motion effect appeared in the temperature dependence of the relaxation rate. Furthermore, proton relaxation rates of the acetic acid methyl group and deuteron relaxation rates of the acid methyl and OD group are reported. Again, the data are given in the temperature range as above and for a number of frequencies. Rotational time correlation functions g(t) for the axid molecule are derived. Finally we present experimental results for the self-diffusion coefficients of both mixture partners DMSO and AcH and of DMSO in the solvent MeOH.

Search for hydrophobic association between small aprotic solutes from an application of the nuclear magnetic relaxation method

Proton and deuteron magnetic relaxation rates of the four solutes acetone, acetonitrile, trimethylamine, and tetramethylurea in their aqueous mixtures are reported. For the normal and deuterated organic substances the water was D2O and H2O, respectively. The intermolecular relaxation rates were determined. Experimental results for the self-diffusion coefficients of trimethylamine and tetramethylurea in their aqueous mixtures are also reported. From these results and literature data the A parameter, A=(1/T1)inter·D1/c′1 being a criterion for association, was calculated. We obtained the result that only for the largest solute molecule, i.e. tetramethylurea, A showed the typical concentration dependence indicating solute-solute association. For the other three components self-association is not outside the range of the sensitivity of the present method.