Manganese(II) as magnetic relaxation probe in the study of biomechanisms and of biomacromolecules

Niccolai, Neri; Tiezzi, Enzo; Valensin, Gianni

doi:10.1021/cr00050a002

Cited by 55 publications

(20 citation statements)

References 75 publications

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“…There are six well-defined hfs lines, as in MnSO4(aq), but there are significant differences. These cell samples exhibit spectral characteristics similar to those which have been observed previously for Mn2+ ions bound to macromolecules in biological systems (33). The lines are not as symmetrical as those of MnSO4(aq), and both the line widths, AHPI and the intensities of lines 2, 3, 4, and 5 relative to those of lines 1 and 6 are decreased, with the central lines 3 and 4 being the least intense.…”

Section: Resultssupporting

confidence: 78%

Acquisition of manganous ions by mutans group streptococci

et al. 1993

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The cariogenic bacteria Streptococcus sobrinus and S. cricetus were shown to have an absolute requirement for manganous ion in order to bind glucans or to adhere to glass in the presence of sucrose. The bacteria possessed a reasonably high affinity transport system for 54Mn2 , yielding a Km of about 12 ,M. The Vmax for uptake of 54Mn2+ in S. sobrinus was increased when the bacteria were grown in Mn-depleted medium, but the Km remained the same. There was no evidence for two Mn2+ uptake systems, commonly observed for many bacteria. Ions such as Ca2+, Co2+, Co3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, and Zn2+ did not inhibit the uptake of 54Mn2+ by the bacteria, although Cd21 was a potent inhibitor. Fractionation experiments showed that manganese was distributed in protoplasts (67%) and in the cell wall (33%). Approximately 80%o of the 54Mn2+ in S. sobrinus was rapidly exchangeable with nonradioactive Mn2+. Electron spin resonance experiments showed that all of the manganese was bound or restricted in mobility. Proton motive forcedissipating agents increased the acquisition of 54Mn2+ by the streptococci, probably because the wall became more negatively charged when the cell could no longer produce protons.Bacteria use trace metals as prosthetic groups for numerous enzymes. For many bacteria, manganous ion is essential for growth and division. Requirements for manganese occur in both gram-positive and gram-negative bacteria. Archibald (4) has reviewed the role of manganese in microbial metabolism. Drake et al. (16) found that expression of the glucanbinding lectin (GBL) of the mutans group streptococci depends on the presence of manganous ion in the growth medium. More recent work by showed that growth supplements of citrate or lactate prevented expression of GBL. The effects of citrate and lactate were probably due to the binding of manganese by the organic acids, effectively starving the cells for the metal ion. The GBL of the mutans group streptococci may function to promote their sucrose-dependent adhesion to and accumulation on the surfaces of teeth (10,11,21,22,26,27), an initial step in dental caries formation.Several lines of evidence point to a role of manganese in dental caries (6,7,9,12), although that role has yet to be defined. Adhesion to surfaces seems to favor the growth and survival of bacteria. If manganous ion contributes to the ability of streptococci to adhere, it would be expected that the bacteria possess efficient means of acquisition of the ion. In this study, it is shown that Streptococcus sobrinus and S. cricetus, both members of the mutans group of streptococci, possess a highly specific uptake system for manganous ion. Trypticase soy broth (TSB; BBL Microbiology Systems, Cockeysville, Md.). In order to eliminate potential sucrose or a-1,6-glucan contaminants, the medium was treated with yeast invertase (1 mg/g of dry medium; Sigma Chemical Co., St. Louis, Mo.) and fungal dextranase (1 mg/g of dry medium; Sigma) at 50°C for 3 h prior to autoclaving. Treatment of the medium with the enzyme...

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Section: Resultssupporting

confidence: 78%

Acquisition of manganous ions by mutans group streptococci

et al. 1993

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“…Determination of T I measurements of the relaxation times, T1, were done by the inversion-recovery pulse sequence ?r/2-r-r. The delay 7 vaned from T~ to 4 0~~ (1 5 6 7 0 < 50 ms).…”

Section: Methodsmentioning

confidence: 99%

“…Manganese addition. The influence of paramagnetic substance on the proton relaxation was studied by adding MnC12, a widely used contrasting agent (7), to the Tyrode solution at different concentrations. The variations of the spin-lattice relaxation rate and those of the spin-spin relaxation rate with Mn2+ concentration have been fitted by a linear plot according to…”

Section: Methodsmentioning

confidence: 99%

NMR compartmentalization of free water in the perfused rat heart

Mauss

Grucker

Fornasiero

et al. 1985

Magnetic Resonance in Med

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Spin-lattice (T1) and spin-spin (T2) relaxation times have been measured on perfused rat hearts under two experimental conditions. T1 exhibits a monoexponential decay. On the other hand T2 has a decay with two components: a short one T2s and a long one T2l. These facts have been discussed according to cross-relaxation and a bicompartmentalization of tissue assuming a slow exchange model for spin-spin relaxation and a fast exchange model for spin-lattice relaxation. Increasing the osmotic pressure of the perfusion solution decreased the absolute density proton of the T2s compartment reflecting the loss of its water content. The paramagnetic ion manganese diminishes the values of T1 and those of the long component T2l without affecting its short component. Therefore the short component could be assigned to intracellular and the long component to extracellular free water. The extracellular T2 (459 ms) is approximatively 10-fold higher than the intracellular T2 (45 ms). With images of "pure T2" such a difference could be useful to enhance the contrast between organs and the surrounding liquid or between organs with different water compartmentalization.

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“…2, the high spin manganese gives six stable complexes with glycine. According to E a values in Table 2, for this spin multiplicity the absolute minimum corresponds to the bicoordinated complex (6). In this complex, Mn 2+ interacts with the two oxygen atoms of the…”

Section: Spinmentioning

confidence: 99%

“…Manganese proteins, for example, are important in the oxygen evolution catalyzed by the proteins of photosynthetic reaction center and are involved in the metabolism of amino acids and proteins [5]. In addition, manganese as a divalent metal ion plays a significant role in RNA structure and catalysis [6,7]. In many manganese proteins the manganese is in the II oxidation state [4].…”

Section: Introductionmentioning

confidence: 99%