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W Brill

Publications and source records attributed to W Brill.

9 recordsLinked to original sources
PubMed1994

A novel fluorogenic substrate for ribonucleases. Synthesis and enzymatic characterization.

The synthesis and enzymatic characterization of DUPAAA, a novel fluorogenic substrate for RNases of the pancreatic type is described. It consists of the dinucleotide uridylyl-3',5'-deoxyadenosine to which a fluorophore, o-aminobenzoic acid, and a quencher, 2,4-dinitroaniline, have been attached by means of phosphodiester linkages. Due to intramolecular quenching the intact substrate displayed very little fluorescence. Cleavage of the phosphodiester bond at the 3'-side of the uridylyl residue by RNase caused a 60-fold increase in fluorescence. This allowed the continuous and highly sensitive monitoring of enzyme activity. The substrate was turned over efficiently by RNases of the pancreatic type, but no cleavage was observed with the microbial RNase T1. Compared to the dinucleotide substrate UpA, the specificity constant with RNase A, RNase PL3 and RNase U(s) increased 6-, 18-, and 29-fold, respectively. These differences in increased catalytic efficiency most likely reflect differences in the importance of subsites on the enzyme in the binding of elongated substrates. Studies on the interactions of RNase inhibitor with RNase A using DUPAAA as a reporter substrate showed that it was well suited for monitoring this very tight protein-protein interaction using pre-steady-state kinetic methods.

Aminobenzoates↗
PubMed1986

NMR studies of DNA recognition sequences and their interaction with proteins. The phage lambda OR1 operator, a symmetric lac operator and their specific complexes with cro protein and lac repressor "headpiece".

The phage lambda operator OR1 and a 18 base pair symmetric lac operator have been studied by high resolution NMR. The imino proton resonances and the resonances of the unexchangeable protons (except the 5' and 5" sugar proton resonances) have been assigned by one- and two-dimensional NOE techniques. The imino proton resonances of OR1 and the symmetric lac operator have been used to monitor changes induced in the operator structure by the formation of a specific complex with the phage lambda cro protein and with the lac repressor N-terminal DNA binding domain ("headpiece"). Two regions within the OR1 sequence could be identified, where changes in the imino proton resonance positions occur: The central part around base pairs CG 9 and 10 and the region around base pairs AT 5 and CG 5. The TA base pair 6 is the only position in the symmetric lac operator, where the complex formation with headpiece induces a change.

Bacteriophage lambda↗
PubMedDate not supplied

[Improving fiber adhesion by surface oxidation in carbon fiber reinforced bone cement].

The mechanical superiority of carbon fiber reinforced PMMA containing additional apatite was shown previously. For further improvement these carbon fibers were now submitted to a superficial oxidation treatment by HNO3. A closer contact between the carbon fibers and PMMA and even trabeculae-like adhesions were detected by Scanning Electron Microscopy. The fatigue strength of the carbon fiber reinforced bone cement could be increased at 17% by this oxidation treatment. This increase, however, is less than that observed in the case of other fiber reinforced composites. Most likely this is caused by the pronounced polymerisation contraction of PMMA. Further improvement of the adhesion of the fibers to cement may be achieved by different oxidation techniques, further extraction of foreign substances or graft polymerization of the carbon fibers by PMMA or other polymers.

Adhesiveness↗
PubMedDate not supplied

[Morphologic analysis of endoprosthesis materials with scanning electron microscopy].

The biomaterials used in endoprosthesis are subject to great dynamic and tribologic stress which they are not always able to withstand. Wear and fatigue fractures may ensue. The SEM is a valuable tool for controlling quality and determining the nature of faults in the material. Examination of the surfaces of a fatigue fracture usually reveals the cause of the fracture. The presence of manufacturing faults shows that the producer's quality control (the non-destructive-method) was not always sufficient. The SEM is also valuable for examining the polished surfaces of the prosthesis before and after load bearing in order to evaluate wear damages.

Biomechanical Phenomena↗
PubMedDate not supplied

[The interface between hydroxyapatite ceramic and newly formed bone in scanning electron microscopy].

Bone samples, which have been embedded in methylmethacrylate in an undecalcified state can be evaluated by a scanning electron microscopy after removal of the methylmethacrylate. Hydroxy apatite (HA) has been implanted in 6 mm bore holes of the rabbits' femoral condyle. The animals were sacrificed after 2, 4, 6, 8 weeks and 8 months. The interface between HA and the newly built bone was observed. A direct contact has been found regularly through high magnification (up to 16,000 times). The three dimensional embedding of the implanted HA-particles into the newly built bone can be shown. Collagen filaments are spreading out from bone to HA-particles. We think that there is not only a mechanical but also a chemical connection between both.

Animals↗