Hanging-drop multicellular spheriods as a model of tumour angiogenesis

The establishment of a vascular network within tumours is a key step in the progression towards an aggressive, metastatic state, with poor prognosis. We have developed a novel in vitro model to specifically capture the interaction between endothelial cells and solid tumours. Micro-vascularised in vitro tumour constructs were produced by introducing endothelial cells to multicellular spheroids formed in hanging drops. Upon introduction, the endothelial cells migrated into the tumour spheroid, establishing tubular networks and luminal structures. This system relies on the natural pro-angiogenic capacity of multicellular spheroids, and does not require the addition of exogenous angiogenic factors, or use of extracellular-matrix substitutes.

Hanging Basket, C House, Coorparoo, Brisbane

Timber alcove located under skylight within outdoor room.

Hanging Basket, C House, Coorparoo, Brisbane

Timber alcove located under skylight within outdoor room.

Hanging Basket, C House, Coorparoo, Brisbane

Timber alcove located under skylight within outdoor room.

Hanging Basket, C House, Coorparoo, Brisbane

Timber alcove located under skylight within outdoor room.

Crystallization and preliminary X-ray diffraction studies of mammalian purple acid phosphatase

The oxidized form of purple acid phosphatase from pig allantoic fluid has been crystallized in the presence of phosphate using the hanging-drop technique. The crystals belong to the space group P2(1)2(1)2(1) and have unit-cell parameters a = 66.8, b = 70.3, c = 78.7 Angstrom. Diffraction data collected from a cryocooled crystal using a conventional X-ray source extend to 1.55 Angstrom resolution. A knowledge of the three-dimensional structure of mammalian purple acid phosphatase will aid in understanding the substrate specificity of the enzyme and will be important in the rational design of inhibitors, with potential in the treatment of bone diseases.

Determination of the stability constants of mercury(II) complexes of mixed donor macrobicyclic encapsulating ligands

The reactions of mercury(II) with the mixed donor encapsulating ligands 3,6,16-trithia-6,11,19-triazabicyclo[6.6.6]icosane (AMN(3)S(3)sar) and 1-amino-8-methyl-6,19-dithia-3,10,13,16-tetraazabicyclo[6.6.6]icosane (AMN(4)S(2)sar) have been studied. NMR ligand-ligand competition experiments with the ligands 1,4,8,11-tetraazaeyclotetradecane ([14]aneN(4)), 1-thia-4,7,10-triazacyclododecane ([12]aneN(3)S) and ethylenediaminetetraacetic acid (EDTA) with AMN(3)S(3)sar and Hg(II) indicated that [14]aneN(4) would be an appropriate competing ligand for the, determination of the Hg(II) stability constant. Calculations indicated the ratio of concentrations of AMN3S3sar, [14]aneN(4) and Hg(II) required for the determination of the stability constant ranged from 1:1:1 to 1:5:1. Refinement of the titration curves yielded log(10)K[Hg(AMN(3)S(3)sar)](2+) = 17.7. A similar competition titration resulted in the determination of the stability constant for the AMN(4)S(2)sar system as log(10)K[Hg(AMN(4)S(2)sar)](2+) = 19.5. The observed binding constants for the mixed N/S donor systems and the hexaaza analogues sar (3,6,10,13,16,19-hexaazabicyclo [6.6.6]icosane) and diamsar (1,8-diamino-3,6,10,13,16,19 -hexazabicyclo [6.6.6] icosane (log(10)K-[Hg(diamsar)](2+) = 26.4; log(10)K[Hg(sar)](2+) = 28.1) differ by approximately ten orders of magnitude. The difference is ascribed not to a cryptate effect but to a mismatch in the Hg-N and Hg-S bond lengths in the N/S systems.

Expression, purification, crystallization, and NMR studies of the helicase interaction domain of Escherichia coli DnaG primase

in Escherichia coli, the DnaG primase is the RNA polymerase that synthesizes RNA primers at replication forks. It is composed of three domains, a small N-terminal zinc-binding domain, a larger central domain responsible for RNA synthesis, and a C-terminal domain comprising residues 434-581 [DnaG(434-581)] that interact with the hexameric DnaB helicase. Presumably because of this interaction, it had not been possible previously to express the C-terminal domain in a stably transformed E coli strain. This problem was overcome by expression of DnaG(434-581) under control of tandem bacteriophage gimel-promoters, and the protein was purified in yields of 4-6 mg/L of culture and studied by NMR. A TOCSY spectrum of a 2 mM solution of the protein at pH 7.0, indicated that its structured core comprises residues 444-579. This was consistent with sequence conservation among most-closely related primases. Linewidths in a NOESY spectrum of a 0.5 mM sample in 10 mM phosphate, pH 6.05, 0.1 M NaCl, recorded at 36 degreesC, indicated the protein to be monomeric. Crystals of selenomethionine-substituted DnaG(434-581) obtained by the hanging-drop vapor-diffusion method were body-centered tetragonal, space group I4(1)22, with unit cell parameters a = b 142.2 Angstrom, c = 192.1 Angstrom, and diffracted beyond 2.7 Angstrom resolution with synchrotron radiation. (C) 2003 Elsevier Inc. All rights reserved.

Separation of mercury (II), lead (II), and silver (I) from aqueous solution using an aminopolycarboxylate silica

A quartz crystal microbalance modified by the attachment of silica particles derivatized with the aminopolycarboxylate ligand N-[(3-trimethoxysilyl)propyl]ethylenediamine-N,N',N'-triacetic acid has been employed to assess conditions under which mercury (II), lead (II), and silver (I) nitrates may be separated in aqueous solution. The separation protocol, which involved removal of Hg(II), as [HgI4](2-), and Pb(II) with H+ was successfully applied to a batchwise separation of the 3 metal ions.

Bis(diethylenetriamine)mercury(II) bis(thiocyanate)

Mercury(II) in the title compound, [Hg(C4H13N3)2](SCN)2, is six-coordinated with two diethylenetriamine (dien) ligands in a sym-facial configuration. The complex cation has a twofold axis of symmetry, and the secondary amine groups are in trans positions.

Drop penetration into porous powder beds

The kinetics of drop penetration were studied by filming single drops of several different fluids (water, PEG200, PEG600, and HPC solutions) as they penetrated into loosely packed beds of glass ballotini, lactose, zinc oxide, and titanium dioxide powders. Measured times ranged from 0.45 to 126 s and depended on the powder particle size,viscosity, surface tensions, and contact angle. The experimental drop penetration times were compared to existing theoretical predictions by M. Denesuk et al. (J. Colloid Interface Sci. 158, 114, 1993) and S. Middleman (Modeling Axisymmetric Flows: Dynamics of Films, Jets, and Drops, Academic Press, San Diego, 1995) but did not agree. Loosely packed powder beds tend to have a heterogeneous bed structure containing large macrovoids which do not participate in liquid flow but are included implicitly in the existing approach to estimating powder pore size. A new two-phase model was proposed where the total volume of the macrovoids was assumed to be the difference between the bed porosity and the tap porosity. A new parameter, the effective porosity (epsilon)eff, was defined as the tap porosity multiplied by the fraction of pores that terminate at a macrovoid and are effectively blocked pores. The improved drop penetration model was much more successful at estimating the drop penetration time on all powders and the predicted times were generally within an order of magnitude of the experimental results. (C) 2002 Elsevier Science (USA).