Investigation of the heterogeneity of hemoglobin by cation-exchange chromatography on Bio-REX 70

The use of Bio-Rex 70 cation-exchange resin for chromatography of normal and diabetic hemoglobin provides a reproducible pattern of the "fast components". Particular attention to the choice of sample preparation, pH of elution, and the increase of ionic strength by sodium chloride linear gradients results in the separation of Hb-A1b into two components and in the isolation of a new component eluting between Hb-A1c and Hb-A0. Experiments with [3H]glucose and the colorimetric test (thiobarbituric acid) normally used to determine the extent of non-enzymatic glycosylation, as well as an increase of this component in diabetic samples compared with normoglycemic ones and a significant linear correlation with Hb-A1c, indicate that this component should be a part of the hemoglobins glucosylated on the epsilon-NH2 group of the lysines of both chains and/or the hemoglobin glucosylated on the alpha-NH2 of the valine of the alpha-chain. We propose to call this component Hb-A1x, pending confirmation of its identity. Normally Hb-A1x accounts for about 3% of Hb-A, but up to 5-7% of glucosylated hemoglobins should be confined to the early part of Hb-A0. In diabetics, the percentage of Hb-A1x rises to 4-5% and that of the other glucosylated hemoglobins increases to 12-16%.     

An automatic method for determination of glycosylated hemoglobins using low-pressure liquid chromatography

Several studies have revealed a correlation between blood levels of glucose and hemoglobin A1c (HbA1c), a minor form of hemoglobin (Hb) present at elevated concentrations in patients with diabetes mellitus. To facilitate a clinical study of the level of circulating HbA1c we have developed an automatic chromatographic system. An efficient separation of HbA1c from HbA0 and other rapid hemoglobins (HbA1a, HbA1b) was achieved on Bio-Rex-70 columns using three buffers. This system allows the daily analysis of 40 samples. The mean level of HbA1c in normal subjects was 5.4 +/- 0.4%. The method also detects the presence of elevated levels of HbF and the most frequent forms of abnormal hemoglobin (HbS, HbC).     

Molecular interactions of re-released proteins in electrophoresis of human erythrocytes

Recently, we found that hemoglobin (Hb) could be re-released from live erythrocytes during electrophoresis release test (ERT). The re-released Hb displays single-band and multiple-band re-release types, but its exact mechanism is not well understood. In this article, the protein components of the single-band re-released Hb were examined. First, the re-released band of erythrocytes and the corresponding band of hemolysate, which was used as control, were cut out from starch-agarose mixed gel. Next, proteins were recovered from the starch-agarose mixed gel by freeze-thaw method. After condensing in a vacuum freeze drier, the samples were loaded onto a 5-12% SDS-PAGE. After electrophoresis, three protein bands (16, 28.9, and 29.3 kDa) emerged from the erythrocytes re-released Hb single-band (R-R), but only one band (29.3 kDa) emerged from the corresponding hemolysate control band (H-R). Finally, these bands were analyzed by MALDI-TOF MS. The results showed that these proteins were beta-globin (16 kDa), carbonic anhydrase 1 (CA1, 28.9 kDa), and carbonic anhydrase 2 (CA2, 29.3 kDa). Because CA2 exists in both erythrocytes re-released band and hemolysate control band, we conclude that the single-band re-released Hb is mainly composed of HbA and CA1. Studying the possible interaction between HbA and CA1 will help us further understand the in vivo function of Hb.     

Characterization and ab initio XRPD structure determination of a novel silicate with Vierer single chains: the crystal structure of NaYSi2O6

The crystal structure of a sodium yttrium silicate with composition NaYSi2O6 has been determined from laboratory X-ray powder diffraction data by simulated annealing, and has been subsequently refined with the Rietveld technique. The compound is monoclinic with space group P2(1)/c and unit cell parameters of a=5.40787(2) A, b=13.69784(5) A, c=7.58431(3) A, and beta=109.9140(3) degrees at 23.5 degrees C (Z=4). The structure was found to be a single-chain silicate with a chain periodicity of four. The two symmetry dependent [Si4O12] chains in the unit cell are parallel to c. A prominent feature is the strong folding of the crankshaft-like chains within the b,c-plane resulting in intrachain Si-Si-Si angles close to 90 degrees. The coordination of the Y3+ ions by O2- is 7-fold in the form of slightly irregular pentagonal bipyramids, with oxygen atoms from four different chains contributing to the coordination polyhedron. Na+ ions are irregularly coordinated by 10 oxygens from two neighboring chains. No disorder of Na+ and Y3+ between the two nontetrahedral cation sites could be observed. Furthermore, micro-Raman spectra have been obtained from the polycrystalline material.     

An electrospray ionization mass spectrometric study of the subunit structure of the giant hemoglobin from the leech <Emphasis Type="Italic">Nephelopsis oscura</Emphasis>

The subunit structure of the giant, extracellular hexagonal bilayer (HBL) hemoglobin (Hb) from the leech Nephelopsis oscura was investigated by electrospray ionization mass spectrometry (ESI-MS) employing a maximum entropy deconvolution of its complex, multiply charged ESI spectra. The denatured unreduced Hb consisted of three monomer globin chains (M), a1 = 16535 Da, a2 = 17171 Da and a3 = 17315 Da, five nonglobin linker chains, L1 = 24512 Da, L2 = 24586 Da, L3 = 24979 Da, L4 = 25006 Da, and L5 = 25566 Da and two subunits of 32950 Da and 33125 Da. ESI-MS of the denatured, reduced Hb showed that the latter were disulfide-bonded heterodimers (D) of globin chains b1 = 16322 Da and b2 = 16499 Da with chain c = 16632 Da. Time-of-flight ESI-MS of the Hb at pH 3.8, 4.5, 5.0, 5.8 and 7.0 revealed a distribution of charge states from 32(+) to 37(+) with masses decreasing from 211 to 208.5 kDa with increase in cone voltage from 60 to 160 V, indicating the presence of a subassembly comprising 12 globin chains. The subunit composition 6M + 3D + 12h, where M = 16993 Da and D = 33004 Da are the weighted masses and h = 616.5 Da, provides a calculated mass, 208.37 kDa that is closest to 208.5 kDa. Our experimental findings are consistent with the bracelet model of HBL Hbs, verified by the recent low-resolution crystal structure of Lumbricus Hb, wherein an HBL arrangement of 12 globin dodecamer subassemblies is tethered to a central complex of 36 linker chains for a total mass of 208.37 x 12 + 24.94 x 36 = 3398 kDa.     

Globin chain separation by SDS polyacrylamide gel electrophoresis. Simple screening method for elongated hemoglobin chains

A simple method for the separation of hemoglobin chains from hemolysate or globin, by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is described. The alpha, beta, and gamma chains can be clearly separated from each other. The alpha chain has the highest mobility, the beta chain has a slower mobility than the gamma chain, while the delta chain has about the same mobility as the beta chain. Hemoglobins with elongated chains can easily be detected by this method. Tak-beta, elongated by 11 residues, moves much more slowly than betaA but is much faster than alpha Constant Spring which is elongated by 31 residues. Screening of several individuals with slow-moving hemoglobins using this method led to the finding of a case with Hb Tak-beta thalassemia and other carriers of Hb Tak.     

Wooden-Tip Electrospray Mass Spectrometry Characterization of Human Hemoglobin in Whole Blood Sample for Thalassemia Screening: A Pilot Study

Traditional analytical methods for thalassemia screening are needed to process complicated and time-consuming sample pretreatment. In recent decades, ambient mass spectrometry (MS) approaches have been proven to be an effective analytical strategy for direct sample analysis. In this work, we applied ambient MS with wooden-tip electrospray ionization (WT-ESI) for the direct analysis of raw human blood samples that were pre-identified by gene detection. A total of 319 whole blood samples were investigated in this work, including 100 α-thalassemia carriers, 67 β-thalassemia carriers, and 152 control healthy samples. Only one microliter of raw blood sample was directly loaded onto the surface of the wooden tip, and then five microliters of organic solvent and a high voltage of +3.0 kV were applied onto the wooden tip to generate spray ionization. Multiply charged ions of human hemoglobin (Hb) were directly observed by WT-ESI-MS from raw blood samples. The signal ratios of Hb chains were used to characterize two main types of thalassemia (α and β types) and healthy control blood samples. Our results suggested that the ratios of charged ions to Hb chains being at +13 would be an indicator for β-thalassemia screening.     

Quantitation of hemoglobins Bart's, H, Portland-I, Portland-II and constant spring by anion-exchange high-performance liquid chromatography

We introduce a new high-performance liquid chromatographic procedure that uses a specific anion-exchange column for the separation of hemoglobin (Hb) Bart's (gamma 4), Hb H (beta 4), Hb Portland-I (zeta 2 gamma 2), Hb Portland-II (zeta 2 beta 2), and the abnormal Hb Constant Spring (alpha 2 extended beta 2) in cord blood and adult red cell lysates. The method provides quantitative data for Hb Bart's in cord blood that correlate well with the alpha-globin gene status of the babies and can be used for an initial identification of alpha-thalassemic conditions. Quantitation of Hb Bart's from cord blood samples that are collected on filter paper and submitted as dried blood spots is unreliable. The separation of Hb H and Hb Bart's allows an evaluation of the synthesis of these two hemoglobin components in patients with Hb H disease.     

Expanding the remarkable structural diversity of uranyl tellurites: hydrothermal preparation and structures of K[UO(2)Te(2)O(5)(OH)], Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O,beta-Tl(2)[UO(2)(TeO(3))(2)], and Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2)

The reactions of UO(2)(C(2)H(3)O(2))(2).2H(2)O with K(2)TeO(3).H(2)O, Na(2)TeO(3) and TlCl, or Na(2)TeO(3) and Sr(OH)(2).8H(2)O under mild hydrothermal conditions yield K[UO(2)Te(2)O(5)(OH)] (1), Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O (2) and beta-Tl(2)[UO(2)(TeO(3))(2)] (3), or Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2) (4), respectively. The structure of 1 consists of tetragonal bipyramidal U(VI) centers that are bound by terminal oxo groups and tellurite anions. These UO(6) units span between one-dimensional chains of corner-sharing, square pyramidal TeO(4) polyhedra to create two-dimensional layers. Alternating corner-shared oxygen atoms in the tellurium oxide chains are protonated to create short/long bonding patterns. The one-dimensional chains of corner-sharing TeO(4) units found in 1 are also present in 2. However, in 2 there are two distinct chains present, one where alternating corner-shared oxygen atoms are protonated, and one where the chains are unprotonated. The uranyl moieties in 2 are bound by five oxygen atoms from the tellurite chains to create seven-coordinate pentagonal bipyramidal U(VI). The structures of 3 and 4 both contain one-dimensional [UO(2)(TeO(3))(2)](2-) chains constructed from tetragonal bipyramidal U(VI) centers that are bridged by tellurite anions. The chains differ between 3 and 4 in that all of the pyramidal tellurite anions in 3 have the same orientation, whereas the tellurite anions in 4 have opposite orientations on each side of the chain. In 4, there are also additional isolated TeO(3)(2-) anions present. Crystallographic data: 1, orthorhombic, space group Cmcm, a = 7.9993(5) A, b = 8.7416(6) A, c = 11.4413(8) A, Z = 4; 2, orthorhombic, space group Pbam, a = 10.0623(8) A, b = 23.024(2) A, c = 7.9389(6) A, Z = 4; 3, monoclinic, space group P2(1)/n, a = 5.4766(4) A, b = 8.2348(6) A, c = 20.849(3) A, beta = 92.329(1) degrees, Z = 4; 4, monoclinic, space group C2/c, a = 20.546(1) A, b = 5.6571(3) A, c = 13.0979(8) A, beta = 94.416(1) degrees, Z = 4.     

Novel double layer salts of copper(I) bromide with N-substituted ethylenediammonium cations

The structures of three hybrid organic/inorganic halometalate salts are reported, and the layer structures developed are contrasted. Crystal structures of the isostructural N-methylethylenediammonium (MEDA(2+)) and N-ethylethylenediammonium (EEDA(2+)) salts of copper(I) bromide are both triclinic, space group P1, with lattice constants a = 6.284(7), b = 7.842(6), and c = 12.03(1) A, alpha = 84.84(3), beta = 83.08(2), and gamma = 88.00(3) degrees, and V = 586(1) A(3) with Z = 2 for (MEDA)Cu(2)Br(4) while (EEDA)Cu(2)Br(4) has lattice constants a = 6.27(2), b = 7.78(2), and c = 13.12(3) A, alpha = 84.69(4), beta = 78.18(3), and gamma = 88.17(7) degrees, and V = 623(3) A(3) with Z = 2. The dominant inorganic feature in both salts is anionic (CuBr(2))(n)(n-) chains of edge-shared CuBr(4) tetrahedra. The diammonium cations hydrogen bond these chains together into a unique double layer structure. For comparison purposes, the crystal structure of (CHA)PbBr(3) (CHA(+) = cyclohexylammonium) is reported (monoclinic, space group P2(1)/n, a = 8.088(2) A, b = 7.912(2) A, and c = 19.572(4) A, beta = 96.98(4) degrees, and V = 1243.2(4) A(3) with Z = 4). This contains (PbBr(3))(n)(n-) halometalate chains, this time of face-shared PbBr(6) octahedra. However, here the organic cations tie the chains together into the more common single layer structure.     

Oxygen dependence of K(+)-Cl- cotransport in human red cell ghosts and sickle cells

KCC activity in normal human red cells (containing haemoglobin A, HbA, and termed HbA cells) is O2-dependent, being active in oxygenated cells but inactive in deoxygenated ones. The mechanism for O2 dependence is unknown but a role for Hb has been suggested. In this paper, we address two main questions. First, do membrane ghosts prepared from HbA cells retain an O2-sensitive KCC activity? Second, how is the response of KCC to changes in O2 tension altered in sickle cell patients heterozygous for HbS and HbC? We found that substantial Cl(-)-dependent K+ influx, indicative of KCC activity, was present in both pink (5-10% normal Hb complement) and white (no measurable Hb) ghosts when equilibrated with air. KCC responded to deoxygenation in pink ghosts only (86 +/- 10% inhibition, mean+/-S.E.M., n = 3), whilst KCC activity in white ghosts remained high (23 +/- 8% inhibition). Results indicate that pink ghosts retain an O2-dependent KCC activity but that this is lost in white ghosts. Second, HbSC-containing red cells showed sickling (88 +/- 3%) when deoxygenated, together with activation of the deoxygenation-induced cation pathway (Psickle) and the Gardos channel. KCC activity, however, was elevated in oxygenated HbSC cells, but inhibited by deoxygenation. Thus Hb polymerisation and sickling could be dissociated from the abnormal response of KCC to deoxygenation observed in HbS-containing red cells. These preparations provide a useful system with which to study the components involved in O2-sensitive membrane transport and why it is perturbed in certain pathological conditions (such as sickle cell disease and oxidant toxicity).     

Characterization of the elusive disulfide bridge forming human Hb variant: Hb Ta-Li β83 (EF7)Gly → Cys by electrospray mass spectrometry

An electrospray mass spectrometric approach to the identification of a human hemoglobin (Hb) variant involving a Cys residue incorporation is presented. In Hb Ta-Li (beta83Gly --> Cys), Cys83 forms inter-molecular disulfide bridges. Routine analysis of the denatured Hb showed the presence of a minor beta chain variant whose mass apparently was 1 Da less than the expected mass difference of 46 Da for a Gly --> Cys substitution. Reduction of the globin chains with dithiothreitol gave an intense monomer with the expected mass difference for the Gly --> Cys substitution. After reprocessing the original raw data from the denatured Hb and taking into account the possibility of dimer formation, a component was revealed whose mass was consistent with a disulfide linked dimer of Ta-Li beta globins. The mutation was localized to peptide betaT10 by analysis of a tryptic digest. Tandem mass spectrometry and DNA sequencing confirmed the Gly --> Cys substitution occurred at residue 83 of the beta chain. Problems encountered in identifying the components in mixtures of monomers and dimers are discussed.     

A new type of single-helix coordination polymer with mixed ligands [M2(phen)2(e,a-cis-1,4-chdc)2(H2O)2]n (M=Co and Ni; phen=1,10-phenanthroline; chdc=cyclohexanedicarboxylate)

A new family of single-stranded helices coordination polymers with mixed ligands, [M2(phen)2(e,a-cis-1,4-chdc)2(H2O)2]n (1, M=Co; 2, M=Ni; chdc=cyclohexanedicarboxylic acid; phen=1,10-phenanthroline), were prepared under hydrothermal conditions and characterized by elemental analyses, IR spectra, TG analysis, and single-crystal X-ray diffraction analysis. X-ray crystal structural analyses reveal that 1 and 2 are isomorphic and belong to the monoclinic system. C40H36Co2N4O10, P2(1)/c, a=10.0566(5) A, b=8.8843(5) A, c=20.2912(14) A, beta=100.052(3) degrees, Z=2 for 1; and C40H36Ni2N4O10, P2(1)/c, a=9.8921(6) A, b=9.0151(4) A, c=20.1628(17) A, beta=100.31(2) degrees, Z=2 for 2. In the structures of 1 and 2, the 1,4-chdc ligand possesses only one kind of e,a-cis-conformation although there are both cis- and trans-conformations in the raw material. Two oxygen atoms of one carboxyl in 1,4-chdc ligand and another oxygen atom of contraposition carboxyl link adjacent Co or Ni atoms into an infinite 1-D zigzag chain. The most attractive structural feature of 1 and 2 is that they both exhibit an infinite chiral chainlike structure with 2(1) helices along the b axis. In addition, the right-handed and the left-handed chains are alternate. Meanwhile, the adjacent chains of 1 and 2 are linked via hydrogen bonds into 2-D network structures, which further form 3-D frameworks via pi-pi interactions of 1,10-phen.     

A new inorganic-organic hybrid iron(III) arsenate: (C2H10N2)[Fe(HAsO4)2(H2AsO4)](H2O). Hydrothermal synthesis, crystal structure, and spectroscopic and magnetic properties

A new iron(III) arsenate templated by ethylenediamine, (C2H10N2) [Fe(HAsO4)2(H2AsO4)](H2O), has been prepared by hydrothermal synthesis. The unit-cell parameters are a = 8.705(3) A, b = 16.106(4) A, c = 4.763(1) A, beta = 90.63(3) degrees; monoclinic, P2(1) with Z = 2. The compound exhibits a chain structure along the c-axis with the ethylenediammonium cations as counterion. The chains show isolated FeO6 octahedra with two HAsO4 and one H2AsO4 tetrahedra per FeO6 octahedron. The ESR spectrum at 5.0 K is isotropic with a g-value of 2.0, which remains practically unchanged at room temperature. Magnetic measurements indicate the presence of antiferromagnetic interactions. A value of -0.835 K for the J-exchange parameter has been calculated by fitting the magnetic data to a model for antiferromagnetic chains of spin S = 5/2.     

M(bipyridine)V(4)O(10) (M = Cu, Ag): hybrid analogues of low-dimensional reduced vanadates

New hybrid layered vanadates, M(bpy)V4O10 (I, M = Cu+; II, M = Ag+; bpy = 4,4'-bipyridine), were prepared from hydrothermal reactions at 220-230 degrees C, and their structures were characterized by single-crystal X-ray diffraction [I, P21/c (No. 14), Z = 4, a = 3.6154(3) A, b = 21.217(1) A, c = 20.267(1) A, and beta = 90.028(3) degrees ; II, P (No. 2), Z = 2, a = 3.5731(4) A, b = 10.429(1) A, c = 21.196(2) A, alpha = 89.031(5) degrees , beta = 89.322(5) degrees , and gamma = 85.546(5) degrees ]. The structures of I and II are closely related, though not isostructurally, with both containing partially reduced V4O10- layers that are constructed from zigzag chains of edge-sharing VO5 tetragonal pyramids. Neighboring zigzag chains within a layer condense via shared vertices and alternate between versions containing V4.5+ and V5+ ions, such that two out of four symmetry-unique V atoms are reduced by a half-electron on average. The interlayer spaces contain unusual M(bpy)+ chains formed from the coordination of two bridging bpy ligands to Ag+/Cu+ in a nearly linear fashion and each with a third bond to a single apical O atom of the reduced (V4.5+) VO5 tetragonal pyramids. Both I and II are stable until approximately 350-400 degrees C in O2, at which point the ligands are liberated to yield the purely inorganic MxV4O10 (M = Ag, Cu) solids. The electrical conductivities of both compounds show a temperature dependence that is consistent with Mott's variable-range-hopping model for randomly localized electrons. Magnetic susceptibilities of both I and II can be fitted to a Curie-Weiss expression (theta = -25 and -31 K, respectively; C approximately 0.40 emu.mol-1.K for both) at higher temperatures and one unpaired spin per formula. However, at below approximately 12-18 K, both show evidence for an antiferromagnetic transition that can be fitted well to the Heisenberg linear antiferromagnetic chain model. These results are analyzed with respect to related reduced vanadates and help to provide new structure-property insights for strongly correlated electron systems.     

Structural rules for the chiral supramolecular organization of OPE-based discotics: induction of helicity and amplification of chirality

A systematic study on the structural rules that regulate the chiral supramolecular organization of oligo(phenylene ethynylene) (OPE)-based discotics is presented. This study is based on the chirooptical properties of two different series of triangular shape OPEs. The first of them is composed by OPE-based trisamides with a variable number of chiral side chains (compounds 1) that self-assemble following a cooperative mechanism. The CD experiments carried out with these desymmetrized trisamides demonstrate that only one stereogenic center is sufficient to achieve a helical organization with a preferred handedness. However, the ability to amplify the chirality decreases upon decreasing the number of stereocenters at the peripheral side chains. The second series is constituted by triangular shape OPEs with a variable number of ether and amide functional groups and constant absolute configuration of the stereogenic centers at all of the peripheral chains (compounds 2). These compounds do not self-assemble into helical aggregates as demonstrated by the corresponding CD studies. The amplification of chirality observed in the mixtures of some of the components of both series has been investigated. The combination of chiral trisamide 1d with chiral but nonhelical 2b or 2c does not produce an amplification of chirality most probably due to the mismatch between the stereogenic centers of both components. However, the combination of achiral trisamide 1a with chiral but nonhelical bisamide 2c generates, in a cooperative manner, helical structures with a preferred handedness in a process involving the transfer of helicity from 1a to 2c and the transfer of chirality from 2c to 1a. The structural features of the OPE discotics also exert a strong influence on the columnar aggregates. Thus, while achiral 1a bundles into thick filaments to form an organogel, the gelation ability of these triangular OPEs decreases upon increasing the number of stereogenic centers, being totally canceled for compounds 2 in which the amide functionalities are replaced by ether linkages. Finally, we have also registered AFM images of the helical aggregates obtained from the mixture of 1a+2c, which implies an efficient transfer of the chiral objects from solution to surfaces. The study presented herein increases the understanding of the structural rules that regulate the chiral supramolecular organization of discrete molecules in general and, more specifically, those based on π-conjugated oligomers.     

Synthesis and characterization of protonated zirconium trisilicate and its exchange phases with strontium

A partially protonated form of the mineral umbite has been prepared by ion exchange of K2ZrSi3O9 x H2O with acetic acid. The protonated phase, compound 1, is assigned the formula H1.45K0.55ZrSi3O9 x 2 H2O and crystallizes in the space group P2(1)/c with unit cell dimensions of a = 7.1002(2), b = 10.1163(3), c = 13.1742(5), and beta = 91.181(1) degrees. The characteristic building blocks of the acid phase are almost identical to those of the parent compound. The framework is composed of polymeric chains of trisilicate groups linked by zirconium atoms, resulting in zeolite-type channels. When viewed down the a axis, two unique ion-exchange channels can be seen. Site 1 is marked by a 12-membered ring and contains 2 cations. Site 2, a 16-membered ring, contains 4 water molecules. Compound 2, consists of a mixed Sr2+ and K+ phase synthesized from 1 by ion exchange with Sr(NO3)2. Compound 2 has the formula K0.34Sr0.83ZrSi3O9 x 1.8 H2O and crystallizes in the same space group P2(1)/c. It has cell dimensions of a = 7.1386(3), b = 10.2304(4), c = 13.1522(4), and beta = 90.222(1) degrees. The Sr2+ cations are distributed evenly among the two exchange sites, showing no preference for either cavity. Compound 3 is the fully substituted Sr phase, SrZrSi3O9 x 2 H2O, and retains the same space group as that of the previous two compounds having unit cell dimensions of a = 7.1425(5), b = 10.2108(8), c = 13.0693(6), and beta = 90.283(1) degrees. The strontium cations show a slight affinity for ion-exchange site 2, having a higher occupancy of 0.535, while site 1 is occupied by the remainder of the Sr2+ cations with an occupancy of 0.465. Batch uptake studies demonstrate a selectivity series among alkaline earth cations of Ba2+ > Sr2+ > Ca2+ > Mg2+.     

Topological relationships and building blocks in Zintl phases of the composition Ba(n+1)(Mg,Li)2nSi2(n+1)

The structures of two novel Zintl phases, Ba6Mg5.2Li2.8Si12 and BaMg0.1Li0.9Si2, are presented. Both compounds contain chains in cis-trans conformation. The silicon partial structure of Ba6Mg5.2Li2.8Si12 (C2/m; a = 1212.0(1), b = 459.78(4), c = 1129.10(9) pm; beta = 91.77(2) degrees; Z = 1) is built of unbranched, planar Si6 chains while BaMg0.1Li0.9Si2 (Pnma; a = 725.92(5), b = 461.36(3), c = 1169.08(8) pm; Z = 4) consists of infinite Si(n) chains. The compounds show all electronic and structural characteristics that are typical for the special subset of Zintl phases with highly charged planar anions. The structures of the new compounds, as well as that of Ba2Mg3Si4, can be derived from the common parent type BaMg2Si2. It is shown that a comprehensive picture of a chemical twinning based on BaMg2Si2 can be derived.     

Analysis of hemoglobin and globin chain variants by a commonly used capillary isoelectric focusing method

To analyze both hemoglobin (Hb) and globin chain variants, we modified a commonly used method, capillary isoelectric focusing (CIEF), with detection at 280 nm. The samples were hemolysates prepared from red blood cells, and globin chains obtained from the hemolysates by treatment with cold acidified acetone. When the migration time for the internal reference, carbonic anhydrase I (isoelectric point, pI 6.60), was taken as 1.0, the migration ratio for Hb A0 in normal human blood was 0.877 +/- 0.004 (mean +/- SD, n = 9), and those of the alpha- and beta-globin chains were 0.673 +/- 0.004 and 0.847 +/- 0.005 (mean +/- SD, n = 4), respectively. The ratio of peak heights between the beta- and alpha-globin chains (beta/alpha) in the normal Hbs obtained from four subjects was almost constant at 2.5 +/- 0.1 (mean +/- SD). This ratio indicates which of the globin chains includes a mutation (if one exists). When an Hb variant, Hb Hoshida (in which Gln is substituted for Glu at residue 43 in the beta-globin chain), was analyzed by this method, two main peaks were observed (migration ratios 0.836 and 0.877, corresponding to an abnormal and the normal Hb, respectively). An additional peak with an abnormal migration ratio of 0.788 was also detected in the globin chain profiles. The ratio of peak heights between normal beta- and alpha-globin chains was 1.57, indicating that a mutation exists in the beta-globin chain. We thus established a convenient system using CIEF that provides a rapid and reproducible method for the random analysis of both Hb and globin chain variants.     

Point‐of‐Care Amperometric Testing of Diabetic Marker (HbA1c) Using Specific Electroactive Antibodies

Specific immune detection of glycated hemoglobin is still a great challenge owing to the small epitopic difference between Hemoglobin (Hb) and HbA1c. We report a new electrochemical immunoassay format for point of care testing of HbA1c. A conducting self‐assembled monolayer of mercaptophenyl boronic acid (MPBA) was used as a capture layer for binding of glycated proteins and ferrocene tagged anti‐HbA1c antibody (FcAb) as a tracer molecule on a gold screen printed electrode. Validation of the new HbA1c assay was carried out using 6 clinical samples with known HPLC values and a correlation coefficient of 98 % was observed.