PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Cross-matching marsupial proteins with eutherian mammal databases: proteome analysis of cells from UV-induced skin tumours of an opossum (Monodelphis domestica)

The identification and characterisation of Monodelphis proteins has required cross-species analysis. Protein expression was investigated in normal, nonirradiated adult fibroblasts and also in fibroblastic cells from a benign cutaneous tumour after chronic ultraviolet (UVB) exposure and a metastatic cutaneous tumour after intermittent exposure. Proteins were separated and visualised by two-dimensional gel electrophoresis (2-D PAGE) and a peptide mass fingerprint (PMF) was obtained for protein spots using matrix assisted laser desorption/ionisation-time of flight-mass spectrometry (MALDITOF-MS). Cross-species PMF database analysis facilitated the identification of 120 proteins, constituting 46.5% of the proteins analysed. The identification of two proteins was confirmed by internal amino acid sequencing using tandem MS. Differential protein expression was observed between normal fibroblasts and those in tumours chronically or intermittently exposed. A number of tropomyosin and vimentin isoforms were expressed only in cells from the metastatic tumour induced by intermittent exposure to UV radiation. These results highlight the value of cross-species PMF analysis for the rapid characterisation of proteins from a poorly defined species and also show how proteomics can be used to detect changes in protein expression in differentially treated cells.     

Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.     

Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.     

Purification and Characterization of Agarase from Marine Bacteria <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. PS12B and Its Use for Preparing Bioactive Hydrolysate from Agarophyte Red Seaweed <Emphasis Type="Italic">Gracilaria verrucosa</Emphasis>

Acinetobacter strain PS12B was isolated from marine sediment and was found to be a good candidate to degrade agar and produce agarase enzyme. The extracellular agarase enzyme from strain PS12B was purified by ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography. The specific activity of the crude enzyme which was 1.52 U increased to 45.76 U, after two-stage purification, with an enzyme yield of 9.76%. Purified enzyme had a molecular mass of 24 kDa. The optimum pH and temperature for activity of purified agarase were found to be 8.0 and 40 °C, respectively. The K_m and V_max values for agarase were 4.69 mg/ml and 0.5 μmol/min, respectively. Treatment with EDTA reduced the agarase activity by 58% at 5 mM concentration. The enzyme activity was stimulated by the presence of Fe²⁺, Mn²⁺, and Ca2⁺ ions while reducing reagents (β-mercaptoethanol and dithiothreitol, DTT) enhanced its activity by 30–40%. The purified agarase exhibited tolerance to both detergents and organic solvents. Major hydrolysis products of agar were DP4 and also a mixture of longer oligosaccharides DP6 and DP7. The enzyme hydrolysed seaweed (Gracilaria verrucosa) exhibited strong antioxidant activity in vitro. Successful hydrolysis of seaweed indicates the potential use of the enzyme to produce seaweed hydrolysate having health benefits as well as the industrial application like the production of biofuels.     

Subproteomics based upon protein cellular location and relative solubilities in conjunction with composite two-dimensional electrophoresis gels

Progress in the field of proteomics is dependent upon an ability to visualise close to an entire protein complement via a given array technology. These efforts have previously centred upon two-dimensional gel electrophoresis in association with immobilised pH gradients in the first dimension. However, limitations in this technology, including the inability to separate hydrophobic, basic, and low copy number proteins have hindered the analysis of complete proteomes. The challenge is now to overcome these limitations through access to new technology and improvements in existing methodologies. Proteomics can no longer be equated with a single two-dimensional electrophoresis gel. Greater information can be obtained using targeted biological approaches based upon sample prefractionation into specific cellular compartments to determine protein location, while novel immobilised pH gradients spanning single pH units can be used to display poorly abundant proteins due to their increased resolving power and loading capacity. In this study, we show the effectiveness of a combined use of two differential subproteomes (as defined by relative solubilities, cellular location and narrow-range immobilised pH gradients) to increase the resolution of proteins contained on two-dimensional gels. We also present new results confirming that this method is capable of displaying up to a further 45% of a given microbial proteome. Subproteomics, utilising up to 40 two-dimensional gels per sample will become a powerful tool for near-to-total proteome analysis in the postgenome era. Furthermore, this new approach can direct biological focus towards molecules of specific interest within complex cells and thus simplify efforts in discovery-based proteome research.     

Microtubule alterations and mutations induced by desoxyepothilone B: implications for drug-target interactions

Epothilones, like paclitaxel, bind to beta-tubulin and stabilize microtubules. We selected a series of four leukemia sublines that display increasing levels of resistance to the epothilone analog desoxyepothilone B (dEpoB). The dEpoB cells selected in 30-140 nM were approximately 15-fold cross-resistant to paclitaxel, while 300 nM selected cells were 467-fold resistant to this agent. The dEpoB-selected cells are hypersensitive to microtubule destabilizing agents, and express increased levels of class III beta-tubulin and MAP4. A novel class I beta-tubulin mutation, A231T, that affects microtubule stability but does not alter paclitaxel binding, was identified. The 300 nM selected cells acquired a second mutation, Q292E, situated near the M loop of class I beta-tubulin. These cells fail to undergo drug-induced tubulin polymerization due to dramatically reduced drug binding. The dEpoB-resistant leukemia cells provide novel insights into microtubule dynamics and, in particular, drug-target interactions.     

Computer extended series solution for unsteady flow in a contracting or expanding pipe

Unsteady flow in a semi-infinite contracting or expanding pipeis reinvestigated using long series analysis. The proposed seriesmethod is useful in analysing the problem for a moderately largeconstant ( = aa/, where a = a(t), the radius of the pipe isa function of time, a(t) is the velocity of the wall, and iskinematic viscosity). For positive values of (expansion ofthe pipe) accuracy of the series representing shear stress andpressure gradient is increased from = 2.89 to = 6.0 by extractingthe singularity followed by completion of the series. For negativevalues of (contraction of the pipe), we revert the series whichresults into the increase of the region of validity of the transposedseries from = -25.0 to = -2.89. Later we use Padé approximantsfor summing them. Also, the asymptotic solution for large valuesof is obtained and it agrees closely with pure numerical valuesof shear stress at the wall and pressure gradient.