Study of the interaction between lanthanide ions and a supported bilayer lipid membrane by cyclic voltammetry and ac impedance

The interaction of lanthanide ions with a supported bilayer lipid (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine) membrane (sBLM) was investigated by cyclic voltammetry and ac impedance spectroscopy in this paper, Lanthanide can affect the conformation of the supported bilayer lipid membrane and cause pore formation. Through the pores, Fe(CN)(6)(3) (4) can reach the electrode surface and show its redox behaviour. Furthermore the redox currents or Fe(CN)(6)(3) (4) increased with increasing concentration of lanthanides and leveled off at 1.2 muM for Eu3+. The interaction ability of three lanthanides with sBLM follows the sequence: Eu3+ > Tb3+ > La3+.

Calculation of the electrostatic energy H-e(fd) on 4f(N-1)5d configuration of lanthanide ions

In LS coupling, the energy expressions of H-e(fd) of the chief low-energy levels of 4f(N-15)d (n < 9) configuration ions are calculated. H-e(fd) can be parameterized with F-K (k=2,4) and G(K)(k=1,3,5). f(k) and g(k), which are coefficients, times the corresponding parameter FK and GK leads to the energy expressions of H-e(fd).

Networks with hexagonal circuits in co-ordination polymers of metal ions (Zn-II, Cd-II) with 1,1 '-(1,4-butanediyl)bis(imidazole)

Three new compounds, [ZnL1.5(H2O)(SO4)]. 6H(2)O 1, [ZnL1.5(H2O)(2)][NO3](2). 2H(2)O 2 and [CdL1.5(H2O)(2)(SO4)]. 4H(2)O 3 were obtained from self-assembly of the corresponding metal salts with 1,1'-(1,4-butanediyl)bis(imidazole) (L). In both 1 and 2 zinc ion is five-co-ordinated, showing a less-common trigonal bipyramidal co-ordination polyhedron, while cadmium ion of 3 is six-co-ordinated with a common octahedral arrangement. The sulfate ions of 1 and 3 are co-ordinated, however the nitrate ions of 2 are not. Each of the three compounds is composed of a (6, 3) network with the hexagonal smallest circuit containing six metal ions and six L; each L is co-ordinated to two metal ions, acting as a bridging ligand. In 1 the 2-D sheet of (6, 3) networks is interpenetrated in an inclined mode by symmetry related, identical sheets to give an interlocked 3-D structure, while the (6, 3) networks of both 2 and 3 stack in a parallel fashion to construct frameworks having channels.

Structure of coordination polymer, [Zn(bipy)(H2O)(3)SO4] center dot 2H(2)O (bipy=4,4 '-bipyridine)

The crystal of the title compound (C10H18N2O9SZn M-r=407.69) belongs to the hexagonal system, space group P 6(5) with cell parameters: a=11.411 (2), c=20.908(4) Angstrom, V=2357.7(7) Angstrom(3), Z=6, D-c=1.723g/cm(3), F(000)=1260, mu(MoKa)=1.743mm(-1). The final R and omega R factors are 0.072 and 0.178 respectively for 1335 observed reflections. in the structure, zinc ions are bridged by 4,4'-bipyridine to form infinite chains. The sheets containing parallel chains stack along a 65 screw axis to give a helical staircase motif. The helical structure is mainly controlled by the hydrogen bonds.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

Theoretical studies of nonlinear optical properties of compounds K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd)

K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd) is a special type of frequency doubling compound, whose crystal structure exhibits a scarcity of fluorine ions. This leads to two different coordination polyhedrons in the general position of K(2) atoms: [K(2)O6F(1)(2)F(2)] and [K(21)O6F(1)(2)] in a 2/1 ratio. The chemical bonding structures of all constituent atoms of the compound K4Gd2(CO3)(3)F-4 (KGCOF) are comprehensively studied; moreover, the relationship between the chemical bonding structure and the nonlinear optical (NLO) properties is investigated from the chemical bond viewpoint. The theoretical prediction of the NLO tensor coefficient d(11) of KGCOF is in agreement with experimental observation. Theoretical analyses show that the nonlinearity of this crystal type mainly originates from K-O bonds. In addition, the correlation between the NLO tensor d(11) and the refractive index n(0) of KGCOF is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)07506-X].

P-6(7/2)-excited-state decay mechanism and energy-transfer processes in KMgF3 : Eu2+ and KMgF3 : EuX (X = Gd, Ce, Cr)

A four-level decay model in KMgF3:Eu2+ is proposed. The decay profiles of the P-6(7/2) excited state of Eu2+ are biexponential, and the physical implication of each term in the fit equation responsible for the model is interpreted. The evidence obtained spectroscopically for supporting the model is presented. A new method to study energy transfer between Eu2+ and X3+ in KMgF3:Eu-X (X = Gd, Ce, Cr) is established on the basis of the proposed model.

Formation of a self-assembled monolayer of 2-mercapto-3-n-octylthiophene on gold

Monolayer assembly of 2-mercapto-3-n-octylthiophene (MOT) having a relatively large headgroup onto gold surface from its dilute ethanolic solutions has been investigated by electrochemistry. An electrochemical capacitance measurement on the permeability of the monolayer to aqueous ions, as compared with its alkanethiol counterpart [CH3(CH2)(9)SH (DT)] with a similar molecular length, shows that the self-assembled monolayers (SAMs) of MOT can be penetrated by aqueous ions to some extent. Furthermore, organic molecular probes, such as dopamine, can sufficiently diffuse into the monolayer because a diffusion-limited current peak is observed when the dopamine oxidation reaction takes place, showing that the monolayer is loosely packed or dominated by defects. But the results of electron transfer to aqueous redox probes (including voltammetry in Fe(CN)(6)(3-/4-) solutions and electrochemical ac impedance spectrum) confirm that the monolayer can passivate the gold electrode surface effectively for its very low ratio of pinhole defects. Moreover, a heterogeneous patching process involving addition of the surfactants into the SAMs provides a mixed or hybrid membrane that has superior passivating properties. These studies show that the MOT monolayer on the electrode can provide an excellent barrier for hydrated ionic probe penetration but cannot resist the organic species penetration effectively. The unusual properties of the SAMs are attributed to the entity of the relatively large thiophene moiety between the carbon chain and the thiol group.

Mass spectrometric studies of metallofullerene

The endrohel metallofullerene, Gd@C-82, Gd@C-80, Gd-2@C-80 were synthesized by using K-H method. The technique of two-step of high pressure and high temperature extraction with 1, 3, 5-trimethylbenzene (first step) and pyridine(second step) has been successfully utilized to extract metallofullerene of Gd@C-82 The gas-phase negative ions of fullerenes C-n(n= 60, 70, 78, 82, 84...) and metallofullerene (Gd@C-82) have been studied by the ESI-MS, REC-MS and MALDI-TOF-MS. The differences among the mass spectra of ESI-MS, REC-MS and MALDI-TOF-MS have been observed and explained. In contrast to the empty fullerene C-82 , the metallofullerene Gd@C-82 should have a larger HOMO-LUMO gap. Experimental results suggest that Gd@C-82 is polarized and Gd3+ located in the off-center position of C-82 cage after Gd3+ is trapped into C-82 cage.

Studies on the transport of lanthanides ions through the membrane of human erythrocyte in vitro by ICP-MS

A method was developed for the determination of lanthanum in the cytoplasm of human erythrocytes after they were incubated in lanthanum nitrate or citrate solutions. The lanthanum concentration in the cytoplasm of incubated erythrocytes is much higher than that in normal erythrocytes. It is suggested lanthanum can transport through the membrane of erythrocyte in vitro. Solutions containing chelator are unsuitable to be washing buffer in the investigation.

Study of energy transfer in KMgF3 : Eu-X (X = Gd, Cr, Ce) by the decay model of P-6(7/2) exited state of Eu2+

Energy transfer processes between Eu2+ and Gd3+, Cr3+, Ce3+ ions in KMgF3, which are difficult to study spectroscopically, have been investigated by using the proposed four-level decay model of the P-6(7/2) excited state of the Eu2+ ion. Gd3+ and Ce3+ transfer its energy to the vibronic transition of the P-6(7/2) --> S-8(7/2) transition of Eu2+, whereas Cr3+ receive energy from Eu2+ via the d-d interaction. The energy transfer from the Eu2+ 4f(6)5d level to the Ce3+ 4f5d state is observed spectroscopically, and the energy transfer mechanism is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Investigation on moleculare and crystal structures of metal complexes with aminopolycarboxylic acids (VII) - Syntheses and structure determination of Na-3[Hg (I) (edta) C1] center dot 6H(2)O

In this paper we describe the moleculare and crystal structures of the Na-3[Hg( II )(edta)Cl] . 6H(2)O (edta=ethylenediamine-N,N,N',N'-tetraacetate). The crystal data are as follows: orthorhombic, a=8. 083 (2) Angstrom , b=13. 870(3) Angstrom , c=38. 617(5) Angstrom , v=4329. 4 (13) Angstrom(3) , Z=8, Dc= 1. 798 g . cm(-3), mu=5. 564 mm(-1), P(000)=2280, R=0. 0317 and R-w=0. 0731 for 3883 unique reflections. In complex, the complex anion [Hg ( II ) (edta)Cl](3-) has a seven-coordination structure like a mono-capped trigonal-prism (C-2v-MTP) in which the edta(4-) acts as a hexadentate ligand with four O atoms and two N atoms and a Cl- caps a quadrilateral face as a seventh ligand. It can be known that the Hg2+ which has a d(10) electronic structure can form a high-coordinate compound with a hexadentate ligand (edta) because it has a big ionic radius.

The change of Eu3+-surroundings in the system Al2O3-B2O3 containing Eu3+ ions

The change of Eu3+-surroundings with the Al/B ratio varying from 4.5 to 2 and Eu/(Al + B) = 0.02, was investigated through X-ray diffraction, infrared spectra, excitation and emission spectra, and phonon sideband. The results show coexistence of the crystal phase Al18B4O33 and the amorphous phase and Eu3+ ions of the samples with the Al/B ratio from 3 to 2 are incorporated into the amorphous phase. It was also found that electron-phonon coupling strength decreases with the Al/B ratio from 3 to 2, non-radiative decay rate decreases, resulting in an increase of the Eu3+-emission intensity. (C) 1999 Elsevier Science Ltd. All rights reserved.

Studies on the interaction of rare earth ions with BSA

Studies on the bounding character of rare earth ions with borine serum albumin(BSA) are significant for understanding the state of rare earth ions in body and their effects on the structure and function of protein. The fluorescence spectrum and pH potentiometry showed consistent results of apparent complexion constant of Tb-2 . BSA. The equilibrium dialysis showed that there are two specific binding sites and more than six non-specific binding sites of RE ions onto BSA molecule with the conditional stable constants lg K-1 = 5. 157 and lgK(2) = 3. 435. Na-23 NMR studies revealed that the BSA peptide chain bound to RE ions was expanded and the mobility of its molecular backbone was increased.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of phospholipase A(2) and fibrinolytic enzyme, two enzymes obtained from Chinese Agkistrodon blomhoffii Ussurensis venom

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to analyze two enzymes, phospholipase AZ and fibrinolytic enzyme isolated from Chinese Agkistrodon blomhoffii Ussurensis venom. Using sinapinic acid as the matrix, positive ion mass spectra of the enzymes were obtained, In addition to the dominant protein [M+H](+) ions, multimeric and multiply charged ions were also observed in the mass spectra, The higher the concentration of the enzymes, the more multiply charged polymer and multimeric ions were detected, Our results indicate that MALDI-TOFMS can provide a rapid and accurate method for molecular weight determination of snake venom enzymes, Mass accuracies of 0.1 and 0.3 % were achieved by analysis of highly dialyzed phospholipase A2 and fibrinolytic enzyme, and these results are much better than those obtained using sodium dodecyl sulfate-palyacrylamide gel electrophoresis. MALDI-TOFMS thus provides a reliable method to determine the purity and molecular weight of these enzymes, which are of potential use as therapeutants, Copyright (C) 1999 John Wiley & Sons, Ltd.