Proton Nuclear Magnetic Relaxation Research Articles

Engineered Nonviral Protein Cages Modified for MR Imaging.

Diagnostic medical imaging utilizes magnetic resonance (MR) to provide anatomical, functional, and molecular information in a single scan. Nanoparticles are often labeled with Gd(III) complexes to amplify the MR signal of contrast agents (CAs) with large payloads and high proton relaxation efficiencies (relaxivity, r1). This study examined the MR performance of two structurally unique cages, AaLS-13 and OP, labeled with Gd(III). The cages have characteristics relevant for the development of theranostic platforms, including (i) well-defined structure, symmetry, and size; (ii) the amenability to extensive engineering; (iii) the adjustable loading of therapeutically relevant cargo molecules; (iv) high physical stability; and (v) facile manufacturing by microbial fermentation. The resulting conjugates showed significantly enhanced proton relaxivity (r1 = 11-18 mM-1 s-1 at 1.4 T) compared to the Gd(III) complex alone (r1 = 4 mM-1 s-1). Serum phantom images revealed 107% and 57% contrast enhancements for Gd(III)-labeled AaLS-13 and OP cages, respectively. Moreover, proton nuclear magnetic relaxation dispersion (1H NMRD) profiles showed maximum relaxivity values of 50 mM-1 s-1. Best-fit analyses of the 1H NMRD profiles attributed the high relaxivity of the Gd(III)-labeled cages to the slow molecular tumbling of the conjugates and restricted local motion of the conjugated Gd(III) complex.

Lanthanide DO3A-Complexes Bearing Peptide Substrates: The Effect of Peptidic Side Chains on Metal Coordination and Relaxivity.

Two DO3A-type ligands conjugated to substrates of urokinase (L3) and caspase-3 (L4) via a propyl-amide linker were synthesized and their lanthanide(III) (Ln3+) complexes studied. A model compound without peptide substrate (L2) and an amine derivative ligand mimicking the state after enzymatic cleavage (L1) were also prepared. Proton Nuclear Magnetic Relaxation Dispersion (NMRD) profiles recorded on the gadolinium(III) (Gd3+) complexes, complemented with the assessment of hydration numbers via luminescence lifetime measurements on the Eu3+ analogues, allowed us to characterize the lanthanide coordination sphere in the chelates. These data suggest that the potential donor groups of the peptide side chains (carboxylate, amine) interfere in metal coordination, leading to non-hydrated LnL3 and LnL4 complexes. Nevertheless, GdL3 and GdL4 retain a relatively high relaxivity due to an important second-sphere contribution generated by the strongly hydrophilic peptide chain. Weak PARACEST effects are detected for the amine-derivative EuL1 and NdL1 chelates. Unfortunately, the GdL3 and GdL4 complexes are not significantly converted by the enzymes. The lack of enzymatic recognition of these complexes can likely be explained by the participation of donor groups from the peptide side chain in metal coordination.

Influence of Pluronic F127 microenvironments on the photochemical nitric oxide release from S-nitrosoglutathione

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) (F127) hydrogels have been used to deliver nitric oxide (NO) topically in biomedical applications. Here, the effect of F127 microenvironments on the photochemical NO release from S-nitrosoglutathione (GSNO) was investigated in F127 solutions 7.6 wt% 15 wt% and 22.5 wt% at 15 °C and 37 °C. Small-angle X-ray Scattering (SAXS) and Differential Scanning Calorimetry (DSC) measurements, along with proton Nuclear Magnetic Resonance (1H NMR) spectral shifts and T2 relaxation data at six different concentration-temperature conditions, allowed identifying F127 microphases characterized by: a sol phase of unimers; micelles in non-defined periodic order, and a gel phase of cubic packed micelles. Kinetic measurements showed that GSNO photodecompositon proceeds faster in micellized F127 where GSNO is segregated to the intermicellar microenvironment. Real time kinetic monitoring of NO release and T2 relaxation profiles showed that NO is preferentially partitioned into the hydrophobic PPO cores of the F127 micelles, with the consequent decrease in its rate of release to the gas phase. These results show that F127 microphases affect both the kinetics of GSNO photodecomposition and the rate of NO escape and can be used to modulate the photochemical NO delivery from F127/GSNO solutions.

A Magnetic Chameleon: Biocompatible Lanthanide Fluoride Nanoparticles with Magnetic Field Dependent Tunable Contrast Properties as a Versatile Contrast Agent for Low to Ultrahigh Field MRI and Optical Imaging in Biological Window

A novel type of multimodal, magnetic resonance imaging/optical imaging (MRI/OI) contrast agent was developed, based on core-shell lanthanide fluoride nanoparticles composed of a β-NaHoF4 core plus a β-NaGdF4:Yb3+ , Tm3+ shell with an average size of ∼24 nm. The biocompatibility of the particles was ensured by a surface modification with poly acrylic acid (PAA) and further functionalization with an affinity ligand, folic acid (FA). When excited using 980 nm near infrared (NIR) radiation, the contrast agent (CA) shows intense emission at 802 nm with lifetime of 791±3 μs, due to the transition 3 H4 →3 H6 of Tm3+ . Proton nuclear magnetic relaxation dispersion (1 H-NMRD) studies and magnetic resonance (MR) phantom imaging showed that the newly synthesized nanoparticles, decorated with poly(acrylic acid) and folic acid on the surface (NP-PAA-FA), can act mainly as a T1 -weighted contrast agent below 1.5 T, a T1 /T2 dual-weighted contrast agent at 3 T, and as highly efficient T2 -weighted contrast agent at ultrahigh fields. In addition, NP-PAA-FA showed very low cytotoxicity and no detectable cellular damage up to a dose of 500 μg mL-1 .

(1)H NMR Relaxation Study of a Magnetic Ionic Liquid as a Potential Contrast Agent.

A proton nuclear magnetic relaxation dispersion (1)H NMRD study of the molecular dynamics in mixtures of magnetic ionic liquid [P66614][FeCl4] with [P66614][Cl] ionic liquid and mixtures of [P66614][FeCl4] with dimethyl sulfoxide (DMSO) is presented. The proton spin-lattice relaxation rate, R1, was measured in the frequency range of 8 kHz-300 MHz. The viscosity of the binary mixtures was measured as a function of an applied magnetic field, B, in the range of 0-2 T. In the case of DMSO/[P66614][FeCl4] the viscosity was found to be independent from the magnetic field, while in the case of the [P66614][Cl]/[P66614][FeCl4] system viscosity decreased with the increase of the magnetic field strength. The spin-lattice relaxation results were analyzed for all systems taking into account the relaxation mechanisms associated with the molecular motions with correlation times in a range between 10(-11) and 10(-7)s, usually observed by NMRD, and the paramagnetic relaxation contributions associated with the presence of the magnetic ions in the systems. In the case of the DMSO/[P66614][FeCl4] system the R1 dispersion shows the relaxation enhancement due to the presence of the magnetic ions, similar to that reported for contrast agents. For the [P66614][Cl]/[P66614][FeCl4] system, the R1 dispersion presents a much larger paramagnetic relaxation contribution, in comparison with that observed for the DMSO/[P66614][FeCl4] mixtures but different from that reported for other magnetic ionic liquid system. In the [P66614][Cl]/[P66614][FeCl4] system the relaxation enhancement associated with the paramagnetic ions is clearly not proportional to the concentration of magnetic ions, in contrast with what is observed for the DMSO/[P66614][FeCl4] system.

Terpyridine-based heteroditopic ligand for Ru(II)Ln3(III) metallostar architectures (Ln = Gd, Eu, Nd, Yb) with MRI/optical or dual-optical responses.

A new ditopic ligand (L) based on a 2,2':5',4″-terpyridine unit substituted in the 2″,6″ positions with iminodiacetate arms has been designed and synthesized for the construction of Ru(II)L3Ln3(III) supramolecular architectures. The two components of this system, a 2,2'-bipyridine unit for Ru(II) coordination and a pyridine-bis(iminodiacetate) core for Ln(III) coordination, are tightly connected via a covalent Carom(py)-Carom(py) bond. The paramagnetic and photophysical properties of the corresponding tetrametallic Ru(II)L3Gd3(III) complex have been evaluated, highlighting the potential of this metallostar structure to act as a bimodal MRI/optical imaging agent. Variable-temperature (17)O NMR and proton nuclear magnetic relaxation dispersion (NMRD) measurements showed that this complex exhibits (i) a remarkable relaxivity per metallostar molecule, particularly at clinical and high magnetic fields (r1(310K) = 51.0 and 36.0 mM(-1) s(-1) at 20 and 300 MHz, respectively) and (ii) a near-optimal residence lifetime of Gd(III) coordinated water molecule (τM(310K) = 77.5 ns). This is the result of the presence of two inner-sphere water molecules in the Gd(III) components of the metallostar and a slow tumbling rate of the molecule (τR(310K) = 252 ps). Upon excitation in the visible domain (λexc = 472 nm), the Ru(II) component of the complex exhibits a bright-red luminescence centered at 660 nm with a quantum yield of 2.6% in aqueous solutions at pH 7.4. Moreover, this Ru(II)L3Gd3(III) assembly is also characterized by a high kinetic inertness in biological media (PBS and human serum solutions) and a high photostability (photobleaching). Finally, preliminary photophysical studies on RuL3Nd3 and RuL3Yb3 assemblies revealed that the Ru(II) center acts as an effective sensitizer for Ln(III)-based luminescence in the near-IR region. The Nd(III) species was found to be the most effective at quenching the (3)MLCT luminescence of the Ru center.

A new approach to follow the formation of iron oxide nanoparticles synthesized by thermal decomposition

A novel way has been proposed to follow the formation of nanocrystalline magnetite. Iron oxide nanoparticles were synthesized by the thermal decomposition of Fe(acac)3 in the presence of oleic acid and oleylamine surfactants at high temperature. The species produced during the synthetic process are characterized through their effects on the proton nuclear magnetic relaxation of the reaction medium and their sizes. As shown by transmission electron microscopy, photon correlation spectroscopy and x-ray diffraction, the diameter of nano-objects increases when the time synthesis is longer. Magnetic properties evaluated by nuclear magnetic resonance (NMRD profiles, T1 and T2 measurements) were correlated with the size parameters.

Tetranuclear d-f Metallostars: Synthesis, Relaxometric, and Luminescent Properties

A novel ditopic ligand DTPA-ph-phen, based on 1,10-phenanthroline and diethylenetriaminepentaacetic acid (DTPA) units, has been designed and fully characterized by (1)H, (13)C, and 2D-COSY NMR spectroscopy, IR and electrospray ionization mass spectrometry (ESI-MS) techniques. The DTPA core of the ligand specifically binds Ln(III) ions (Ln = Eu, Gd) resulting in formation of the [Ln{DTPA-ph-phen}(H(2)O)](-) complex. The photophysical properties of the Eu(III) compound have been investigated, and the complex shows characteristic red luminescence with an overall quantum yield of 2.2%. Reaction of [Gd{DTPA-ph-phen}(H(2)O)](-) with Ru(II) leads to further self-assembly into a heterobimetallic metallostar complex containing Gd(III) and Ru(II) in a 3:1 ratio. This tetranuclear [(Gd{DTPA-ph-phen})(3)(H(2)O)(3)Ru](-) complex (Gd(3)Ru), formed by the coordination of Ru(II) to the 1,10-phenanthroline unit, has been characterized by a range of experimental techniques and evaluated toward its feasibility as a potential bimodal optical/MRI agent. The Gd(3)Ru metallostar shows intense metal-to-ligand charge transfer (MLCT) transition resulting in intense light absorption in the visible spectral region. Upon irradiation into this MLCT band at 450 nm, the Gd(3)Ru complex exhibits red broad-band luminescence in the range of 550-800 nm centered at 610 nm with a quantum yield of 4.8%. Proton nuclear magnetic relaxation dispersion (NMRD) measurements indicate that the Gd(3)Ru complex exhibits an enhanced relaxivity value r(1) of 36.0 s(-1) mM(-1) per metallostar molecule at 20 MHz and 310 K. The ability of the complex to noncovalently bind to human serum albumin (HSA) was investigated, but no significant interaction was detected.

Synthesis and Characterization of a Hypoxia‐Sensitive MRI Probe

Tissue hypoxia occurs in pathologic conditions, such as cancer, ischemic heart disease and stroke when oxygen demand is greater than oxygen supply. An imaging method that can differentiate hypoxic versus normoxic tissue could have an immediate impact on therapy choices. In this work, the gadolinium(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with a 2-nitroimidazole attached to one carboxyl group via an amide linkage was prepared, characterized and tested as a hypoxia-sensitive MRI agent. A control complex, Gd(DO3A-monobutylamide), was also prepared in order to test whether the nitroimidazole side-chain alters either the water proton T(1) relaxivity or the thermodynamic stability of the complex. The stabilities of these complexes were lower than that of Gd(DOTA)(-) as expected for mono-amide derivatives. The water proton T(1) relaxivity (r(1)), bound water residence lifetime (τ(M)) and rotational correlation time (τ(R)) of both complexes was determined by relaxivity measurements, variable temperature (17) O NMR spectroscopy and proton nuclear magnetic relaxation dispersion (NMRD) studies. The resulting parameters (r(1) =6.38 mM(-1) s(-1) at 20 MHz, τ(M) =0.71 μs, τ(R) =141 ps) determined for the nitroimidazole derivative closely parallel to those of other Gd(DO3A-monoamide) complexes of similar molecular size. In vitro MR imaging experiments with 9L rat glioma cells maintained under nitrogen (hypoxic) versus oxygen (normoxic) gas showed that both agents enter cells but only the nitroimidazole derivative was trapped in cells maintained under N(2) as evidenced by an approximately twofold decrease in T(1) measured for hypoxic cells versus normoxic cells exposed to this agent. These results suggest that the nitroimidazole derivative might serve as a molecular reporter for discriminating hypoxic versus normoxic tissues by MRI.

Monoglyceride Stabilized Oil in Water Emulsions: an Investigation of Structuring and Shear History on Phase Behaviour

In this study we report on the effects of structuring, aging, temperature, and shear history on the polymorphism and stability of structured monoglyceride stabilized oil in water emulsions, or MAG gels. With knowledge that the structure of the gel is paramount towards its functionality, this study investigated how structuring of MAG gel affects proton relaxation and monoglyceride crystal polymorphism. The structured MAG gel was compared to its compositionally equivalent unstructured components containing either dry or hydrated monoglycerides. Proton relaxation studies were conducted using pulsed proton Nuclear Magnetic Resonance T2 relaxation analysis. Powder X-ray Diffraction was used to determine the monoglyceride crystal polymorphism within the system. Proton relaxation was greatly affected by the structuring of MAG gel components, with the structured MAG gel displaying faster relaxation times compared to its unstructured components. The structured MAG gel also displayed different polymorphic behaviour than its unstructured components, with structured gels exhibiting greater stability, and displaying both α and β monoglyceride polymorphic forms. The application of shear resulted in greater water mobility within MAG gels compared to non-sheared samples, as well as a greater proportion of the β polymorphic population. This study established a relationship between water mobility determined by T2 relaxation analysis and the proportion of the β polymorph population determined through XRD reflections. It clearly demonstrates that an increase in the β polymorph population leads to a decrease in the strength of water binding, and that shear enhances this process.

A new metallostar complex based on an aluminum(iii) 8-hydroxyquinoline core as a potential bimodal contrast agent

A ditopic DTPA monoamide derivative containing an 8-hydroxyquinoline moiety was synthesized and the corresponding gadolinium(III) complex ([Gd(H5)(H(2)O)](-)) was prepared. After adding aluminum(III), the 8-hydroxyquinoline part self-assembled into a heteropolymetallic triscomplex [(Gd5)(3)Al(H(2)O)(3)](3-). The magnetic and optical properties of this metallostar compound were investigated in order to classify it as a potential in vitro bimodal contrast agent. The proton nuclear magnetic relaxation dispersion measurements indicated that the relaxivity r(1) of [Gd(H5)(H(2)O)](-) and [(Gd5)(3)Al(H(2)O)(3)](3-) at 20 MHz and 310 K equaled 6.17 s(-1) mM(-1) and 10.9 s(-1) mM(-1) per Gd(III) ion respectively. This corresponds to a relaxivity value of 32.7 s(-1) mM(-1) for the supramolecular complex containing three Gd(III) ions. The high relaxivity value is prominently caused by an increase of the rotational tumbling time τ(R) by a factor of 2.7 and 5.5 respectively, in comparison with the commercially used MRI contrast agent Gd(III)-DTPA (Magnevist®). Furthermore, upon UV irradiation, [(Gd5)(3)Al(H(2)O)(3)](3-) exposes green broad-band emission with a maximum at 543 nm. Regarding the high relaxivity and the photophysical properties of the [(Gd5)(3)Al(H(2)O)(3)](3-) metallostar compound, it can be considered as a lead compound for in vitro bimodal applications.

A Heterobimetallic Ruthenium–Gadolinium Complex as a Potential Agent for Bimodal Imaging

Trinuclear heterobimetallic Ln(III)-Ru(II) complexes (Ln = Eu, Gd) based on a 1,10-phenanthroline ligand bearing a diethylenetriaminepentaacetic acid (DTPA) core have been synthesized and fully characterized by a range of experimental techniques. The (17)O NMR and proton nuclear magnetic relaxation dispersion (NMRD) measurements of Gd(III)-Ru(II) show that, in comparison to the parent Gd-DTPA, this complex exhibits improved relaxivity, which is the result of an increase of the rotational correlation time. Relaxometry and ultrafiltration experiments indicate that the 1,10-phenanthroline ligand has a high affinity for noncovalent binding to human serum albumin, which results in a high relaxivity r(1) of 14.3 s(-1) mM(-1) at 20 MHz and 37 °C. Furthermore, the Ln(III)-Ru(II) complexes (Ln = Eu, Gd) show an intense light absorption in the visible spectral region due to metal-to-ligand charge transfer (MLCT) transitions. Upon excitation into the MLCT band at 440 nm, the complexes exhibit a bright-red luminescence centered at 610 nm, with a quantum yield of 4.7%. The luminescence lifetime equals 540 ns and is therefore long enough to exceed the fluorescent background. Monometallic lanthanide complexes have also been synthesized, and the Eu(III) analogue shows a characteristic red luminescence with a quantum yield of 0.8%. Taking into account the relaxometric and luminescent properties, the developed Gd(III)-Ru(II) complex can be considered as a potential in vitro bimodal imaging agent.

A novel approach to assess mean lethal radiation dose with water proton spin lattice relaxation times

AbstractThe assessment of mean lethal radiation dose (D0) in human organs, using multi-target and linear quadratic models, with water proton nuclear magnetic resonance spin lattice relaxation time yields a correlation coefficient of 0.90 and 0.82, respectively. Results of this study reveal that as the spin lattice relaxation time increases, the D0 decreases.

Hydration Behavior of Dietary Fibers and Polar Groups Relevant to Hydration Measured by Proton Nuclear Magnetic Relaxation

Hydration Behavior of Dietary Fibers and Polar Groups Relevant to Hydration Measured by Proton Nuclear Magnetic Relaxation

Detecting columnar deformations in a supermesogenic octapode by proton NMR relaxometry

We used proton ( (1)H nuclear magnetic relaxation (NMR) dispersions to study the molecular dynamics in the isotropic phase and mesophases (nematic and columnar hexagonal) of a supermesogenic octapode formed by laterally connecting calamitic mesogens to an inorganic silsesquioxane cube through flexible spacers. The dispersions of the spin-lattice relaxation time (T(1)) are interpreted through relaxation mechanisms used for the study of molecular dynamics in low-molar-mass liquid crystals but adapted to the case of liquid crystalline supermolecules. At high frequencies (above 10MHz) the behaviour of the T(1) with the Larmor frequency is similar for all phases and is ascribed to local reorientations and/or rotations. At intermediate and low frequencies (below 10MHz) our results show notable differences in the T(1) behaviour with respect to the mesophases. The nematic (N) and isotropic (Iso) phases' low-frequency results are similar and are interpreted for both phases in terms of order director fluctuations (ODF), revealing that even in the isotropic phase local nematic order is detected by proton NMR relaxometry. Local nematic order in the Iso phase is interpreted in terms of the presence of nematic cybotactic clusters induced by the interdigitation of mesogens that is promoted by the silsesquioxane octapode molecular structure. In the columnar hexagonal (Col (h) phase, the T(1) dispersions show that elastic columnar deformations (ECD) dominate the nuclear magnetic relaxation below 10MHz. This result shows that the columnar packing of the octapode clearly restricts the collective fluctuations of the mesogenic units inspite of their local nematic order.

Proton NMR relaxation as a probe for setting cement pastes

We report a 20-MHz proton nuclear magnetic resonance T1 relaxation study of cement paste hydration in the early stages of setting, using different centimeter-sized samples of cements of various origins and different water-to-cement ratios. In every sample, during the first few minutes of hydration, it is found that inverse Laplace processing of inversion-recovery measurements systematically exhibits at least two T1 values: a long one, around 100 ms, whose value correlates well with water content and which may be attributed to bulk water surrounding cement grains; and a short one, around 2 ms, which is quite insensitive to water-to-cement ratio and which may be attributed to water embedded in floculated cement grains before setting occurs. The time evolution of the longest T1 value for several hours is also shown to exhibit a characteristic five-stage behavior that is well correlated with known stages of the hydration process: initial reaction, induction period, acceleration period, deceleration period and slow hydration reaction. These results are compared with calorimetric measurements and electrical conductivity literature.

Acoustical enhancement of nuclear magnetic relaxation rates in liquids

Proton nuclear magnetic relaxation is known to depend on thermal motion. That motion can be affected if an acoustic wave runs through the sample. Nuclear magnetic relaxation was shown to be modified by acoustic waves in solids, but the phenomenon was never observed in liquids. A quantitative estimation is here obtained for liquids whose relaxation is governed by magnetic dipolar coupling, thanks to the calculation of the increment to spectral density functions due to acoustic stimulation. The result of the calculation leads to the conclusion that the effect is negligible for monochromatic excitation if the wave amplitude remains compatible with the safety requirements typical of magnetic resonance imaging.

High Relaxivity Gadolinium Hydroxypyridonate−Viral Capsid Conjugates: Nanosized MRI Contrast Agents1

High relaxivity macromolecular contrast agents based on the conjugation of gadolinium chelates to the interior and exterior surfaces of MS2 viral capsids are assessed. The proton nuclear magnetic relaxation dispersion (NMRD) profiles of the conjugates show up to a 5-fold increase in relaxivity, leading to a peak relaxivity (per Gd3+ ion) of 41.6 mM(-1) s(-1) at 30 MHz for the internally modified capsids. Modification of the exterior was achieved through conjugation to flexible lysines, while internal modification was accomplished by conjugation to relatively rigid tyrosines. Higher relaxivities were obtained for the internally modified capsids, showing that (i) there is facile diffusion of water to the interior of capsids and (ii) the rigidity of the linker attaching the complex to the macromolecule is important for obtaining high relaxivity enhancements. The viral capsid conjugated gadolinium hydroxypyridonate complexes appear to possess two inner-sphere water molecules (q = 2), and the NMRD fittings highlight the differences in the local motion for the internal (tauRl = 440 ps) and external (tauRl = 310 ps) conjugates. These results indicate that there are significant advantages of using the internal surface of the capsids for contrast agent attachment, leaving the exterior surface available for the installation of tissue targeting groups.

Albumin Binding, Relaxivity, and Water Exchange Kinetics of the Diastereoisomers of MS-325, a Gadolinium(III)-Based Magnetic Resonance Angiography Contrast Agent

The amphiphilic gadolinium complex MS-325 ((trisodium-{(2-(R)-[(4,4-diphenylcyclohexyl) phosphonooxymethyl] diethylenetriaminepentaacetato) (aquo)gadolinium(III)}) is a contrast agent for magnetic resonance angiography (MRA). MS-325 consists of two slowly interconverting diastereoisomers, A and B (65:35 ratio), which can be isolated at pH > 8.5 (TyeklAr, Z.; Dunham, S. U.; Midelfort, K.; Scott, D. M.; Sajiki, H.; Ong, K.; Lauffer, R. B.; Caravan, P.; McMurry, T. J. Inorg. Chem. 2007, 46, 6621-6631). MS-325 binds to human serum albumin (HSA) in plasma resulting in an extended plasma half-life, retention of the agent within the blood compartment, and an increased relaxation rate of water protons in plasma. Under physiological conditions (37 degrees C, pH 7.4, phosphate buffered saline (PBS), 4.5% HSA, 0.05 mM complex), there is no statistical difference in HSA affinity or relaxivity between the two isomers (A 88.6 +/- 0.6% bound, r1 = 42.0 +/- 1.0 mM(-1) s(-1) at 20 MHz; B 90.2 +/- 0.6% bound, r1 = 38.3 +/- 1.0 mM(-1) s(-1) at 20 MHz; errors represent 1 standard deviation). At lower temperatures, isomer A has a higher relaxivity than isomer B. The water exchange rates in the absence of HSA at 298 K, kA298 = 5.9 +/- 2.8 x 10(6) s(-1), kB298 = 3.2 +/- 1.8 x 10(6) s(-1), and heats of activation, DeltaHA = 56 +/- 8 kJ/mol, DeltaHB = 59 +/- 11 kJ/mol, were determined by variable-temperature 17O NMR at 7.05 T. Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded over the frequency range of 0.01-50 MHz at 5, 15, 25, and 35 degrees C in a 4.5% HSA in PBS solution for each isomer (0.1 mM). Differences in the relaxivity in HSA between the two isomers could be attributed to the differing water exchange rates.

Microstructure and texture of cementitious porous materials

We have characterized the microstructure of different cementitious materials (white and Portland cement pastes, mortars, concretes) by different magnetic resonance techniques. In particular, we show how the measurement of proton nuclear magnetic spin-lattice relaxation as a function of magnetic field strength (and hence nuclear Larmor frequency) can provide reliable information on the dynamics of proton species at the surface of CSH, the specific surface area and the pore size distribution throughout the progressive hydration of cement-based materials. The measurement does not require any drying temperature modification and is sufficiently fast to be applied continuously during the progressive hydration of the material. Coupling this method with the standard proton nuclear spin relaxation and high-resolution NMR allows us to follow the development of microscale texture within the material.