Synthesis and biological properties of 2-phenylbenzothiazole derivatives

2-Phenylbenzothiazoles have structural similarities to the antioestrogenic 2-phenylindole, zindoxifene and to the oestrogenic isoflavone, genistein which also inhibits tyrosine kinases. Hydroxylated 2-phenylbenzothiazole derivatives were therefore produced and tested for oestrogenic and tyrosine kinase inhibitory activity. Synthesis of methoxy substituted 2-phenylbenzothiazoles was via the Jacobson method, demethylation being effected by boron tribromide at -70oC. Three amino substituted 2-phenylbenzothiazoles were also synthesised and tested for activity. Data is presented for oestrogen receptor binding activity, aromatase inhibitory activity, epidermal growth factor receptor tyrosine kinase (EGFRTK) inhibitory activity and cytotoxicity to ANN-1, 3T3, MCF-7 and WIDR cells. Oestrogen receptor binding affinity (RBA) was shown by five of the nine compounds tested. 2-(4-hydroxy)-6-hydroxybenzo-thiazole was the most active of the benzothiazoles tested (RBA 0.7). This is low but comparable to that of genistein. EGFRTK inhibitory activity was shown by four of the six benzothiazole derivatives tested; activity was comparable to that of genistein. Cytotoxicity assays have shown no selective toxicity of 2-phenylbenzothiazoles to any of the cell lines tested. Toxicity to MCF-7 cells was similar to that for other cell lines despite some compounds showing oestrogen receptor binding capacity. Amino-substituted 2-phenylbenzothiazoles showed selective toxicity towards transformed ANN-1 cells compared to normal 3T3 cells but the mechanism of this selectivity has not been established. Molecular modelling techniques, including CHEM-X, QUANTA and MOPAC were used to compare known ATP-competitive tyrosine kinase inhibitors with a model of ATP built from the crystal structure of the ATP-phosphoglycerate kinase complex. Structural features thought to be important to kinase inhibition were found and used to suggest further 2-phenylbenzothiazole analogues which may have improved activity.

Biological barriers to the nasal delivery of peptide drugs

The nasal absorption of larger peptide and protein drugs is generally low. The importance of the mucus layer and enzymic degradation in reducing absorption were investigated. Reversed-phase high-performance liquid chromatographic (HPLC) methods were developed to assay a variety of compounds. Pig gastric mucus (PGM) was selected to investigate the importance of the mucus layer. A method of treating and storing PGM was developed and evaluated which was representative of the gel in vivo. The nature of the mucus barrier was evaluated in vitro with three-compartment diffusion cells and a series of compounds with differing physicochemical properties. Mucus retarded the diffusion of all the compounds with molecular weight and charge exerting a marked effect. Binding to mucus was investigated by a centrifugation method. All of the compounds tested were found to bind to mucus with the exception of the negatively charged molecule benzoic acid. The small peptides did not demonstrate greater binding to mucus than any of the other compounds evaluated. The effect of some absorption enhancers upon the rate of diffusion of tryptophan through mucus was determined in vi tro. At the concentrations employed the enhancers EDTA, N-acetylcysteine and taurodeoxycholic acid exerted no effect, whilst taurocholic acid and cholic acid, were found to slightly reduce the rate of diffusion. The intracellular and luminal proteolytic activity of the nose was investigated in the sheep animal model with a nasal mucosal homogenate and a nasal wash preparation respectively and a series of chemically similar peptides. Hydrolysis was also investigated with the proteolytic enzymes carboxypeptidase A, cytosolic leucine aminopeptidase and microsomal leucine aminopeptidase. Sheep nasal mucosa possesses significant peptide hydrolase activity capable of degrading all the substrates tested. Considerable variation in susceptibility was observed. Degradation occurred excl us i ve ly at the pept ide bond between the aromatic amino ac id and glycine, indicating some specificity for aromatic amino acids. Hydrolysis profiles indicated the presence of both aminopeptidase and carboxypeptidase enzymes. The specific activity of the microsomal fraction was found to be greater than the cytosolic fraction. Hydrolysis in the nasal wash indicated the presence of either luminal or loosely-bound proteases, which can degrade peptide substrates. The same specificity for aromatic amino acids was observed and aminopeptidase activity demonstrated. The specific activity of the nasal wash was smaller than that of the homogenate.

The application of methods of uncertain reasoning to the biological classification of river water quality

This thesis presents an investigation into the application of methods of uncertain reasoning to the biological classification of river water quality. Existing biological methods for reporting river water quality are critically evaluated, and the adoption of a discrete biological classification scheme advocated. Reasoning methods for managing uncertainty are explained, in which the Bayesian and Dempster-Shafer calculi are cited as primary numerical schemes. Elicitation of qualitative knowledge on benthic invertebrates is described. The specificity of benthic response to changes in water quality leads to the adoption of a sensor model of data interpretation, in which a reference set of taxa provide probabilistic support for the biological classes. The significance of sensor states, including that of absence, is shown. Novel techniques of directly eliciting the required uncertainty measures are presented. Bayesian and Dempster-Shafer calculi were used to combine the evidence provided by the sensors. The performance of these automatic classifiers was compared with the expert's own discrete classification of sampled sites. Variations of sensor data weighting, combination order and belief representation were examined for their effect on classification performance. The behaviour of the calculi under evidential conflict and alternative combination rules was investigated. Small variations in evidential weight and the inclusion of evidence from sensors absent from a sample improved classification performance of Bayesian belief and support for singleton hypotheses. For simple support, inclusion of absent evidence decreased classification rate. The performance of Dempster-Shafer classification using consonant belief functions was comparable to Bayesian and singleton belief. Recommendations are made for further work in biological classification using uncertain reasoning methods, including the combination of multiple-expert opinion, the use of Bayesian networks, and the integration of classification software within a decision support system for water quality assessment.

Biological interactions with synthetic polymers

Anchorage dependent cell culture is a useful model for investigating the interface that becomes established when a synthetic polymer is placed in contact with a biological system. The primary aim of this interdisciplinary study was to systematically investigate a number of properties that were already considered to have an influence on cell behaviour and thereby establish the extent of their importance. It is envisaged that investigations such as these will not only further the understanding of the mechanisms that affect cell adhesion but may ultimately lead to the development of improved biomaterials. In this study, surface analysis of materials was carried out in parallel with culture studies using fibroblast cells. Polarity, in it's ability to undergo hydrogen bonding (eg with water and proteins), had an important affect on cell behaviour, although structural arrangement and crystallinity were not found to exert any marked influence. In addition, the extent of oxidation that had occurred during the process of manufacture of substrates was also important. The treatment of polystyrene with a selected series of acids and gas plasmas confirmed the importance of polarity, structural groups and surface charge and it was shown that this polymer was not unique among `hydrophobic' materials in it's inability to support cell adhesion. The individual water structuring groups within hydrogel polymers were also observed to have controlling effects on cell behaviour. An overall view of the biological response to both hydrogel and non-hydrogel materials highlighted the importance of surface oxidation, polarity, water structuring groups and surface charge. Initial steps were also taken to analyse foetal calf serum, which is widely used to supplement cell culture media. Using an array of analytical techniques, further experiments were carried out to observe any possible differences in the amounts of lipids and calcium that become deposited to tissue culture and bacteriological grade plastic under cell culture conditions.

A dynamic model of the hypoxia-inducible factor 1α (HIF-1α) network

Activation of the hypoxia-inducible factor (HIF) pathway is a critical step in the transcriptional response to hypoxia. Although many of the key proteins involved have been characterised, the dynamics of their interactions in generating this response remain unclear. In the present study, we have generated a comprehensive mathematical model of the HIF-1a pathway based on core validated components and dynamic experimental data, and confirm the previously described connections within the predicted network topology. Our model confirms previous work demonstrating that the steps leading to optimal HIF-1a transcriptional activity require sequential inhibition of both prolyl- and asparaginyl-hydroxylases. We predict from our model (and confirm experimentally) that there is residual activity of the asparaginyl-hydroxylase FIH (factor inhibiting HIF) at low oxygen tension. Furthermore, silencing FIH under conditions where prolyl-hydroxylases are inhibited results in increased HIF-1a transcriptional activity, but paradoxically decreases HIF-1a stability. Using a core module of the HIF network and mathematical proof supported by experimental data, we propose that asparaginyl hydroxylation confers a degree of resistance upon HIF-1a to proteosomal degradation. Thus, through in vitro experimental data and in silico predictions, we provide a comprehensive model of the dynamic regulation of HIF-1a transcriptional activity by hydroxylases and use its predictive and adaptive properties to explain counter-intuitive biological observations.

Characterisation of electrospun polystyrene scaffolds for three-dimensional in vitro biological studies

The purpose of this study was to produce a well-characterised electrospun polystyrene scaffold which could be used routinely for three-dimensional (3D) cell culture experimentation. A linear relationship (p<0.01p<0.01) between three principal process variables (applied voltage, working distance and polymer concentration) and fibre diameter was reliably established enabling a mathematical model to be developed to standardise the electrospinning process. Surface chemistry and bulk architecture were manipulated to increase wetting and handling characteristics, respectively. X-ray photoelectron spectroscopy (XPS) confirmed the presence of oxygen-containing groups after argon plasma treatment, resulting in a similar surface chemistry to treated tissue culture plastic. The bulk architecture of the scaffolds was characterised by scanning electron microscopy (SEM) to assess the alignment of both random and aligned electrospun fibres, which were calculated to be 0.15 and 0.66, respectively. This compared to 0.51 for collagen fibres associated with native tissue. Tensile strength and strain of approximately of 0.15 MPa and 2.5%, respectively, allowed the scaffolds to be routinely handled for tissue culture purposes. The efficiency of attachment of smooth muscle cells to electrospun scaffolds was assessed using a modified 3-[4,5-dimethyl(thiazol-2yl)-3,5-diphery] tetrazolium bromide assay and cell morphology was assessed by phalloidin-FITC staining of F-actin. Argon plasma treatment of electrospun polystyrene scaffold resulted in significantly increased cell attachment (p<0.05p<0.05). The alignment factors of the actin filaments were 0.19 and 0.74 for the random and aligned scaffold respectively, compared to 0.51 for the native tissue. The data suggests that electrospinning of polystyrene generates 3D scaffolds which complement polystyrene used in 2D cell culture systems.

Identification and relative quantification of tyrosine nitration in a model peptide using two-dimensional infrared spectroscopy

Nitration of tyrosine in proteins and peptides is a post-translational modification that occurs under conditions of oxidative stress. It is implicated in a variety of medical conditions, including neurodegenerative and cardiovascular diseases. However, monitoring tyrosine nitration and understanding its role in modifying biological function remains a major challenge. In this work, we investigate the use of electron-vibration-vibration (EVV) two-dimensional infrared (2DIR) spectroscopy for the study of tyrosine nitration in model peptides. We demonstrate the ability of EVV 2DIR spectroscopy to differentiate between the neutral and deprotonated states of 3-nitrotyrosine, and we characterize their spectral signatures using information obtained from quantum chemistry calculations and simulated EVV 2DIR spectra. To test the sensitivity of the technique, we use mixed-peptide samples containing various levels of tyrosine nitration, and we use mass spectrometry to independently verify the level of nitration. We conclude that EVV 2DIR spectroscopy is able to provide detailed spectroscopic information on peptide side-chain modifications and to detect nitration levels down to 1%. We further propose that lower nitration levels could be detected by introducing a resonant Raman probe step to increase the detection sensitivity of EVV 2DIR spectroscopy. (Graph Presented).

Numerical simulation of mass transfer during the osmotic dehydration of biological tissues

In this paper a mathematical model based on mass transfer in plant tissues is developed. The model takes into account the diffusion and convection of each constituent within the tissue. The driving force for the convection is assumed to be the gradient of hydrostatic pressure. The mass balance equation for the transport of each constituent is established separately for intracellular and extracellular volumes but taking into account the mass exchange across the cell membrane between the intracellular and extracellular volumes. The mass transfer results in not only the change of intracellular and extracellular volumes but also the shrinkage of whole tissue. The model allows us to quantitatively simulate the time evolution of intracellular and extracellular volumes, which was observed in histological sections under the microscope. © 2005 Elsevier B.V. All rights reserved.

Model Construction and Research using System Compositional Approach on Natural Hierarchical Neural Networks. Development of Computer Toolbox

System compositional approach to model construction and research of informational processes, which take place in biological hierarchical neural networks, is being discussed. A computer toolbox has been successfully developed for solution of tasks from this scientific sphere. A series of computational experiments investigating the work of this toolbox on olfactory bulb model has been carried out. The well-known psychophysical phenomena have been reproduced in experiments.

Theoretical Hyperbolic Model of a Partial Agonism: Explicit Formulas for Affinity, Efficacy and Amplification

The quantitative analysis of receptor-mediated effect is based on experimental concentration-response data in which the independent variable, the concentration of a receptor ligand, is linked with a dependent variable, the biological response. The steps between the drug–receptor interaction and the subsequent biological effect are to some extent unknown. The shape of the fitting curve of the experimental data may give some in-sights into the nature of the concentration–receptor–response (C-R-R) mechanism. It can be evaluated by non-linear regression analysis of the experimental data points of the independent and dependent variables, which could be considered as a history of the interaction between the drug and receptors. However, this information is not enough to evaluate such important parameters of the mechanism as the dissociation constant (affinity) and efficacy. There are two ways to provide more detailed information about the C-R-R mechanism: (i) an experimental way for obtaining data with new or

Immunological synapse: a mathematical model of the bond formation process:mathematical modelling of the immature synapse

The cell:cell bond between an immune cell and an antigen presenting cell is a necessary event in the activation of the adaptive immune response. At the juncture between the cells, cell surface molecules on the opposing cells form non-covalent bonds and a distinct patterning is observed that is termed the immunological synapse. An important binding molecule in the synapse is the T-cell receptor (TCR), that is responsible for antigen recognition through its binding with a major-histocompatibility complex with bound peptide (pMHC). This bond leads to intracellular signalling events that culminate in the activation of the T-cell, and ultimately leads to the expression of the immune eector function. The temporal analysis of the TCR bonds during the formation of the immunological synapse presents a problem to biologists, due to the spatio-temporal scales (nanometers and picoseconds) that compare with experimental uncertainty limits. In this study, a linear stochastic model, derived from a nonlinear model of the synapse, is used to analyse the temporal dynamics of the bond attachments for the TCR. Mathematical analysis and numerical methods are employed to analyse the qualitative dynamics of the nonequilibrium membrane dynamics, with the specic aim of calculating the average persistence time for the TCR:pMHC bond. A single-threshold method, that has been previously used to successfully calculate the TCR:pMHC contact path sizes in the synapse, is applied to produce results for the average contact times of the TCR:pMHC bonds. This method is extended through the development of a two-threshold method, that produces results suggesting the average time persistence for the TCR:pMHC bond is in the order of 2-4 seconds, values that agree with experimental evidence for TCR signalling. The study reveals two distinct scaling regimes in the time persistent survival probability density prole of these bonds, one dominated by thermal uctuations and the other associated with the TCR signalling. Analysis of the thermal fluctuation regime reveals a minimal contribution to the average time persistence calculation, that has an important biological implication when comparing the probabilistic models to experimental evidence. In cases where only a few statistics can be gathered from experimental conditions, the results are unlikely to match the probabilistic predictions. The results also identify a rescaling relationship between the thermal noise and the bond length, suggesting a recalibration of the experimental conditions, to adhere to this scaling relationship, will enable biologists to identify the start of the signalling regime for previously unobserved receptor:ligand bonds. Also, the regime associated with TCR signalling exhibits a universal decay rate for the persistence probability, that is independent of the bond length.

Wound healing studies and interfacial phenomena:use and relevance of the corneal model

The interaction of the wound dressing as a biomaterial with the wound bed is the central issue of this chapter. The interfacial phenomenon that encompasses the biological and biochemical consequences that arise when a biomaterial is introduced to a host biological environment is discussed. A great deal can be learned from observations arising from the behaviour of biomaterials at other body sites; one particularly relevant body site in the context of wound healing is the anterior eye. The cornea, tear film and posterior surface of the contact lens provide an informative model of the parallel interface that exists between the chronic wound bed, wound fluid and the dressing biomaterial. © 2011 Woodhead Publishing Limited All rights reserved.