PURSE 1996

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/43

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Browsing PURSE 1996 by Subject "Chemistry"

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    Chemical Variations of Uncaria Ellipitca
    (University of Peradeniya, Peradeniya, 1996-08-10) Chandrasena, W. D.; Diyabalanage, T. K. K.; Wannigama, G. P.
    Uncaria elliptica is a woody climber, widely distributed in South and South East Asia. The species collected in Thailand and the species collected in Malaysia show chemical variations. This investigation reports chemical variations of the species within Sri Lanka itself Samples of the species were collected from the Kanneliya (KN) and Udawattakelle (UK) forest reserves. The KN plant and the UK plant showed minor differences in their triterpenoid compositions. The alkaloids of the two plants showed more striking differences. The KN plant gave ajmalicine, incorporating one molecule of tryptamine and one molecule of secologanin. The UK plant gave no ajmalicine, but gave the roxburghines, incorporating two molecules of tryptamine and one molecule of secologanin. The roxburghines are unique to the genus and among its 34 species, are found only in Uncaria elliptica.
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    Construction of an Improved Automatic Burette
    (University of Peradeniya, Peradeniya, 1996-08-10) Tennakoon, D. T. B.; Bandara, H. M. N.; Chandrasena, W. D.; Ilangantilake, A. N.
    We have previously described the construction of an automatic burette with the ability to detect the colour change at the end point. An ordinary burette modified for the purpose was used to control the addition of the titrant and the vohune was read visually. This instrument is now improved and the burette is replaced with a motor-driven plastic syringe. Once calibrated, the instrument is able to add and measure the vohune of the titrant with a high degree of accuracy. The process is fully computer controlled.
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    Factors Affecting the In-Situ conductivity of electronically conducting Polymers
    (University of Peradeniya, Peradeniya, 1996-08-10) Vidanapathirana, K. P.; Senadeera, G. K. R.; Guanratne, L. M. W. K.; Kareem, A. M.; Dissanayake, M. A. K. L.
    In recent years the discovery of doped organic polymers with high electronic conductivities has generated substantial research interest among physicists and chemists. Conjugated polymers such as polyacetylene, polypyrrole, polythiophene, polyparaphenylene with doped derivatives reported to have conductivities larger than 1 S/cm. The films obtained in organic media exhibit superior characteristics in favour of their conductivity and mechanical properties. However, the use of organic solvent is costly and hazardous. Hence the use of water as a solvent for the polymerization is evidently advantageous. Therefore, in this study, investigations have been carried out to find the effect of pH of the electrolyte, effect of the size of the dopant ion, effect of the electrolyte concentration and the effect of the current density used in the polymerization on the in-situ conductivity of poly N methyl pyrrole in aqueous media. The polymerization current density has the largest influence on the conductivity. The conductivity increase with the decreasing current density. pH of the electrolyte also effects the conductivity. The films formed using higher acidic media seems to have high conductivity. As seen in the non aqueous media, the conductivity changes with the size of the anion and the concentration of electrolyte.
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    Premary Study on the Protein Chemistry of Goat Milk
    (University of Peradeniya, Peradeniya, 1996-08-10) Weerabadda, W. K. C.; Horadagoda, A.; Wijewardena, T. G.
    Incidence of food allergy can increase with the introduction of cow milk/(Wood 1986). Food allergy is the clinical syndrome resulting from sensitisation of an individual to dietary proteins or other allergens present in the intestinal1umen. Cow milk allergy is common during infancy however, it is not confined to childhood (Deamer. Gerrard and Speer 1979). Allergic response elicited by cows milk may be attributed to its soluble whey proteins and such persons are prescribed goat milk or cow milk products such as yoghurt which they appear to tolerate well. Unlike cow milk, there is a dearth of information on the composition and chemistry of goat milk proteins which may be responsible for the aforementioned favourable effect. In this study, proteins in goat milk have been analysed and compared with those of human milk, cow milk and yoghurts (made out of cow milk) in order to understand the reasons for this differences in the allergic responses. Twenty five samples of milk were collected from each species. In the cow and the goat these were collected at different stages of lactation but it was ensured that equal numbers per stages were collected in each species. In the human all samples were from early lactation. All the samples were analysed for total protein, casein, whey proteins by using both Kjeldhal and Biuret assays and further analysed by Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE). The electrophoretic patterns of proteins in individual samples were compared with that of the commercially available milk protein standards. The average total protein concentration (g/I) of goat milk, cow milk, human milk and yoghurt was 35.2, 33.5, 8.3 and 33.0 respectively. The casein concentration and the whey proteins for the three species were 29.1,24.1,2.4 and 6.13,9.51, 5.97 (g/I) respectively. Casein to whey protein ratio was high in cow and goat milk and in human the ratio was very much lower. SDS-PAGE revealed that goat milk had similar protein bands to that of cow milk but during the preparation of yoghurt the whey protein fraction of fresh milk has reduced and SDS-PAGE showed lighter whey protein bands in the yoghurt. Further studies are in progress to identify and quantitate the different proteins of these milks and their products.