Surface composition of anhydrous tricalcium aluminate and calcium aluminoferrite

Electron spectroscopy and optoacoustic spectroscopy (OAS) have been used to study the surfaces of synthetic tricalcium aluminate, Ca₃Al₂O₆ and calcium aluminoferrite, Ca₂AIFeO₅. The surfaces of these compounds have compositions which differ markedly from those of the bulk. The surface of tricalcium aluminate is depleted in calcium and enriched in aluminium and also carries relatively stable hydroxyl groups, which can be detected by OAS. Calcium aluminoferrite has a surface enriched in aluminium and depleted in calcium and iron. Again, some hydroxyl groups are present on the surface. These differences in surface composition are discussed with particular reference to the early stages of reaction with water.     

Plasmonic sensing characteristics of single nanometric holes

The optical response of isolated holes in 20 nm thin gold is probed as a function of alkanethiol CH(3)(CH2)x SH (x epsilon in 1-15) and protein adsorption using dark-field spectroscopy. We establish that the plasmon excitations of single and short-range ordered 60 nm holes exhibit similar E-field decay lengths delta approximately 10-20 nm and that a single hole can be used to resolve the successive adsorption of a protein (biotin-BSA) and its interaction partner (neutravidin). The data confirm the localized character of the hole plasmon and demonstrate that its applicability for bio/chemosensing is similar to that of particle plasmons.     

Predictive modelling of growth and measurement of enzymatic synthesis and activity by a cocktail of Brochothrix thermosphacta

The possibility was examined of developing a predictive model that combined microbial growth (increase in cellular number) and extracellular enzyme activity of a cocktail of three strains of Brochothrix thermosphacta. Estimations of growth and enzyme activity were made within a three-dimensional matrix of conditions: temperature 2-20 degrees C, pH value 4.0-7.5 and water activity (a(w)) 0.95-0.995. A model which predicted growth based on increases in cell number was constructed. No extracellular lipases were detected, but slight proteolytic reactions were observed. Although it was not possible to model protease activity, the growth model and information relating to enzyme activity will be made freely available in a database on the Internet.     

Synthesis of cytidine ribonucleotides by stepwise assembly of the heterocycle on a sugar phosphate

Although various syntheses of the nucleic acid bases exist and ribose is a product of the formose reaction, no prebiotically plausible methods for attaching pyrimidine bases to ribose to give nucleosides have been described. Kinetic and thermodynamic factors are thought to mitigate against such condensation reactions in aqueous solution. This inability to produce pyrimidine nucleosides and hence nucleotides is a major stumbling block of the "RNA World" hypothesis and has led to suggestions of alternative nucleic acids as evolutionary precursors to RNA. Here, we show that a process in which the base is assembled in stages on a sugar phosphate can produce cytidine nucleotides. The sequential action of cyanamide and cyanoacetylene on arabinose-3-phosphate produces cytidine-2',3'-cyclophosphate and arabinocytidine-3'-phosphate.     

The interaction between the use of information technology and organizational culture

The interaction between the use of information technology, (IT) in organizations and that organization's culture is examined. The interaction is considered from the early stages of specification through to the regular use of the systems. The changes in the technological artefacts which result from the use of IT are discussed. Some suggestions about control of the interaction are made.     

Structural determinants of the interaction between the erbB2 receptor and the Src homology 2 domain of Grb7

The Src homology 2 (SH2) domain-containing protein Grb7 and the erbB2 receptor tyrosine kinase are overexpressed in a subset of human breast cancers. They also co-immunoprecipitate from cell lysates and associate directly in vitro. Whereas the Grb7 SH2 domain binds strongly to erbB2, the SH2 domain of Grb14, a protein closely related to Grb7, does not. We have investigated the preferred binding site of Grb7 within the erbB2 intracellular domain and the SH2 domain residues that determine the high affinity of Grb7 compared with Grb14 for this site. Phosphopeptide competition and site-directed mutagenesis revealed that Tyr-1139 of erbB2 is the major binding site for the Grb7 SH2 domain, indicating an overlap in binding specificity between the Grb7 and Grb2 SH2 domains. Substituting individual amino acids in the Grb14 SH2 domain with the corresponding residues from Grb7 demonstrated that a Gln to Leu change at the betaD6 position imparted high affinity erbB2 interaction, paralleled by a marked increase in affinity for the Tyr-1139 phosphopeptide. The reverse switch at the betaD6 position abrogated Grb7 binding to erbB2. This residue therefore represents an important determinant of SH2 domain specificity within the Grb7 family.     

Lack of relationship between CDK activity and G1 cyclin expression in breast cancer cells

The G1 cyclins, cyclin D1 and E, are rate limiting for progression through G1 phase of the cell cycle in breast epithelial cells and are oncogenic when expressed in the mammary epithelium of transgenic mice. These genes are frequently overexpressed in clinical breast cancer where overexpression appears to be associated with specific disease phenotypes, altered responsiveness to therapeutic intervention and patient survival. In order to investigate the functional correlates of cyclin D1 and cyclin E overexpression we employed a panel of normal, immortalized and neoplastic breast epithelial cell lines to examine the relationships between cyclin gene expression, cyclin-CDK complex formation and CDK activity. In agreement with earlier studies cyclin D1 and E expression varied over an approximately tenfold range among the 18 cell lines studied. There was no apparent relationship, however, between cyclin D1 expression and the in vitro activity of its major kinase partner, Cdk4, although MDA-MB-134 cells displayed the highest level of both cyclin D1 expression and Cdk4 activity. Similarly, there was no significant relationship between cyclin E expression and cyclin E-Cdk2 activity. Fractionation of whole cell lysates by gel filtration chromatography revealed that approximately 90% of the cyclin E protein was present in inactive complexes containing the CDK inhibitors p21 and p27. Much of the small fraction of active cyclin E protein was of very high apparent molecular mass, >400 kDa, suggesting that formation of these complexes is a more important determinant of cyclin E-Cdk2 activity than cyclin E abundance. These data suggest that properties of cyclins D1 and E in addition to their ability to activate Cdk4 and Cdk2 may contribute to the effects of overexpression on the breast cancer phenotype.