Molecular recognition during sol–gel and gel–sol transition of kappa–iota carrageenan mixtures (original) (raw)

Phase transitions of κ-carrageenan gels in various types of salts

Journal of Applied Polymer Science, 2006

Sol-gel and gel-sol phase transitions of k-carrageenan in various types of salts were studied using photon transmission technique. Here, LiCl, NaCl, KCl, MgCl 2 , CaCl 2 , and SrCl 2 were chosen as the proper salts for the k-carrageenan-water system. Photon transmission intensity, I tr was monitored against temperature to determine the sol-gel and gel-sol temperatures (T sg and T gs ) and activation energies (DE sg and DE gs ). It was observed that T gs temperatures were notably higher than T sg due to the hysteresis on the phase transition loops. It was observed that stronger carrageenan gels are formed in the presence of KCl compared to the others.

Monovalent and Divalent Cation Effects on Phase Transitions of -carrageenan

Journal of Bioactive and Compatible Polymers, 2007

Phase transitions of -carrageenan in a variety of monovalent (Li, Na, K) and divalent (Mg, Ca, Sr) cation solutions were studied during heating and cooling by using photon transmission technique. Photon transmission intensity (I tr ) was monitored against temperature to determine the transition temperatures and activation energies during the heating and cooling processes in the monovalent and divalent systems. Three distinct transition regions were observed during the heating and cooling cycles for the carrageenan-divalent salt system. At the first step of the heating process, dimer groups were transformed into dimers that presented (g-d) transitions, then these dimers were directly converted into a double helix by undergoing a (d-h) transition. In the higher temperature region, a double helix-to-coil (h-c) transition took place. During the cooling process, these transitions are arranged in the order of (c-h), (h-d), and (d-g). The carrageenan-monovalent salt system presented only coil-to-rod-like helix (c-r) and rod-like helix-to-coil (r-c) transitions during the cooling and heating processes, respectively. A hysteresis was observed between (r-c)-(c-r) and (g-d)-(d-g) transitions for the monovalent and divalent cations, respectively.

Cation effect on thermal transition of ι-carrageenan: a photon transmission study

Journal of Biomaterials Science, Polymer Edition, 2005

Coil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of ι-carrageenan in various cation (CaCl 2 ) solutions upon heating and cooling were studied using the photon transmission technique. Photon transmission intensity, I tr , was monitored against temperature to determine the (c-h) and (h-d) transition temperatures (T ch and T hd ) and activation energies ( E ch and E hd ). An extra dimer-to-dimer (d-d) transition was observed during cooling at low temperature region. However, upon heating dimers directly decompose into double helices by making dimerto-double helix (d-h) transition. Further heating results in double helix-to-coil (h-c) transition at high temperature region. T dh and T hc temperatures and E dh and E hc activation energies were determined. It was observed that T hc and T ch temperatures and E ch and E hc activation energies were found to be strongly correlated to the CaCl 2 content in the system.

Cation effects on sol–gel and gel–sol phase transitions of κ-carrageenan–water system

International Journal of Biological Macromolecules, 2003

Carrageenan gels prepared with various carrageenan concentrations in pure water were completely dried and then swelled in pure water. Photon transmission measurements were performed using a UV-Vis (UVV) spectrometer during the swelling of -carrageenan gels. Transmitted photon intensity, I tr , increased exponentially as swelling time is increased for all gel samples. The behaviour of I tr was interpreted by Monte-Carlo Simulation. The increase in I tr was quantified by employing Li-Tanaka equation, from which time constants τ 1 and collective diffusion coefficients, D o were determined for the gels in various carrageenan concentrations. Gravimetric and volumetric measurements were also carried out during swelling of gels. It is observed that gel with high carrageenan content possess more double helices and more lattice dislocations and swell slower than gels with low carrageenan content which may contain less double helices and less lattice imperfections. Increase in I tr was interpreted by the homogeneous distribution of double helices in the carrageenan gel system.

Cation effects on phase transition of kappa-iota-carrageenan hybrids: a photon transmission study

Composite Interfaces, 2007

A steady-state fluorescence technique was employed to study the swelling of j-carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. The fluorescence intensity of pyranine was measured during the in situ swelling process of j-carrageenan gels. The fluorescence intensity increased exponentially as the swelling time increased. The increase in the fluorescence intensity was modeled with the Li-Tanaka equation, from which the swelling time constants and cooperative diffusion coefficients were determined. The swelling time constants decreased and the cooperative diffusion coefficients increased as the swelling temperature was increased. The swelling activation energies were measured to be 47.05 kJ/mol.

Study of thermal phase transitions in iota carrageenan gels via fluorescence technique

Journal of Applied Polymer Science, 2011

The effect of carrageenan concentration on thermal phase transitions of the iota carrageenan gels was investigated by using fluorescence technique. During heating and cooling processes, scattered light, I sc , and fluorescence intensity, I p , were monitored against temperature to investigate phase transitions. Transition temperatures from the derivative of the transition paths were determined. Two regions were observed during the heating and cooling processes. At the first step of the heating, dimers were converted into double helix by undergoing dimer to double helix (d-h) transition. At the higher tem-perature region, double helix to coil (h-c) transition took place. During the cooling process, these transitions are arranged in the order of coil to double helix (c-h) and double helix to dimer (h-d). A hysteresis was observed between (h-d) and (d-h) transitions. The critical gel fraction exponents, b, were found to be independent of the system by indicating that they all fall into the same universality class.

Photon Transmission Study on Conformational Ordering of Iota-Carrageenan in CaCl 2 Solution

Journal of Biomolecular Structure and Dynamics, 2005

Coil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of ι-carrageenan in CaCl 2 solution upon cooling were studied using photon transmission technique. Photon transmission intensity, I tr was monitored against temperature to determine the (c-h) and (hd) transition temperatures (T ch and T hd ) and activation energies (∆E ch and ∆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 ∆E dh and ∆E hc activation energies were also determined. It was observed that T hc and T ch temperatures and ∆E dh and ∆E hd activation energies do not effected by carrageenan content. However, T hd , T dh and T dd temperatures and ∆E ch and ∆E hc activation energies were found to be strongly correlated to the carrageenan content in the system.

Cation effect on gel – sol transition of kappa carrageenan

Polymer Bulletin, 2008

A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of kcarrageenan (kappa carrageenan) gels at various temperatures. kcarrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in kcarrageenan and used as a fluorescence probe. Scattered light intensities, I sc and fluorescence intensities, I were monitored during the drying and swelling of kcarrageenan gels. It was observed that the fluorescence intensity decreased linearly as drying time was increased. A simple model consisting of Case II diffusion was used to quantify the drying processes of the kcarrageenan gels. This moving boundary model provided packing constant, k 0 . During swelling, fluorescence intensity increased exponentially as time is increased. The increase in I, was modeled using Li-Tanaka equation from which swelling time constants, t c and cooperative diffusion coefficients, D c were determined. It was observed that swelling time constants, t c decreased and diffusion coefficients, D c increased as the swelling temperature was increased. Activation energies for drying and swelling were also obtained and found to be 53.9 and 47.2 kJ mol À1 , respectively.