Heat-induced Change Research Articles

Heat- and light-treatment change the visible fluorescence of Akoya cultured pearls

We exposed Akoya cultured pearls separately to heat (60–120 °C) and artificial light to investigate changes to fluorescence in the visible range and yellowing. We found that for both heat-treated and light-treated pearls, the fluorescence peak shifted from 480 to 430 nm with an increase in fluorescence intensity. This change in intensity was more prominent in heat-treated pearls, with the initial speed of increase rising with treatment temperature; treatment at 100 °C caused the greatest increase in fluorescence intensity. However, aminoguanidine suppressed the heat-induced change in the fluorescence of an ethylenediaminetetraacetic acid–soluble nacreous layer matrix. These results suggest that the heated-induced changes in the fluorescence of Akoya cultured pearls were caused largely by a buildup of fluorescent advanced glycation end products through the Maillard reaction. Although heat treatment led to a large increase in fluorescence intensity of the peak at approximately 430 nm in a deoxygenized environment, hardly any change in fluorescence intensity was observed after light treatment in this environment. Moreover, a new shoulder peak appeared at about 460 nm after light treatment. These results suggest that the Maillard reaction was not a major factor in the light-induced changes in the fluorescence of Akoya cultured pearls.

The Heat-Induced Reversible Change in the Blood-Testis Barrier (BTB) Is Regulated by the Androgen Receptor (AR) via the Partitioning-Defective Protein (Par) Polarity Complex in the Mouse1

Scrotal hypothermia is essential for normal spermatogenesis, and temporal heat stress causes a reversible disruption of the blood-testis barrier (BTB). Previous studies have shown that AR expression in primary monkey Sertoli cells (SCs) was dramatically reduced after temporary heat treatment. However, the mechanisms underlying the heat-induced reversible disruption of the BTB, including whether it is directly regulated by the AR, remain largely unknown. In this study, we demonstrated that the AR acts upstream to regulate the heat-induced reversible change in the BTB in mice. When the AR was overexpressed in SCs using an adenovirus, the heat stress-induced down-regulation of BTB-associated proteins (Zonula occludens-1 (ZO-1), N-Cadherin, E-Cadherin, α-Catenin, and β-Catenin) was partially rescued. AR knockdown by RNAi or treatment with flutamide (an AR antagonist) in SCs inhibited the recovery of BTB-associated protein expression after 43°C heat treatment for 30 min. The results of an in vivo AR antagonist injection experiment further showed that the recovery of BTB permeability induced by temporal heat stress was regulated by the AR. Furthermore, we observed that the co-localization and interactions of partitioning-defective protein (Par) 6-Par3-aPKC-Cdc42 polarity complex components were disrupted in both AR-knockdown and heat-induced SCs. AR overexpression in SCs prevented the disruption of these protein-protein interactions after heat treatment. AR knockdown or treatment with flutamide in SCs inhibited the restoration of these protein-protein interactions after heat treatment compared with heat treatment alone. Together, these results demonstrate that the AR plays a crucial role in the heat-induced reversible change in BTB via the Par polarity complex.

Gold Nanorods Embedded in Titanium Oxide Film for Sensing Applications

We succeeded in fabricating a localized surface plasmon resonance (LSPR) sensor comprising gold nanorods (AuNRs) that were immobilized in a thin film of titanium oxide. First, AuNRs were electrostatically immobilized onto a glass substrate; then, dip-coating of the thin titanium oxide film was carried out. These procedures were realized to prepare well-dispersed AuNRs onto a substrate with a uniform titanium oxide layer. The titanium-oxide-coated AuNRs could retain their rod-shape, even after annealing at 300°C for 1 h, since titanium oxide effectively prevented any heat-induced shape change of the AuNRs. The peak shifts of the plasmon bands of the immobilized AuNRs were observed with the change in the environmental refractive indices, even after titanium oxide coating. In addition, the as-prepared titanium oxide layer exhibited photocatalytic activity for methylene blue dye molecule under UV irradiation. This suggests that the titanium-oxide-coated AuNRs can conveniently be reusable even for unwanted contamination with organic compounds, due to their photocatalytic decomposition with UV light.

A new statistical approach for determining the crystallinity of heat-altered bone mineral from FTIR spectra

The crystallinity of bone mineral represents an established method of measuring heat-induced change and is of importance to fields including material science, clinical science, anthropology and archaeology. A commonly used technique involves the calculation of the Crystallinity Index (CI) using selected peaks from Fourier Transform Infrared (FTIR) absorbance spectra. However, the choice of peaks has to date not been statistically justified. In this study a novel application of statistical techniques to the FTIR spectra of bone samples burned in the range 100 °C–1100 °C has been used to identify 5 new spectral indices of heat-induced crystallinity change. The validity of the new indices was tested by using a statistical classification model (LDA) to predict the burning temperature of a set of 108 bone samples burned between 100 °C and 1100 °C. A correct classification rate (CCR) of 97.2% was obtained when a combination of 4 indices including the CI was used. This was significantly better than the CCR of 66.7% which was obtained when the CI was used on its own.

Characterizing the binding of nucleotide ATP on serum albumin by 31P NMR diffusion

The pulsed-field-gradient (PFG) 31P NMR diffusion spectra were measured under varied sample conditions to characterize the low-affinity binding of adenosine 5′-triphosphate (ATP) on human serum albumin (HSA) or bovine serum albumin (BSA). The NMR diffusion constants of ATP, ATP–HSA, or ATP–BSA were illustrated as function of ATP concentrations. The binding curves of ATP–HSA and ATP–BSA were identical but strikingly different from the ATP curve. Using a “Scatchard plot”, the apparent binding constant (K) and number of ATP binding sites (n) on serum albumin were evaluated as K = 75.25 (mol/L)–1 and n = 10, respectively. At a pH < 5.0 and a pH > 9.0 or a temperature > 45 °C, the diffusion data of ATP–HSA were found to increase remarkably, suggesting that the dissociation of ATP from HSA was largely enhanced, probably because of pH- or heat-induced protein structural change, degradation, or aggregation. In addition, our data indicated that ADP was strongly competitive with ATP for the low-affinity binding to HSA, but heptanone and Cl– were essentially noncompetitive. These results are important for further elucidating the interaction of ATP with serum albumin and its possible effect on related bioprocesses. The method can be well applied to study the binding of other nucleotides/nucleosides on proteins.

Improvement of Crystallization Rate in Post-Annealed Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> Films

Crystallization behaviors of dc sputtered Ge2Sb2Te5 films were studied by X-ray diffraction and transient optical transmittance. Crystalline peak at 29.0° in diffraction patterns appeared after thermal annealing at 180 and 210 °C. Crystallization rate increased after thermal annealing below crystallization temperature. These observations indicate that heat-induced structural change enhances crystallization rate of Ge2Sb2Te5films.

Effect of Annealing on Sub-Gap Absorption in Amorphous InGaZnO<sub>4</sub> Films

Optical absorption in amorphous InGaZnO4films was examined by optical transmittance and photothermal spectroscopy using individual cantilever. The amorphous InGaZnO4films have optical bandgap of ~3.5 eV, and Urbach tail absorption and mid-gap absorption at 2.0-3.0 eV. Mid-gap absorption was reduced by thermal annealing at 300 °C in an atmosphere. This observation indicates that heat-induced structural change causes reduction of gap states in amorphous InGaZnO4films.

Effect of hydrophilic polymer conjugation on heat-induced conformational changes in a protein

End-functional 2-methacryloyloxyethyl phosphorylcholine (MPC) co-polymers containing two different monomer units, 2-hydroxyethyl methacrylate (HEMA) and n-butyl methacrylate (BMA), with varying hydrophilicities were synthesized to investigate the effect of the conjugated hydrophilic polymer on the heat-induced conformational changes of a protein. MPC co-polymer-conjugated proteins containing the HEMA unit (PMH) could withstand thermal conformational changes better than those containing the more hydrophobic BMA unit (PMB). The changes in protein tertiary structures were estimated via the excitation of tryptophan. PMH-conjugated proteins could withstand heat-induced intensity changes better than the PMB-conjugated proteins. Thus, hydrophilic units in the conjugated polymer are probably essential in suppressing the heat-induced conformational changes of a protein. The changes in secondary and tertiary structures of poly(MPC)-(PMPC) and poly(HEMA) (PHEMA)-conjugated proteins were compared to validate the effect of MPC units on heat-induced conformational change. Although the thermally induced conformational changes in the secondary and tertiary structures of PHEMA-conjugated proteins were partially suppressed, the effect on PMPC-conjugated proteins was much greater, with significant conformational preservation. This is due to the specific hydration state of the hydrophilic PMPC chain, which reduces interaction between the protein molecules.

Moderate heat stress of Arabidopsis thaliana leaves causes chloroplast swelling and plastoglobule formation

Photosynthesis is inhibited by heat stress. This inhibition is rapidly reversible when heat stress is moderate but irreversible at higher temperature. Absorbance changes can be used to detect a variety of biophysical parameters in intact leaves. We found that moderate heat stress caused a large reduction of the apparent absorbance of green light in light-adapted, intact Arabidopsis thaliana leaves. Three mechanisms that can affect green light absorbance of leaves, namely, zeaxanthin accumulation (absorbance peak at 505 nm), the electrochromic shift (ECS) of carotenoid absorption spectra (peak at 518 nm), and light scattering (peak at 535 nm) were investigated. The change of green light absorbance caused by heat treatment was not caused by changes of zeaxanthin content nor by the ECS. The formation of non-photochemical quenching (NPQ), chloroplast movements, and chloroplast swelling and shrinkage can all affect light scattering inside leaves. The formation of NPQ under high temperature was not well correlated with the heat-induced absorbance change, and light microscopy revealed no appreciable changes of chloroplast location because of heat treatment. Transmission electron microscopy results showed swollen chloroplasts and increased number of plastoglobules in heat-treated leaves, indicating that the structural changes of chloroplasts and thylakoids are significant results of moderate heat stress and may explain the reduced apparent absorbance of green light under moderately high temperature.

Metabolic and hormonal acclimation to heat stress in domesticated ruminants

Environmentally induced periods of heat stress decrease productivity with devastating economic consequences to global animal agriculture. Heat stress can be defined as a physiological condition when the core body temperature of a given species exceeds its range specified for normal activity, which results from a total heat load (internal production and environment) exceeding the capacity for heat dissipation and this prompts physiological and behavioral responses to reduce the strain. The ability of ruminants to regulate body temperature is species- and breed-dependent. Dairy breeds are typically more sensitive to heat stress than meat breeds, and higher-producing animals are more susceptible to heat stress because they generate more metabolic heat. During heat stress, ruminants, like other homeothermic animals, increase avenues of heat loss and reduce heat production in an attempt to maintain euthermia. The immediate responses to heat load are increased respiration rates, decreased feed intake and increased water intake. Acclimatization is a process by which animals adapt to environmental conditions and engage behavioral, hormonal and metabolic changes that are characteristics of either acclimatory homeostasis or homeorhetic mechanisms used by the animals to survive in a new ‘physiological state’. For example, alterations in the hormonal profile are mainly characterized by a decline and increase in anabolic and catabolic hormones, respectively. The response to heat load and the heat-induced change in homeorhetic modifiers alters post-absorptive energy, lipid and protein metabolism, impairs liver function, causes oxidative stress, jeopardizes the immune response and decreases reproductive performance. These physiological modifications alter nutrient partitioning and may prevent heat-stressed lactating cows from recruiting glucose-sparing mechanisms (despite the reduced nutrient intake). This might explain, in large part, why decreased feed intake only accounts for a minor portion of the reduced milk yield from environmentally induced hyperthermic cows. How these metabolic changes are initiated and regulated is not known. It also remains unclear how these changes differ between short-term v. long-term heat acclimation to impact animal productivity and well-being. A better understanding of the adaptations enlisted by ruminants during heat stress is necessary to enhance the likelihood of developing strategies to simultaneously improve heat tolerance and increase productivity.

Temperature scanning FTIR analysis of secondary structures of proteins embedded in amorphous sugar matrix

Heat-induced changes in secondary structures of five proteins (bovine serum albumin, BSA; human serum albumin, HSA; myoglobin; ribonuclease A, RNase A; and, β-lactoglobulin, β-Lg) in an amorphous sugar matrix were analyzed by temperature-scanning Fourier transform infrared spectroscopy to elucidate the mechanism of heat-induced conformational change of solid-phase proteins. Three sugars, trehalose, maltose, and dextran (MW 6000), were used. Loss of α-helices due to increasing temperature was observed for BSA, HSA, and myoglobin, which are rich in α-helices. RNase A showed a marked decrease in predominant secondary structural components (β-sheet) with increasing temperature. However, no noticeable changes in the content of secondary structures, except for a slight loss of α-helices, were observed for β-Lg, which is also β-sheet-rich. These heat-induced conformational changes were significant at temperatures above the glass transition temperature. The heat-induced conformational change in BSA dried with sugar appeared time-independent and was clearly different from that due to dehydration and from the thermal conformational change for a solution of BSA. In particular, differences in secondary structural components that increased due to loss of α-helices were noted. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3088–3098, 2009

Memory Metamaterials

The resonant elements that grant metamaterials their distinct properties have the fundamental limitation of restricting their useable frequency bandwidth. The development of frequency-agile metamaterials has helped to alleviate these bandwidth restrictions by allowing real-time tuning of the metamaterial frequency response. We demonstrate electrically controlled persistent frequency tuning of a metamaterial, which allows the lasting modification of its response by using a transient stimulus. This work demonstrates a form of memory capacitance that interfaces metamaterials with a class of devices known collectively as memory devices.

Effects of Yolk Contamination, Shearing, and Heating on Foaming Properties of Fresh Egg White

A series of experiments were conducted to evaluate effects of yolk contamination, shearing, and thermal treatment on foaming properties of liquid egg white. Samples obtained from industrial processing were also evaluated. Whipping and purging methods were both used to assess their effectiveness and sensitivity in evaluating foaming. A concentration as low as 0.022% (as-is basis) of yolk contamination caused significant reductions in foaming capacity and foaming speed. The neutral lipid fraction of egg yolk caused the major detrimental effect on foaming, and phospholipids fraction did not give significant foaming reduction at a concentration as high as 0.1%. High-speed and short-time shearing caused no apparent damage but longer shearing time significantly impaired foaming. Heat-induced foaming change is a function of temperature and holding time. Foaming was significantly reduced at a temperature of 55 degrees C for 10 min, whereas it did not change up to 3 min at a heating temperature of 62 to 64 degrees C. Industrial processing steps (pumping, pipe transfer, and storage) did not produce negative effects on foaming of the final products and the controlled pasteurization was actually beneficial for good foaming performance. Therefore, yolk contamination of the egg white was the major factor in reducing foaming properties of the white protein.

EFFECT OF DIFFERENT COOKING VESSELS ON HEAT INDUCED LIPID PEROXIDATION OF DIFFERENT EDIBLE OILS

Sunflower, coconut, palm and sesame oils were evaluated for heat induced peroxidation as assessed from malondialdehyde (MDA) generation when heated in iron, copper, stainless steel, aluminium and glass vessels on a controlled flame for 0, 5, 10 and 20 min. The MDA generation on heating was time dependent in all the oils. The extent of heat-induced change was the least in coconut oil followed by sesame oil. The heat induced MDA generation was the maximum in sunflower oil. The change was very less in aluminium and glass vessel but was very high in iron and copper vessels. The results show that aside from the level of anti-oxidants and unsaturation of oils, the transitional element used in cooking vessels also determine the extent of heat-induced peroxidation of oils, the impact of which is discussed in light of the harmful effects of MDA on health. PRACTICAL APPLICATIONS Contrary to the view that unsaturated oils are better than saturated oils, the present study shows that MDA generation on heating in relatively saturated oil, like coconut oil, is less in comparison to unsaturated oils. So for frying purposes, coconut oil may be better than other unsaturated oils. In spite of high unsaturation level, heat-induced MDA generation in sesame oil was lower in comparison to sunflower oil probably because of the presence of more antioxidants. Sesame oil may be better than sunflower oil for frying purpose. In view of harmful effects of MDA, heating oil for frying of foodstuffs in vessels made up of transitional metal(s) is probably not a good practice. Aluminium or glass vessel may be better for this purpose.

Dissection of heat-induced systemic signals: superiority of ion fluxes to voltage changes in substomatal cavities

Using non-invasive ion-selective microprobes, that were placed in substomatal cavities, long-distance signalling has been investigated in intact Hordeum vulgare and Vicia faba seedlings. Heat (flame), applied to one leaf (S-leaf), triggers apoplastic ion activity (pH, pCa, pCl) transients in a distant leaf (T-leaf), all largely independent of simultaneously occurring action potential-like voltage changes. While apoplastic pCa and pH increase (Ca(2+)-, H(+)-activities decrease), pCl decreases (Cl(-)-activity increases). As the signal transfer from the S- to the T-leaf is too fast to account for mass flow, the heat-induced pressure change is primarily responsible for changes in voltage (H(+) pump deactivation) as well as for the ion fluxes. The pCa transient precedes the pCl- and pH responses, but not the voltage change. Since the apoplastic pCl decrease (Cl(-) increase) occurs after the pCa increase (Ca(2+) decrease) and after the depolarization, we argue that the Cl(-) efflux is a consequence of the Ca(2+) response, but has no part in the depolarization. Kinetic analysis reveals that pH- and pCl changes are interrelated, indicated by the action of the anion channel antagonist NPPB, which inhibits both pCl- and pH changes. It is suggested that efflux of organic anions into the apoplast causes the pH increase rather than the deactivation of the plasma membrane H(+) pump. Since there is considerably more information in ion activity changes than in a single action- or variation potential and heat-induced ion fluxes occur more reliably than voltage changes, released by milder stimuli, they are considered systemic signalling components superior to voltage.

Temperature-Controlled Photooxygenation with Polymer Nanocapsules Encapsulating an Organic Photosensitizer

A cross-linked poly- N-isopropylacrylamide (polyNIPAM) nanocapsule, TH@PC, containing thionine (TH), an organic photosensitizer, has been synthesized. This capsulated polymeric photosensitizer promotes a singlet oxygen oxygenation ( (1)O 2) accurately controlled by temperature: it shows high oxygenation activity at low temperature, but shows activity decrease with a rise in temperature, resulting in almost zero activity at >40 degrees C. The clear on-off activity control is driven by a heat-induced structure change of the capsule from the swollen single capsule to contracted state, and then to aggregate, behaving as an intelligent (1)O 2 filter. At low temperature, the capsule exists as the swollen single capsule, which allows (1)O 2 diffusion to bulk water, resulting in high oxygenation activity. A rise in temperature leads to contraction of the capsule, reducing the mesh size of the capsule wall. This suppresses (1)O 2 diffusion to bulk water and shows decreased activity. Intercapsule aggregation at >30 degrees C further suppresses (1)O 2 diffusion and shows almost no activity. The capsule promotes reversible activity control regardless of the heating/cooling process and can be reused with a simple recovery process.

Study of Thermal Dynamics of Defatted Bovine Serum Albumin in D2O Solution by Fourier Transform Infrared Spectra and Evolving Factor Analysis

Fourier transform infrared (FT-IR) spectra have been measured for defatted bovine serum albumin (BSA) in D(2)O with a concentration of 2.0 wt % over a temperature range of 26-90 degrees C and the corresponding difference spectra have been calculated by subtracting the contribution of D(2)O at the same temperature. Evolving factor analysis (EFA) by selecting two factors and three factors has been employed to analyze the temperature-dependent difference IR spectra in the 1700-1600 cm(-1) spectral region of the defatted BSA in D(2)O solution. Three-factor EFA has been employed to determine the distinction of the three protein species involved in the process of temperature elevation: native, transitional, and denatured protein. The temperature profiles obtained from three-factor EFA indicate that heat-induced conformational change in the secondary structures of defatted BSA in D(2)O undergoes two two-state transitions, a drastic transition and a slight transition, which occur in the temperature ranges of 68-82 degrees C and 56-76 degrees C, respectively.

The effect of ambient temperature on gross-efficiency in cycling

Time-trial performance deteriorates in the heat. This might potentially be the result of a temperature-induced decrease in gross-efficiency (GE). The effect of high ambient temperature on GE during cycling will be studied, with the intent of determining if a heat-induced change in GE could account for the performance decrements in time trial exercise found in literature. Ten well-trained male cyclists performed 20-min cycle ergometer exercise at 60% P_{V{text{O}}_{{text{2max}}} } (power output at which VO2max was attained) in a thermo-neutral climate (N) of 15.6 ± 0.3°C, 20.0 ± 10.3% RH and a hot climate (H) of 35.5 ± 0.5°C, 15.5 ± 3.2% RH. GE was calculated based on VO2 and RER. Skin temperature (Tsk), rectal temperature (Tre) and muscle temperature (Tm) (only in H) were measured. GE was 0.9% lower in H compared to N (19.6 ± 1.1% vs. 20.5 ± 1.4%) (P < 0.05). Tsk (33.4 ± 0.6°C vs. 27.7 ± 0.7°C) and Tre (37.4 ± 0.6°C vs. 37.0 ± 0.6°C) were significantly higher in H. Tm was 38.7 ± 1.1°C in H. GE was lower in heat. Tm was not high enough to make mitochondrial leakage a likely explanation for the observed reduced GE. Neither was the increased Tre. Increased skin blood flow might have had a stealing effect on muscular blood flow, and thus impacted GE. Cycling model simulations showed, that the decrease in GE could account for half of the performance decrement. GE decreased in heat to a degree that could explain at least part of the well-established performance decrements in the heat.

A novel approach to the visualisation of heat-induced structural change in bone

A new approach to visualising heat-induced change in bone was attempted. This was an attempt to counter the serious limitations of existing analytical methods yet still allow for the examination of subtle changes that occur due to burning. A new form of Magnetic Resonance Imaging was deemed to fulfil this remit. Preliminary tests were performed and proved successful in creating clear, well-defined images of progressive heat-induced structural changes in bone. The implications for improving our understanding of heat-induced change, and therefore our methods of human identification, are significant.

Effects of pH and Polyanions on the Thermal Stability of Fibroblast Growth Factor 20

Fibroblast growth factor 20 (FGF20) is a member of the FGF family with potential for use in several different therapeutic categories. In this work, we provide the first structural characterization of FGF20 using a wide variety of approaches. Like other members of the FGF family, FGF20 appears to possess a beta-trefoil structure. The effect of pH on the conformation and thermal stability of FGF20 is evaluated using far-UV circular dichroism (CD), intrinsic and ANS fluorescence, and high-resolution derivative UV absorption spectroscopy. Empirical phase diagrams are constructed to describe the solution behavior of FGF20 over a wide pH and temperature range. The protein appears to be unstable at pH <5, with aggregation and precipitation observed during dialysis. A major heat-induced conformational change also causes aggregation and precipitation of FGF20 at elevated temperatures. The highest thermal stability is observed near neutral pH (Tm ~55 degrees C at pH 7). The effect of several high- and low-molecular mass polyanions on the thermal stability of FGF20 is also examined using CD, intrinsic fluorescence, and DSC analysis. Among these ligands, heparin exhibits the greatest stabilizing effect on FGF20, increasing the Tm by more than 10 degrees C.