Determination of ligand-protein dissociation constants by electrospray mass spectrometry-based diffusion measurements

A novel approach for the quantification of ligand-protein interactions is presented. Electrospray ionization mass spectrometry (ESI-MS) is used to monitor the diffusion behavior of noncovalent ligands in the presence of their protein receptors. These data allow the fraction of free ligand in solution to be determined, such that the corresponding dissociation constants can be calculated. A set of conditions is developed that provides an "allowable range" of concentrations for this type of assay. The method is tested by applying it to two different inhibitor-enzyme systems. The dissociation constants measured for benzamidine-trypsin and for N,N',N' '-triacetylchitotriose-lysozyme are (50 +/- 10) and (6 +/- 1) mM, respectively. Both of these results are in good agreement with previous data from the literature. In contrast to traditional ESI-MS-based methods, the approach used in this work does not rely on the preservation of specific solution-type noncovalent interactions in the gas phase. It is shown that this method allows an accurate determination of dissociation constants, even in cases in which the ion abundance ratio of free to ligand-bound protein in ESI-MS does not reflect the corresponding concentration ratio in solution.     

Measurement of ionic diffusion in lithium fluoride by nuclear magnetic resonance techniques

Rates of diffusion of ⁷Li and ¹⁹F were investigated in doped crystals of lithium fluoride using the technique of motional narrowing of nuclear magnetic resonance lines. Major doping elements were divalent Mg and Mn ions, present in amounts between 3 and 240 × 10^–6 cation site fraction. Extrinsic vacancies introduced by this doping increased Li ion diffusion and caused ⁷Li motional narrowing to begin at lower temperatures for greater impurity contents.Diffusivities were determined from the motional narrowing curves using a method of analysis which reduces uncertainties due to magnetic field inhomogeneity and other temperature independent contributions to line broadening. Resulting log D vs 1/T plots showed the expected intrinsic, free vacancy extrinsic, and divalent ion-vacancy association regions of Li ion diffusivity. Activation energies determined for these regions were 1.87±0.09, 0.66±0.03, and 0.91±0.05 eV, respectively. These values yielded the energy for motion of a cation vacancy as 0.66 eV and the energy of formation of a Schottky defect as 2.42 eV.Experimental results obtained earlier in powdered LiF: Mn samples are clarified, and indications concerning the effects of other impurities on Li ion diffusion are presented and discussed.     

The photomagnetic effect detected by nuclear magnetic resonance

The results of experiments with transparent easy-plane antiferromagnetic iron borate (FeBO₃) show that nuclear magnetic resonance (NMR) offers an effective tool for the study of photomagnetism in magnetically ordered materials. It is established that illumination of a FeBO₃ sample leads to a shift of the ⁵⁷Fe NMR frequency due to a change in the electron magnetization and significantly increases the nuclear induction signal intensity in the range of existence of the domain boundaries.     

Thermometric detection of nuclear magnetic resonance

Nuclear magnetic resonance has been detected in nonmagnetic materials by observing the temperature rise in the sample. The experiments were performed at temperatures between 1 and 4 K, and results are presented for the²⁷Al resonance in aluminum metal and the¹⁹F resonance in a sample of doped CaF₂. The primary sources of noise have been identified and ways of improving the apparatus are discussed. The technique could prove useful in experiments that require a large range of frequencies to be swept and in experiments investigating the effects of strong rf fields.     

Utilization of the effect of temperature on nuclear quadrupole resonance for absolute temperature measurements

Conclusions As the result of the above analysis of the theoretical and experimental data it was possible to obtain a NQR frequency equation which takes into consideration the deformation of the crystalline lattice, thus leading to a reduction in the absolute temperature measurement error down to 0.6° in the range of 20–273°K (in preceding work the error in this interval amounted to at least 20–50°). Possible ways of a further correction of the above functional relationship and a consequent raising of the absolute temperature measurement precision have been outlined.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 39–41, January, 1967.     

11B nuclear magnetic resonance in boron-doped diamond

Abstract

This review summarizes recent results obtained by ¹¹B solid-state nuclear magnetic resonance (NMR) on boron-doped diamond, grown by the high-pressure high-temperature (HPHT) or chemical vapor deposition techniques. Simple single-pulse experiments as well as advanced two-dimensional NMR experiments were applied to the boron sites in diamond. It is shown that magic-angle spinning at magnetic fields above 10 T is suitable for observation of high-resolution ¹¹B spectra of boron-doped diamond. For boron-doped HPHT diamonds, the existence of the excess boron that does not contribute to electrical conductivity was confirmed and its ¹¹B NMR signal was characterized. The point-defect structures (B+H complexes and -B-B-/-B-C-B- clusters), postulated previously for the excess boron, were discarded and graphite-like structures were assigned instead.     

11B nuclear magnetic resonance in boron-doped diamond

This review summarizes recent results obtained by ¹¹B solid-state nuclear magnetic resonance (NMR) on boron-doped diamond, grown by the high-pressure high-temperature (HPHT) or chemical vapor deposition techniques. Simple single-pulse experiments as well as advanced two-dimensional NMR experiments were applied to the boron sites in diamond. It is shown that magic-angle spinning at magnetic fields above 10 T is suitable for observation of high-resolution ¹¹B spectra of boron-doped diamond. For boron-doped HPHT diamonds, the existence of the excess boron that does not contribute to electrical conductivity was confirmed and its ¹¹B NMR signal was characterized. The point-defect structures (B+H complexes and -B-B-/-B-C-B- clusters), postulated previously for the excess boron, were discarded and graphite-like structures were assigned instead.     

On the quantumness of correlations in nuclear magnetic resonance

Nuclear magnetic resonance (NMR) was successfully employed to test several protocols and ideas in quantum information science. In most of these implementations, the existence of entanglement was ruled out. This fact introduced concerns and questions about the quantum nature of such bench tests. In this paper, we address some issues related to the non-classical aspects of NMR systems. We discuss some experiments where the quantum aspects of this system are supported by quantum correlations of separable states. Such quantumness, beyond the entanglement-separability paradigm, is revealed via a departure between the quantum and the classical versions of information theory. In this scenario, the concept of quantum discord seems to play an important role. We also present an experimental implementation of an analogue of the single-photon Mach-Zehnder interferometer employing two nuclear spins to encode the interferometric paths. This experiment illustrates how non-classical correlations of separable states may be used to simulate quantum dynamics. The results obtained are completely equivalent to the optical scenario, where entanglement (between two field modes) may be present.     

High-pressure cylindrical acoustic resonance diffusion measurements of methane in liquid hydrocarbons

A novel cylindrical acoustic resonance method for the measurement of gas diffusion into liquids at high pressures is described. The measurements were per formed in a vertically oriented cylindrical acoustic resonator containing both the liquid solvent and gaseous diffusant while under high-precision isothermal and isobaric control. Individual resonance modes of the liquid column, the gas column, and the two-phase coupled fluid are resolved in the fast Fourier trans form acoustic-resonance spectrum (FFT-ARS). High-resolution acoustic spectra measured at frequent time intervals reveal the changes which accompany the diffusion fusion of gas into the liquid phase. One change, namely, the growth in length of the liquid column, results in a systematic shift to higher frequencies of axial modes in the gas column. The temporal behavior of this moving boundary, together with quantitative measurement of the flow to the gas column required to sustain the constant pressure, permits determination of the gas-into-liquid diffusion coefficient. Diffusion coefficients were determined from the change in frequency as a function of time of axial resonance modes in the gas-phase virtual cylinder as the surface of the underlying liquid phase advanced due to gas absorption. Measurements of the systems methane/n-octane, methane/n-nonane, and methane/n-decane were performed as a function of temperature at a pressure of 250 psia. Comparisons is made to results obtained elsewhere and by other methods but at the same temperatures and pressure.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Structure of dispersion media by nuclear magnetic resonance

The change of the diamagnetic shielding constant of a benzene molecule interacting with the solid phase surface is calculated.Notation _d diamagnetic shielding constant - e, m_e electron charge and mass, respectively - c speed of light - _b ^o benzene wave function - _m ^o and _m ^o* eigenfunctions of benzene molecule and their conjugates - W_mo matrix elements of the perturbation operator - E _o ^o energy of the ground state of a benzene molecule - e _m ^o energy of the excited states of a benzene molecule - a ₀ Bohr radius Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 476–482, September, 1981.     

盐酸普罗帕酮的核磁共振谱分析

该文利用核磁共振实验技术详细研究了抗心律失常药物盐酸普罗帕酮的化学结构特征，并借助二维核磁共振实验技术对盐酸普罗帕酮的氢谱和碳谱进行了完全归属，为该类化合物的结构解析提供了有益的分析依据。     

Recent advances in nuclear magnetic resonance quantum information processing

Quantum information processors have the potential to drastically change the way we communicate and process information. Nuclear magnetic resonance (NMR) has been one of the first experimental implementations of quantum information processing (QIP) and continues to be an excellent testbed to develop new QIP techniques. We review the recent progress made in NMR QIP, focusing on decoupling, pulse engineering and indirect nuclear control. These advances have enhanced the capabilities of NMR QIP, and have useful applications in both traditional NMR and other QIP architectures.     

In situ monitoring of the microstructure of detergent drops during drying using a rapid nuclear magnetic resonance diffusion measurement

The application of a nuclear magnetic resonance (NMR) diffusion measurement suitable for monitoring, in situ, the evolution of microstructure in commercial surfactant-based detergent drops as a response to drying is demonstrated for the first time. We utilise pulsed field gradient (PFG) NMR diffusion techniques to observe variations in self-diffusion coefficient, surface-to-volume ratio and characteristic pore size by probing the water content of the drops. Previously, we quantified the evolution of microstructure in vials of detergent paste using conventional PFG techniques. Now we apply a rapid PFG technique to enable this measurement during the relatively fast in situ drying of a drop with spherical geometry, relevant to spray drying processes. A finer structure is seen to form in the drops compared to the paste in the vials.