Constructing two-weight codes with prescribed groups of automorphisms

We construct new linear two-weight codes over the finite field with q elements. To do so we solve the equivalent problem of finding point sets in the projective geometry with certain intersection properties. These point sets are in bijection to solutions of a Diophantine linear system of equations. To reduce the size of the system of equations we restrict the search for solutions to solutions with special symmetries.Two-weight codes can be used to define strongly regular graphs. We give tables of the two-weight codes and the corresponding strongly regular graphs. In some cases we find new distance-optimal two-weight codes and also new strongly regular graphs.     

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.     

Chiral diphosphine ligands based on camphor: synthesis and applications in asymmetric hydrogenations

The synthesis of a novel class of atropisomer chiral diphosphine ligands with a bornene framework is described. The new ligands showed in Rh catalyzed asymmetric hydrogenation of α- and β-enamides very high ee’s (more than 99%).     

Quasirationale singularitäten

It Is shown that Elkik's results on deformations of rational singularities hold without Cohen-Macaulay assumptions: let f:XS be flat with normal fibres X_s and desingularisations _s:Y_sX_s; then the sets are open for all d.     

Heats of crystallization of potassium chloride and magnesium chloride hexahydrate from aqueous solutions at 298.15 K. A critical review

Published data on the heats of crystallization from aqueous solutions of potassium chloride and magnesium chloride hexahydrate are critically reviewed and compared with those evaluated from solubility and activity data. The recommended values of the heats of crystallization are −13.8±0.1 kJ mole⁻¹ for KCl and −15.8^−0.3_+2.8 kJ mole⁻¹ for MgCl₂·6 H₂O. A test of the mutual consistency of data for dissolution heats, temperature dependence of solubility and concentration dependence of activity and/or osmotic coefficient is a side-issue of the review.     

Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide

An enzymatic assay for glucose based on the use of the fluorescent probe for hydrogen peroxide, europium(III) tetracycline (EuTc), is described. The weakly fluorescent EuTc and enzymatically generated H₂O₂ form a strongly fluorescent complex (EuTc–H₂O₂) whose fluorescence decay profile is significantly different. Since the decay time of EuTc–H₂O₂ is in the microseconds time domain, fluorescence can be detected in the time-resolved mode, thus enabling substantial reduction of background fluorescence. The scheme represents the first H₂O₂-based time-resolved fluorescence assay for glucose not requiring the presence of a peroxidase. The time-resolved assay (with a delay time of 60 s and using endpoint detection) enables glucose to be determined at levels as low as 2.2 mol L^–1, with a dynamic range of 2.2–100 mol L^–1. The method also was adapted to a kinetic assay in order to cover higher glucose levels (mmol L^–1 range). The latter was validated by analyzing spiked serum samples and gave a good linear relationship for glucose levels from 2.5 to 55.5 mmol L^–1. Noteworthy features of the assay include easy accessibility of the probe, large Stokes shift, a line-like fluorescence peaking at 616 nm, stability towards oxygen, a working pH of approximately 7, and its suitability for both kinetic and endpoint determination.     

Gold nanoparticle-enhanced surface plasmon resonance measurement with a highly sensitive quantification for human tissue inhibitor of metalloproteinases-2

Two different methods for the quantification of human tissue inhibitor of metalloproteinases-2 (TIMP-2) were developed using surface plasmon resonance (SPR) and gold nanoparticles for signal enhancement. The first method, a competitive assay, used TIMP-2 immobilized to the sensor surface and the inactive form of matrix metalloproteinase-2 (proMMP-2) (EC 3.4.24.24) adsorbed to gold nanoparticles. The sensor signals resulting from the interaction of MMP-2-gold nanoparticles with immobilized TIMP-2 were inversely proportional to the amounts of TIMP-2 of the sample. The measuring range for TIMP-2 was about 15–180 pM. The second method, a one-step sandwich assay, used proMMP-2 immobilized to the sensor surface and an anti-TIMP-2 monoclonal antibody coupled to gold nanoparticles. The lower detection limit of this assay format was 0.5 pM of TIMP-2. The binding signals were highly reproducible up to 100 pM of the inhibitor. The improvements obtained in TIMP-2 quantification over already existing tests could contribute to a better understanding and diagnosis of diseases like cancer.     

Small molecules as inhibitors of cyclin-dependent kinases

Cell division (mitosis) is one of the basic requirements for multicellular oranisms. The capability of a cell to replicate enables a complex assembly to be created. Faulty regulation of the control mechanism in the cell cycle leads to an excessive cell proliferation and is the cause of cancer. The key position of the cyclin-dependent kinases (CDKs) and their direct partners, as well as the fact that the majority of malign illnesses show defects in at least one of these key players of the cell cycle, is of great interest for the development of low-molecular-weight CDK inhibitors. In this Review an overview of the different structural classes of ATP-competitive inhibitors of CDKs are given, whose devlopment was aimed at battling cancer. The Review shows how far the development of selective CDK inhibitors has progressed and to what extent the expectations for such drugs have so far been fulfilled.