1H, 13C, 15N nuclear magnetic resonance backbone assignments and secondary structure of human calcineurin B

The calmodulin- and calcium-stimulated protein phosphatase calcineurin, PP2B, consists of two subunits: calcineurin B, which binds Ca2+, and calcineurin A, which contains the catalytic site and a calmodulin binding site. Heteronuclear 3D and 4D NMR experiments were carried out on a recombinant human calcineurin B which is a 170-residue protein of molecular mass 19.3 kDa, uniformly labeled with 15N and 13C. The nondenaturing detergent CHAPS was used to obtain a monomeric form of calcineurin B. Three-dimensional triple resonance experiments yielded complete sequential assignment of the backbone nuclei (1H, 13C, and 15N). This assignment was verified by a 4D HN(COCA)NH experiment carried out with 50% randomly deuteriated and uniformly 15N- and 13C-enriched calcineurin B. The secondary structure of calcineurin B has been determined on the basis of the 13C alpha and 13C beta secondary chemical shifts, J(HNH alpha) couplings, and NOE connectivities obtained from 3D 15N-separated and 4D 13C/15N-separated NOESY spectra. Calcineurin B has eight helices distributed in four EF-hand, helix-loop-helix [Kretsinger, R. H. (1980) CRC Crit. Rev. Biochem. 8, 119-174] calcium binding domains. The secondary structure of calcineurin B is highly homologous to that of calmodulin. In comparison to calmodulin, helices B and C are shorter while helix G is considerably longer. As was observed for calmodulin in solution, calcineurin B does not have a single long central helix; rather, helices D and E are separated by a six-residue sequence in a flexible nonhelical conformation.     

Hydraulic fracturing stress measurements in Hong Kong

Since 1990, a total of 149 hydrofrac stress measurements to about 200 m depth were conducted in 18 boreholes as part of several geotechnical site investigation programs in the Hong Kong area. The in situ tests were carried out by using the wireline hydrofrac technique to move the straddle packer tool within the 76 mm or 101 mm diameter boreholes. Although the tests were performed both in fractured and unfractured crystalline rocks and the boreholes are located in areas of pronounced topographic relief, the results yield a consistent orientation of the maximum horizontal stress of N 108°±28°. Above 150 m depth, the vertical stress S_v due to the weight of the overburden with given rock density is the minimum principal stress, while the few deeper data available suggest that the minimum horizontal principal stress is the least principal stress. The derived stress magnitudes can be reasonably summarized by the following normalized stress-ratios:

where z is the depth in meters and S_h and S_H are the minimum and maximum horizontal principal stresses. Due to the considerable scatter of the stress data at shallow depth above 100 m, it is suggested that further detailed in situ stress measurements be undertaken in areas where large-scale underground excavations are planned.     

Improvement of haemocompatibility of metallic stents by polymer coating

An alternative to open heart surgery in treating arterial diseases causing restricted blood flow is the implantation of intracoronary metallic stents. In spite of the advances in implantation and in spite of the excellent mechanical properties of metallic stents, there are still limitations because of the thrombogenicity of the metal. We have, hence, directed our attention to the coating of metallic stents with an ultrathin polymer layer by chemical vapor deposition (CVD) polymerization of 2-chloroparacyclophan. In a second step of surface modification the poly(2-chloroparaxylylene) layer is modified by treatment with a sulfur dioxide plasma in order to obtain a more hydrophilic surface with new functional groups. The results demonstrate the stable polymer coating of the stents and the improvement of haemocompatibility after treatment with sulfur dioxide plasma. Platelet adhesion is decreased from 85% for the metal surface to 20% for the CVD-coated and sulfur-dioxide-plasma treated surface. © 1999 Kluwer Academic Publishers     

Biochemical testing of thyroid function

Various published guidelines recommending serum thyrotropin (TSH)-first thyroid testing are outlined. The entities called "subclinical hypothyroidism" and "subclinical hyperthyroidism" are defined on the basis of abnormal TSH concentrations and normal values of other biochemical thyroid tests. The controversies about follow-up and treatment of these disorders are discussed. The laboratory experience of Mayo Clinic Rochester in using TSH-first thyroid testing and the subsequent implementation of a thyroid test ordering cascade are presented. Finally, recommendations are given for further optimizing laboratory testing for thyroid disorders.     

Betriebsfestigkeitsnachweis für das Teleskop‐Lager beim Projekt SOFIA

Fatigue assessment of the telescope support for the project SOFIA SOFIA is, in simplified terms, a Boeing 747 SP aircraft with a telescope on board. This paper discusses a proposal for the fatigue assessment of the telescope support. Basis of the proposal is the fatigue assessment procedure defined in Eurocode 3. Because the support is part of the aircraft pressure bulkhead it is safety relevant. Therefore the safety margin of the procedure had to be adjusted to the relevant aircraft standards. The telescope support can be considered as a rigid body which is loaded by a known acceleration spectrum. Therefore the fatigue assessment procedure for each specific point of the welded structure is reduced to a simple equation into which only the dead weight stress and the numerical value of the detail category for this point, taken from the classification tables of Eurocode 3, have to be inserted.     

Degradation behavior of hydrogels from poly(vinyl alcohol)‐graft‐[poly(rac‐lactide)/poly(rac‐lactide‐co‐glycolide)]: Influence of the structure and composition on the material's stability

The swellability and mass loss of poly(vinyl alcohol)‐graft‐[poly(rac‐lactide)/poly(rac‐lactide‐co‐glycolide)] hydrogels upon hydrolysis are strongly affected by the composition of the hydrogels. Hydrophobic hydrogels remain at a relatively constant mass for a couple of weeks, and the mass decreases dramatically thereafter, whereas more hydrophilic hydrogels lose mass right from the beginning. All hydrogels display water uptake values between 90 and 280% within 8 weeks. For longer periods of degradation, the water uptake increases up to a maximum of about 900%. Studies of the thermal properties of samples upon degradation and their IR measurements have shown that the degradation rate is related to the physical and chemical structure of the hydrogels and hence to the hydrophobic/hydrophilic balance; that is, the degradation increases with the increasing hydrophilicity of the material. As a result, degradation can be engineered through the variation of the composition and structure of the material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009