The Presence of Novel Plant Growth Regulators in Leaves of Distylium racemosum Sieb et Zucc

The scaling law derived from the percolation theory was applied to the concentration dependence of mechanical properties of polyacrylamide measured near the sol–gel transition point. The critical concentration of the sol–gel transition, ?_g, was estimated from the plot of concentration (?) vs. the reciprocal of viscosity (η) by extrapolating 1/η to zero. The critical exponent for the sol viscosity, s, which was estimated from the slope of the log(?_g–?) vs. log η plot was about 0.7. The estimated value of s was similar to the value predicted by the percolation theory based on the superconductor–normal conductor mixture model. The critical exponent for the gel elasticity, t, as estimated from the slope of the log(?–?_g) vs. log G′ plot, where G′ was the dynamic shear modulus of the gel at a frequency of 2Hz. The value of t was about 2, which was also similar to the value predicted by the percolation theory. These results indicated the at the concentration dependences of η and G′ of polyacrylamide near the sol–gel transition point were described by the percolation theory.     

Sol‐gel synthesis and luminescent properties of red‐emitting Y(P,V)O4:Eu3+ phosphors

Eu³⁺‐activated Y(P,V)O₄ phosphors were prepared by the EDTA sol‐gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2–3 µm and had a smooth surface. The excitation spectra for Y(P,V)O₄:Eu³⁺ consisted of three strong excitation bands in the 200–350 nm range, which were attributed to a Eu³⁺‐ O^2? charge‐transfer band and ¹A₁?¹ T₁/¹ T₂ transitions in VO₄^3?. The as‐synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu^{3+ 5}D₀?⁷ F₂ electric dipole transition. With the increase in the V⁵⁺/P⁵⁺ ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO₄^3? → Eu³⁺ energy transfer. Copyright © 2015 John Wiley & Sons, Ltd.     

Physical and chemical properties of gelatin from the skin of cultured Amur sturgeon (Acipenser schrenckii)

To expand the usefulness of cultured Amur sturgeon, Acipenser schrenckii, its skin was used to explore the production of gelatin. After acetic acid pre‐treatment (0.05 m for 3 h), gelatin was extracted at temperatures of 50 or 70°C for 1 or 6 h. Gelatin yield ranged from 9.42 to 12.47% (wet weight basis) (P < 0.05). With increasing extraction time and temperature, the content of imino acids (proline + hydroxyproline), gel strength and L*‐value (lightness) decreased, while the a*‐value (redness) and b*‐value (yellowness) of gelatin gel increased (P < 0.05). Electrophoretic analysis revealed that α‐chains and β‐chains were predominant components in all extracted gelatins. Higher molecular weight proteins (γ‐chain) were also observed. Gelling and melting temperatures of gelatin were 13.6–14.6°C and 20.3–22.6°C, respectively. Circular dichroism (CD) spectra and Fourier transform infrared (FTIR) spectroscopy revealed the triple helix loss in gelatin (A₁₂₃₅ (AIII)/A₁₄₅₁ < 1). Extraction conditions caused secondary structure changes in the gelatin. More likely due to the differences in the culture water temperature, gelatin exhibited gelling and melting temperatures intermediate between those of cold‐ and warm‐water fish gelatins. The obtained gelatin can be used in food products or in the production of bioactive compounds.     

Slow relaxational processes in the melting of linear biopolymers: A theory and its application to nucleic acids

We treat the problem of the mean time of complete separation of complementary chains of a duplex containing N base pairs. A combination of analytical and computer methods is used to obtain the exact solution in the form of a compact expression. This expression is used to analyze the limits of application of the equilibrium theory of helix–coil transition in oligo- and polynucleotides. It also allows the melting behavior of a biopolymer to be predicted when its melting is nonequilibrium. In the case of oligonucleotides for which the equilibrium melting takes place at a high value of the stability constant s, the general expression turns into the equation of Craig, Crothers, and Doty, used by them to determine the rate constant k_f of the growth of a helical region from temperature-jump experiments. For the case of fragmented DNA with N ～ 10², the melting process is shown to be completely nonequilibrium, and as a result, the observed melting temperature should be higher than that for the equilibrium. A simple equation is obtained that makes possible calculation of the real, “kinetic” melting temperature T_k. As N increases, the observed melting temperature should approach the equilibrium value, T_m. This analysis has explained quantitatively the peculiar chain-length dependence of the experimentally observed shift in the DNA melting temperature during fragmentation. A thorough analysis is given of the nonequilibrium effects in the melting process of long DNA molecules (N ? 10³). The main conclusion is that even in the presence of profound hysteresis phenomena, the melting profile observed on heating may differ only slightly from the equilibrium profile.     

Synthesis,characterization and sol–gel entrapment of a crown ether‐styryl fluoroionophore

The synthesis and initial evaluation of a new dye‐functionalized crown‐ether, 2‐[2‐(2,3,5,6,8,9,11,12,14,15‐decahydro‐1,4,7,10,13,16‐benzohexaoxacyclooctadecin)ethenyl]‐3‐methyl benzothiazolium iodide (denoted BSD), are reported. This molecule contains a benzyl 18‐crown‐6 moiety as the ionophore and a benzothiazolium to spectrally transduce ion binding. Binding of K⁺ to BSD in methanol causes shifts in the both absorbance and fluorescence emission maxima, as well as changes in the molar absorptivity and the emission intensity. Apparent dissociation constants (K_d) in the range 30–65 µ m were measured. In water and neutral buffer, K_d values were approximately 1 m m . BSD was entrapped in sol–gel films composed of methyltriethoxysilane (MTES) and tetraethylorthosilicate (TEOS) with retention of its spectral properties and minimal leaching. K⁺ binding to BSD in sol–gel films immersed in pH 7.4 buffer causes significant fluorescence quenching, with an apparent response time of approximately 2 min and an apparent K_d of 1.5 m m . Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of additives on isothermal crystallization kinetics and physical characteristics of coconut oil

The effect of lauric acid and low-HLB sucrose esters (L-195, S170) on the isothermal crystallization of coconut oil was investigated by differential scanning calorimetry. The fundamental crystallization parameters, such as induction time of nucleation and crystallization rate, were obtained by using the Gompertz equation. The Gibb's free energy of nucleation was calculated via the Fisher–Turnbull equation based on the equilibrium melting temperature. All additives, investigated in this work, proved to have an inhibition effect on nucleation and crystallization kinetics of coconut oil. Our results revealed that the inhibition effect is related to the dissimilarity of the molecular characteristics between coconut oil and the additives. The equilibrium melting temperature (T_m°) of the coconut oil–additive mixtures estimated by the Hoffman–Weeks method was decreased with the addition of lauric acid and increased by using sucrose esters as additives. Micrographs showing simultaneous crystallization of coconut oil and lauric acid indicated that strong molecular interaction led to the increase in lamellar thickness resulting in the T_m° depression of coconut oil. The addition of L-195 modified the crystal morphology of coconut oil into large, dense, non-porous crystals without altering the polymorphic occurrence of coconut oil. The enhancement in lamellar thickness and crystal perfection supported the T_m° elevation of coconut oil.     

Steady-state and pulsed NMR studies of gelation in aqueous agarose

Steady-state and pulsed NMR techniques have been used to investigate molecular motion in sols and gels of agarose. In passing through the sol–gel transition, the molecular mobility of water molecules is reduced only by a small amount, whereas motion of the polymer chains is greatly attenuated. The results are discused in terms of the network theory of gelation, with references to the role of water in the process and the nature of the “junction zones” between polymer chains. T₂ and line-width measurements are dominated by exchange broadening. The effects of exchange rate and differences in relaxation time between the exchanging sites are discussed. The temperature hysteresis behavior of agarose gels has been investigated and the effects of “ageing” correlated with changes in nuclear relaxation times. The synergistic increase in gel strength obtained on adding locust bean gum (LBG) to agarose has been investigated. The results indicate that LBG does not form double-helix junctions and may decrease rates of gelation by steric effects. At high agarose concentration, the LBG remains mainly in solution in interstitial water, but at low agarose concentration, it is suggested that the LBG can link gel aggregates together into a self-supporting structure, producing a synergistic increase in gel strength. Comparisons have been made between the nature of the agarose–LBG interaction and agarose–cellulose interactions in biological systems.     

NMR study on molecular mobility of DNA molecules in solution

The molecular mobility of calf thymus DNA molecules in solution has been discussed in terms of correlation time τ calculated from measurements of longitudinal T₁ and transverse T₂ magnetic relaxation times. The influence of DNA concentration and ionic strength of the solution upon freedom of movement of DNA molecules was studied for native and denatured DNA and also during thermal helix-coil transition. The dependence of τ values on temperature was carried out by comparing the values of correlation times τ_tat given temperature with the correlation time τ₂₀ at 20°C. The molecular rotation of DNA at 20°C and at higher ionic strength at 0.15 and 1.0.M NaCl is described by τ values of the order of 1.0–1.2 × 10^?8 and was reduced slightly with increase of temperature below the helix-coil transition. The molecular rotation of DNA in 0.02MNaCl was lower at 20°C as compared to DNA in solvents with higher NaCl concentrations and increases rapidly with increase of temperature in the range 20–60°C. The values of correlation time are characterized by fast increase at temperatures above the spectrophotometrically determined beginning of melting curve. The beginning of this increase is observed at about 65, 80, and 85°C for DNA in 0.02, 0.15, and 1.0MNaCl, respectively. Values of correlation time for denatured DNA are in all cases about 1.1–1.4 times that for native DNA. The obtained results are discussed in terms of conformation of DNA molecules in solution as well as in terms of water dipole binding in DNA hydration shells.     

Sol–gel synthesis,characterization and luminescence properties of SrMgAl2SiO7:Eu2+ as a novel nanocrystalline phosphor

In this research, a new SrMgAl₂SiO₇:Eu²⁺ phosphor was synthesized via the sol–gel method. The phase‐forming processes were studied by thermogravimetric–differential thermal analysis and X‐ray diffraction technique. Scanning electron microscopy showed that there is uniform morphology and microstructure owing to the sol–gel route. Spectrophotometry and colorimetry analyses illustrated that, under short ultraviolet excitation, the main emission peak occurred at 421 nm and also a relatively pure blue color was observed that was ascribed to the 4f⁶5d¹(²D) → 4f⁷(⁸S_7/2) transition of Eu²⁺ with color coordination of x = 0.187, y = 0.077. Finally, it was found that the color and phase purity of the synthesized powder increased as calcinations time increased. Copyright © 2010 John Wiley & Sons, Ltd.     

A dilatometric investigation of the effects of general anaesthetics,alcohols and hydrostatic pressure on the phase transition in smectic mesophases of dipalmitoyl phosphatidylcholine

The effect of general anaesthetics, alcohols and hydrostatic pressure on the thermal transition in dipalmitoyl phosphatidylcholine multilayer liposomes has been measured using dilatometry. The volume increasse at the transition (ΔV_t) is 0.0350 ± 0.0003 ml/g. the transition temperature (T_t) 41.84 ± 0.09°C and the width of the transition 1.025 ± 0.18°C. ΔH calculated by the Clapeyron-Clausius equation is 8.4 kcal/mol. The n-alcohols C₃C₅ reduced the transition temperature without affecting the transition width which was however, increased by n-hexanol. Trichloroethylene, the fluorescent probe N-phenyl-1-naphthyl-amine, and methoxyflurane all increased the transition width (reduced the cooperativity of the transition) with a simultaneous depression of T_t. Methoxyflurane caused a two-stage transition expansion. Diethyl ether's effect has similarities with both the C₃ and C₆ alcohols. Generally ΔV_t was unaffected by the agents.Pressure increased T_t by 0.0238°C/atm linearly over the range 1–300 atm in both treated and untreated liposomes, and therefore cannot be said to antagonize anaesthetics. In both treated and untreated liposomes ΔV_t and the width of the transition were unaffected by pressure. Pressure thus reverses the effects of anaesthetics on T_t but not their spread of the transition width.     

Estimation of the diversity between DNA calorimetric profiles,differential melting curves and corresponding melting temperatures

The Poland–Fixman–Freire formalism was adapted for modeling of calorimetric DNA melting profiles, and applied to plasmid pBR 322 and long random sequences. We studied the influence of the difference (H_GC?H_AT) between the helix‐coil transition enthalpies of AT and GC base pairs on the calorimetric melting profile and on normalized calorimetric melting profile. A strong alteration of DNA calorimetrical profile with H_GC?H_AT was demonstrated. In contrast, there is a relatively slight change in the normalized profiles and in corresponding ordinary (optical) normalized differential melting curves (DMCs). For fixed H_GC?H_AT, the average relative deviation (S) between DMC and normalized calorimetric profile, and the difference between their melting temperatures (T_cal?T_m) are weakly dependent on peculiarities of the multipeak fine structure of DMCs. At the same time, both the deviation S and difference (T_cal?T_m) enlarge with the temperature melting range of the helix‐coil transition. It is shown that the local deviation between DMC and normalized calorimetric profile increases in regions of narrow peaks distant from the melting temperature.     

Melting, glass transition, and apparent heat capacity of α-d-glucose by thermal analysis

The thermal behaviors of α-d-glucose in the melting and glass transition regions were examined utilizing the calorimetric methods of standard differential scanning calorimetry (DSC), standard temperature-modulated differential scanning calorimetry (TMDSC), quasi-isothermal temperature-modulated differential scanning calorimetry (quasi-TMDSC), and thermogravimetric analysis (TGA). The quantitative thermal analyses of experimental data of crystalline and amorphous α-d-glucose were performed based on heat capacities. The total, apparent and reversing heat capacities, and phase transitions were evaluated on heating and cooling. The melting temperature (T_m) of a crystalline carbohydrate such as α-d-glucose, shows a heating rate dependence, with the melting peak shifted to lower temperature for a lower heating rate, and with superheating of around 25 K. The superheating of crystalline α-d-glucose is observed as shifting the melting peak for higher heating rates, above the equilibrium melting temperature due to of the slow melting process. The equilibrium melting temperature and heat of fusion of crystalline α-d-glucose were estimated. Changes of reversing heat capacity evaluated by TMDSC at glass transition (T_g) of amorphous and melting process at T_m of fully crystalline α-d-glucose are similar. In both, the amorphous and crystalline phases, the same origin of heat capacity changes, in the T_g and T_m area, are attributable to molecular rotational motion. Degradation occurs simultaneously with the melting process of the crystalline phase. The stability of crystalline α-d-glucose was examined by TGA and TMDSC in the melting region, with the degradation shown to be resulting from changes of mass with temperature and time. The experimental heat capacities of fully crystalline and amorphous α-d-glucose were analyzed in reference to the solid, vibrational, and liquid heat capacities, which were approximated based on the ATHAS scheme and Data Bank.     

1H NMR studies: dynamics of water in gelatin

 Proton magnetic resonance was used to characterize the dynamics of water in gelatin. Both sol and gel states were investigated. Transverse relaxation rates (R ₂) were dependent on the proton frequency measurement. (R ₂) measured with the Carr-Purcell-Meiboom-Gill pulse sequence was dependent on pulse spacing. These observations were interpreted in terms of chemical exchanges between water protons and those of the macromolecules in the sol state, whereas in the gel state the contribution of diffusion through microheterogeneities in the sample seems to provide an additional transverse relaxation mechanism. Received: 10 May 1999 / Revised version: 13 December 1999 / Accepted: 25 January 2000     

A study of DNA denaturation in the ultracentrifuge

The melting transition of DNA in alkaline CsCl can be followed in the analytical ultracentrifuge. Equilibrium partially denatured states can be observed. These partially denatured DNA bands have bandwidths of up to several times those of native DNA. Less stable molecules melt early and are found at heavier densities in the melting region. An idealized ultracentrifuge melting transition is described. The melting transition of singly nicked PM-2 DNA resembles the idealized curve. The DNA profile is a Gaussian band at all points in the melt. DNA's from mouse, D. Melanogaster, M. lysodeikticus, T4, and T7 also show equilibrium bands at partially denatured densities, some of which are highly asymmetric. Simple sequence satellite DNA shows an all-or-none transition with no equilibrium bands at partially denatured densities. The temperature at which a DNA denatures is an increasing function of the (G + C) content of the DNA. The T_m does not show a molecular-weight dependence in the range 1.2 × 10⁶–1.5 × 10⁷ daltons (single strand) for mouse, M. lysodeikticus, or T4 DNA. The mouse DNA partially denatured bands do not change shape as a function of molecular weight. The T4 DNA intermediate band develops a late-melting tail at low molecular weight. M. lysodeikticus DNA bands at partially denatured densities become broader as the molecular weight is decreased. Mouse DNA is resolved into six Gaussian components at each point in the melting transition.     

Water‐compatible silica sol–gel molecularly imprinted polymer as a potential delivery system for the controlled release of salicylic acid

Molecularly imprinted polymers (MIPs) for salicylic acid were synthesized and evaluated in aqueous environments in the aim to apply them as drug delivery carriers. One organic MIP and one inorganic MIP based on the sol–gel process were synthesized. The organic MIP was prepared by radical polymerization using the stoichiometric functional monomer, 1‐(4‐vinylphenyl)‐3‐(3,5‐bis(trifluoromethyl)phenyl)urea, which can establish strong electrostatic interactions with the –COOH of salicylic acid. The sol–gel MIP was prepared with 3‐(aminopropyl)triethoxysilane and trimethoxyphenylsilane, as functional monomers and tetraethyl orthosilicate as the crosslinker. While the organic MIPs bound the target specifically in acetonitrile, they exhibited lower binding in the presence of water, although the imprinting factor increased under these conditions, due to reduced non‐specific binding. The sol–gel MIP has a high specificity and capacity for the drug in ethanol, a solvent compatible with drug formulation and biomedical applications. In vitro release profiles of the polymers in water were evaluated, and the results were modelled by Fick's law of diffusion and the power law. Analysis shows that the release mechanism was predominantly diffusion‐controlled. Copyright © 2014 John Wiley & Sons, Ltd.     

Selecting polymers for two‐phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity,crystallinity, and glass transition temperature

Two‐phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (w_c), and (3) glass transition temperature (T_g). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n‐butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n‐butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their T_g, and that the T_g can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1500–1507, 2015     

Effect of inorganic salts and glucose additives on dose–response,melting point and mass density of genipin gel dosimeters

Genipin gel dosimeters are hydrogels infused with a radiation-sensitive material which yield dosimetric information in three dimensions (3D). The effect of inorganic salts and glucose on the visible absorption dose–response, melting points and mass density of genipin gel dosimeters has been experimentally evaluated using 6-MV LINAC photons. As a result, the addition of glucose with optimum concentration of 10% (w/w) was found to improve the thermal stability of the genipin gel and increase its melting point (T_m) by 6 °C accompanied by a slight decrease of dose–response. Furthermore, glucose helps to adjust the gel mass density to obtain the desired tissue-equivalent properties. A drop of T_m was observed when salts were used as additives. As the salt concentration increased, gel T_m decreased. The mass density and melting point of the genipin gel could be adjusted using different amounts of glucose that improved the genipin gel suitability for 3D dose measurements without introducing additional toxicity to the final gel.     

Effect of pressure on the sol-gel transition of carrageenans

The effects of pressure on the sol-gel transition of κ- and ι-carrageenans were studied in KCl solutions under high pressures up to 3000 kg/cm². The carrageenan gels were destabilized by pressure: the pressure depression of melting temperature, (dT/dP)_m, was ?5.7 × 10^?3 and ?4.0 × 10^?3 K cm²/kg independent of KCl concentration for κ- and ι-carrageenans, respectively. The enthalpy, entropy and volume changes accompanying the gel formation were calculated from the Eldridge-Ferry's plots and the Clausius-Clapeyron equation. The volume change per unit cross-link (two disaccharide residues) was estimated to be (2.5 ～ 4.9) and (1.7 ～ 3.4) ml/mol for κ- and ι-carrageenans, respectively. The compressibility of both carrageenan molecules appeared to be larger by (1.6 ～ 2.6) × 10^?12 (κ-form) and by (0.8 ～ 1.3) × 10^?12cm²/dyn (i-form) in gel state as compared with in sol state These increases in volume and compressibility on gelation were attributed to a reduction of water of hydration from the carrageenan molecules, which is mainly due to a replacement of the polymer-water hydrogen bond by the polymer-polymer hydrogen bond. These results seemed not inconsistent with the idea that a double helix structure of carrageenan gels may persist in solution as well as in the solid state.     

Effects of Polyols and Sugars on the Sol-Gel Transition of Gelatin

The melting temperature of gelatin gel increased with increasing concentrations of polyols and sugars added at any gelatin concentation. The enthalpy of gel melting measured by Eldridge-Ferry plots and calorimetric measurements was decreased by addition of these polyhydric compounds, indicating that the gel stabilization by them is predominantly due to the large decrease in entropy of gel melting. Circular dichroism analysis showed that the helix formation of gelatin molecules was enhanced with increasing concentrations of these additives, but there was no positive correlation between their helix-forming ability and gel-stabilizing ability. The viscosity of gelatin solution was less in these mixed solvents than in water. Based on these results, a possible stabilization mechanism of gelatin gel by polyhydric compounds was discussed, in comparison with that of native collagen, in terms of the thermodynamics of protein-solvent interactions.     

Glassy State and Seed Storage Stability: The WLF Kinetics of Seed Viability Loss at T>Tgand the Plasticization Effect of Water on Storage Stability

The relationship between the glassy state in seeds and storage stability was examined, using the glass transition curve and a seed viability database from previous experiments. Storage data for seeds at various water contents were studied by Williams–Landel–Ferry (WLF) kinetics, whereas the glass transition curves of seeds with different storage stability were analysed by the Gordon–Taylor equation in terms of the plasticization effect of water on seed storage stability. It was found that the critical temperatures (T_c) for long-term storage of three orthodox seeds were near or below their glass transition temperatures (T_g), indicating the requirement for the presence of the glassy state for long-term seed storage. The rate of seed viability loss was a function of T-T_gat T>T_g, which fitted the WLF equation well, suggesting that storage stability was associated with the glass transition, and that the effect of water content on seed storage was correlated with the plasticization effect of water on intracellular glasses. A preliminary examination suggested a possible link between the glass transition curve and seed storage stability. According to the determined WLF constants, intracellular glasses in seeds fell into the second class of amorphous systems as defined by Slade and Levine (Critical Reviews in Food Science and Nutrition30: 115–360, 1991). These results support the interpretation that the glassy state plays an important role in storage stability and should be a major consideration in optimizing storage conditions.