Divalent cations affect chain mobility and aggregate structure of lipopolysaccharide from Salmonella minnesota reflected in a decrease of its biological activity

AbstractThe physicochemical properties and biological activities of rough mutant lipopolysaccharides Re (LPS Re) as preformed divalent cation (Mg2+, Ca2+, Ba2+) salt form or as natural or triethylamine (Ten+)-salt form under the influence of externally added divalent cations were investigated using complementary methods: Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopic (FT-IR) measurements for the β↔α gel to liquid crystalline phase behaviour of the acyl chains of LPS, synchrotron radiation X-ray diffraction studies for their aggregate structures, electron density calculations of the LPS bilayer systems, and LPS-induced cytokine (interleukin-6) production in human mononuclear cells. The divalent cation salt forms of LPS exhibit considerable changes in physicochemical parameters such as acyl chain mobility and aggregate structures as compared to the natural or monovalent cation salt forms. Concomitantly, the biological activity was much lower in particular for the Ca2+- and Ba2+-salt forms. This decrease in activity results mainly from the conversion of the unilamellar/cubic aggregate structure of LPS into a multilamellar one. The reduced activity also clearly correlates with the higher order – lower mobility – of the lipid A acyl chains. Both effects can be understood by an impediment of the interactions of LPS with binding proteins such as lipopolysaccharide-binding protein (LBP) and CD14 due to the action of the divalent cations

ION BEAM SURFACE INTERACTION AT GRAZING INCIDENCE

Various observations concerning the interaction mechanism of ion beam surface interaction at grazing incidence (IBSIGI) are summarized and discussed. Examples for the application of IBSIGI in high resolution spectroscopy of atomic physics are presented and the use of IBSIGI for the universal production of nuclear spin polarized ion beams is demonstrated.Des observations concernant le mécanisme d'interaction des ions avec une surface inclinée (IBSIGI) sont présentées et discutées. Des exemples pour l'application de IBSIGI dans la spectroscopie atomique à haute résolution sont présentés et l'usage de IBSIGI pour la production universelle des faisceaux ioniques avec polarisation du spin nucléaire est démontré

Hyperfine structure of 14NIII 2p 2P3/2 by quantum beats after ion surface interaction at grazing incidence

Applying a modified quantum beat method, the hyperfine splittings of 14NIII 2p 2P3/2 are determined to ν 3/2,5/2 = (252.0 ± 1.1) MHz and ν1/2,3/2 = (126.2 ± 0.4) MHz. From the frequencies we deduce the nuclear electric quadrupole moment of 14N Q (14N) = (19.4 ± 0.9) mb and the quadrupole coupling constant for the 2p-electron in 14NIII 1s22s 22p 2P3/2 : e Q qat = - (16-6 ± 0.6) MHz.Nous avons mesuré, par une éthode de battements quantiques, les écarts de structure hyperfine de 14NIII 2p 2P3/2ν3/2,5/2 = (252,0 ± 1, 1) MHz et ν1/2,3/2 = (126,2 ± 0,4) MHz. De ces fréquences on déduit le moment quadrupolaire électrique du noyau Q (14N) = (19,4 ± 0,9) mb et la constante de couplage quadrupolaire pour l'électron 2p de 14NIII 1s22s22p 2P3/2 : e Q qat = -(16,6 ± 0,6) MHz