Membrane-immobilized haptoglobin as affinity matrix for a hemoglobin-A1c immunosensor

An amperometric immunosensor for hemoglobin-A1c (HbA1c) determination has been developed utilizing membrane-immobilized haptoglobin as affinity matrix fixed in front of a Pt-working electrode. The HbA1c assay was carried out in a two-step procedure including the selective hemoglobin enrichment on the sensor surface and the specific HbA1c detection by a glucose oxidase (GOx) labeled anti-HbA1c antibody. Hydrogen peroxide generated by the enzyme label was oxidized at +600 mV versus Ag/AgCl. A standard curve for HbA1c was obtained with a linear range between 0 and 25% HbA1c of total hemoglobin which correspond to 7.8–39 nM. ELISA studies confirmed the advantage of a sandwich-type format with haptoglobin as capture molecule for selective hemoglobin binding over the direct adsorption method. Results by the sandwich immunoassay showed a linear correlation within the clinically relevant range 5–20% (CV < 3). For sensor application the immobilization procedure of haptoglobin onto CDI-activated cellulose membranes was optimized.     

Synthesis, decomposition, and structural studies in the gas phase and solid state of N,N-dimethylaminoxygermane

N,N-Dimethylaminoxygermane, H3GeONMe2, was prepared by the reaction of H3GeBr with LiONMe2 in dimethyl ether at -96 degrees C. The identity of H3GeONMe2 was proven by gas-phase IR and solution NMR spectroscopy (1H, 13C, 15N, 17O). It is an unstable volatile liquid compound. It decomposes by cleavage of a Ge-O and a Ge-H bond giving HONMe2 and an insoluble germanium hydride polymer (GeH2)n. This decomposition reaction has been modeled at the MP2/6-311G(d,p) level of theory by the homodesmotic reaction H3GeONMe2 + Ge2H6-->Ge3H8 + HONMe2, which is predicted slightly exothermic by 14 kJ mol-1. The molecular structure of H3GeONMe2 was determined by gas-phase electron diffraction supported by an ab initio geometry [MP2/6-311G(d,p)] and a force field [MP2/6-31G(d)]. The structure of the compound in the crystal lattice was determined by low-temperature crystallography using a single crystal of H3GeONMe2 grown in situ [C2H9NOGe, orthorhombic, Pnma, Z = 4, a = 8.1280(12) A, b = 9.7037(15) A, c = 7.0722(12) A]. Important bond lengths and angles (gas phase/solid state, A/deg) are Ge-O 1.785(2)/1.815(1), O-N 1.462(7)/1.460(2), N-C 1.460(4)/1.453(2), Ge-O-N 105.2(5)/104.6(1), O-N-C 105.8(5)/105.8(1), C-N-C 110.8(9)/111.2(2), Ge...N 2.587(6)/2.601(1). In the solid state the compound forms infinite chains by intermolecular Ge...O contacts of 2.808 A. The question of the attraction between Ge and N atoms is discussed with respect to reference Ge/O and N/O compounds, which have wider angles at oxygen than H3GeONMe2. For comparison the structures of the compounds H3CONMe2, H3SiONMe2, and H3SnONMe2 were also calculated to reflect the influence of the group 14 atom on the structure and to discuss the occurrence of weak E...N interactions in the compounds H3EONMe2.     

Luminescent organoboron quinolate polymers

The synthesis of well-defined luminescent organoboron polymers via a novel three-step procedure starting from silylated polystyrene is reported. Highly selective borylation of poly(4-trimethylsilylstyrene) (PS-Si), followed by replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl), and final introduction of the 8-hydroxyquinolato moiety yields a series of new organoboron quinolate polymers in 67-83% isolated yield. The hexyl-substituted polymers are highly soluble and solution-processable yielding thin films that efficiently emit light at 513-514 nm upon excitation at 395 nm.     

Polarographic determination of α-amylase activity

The enzyme α-amylase splits blue starch in fragments bearing electroactive groups which exhibit two waves in the pulse polarograms. This behaviour is the basis of the polagraphic determination of bacterial and human serum α-amylase activity. The differential pulse mode is more sensitive by a factor of 25 as compared with normal pulse polarography. With serum α-amylase, protein adsorption disturbs the determination of low activities.     

Organoaluminium and -gallium compounds with N,N-diisopropylaminomethyl groups

The N,N-diisopropylaminomethyl aluminium compound [tBu2AlCH2NiPr2 x LiCl]2(1) and the gallium compounds Li[tBu2Ga(CH2NiPr2)2](2) and [tBu2GaCH2N(H)iPr2]Cl x tBu3Ga (3) were prepared by transmetallation of N,N-diisopropylaminomethyllithium LiCH2NiPr2 with di-tert-butylaluminium or -gallium chloride, and characterised by elemental analyses, multinuclear NMR spectroscopy (1H, 13C, 27Al, 7Li) and IR spectroscopy. The crystal structures have been determined by single crystal X-ray diffraction. Compound aggregates as a centrosymmetric dimer, with two Al-C-N units connected by a frame of two LiCl molecules [Al-Cl 2.367(1), Cl-Li 2.339(4) and 2.374(4), Li-N 1.977(4)A]. Compound 2 is a lithium organogallate with two weak LiN bonds [1.965(7) and 1.937(7)A]. Compound 3 contains two different moieties: tBu3Ga and a [tBu2GaCH2N(H)iPr2]+ cation, which are bridged by a Cl- anion [Ga-Cl 2.445(1) and 2.579(1), HCl 2.362(3)A].     

Quantum chemical calculations for the determination of the molecular structure of conjugated compounds: Part XIII. On the conformational structure of rans-benzylideneaniline in the gas phase and in solution

Contrary to the results of other semi-empirical all-valence electron methods, the main features concerning the conformation of trans-benzylideneaniline are correctly accounted for using the NDDO method. Based on a modified continuum model the influence of solvents on the molecular structure was estimated.     

Laccase-catalyzed carbon-carbon bond formation: oxidative dimerization of salicylic esters by air in aqueous solution

The laccase catalyzed oxidative dimerization of salicylic esters, a rare example of a laccase-catalyzed carbon-carbon bond formation, was studied. This reaction allows the use of air as stoichiometric oxidant and proceeds in aqueous solution. The preparative scope and the mechanism of the method, which provides a new and convenient access to functionalized biaryls under mild conditions, were investigated.     

Terminally Dimetallated N,N′‐Dimethylpiperazines with Doubly Spirocyclic Structures

Dilithiated N,N′‐dimethyl‐piperazine, LiCH₂N(CH₂CH₂)₂ NCH₂Li ( 2 ) was prepared by transmetallation of N,N′‐bis(trimethylstannylmethyl)‐piperazine ( 1 ) with ⁿBuLi and was isolated as a highly pyrophoric yellowish powder in high yield. Compound 2 was characterized by elemental analysis and was reacted as difunctional aminomethylating reagent with dialkyl‐earth metal chlorides, R₂MCl (M = Al, Ga; R = Me, ^tBu) which resulted in the formation of spirocyclic adducts of N,N′‐bis(dialkylmetallamethyl)‐piperazine and unreacted dialkylmetal chlorides, [(Me₂AlCl)Me₂AlCH₂N(CH₂CH₂)₂NCH₂AlMe₂(ClAlMe₂)] ( 3 ) and [(^tBu₂GaCl)^tBu₂GaCH₂N(CH₂CH₂)₂NCH₂Ga^tBu₂(ClGa^tBu₂)] ( 4 ) with five‐membered rings. Compounds 1 , 3 and 4 were identified by NMR‐spectroscopy (¹H, ¹³C, ¹¹⁹Sn for 1 , ²⁷Al for 3 ), mass spectra (EI, for 1 ) and by crystal structure determinations.