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Crowded environments, commonly found in the food system, are utilized to enhance the properties of soybean proteins. Despite their widespread application, little information exists regarding the impact of crowded environments on the denaturation behaviors of soybean proteins. In this study, we investigated how crowding agents with varying molecular weights, functional groups, and topology affect the denaturation behavior of glycinin under crowded conditions. The results reveal that thermal stability in PEG crowded environments is mainly influenced by both preferential hydration and binding. The stabilization is primarily enthalpy-driven, with aggregation contributing additional entropic stabilization. Specifically, ethylene glycol and diethylene glycol exhibit temperature-dependent, bilateral effects on glycinin stability. At the denaturation temperature, hydrophobic interactions play a predominant role, decreasing glycinin's thermal stability. However, at a molecular weight of 200 g/mol, there is a delicate balance between destabilizing and stabilizing effects, leading to no significant change in thermal stability. With the addition of PEG 400, 1000, and 2000, besides preferential hydration, additional hard-core repulsions between glycinin molecules enhance thermal stability. Methylation modification experiments demonstrated that 2-methoxyethyl ether exerted a more pronounced denaturing effect. Additionally, the cyclization of PEG 1000 decreased its stabilizing effect., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A temperature measurement subsystem (TMS) is a critical piece of infrastructure of the space gravitational wave detection platform, necessary for monitoring minuscule temperature changes at the level of 1μK/Hz1/2 within the electrode house, in the frequency range of 0.1mHz to 1Hz. The voltage reference (VR), a key component of the TMS, must possess low noise characteristics in the detection band to minimize the impact on temperature measurements. However, the noise characteristics of the voltage reference in the sub-millihertz range have not been documented yet and require further study. This paper reports a dual-channel measurement method for measuring the low-frequency noise of VR chips down to 0.1mHz. The measurement method makes use of a dual-channel chopper amplifier and an assembly thermal insulation box to achieve a normalized resolution of 3×10-7/Hz1/2@0.1mHz in the VR noise measurement. The seven best-performance VR chips documented at a common frequency range are tested. The results show that their noise at sub-millihertz frequencies can significantly differ from that around 1Hz.

SnS 2 /reduced graphite oxide (rGO) composite materials show great potential as high-performance anode candidates in sodium-ion batteries (SIBs) owing to their high specific capacities and power densities. However, the repeated formation/decomposition of the solid electrolyte interface (SEI) layer around composite anodes usually consumes additional sodium cations, resulting in poor Coulombic efficiency and decreasing specific capacity upon cycling. Therefore, in order to compensate for the large irreversible sodium loss of the SnS 2 /rGO anode, this study has proposed a facile strategy by implementing organic solutions of sodium-biphenyl/tetrahydrofuran (Na-Bp/THF) and sodium-naphthylamine/dimethoxyethane (Na-Naph/DME) as chemical presodiation reagents. Particularly, the storage stability of Na-Bp/THF and Na-Naph/DME in ambient air accompanied by their presodiation behavior on the SnS 2 /rGO anode has been investigated, and both reagents exhibited desirable ambient air-tolerant storage stability with favorable sodium supplement effects even after 20 days of storage. More importantly, the initial Coulombic efficiency (ICE) of SnS 2 /rGO electrodes could be controllably increased by immersing in a presodiation reagent for different durations. Consequently, with a facile chemical presodiation strategy of immersion in Na-Bp/THF solution for only 3 min in ambient air, the presodiated SnS 2 /rGO anode has exhibited an outstanding electrochemical performance with a high ICE of 95.6% as well as an ultrahigh specific capacity of 879.2 mAh g -1 after 300 cycles (83.5% of its initial capacity), highly superior to the pristine SnS 2 /rGO anode. This efficient and scalable presodiation strategy provides a new avenue for the prevailing application of other anode candidates in high-energy SIBs.

Studying high-sensitivity fiber-optic temperature sensors is vital in pursuing high-precision temperature measurement. We propose a liquid-sealed multimode interference fiber temperature sensor with a double-taper structure. The influence of structure and sealed-liquid material on the temperature sensitivity of the sensor is analyzed experimentally. The results show that the tapered structure can effectively improve the temperature sensitivity of the sensor, and the effect becomes more evident with the increased refractive index of the sealed liquid. As the refractive index of the sealed liquid increases, the temperature sensitivity of the sensor can be effectively improved. However, the sealed liquid with a high refractive index will increase the failure temperature of the sensor. Near the failure temperature, the sensor achieves an ultra-high-temperature sensitivity of -8.28 n m / K . The results also prove that further increasing the refractive index of the sealed liquid no longer has a significant gain in temperature sensitivity. It is expected that the relevant research will contribute to the development of high-precision temperature-sensing systems.

The statics and dynamics of supercooled water in the hydration layer of poly(ethylene glycol) (PEG) were studied by a combination of quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations. Two samples, that is, hydrogenated PEG/deuterated water (h-PEG/D 2 O) and fully deuterated PEG/hydrogenated water (d-PEG/H 2 O) with the same molar ratio of ethylene glycol (EG) monomer to water, 1:1, are compared. The QENS data of h-PEG/D 2 O show the dynamics of PEG, and that of d-PEG/H 2 O reveals the motion of water. The temperature-dependent elastic scattering intensity of both samples has shown transitions at supercooled temperature, and these transition temperatures depend on the energy resolution of the instruments. Therefore, neither one is a phase transition, but undergoes dynamic process. The dynamic of water can be described as an Arrhenius to super-Arrhenius transition, and it reveals the hydrogen bonding network relaxation of hydration water around PEG at supercooled temperature. Since the PEG-water hydrogen bond structural relaxation time from MD is in good agreement with the average relaxation time from QENS (d-PEG/H 2 O), MD may further reveal the atomic pictures of the supercooled hydration water. It shows that hydration water molecules form a series of pools around the hydrophilic oxygen atom of PEG. At supercooled temperature, they have a more bond ordered structure than bulk water, proceed a trapping sites diffusion on the PEG surface, and facilitate the structural relaxation of PEG backbone., (© 2022 Author(s).)

As a kind of negative electrode material for sodium-ion batteries (SIBs), tin-based active compounds have attracted numerous research efforts in recent years due to relatively high theoretical capacity. However, sluggish reaction kinetics for large-radius sodium ions hinders the practical application of layered tin-based anodes such as tin disulfide (SnS 2 ) in SIBs. In this study, polyethylene glycol (PEG) is introduced as an intercalant and reduced graphene oxide (rGO) is utilized as the substrate to prepare a novel PEG-SnS 2 /rGO composite with expanded layer spacing (0.921 nm) through a facile hydrothermal process. SnS 2 flakes in a size range of 50-100 nm are uniformly grown on the graphene sheet, the CS covalent bonding demonstrates a tight connection between the active SnS 2 particles and the graphene skeleton, which is conductive to convenient charge transfer during the electrochemical process. Owing to the significantly improved sodium ions transport kinetics and fast electronic conductive network, the PEG-SnS 2 /rGO composite presents a high capacitance contribution of 90.69% at a scan rate of 0.6 mV s -1 . It delivers a high reversible capacity of 960.6 mAh g -1 at 0.1 A g -1 , good cycling performance with 770 mAh g -1 remained after 100 charge/discharge cycles, and excellent rate capability with an ultrahigh capacity of 720 mAh g -1 at 5 A g -1 . This work provides new insights into the design of a kinetically favorable anode material for SIBs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The development of high-efficiency, robust, and available electrode materials for oxygen evolution reaction (OER) and lithium-ion batteries (LIBs) is critical for clean and sustainable energy system but remains challenging. Herein, a unique yolk-shell structure of Fe 2 O 3 nanotube@hollow Co 9 S 8 nanocage@C is rationally prepared. In a prearranged sequence, the fabrication of Fe 2 O 3 nanotubes is followed by coating of zeolitic imidazolate framework (ZIF-67) layer, chemical etching of ZIF-67 by thioacetamide, and eventual annealing treatment. Benefiting from the hollow structures of Fe 2 O 3 nanotubes and Co 9 S 8 nanocages, the conductivity of carbon coating and the synergy effects between different components, the titled sample possesses abundant accessible active sites, favorable electron transfer rate, and exceptional reaction kinetics in the electrocatalysis. As a result, excellent electrocatalytic activity for alkaline OER is achieved, which delivers a low overpotential of 205 mV at the current density of 10 mA cm -2 along with the Tafel slope of 55 mV dec -1 . Moreover, this material exhibits excellent high-rate capability and excellent cycle life when employed as anode material of LIBs. This work provides a novel approach for the design and the construction of multifunctional electrode materials for energy conversion and storage., (© 2021 The Authors. Small published by Wiley-VCH GmbH.)

The study of ion specificities of charged-neutral random copolymers is of great importance for understanding specific ion effects on natural macromolecules. In the present work, we have investigated the specific anion effects on the thermoresponsive behavior of poly([2-(methacryloyloxy)ethyl trimethylammonium chloride]- co - N -isopropylacrylamide) [P(METAC- co -NIPAM)] random copolymers. Our study demonstrates that the anion specificities of the P(METAC- co -NIPAM) copolymers are dependent on their chemical compositions. The specific anion effects on the copolymers with high mole fractions of poly( N -isopropylacrylamide) (PNIPAM) are similar to those on the PNIPAM homopolymer. As the mole fraction of PNIPAM decreases to a certain value, a V-shaped anion series can be observed in terms of the anion-specific cloud point temperature of the copolymer, as induced by the interplay between different anion-polymer interactions. Our study also suggests that both the direct and the indirect anion-polymer interactions contribute to the anion specificities of the copolymers. This work would improve our understanding of the relationship between the ion specificities and the ion-macromolecule interactions for naturally occurring macromolecules.

As an anode electrode material for lithium-ion batteries, SnS has high specific capacity and has received widespread attention, but its practical application is still hindered by the low reversibility of the conversion reaction and the large irreversible capacity caused by the solid electrolyte interphase (SEI). In this paper, SnS nanoparticles are encapsulated into a sulfur-doped graphene bubble film (SnS@G) by a scalable electrostatic self-assembly of SnS 2 /graphene oxide and hexadecyl trimethyl ammonium bromide, followed by the thermal decomposition of SnS 2 and sulfur doping in graphene. Due to electrostatic attraction, the SnS nanoparticles are tightly wrapped in multilayer graphene sheets to form a flake-graphite-like structure. Compared with the disordered stacked SnS/graphene sheet composite, the closely packed SnS@G shows a much lower specific surface area and smaller irreversible Li + consumption and surface film resistance after lithiation. The SnS@G composite anode exhibits great initial coulombic efficiency (83.2%), which is the highest value among the chemically synthesized SnS anodes. It also presents unprecedented cycling stability (1462 mA h g -1 after 200 cycles at 0.1 A g -1 and 1020 mA h g -1 after 500 cycles at 1 A g -1 ) and superior rate capabilities (750 mA h g -1 at 5 A g -1 ) upon Li storage, which demonstrates its excellent electrochemical performance and great potential as a negative electrode material for lithium-ion batteries.

In this work, we demonstrate an interesting structural phase transition from SnS2/reduced graphene oxide to SnS/sulfur-doped graphene at a moderate calcination temperature of 500 °C under an inert atmosphere. It is discovered that SnS2 chemically bound to rGO with a weakened C-S bond is easier to break and decompose into SnS, whereas it is difficult for pure-phase crystalline SnS2 to experience phase transformation at this temperature. Moreover, the thin-layered structure of SnS2 and rGO is an important factor for the effective doping of the dissociated Sx into graphene. Density functional theory calculations also reveal the feasibility of the structural phase transition process. Morphology characterization shows that partial SnS maintains the original nanosheet structure (∼100 nm) and the others are decomposed into tiny nanoparticles (10-20 nm). A high S-doping amount reduces the irreversible lithium storage sites on graphene, and the first coulombic efficiency is as high as 81.7%. In addition, thin-layered and small-sized SnS can alleviate the structural damage caused by volume expansion and shrinkage; therefore, a high specific capacity of 893.9 mA h g-1 is retained after 100 cycles.

Materials with a low coefficient of thermal expansion (CTE) are extremely demanded in many fields, varying from microelectronics to space technology. Here we report a novel method to achieve low CTE, which differs essentially from the conventional way that uses additives with negative thermal expansion (NTE) to compensate for the positive CTE of the matrix. The stoichiometric Hf 0.87 Ta 0.13 Fe 2+ x ( x = 0) shows a giant NTE, which is gradually suppressed with increasing x and finally changed to near-zero thermal expansion (ZTE) at x ≈ 0.4. The excess Fe was suggested to form anti-site defects by occupying the 4f sites. As revealed by electron spin resonance (ESR) spectra, the weakened NTE is closely related to a slower ferromagnetic (FM) ordering process than observed at x = 0. In addition, the CTE can be further tuned by introducing an extra α-Fe phase to achieve a low CTE (e.g., 3.3 ppm/K for x = 1.0) with markedly enhanced mechanical properties, beneficial to applications.

This study presents a process of developing a novel PI3K-mTOR inhibitor through the prodrug of a metabolite. The lead compound (compound 1) was identified with similar efficacy as that of NVP-BEZ235 in a tumor xenograft model, but the exposure of compound 1 was much lower than that of NVP-BEZ235. After reanalysis of the blood sample, a major metabolite (compound 2) was identified. Compound 2 exerted similar in vitro activity as compound 1, which indicated that compound 2 was an active metabolite and that the in vivo efficacy in the animal model came from compound 2 instead of compound 1. However, compound 1 was metabolized into compound 2 predominantly in the liver microsomes of mouse, but not in the liver microsomes of rat, dog, or human. In order to translate the efficacy in the animal model into clinical development or predict the pharmacokinetic/pharmacodynamic parameters in the clinical study using a preclinical model, we developed the metabolite (compound 2) instead of compound 1. Due to the low bioavailability of compound 2, its prodrug (compound 3) was designed and synthesized to improve the solubility. The prodrug was quickly converted to compound 2 through both intravenous and oral administrations. Because the prodrug (compound 3) did not improve the oral exposure of compound 2, developing compound 3 as an intravenous drug was considered by our team, and the latest results will be reported in the future., Competing Interests: Disclosure Yan Zhou, Genyan Zhang, Feng Wang, Jin Wang, Yanwei Ding, Xinyu Li, Chongtie Shi, Jiakui Li and Chengkon Shih all work for Xuanzhu Pharma, Jinan, China. The authors report no other conflicts of interest in this work.

Folding and aggregation of proteins profoundly influence their functions. We have investigated the effects of thermal history, concentration and pH on the denaturation and refolding of lysozyme by using ultrasensitive differential scanning calorimetry (US-DSC) and sedimentation velocity (SV) via analytical ultracentrifugation (AUC). The former is sensitive to small energy change whereas the latter can differentiate the oligomers such as dimer and trimer from individual protein molecules. Our studies reveal that the degree of denaturation irreversibility increases as heating times increases. The denaturation temperature (Td) and enthalpy change (ΔH) are influenced by heating rate since the denaturation is not in equilibrium during the heating. We can obtain Td and ΔH in equilibrium by extrapolation of heating rate to zero. In a dilute solution, no aggregation but unfolding happens in the denaturation. However, when the concentration is above a critical value (∼15.0 mg/mL), lysozyme molecules readily form trimers or other oligomers. Lysozyme molecules unfold into stretched chains at pH > 6.0, which would further forms large aggregates. The formation of aggregates makes the refolding of lysozyme impossible.

Background: Several occupational stress studies of healthcare workers have predicted a high prevalence of anxiety symptoms, which can affect their quality of life and the care that they provide. However, few studies have been conducted among community healthcare workers in China. We attempted to explore whether burnout mediates the association between occupational stress and anxiety symptoms., Methods: A cross-sectional survey was completed in Liaoning Province, China from November to December 2012. A total of 1,752 healthcare workers from 52 Community Health Centers participated in this study, and all participants were given self-administered questionnaires. These questionnaires addressed the following aspects: the Zung Self-Rating Anxiety Scale, the Chinese version of the effort-reward imbalance scale and the Maslach Burnout Inventory-General Survey. Finally, the study included 1,243 effective respondents (effective response rate, 70.95%). Hierarchical linear regression analysis, performed with SPSS 17.0, was used to estimate the effect of burnout., Results: The prevalence of anxiety symptoms among the community healthcare workers was 38.0%. After adjusting for demographic characteristics, the effort-reward ratio and overcommitment positively predicted anxiety symptoms. Meanwhile, the effort-reward ratio and overcommitment were positively related to the emotional exhaustion and cynicism subscales of burnout. In addition, the emotional exhaustion and cynicism subscales were positively related to anxiety symptoms. Thus, there is a link between burnout, occupational stress and anxiety symptoms., Conclusions: Burnout mediates the effect of occupational stress on anxiety symptoms. To effectively reduce the impact of occupational stress on anxiety symptoms, burnout management should be considered.

The effect of urea on the phase transition of PNIPAM was studied using differential scanning calorimetry (DSC). For a certain urea concentration, the enthalpy change of phase transition of poly(N-isopropylacrylamide) (PNIPAM) aqueous solution increases with the number of DSC cycles, presumably due to the displacement of water molecules bound to the amide groups of PNIPAM by urea molecules at the temperature higher than the lower critical solution temperature (LCST) of PNIPAM and causes the decrease in the absolute value of the exothermic heat related to the dehydration of hydrophilic groups and interactions of hydrophilic residues to around 0. Moreover, the enthalpy change decreases with the urea concentration during the heating process of the first DSC cycle, indicating the replacement of water molecules around the apolar isopropyl groups by urea molecules at the temperature lower than LCST, and the endothermic heat caused by the dehydration of apolar groups decreases. Furthermore, the urea molecules which replace the water molecules at high temperature can be replaced again by water molecules at the temperature lower than LCST, but this process needs several days to complete.

We report our discovery of a novel series of potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors. Starting from a lead identified by scaffold-hopping approach, our discovery and development efforts were focused on exploring structure-activity relationships, optimizing pharmacokinetic profile, improving in vitro and in vivo efficacy, and evaluating safety profile. The selected candidate, Imigliptin, is now undergoing clinical trial.

The solution behaviors and microstructures of poly(N-isopropylacrylamide)x-poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20-poly(N-isopropylacrylamide)x (PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx or PNIPAmx-P123-PNIPAmx) pentablock terpolymers with various PNIPAm block lengths in dilute and concentrated aqueous solutions were investigated by micro-differential scanning calorimetry (micro-DSC), static and dynamic light scattering (SLS & DLS), and synchrotron small angle X-ray scattering (SAXS). Two lower critical solution temperatures (LCSTs) were observed for PNIPAmx-P123-PNIPAmx pentablock terpolymers in dilute solutions, which corresponded to LCSTs of PPO and PNIPAm blocks, respectively. The LCST of PPO block shifted from 24.4 °C to 29 °C when the length x of PNIPAm block increased from 10 to 97. The LCST of PNIPAm is around 34.5 °C-35.3 °C and less dependent on the block length x. The PNIPAmx-P123-PNIPAmx pentablock terpolymers formed "associate" structures and micelles with hydrophobic PNIPAm and PPO blocks as cores and soluble PEO blocks as coronas in dilute aqueous solutions at 20 °C and 40 °C, respectively, regardless of the relative lengths of PNIPAm, PPO and PEO blocks. The size of "associate" structures of PNIPAmx-P123-PNIPAmx pentablock terpolymers at 20 °C increased with increasing the length of PNIPAm block. The microstructures of PNIPAmx-P123-PNIPAmx hydrogels formed in concentrated aqueous solutions (40 wt%) were strongly dependent on the environmental temperatures and relative lengths of PNIPAm, PPO and PEO blocks as revealed by SAXS. Increasing the length of PNIPAm block weakened the order structures of PNIPAmx-P123-PNIPAmx hydrogels. The microstructures of PNIPAmx-P123-PNIPAmx hydrogels changed from mixed fcc and hex structures for PNIPAm10-P123-PNIPAm10 to isotropic structure for PNIPAm97-P123-PNIPAm97. Increasing temperature led to the transition from mixed hex and fcc structure to pure hex structure for PNIPAm10-P123-PNIPAm10 hydrogel at temperature above the LCSTs.

Ethylene glycol (EG) and hydrogen peroxide (H2O2) can act as both hydrogen-bond donors and acceptors in the formation of solvent complexes with water molecules. In the present work, we have systematically investigated the ion-specific lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) in H2O–EG and H2O–H2O2 mixtures. The results obtained from turbidity measurements show that the specific anion effect is amplified with the increasing molar fraction of EG (x(EG)) but is independent of the molar fraction of H2O2 (x(H2O2)). The studies of Raman spectra and differential scanning calorimetry indicate that the discrepancy in amplification of specific anion effect between H2O–EG and H2O–H2O2 mixtures is due to the difference in the anion–solvent complex interactions rather than the anion–polymer or solvent–polymer interactions. On the other hand, the specific cation effect can also be amplified with the increasing x(EG) but changes only slightly with the x(H2O2). The discrepancy in amplification of specific cation effect between the two types of solvent mixtures is attributed to the difference in the solvent–polymer interactions.

By choosing poly(N,N-diethylacrylamide) which lacks the possibility to form intra- or inter-chain hydrogen bonds, we studied its chain association and dissociation in water by using laser light scattering (LLS), ultrasensitive differential scanning calorimetry (US-DSC) and Fourier transform infrared spectroscopy (FTIR). As the solution temperature increases, the average hydrodynamic radius (R(h)) and average radius of gyration (R(g)) decrease, indicating the intrachain shrinking. When the temperature is higher than its lower critical solution temperature (LCST, approximately 30 degrees C), the apparent weight-average molar mass (M(w,app)) increases, reflecting the interchain association. At the same time, FTIR study reveals that as the temperature increases, the area ratio of two absorption peaks, respectively, associated to one hydrogen bonded carbonyl >C=O...H-O-H and free carbonyl >C=O groups increases, while that related to two hydrated hydrogen bonded carbonyl groups decreases, indicating heating-induced dehydration. In the reversible cooling process, R(h), R(g), M(w,app) and area ratios of the absorption peak are similar to those in the heating process for each given temperature, indicating that there is no hysteresis in the interchain association and dissociation. This present study confirms that the hysteresis previously observed for a sister polymer, poly(N-isopropylacrylamide), is due to the formation of some additional hydrogen bonds in its collapsed state at temperatures higher than the LCST.

Human upstream binding factor (hUBF) HMG Box-5 is a highly conserved protein domain, containing 84 amino acids and belonging to the family of the nonspecific DNA-binding HMG boxes. Its native structure adopts a twisted L shape, which consists of three alpha-helices and two hydrophobic cores: the major wing and the minor wing. In this article, we report a reversible three-state thermal unfolding equilibrium of hUBF HMG Box-5, which is investigated by differential scanning calorimetry (DSC), circular dichroism spectroscopy, fluorescence spectroscopy, and NMR spectroscopy. DSC data show that Box-5 unfolds reversibly in two separate stages. Spectroscopic analyses suggest that different structural elements exhibit noncooperative transitions during the unfolding process and that the major form of the Box-5 thermal intermediate ensemble at 55 degrees C shows partially unfolded characteristics. Compared with previous thermal stability studies of other boxes, it appears that Box-5 possesses a more stable major wing and two well separated subdomains. NMR chemical shift index and sequential (1)H(N) (i)-(1)H(N) (i+1) NOE analyses indicate that helices 1 and 2 are native-like in the thermal intermediate ensemble, while helix 3 is partially unfolded. Detailed NMR relaxation dynamics are compared between the native state and the intermediate ensemble. Our results implicate a fluid helix-turn-helix folding model of Box-5, where helices 1 and 2 potentially form the helix 1-turn-helix 2 motif in the intermediate, while helix 3 is consolidated only as two hydrophobic cores form to stabilize the native structure.

The hydrogen bonding interactions of the triple helical lentinan, beta-(1-->3)-D-glucan from Lentinus edodes, in the mixtures of dimethyl sulfoxide (DMSO) and water were investigated by light scattering, viscometry, and ultrasensitive differential scanning calorimetry (US-DSC). The results revealed that two conformation transitions occurred in the lentinan solution with an increase of temperature. A reversible transition from triple helix I to triple helix II, namely, from a high degree of immobilization of the backbone to a more freely rotating one, occurred in the temperature range from 8 to 45 degrees C. The other was an irreversible conformation transition from triple helix to single strand flexible chain at 90-140 degrees C, depending on the DMSO concentration. The side chain of the triple helix I lentinan combined with water clusters through hydrogen bonds to form an associating water layer in the first region, leading to a high degree of immobilization of the backbone. However, the side chain could rotate in triple helix II at slightly elevated temperature, as a result of the breaking of the associating structure with relatively lower energy. The second transition resulted from the destruction of the intra- and intermolecular hydrogen bonds in lentinan, which sustain the triple helical structure. Furthermore, the transition in the high temperature region showed high cooperation, suggesting that the intra- and intermolecular hydrogen bonds with the relatively high energy were destructed simultaneously. Therefore, the diversity of the hydrogen bonds created the multiple conformational transitions of the triple helical polysaccharide in the aqueous solution.

By use of isothermal titration calorimetry (ITC) and ultrasensitive differential scanning calorimetry (US-DSC), we have investigated the energy change in the periodic swelling-to-deswelling of thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) microgels containing ruthenium(II) tris(2,2'-bipyridine) (Ru(bpy)3) which is a catalyst for Belousov-Zhabotinsky (BZ) reaction. As temperature increases, the induction period and oscillation period of BZ reaction decrease because the reaction rate increases. However, the oscillation disappears at a temperature above the lower critical solution temperature (LCST) of the microgels since Ru(bpy)3 is trapped in the microgels and cannot react with BZ substrates. As microgel size increases or the cross-linking density decreases, the restriction of polymer networks on Ru(bpy)3 decreases, so that Ru(bpy)3 can readily contact with BZ substrates, leading the oscillation amplitude to increase. In addition, the so-called transient chaos occurs at a low stirring speed, and it wanes with the increasing stirring speed. All the facts indicate that the contact between Ru(bpy)3 and BZ substrates determines the oscillation of the microgels.

Escherichia coli DNA photolyase repairs cyclobutane pyrimidine dimer (CPD) in UV-damaged DNA through a photoinduced electron transfer mechanism. The catalytic activity of the enzyme requires fully reduced FAD (FADH (-)). After purification in vitro, the cofactor FADH (-) in photolyase is oxidized into the neutral radical form FADH (*) under aerobic conditions and the enzyme loses its repair function. We have constructed a mutant photolyase in which asparagine 378 (N378) is replaced with serine (S). In comparison with wild-type photolyase, we found N378S mutant photolyase containing oxidized FAD (FAD ox) but not FADH (*) after routine purification procedures, but evidence shows that the mutant protein contains FADH (-) in vivo as the wild type. Although N378S mutant photolyase is photoreducable and capable of binding CPD in DNA, the activity assays indicate the mutant protein is catalytically inert. We conclude that the Asn378 residue of E. coli photolyase is crucial both for stabilizing the neutral flavin radical cofactor and for catalysis.

Poly(N-isopropylmethacrylamide) (PiPMA) has one more methyl group at each monomeric unit than poly(N-isopropylacrylamide) (PiPA). By use of laser light scattering (LLS) and ultrasensitive differential scanning calorimetry (US-DSC) we have investigated the association and dissociation of PiPMA chains in water. LLS studies reveal that PiPMA chains form larger aggregates at a temperature above its lower critical solution temperature (LCST) as the chain molar mass (Mw) decreases. In comparison with PiPA aggregates, PiPMA aggregates show a larger ratio of average radius of gyration to average hydrodynamic radius (/), indicating that PiPMA aggregates are looser. US-DSC studies show PiPMA chains have smaller enthalpy change (DeltaH) and entropy change (DeltaS) than PiPA chains during the phase transition, indicating that PiPMA chains have smaller conformational change. Our experiments demonstrate that the additional methyl groups in PiPMA chains restrain the intrachain collapse and interchain association, leading the phase transition to occur at a higher temperature.

The effects of the concentration (C) and heating rate on the collapse and association of poly(N-isopropylacrylamide) chains in water have been investigated by use of ultrasensitive differential scanning calorimetry. In the dilute solutions, both the phase transition temperature (Tp) and enthalpy change (DeltaH) increase with the heating rate but decrease with concentration. By extrapolation to zero heating rate and zero concentration, Tp and DeltaH for coil-to-globule transition of a single chain in thermodynamic equilibrium can be obtained. In semidilute solutions, both Tp and DeltaH increase with the heating rate but slightly vary with the concentration. Tp and DeltaH for pure interchain association in equilibrium are obtained by extrapolation to zero heating rate. Our experiments reveal that only intrachain contraction occurs when the concentration is infinitely close to zero. When the concentration is above the overlap concentration (C*), only interchain association exists. In the range 0

Triose phosphate isomerase (TIM) was prepared and purified from chicken breast muscle. The equilibrium unfolding of TIM by urea was investigated by following the changes of intrinsic fluorescence and circular dichroism spectroscopy, and the equilibrium thermal unfolding by differential scanning calorimetry (DSC). Results show that the unfolding of TIM in urea is highly cooperative and no folding intermediate was detected in the experimental conditions used. The thermodynamic parameters of TIM during its urea induced unfolding were calculated as DeltaG degrees =3.54 kcal.mol(-1), and m(G) = 0.67 kcal.mol(-1)M(-1), which just reflect the unfolding of dissociated folded monomer to fully unfolded monomer transition, while the dissociation energy of folded dimer to folded monomer is probe silence. DSC results indicate that TIM unfolding follows an irreversible two-state step with a slow aggregation process. The cooperative unfolding ratio, DeltaH(cal)/DeltaH(vH), was measured close to 2, indicating that the two subunits of chicken muscle TIM unfold independently. The van't Hoff enthalpy, DeltaH(vH), was estimated as about 200 kcal.mol(-1). These results support the unfolding mechanism with a folded monomer formation before its tertiary structure and secondary structure unfolding.

The denaturation of collagen solution in acetic acid has been investigated by using ultra-sensitive differential scanning calorimetry (US-DSC), circular dichroism (CD), and laser light scattering (LLS). US-DSC measurements reveal that the collagen exhibits a bimodal transition, i.e., there exists a shoulder transition before the major transition. Such a shoulder transition can recover from a cooling when the collagen is heated to a temperature below 35 degrees C. However, when the heating temperature is above 37 degrees C, both the shoulder and major transitions are irreversible. CD measurements demonstrate the content of triple helix slowly decreases with temperature at a temperature below 35 degrees C, but it drastically decreases at a higher temperature. Our experiments suggest that the shoulder transition and major transition arise from the defibrillation and denaturation of collagen, respectively. LLS measurements show the average hydrodynamic radius R(h), radius of gyration R(g)of the collagen gradually decrease before a sharp decrease at a higher temperature. Meanwhile, the ratio R(g)/R(h) gradually increases at a temperature below approximately 34 degrees C and drastically increases in the range 34-40 degrees C, further indicating the defibrillation of collagen before the denaturation., ((c) 2007 Wiley Periodicals, Inc.)

N-Isopropylacrylamide-co-acrylamidophenylboronic acid (NIPAM-co-PBA) microgels were prepared by free radical polymerization in water. The release of glucose and Alizarin Red S (ARS) from the microgels as a function of temperature has been investigated by using laser light scattering (LLS) and ultrasensitive differential scanning calorimetry (US-DSC). Such microgels can bind glucose and ARS via boronic acids at a lower temperature. As the temperature increases, the microgels shrink, and the diols are released. The release could be controlled by temperature. The effect of the structure of the microgels on the release is also discussed.

The lower critical solution temperature (LCST) behaviors of random and segmented copolymers of N-isopropylacrylamide (NIPAM) and acrylic acid (AA) prepared in dioxane and water have been investigated by using ultrasensitive microcalorimetry (US-DSC). The introduction of AA increases the LCST of the former but slightly affects that of the latter. When the molar fraction of AA is low (approximately 2 mol %), the LCST of the segmented copolymer shifts to a higher temperature with increasing pH, while the LCST of the corresponding random copolymer slightly changes. Below the boiling point of water, the random copolymer and segmented copolymer with the molar fraction of AA about 15 mol % no longer exhibit an LCST at pH > 5. The addition of calcium ions leads the LCST of both the segmented copolymer and random copolymer to decrease. Our results suggest that the LCST behavior of the copolymers is determined by the clustering of poly(N-isopropylacrylamide) segments.