Heat-induced Change Research Articles

Comparative transcriptome profiling of contrasting finger millet (Eleusine coracana (L.) Gaertn) genotypes under heat stress.

Eleusine coracana (L.) Gaertn is a crucial C4 species renowned for its stress robustness and nutritional significance. Because of its adaptability traits, finger millet (ragi) is a storehouse of critical genomic resources for crop improvement. However, more knowledge about this crop's molecular responses to heat stress needs to be gained. In the present study, a comparative RNA sequencing analysis was done in the leaf tissue of the finger millet, between the heat-sensitive (KJNS-46) and heat-tolerant (PES-110) cultivars of Ragi, in response to high temperatures. On average, each sample generated about 24million reads. Interestingly, a comparison of transcriptomic profiling identified 684 transcripts which were significantly differentially expressed genes (DEGs) examined between the heat-stressed samples of both genotypes. The heat-induced change in the transcriptome was confirmed by qRT-PCR using a set of randomly selected genes. Pathway analysis and functional annotation analysis revealed the activation of various genes involved in response to stress specifically heat, oxidation-reduction process, water deprivation, and changes in heat shock protein (HSP) and transcription factors, calcium signaling, and kinase signaling. The basal regulatory genes, such as bZIP, were involved in response to heat stress, indicating that heat stress activates genes involved in housekeeping or related to basal regulatory processes. A substantial percentage of the DEGs belonged to proteins of unknown functions (PUFs), i.e., not yet characterized. These findings highlight the importance of candidate genes, such as HSPs and pathways that can confer tolerance towards heat stress in ragi. These results will provide valuable information to improve the heat tolerance in heat-susceptible agronomically important varieties of ragi and other crops.

Identification of candidate regulators of the response to early heat stress in climate-adapted wheat landraces via transcriptomic and co-expression network analyses.

Climate change is likely to lead to not only increased global temperatures but also a more variable climate where unseasonal periods of heat stress are more prevalent. This has been evidenced by the observation of spring-time temperatures approaching 40°C in some of the main spring-wheat producing countries, such as the USA, in recent years. With an optimum growth temperature of around 20°C, wheat is particularly prone to damage by heat stress. A warming climate with increasingly common fluctuations in temperature therefore threatens wheat crops and subsequently the lives and livelihoods of billions of people who depend on the crop for food. To futureproof wheat against a variable climate, a better understanding of the response to early heat stress is required. Here, we utilised DESeq2 to identify 7,827 genes which were differentially expressed in wheat landraces after early heat stress exposure. Candidate hub genes, which may regulate the transcriptional response to early heat stress, were identified via weighted gene co-expression network analysis (WGCNA), and validated by qRT-PCR. Two of the most promising candidate hub genes (TraesCS3B02G409300 and TraesCS1B02G384900) may downregulate the expression of genes involved in the drought, salinity, and cold responses-genes which are unlikely to be required under heat stress-as well as photosynthesis genes and stress hormone signalling repressors, respectively. We also suggest a role for a poorly characterised sHSP hub gene (TraesCS4D02G212300), as an activator of the heat stress response, potentially inducing the expression of a vast suite of heat shock proteins and transcription factors known to play key roles in the heat stress response. The present work represents an exploratory examination of the heat-induced transcriptional change in wheat landrace seedlings and identifies several candidate hub genes which may act as regulators of this response and, thus, may be targets for breeders in the production of thermotolerant wheat varieties.

Closing in on the heat‐activation mechanisms of TRPV channels

The sensation of heat is mediated by cation-permeable ion channels of the thermoTRP kind. Among these, some of the principal heat-activated ion channels are formed by the TRPV1–4 members of the TRPV subfamily (Latorre et al. 2009). The mechanism by which these membrane proteins convert thermal energy to a channel-opening conformational change is still being intensely investigated and for the most part is not well understood. The availability of high-resolution structures provided by the cryo-EM revolution has made it easier to propose structure–function hypotheses to study heat activation. However, high quality functional studies based in electrophysiology are still the benchmark to prove mechanisms for ion channels. Quantifying the contribution of a channel region to the heat-absorbing step is a difficult task. So far, a good experimental approximation is the estimation of the activation enthalpy associated with the opening of the channel, measured from the steepness of the channel open probability as a function of temperature. In previous seminal work (Yao et al. 2011), the laboratory of Feng Qin identified a so-called membrane proximal domain (MPD), located between the first transmembrane domain and the N-terminal ankyrin repeat domains in all TRPV channels. The authors produced evidence which suggests that the MPD is a main determinant of the activation enthalpy in TRPV1–4 thermoTRP channels. Importantly, the suggestion that this region is involved in a heat-absorbing conformational change was supported by careful measurement of the apparent enthalpy. In the present work, Liu and Qin (2021) further dissect the contribution of the components of the MPD and of individual amino acid residues within the MPD to the apparent enthalpy of activation in TRPV1 and TRPV2 channels. These important new results begin to paint a detailed picture of the fine-tuning involved in channel activation by temperature. TRPV2 channels are the thermoTRP channels with the highest enthalpy of activation –more than double the activation enthalpy of TRPV1 – and are also activated by very high temperatures (>50°C compared to >40°C for TRPV1). Interestingly, the activation of TRPV2 is also different from TRPV1 in that it shows marked hysteresis. TRPV2 channels activate steeply after initial temperature stimuli that do not activate a large fraction of current. Regardless of these differences, Liu and Qin make use of a unique heat-activation technique that relies on rapid infrared laser activation of currents and of chimeric constructions in which parts of the MPD region are swapped between both types of channels to successfully identify a helix–turn–helix motif comprising 10 residues in TRPV2 and 11 residues in TRPV1 that is part of the MPD. Transplantation of this motif between the two channels is enough to produce chimaeras that activate with the enthalpy of activation of the donor channel. Further mutagenesis experiments identified single residues that are implicated in the high temperature dependence of activation of TRPV2. Of particular interest is a serine present in TRPV1 and absent in TRPV2 and TRPV3, another high temperature-activated channel. Reintroduction of the serine in the 10-residue motif of TRPV2 reduced the apparent enthalpy of activation to values comparable to TRPV1. The fact that a single serine is capable of such a large effect suggests that this serine drastically modulates the local structure of the motif or its local interactions or both. According to cryo-EM structures of TRPV2 (Zubcevic et al. 2016), this helix–turn–helix motif is poised to interact with the S2–S3 intracellular loop and the functionally important TRP domain helix. What is the function of the helix–turn–helix in the complete gating cycle of thermoTRP channels? One possibility is that it is part of a protein domain involved in heat absorption, a heat sensor of sorts. As discussed by the authors, this possibility is unlikely due to its small size and the fact that it is generally thought that a large number of interactions are needed to produce high temperature sensitivity. Another possible function for this motif is as a coupling region, capable of transmitting a heat-induced conformational change initiated in other regions of the channel to the activation gate formed by the S6 transmembrane segments. Careful functional experiments such as the ones reported in the present work as well as detailed structural determination of activated and deactivated states will be needed in the future in order to fully understand heat activation in TRPV channels. Meanwhile, these experiments remind us of the immense usefulness of careful electrophysiology. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. None declared. Sole author. Funded by grant DGAPA-PAPIIT-UNAM No. IN215621.

Molecular Basis of IgE-Mediated Shrimp Allergy and Heat Desensitization.

Crustacean allergy, especially to shrimp, is the most predominant cause of seafood allergy. However, due to the high flexibility of immunoglobulin E (IgE), its three-dimensional structure remains unsolved, and the molecular mechanism of shrimp allergen recognition is unknown. Here a chimeric IgE was built in silico, and its variable region in the light chain was replaced with sequences derived from shrimp tropomyosin (TM)-allergic patients. A variety of allergenic peptides from the Chinese shrimp TM were built, treated with heating, and subjected to IgE binding in silico. Amino acid analysis shows that the amino acid residue conservation in shrimp TM contributes to eliciting an IgE-mediated immune response. In the shrimp-allergic IgE, Glu98 in the light chain and other critical residues that recognize allergens from shrimp are implicated in the molecular basis of IgE-mediated shrimp allergy. Heat treatment could alter the conformations of TM allergenic peptides, impact their intramolecular hydrogen bonding, and subsequently decrease the binding between these peptides and IgE. We found Glu98 as the characteristic amino acid residue in the light chain of IgE to recognize general shrimp-allergic sequences, and heat-induced conformational change generally desensitizes shrimp allergens.

Chalcogenide Glass-Capped Fiber-Optic Sensor for Real-Time Temperature Monitoring in Extreme Environments.

We demonstrate a novel chalcogenide glass (ChG)-capped optical fiber temperature sensor capable of operating within harsh environment. The sensor architecture utilizes the heat-induced phase change (amorphous-to-crystalline) property of ChGs, which rapidly (80–100 ns) changes the optical properties of the material. The sensor response to temperature variation around the phase change of the ChG cap at the tip of the fiber provides abrupt changes in the reflected power intensity. This temperature is indicative of the temperature at the sensing node. We present the sensing performance of six different compositions of ChGs and a method to interpret the temperature profile between 440 °C and 600 °C in real-time using an array structure. The unique radiation-hardness property of ChGs makes the devices compatible with high-temperature and high-radiation environments, such as monitoring the cladding temperature of Light Water (LWR) or Sodium-cooled Fast (SFR) reactors.

Biomechanical sensing of in vivo magnetic nanoparticle hyperthermia-treated melanoma using magnetomotive optical coherence elastography.

Rationale: Magnetic nanoparticle hyperthermia (MH) therapy is capable of thermally damaging tumor cells, yet a biomechanically-sensitive monitoring method for the applied thermal dosage has not been established. Biomechanical changes to tissue are known indicators for tumor diagnosis due to its association with the structural organization and composition of tissues at the cellular and molecular level. Here, by exploiting the theranostic functionality of magnetic nanoparticles (MNPs), we aim to explore the potential of using stiffness-based metrics that reveal the intrinsic biophysical changes of in vivo melanoma tumors after MH therapy.Methods: A total of 14 melanoma-bearing mice were intratumorally injected with dextran-coated MNPs, enabling MH treatment upon the application of an alternating magnetic field (AMF) at 64.7 kHz. The presence of the MNP heating sources was detected by magnetomotive optical coherence tomography (MM-OCT). For the first time, the elasticity alterations of the hyperthermia-treated, MNP-laden, in vivo tumors were also measured with magnetomotive optical coherence elastography (MM-OCE), based on the mechanical resonant frequency detected. To investigate the correlation between stiffness changes and the intrinsic biological changes, histopathology was performed on the excised tumor after the in vivo measurements.Results: Distinct shifts in mechanical resonant frequency were observed only in the MH-treated group, suggesting a heat-induced stiffness change in the melanoma tumor. Moreover, tumor cellularity, protein conformation, and temperature rise all play a role in tumor stiffness changes after MH treatment. With low cellularity, tumor softens after MH even with low temperature elevation. In contrast, with high cellularity, tumor softening occurs only with a low temperature rise, which is potentially due to protein unfolding, whereas tumor stiffening was seen with a higher temperature rise, likely due to protein denaturation.Conclusions: This study exploits the theranostic functionality of MNPs and investigates the MH-induced stiffness change on in vivo melanoma-bearing mice with MM-OCT and MM-OCE for the first time. It was discovered that the elasticity alteration of the melanoma tumor after MH treatment depends on both thermal dosage and the morphological features of the tumor. In summary, changes in tissue-level elasticity can potentially be a physically and physiologically meaningful metric and integrative therapeutic marker for MH treatment, while MM-OCE can be a suitable dosimetry technique.

Refining the Properties of Softwood Kraft Lignin with Acetone: Effect of Solvent Fractionation on the Thermomechanical Behavior of Electrospun Fibers

The complexity and polydispersity of lignin, the most abundant aromatic polymer in nature, create great challenges for its valorization for value-added materials and products. Reducing the heterogeneity of industrial lignin and identifying the structure–property relationships are a necessity to achieve predictable and high performance materials for polymeric applications. In this study, a simple one-step solvent extraction method using an industrial solvent, acetone, was presented as a tool to improve the homogeneity of softwood kraft lignin (SKL). The effect of acetone fractionation on the molecular weight (GPC), chemical structure (13C and HSQC NMR), and thermal (DSC and TGA) and dynamical mechanical properties (compressive-torsion DMA) of soluble (ASKL) and insoluble (AISKL) lignin fractions was evaluated. Results showed that two fractions had significant differences in Mw, chemical structure, and functional groups, showing distinct thermal flow and viscoelastic behaviors along with large shifts in the glass-to-rubbery transition temperatures of nearly 80 °C. Electrospun submicron fibers composed of 99 wt % lignin were produced from ASKL and AISKL fractions, which had improved spinnability characteristics compared to their parent SKL lignin. Thermomechanical properties of fiber mats were studied by a tensile dynamical mechanical analyzer, and the heat-induced change in the morphology of fibers was evaluated by SEM. Fiber mats produced from ASKL fractions showed increased water resistance and hydrophobicity as revealed by water contact angle measurements.

Chemosteometric regression models of heat exposed human bones to determine their pre-burnt metric dimensions.

Heat exposure can lead to apparently random osteometric changes that hinder the application of metric methods used for biological profiling. The impracticality of using objective and burn-specific osteometric methods reduces the chances of establishing the biological profiles of unknown individuals based on their skeletal remains. We investigated the potential of chemometry analysis based on infrared spectroscopy to predict the amount of heat-induced osteometric changes and how this reflected into sex estimation. Bones from 41 identified adult skeletons (24 females and 17 males with ages between 62 and 90 years old) were experimentally burnt to maximum temperatures ranging from 450°C to 1,100°C (attained after 65 to 240 min). Measurements were taken both before and after each experiment and powder samples were analyzed through FTIR-ATR. Correlations among heat-induced metric changes and chemometric indices (crystallinity index; B-type carbonates; carbonate [A + B] to carbonate B ratio; hydroxyl to phosphate ratio; 630 cm-1 , 1450 cm-1 , 3572 cm-1 , and 3642 cm-1 ) were tested. Significant variables were used to build regression models to predict heat-induced metric change which were then tested on an independent set of samples. Agreement in sex estimation between the pre- and post-burnt samples was also evaluated. All indices were significantly correlated to heat-induced metric changes (α = .01) and the highest correlations were obtained for the 630 cm-1 , 3572 cm-1 , and crystallinity index. We confirmed that regression models based on chemometrics obtained from infrared spectra through FTIR-ATR are better at estimating heat-induced metric changes affecting bone and at sexing remains than other osteometric methods such as those based on correction factors or on metric references specific to calcined bones. Regression models avoid the subjectivity associated with the application of other methods. While the latter can be applied only to calcined bones, which is difficult to assess sometimes, regression models can be applied to all bones regardless of their condition. Also, regression models have the advantage of allowing to infer about heat-induced metric change on a case-by-case basis.

Changes in microcapsules under heating: the effect of particle size on thermal stability and breakability

In this work, the effect of particle size on the thermal stability and bursting phenomenon of the microcapsules with a melamine resin shell was studied. The heat-induced change process and mechanism of the prepared microcapsules were derived. Firstly, the microcapsules with different particle sizes were prepared and characterized via encapsulation efficiency measurements, optical microscopy, and scanning electron microscopy. The thermogravimetric analysis curves of the samples were calculated, analyzed, and compared with the samples’ particle size and distribution, and the changes and differences in the microcapsules under heating environment were macroscopically studied. Furthermore, thermo-microscopic image analysis of the samples was conducted using a laboratory-combined instrument system, and their dynamic morphology in a temperature-increasing environment was microscopically investigated. On the basis of these data, it was found that the thermal bursting phenomenon occurred when the microcapsule particle size was larger than the “critical dimension.” And as the particle sizes decreased, their heat rupture resistance was improved, and the trend of change was described by an exponential function (y = 133.64 + 94.76 × 0.85x). When the microcapsule size was smaller than the critical dimension, the thermal bursting phenomenon disappeared and the thermal stability was depended on the degradation temperature of the MMF shell.

Spectroscopic Comparison of Thermal Transport at Organic-Inorganic and Organic-Hybrid Interfaces Using CsPbBr3 and FAPbBr3 (FA = Formamidinium) Perovskite Nanocrystals.

Thermal transport across interfaces depends on the matching of vibrational structure at the interface. This work examines the transfer of thermal excitation from an organic ligand coating to either all-inorganic cesium lead tribromide (CsPbBr3) nanocrystals or hybrid organic-inorganic formamidinium lead tribromide (FAPbBr3) nanocrystals using selective infrared optical excitation. These two semiconductors are directly compared because they (or similar semiconductors) are currently envisioned as strong candidates in many optoelectronic technologies and they differ due to the presence of an organic or inorganic cation, which introduces substantial differences in the phonon density of states in otherwise quite similar semiconductors. Infrared excitation of C-H vibrations of surface-bound ligands generates a temperature gradient between the organic ligand shell and nanocrystal core, which results in heat flow, measured by probing changes of the semiconductor band gap. Heat transfer to both perovskite compositions of comparable sizes is similar (25-30 ps), due to fast intramolecular vibrational relaxation and similar matching of low-energy phonons with the organic ligand, but FAPbBr3 samples show a slow bleaching kinetic on the order of 1 ns. This slow, heat-induced change in the semiconductor band gap is attributed not to interfacial heat transfer but instead to thermal equilibration between the organic and inorganic sublattices of FAPbBr3. Ab initio molecular dynamics simulations support the hypothesis that low-energy inorganic sublattice phonon modes are populated initially in the heat transfer process, with a slow thermal population of the higher-energy phonon modes associated primarily with the organic cation. Slow thermal equilibration of FAPbBr3 is likely to substantially impact the time-dependent response of optoelectronic devices that heat the semiconductor active layer and provide further evidence that the poor bulk thermal transport of hybrid perovskite materials extends to microscopic thermal processes.

A phase-change thin film-tuned photonic crystal device

This paper reports a tunable photonic device that incorporates a thin layer of phase-change material, Ge2Sb2Te5 (GST), in a photonic crystal (PC) structure. The PC structure is based on a one-dimensional grating waveguide with a metal cladding. The metal-cladded PC structure supports a guided-mode resonance (GMR) that selectively absorbs light at a particular wavelength. Inserting the GST material into the gating waveguide makes it possible to control the GMR mode. Here, the GST-PC device was numerically designed and optimized to obtain significant tuning of the GMR mode around 1550 nm. The tuning phenomena were experimentally demonstrated by the heat-induced phase change between crystalline and amorphous phases of the GST thin film. A spectral shift of the resonant wavelength from 1440 to 1610 nm was achieved via the crystallization process. The phase tuning of GST exhibits good repeatability as demonstrated by switching between amorphous and crystalline phases of GST for multiple cycles. The GST-PC device represents a new approach for tuning optical resonances with potential applications including but not limited to integrated photonic circuits, optical communications, and high-performance optical filters.

High-Temperature Strength of Copper-Based Condensed Materials

The temperature dependences of Vickers microhardness, ultimate strength, and offset yield point in the temperature range between 290 and 1070 K were determined for the transversal direction in copper-based composites Cu–Zr–Y–Mo, Cu–Cr, Cu–C, and Cu–W. The materials produced by electron-beam evaporation/condensation are used for the manufacture of current collectors which, when in operation, are subjected to intensive wear and electrical erosion as well as to mechanical loading at elevated temperatures. This production method provides composite materials with a special layered structure, where copper layers are interspersed with dispersed-particle layers of other metals. The paper describes the procedures of Vickers microhardness and tensile testing at high temperatures. A general thermodynamic activation analysis of the derived relationships of hardness and strength has been performed for various copper-based composite systems in the range of (0.2–0.8)Tmelt of copper. A comparative analysis of the obtained values of the activation energy of plastic deformation of copper and copper-based composites as well as the theoretical and experimental data on deformation, internal friction, creep, and self-diffusion processes in copper has revealed that in a wide range of temperatures the activation energy of plastic deformation undergoes a significant change during a transition from one temperature region to another. This is indicative of a successive changeover of effective (governing) thermally activated mechanisms of plastic deformation. It is proved that a heat-induced change in the strength characteristics (hardness, ultimate strength, offset yield point) of the composites studied is controlled by the same plastic deformation mechanisms whose temperature regions coincide.

Conformationally Flexible Bis(9‐fluorenylidene)porphyrin Diradicaloids

A stable 5,10-bis(9-fluorenylidene)porphyrin (Por-Fl) diradicaloid was synthesized. It shows a quinoidal, saddle-shaped geometry in the single crystal but can be thermally populated to a triplet diradical both in solution and in the solid state. Coordination with the Ni2+ ion (Por-Fl-Ni) does not significantly change the contorted conformation but reduces the singlet-triplet gap. Heat-induced geometric change can explain the observed paramagnetic properties as well as unusual hysteresis in SQUID measurements. On the other hand, protonation (Por-Fl-2H+ ) dramatically changes the conformation while maintains the closed-shell electronic structure. Our studies demonstrate how heat, coordination, and protonation affect the geometry, diradical character, and physical properties of conformationally flexible open-shell singlet diradicaloids.

The effect of dynamical compressive and shear strain on magnetic anisotropy in a low symmetry ferromagnetic film

Dynamical strain generated upon excitation of a metallic film by a femtosecond laser pulse may become a versatile tool enabling control of the magnetic state of thin films and nanostructures via inverse magnetostriction on a picosecond time scale. Here, we explore two alternative approaches to manipulate magnetocrystalline anisotropy and excite magnetization precession in a low-symmetry film of a magnetic metallic alloy galfenol (Fe,Ga), either by injecting a picosecond strain pulse into it from a substrate, or by generating dynamical strain of a complex temporal profile in the film directly. In the former case, we realize ultrafast excitation of magnetization dynamics solely by strain pulses. In the latter case, optically-generated strain emerging abruptly in the film modifies its magnetocrystalline anisotropy, competing with heat-induced change of anisotropy parameters. We demonstrate that the optically-generated strain remains efficient for launching magnetization precession, when the heat-induced changes of anisotropy parameters do not trigger the precession any more. We emphasize that in both approaches the ultrafast change of magnetic anisotropy mediating the precession excitation relies on the mixed, compressive, and shear character of the dynamical strain, which emerges due to low-symmetry of the metallic film under study.

Interactions in casein micelle – Pea protein system (part I): Heat-induced denaturation and aggregation

The aim of this work was to investigate the heat-induced interactions between pea proteins (vicilin 7S or legumin 11S enriched-fractions) in admixture with suspended casein micelles (SCM), at weight protein ratio of 1:1 and pH 7.1. The single-protein samples and mixtures thereof were prepared at concentrations of 18 and 36 mgprotein/gsample, respectively, then heated from 40 to 85 °C and incubated for 0–60 min. As compared to single-protein samples, differential scanning calorimetry (DSC) data indicated that the denaturation temperature of pea proteins increased of about 4 °C in the presence of SCM. Heat-induced change in protein composition of the soluble (SP) and micellar (MP) phases from centrifuged SCM – pea protein mixture was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and densitometry. Likewise SP was analyzed by size-exclusion chromatography (SEC-HPLC). While pea legumin 11S and vicilin 7S oligomers were markedly sedimentable in MP from their respective unheated mixture, thermal denaturation and protein aggregation (≥75 °C) resulted in increasing levels of dissolved pea proteins in SP. Heating of the SCM – legumin mixture (85 °C, 15–60 min incubation) resulted in the dissociation of the legumin subunits Lαβ into acidic Lα and basic Lβ polypeptides, yielding in comparable amounts soluble and insoluble disulfide-bonded aggregates, respectively. In contrast in the SCM – vicilin mixture, the heat-denatured vicilin polypeptides in a temperature range of 70–80 °C produced in majority soluble and non-covalent aggregates. Though the heat-induced interactions between pea proteins were altered in the presence of micelles, caseins would not be involved into pea proteins aggregation.

Systems biology of aging.

Human aging occurs at rates that vary widely between organisms and cell types. We hypothesize that in both cases, variation is due to differences in heat production, heat management and molecular susceptibility to heat-induced change. Metabolic rates have long been implored for their contributions to the aging process, with a negative correlation observed between basal metabolic rate and lifespan (Savage et al., Proc Natl Acad Sci U S A 104:4718–4723, 2007, Economos, Exp Gerontol 17:145–152, 1982, Keys et al., Metabolism 22:579–587, 1973, O’Connor et al., Comp Biochem Physiol Part A, Molr & Integr Physiol 133:835–842, 2002, Speakman, J Exp Biol 208:1717–1730, 2005, Poehlman, J Am Geriatrics Soc 41:552–559, 1993). Small amounts of heat are the well-known byproduct of metabolism and other biological processes, and despite their magnitude, are sufficient to elicit alterations in biomolecular characteristics (Somero, Ann Rev Physiol 57:43–68, 1995). Existing theories of aging suggest that damage occurs to the conformations or sequences of molecules, which only shifts focus onto the implied failure of repair mechanisms. Contrarily, heat-induced changes affect the behavioral characteristics of molecules and are thus able to persist “under the radar” of heat shock proteins and other canalizing mechanisms, which recognize only physical aberrancies (Rutherford and Lindquist, Nature 396:336–342, 1998, Siegal and Bergman, Proc Natl Acad Sci U S A 99:10528–10532, 2002, Waddington, Nature 150:563–565, 1942). According to our hypothesis, behavioral changes to the binding affinities, kinetics, motilities, and functionalities are dependent on minute energetic fields within and between molecules. Exposure to the thermal byproducts of metabolism cause heritable shifts in molecular interaction schemes and diminish the integrity of genetic and epigenetic networks. Restructured topologies alter the emergent properties of networks and are observed as the increased variation and decreased functionality associated with “aging” (Moorad and Promislow, Proc Royal Soc B Biol Sci 276:2271–2278, 2009, Soltow et al., Integr Comp Biol 50:844–854, 2010, Siegal et al.,Genetica 129:83–103, 2007, Promislow,Proc Biol sci/The Royal Soc 271:1225–1234, 2004, Southworth et al., PLoS Genet 5:e1000776, 2009, Rodwell et al.,PLoS Biol 2:e427, 2004). A major hurdle in the development of this hypothesis was overcome with the discovery of protein moonlighting: the phenomenon by which proteins assume drastically different functions independent of conformational change (Jeffery, Trends Biochem Sci 24:8–11, 1999). This molecular mechanism validates the hypothesis that network and behavioral changes can undergo somatic inheritance, and be accumulated by daughter cells over the course of a lifetime. Once a damage threshold has been surpassed, a system can no longer sustain life, and death results.

Drying Characteristics of Carrots Immersed in a Fluidized Bed of Fluidizing Particles Under Reduced Pressure

The drying characteristics and properties (color and shrinkage) of carrots (as a representative agricultural product) were experimentally examined in a fluidized bed under reduced pressure. Dry hot air and superheated steam were used as the drying gases. Rice and carrot powders (0.125–0.355 mm in diameter) were used as the fluidizing particles, in addition to glass beads (0.12 mm in diameter). It was confirmed that the drying rate using a fluidized bed was much higher than without a fluidized bed (hot-air drying), regardless of the type of fluidizing particles used. Under reduced pressure, both with and without a fluidized bed, the drying rate was higher than that at atmospheric pressure using hot air. The drying rate was sufficiently high for fluidized-bed drying with superheated steam, though the drying rate was higher with hot air than with superheated steam. As the drying temperature increased, the volume ratio (befor/after drying) of the sample increased. At high drying temperatures (373 and 423 K in the present study), the color of the sample changed; in other words, a heat-induced change in the properties of the carrot was observed. At a low drying temperature (333 K in the present study), the drying method did not affect the color of the carrot; i.e., the color of the dried material was maintained even in a fluidized bed under reduced pressure when the drying rate was higher.

Crystal Structure and Thermodynamic and Kinetic Stability of Metagenome-Derived LC-Cutinase

The crystal structure of metagenome-derived LC-cutinase with polyethylene terephthalate (PET)-degrading activity was determined at 1.5 Å resolution. The structure strongly resembles that of Thermobifida alba cutinase. Ser165, Asp210, and His242 form the catalytic triad. Thermal denaturation and guanidine hydrochloride (GdnHCl)-induced unfolding of LC-cutinase were analyzed at pH 8.0 by circular dichroism spectroscopy. The midpoint of the transition of the thermal denaturation curve, T1/2, and that of the GdnHCl-induced unfolding curve, Cm, at 30 °C were 86.2 °C and 4.02 M, respectively. The free energy change of unfolding in the absence of GdnHCl, ΔG(H2O), was 41.8 kJ mol(-1) at 30 °C. LC-cutinase unfolded very slowly in GdnHCl with an unfolding rate, ku(H2O), of 3.28 × 10(-6) s(-1) at 50 °C. These results indicate that LC-cutinase is a kinetically robust protein. Nevertheless, the optimal temperature for the activity of LC-cutinase toward p-nitrophenyl butyrate (50 °C) was considerably lower than the T1/2 value. It increased by 10 °C in the presence of 1% polyethylene glycol (PEG) 1000. It also increased by at least 20 °C when PET was used as a substrate. These results suggest that the active site is protected from a heat-induced local conformational change by binding of PEG or PET. LC-cutinase contains one disulfide bond between Cys275 and Cys292. To examine whether this disulfide bond contributes to the thermodynamic and kinetic stability of LC-cutinase, C275/292A-cutinase without this disulfide bond was constructed. Thermal denaturation studies and equilibrium and kinetic studies of the GdnHCl-induced unfolding of C275/292A-cutinase indicate that this disulfide bond contributes not only to the thermodynamic stability but also to the kinetic stability of LC-cutinase.

Structure and magnetic properties of electrodeposited Ni87.3Fe11.3W1.4 alloy

A dark gray nanostructured coating of an alloy composed of 87.3wt.% Ni, 11.3wt.% Fe and 1.4wt.% W (Ni87.3Fe11.3W1.4) was electrodeposited from an ammonia citrate bath on a titanium cathode at a current density of 500mAcm−2.A cathodic polarization curve was recorded and dependence of the current efficiency of alloy deposition on current density was determined. Partial polarization curves for alloy deposition and hydrogen evolution were also measured. Alloy deposition at current densities of up to 300mAcm−2 is an activation-controlled process which turns into a diffusion-controlled process at higher current densities. At potentials more positive than −960mV, hydrogen is evolved from NH4+ and (HCit)3− ions (where (HCit)3− denotes triply deprotonated citric acid, C6H5O73−). At potentials more negative than −960mV, hydrogen evolution from water is the dominating reaction.SEM images show that the surface of the deposit obtained at 500mAcm−2 has a globular structure containing a large number of craters, mostly located between the globules.XRD analysis revealed that the alloy contains an amorphous matrix with embedded nanocrystals of the FCC-structured solid solution of Fe and W in Ni with a mean particle size of 8.8nm. The deposit has a high internal microstrain value and a high density of chaotically distributed dislocations.Heating and milling the alloy cause structural changes involving changes in the magnetic properties of the alloy. Structural relaxation takes place in the temperature interval of 80°C tо 420°C. In this temperature range, magnetization of both as-deposited and milled alloy samples increases with increasing temperature, reaching maximum at a certain temperature, but decreases thereafter with further heating. During structural relaxation, short-term structural arrangement facilitates the expansion and orientation of magnetic domains, leading to increased magnetization of the alloy. The abrupt decline in magnetization at higher temperatures is the result of a heat-induced change in magnetic domain orientation.Annealing the alloy at temperatures above 420°C causes amorphous phase crystallization and growth of crystal grains of the FCC-structured solid solution of Fe and W in Ni, as well as a simultaneous decrease in internal microstrain and mean density of chaotically distributed dislocations. The same structural changes, somewhat lower in intensity, are also caused by alloy milling. The new state of the microstructure achieved through annealing and milling is best illustrated by the mean crystal size. The increase in mean crystal size results in a shift of the Curie temperature towards lower temperatures, whereas magnetization increases at first, reaching maximum at a certain mean crystal size, but decreases, thereafter, with a further increase in mean crystal size.

Gold Nanorods with Phase‐Changing Polymer Corona for Remotely Near‐Infrared‐Triggered Drug Release

Herein, we report a new drug-delivery system (DDS) that is comprised of a near-infrared (NIR)-light-sensitive gold-nanorod (GNR) core and a phase-changing poly(ε-caprolactone)-b-poly(ethylene glycol) polymer corona (GNR@PCL-b-PEG). The underlying mechanism of the drug-loading and triggered-release behaviors involves the entrapment of drug payloads among the PCL crystallites and a heat-induced phase change, respectively. A low premature release of the pre-loaded doxorubicin was observed in PBS buffer (pH 7.4) at 37 °C (<10% of the entire payload after 48 h). However, release could be activated within 30 min by conventional heating at 50 °C, above the Tm of the crystalline PCL domain (43.5 °C), with about 60% release over the subsequent 42 h at 37 °C. The NIR-induced heating of an aqueous suspension of GNR@PCL-b-PEG under NIR irradiation (802 nm) was investigated in terms of the irradiation period, power, and concentration-dependent heating behavior, as well as the NIR-induced shape-transformation of the GNR cores. Remotely NIR-triggered release was also explored upon NIR irradiation for 30 min and about 70% release was achieved in the following 42 h at 37 °C, with a mild warming (<4 °C) of the surroundings. The cytotoxicity of GNR@PCL-b-PEG against the mouse fibroblastic-like L929 cell-line was assessed by MTS assay and good compatibility was confirmed with a cell viability of over 90% after incubation for 72 h. The cellular uptake of GNR@PCL-b-PEG by melanoma MEL-5 cells was also confirmed, with an averaged uptake of 1250(±110) particles cell(-1) after incubation for 12 h (50 μg mL(-1)). This GNR@PCL-b-PEG DDS is aimed at addressing the different requirements for therapeutic treatments and is envisaged to provide new insights into DDS targeting for remotely triggered release by NIR activation.