No description available.

No description available.

Chromone and flavanone derivatives were prepared by condensation of the corresponding 2-hydroxyacetophenones (with diethyl oxalate or the appropriate aromatic aldehyde respectively) and cyclisation of the condensation products. Saeyer-Villiger rearrangement of these flavanones, with MCPBA, resulted in expansion of the C-ring. Spectroscopic techniques have been used to establish the regioselectivity of the rearrangement and hence, the identity of the rearranged products as 1,5-benzodioxepan-4-ones. The 1,5-benzodioxepan-4-ones were subjected to detailed ¹H and ¹³C n.m.r. analysis and a combination of low and high resolution mass spectrometry has been used to study the mass fragmentation pathways of these ring-expanded products.

Field and laboratory studies were undertaken to examine the ecological role of colouration in the penpoint gunnel Apodichthys flavidus, its structural basis and possible origin. A. flavidus was found to vary in colour from green through brown to red. The vast majority of fish collected matched at least one type of vegetation from their habitat. Those observed directly within vegetation were of the same colour as the vegetation. In habitat selection experiments A. flavidus was found to prefer cover under rocks to that within vegetation, but when provided with vegetation alone chose that which it matched. The colour phases observed in A. flavidus were found to be determined directly by the pigments they contained not by differences in stages of chromatophore expansion. Green fish owe their colour primarily to esterified dihydroxy ε carotene conjugated with a protein and dispersed throughout the integument. The colour of red fish results primarily from esters of astaxanthin contained in erythrophores. Brown fish incorporate the colouration systems of both the red and green phases, but the modifications involved have not been fully worked out. Colour change experiments showed that A. flavidus cannot undergo complete changes of colour phase in response to environment alone. Diet has an influence on colour, but complete colour changes were not produced experimentally. Larvae were reared from the eggs of green and brown individuals. All developed colouration more similar to that of the Artemia upon which they were fed than to their parental type. This evidence is discussed in terms of a possible dietary origin of colour variation and weighed against polymorphism. It is suggested that the colouration of A. flavidus has a cryptic function which is of importance primarily during food seeking. It is hypothesized that the vegetation upon which A. flavidus larvae settle in conjunction with early diet primarily determines the colouration of individuals. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

No description available.

No description available.

No description available.

Following an earlier study of different coloured pigments used in Roman wall-plaster paintings, this research project investigates the use of the synthetic pigment commonly known as Egyptian Blue in Romano-British wall-plaster paintings. Samples of Egyptian Blue pellets were obtained from excavations at the Romano-British sites of Fishbourne Roman Palace, near Chichester, Piddington near Northampton, Turners Hall Farm, near St Albans, and from excavations at Verulamium (Roman St Albans). The aim of this study is to determine the chemical composition, fabric and texture of each pellet as well as attempting a textural and geochemical classification of the pellets, using well established analytical techniques, particularly LA-ICP-MS and SEM-EDAX. The colour of the pellets was examined and identified using the Munsell Book of Color (Matte Finish Collection) 1973. The results of the analysis of the Egyptian Blue pellets found on Romano-British sites showed that differing amounts of silica, copper, calcium, as well as smaller amounts of other elements, were used in their manufacture. Most of the pellets examined appear to have been manufactured locally, though some were almost certainly imported. Experimental work was undertaken, both in the laboratory and out in-the-field where a reconstructed Bronze Age Clamp Kiln and an Iron Age Belgic Kiln were used, to reproduce the synthetic pigment Egyptian Blue, using a recipe similar to that used by earlier investigators. Such recently manufactured Egyptian Blue pellets were applied, as a pigment, to damp lime mortar, in an attempt to correlate the achieved colour with the firing time. Similar techniques were used in an attempt to ascertain the nature of the pigments used on the small fragments of painted wall-plaster found in a back filled trench, from Wheeler's 1930 - 33 excavations at Verulamium. On two of the fragments gas chromatographic analysis was applied to determine the nature of the binding material that might have been used. This study is thought to be the first in-depth investigation of Romano-British Egyptian Blue pellets and thereby contributes to the art history and archaeological knowledge of this period.

The mechanism of protection by carotenoids against photodynamic killing in Curtobacterium flaccumfaciens pathover poinsettiae (C. poinsettiae) was studied using pigment mutants isolated by treatment with nitrosoguanidine and DNA gyrase inhibitors. Growth rates, pigment composition, pigment levels and the ultrastructure of the wild-type streptomycin resistant strain of G. poinsettiae (wt-str) and all mutants were compared. One mutant, NTG-1, lacked colored carotenoids, and another, NTG-2, was a slow growing mutant containing low levels (14%) of wild-type carotenoid pigments. Except for NTG-1, the other pigment mutants had different proportions of the same pigments found in the wild type as determined by high performance liquid chromatography (HPLC). Only NTG-2 was morphologically distinct at the ultrastructural level.