Browsing by Author "Hailemichael Goitom, Aron"

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    Identification of the putative urinary intraspecific recognition pheromone of the caracal caracal caracal
    (Stellenbosch : Stellenbosch University, 2017-03) Hailemichael Goitom, Aron; Burger, B. V.; De Villiers, Andre J.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: Sheep husbandry makes a considerable contribution to the economy of South Africa. However, it has been pressure during the last few decades due to the rapidly growing numbers of predators such as the caracal, Caracal caracal, and the red jackal, Canis mesomelas. Currently, sheep farming is hardly viable in the arid southern parts of the country. When experimenting with various methods of controlling caracal numbers, sheep farmers found that this problem animal could be effectively lured into traps using the urine of another male or female caracal. The main disadvantage here is that a sheep farmer could incur serious stock losses before he is able to obtain a starting sample of urine from another source (e.g., another farmer). It was hypothesised that caracal urine contains a volatile organic substance, or substances (VOCs), that are involved in the semiochemical communication between members of this species. The objective of this investigation was to identify these putative attractants in the urine, for the subsequent formulation of a caracal lure composed of synthetic analogues of the natural VOCs. As sheep farmers reported that male and female urine were equally effective attractants, it was considered unlikely that the attracting agent could be a sex pheromone; rather, it could have an intraspecific signalling function. Efforts were made to identify all the VOCs present in caracal urine samples donated by farmers from different sheep farming areas of the country. A total of 191 VOCs, including five steroid hormones, were identified. The identification of 86% of these VOCs was corroborated by gas chromatographic-mass spectrometric (GC-MS) comparison of the natural substances with authentic synthetic analogues. Obligate proteinuria is known in certain animals, in which it is not an indicator of renal abnormality. In the house mouse, Mus domesticus, for example, so-called major urinary proteins (MUPs) bind dehydro-exo-brevicomin and 2-(sec-butyl)-4,5-dihydrothiazole elicit male aggression. The carboxylesterase-like urinary excreted pheromone-binding protein, also known as cauxin, has been identified in the urine of several felids, but was not found in caracal urine. However, the pheromone-binding proteins ‘Transgelin fragment (M3WJ37)’ and ‘Uncharacterized protein (M3XEJ0)’, both previously identified in Felis catus and Felis silvestris catus, were identified in caracal urine. The macrocyclic C15 ketone, cyclopentadecanone, was identified as one of the VOCs present in the headspace gas of caracal urine. The headspace concentration of this ketone increased when the urine was heated at 95 ºC for 10 min. A similar, but more pronounced increase in cyclopentadecanone concentration was observed when urinary protein present in caracal urine was denatured by subjecting it to similar treatment. This was interpreted as an indication that this ketone is a ligand of caracal urinary protein. The C13, C14, C16, and C17 macrocyclic ketones were subsequently also identified as urinary protein ligands. In bioassays, a mixture of synthetic analogues of a large number of the other ketones identified in caracal urine, including cyclopentadecanone, elicited typical feline behaviour in two male caracal in captivity. Similar behavioural patterns were observed when a mixture of the C13, C14, C15, and C16 macrocyclic ketones were tested. It was concluded that these ketones, that are ligands of the caracal’s urinary protein, could play an essential role in the intraspecific communication of the caracal.
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    Indirect capillary electrophoretic detection methods of cations and anions
    (Stellenbosch : Stellenbosch University, 2004-12) Hailemichael Goitom, Aron; Crouch, A. M.; Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science.
    ENGLISH ABSTRACT: Capillary electrophoresis (CE) has recently attracted considerable attention as a promising analytical technique for the separation of cations and anions in complex matrices. Determination of ions in aqueous samples using capillary electrophoresis can be accomplished with indirect UV detection. Most inorganic ions have weak absorption profiles in the UV-Vis wavelength range. These mostly non-absorbing species are commonly detected by indirect UV absorbance through addition of an absorbing co-ion (chromophore) into the electrolyte. Inorganic cations most often require an additional complexing agent to selectively alter their similar mobilities and proper separation. For optimal determination of alkali, alkaline, and transition metal ions, several electrolytes systems were studied. These include pyridine, imidazole and 4- aminopyridine as UV-absorbing species and glycolic acid, a-hydroxyisobutyric acid and their mixture were used as complexing reagents. A mixture of 10 metal ions (K+, Na+,Ca2+, Mg2+, Mn2+, Fe2+, Cd2+, Pb2+, Ni2+and Zn2+) was successfully separated. Detectionwas performed at 210,214 and 254 nm. In the anion determination chromate and 2, 6 pyridine dicarboxylic acids (PDC) were used as back ground electrolytes for inorganic ions (F-, CI- en SO₄² ̄ ) and organic acids (tartaric acid, malic acid, succinic acid and citric acid) separations respectively. Electroosmotic flow (EOF) was reversed in the direction of the anode by adding Cetyltrimethylammonium bromide (CTAB) to the electrolyte. Highly alkaline conditions were used to confer a negative charge on inorganic and organic anions to promote their migration towards the anode. The detection wavelength was 200 nm. All peaks were completely resolved and well separated. The limit of detection (LOD) of cations and anions were in the range of 0.5 - 3 ppm and 2 - 3.5 ppm respectively. The described methods were used successfully in routine analysis of real samples. This includes the qualitative and quantitative analysis of an environmental water samples from the areas surrounding Stellenbosch, beverages and orange juice.