Norma Wade-Jardetzky

Extent of intracellular pH changes during H(+) extrusion by maize root-tip cells.

Abstract31P-Nuclear-magnetic-resonance spectra of maize (Zea mays L.) root tips, that had been induced to extrude large amounts of H+ in response to fusicoccin (FC) in the presence of potassium salts, indicate that the cytoplasmic pH does not become higher than that of controls. In fact, the cytoplasmic pH may become slightly (approx. 0.1 pH unit) lower in cells extruding H+. Estimations of the buffer capacity of the cells show that without active intracellular pH regulation, H+ extrusion caused by FC would cause the intracellular pH to rise by at least 0.6 pH unit h-1. Our results indicate that intracellular pH is tightly regulated even during extreme rates of acid extrusion, and that a rise in cytoplasmic pH is not the signal linking H+ extrusion with enhanced organic-acid synthesis or other intracellular responses to H+ pumping.

Differential mobility of the N-terminal headpiece in the lac-repressor protein.

It is shown by resolution enhancement and relaxation studies of the 360 MHz 1H nuclear magnetic resonance spectra of the lac-repressor of Escherichia coli and the two fragments derived from it by limited tryptic digestion (the N-terminal headpiece and remaining T-core) that the majority of the relatively mobile residues in the intact lac-repressor are located in the headpiece. Although nuclear magnetic resonance data clearly indicate that the headpiece is a highly structured entity, even when isolated, it is a more mobile part of the repressor than the T-core.

Continuous-flow NMR culture system for mammalian cells

A continuous-flow NMR culture system for mammalian cells has been developed on which 31P-NMR experiments under complete and strictly physiologic conditions have been performed. Observations on the response of the cellular metabolism to stresses such as starvation, low temperature and changes in environmental pH monitored by 31P-NMR are reported. The response of the intracellular pH relative to the external pH of the growth medium is studied. We find that under the experimental conditions used there exists a delta pH varying between less than 0.2 and more than 0.6 pH units. These results are compatible with those obtained using other techniques.

Comparison of protein structures by high resolution solid state and solution NMR

Comparisons of the crystal and solution structure of proteins are usually based on circumstantial evidence. Direct structure determination is possible only in the solid state, and to make the comparison, various spectroscopic findings (CD, ORD, NMR), or results of chemical modification experiments are tested for consistency with the known crystal structure [ 11. To be rigorous a comparison should be based on data obtained by the same method on the same object under two different conditions. Here we present an experiment which makes such a direct comparison of the crystal and solution structure of proteins by high resolution “C NMR.

High resolution 1H NMR of a selectively deuterated analog of the lac repressor

Abstract A selectively deuterated tyrosine analog of the lac repressor has been prepared and its 1 H spectra examined at 360 MHz. Spectral changes observed in the presence of Tris·HCl buffer and the inducer isopropyl-β- d -thiogalactoside suggest the existence of different conformational forms.

Changes in the phosphorus metabolism of a diving turtle observed by 31P-NMR

Abstract Relative concentrations of phosphates have been measured by 31 P-NMR on the heads of intact healthy freshwater turtles capable of sustaining dives of more than 4 h with complete subsequent recovery and turnover rates under conditions of reversible hypoxia have been determined by NMR using saturation transfer techniques.

On the interaction of the lac repressor headpiece with nucleic acids

The Zac repressor protein has been extensively studied in an attempt to understand the interactions which allow recognition of and extremely tight binding to the lac operator region of DNA [ 11. Genetic experiments have suggested that an important DNA binding region is in the N-terminal region of the repressor, e. g., changes of tyrosine 17 and to a lesser extent tyrosine 7 result in loss of DNA binding capability. A 5 1 amino acid headpiece (HP) can be cleaved from the repressor’s N-terminus [2]. This fragment retains the capability to bind both specifically to operator DNA and non-specifically, though the binding constants are reduced from those for the intact repressor [3]. NMR experiments have shown that this headpiece exists as a mobile domain in the intact repressor which has the same structure as the isolated peptide [4,5]. NMR has also shown that this segment has extensive secondary and perhaps tertiary structure [6]. Photo-CIDNP experiments on HP have shown that tyrosines 7 and 17 and histidine 29 have reduced accessibility for reaction with the flavin dye when DNA is bound [7]. We have examined the binding of HP to a short synthetic DNA segment by high resolution NMR in both Hz0 and ‘Hz0 solution.

NMR AS A NONINVASIVE MONITORING TECHNIQUE IN PHYSIOLOGY AND MEDICINE

Publisher Summary Nuclear magnetic resonance (NMR) is a spectroscopic method based on the fact that atomic nuclei in bulk matter absorb radiofrequency radiation when placed in a magnetic field. The absorption signal can be picked up by a tuned coil surrounding the sample and displayed after manifold amplification on any suitable recording device. The frequency at which absorption is observed depends on the strength of the imposed magnetic field. This chapter discusses the advantages of NMR as a noninvasive monitoring technique in physiology and medicine. The first recorded physiological observations made by NMR were on blood or its cellular components. Thus far, in vivo NMR studies have dealt largely with cell suspensions or perfused organs. Only one report of a 31P spectrum obtained on a live animal, the head of a mouse, has appeared in the literature (Chance, et al, 1978). The chapter discusses whether NMR is sensitive to reversible metabolic and mild physiological perturbations.