Haggai Gilboa

Lithium nuclear magnetic resonance measurements in halotolerant bacterium Ba1

Abstract Measurements of relaxation times T 1 and T 2 , were carried out on a high-salt- and low-salt-grown bacterial pellets of halotolerant bacterium B a 1 . In our measurements, T 1 ⪢ T 2 and both were frequency-independent. In the high-salt-grown pellet the relaxation time values were much shorter than in the case of low-salt growth medium. Intensity measurements show that only 55% of the lithium in the high-salt pellet is detected; for the low-salt pellet almost all the lithium is detected. Growth measurements were carried out on the B a 1 . It is suggested that there is some form of adaptation of the bacteria to the growth medium. The adaptation is reflected in the lithium NMR results.

Heat-bath cooling of spins in two amino acids

Abstract Heat-bath cooling is a component of practicable algorithmic cooling of spins, an approach which might be useful for in vivo 13 C spectroscopy, in particular for prolonged metabolic processes where substrates that are hyperpolarized ex-vivo are not effective. We applied heat-bath cooling to 1, 2- 13 C 2 -amino acids, using the α protons to shift entropy from selected carbons to the environment. For glutamate and glycine, both carbons were cooled by about 2.5-fold, and in other experiments the polarization of C1 nearly doubled while all other spins had equilibrium polarization, indicating reduction in total entropy. The effect of adding Magnevist®, a gadolinium contrast agent, on heat-bath cooling of glutamate was investigated.

Double quantum sodium NMR studies of the halotolerant Ba1 bacterium

Abstract The relaxation times T 1 , T 2f and T 2s , of sodium in the cytosol of the halophilic halotolerant bacterium Ba 1 isolated from the Dead Sea were measured. T 2f and T 2s , were separated by using the double quantum filtering method. The measurements were carried out at two different concentrations of the growth medium. From the spectral density ratio it seems that the microenvironment in the cytosol affecting the sodium relaxation times is similar for the two different growth media. It seems that the bacteria keep a constant microenvironment in the cytosol.

Relaxation time measurements and molecular dynamics of dipalmitoyl-α-lecithin in the solid phase

The relaxation times T1 and TD were measured for dipalmitoyl-L-α-lecithin and dipalmitoyl-DL-α-lecithin at various temperatures. It was possible to separate the contribution of the slow motions to the relaxation rates from the fast ones. For some types of motions the activation energies could be estimated.

Nuclear magnetic resonance studies of cesium-133 in the halophilic halotolerant bacterium Ba1. Chemical shift and transport studies †

Ba1 bacteria (Holomonas israelensis ) were grown on different salt concentrations 0.2–4 M. When the cells were transferred to a medium containing 25 mM CsCl without potassium there was an uptake of cesium by the cells. The intracellular cesium signal was shifted from the cesium signal in the medium without the use of a shift reagent. The shift was depended on the salt concentration in the growth medium. The intracellular cesium shift showed a much smaller dependence on the concentration of salts in the medium than the extracellular cesium; the same results were detected for cells grown on a medium containing 25 mM CsCl. The cesium transport through the cell membrane was mostly by active transport. The cesium concentration in the cell was higher than that of the medium, ∼100 mM intracellular concentration compared to 25 mM in the medium. The first order constants for influx or efflux of cesium were from 2 × 10−4 and up to 24 × 10−4 /min for the different medium concentrations.

Sodium binding in Halobacterium halobium measured by the nuclear magnetic resonance technique

Abstract Relaxation time measurements T 1 and T 2 of sodium in Halobacterium halobium pellets were carried out at two frequencies. From those measurements, combined with intensity measurements of the sodium in the system, estimation of the properties of the sodium ions in the system was carried out. It is suggested that three types of sodium ions are present in the bacterial pellet. (A) The extracellular sodium with properties of free solution and (B) sodium which is in the pericellular volume between the cell wall and the cell membrane. There is an exchange between type A and type B sodium. The type B sodium has ( e 2 qQ )/ h = 3.7 · 10 7 rad/s, τ cB = 5.2 · 10 −6 s and τ B = 1 · 10 −3 s. The sodium of type C is bound inside the cell and undetected. Its concentration inside the cell is assumed to be 1.9 M.

The determination of intracellular sodium concentration in human red blood cells: Nuclear magnetic resonance measurements

The intracellular sodium concentration and intracellular volume of human red blood cells were determined from 23Na and 1H NMR spectra. It is shown that sodium dissolved in the intracellular water has a concentration higher than that previously published. The intracellular sodium concentration measured was 11.4 +/- 3.1 mM. A comparison of different NMR methods used to determine sodium concentration is given.

Proton magnetic relaxation in intact mice lungs during oxygen exposure

Summary Proton spin lattice relaxation times have been determined in mice lungs during exposure to hyperbaric oxygen. The water protons within the lungs of the oxygen-exposed mice relax slower than those in control animals. The rate of changes followed approximately the rate of water accumulation within the lungs. The results are interpreted in terms of a hypothesis that a minor fraction of the protons in the cell is distributed over states of low mobility and exchanges rapidly with a major fraction which exhibits shorter correlation time. The change in water relaxation rates in lungs following the exposure to oxygen is attributed to the difference in the distribution ratio of water between the hydration and free states.

Nuclear magnetic resonance studies of Ba1 bacterium and some model systems

Lithium NMR relaxation times of some model systems and E. coli cells in high LiCl concentration were measured. The lithium NMR relaxation times were compared to the relaxation times in the holotolerant bacterium Ba1 (Goldberg, M., Risk, M. and Gilboa, H. (1983) Biochim. Biophys. Acta 763, 35-40). Complementary studies of the water protons NMR relaxation times were carried out. It is suggested that the lithium in the H.S. Ba1 bacterium is occulated in small pores of the cell envelope.