Effects of temperature on the properties of primary auditory fibres of the spectacled caiman,Caiman crocodilus (L.)

Summary The effect of temperature on the response properties of primary auditory fibres in caiman was studied. The head temperature was varied over the range of 10–35 ° C while the body was kept at a standard temperature of 27 °C (T_s). The temperature effects observed on auditory afferents were fully reversible. Below 11 °C the neural firing ceased.The mean spontaneous firing rate increased nearly linearly with temperature. The slopes in different fibres ranged from 0.2–3.5 imp s^–1 °C^–1. A bimodal distribution of mean spontaneous firing rate was found (<20 imp s^–1 and >20 imp s^–1 at T_s) at all temperatures.The frequency-intensity response area of the primary fibres shifted uniformly with temperature. The characteristic frequency (CF) increased nearly linearly with temperature. The slopes in different fibres ranged from 3–90 Hz °C^–1. Expressed in octaves the CF-change varied in each fibre from about O.14oct °C^–1 at 15 °C to about 0.06 oct °C^–1 at 30 °C, irrespective of the fibre's CF at T_s. Thresholds were lowest near T_s. Below T_s the thresholds decreased on average by 2dB°C^–1, above T_s the thresholds rose rapidly with temperature. The sharpness of tuning (Q_10db) showed no major change in the temperature range tested.Comparison of these findings with those from other lower vertebrates and from mammals shows that only mammalian auditory afferents do not shift their CF with temperature, suggesting that a fundamental difference in mammalian and submammalian tuning mechanisms exists. This does not necessarily imply that there is a single unifying tuning mechanism for all mammals and another one for non-mammals.Abbreviations BF best frequency: frequency of maximal response at an intensity 10 dB above the CF-threshold - CF characteristic frequency - FTC frequency threshold curve, tuning curve - T _s standard temperature of 27 °C     

Predict the glass transition temperature of glycerol-water binary cryoprotectant by molecular dynamic simulation

Vitrification is proposed to be the best way for the cryopreservation of organs. The glass transition temperature (T_g) of vitrification solutions is a critical parameter of fundamental importance for cryopreservation by vitrification. The instruments that can detect the thermodynamic, mechanical and dielectric changes of a substance may be used to determine the glass transition temperature. T_g is usually measured by using differential scanning calorimetry (DSC). In this study, the T_g of the glycerol-aqueous solution (60%, wt/%) was determined by isothermal-isobaric molecular dynamic simulation (NPT-MD). The software package Discover in Material Studio with the Polymer Consortium Force Field (PCFF) was used for the simulation. The state parameters of heat capacity at constant pressure (C_p), density (ρ), amorphous cell volume (V_cell) and specific volume (V_specific) and radial distribution function (rdf) were obtained by NPT-MD in the temperature range of 90–270 K. These parameters showed a discontinuity at a specific temperature in the plot of state parameter versus temperature. The temperature at the discontinuity is taken as the simulated T_g value for glycerol–water binary solution. The T_g values determined by simulation method were compared with the values in the literatures. The simulation values of T_g (160.06–167.51 K) agree well with the DSC results (163.60–167.10 K) and the DMA results (159.00 K). We drew the conclusion that molecular dynamic simulation (MDS) is a potential method for investigating the glass transition temperature (T_g) of glycerol–water binary cryoprotectants and may be used for other vitrification solutions.     

Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Ventilatory physiology of the numbat (<Emphasis Type="Italic">Myrmecobius fasciatus</Emphasis>)

This study examines the ventilatory physiology of the numbat (Myrmecobius fasciatus), a small to medium-sized (550 g) termitivorous marsupial. Ventilatory parameters at thermoneutrality reflect the slightly low (83% of predicted) basal metabolic rate of the numbat, with ventilation frequency (ƒ_R; 30.6±3.65 breaths min^–1), tidal volume [V_T; 6.0±0.66 ml at body temperature and pressure, saturated (BTPS)] and consequently minute volume (V_I; 117.7±15.22 ml min^–1; BTPS) all being 80–87% of that expected for a marsupial of similar body mass. Oxygen extraction was 27.7±1.37% in the thermoneutral zone. As is typical of marsupials, numbats accommodated increased oxygen consumption rates at ambient temperatures (T _a) below the thermoneutral zone by increasing minute volume (up to 411.2±43.98 ml min^–1; BTPS at T _a=10 °C) rather than oxygen extraction. Minute volume at 10 °C increased more by changes in ventilation frequency (up to 45.5±4.85 breaths min^–1) than tidal volume (9.4±1.03 ml, BTPS), as is also typical for a small-medium sized marsupial.Abbreviations BMR basal metabolic rate - BTPS body temperature and pressure, saturated - EO ₂ oxygen extraction - ƒ _R ventilation frequency - STPD standard temperature and pressure, dry - T _a ambient temperature - T _b body temperature - TNZ thermoneutral zone - V _I minute volume - V _T tidal volume - O ₂ oxygen consumption rate Communicated by I.D. Hume     

Glass transition temperatures of a ready to eat breakfast cereal formulation and its main components determined by DSC and DMTA

The effect of water content on the glass transition temperatures of a ready to eat cereal formulation was determined, as well as for its major components, oat flour, rice flour and an oat–rice flour blend, in the same ratio as they are present in the formulation. All samples were compression moulded at high temperature and were moisture conditioned in a 10–22% interval (dry basis). Glass transition temperatures (T_g) were measured by differential scanning calorimetry (DSC) and the main mechanical relaxation temperatures (T_α), measured by dynamic mechanical thermal analysis (DMTA). The relaxation temperatures taken at tan δ peaks, were found 20–30 °C larger than T_g. Besides the plasticizing effect of water adequately described by the Gordon–Taylor equation, no differences of T_g (and T_α) values between the major components were obtained at a constant moisture content. The T_g and T_α values of the RTE formulation were found to be about 30 °C lower than its components, a result which was attributed to the plasticizing effect of the minor components in the formulation (sugar and malt extract).     

Evidence of α fluctuations in myoglobin's denaturation in the high temperature region: Average relaxation time from an Adam–Gibbs perspective

In this work, we derive an analytical expression for the relaxation time τ as a function of temperature T for myoglobin protein (Mb, PDB:1MBN) in the high temperature limit (T > T_g = 200 K). The method is based on a modified version of the Adam–Gibbs theory (AG theory) for the glass transition in supercooled liquids and an implementation of differential geometry techniques. This modified version of the AG theory takes into account that the entropic component in protein's denaturation has two major sources: a configurational contribution ΔS_c due to the unfolding of the highly ordered native state N and a hydration contribution ΔS^hyd arising from the exposure of non-polar residues to direct contact with solvent polar molecules. Our results show that the configurational contribution ΔS_c is temperature-independent and one order of magnitude smaller than its hydration counterpart ΔS^hyd in the temperature range considered. The profile obtained for log τ(T) from T = 200 K to T = 300 K exhibits a non-Arrhenius behavior characteristic of α relaxation mechanisms in hydrated proteins and glassy systems. This result is in agreement with recent dielectric spectroscopy data obtained for hydrated myoglobin, where at least two fast relaxation processes in the high temperature limit have been observed. The connection between the relaxation process calculated here and the experimental results is outlined.     

Graphitized macroporous carbon microarray with hierarchical mesopores as host for the fabrication of electrochemical biosensor

A novel graphitized ordered macroporous carbon (GMC, pore size 380 nm) with hierarchical mesopores (2–30 nm) and high graphitization degree was prepared by nickel-catalyzed graphitization of polystyrene arrays. The obtained GMC possessed high specific surface area, large pore volume, and good electrical conductivity, which was explored for the enzyme entrapment and biosensor fabrication by a facile method. With advantages of novel nanostructure and good electrical conductivity, direct electrochemistry of hemoglobin (a model protein) was observed on the GMC-based biocomposite with a formal potential of −0.36 V (vs. Ag/AgCl) and an apparent heterogeneous electron transfer rate constant (k_s) of 1.2 s⁻¹ in pH 7.0 buffer. Comparative studies revealed that GMC offered significant advantages over carbon nanotubes (CNTs) in facilitating direct electron transfer of entrapped Hb. The fabricated biosensor exhibited good sensitivity (101.6 mA cm⁻² M⁻¹) and reproducibility, wide linear range (1–267 μM), low detection limit (0.1 μM), and good long-term stability for H₂O₂ detection. GMC proved to be a promising matrix for enzyme entrapment and biosensor fabrication, and may find wide potential applications in biomedical detection and environmental analyses.     

Coenzyme model reaction in lipid bilayers

Coenzyme model reactions, such as the H⁻ (H⁺ + 2e⁻) transfer from NADH models to triphenyl methane dyes, were investigated in the presence of lipid bilayers, for example, -α-dimyristoyl phosphatidyl choline and egg yolk lecithin. In the temperature dependence of the acceleration effect by the lipid bilayer, discontinuous points were observed, corresponding to the phase transition point such as gel-liquid crystal (T_c) or the segregation point (T_s). The T_c and T_s values of the bilayers varied with the reactant as a result of the difference of perturbing effect on the structure of the bilayers. The pressure effect on the transition point was also studied. Transition points such as T_c or T_s became higher with increasing pressure, and dT_c/dP or dT_s/dP was different for various bilayers. In the gel phase of the membrane, stereospecific reduction of malachite green was observed by chiral nicotinamide: the difference in the catalytic effect on the reduction rate between (R)- and (S)-dihydronicotinamides was larger in the gel phase than that in the liquid crystal phase or in the phase separated state, which suggests that the gel-state molecule can recognize the molecular structure better than the liquid-crystal state molecule.     

Fatty acid transport and activation and the expression patterns of genes involved in fatty acid trafficking

These studies defined the expression patterns of genes involved in fatty acid transport, activation and trafficking using quantitative PCR (qPCR) and established the kinetic constants of fatty acid transport in an effort to define whether vectorial acylation represents a common mechanism in different cell types (3T3-L1 fibroblasts and adipocytes, Caco-2 and HepG2 cells and three endothelial cell lines (b-END3, HAEC, and HMEC)). As expected, fatty acid transport protein (FATP)1 and long-chain acyl CoA synthetase (Acsl)1 were the predominant isoforms expressed in adipocytes consistent with their roles in the transport and activation of exogenous fatty acids destined for storage in the form of triglycerides. In cells involved in fatty acid processing including Caco-2 (intestinal-like) and HepG2 (liver-like), FATP2 was the predominant isoform. The patterns of Acsl expression were distinct between these two cell types with Acsl3 and Acsl5 being predominant in Caco-2 cells and Acsl4 in HepG2 cells. In the endothelial lines, FATP1 and FATP4 were the most highly expressed isoforms; the expression patterns for the different Acsl isoforms were highly variable between the different endothelial cell lines. The transport of the fluorescent long-chain fatty acid C₁-BODIPY-C₁₂ in 3T3-L1 fibroblasts and 3T3-L1 adipocytes followed typical Michaelis–Menten kinetics; the apparent efficiency (k_cat/K_T) of this process increases over 2-fold (2.1 × 10⁶–4.5 × 10⁶ s⁻¹ M⁻¹) upon adipocyte differentiation. The V_max values for fatty acid transport in Caco-2 and HepG2 cells were essentially the same, yet the efficiency was 55% higher in Caco-2 cells (2.3 × 10⁶ s⁻¹ M⁻¹ versus 1.5 × 10⁶ s⁻¹ M⁻¹). The kinetic parameters for fatty acid transport in three endothelial cell types demonstrated they were the least efficient cell types for this process giving V_max values that were nearly 4-fold lower than those defined form 3T3-L1 adipocytes, Caco-2 cells and HepG2 cells. The same cells had reduced efficiency for fatty acid transport (ranging from 0.82 × 10⁶ s⁻¹ M⁻¹ to 1.35 × 10⁶ s⁻¹ M⁻¹).     

Altitudinal change in soil and foliar nutrient concentrations and in microclimate across the tree line on the subtropical island mountain Mt. Teide (Canary Islands)

Mt. Teide (Tenerife, Spain) is a high volcanic island mountain with an unusually low tree line elevation (2000–2100 m). While searching for the causes of this tree line depression, we analysed the concentrations of total N, available P, and salt-exchangeable Ca, K and Mg in three soil horizons, and the foliar N, P, Ca, K and Mg concentrations in six abundant plant species (trees, shrubs, forbs) along a transect from 1400 (1600) to 3100 m a.s.l. The objective of the study was to detect altitudinal trends in soil and plant nutrient status below and above the tree line. For characterising elevational changes in microclimate and hydrology, we also conducted measurements of air and soil temperatures (T_a and T_s), atmospheric water vapour saturation deficit (D), potential evaporation (E) and soil moisture (θ) on 3–4 occasions along the transect.T_a and T_s did not linearly decrease with elevation but were highest at or immediately below the tree line and were relatively low in the closed Pinus canariensis forest at 1600 m. T_s reached maxima at about 70 °C near the tree line. The absence of a linear temperature decrease with elevation was caused by a stable temperature inversion at about 2000 m and by canopy shading in the forest canopy below the tree line. In June, the topsoil (10 cm) dried out almost completely between 1800 and 3100 m, but remained moist in the pine forest at 1600 m. This gradient reflects the transition from the montane cloud belt to the dry alpine belt higher upslope. The subsoil (30 cm) contained >30 vol% of soil water at all elevations even in June except for the uppermost site (3100 m). Potential evaporation increased with elevation despite a decrease in D. We assume that this is mainly due to the air pressure-dependent increase with elevation in the diffusion coefficient for water vapour in air.The concentrations of N and ‘available’ P (after Olsen) in the mineral topsoil were by far smaller than in alpine soils of other humid mountains which is thought to be a consequence of a very dry and biologically inactive topsoil in the semi-arid alpine belt of Mt. Teide. In contrast to many other mountains, foliar N, P and cation concentrations in the plants did not increase with elevation but either remained unchanged, or decreased as in the tree line species P. canariensis. Nevertheless, P. canariensis probably is not limited by nutrient deficiency at the tree line despite rather low N and P needle concentrations. Rather, drought and heat stress effects on seedling establishment are thought to be the causes of the tree line depression.     

α-Synuclein aggregation variable temperature and variable pH kinetic data: A re-analysis using the Finke–Watzky 2-step model of nucleation and autocatalytic growth

The aggregation of proteins is believed to be intimately connected to many neurodegenerative disorders. We recently reported an “Ockham's razor”/minimalistic approach to analyze the kinetic data of protein aggregation using the Finke–Watzky (F–W) 2-step model of nucleation (A → B, rate constant k₁) and autocatalytic growth (A + B → 2B, rate constant k₂). With that kinetic model we have analyzed 41 representative protein aggregation data sets in two recent publications, including amyloid β, α-synuclein, polyglutamine, and prion proteins (Morris, A. M., et al. (2008) Biochemistry 47, 2413-2427; Watzky, M. A., et al. (2008) Biochemistry 47, 10790–10800). Herein we use the F–W model to reanalyze protein aggregation kinetic data obtained under the experimental conditions of variable temperature or pH 2.0 to 8.5. We provide the average nucleation (k₁) and growth (k₂) rate constants and correlations with variable temperature or varying pH for the protein α-synuclein. From the variable temperature data, activation parameters ΔG^‡, ΔH^‡, and ΔS^‡ are provided for nucleation and growth, and those values are compared to the available parameters reported in the previous literature determined using an empirical method. Our activation parameters suggest that nucleation and growth are energetically similar for α-synuclein aggregation (ΔG^‡_nucleation = 23(3) kcal/mol; ΔG^‡_growth = 22(1) kcal/mol at 37 °C). From the variable pH data, the F–W analyses show a maximal k₁ value at pH ~ 3, as well as minimal k₁ near the isoelectric point (pI) of α-synuclein. Since solubility and net charge are minimized at the pI, either or both of these factors may be important in determining the kinetics of the nucleation step. On the other hand, the k₂ values increase with decreasing pH (i.e., do not appear to have a minimum or maximum near the pI) which, when combined with the k₁ vs. pH (and pI) data, suggest that solubility and charge are less important factors for growth, and that charge is important in the k₁, nucleation step of α-synuclein. The chemically well-defined nucleation (k₁) rate constants obtained from the F–W analysis are, as expected, different than the 1/lag-time empirical constants previously obtained. However, k₂ × [A]₀ (where k₂ is the rate constant for autocatalytic growth and [A]₀ is the initial protein concentration) is related to the empirical constant, k_app obtained previously. Overall, the average nucleation and average growth rate constants for α-synuclein aggregation as a function of pH and variable temperature have been quantitated. Those values support the previously suggested formation of a partially folded intermediate that promotes aggregation under high temperature or acidic conditions.     

ICChI, a glycosylated chitinase from the latex of Ipomoea carnea

A multi-functional enzyme ICChI with chitinase/lysozyme/exochitinase activity from the latex of Ipomoea carnea subsp. fistulosa was purified to homogeneity using ammonium sulphate precipitation, hydrophobic interaction and size exclusion chromatography. The enzyme is glycosylated (14–15%), has a molecular mass of 34.94 kDa (MALDI–TOF) and an isoelectric point of pH 5.3. The enzyme is stable in pH range 5.0–9.0, 80 °C and the optimal activity is observed at pH 6.0 and 60 °C. Using p-nitrophenyl-N-acetyl-β-d-glucosaminide, the kinetic parameters K_m, V_max, K_cat and specificity constant of the enzyme were calculated as 0.5 mM, 2.5 × 10⁻⁸ mol min⁻¹ μg enzyme⁻¹, 29.0 s⁻¹ and 58.0 mM⁻¹ s⁻¹ respectively. The extinction coefficient was estimated as 20.56 M⁻¹ cm⁻¹. The protein contains eight tryptophan, 20 tyrosine and six cysteine residues forming three disulfide bridges. The polyclonal antibodies raised and immunodiffusion suggests that the antigenic determinants of ICChI are unique. The first fifteen N-terminal residues G–E–I–A–I–Y–W–G–Q–N–G–G–E–G–S exhibited considerable similarity to other known chitinases. Owing to these unique properties the reported enzyme would find applications in agricultural, pharmaceutical, biomedical and biotechnological fields.     

Effects of temperature, salinity and irradiance on the growth of the red tide dinoflagellate Gyrodinium instriatum Freudenthal et Lee

The effects of temperature, salinity and irradiance on the growth of the red tide dinoflagellate Gyrodinium instriatum Freudenthal et Lee were examined in the laboratory. Exposed to 45 different combinations of temperature (10–30 °C) and salinity (0–40) under saturating irradiance, G. instriatum exhibited its maximum growth rate of 0.7 divisions/day at a combination of 25 °C and a salinity of 30. Optimum growth rates (>0.5 divisions/day) were observed at temperatures ranging from 20 to 30 °C and at salinities from 10 to 35. The organism could not grow at ≤10 °C. In addition, G. instriatum burst at a salinity of 0 at all temperatures, but grew at a salinity of 5 at temperatures between 20 and 25 °C. It is noteworthy that G. instriatum is a euryhaline organism that can live under extremely low salinity. Factorial analysis revealed that the contributions of temperature and salinity to its growth of the organism were almost equal. The irradiance at the light compensation point (I₀) was 10.6 μmol/(m² s) and the saturated irradiance for growth (I_s) was 70 μmol/(m² s), which was lower than I_s for several other harmful dinoflagellates (90–110 μmol/(m² s)).     

Structural modifications and thermal transitions of standard maize starch after DIC hydrothermal treatment

Standard maize starch was hydrothermally treated by Instantaneous Controlled Pressure Drop (DIC) process at three pressure levels (1, 2 and 3 bar) corresponding to the temperatures of 100, 122 and 135 °C (at 13–27% moisture), respectively. The structural effects of various hydrothermal conditions were examined with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. In order to understand the changes that occur during DIC treatment, melting endotherms of native maize starch at various moisture contents were determined. The gelatinization temperatures of DIC treated standard maize starch increased with DIC treatment. The transition temperatures (T_o, T_p) are closely related to the combined effect of pressure and processing time. At approximately 10 min of processing time, T_o and T_p were 65.7 and 72.3, 68.8 and 73.6 °C, 74.8 and 79.8 °C for pressure levels of 1, 2 and 3 bar, respectively (against 63.1 and 69.6 °C for native starch). DIC treatment narrowed the gelatinization temperature range and decreased gelatinization enthalpy (ΔH), as the severity of processing conditions increased. ΔH decreased from 11.4 J g⁻¹ (native) to 11.0 (1 bar), 9.0 (2 bar) and 1.7 J g⁻¹ (3 bar) for treated maize starch during approximately 10 min. Relative crystallinity of hydrothermally treated starch decreased with increasing DIC conditions. The A-type crystalline pattern was progressively lost (at pressure level 2 bar) and substituted by the V_h-type X-ray diffraction pattern, corresponding to the formation of amylose–lipid complexes. For severe DIC conditions (pressure level of 3 bar), the substitution was completed. Microscopic observations revealed progressive loss of the birefringence of DIC treated starch granules except at low pressure (1 bar), while the integrity of starch granules was preserved for all the conditions. These modifications that reveal important changes in the crystalline organization of the starch granules are related to their functional properties.     

Behaviour of water bound in bone marrow cells affected by organic solvents of different polarity

The behaviour of intracellular water affected by organic solvents of different polarity in partially dehydrated marrow cells obtained from tubular bones of broiler chickens was studied using ¹H NMR spectroscopy at 210–290 K. The ¹H NMR spectra of intracellular water include two signals which can be assigned to strongly (SAW, chemical shift of the proton resonance δ_H = 4–5 ppm) and weakly (WAW, δ_H = 1.2–1.7 ppm) associated waters which can be also divided into weakly (WBW, frozen at 250 < T < 273 K and changes in the Gibbs free energy ΔG > −0.8 kJ/mol) and strongly (SBW, unfrozen at T < 250 K, ΔG < −0.8 kJ/mol) bound intracellular waters. Solvents of different polarity such as dimethylsulfoxide-d₆ (Me₂SO-d₆), acetonitrile-d₃, and chloroform-d differently affect structure, Gibbs free energy, and molecular mobility of intracellular water. A maximal fraction of SBW in WAW and a minimal fraction of SBW in SAW are observed on absorption of acetonitrile (0.8 g/g) by cells. The opposite results are on addition of Me₂SO (0.8 g/g) which strongly changes organisation of intracellular water and enhances the freezing point depression of SBW.     

The routine metabolic rate of mulloway (Argyrosomus japonicus: Sciaenidae) and yellowtail kingfish (Seriola lalandi: Carangidae) acclimated to six different temperatures

This study compared the mass-specific routine metabolic rate (RMR) of similar sized mulloway (Argyrosomus japonicus), a sedentary species, and yellowtail kingfish (Seriola lalandi), a highly active species, acclimated at one of several temperatures ranging from 10–35 °C. Respirometry was carried out in an open-top static system and RMR corrected for seawater–atmosphere O₂ exchange using mass-balance equations. For both species RMR increased linearly with increasing temperature (T). RMR for mulloway was 5.78T − 29.0 mg O₂ kg^− 0.8 h^− 1 and for yellowtail kingfish was 12.11T − 39.40 mg O₂ kg^− 0.8 h^− 1. The factorial difference in RMR between mulloway and yellowtail kingfish ranged from 2.8 to 2.2 depending on temperature. The energetic cost of routine activity can be described as a function of temperature for mulloway as 1.93T − 9.68 kJ kg^− 0.8 day^− 1 and for yellowtail kingfish as 4.04T − 13.14 kJ kg^− 0.8 day^− 1. Over the full range of temperatures tested Q₁₀ values were approximately 2 for both species while Q₁₀ responses at each temperature increment varied considerably with mulloway and yellowtail kingfish displaying thermosensitivities indicative of each species respective niche habitat. RMR for mulloway was least thermally dependent at 28.5 °C and for yellowtail kingfish at 22.8 °C. Activation energies (E_a) calculated from Arrhenius plots were not significantly different between mulloway (47.6 kJ mol^− 1) and yellowtail kingfish (44.1 kJ mol^− 1).     

Diversity in amylopectin structure, thermal and pasting properties of starches from wheat varieties/lines

Structural, thermal and pasting diversity of starches from Indian and exotic lines of wheat was studied. Majority of the starches showed amylose content ranging between 22% and 28%. Endotherm temperatures (T_o, T_p and T_c) of the starches showed a range between 56–57, 60 –61 and 65.5–66.5 °C, respectively. Exotherms with T_p between 87.0 and 88.2 °C were observed during cooling of heated starches, indicating the presence of amylose–lipid complexes. Exotherm temperatures were negatively correlated to swelling power. Amylopectin unit chains with different degree of polymerization (DP) were observed to be associated with pasting temperature, setback and thermal (endothermic T_o, T_p, and T_c) parameters. Amylopectin unit chains of DP 13–24 showed positive relationship with endothermic T_o, T_p and T_c. Pasting temperature showed positive correlation with short chains (DP 6–12) while negative correlation with medium chain (DP 13–24) amylopectins. Setback was positively correlated to DP 16–18 and negatively to DSC amylose–lipid parameters.     

Model for the production of L-tryptophan from L-serine and indole by immobilized cells in a three-phase liquid-impelled loop reactor

Production of L-tryptophan from L-serine and indole catalyzed by Escherichia coli, immobilized in k-carrageenan gel beads, is technically feasible in the liquidimpelled loop reactor (LLR), using an organic solvent, e.g. n-dodecane.With L-serine in large excess intrinsic reaction kinetics is approximately first order with respect to indole, with a reaction constant of 8.5×10^–5 m³ kg _dw ^–1 s^–1.The overall process kinetics is jointly controlled by intrinsic kinetics and by intraparticle mass transfer resistance, which can be quantified using an effectiveness factor.Mass transfer of indole from the organic to the aqueous phase and from the aqueous to the gel phase are relatively fast and thus have negligible influence in the overall process kinetics, under the operational conditions tested. However, they may become important if the process is intensified by increasing the cell concentration in the gel and/or the gel hold-up in the reactor.A simple model which includes indole mass balances over the aqueous and organic phases, mass transfer and reaction kinetics, with parameters experimentally determined in independent experiments, was successful in simulating L-tryptophan production in the LLR.List of Symbols a, b, c coefficients of the equilibrium curve for indole between organic and aqueous phases - A, B, C, D, E, F auxiliary variables used in liquid-liquid mass transfer studies - a _x specific interfacial area referred to the volume of the aqueous phase (m^–1) - A _x interfacial area (m²) - a _Y specific interfacial area referred to the volume of the organic phase (m^–1) - A _Y interfacial area (m²) - C _b substrate concentration in the bulk of the aqueous phase (kg m^–3) - C _e substrate concentration in exit stream (kg m^–3) - C _E biocatalyst concentration referred to the aqueous phase (kg m^–3) - C _{E s} biocatalyst concentration referred to the volume of gel (kg m^–3) - C _s substrate concentration at the gel surface (kgm^–3) - d, e, f coefficients of the equilibrium curve for indole between aqueous and organic phases - dp particle diameter (m) - K ₂ kinetic constant (s^–1) - K ₁ kinetic constant K₂/K_M (kg^–1 m³ s^–1) - K _M Michaälis-Menten constant (kgm^–3) - K _X mass transfer coefficient referred to the aqueous phase (ms^–1) - K _Xa_X volumetric mass transfer coefficient based on the volume of the aqueous phase (s^–1) - k _Y mass transfer coefficient referred to the organic phase (ms^–1) - K _Ya_Y volumetric mass transfer coefficient based on the volume of the organic phase (s^–1) - N _X mass flux of indole from organic to aqueous Phase (kg m^–2s^–1) - N _Y mass flux of indole from aqueous to organic phase (kg m^–2s^–1) - Q _e volumetric flow rate in exit stream (m³s^–1) - Q _f volumetric flow rate in feed stream (m³s^–1) - _obs observed reaction rate (kg s^–1 m^–3) - intrinsic reaction rate (kg s^–1 m^–3) - Re Reynolds number - Sc Schmidt number - Sh Sherwood number - t time (s) - u superficial velocity (m s^–1) - V _max maximum reaction rate (kg s^–1m^–3) - V _S volume of the support (m³) - V _X volume of aqueous phase (m³) - V _Y volume of the organic phase (m³) - X indole concentration in the aqueous phase (kgm^–3) - Y indole concentration in the organic phase (kg m^–3 Greek Letters overall effectiveness factor - _e external effectiveness factor - _i internal effectiveness factor - Thiele module A fellowship awarded to one of us (D.M.R.)by INICT is gratefuly acknowledged.     

Stimuli-responsive separation of proteins using immobilized liposome chromatography

The possibility of the stimuli-responsive separation of proteins was investigated using immobilized liposome chromatography (ILC) as novel aqueous two-phase systems. The specific capacity factor (k_s) of β-galactosidase, obtained by analysis of ILC, was varied by changing the pH of the solution and was maximized at the specific pH of 5 (k_s,max=5.57). The k_s values were found to correspond well with their local hydrophobicities, which can be determined by the aqueous two-phase partitioning method. The variation of k_s, therefore, indicates a change in the surface properties of a protein during conformational change under pH stimuli. A similar phenomenon is observed in the case of other proteins (α-glucosidase, k_s,max=11.3 at pH 4; carbonic anhydrase from bovine, k_s,max=6.53 at pH 4). The difference in the height and/or the position of the peaks of the k_s–pH curves of each protein suggests a difference in their pH denaturation in the ILC column. Based on these results, the mutual separation of the above proteins at pH 4 could be successfully performed by selecting their specific capacity factor as a design parameter.     

Functional expression of N-terminal truncated α-subunits of Na,K-ATPase in Xenopus laevis oocytes

N-terminal deletion mutants of Na,K-ATPase α₁ isoforms initiating translation at Met³⁴ (α₁T₁) or at Met⁴³ (α₁T₂) were expressed in X. laevis oocytes. Compared to β₃ cRNA injected controls, the co-expression of α₁wt, α₁T₁, α₁T₂ with β₃ subunits results in a 2- to 3-fold increase of ouabain binding sites, parallelled by a concomitant increase in Na,K-pump current. The apparent K for potassium activation of the α₁T₂/β₃ Na,K-pumps is significantly higher than that of the α₁wt/β₃ or α₁T₁/β₃ Na,K-pumps expressed at the cell surface. Total deletion of the lysine-rich N-terminal domain thus allows the expression of active Na,K-pump but with distinct cation transport properties.