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Yayın Photon transmission study on conformational ordering of iota-carrageenan in CaCl2 solution(Taylor & Francis Inc, 2005-06) Kara, Selim; Pekcan, Mehmet ÖnderCoil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of iota-carrageenan in CaCl2 solution upon cooling were studied using photon transmission technique. Photon transmission intensity, I-iota r was monitored against temperature to determine the (c-h) and (h-d) transition temperatures (T-ch and T-hd) and activation energies (Delta E-ch and Delta E-hd). An extra dimer-to-dimer (d-d) transition was also observed during cooling at low temperature region. However, upon heating dimers disappear to double helices by making dimer-to-double helix (d-h) transition. Further heating resulted double helix-to-coil (h-c) transition at high temperature region. T-dh and T-ch temperatures and Delta E-dh and Delta E-hc activation energies were also determined. It was observed that T-hc and T-ch temperatures and Delta E-dh and Delta E-hd activation energies do not effected by carrageenan content. However, T-hd, T-dh and T-dd temperatures and Delta E-ch and Delta E-hc activation energies were found to be strongly correlated to the carrageenan content in the system.Yayın Small molecule diffusion into swelling Iota-Carrageenan gels: A fluorescence study(Taylor & Francis Group, 2007-04) Ataman, Evren; Pekcan, Mehmet ÖnderSmall molecule diffusion into Iota-Carrageenan gel was studied by using steady-state fluorescence (SSF) technique. Pyranine, dissolved in water was used as fluorescence probe. Fluorescence emission intensity, I-p, and scattered light intensity, I-sc, were monitored to study diffusion and swelling processes at various temperatures respectively. Fickian and Li-Tanaka models were elaborated to produce diffusion, D, and collective diffusion, D-0, coefficients. Diffusion and swelling activation energies were also obtained and found to be 20.5 kj mol(-1) and 28.2 kj mol(-1). respectively.Yayın Synergistic effect of the locust bean gum on the thermal phase transitions of kappa-carrageenan gels(Elsevier Sci Ltd, 2009-03) Arda, Ertan; Kara, Selim; Pekcan, Mehmet ÖnderSynergism between K-carrageenan and locust bean gum (LBG) was studied using the photon transmission technique. Synergistic effects in these polymeric mixtures strongly affected the physical properties of the gel structure. The transmitted light intensities, I-tr, versus temperature variations were investigated during the gelation and liquefaction processes. Slight synergistic peaks were detected in gel-sol and sol-gel transition temperatures for high kappa-carrageenan/LBG ratios (approx. 80/2). Moreover, apparent synergistic peaks were observed in gel-sol and sol-gel transition activation energies for the mixtures approximately with the ratios of 80/10.
