Determination of the turnover number of the restriction endonuclease EcoRI using evanescent wave technology

Binding and catalytic activity of the type II restriction endonuclease EcoRI on immobilized DNA has been observed in real time using three different evanescent wave biosensors and two different immobilization techniques. The method gives direct access to the turnover number (kcat) without the necessity for the determination of any concentration or activity. The combination of different evanescent wave techniques gives access to the catalytic mechanism and allows the determination of the rate limiting step.     

(−)-Daucic acid: Proof of -lyxo configuration, synthesis of its -ribo, -xylo, -arabino and -lyxo analogs, and biosynthetic implications

The dimethyl esters of the 2,6-anhydro-3-deoxy-hept-2-enaric acids with -xylo, -lyxo, -arabino, -lyxo- and -ribo-configuration were synthesized from -galactose and -mannose, respectively, and further characterized by their di-O-acetyl and di-O-benzoyl derivatives. Comparison of their physical data with those of Daucus carota derived products revealed (−)-daucic acid to have -lyxo-configuration 46 rather than the previously assigned -xylo stereochemistry 1. Dimethyl daucate 43 could be converted by acid-induced ring contraction and dehydration into naturally occurring (+)-osbeckic acid 47, thereby proving its (S)-configuration. Configurational identity in the pyranoid rings of (−)-daucic acid and KDO, together with available biosynthetic evidence on chelidonic acid 4, a leaf closing factor, suggests a joint, KDO 8-P-based pathway for their biosynthesis in plants.     

Thermisch stimulierte Lumineszenzerscheinungen. I Einfluß der Vorbehandlung von Kupferstaub und das Phänomen „Kontaktgedächtnis”︁

Thermally Stimulated Luminescence Phenomena. I. Influence of Pretreatment of Copper Dust and the Phenomenon “Contact Memory” The thermally stimulated luminescence of so-called “copper dust” is strongly influenced by its pretreatment. Samples which have been cooled prior to measurement show lower energies and those which have been mechanically treated, irradiated or heated, show higher thermoluminescence energies than samples which have been stored normally. After removal of the samples from the metallic carrier and subsequent heating of the latter, the thermoluminescence energies are proportional to those found for the sample measured immediately before. This phenomenon is considered as “contact memory”. All results are interpreted according to the concept of the hierarchic order.     

Lotketten in Speziellen Hjelmslev-Gruppen

Let be given a geometric structure with a set of lines and a symmetric orthogonality relation. F. Bachmann defined in [3] chains of perpendiculars in such a structure, and studied those chains in Hjelmslev-groups. All AGS-groups (= groups treated in [1]) are Hjelmslev-groups, and the theory of Hjelmslev-groups includes also Hjelmslev's concept of Allgemeine Kongruenzlehre. In Hjelmslev-groups, chains of perpendiculars are closely related to the group generated by the points. We establish some results about chains of perpendiculars in special classes of Hjelmslev-groups.     

Affinity interactions between phenylboronic acid-carrying self-assembled monolayers and flavin adenine dinucleotide or horseradish peroxidase

A method is provided for the recognition of glycated molecules based on their binding affinities to boronate-carrying monolayers. The affinity interaction of flavin adenine dinucleotide (FAD) and horseradish peroxidase (HRP) with phenylboronic acid monolayers on gold was investigated by using voltammetric and microgravimetric methods. Conjugates of 3-aminophenylboronic acid and 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) or 11-mercaptoundecanoic acid were prepared and self-assembled on gold surfaces to generate monolayers. FAD is bound to this modified surface and recognized by a pair of redox peaks with a formal potential of -0.433 V in a 0.1 M phosphate buffer solution, pH 6.5. Upon addition of a sugar to the buffer, the bound FAD could be replaced, indicating that the binding is reversible. Voltammetric, mass measurements, and photometric activity assays show that the HRP can also be bound to the interface. This binding is reversible, and HRP can be replaced by sorbitol or removed in acidic solution. The effects of pH, incubation time, and concentration of H(2)O(2) were studied by comparing the catalytic reduction of H(2)O(2) in the presence of the electron-donor thionine. The catalytic current of the HRP-loaded electrode was proportional to HRP concentrations in the incubation solution in the range between 5 microg mL(-1) and 0.1 mg mL(-1) with a linear slope of 3.34 microA mL mg(-1) and a correlation coefficient of 0.9945.     

The luminescence efficiency of YAG: Ce phosphors

The luminescence intensity of Yttrium aluminium garnet activated by the Ce³⁺ (YAGCe³⁺) under cathode-ray excitation depends on the preparation method and content of some dopants. Samples containing Fe, Pt, Ir or some colour centre, respectively, show relatively low luminescence. The maximum luminescence intensity was obtained with the Czochralski method grown single crystals in 98% Ar+2% H₂ atmosphere which were sensitized by oxygen annealing followed by treatment at 1500 °C in molybdenum container using a wet hydrogen atmosphere.