Crystallization of a globular protein in lipid cubic phase

We studied the crystallization of a globular protein, lysozyme, in the cubic phase of the lipid mono-olein. The solubility of lysozyme in salt solution decreased by a factor of approximately 4 when confined in cubic phase. Monte Carlo simulations and calculations show that this can be explained by the confinement of lysozyme molecules to the narrow water cells in the cubic phase.     

1H-1H double-quantum CRAMPS NMR at very-fast MAS (nuR=35 kHz): a resolution enhancement method to probe 1H-1H proximities in solids

A High-resolution two-dimensional (2D) (1)H double-quantum (DQ) homonuclear recoupling experiments, combined with smooth amplitude-modulation (SAM) homonuclear decoupling is presented. The experiment affords highly resolved and clean (1)H DQ-SQ 2D spectra at very-fast MAS rates (nu(R)=35 kHz). The method is well suited to probe (1)H-(1)H distances in powdered solids and demonstrations are applied on a NaH(2)PO(4) powdered sample, an inorganic compound having hydrogen bonding networks.     

High resolution NMR imaging: Gd-DTPA labeled enzyme as a probe for permeability studies in polyacrylamide gels.

The penetration of horse liver alcohol dehydrogenase (HLAD) molecules into polyacrylamide gel beads, which are used to immobilize the enzyme, was studied. HLAD was labeled with gadolinium diethylene-triamine-pentaacetic acid (Gd-DTPA), using the N-hydroxy-succinimide active ester of DTPA as a chelating agent. The HLAD-(Gd-DTPA)27 has a 3.7-fold larger longitudinal (R1) and a 14-fold larger transversal relaxivity (R2) (at 2.4 T) than the plain Gd-DTPA. A series of dry polyacrylamide gel beads, with total monomer concentration ranging from 5% to 30% were synthesized and swollen in a buffered solution of HLAD-(Gd-DTPA)27. The gel beads were examined with high resolution NMR imaging. The T1- and T2-weighted images revealed that the permeability for the labeled HLAD decreased with increasing total monomer concentration of the gel beads. These imaging results correlate fairly well with the enzymatic reactivities measured for the same range of gel beads but swollen in a solution of non labeled HLAD and NAD+ (nicotinamide adenine dinucleotide). It is concluded that Gd-labeling can be used to monitor the distribution of weakly concentrated, water soluble products in a solid matrix.     

High-field high-speed MAS resolution enhancement in 1H NMR spectroscopy of solids

Resolution in ¹H NMR spectra of solids can be significantly enhanced with fast magic-angle spinning and high magnetic fields. A variable field and spinning speed study up to 25 T and 40 kHz shows that the homogeneous line broadening is inversely proportional to the product of magnetic field strength and spinning speed. The combination of high field and fast speed yields a ¹H linewidth approaching the intrinsic limit determined by anisotropy of magnetic susceptibility. An analysis of the anisotropic magnetic susceptibility line broadening is presented.     

A 1H/19F minicoil NMR probe for solid-state NMR: application to 5-fluoroindoles

We show that it is feasible to use a minicoil for solid-state 19F 1H NMR experiments that has short pulse widths, good RF homogeneity, and excellent signal-to-noise for small samples while using low power amplifiers typical to liquid-state NMR. The closely spaced resonant frequencies of 1H and 19F and the ubiquitous use of fluorine in modern plastics and electronic components present two major challenges in the design of a high-sensitivity, high-field 1H/19F probe. Through the selection of specific components, circuit design, and pulse sequence, we were able to build a probe that has low 19F background and excellent separation of 1H and 19F signals. We determine the principle components of the chemical shift anisotropy tensor of 5-fluoroindole-3-acetic acid (5FIAA) and 5-fluorotryptophan. We also solve the crystal structure of 5FIAA, determine the orientation dependence of the chemical shift of a single crystal of 5FIAA, and predict the 19F chemical shift based on the orientation of the fluorine in the crystal. The results show that this 1H/19F probe is suitable for solid-state NMR experiments with low amounts of biological molecules that have been labeled with 19F.     

NMR difference probe: a dual-coil probe for NMR difference spectroscopy

A unique probe designed to acquire nuclear magnetic resonance difference spectra of two samples is presented. The NMR Difference Probe contains two sample coils in a resonant circuit that switches between parallel excitation and serial acquisition to cancel common signals such as solvent peaks and impurities. Two samples containing a common analyte, acetonitrile, were used to demonstrate signal cancellation in a difference spectrum collected with a single pulse experiment. The cancellation was over 96% effective. The approach described has applications in the areas of solvent subtraction and spectral simplification.     

Frequency-dependent protonic conduction and high resolution 1H NMR of KDP around 298 K

Measurements of the dc conductivity, polarisation conductivity, and high resolution ¹H NMR have been carried out on KDP (KH₂PO₄) around 298 K. Comparisons between the different results are reported and an interpretation is proposed in order to clarify the protonic motion within the bulk material.     

High resolution 31P NMR study of octacalcium phosphate

We have assigned the (31)P high-resolution spectrum of octacalcium phosphate by (31)P double quantum and HETCOR spectroscopy. The (31)P peaks at -0.2, 2.0, 3.3 and 3.7 ppm are assigned to P5/P6, P3, P2/P4 and P1, respectively. Our data reveal that substantial amount of the PO(4)(3-) groups at the P2 and P4 sites have been transformed to HPO(4)(2-) in our octacalcium phosphate sample.     

High resolution optical image restoration for ground-based large telescope using phase diversity speckle

Phase diversity speckle (PDS) is an image restoration technique which is based on the idea of phase diversity (PD). It uses multi-frame short-exposure image sequence to calculate their corresponding wave-front information. Each image pair consists of two images collected by two cameras at the same time with one in focus and the other with known defocus value. Multi-frame processing can significantly improve the target signal to noise ratio, and decrease noise influence. In this paper, based on the principle of pupil Fourier imaging, by adjusting the pupil size, we get different scales of the optical point spread function (PSF). Also, we analysis different camera noise distribution channels, location differences and other factors to optimize the objective evaluation function, and this can reduce the computational complexity and improve the processing speed of image restoration. In the indoor environment, we build optical platform, and use multi-frame phase diversity speckle to make experiment under different turbulence conditions. The experimental results show that the image restoration effect of the proposed method is close to the diffraction limit.     

High resolution spectroscopy using photodeflection

Isotope separation by laser deflection of an atomic beam, combined with simultaneous mass spectroscopy, has been used to determine optical frequency shifts and to assign mass numbers to all components of the $\text{Ba 6s}{}^2{}^1\text{S}{}_0\text{?6s6p}{}^1\text{P}{}_1$ 5536 Å resonance. Several components which cannot be resolved optically without the use of enriched samples, were resolved with the technique described. They are ${}^{135}\text{Ba}\text{(F=}\text{5}\text{2}\text{)}$ at 120 MHz, ¹³⁶Ba at 128 MHz and ¹³⁴Ba at 138 MHz.     

NMR probe of phase segregation in electron doped mixed valence manganites

A 55Mn and 139La NMR study of La0.35Ca0.65MnO3 is reported. The zero field 55Mn spectra consist of two lines centered at 290 and 375 MHz. Their behavior under an applied magnetic field makes it possible to attribute them to regions of antiferromagnetically and ferromagnetically coupled Mn spins, respectively. This gives evidence for the existence of electronic phase segregation of microscopic ferromagnetic regions of double exchange coupled Mn spins over a charge ordered antiferromagnetic background. The behavior of these ferromagnetic regions in the applied magnetic field is related to the magnetoresistive properties of the manganites.     

High resolution off-magic-angle spinning NMR for cholesteric liquid crystals

High resolution NMR of cholesteric liquid crystals is realized by off-magic-angle spinning (OMAS). Using the average potential theory, it is shown that the pitch axes of a cholesteric liquid crystal with a positive (negative) magnetic susceptibility anisotropy are aligned along the spinning axis with an OMAS angle larger (smaller) than the magic angle without any distortion of the helical structure, which is untwisted or distorted by the static magnetic field in some static samples. Hence, the line broadening due to the anisotropies of chemical shifts and/or quadrupole couplings is removed, while information of the anisotropies in cholesteric alignments can be obtained from the line positions. A detailed theoretical analysis of effects of spinning frequency and molecular diffusion along the pitch axis on the linewidth is given, predicting that the resolution is improved greatly at a spinning frequency much higher than the rotational diffusion coefficient. These theoretical results are verified by ¹³C OMAS experiments on a cholesteric liquid crystal of p-ethoxybenzyl-p-[(S)-2- methylbutyl]aniline (EBMBA) and cholesteric mixtures of p-methoxybenzylidene-p-n-butylaniline (MBBA) and cholesteryl chloride (CC).     

Experimental damage thresholds of a laser suppression imaging system using a cubic phase plate

The development of laser systems leads to an increasing threat to photoelectric imaging sensors. A cubic phase plate wavefront coding imaging system is proposed to reduce the risk of damage owing to intense laser radiation. Based on the wavefront coding imaging model, the diffracted spot profile and the light intensity distribution on the observation plane are simulated. An experimental device is set up to measure the laser-induced damage thresholds and investigate the morphology of laser-induce...     

Low-E probe for (19)F-(1)H NMR of dilute biological solids

Sample heating induced by radio frequency (RF) irradiation presents a significant challenge to solid state NMR experiments in proteins and other biological systems, causing the sample to dehydrate which may result in distorted spectra and a damaged sample. In this work we describe a large volume, low-E (19)F-(1)H solid state NMR probe, which we developed for the 2D (19)F CPMG studies of dilute membrane proteins in a static and electrically lossy environment at 600MHz field. In (19)FCPMG and related multi-pulse (19)F-(1)H experiments the sample is heated by the conservative electric fields E produced in the sample coil at both (19)F and (1)H frequencies. Instead of using a traditional sample solenoid, our low-E (19)F-(1)H probe utilizes two orthogonal loop-gap resonators in order to minimize the conservative electric fields responsible for sample heating. Absence of the wavelength effects in loop-gap resonators results in homogeneous RF fields and enables the study of large sample volumes, an important feature for the dilute protein preparations. The orthogonal resonators also provide intrinsic isolation between the (19)F and (1)H channels, which is another major challenge for the (19)F-(1)H circuits where Larmor frequencies are only 6% apart. We detail steps to reduce (19)F background signals from the probe, which included careful choice of capacitor lubricants and manufacture of custom non-fluorinated coaxial cables. Application of the probe for two-dimensional (19)F CPMG spectroscopy in oriented lipid membranes is demonstrated with Flufenamic acid (FFA), a non-steroidal anti-inflammatory drug.     

Improving the 1H indirect dimension resolution of 2D CRAMPS NMR spectra: a simulation and experimental investigation

An experimental and simulation investigation regarding the effect of various CRAMPS parameters (delays interleaved with the decoupling shape, z-rotation symmetry and offset frequency) on the DUMBO decoupling performance is presented using two model compounds, glycine and tyrosine·HCl. Although the conclusions of this work may be extended to the other homonuclear-decoupling schemes, this work focuses essentially on the effect of adding interleaved delays to DUMBO decoupling during the indirect dimension using different 2D pulse-scheme architectures. While the simulations revealed an increasing loss of the spectral resolution with longer delays (from 0 to 6 μs), the experimental 2D (1)H DUMBO NMR correlation spectra revealed that the inclusion of delays, during the indirect dimension, improves the (1)H resolution whether the z-rotation symmetry was used or not. The best experimental spectra are obtained when z-rotation symmetry and windows are combined.     

1H NMR Detection of superparamagnetic nanoparticles at 1T using a microcoil and novel tuning circuit

Magnetic beads containing superparamagnetic iron oxide nanoparticles (SPIONs) have been shown to measurably change the nuclear magnetic resonance (NMR) relaxation properties of nearby protons in aqueous solution at distances up to approximately 50 microm. Therefore, the NMR sensitivity for the in vitro detection of single cells or biomolecules labeled with magnetic beads will be maximized with microcoils of this dimension. We have constructed a prototype 550 microm diameter solenoidal microcoil using focused gallium ion milling of a gold/chromium layer. The NMR coil was brought to resonance by means of a novel auxiliary tuning circuit, and used to detect water with a spectral resolution of 2.5 Hz in a 1.04 T (44.2MHz) permanent magnet. The single-scan SNR for water was 137, for a 200 micros pi/2 pulse produced with an RF power of 0.25 mW. The nutation performance of the microcoil was sufficiently good so that the effects of magnetic beads on the relaxation characteristics of the surrounding water could be accurately measured. A solution of magnetic beads (Dynabeads MyOne Streptavidin) in deionized water at a concentration of 1000 beads per nL lowered the T(1) from 1.0 to 0.64 s and the T2 * from 110 to 0.91 ms. Lower concentrations (100 and 10 beads/nL) also resulted in measurable reductions in T2 *, suggesting that low-field, microcoil NMR detection using permanent magnets can serve as a high-sensitivity, miniaturizable detection mechanism for very low concentrations of magnetic beads in biological fluids.