Functionalisation of polymers: reactive processing, structure and performance characteristics

The main aim of this work was to study the effect of two comonomers, trimethylolpropane trimethacrylate (TRIS) and divinylbenzene (DVB) on the nature and efficiency of grafting of two different monomers, glycidyl methacrylate (GMA) and maleic anhydride (MA) on polypropylene (P) and on natural rubber (NR) using reactive processing methods. Four different peroxides, benzoyl peroxide (BPO), dicumyl peroxide (DCP), 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane (t-101), and 1,1-di(tert-butylperoxy)-3,3,5-trimethyl cyclohexene (T-29B90) were examined as free radical initiators. An appropriate methodology was established and chemical composition and reactive processing parameters were examined and optimised. It was found that in the absence of the coagents DVB and TRIS, the grafting degree of GMA and MA increased with increasing peroxide concentration, but the level of grafting was low and the homopolymerisaton of GMA and the crosslinking of NR or chain scission of PP were identified as the main side reactions that competed with the desired grafting reaction in the polymers. At high concentrations of the peroxide T-101 (>0.02 mr) cross linking of NR and chain scission of PP became dominant and unacceptable. An attempt to add a reactive coagent, e.g. TRIS during grafting of GMA on natural rubber resulted in excessive crosslinking because of the very high reactivity of this comonomer with the C=C of the rubber. Therefore, the use of any multifunctional and highly reactive coagent such as TRIS, could not be applied in the grafting of GAM onto natural rubber. In the case of PP, however, the use of TRIS and DVB was shown to greatly enhance the grafting degree and reduce the chain scission with very little extent of monomer homopolymerisation taking place. The results showed that the grafting degree was increased with increasing GMA and MA concentrations. It was also found that T-101 was a suitable peroxide to initiate the grafting reaction of these monomers on NR and PP and the optimum temperature for this peroxide was =160°C. A very preliminary work was also conducted on the use of the functionalised-PP (f-PP) in the absence and presence of the two comonomers (f-PP-DVB or f-PP-TRIS) for the purpose of compatibilising PP-PBT blends through reactive blending. Examination of the morphology of the blends suggested that an effective compatibilisation has been achieved when using f-PP-DVB and f-PP-TRIS, however more work is required in this area.

Interaction of peptides, peptidomimetics and other drug candidates with the DI/tripeptide transport system in intestinal epithelial cells, using the in vitro caco-2 cell culture system

An uptake system was developed using Caco-2 cell monolayers and the dipeptide, glycyl-[3H]L-proline, as a probe compound. Glycyl-[3H]L-proline uptake was via the di-/tripeptide transport system (DTS) and, exhibited concentration-, pH- and temperature-dependency. Dipeptides inhibited uptake of the probe, and the design of the system allowed competitors to be ranked against one another with respect to affinity for the transporter. The structural features required to ensure or increase interaction with the DTS were defined by studying the effect of a series of glycyl-L-proline and angiotensin-converting enzyme (ACE)-inhibitor (SQ-29852) analogues on the uptake of the probe. The SQ-29852 structure was divided into six domains (A-F) and competitors were grouped into series depending on structural variations within specific regions. Domain A was found to prefer a hydrophobic function, such as a phenyl group, and was intolerant to positive charges and H+ -acceptors and donors. SQ-29852 analogues were more tolerant of substitutions in the C domain, compared to glycyl-L-proline analogues, suggesting that interactions along the length of the SQ-29852 molecule may override the effects of substitutions in the C domain. SQ-29852 analogues showed a preference for a positive function, such as an amine group in this region, but dipeptide structures favoured an uncharged substitution. Lipophilic substituents in domain D increased affinity of SQ-29852 analogues with the DTS. A similar effect was observed for ACE-NEP inhibitor analogues. Domain E, corresponding to the carboxyl group was found to be tolerant of esterification for SQ-29852 analogues but not for dipeptides. Structural features which may increase interaction for one series of compounds, may not have the same effect for another series, indicating that the presence of multiple recognition sites on a molecule may override the deleterious effect of anyone change. Modifying current, poorly absorbed peptidomimetic structures to fit the proposed hypothetical model may improve oral bioavailability by increasing affinity for the DTS. The stereochemical preference of the transporter was explored using four series of compounds (SQ-29852, lysylproline, alanylproline and alanylalanine enantiomers). The L, L stereochemistry was the preferred conformation for all four series, agreeing with previous studies. However, D, D enantiomers were shown in some cases to be substrates for the DTS, although exhibiting a lower affinity than their L, L counterparts. All the ACE-inhibitors and β-lactam antibiotics investigated, produced a degree of inhibition of the probe, and thus show some affinity for the DTS. This contrasts with previous reports that found several ACE inhibitors to be absorbed via a passive process, thus suggesting that compounds are capable of binding to the transporter site and inhibiting the probe without being translocated into the cell. This was also shown to be the case for oligodeoxynucleotide conjugated to a lipophilic group (vitamin E), and highlights the possibility that other orally administered drug candidates may exert non-specific effects on the DTS and possibly have a nutritional impact. Molecular modelling of selected ACE-NEP inhibitors revealed that the three carbonyl functions can be oriented in a similar direction, and this conformation was found to exist in a local energy-minimised state, indicating that the carbonyls may possibly be involved in hydrogen-bond formation with the binding site of the DTS.

Simultaneous chemical reaction and distillation of formaldehyde

The thesis is concerned with the development and testing of a mathematical model of a distillation process in which the components react chemically. The formaldehyde-methanol-water system was selected and only the reversible reactions between formaldehyde and water giving methylene glycol and between formaldehyde and methanol producing hemiformal were assumed to occur under the distillation conditions. Accordingly the system has been treated as a five component system. The vapour-liquid equilibrium calculations were performed by solving iteratively the thermodynamic relationships expressing the phase equilibria with the stoichiometric equations expressing the chemical equilibria. Using optimisation techniques, the Wilson single parameters and Henry's constants were calculated for binary systems containing formaldehyde which was assumed to be a supercritical component whilst Wilson binary parameters were calculated for the remaining binary systems. Thus the phase equilibria for the formaldehyde system could be calculated using these parameters and good accuracy was obtained when calculated values were compared with experimental values. The distillation process was modelled using the mass and energy balance equations together with the phase equilibria calculations. The plate efficiencies were obtained from a modified A.I.Ch.E. Bubble Tray method. The resulting equations were solved by an iterative plate to plate calculation based on the Newton Raphson method. Experiments were carried out in a 76mm I.D., eight sieve plate distillation column and the results were compared with the mathematical model calculations. Overall, good agreement was obtained but some discrepancies were observed in the concentration profiles and these may have been caused by the effect of limited physical property data and a limited understanding of the reactions mechanism. The model equations were solved in the form of modular computer programs. Although they were written to describe the steady state distillation with simultaneous chemical reaction of the formaldehyde system, the approach used may be of wider application.

Precise orbit determination and analysis from satellite altimetry and laser ranging

For optimum utilization of satellite-borne instrumentation, it is necessary to know precisely the orbital position of the spacecraft. The aim of this thesis is therefore two-fold - firstly to derive precise orbits with particular emphasis placed on the altimetric satellite SEASAT and secondly, to utilize the precise orbits, to improve upon atmospheric density determinations for satellite drag modelling purposes. Part one of the thesis, on precise orbit determinations, is particularly concerned with the tracking data - satellite laser ranging, altimetry and crossover height differences - and how this data can be used to analyse errors in the orbit, the geoid and sea-surface topography. The outcome of this analysis is the determination of a low degree and order model for sea surface topography. Part two, on the other hand, mainly concentrates on using the laser data to analyse and improve upon current atmospheric density models. In particular, the modelling of density changes associated with geomagnetic disturbances comes under scrutiny in this section. By introducing persistence modelling of a geomagnetic event and solving for certain geomagnetic parameters, a new density model is derived which performs significantly better than the state-of-the-art models over periods of severe geomagnetic storms at SEASAT heights. This is independently verified by application of the derived model to STARLETTE orbit determinations.

Gender and subject in higher education

This thesis is concerned with the issue of gender inequality in higher education. It examines the relationship between gender and subject specialisation, looking in particular at the reasons for the predominance, at undergraduate level, of men in the physical sciences, and of women in the humanities. It investigates ideas of `masculinity' and `femininity' and how these relate to constructions of `science' and `arts'. The thesis argues that students choose which subject to study on the basis of certain qualities these subjects are seen to hold, and that these qualities have close connections with beliefs about `masculinity' and `femininity'. It examines this through an interview study of male and female students on six higher education courses: two university courses of physics, two university courses of English, a polytechnic course in communications and a polytechnic course in physical science. The interview study demonstrates that the science subjects are perceived by science students as more certain, more useful and more important than the humanities, and emphasise the value of their degree in gaining a well-paid and important job. Female science students, however, experience conflict between being `a good scientist' and being `feminine'. English and communications students emphasise the breadth, uncertainty and individuality of their subjects, and find science restrictive and narrow. They make little link between their degree and their future career. Men, however, feel no conflict between their identity as men and their chosen subject. It is argued that there is a close link between the construction of masculinity and the construction of physical science, but that English and communications are more ambivalent: in some senses `masculine', in some `feminine'. Men are advantaged in these subjects because of their greater visibility and assertiveness. The thesis concludes that the division between `science' and `arts' reinforces ideas of masculinity and femininity, and argues that female `failure' in education is in part the result of higher education's inability to transcend that division.

Ecological studies on river pollution control

This collection of papers records a series of studies, carried out over a period of some 50 years, on two aspects of river pollution control - the prevention of pollution by sewage biological filtration and the monitoring of river pollution by biological surveillance. The earlier studies were carried out to develop methods of controlling flies which bred in the filters and caused serious nuisance and possible public health hazard, when they dispersed to surrounding villages. Although the application of insecticides proved effective as an alleviate measure, because it resulted in only a temporary disturbance of the ecological balance, it was considered ecologically unsound as a long-term solution. Subsequent investigations showed that the fly populations in filters were largely determined by the amount of food available to the grazing larval stage in the form of filter film. It was also established that the winter deterioration in filter performance was due to the excessive accumulation of film. Subsequent investigations were therefore carried out to determine the factors responsible for the accumulation of film in different types of filter. Methods of filtration which were considered to control film accumulation by increasing the flushing action of the sewage, were found to control fungal film by creating nutrient limiting conditions. In some filters increasing the hydraulic flushing reduced the grazing fauna population in the surface layers and resulted in an increase in film. The results of these investigations were successfully applied in modifying filters and in the design of a Double Filtration process. These studies on biological filters lead to the conclusion that they should be designed and operated as ecological systems and not merely as hydraulic ones. Studies on the effects of sewage effluents on Birmingham streams confirmed the findings of earlier workers justifying their claim for using biological methods for detecting and assessing river pollution. Further ecological studies showed the sensitivity of benthic riffle communities to organic pollution. Using experimental channels and laboratory studies the different environmental conditions associated with organic pollution were investigated. The degree and duration of the oxygen depletion during the dark hours were found to be a critical factor. The relative tolerance of different taxa to other pollutants, such as ammonia, differed. Although colonisation samplers proved of value in sampling difficult sites, the invertebrate data generated were not suitable for processing as any of the commonly used biotic indexes. Several of the papers, which were written by request for presentation at conferences etc., presented the biological viewpoint on river pollution and water quality issues at the time and advocated the use of biological methods. The information and experiences gained in these investigations was used as the "domain expert" in the development of artificial intelligence systems for use in the biological surveillance of river water quality.

Diagenesis and aquifer characteristics of the Sherwood Sandstone Group in North Nottinghamshire

The Sherwood Sandstone Group forms an important aquifer in Eastern England, which in North Nottinghamshire comprises the Nottingham Castle and Lenton Sandstone Formations. The aquifer is formed by an alluvial red-bed sequence dominated by medium-coarse grained sandstones which are texturally immature to submature and have only been subjected to shallow burial diagenesis. These sandstones reached the mature stage of the meso diagenetic regime, and four stages are recognized in their diagenetic history depending upon the physical/chemical processes prevailing and the subsequent effect on porosity and permeability. Stage "One" represents changes including dissolution of unstable silicates, clay replacement, red colouration and precipitation of authigenic minerals (quartz, feldspar, illite, l/S, kaolinite, dolomite, ferroan calcite, calcite). The net result of these changes was porosity reduction. Stage "Two" included changes due to mechanical compaction which resulted in minor porosity reduction. Stage "Three" was the main phase of secondary porosity enhancement. Stage "Four" represents changes taking place in the present groundwater where porosity and permeability may have been increased by dissolution and partly reduced by kaolinite precipitation. Porosity measured by water-resaturation and Hg-injection gave average values of 25.63% and 24.85% respectively. The results are comparable and showed marked correlation especially in highly porous/permeable rocks. Porosity measurements from photomicrographs were markedly offset from laboratory results. Horizontal Kw ranged between 1.43 x 10-5 and 1.13 x 10-1 mm/sec, with an average of  1.68 x 10-2 mm/sec. The estimated KHg ranged between 7.29 x 10-6 and 6.99 x 10-2 mm/sec with an average of 1.47 x 10-2 mm/sec. Both results are significantly correlated for highly porous/permeable rocks. The hydraulic properties are highly dependent upon the diagenetic properties (as most of the pores present are of secondary origin) as well as the pore size distribution. The chemistry of these groundwaters indicates that they are under-saturated with respect to dolomite, calcite, K-feldspar, l/S clay, and montmorillonite. The precipitation of kaolinite,and to a lesser extent illite, is favoured in the present groundwater regime.

Sedimentology, palaeontology and diagenesis of the Much Wenlock limestone formation

Lithofacies distribution indicates that the Much Wenlock Limestone Formation of England and South Wales was desposited on a shelf which was flat and gently subsiding in the north, but topographically variable in the south. Limestone deposition in the north began with 12m of alga-rich limestone, which formed an upward shoaling sequence. Deepening then led to deposition of calcareous silty mudstones on the northern shelf. The remainder of the formation in this area formed during a shelf-wide regression, culminating in the production of an E to W younging sandbody. Lithofacies distribution on the southern shelf was primarily controlled by local subsidence. Six bedded lithofacies are recognised which contain 14 brachiopod/bryozoan dominated assemblages, of which 11 are in situ and three consist of reworked fossils. Microfacies analysis is necessary to distinguish assemblages which reflect original communities from those which reflect sedimentary processes. Turbulence, substrate-type, ease of feeding and other organisms in the environment controlled faunal distribution. Reefs were built dominantly by corals, stromatoporoids, algae and crinoids. Coral/stromatoporoid (Type A) reefs are common, particularly on the northern shelf, where they formed in response to shallowing, ultimately growing in front of the advancing carbonate sandbody. Algae dominate Type B and Type C reefs, reflecting growth in areas of poor water circulation. Lithification of the formation began in the marine-phreatic environment with precipitation of aragonite and high Mg calcite, which was subsequently altered to turbid low Mg calcite. Younger clear spars post-date secondary void formation. The pre-compactional clear spars have features which resemble the products of meteoric water diagenesis, but freshwater did not enter the formation at this time. The pre-compactional spars were precipitated by waters forced from the surrounding silty mudstones at shallow burial depths. Late diagenetic products are stylolites, compaction fractures and burial cements.

Recent and Miocene carbonate sediments from Indonesia. Available in 2 volumes.

Mapping and sediment sampling in reefs of the Pulau Seribu group (southwest Java Sea) shows the existence of ten physiographic zones and subzones represented by seven lithofacies. Reefs in the northern part of the archipelago are smaller, more closely spaced and morphologically sim pler than those in the south. This pattern is attributed to differences in subsidence rate. A th reedimensional model is proposed for the evo lution of these reefs but borehole data are requi red to test this model. Miocene limestones are described in detail from hydrocarbon reservoirs in the Batu Raja Formation of the same area. Brief comparisons a re made with surface outcrops of approximately coeval carbonate developments. The lithofacies developed within these limestones reflect variations in hydrodynam ic regime and basement topography . Ele\le.n diagenetic processes affected the Batu Raja limestones and the dist ribution of these is primarily related to sealevel fluctuations. Early diagenesis was marine and characterised by micritisation and preCipitation of fibrous and bladed cements. Dolomitisat ion occurred in the mixed- water zone and its variable intensity is attributed to the configuration of the carbonate body relative to this zone. Subsequently the limestones were subjected to freshwater phreatic zone diagenesis resulting in dissolution and cementation, and a t a late stage underwent burial compaction. Secondary porosity, which \ar9e1.y determines the suitability of these limestones as hydrocarbon reserVOirs, is a function of the variable intensity of dissolution and cementation, burial compaction, dolomitisation and possibly micrite neomorphism. The sedimentary processes that generated the Batu Raja buildups are inferred f rom comparisons with the Pulau Seribu and other Recent analogues. The contrasting pinnacle form of the Pulau Seribu patch reefs compared with the low relief of the Batu Raja buUdups results from differences in the initial substrate topography and subsequent subsidence rate

Business information systems:technology, development and management in the E-business

Information technology is at the centre of today’s business environment. The increasing importance of e-commerce and the integration of information systems in all areas of a business means it is crucial for managers to understand and implement IS (information systems). This major text, now in its second edition, provides the skills and knowledge necessary to choose the right systems, and to develop and manage them effectively. Business Information Systems: Technology, Development and Management assumes no prior knowledge of IS or IT, and emphasises the importance of IS to management decision making. It takes a 3 part structure: Part One covers hardware and software technologies; Part Two looks at information systems analysis and design; and Part Three describes the strategic management of IS. This successful format allows each section to be studied alongside individual modules, and enables students to focus clearly on specific areas and use the book for more than one course. This book is suitable for college students, undergraduate degree and postgraduate students taking courses with modules in the practical IT skills of selection, implementation, management and use of BIS. The practical sections are also of use to managers in industry involved in the development and use of IS.

DesaLink:solar powered desalination of brackish groundwater giving high output and high recovery

Desalination of groundwater is essential in many arid areas that are far from both seawater and fresh water resources. The ideal groundwater desalination system should operate using a sustainable energy source and provide high water output per land area and cost. To avoid discharging voluminous brine, it should also provide high recovery. To achieve these aims, we have designed DesaLink, a novel approach to linking the solar Rankine cycle to reverse osmosis (RO). To achieve high recovery without the need for multiple RO stages, DesaLink adopts a batch mode of operation. It is suited to use with a variety of solar thermal collectors including linear Fresnel reflectors (LFR). For example, using a LFR occupying 1,000m of land and providing steam at 200°C and 15.5 bar, DesaLink is predicted to provide 350m of fresh water per day at a recovery ratio of 0.7, when fed with brackish groundwater containing 5,000ppm of sodium chloride. Here, we report preliminary experiments to assess the feasibility of the concept. We study the effects of longitudinal dispersion, concentration polarisation and describe a pilot experiment to demonstrate the batch process using a materials testing machine. In addition, we demonstrate a prototype of DesaLink running from compressed air to simulate steam.

The development of Cannabidiol as a psychiatric therapeutic:a review of its antipsychotic efficacy and possible underlying pharmacodynamic mechanisms

Cannabidiol (CBD), a once-considered inert cannabis constituent, is one of two primary constituents of cannabis, alongside delta-9-tetrahydrocannabinol (?9-THC/THC). In the last 30 years, CBD has become implicated with a range of pharmaceutical mechanisms of great therapeutic interest and utility. This review details the literature speculating CBD’s attenuation of psychotic symptoms, particularly in light of a marked elevation in mean THC concentrations, and a concomitant decline in CBD concentrations in the prevalent U.K street market cannabis derivatives since c. 2000. CBD is purported to exhibit pharmacology akin to established atypical antipsychotics, whilst THC has been implicated with the precipitation of psychosis, and the induction of associated symptoms. The aim of the review was to clarify the conjecture surrounding CBD’s antipsychotic efficacy, before going on to detail prominent theories about its associated pharmacodynamics. Were CBD’s antipsychotic efficacy established, then there is potential for major latent anthropological repercussions to manifest, such as significant elevations in psychosis manifestations in the U.K. The review found a largely affirmative body of evidence asserting CBD’s antipsychotic efficacy. CBD exhibited capacity to attenuate natural and artificially induced psychoses in both animal and human cohorts, the latter of which included individuals considered resistant to conventional treatment. CBD also shows promising potential for use as an antipsychotic drug for Parkinson’s disease (PD) patients with psychosis, owing to its low rate of extra-pyramidal side-effect induction. A range of potential pharmacological mechanisms behind CBD’s neuroleptic pharmacology are outlined, with particular emphasis on its prevention of the hydrolysis and reuptake of the endogenous cannabinoid, anandamide. However, given the nebular aetiological basis for psychoses, explicit conclusions on how CBD attenuates psychotic symptoms remains to be determined.

Precipitation studies on alloys from the system copper chromium zirconium

The precipitation reactions occurring in a series of copper-based alloys selected from the system copper-chromium-zirconium have been studied by resistometric and metallographic techniques. A survey of the factors influencing the development of copper-based alloys for high strength, high conductivity applications is followed by a more general review of contemporary materials, and illustrates that the most promising alloys are those containing chromium and zirconium. The few systematic attempts to study alloys from this system have been collated, discussed, and used as a basis for the selection of four alloy compositions viz:- Cu - 0.4% Cr Cu - 0.24. Zr Cu - 0. 3% Cr - 0.1% Zr Cu - 0.2% Cr - 0.2% Zr A description of the experimental techniques used to study the precipitation behaviour of these materials is preceeded by a discussion of the currently accepted theories relating to precipitate nucleation and growth. The experimental results are presented and discussed for each of the alloys independently, and are then treated jointly to obtain an overall assessment of the way in which the precipitation kinetics, metallography and mechanical properties vary with alloy composition and heat treatment. The metastable solid solution of copper-chromium is found to decompose by the rejection of chromium particles which maintain a coherent interface and a Kurdjumov-Sachs type crystallographic orientation relationship with the copper matrix. The addition of 0.1% zirconium to the alloy retards the rate of transformation by a factor of ten and modifies the dispersion characteristics of the precipitate without markedly altering the morphology. Further additions of zirconium lead to the growth of stacking faults during ageing, which provide favourable nucleation sites for the chromium precipitate. The partial dislocations bounding such stacking faults are also found to provide mobile heterogeneous nucleation sources for the precipitation reactions occurring in copper-zirconium.

Perspectives on supply chain management and logistics:creating competitive organisations in the 21st Century

Globalisation is the buzzword of the twenty-first century. It forces businesses to compete not just with rivals within the same city or country, but with similar companies across the globe. In such a world the consumer is king and to keep on top businesses must show constant innovation and meet customers' ever-growing expectations. Supply chain management (SCM), with its focus on achieving the service levels demanded by markets and on optimising total supply chains cost and investment, has a potentially pivotal role to play in addressing these challenges. Perspectives on Supply Chain Management and Logistics is written by a mix of academics, consultants and practitioners, all of whom have significant theoretical and practical experience. The book was conceived with the many supply chain and logistics professionals who are following formal learning programmes at all levels (Certificate, Diploma, Degree and Masters) in the subject in mind. However, it is hoped that it will be read equally profitably by students, researchers and practicing SCM and logistics professionals.

Human intervertebral disc aggrecan inhibits endothelial cell adhesion and cell migration in vitro

STUDY DESIGN: The effect of human intervertebral disc aggrecan on endothelial cell growth was examined using cell culture assays. OBJECTIVE: To determine the response of endothelial cells to human intervertebral disc aggrecan, and whether the amount and type of aggrecan present in the intervertebral disc may be implicated in disc vascularization. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration has been associated with a loss of proteoglycan, and the ingrowth of blood vessels and nerves. Neovascularization is a common feature also of disc herniation. Intervertebral disc aggrecan is inhibitory to sensory nerve growth, but the effects of disc aggrecan on endothelial cell growth are not known. METHODS: Aggrecan monomers were isolated separately from the anulus fibrosus and nucleus pulposus of human lumbar intervertebral discs, and characterized to determine the amount and type of sulfated glycosaminoglycan side chains present. The effects of these aggrecan isolates on the cellular adhesion and migration of the human endothelial cell lines, HMEC-1 and EAhy-926, were examined in vitro. RESULTS: Homogenous substrata of disc aggrecan inhibited endothelial cell adhesion and cell spreading in a concentration dependent manner. In substrata choice assays, endothelial cells seeded onto collagen type I migrated over the collagen until they encountered substrata of disc aggrecan, where they either stopped migrating, retreated onto the collagen, or, more commonly, changed direction to align along the collagen-aggrecan border. The inhibitory effect of aggrecan on endothelial cell migration was concentration dependent, and reduced by enzymatic treatment of the aggrecan monomers with a combination of chondroitinase ABC and keratinase/keratinase II. Anulus fibrosus aggrecan was more inhibitory to endothelial cell adhesion than nucleus pulposus aggrecan. However, this difference did not relate to the extent to which the different aggrecan isolates were charged, as determined by colorimetric assay with 1,9-dimethylmethylene blue, or to marked differences in the distribution of chondroitin sulfated and keratan sulfated side chains. CONCLUSIONS: Human intervertebral disc aggrecan is inhibitory to endothelial cell migration, and this inhibitory effect appears to depend, in part, on the presence of glycosaminoglycan side chains on the aggrecan monomer.