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The advanced spiral growth model that considers the thermodynamics and kinetics aspects of the adsorption process is applied to predict the growth habits of the nitroguanidine crystal in water and ...

Molecular dynamics simulation on the reaction of nano-aluminum particle and water were performed by ReaxFF force field. The different reaction rates of aluminum with H2O and D2O indicate that the effect of kinetic isotope effect (KIE) is obvious. The generation rate of H2 is 20% higher than that of D2. The mechanism of formation and consumption of AlH3 as well as the generation of Al2O3 are elucidated. Specifically, the most frequent reaction pathways throughout the full period are clarified based on the changes of numbers of intermediate and final products. The reactions in the early period are endothermic and release isolated H atoms, which involves Al +3H2O → Al(OH)3 + 3H and 3Al + 2H2O → 2AlO + AlH3 + H. Afterwards, the reactions release a large amount of energy and generate H2 molecules in the later period, in accordance with the equations of 2AlO + H2O → Al2O3 + H2, Al(OH)3 + AlH3 → Al2O3 + 3H2 and 2AlH3 + 3H2O → Al2O3 + 6H2. The initial pathways are in agreement with early DFT investigations. The diffusion coefficients of the different atoms show that the replacement of H2O by D2O reduces the diffusion rate of all the atoms (5%) in the system. The KIE is confirmed, and the results agree with experiments. In addition, the simulations were performed under different maximum temperatures. Results show that the solid residues become more disperse in space as the temperature increase.

CuO/ZIF-8 hybrid structure was obtained by adding the PVP-modified foliaceous CuO microstructures during the preparation of ZIF-8 polygon particles as a promising candidate for promoting the thermolysis process of NC. Thermoanalysis and pyrolysis kinetics based on the DSC and TG/DTG data revealed that the CuO/ZIF-8-NC decomposition had a weightlessness rate of 77.81%, heat release of 2882.5 J⋅g−1, the exothermic peak temperature of 471.25 K, and activation energy of 172.2 ± 16.0 kJ⋅mol−1, indicating that CuO/ZIF-8 has better catalytic activity than CuO and ZIF-8. The reconstructed nth-order kinetic models for NC/catalysis complexes were obtained using a modified fitting algorithm based on the results of isoconversional kinetic analysis, indicating that CuO/ZIF-8, CuO, and ZIF-8 had different catalytic effects on the thermolysis pathways of NC. This study suggests that CuO/ZIF-8 composite may have prospective application as a high potential and unique catalyst for accelerating NC pyrolysis.

Background It is well known that peptides play a vital role in the nutrition and health of dairy cows. Bovine oligopeptide transporter 1 (bPepT1) is involved in the peptide transport process in the gastrointestinal tracts of dairy cows. However, little information is known in the characteristics of bPepT1. Therefore, the purpose of this study was to characterize bPepT1 functionally using a mammalian cell expression system. The uptake of radiolabeled dipeptide glycyl-sarcosine ([3H]-Gly-Sar) into the bPepT1-transfected Chinese hamster ovary cells was measured at various pH and substrate concentrations and with or without 15 other small peptides that contained Met or Lys. Results Western blot results showed that the abundance of bPepT1 protein in the jejunum and ileum are the highest in the gastrointestinal tract of dairy cows. The uptake of [3H]-Gly-Sar by bPepT1-Chinese hamster ovary cells was dependent on time, pH, and substrate concentration, with a low Km value of 0.94 ± 0.06 mmol/L and a maximum velocity of 20.80 ± 1.74 nmol/(mg protein • 5 min). Most of the di- and tripeptides were the substrates of bPepT1, based on substrate-competitive studies. However, bPepT1 has a higher affinity to the peptides with shorter chains, greater hydrophobicity, and negative or neutral charges. Conclusions These results demonstrated for the first time the functional characteristics of bPepT1, and they provide a new insight and better understanding into its vital role in absorbing a wide range of peptides from the digestive tract of dairy cows.

Development of the high energy and low signature propellants with controllable heat releases is always desirable but challenging. Herein, four versatile energetic materials, multi-metal hexanitro complexes (K3[Co(NO2)6], K2Pb[M(NO2)6] (M = Cu2+, Ni2+, Co2+)) as potential catalysts and flash suppressors of the propellants, have been prepared and characterized, and their effects on the non-isothermal and adiabatic decomposition behaviors and kinetics, pyrolysis pathway, heat release, laser ignition and flame propagation properties of RDX have been studied. The results showed that the structure, composition, powder color, and morphology of the hexanitro complexes were transformed due to the substation of transition metal cations, resulting in their different thermal behaviors. The study of the non-isothermal decomposition kinetics showed that the decomposition peak temperature and activation energy (Ea) of RDX was decreased by the addition of hexanitro complexes, and addition of K2Pb[Co(NO2)6] to RDX has the lowest activation energy, while the replacing of the transition metal cations Cu2+ and Ni2+ for Co2+ cannot improve the catalytic activity. The influence of hexanitro complexes on the main pyrolysis pathway of RDX was studied by the TG-FTIR technique, and it is found that the decomposition products (NO and metal oxides) of hexanitro complexes resulted in the transformation of the pyrolysis mechanism of RDX. The adiabatic decomposition results showed that the RDX/K2Pb[Cu(NO2)6] had the largest self-heat rate and the lowest Ea, whereas the RDX/K2Pb[Co(NO2)6] have the shortest time to maximum rate under adiabatic condition. The addition of K2Pb[Cu(NO2)6] to RDX resulted in the largest total heat release, the fastest release rate, and the lowest ignition delay time. The results from the non-isothermal and adiabatic decomposition, heat release and ignition presented that the diverse metal cations in the hexanitro complexes led to the different catalytic performances, which indicated the tunable catalytic activities of hexanitro complex systems to RDX pyrolysis. The hexanitro complexes facilitated the mass and heat transfer in the flame propagation process, owing to the formation of enormous gaseous products and microparticles. Therefore, the tunable characterization of energetic hexanitro complexes demonstrated that these complexes have a large potential application for controlling the heat release of the solid propellants.

The objective of this study was to characterize the expression profile, transport kinetics, and regulation of peptide transporters in bovine mammary epithelial cells (BMECs). Quantitative reverse-transcription real-time PCR, Western blotting, and immunofluorescence staining were used to investigate the expression of peptide transporters in bovine mammary tissues. The effects of time, pH, concentration, and specific inhibitors on β-alanyl-l-lysyl- Ne-7-amino-4-methyl-coumarin-3-acetic acid (β-Ala-Lys-AMCA) uptake in BMECs were also studied. The results showed that the peptide transporters PepT2 and PhT1 are both expressed in bovine mammary glands. The optimal pH for the uptake of β-Ala-Lys-AMCA in BMECs was 6.5. The transport-kinetics study suggested that the uptake of β-Ala-Lys-AMCA in BMECs is saturable over the tested concentration, with a Km value of 82 ± 18 μM and a Vmax of 124 ± 11 pmol/min per milligram of protein. Other dipeptides, including Gly-Sar, Met-Gly, and Met-Met, competitively inhibited β-Ala-Lys-AMCA uptake in BMECs. However, histidine had no effect on β-Ala-Lys-AMCA uptake. Furthermore, knocking down PepT2 could significantly reduce β-Ala-Lys-AMCA uptake, but PhT1 interference had no effect on peptide uptake in BMECs. The inhibition of PI3K and Akt decreased the uptake of β-Ala-Lys-AMCA. The above results revealed functional characteristics of peptide transporters and demonstrated that PepT2 may play a major role in β-Ala-Lys-AMCA uptake in BMECs. Moreover, the PI3K-Akt signaling pathway may regulate the uptake of β-Ala-Lys-AMCA in BMECs.

The molar enthalpies of dissolution for 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) in dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure. Empirical formulae for the calculation of the molar enthalpies of dissolution (Δdiss H), relative partial molar enthalpies (Δdiss H partial) and relative apparent molar enthalpies (Δdiss H apparent) were obtained from the experimental data of the dissolution processes of LLM-105 in DMSO or NMP. Furthermore, the corresponding kinetic equations describing the two dissolution processes were dα/dt = 10−2.37(1 − α)0.47 for the dissolution of LLM-105 in DMSO, and dα/dt = 10−2.38(1 − α)0.42 for the dissolution of LLM-105 in NMP.

The molar enthalpies of dissolution for potassium salt of bis(dinitromethyl)difurazanyl ether [K2(BDFE)] in N-methyl-2-pyrrolidone (NMP) and water were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure. Empirical formulae for the calculation of the molar enthalpies of dissolution (Δdiss H), relative partial molar enthalpies (Δdiss H partial), and relative apparent molar enthalpies (Δdiss H apparent) were obtained from the experimental data of the dissolution processes of K2(BDFE) in NMP or water. Furthermore, the corresponding kinetic equations describing the two dissolution processes were dα/dt = 10−4.11(1 − α)1.12 for the dissolution of K2(BDFE) in NMP and dα/dt = 10−3.76(1 − α)0.88 for the dissolution of K2(BDFE) in water.

The dissolution properties of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowutrzitane (TEX) in N-methyl pyrrolidone (NMP) were studied with a RD496-2000 Calvet microcalorimeter at four different temperatures. The heat effects were measured for TEX in NMP. The molar enthalpies and the differential molar enthalpies for TEX in NMP were also obtained at the same time. The corresponding kinetic equations that describe the four dissolution processes are dα/dt = 10−2.64(1−α)1.31 (T = 298.15 K), dα/dt = 10−2.58(1−α)1.31 (T = 303.15 K), dα/dt = 10−2.54(1−α)1.51 (T = 308.15 K), dα/dt = 10−2.49(1−α)1.03 (T = 313.15 K), and respectively. The values of activation energy E a and pre-exponential factor A for TEX in the dissolution process are 16.84 kJ mol−1 and 100.32 s−1.

The enthalpies of dissolution of dihydrazidinium bis(tetrazolyl)amine (DHBTA) in water and N-methyl pyrrolidone (NMP) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure, respectively. Empirical formulae for the calculation of the enthalpy of dissolution (Δdiss H), relative partial molar enthalpy (Δdiss H partial) and relative apparent molar enthalpy (Δdiss H apparent) were obtained from the experimental data of the dissolution processes of DHBTA in water and NMP. Furthermore, the corresponding kinetic equations describing the two dissolution processes were dα/dt = 10−2.70(1 − α)0.82 for the dissolution of DHBTA in water, and dα/dt = 10−2.47(1 − α)0.66 for the dissolution of DHBTA in NMP, respectively.

Insulin is considered to be a classical central regulator of energy homeostasis. Recently, the effect of insulin on bone has gained a lot of attention, but little attention has been paid to the application in bone tissue engineering. In this study, porous nanohydroxyapatite/collagen (nHAC) scaffolds incorporating poly lactic-co-glycolic acid (PLGA) particles were successfully developed as an insulin delivery platform for bone regeneration. Bioactive insulin was successfully released from the PLGA particles within the scaffold, and the size of the particles as well as the release kinetics of the insulin could be efficiently controlled through Shirasu porous glass premix membrane emulsification technology. It was indicated that the nHAC/PLGA composite scaffolds possessed favorable mechanical and structural properties for cell adhesion and proliferation, as well as the differentiation into osteoblasts. It was also demonstrated that the nHAC/PLGA scaffolds implanted into a rabbit critical-size mandible defect possessed tissue compatibility and higher bone restoration capacity compared with the defects that were filled with or without nHAC scaffolds. Furthermore, the in vivo results showed that the nHAC/PLGA scaffolds which incorporated insulin-loaded microspheres with a size of 1.61 μm significantly accelerated bone healing compared with two other composite scaffolds. Our study indicated that the local insulin released at the optimal time could substantially and reproducibly improve bone repair.

The dissolution properties of ammonium dinitramide (ADN) in N-methyl pyrrolidone (NMP) were studied with a RD496-2000 Calvet microcalorimeter at four different temperatures under atmospheric pressure. The heat effects were determined for ADN in NMP. The molar enthalpies and the differential molar enthalpies for ADN in NMP were also obtained at the same time. The corresponding kinetic equations that describe the four dissolution processes are discussed.

In this paper, the decomposition reaction models and thermal hazard properties of 1,3,5-trinitro-1,3,5-triazinane (RDX) and its PBXs bonded by Formex P1, Semtex 1A, C4, Viton A and Fluorel polymer matrices have been investigated based on isoconversional and combined kinetic analysis methods. The established kinetic triplets are used to predict the constant decomposition rate temperature profiles, the critical radius for thermal explosion and isothermal behavior at a temperature of 82. °C. It has been found that the effect of the polymer matrices on the decomposition mechanism of RDX is significant resulting in very different reaction models. The Formex P1, Semtex and C4 could make decomposition process of RDX follow a phase boundary controlled reaction mechanism, whereas the Viton A and Fluorel make its reaction model shifts to a two dimensional Avrami-Erofeev nucleation and growth model. According to isothermal simulations, the threshold cook-off time until loss of functionality at 82. °C for RDX-C4 and RDX-FM is less than 500 days, while it is more than 700 days for the others. Unlike simulated isothermal curves, when considering the charge properties and heat of decomposition, RDX-FM and RDX-C4 are better than RDX-SE in storage safety at arbitrary surrounding temperature. © 2014 Elsevier B.V.

A new energetic zinc-FOX-7 complex, Zn(NH3)2(FOX-7)2 (FOX-7 = 1,1-diamino-2,2-dinitroethylene), was first synthesized. Thermal decomposition behavior and nonisothermal decomposition kinetics of Zn(NH3)2(FOX-7)2 were studied with DSC and TG/DTG methods. The kinetic equation obtained is $$ \frac{{{\text{d}}\alpha }}{{{\text{d}}T}} = \frac{{10^{13.99} }}{\beta }4(1 - \alpha )[ - \ln (1 - \alpha )]^{{{3 \mathord{\left/ {\vphantom {3 4}} \right. \kern-0pt} 4}}} \exp ( - 1.448 \times 10^{5} /RT) $$ . The self-accelerating decomposition temperature (T SADT) and critical temperature of thermal explosion (T b) are 183.2 and 195.8 °C, respectively. The specific-heat capacity of Zn(NH3)2(FOX-7)2 was determined with a micro-DSC method, and the molar-heat capacity is 454.6 J mol−1 K−1 at 298.15 K. Adiabatic time-to-explosion was also estimated to be about 20 s. The thermal stability of Zn(NH3)2(FOX-7)2 is good and higher than that of analogous Cu(NH3)2(FOX-7)2.

Lead salt of 4-amino-3,5-dinitropyrazole (PDNAP) was synthesized from 4-amino-3,5-dinitropyrazole by the process of metathesis reaction, and its structure was characterized by IR, element analysis, TG, and DSC. The thermal decomposition kinetics and mechanism were studied by means of different heating rate differential scanning calorimetry (DSC) and thermolysis in situ rapid-scan FTIR simultaneous. The effects of PDNAP as an energetic combustion catalyst on the combustion performance of the solid propellant were studied. The results show that the peak temperature is 319.2 °C on DSC curve. The kinetic equation of major exothermic decomposition reaction is $$ \frac{{\text{d}}\alpha}{{\text{d}}T} = \frac{{10^{15.45} }}{\beta }4(1 - \alpha )[ - \ln \left( {1 - \alpha } \right)]^{{{3 \mathord{\left/ {\vphantom {3 4}} \right. \kern-0pt} 4}}} \exp ({{ - 1.972 \times 10^{5} } \mathord{\left/ {\vphantom {{ - 1.972 \times 10^{5} } {RT}}} \right. \kern-0pt} {RT}}). $$ The PDNAP is shown by IR spectroscopy to convert to PbO during the decomposition process. Combustion experiments show PDNAP can reduce the burning rate pressure exponent of the double-base or composite-modified double-base propellant.

Two energetic strontium(II) complexes with nitrogen-rich 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) were synthesized. The metal complexes were characterized by IR, elemental analysis, and single-crystal X-ray diffraction. DSC and TG-DTG were used to study the thermal behavior, non-isothermal decomposition reaction kinetics, self-accelerating decomposition temperature (T SADT), thermal ignition temperature (T TIT), critical temperature of thermal explosion (T b), and the adiabatic time-to-explosion (t TIad). The data indicate competitive energetic materials.

The thermal behavior and decomposition kinetics of C4-bonded PBXs based on some attractive cyclic nitramines were investigated by means of nonisothermal TG and DSC techniques. It has been shown that only a single decomposition process has been observed for RDX-C4 while an obvious two-step process for mixture of BCHMX-C4 CL-20-C4, and HMX-C4. The onset temperature of the exotherms were observed at 216.3, 238.7, 279.2 and 236.7 °C with the peak temperatures of 235.1, 279.0, 231.2 and 233.7 °C for RDX-C4, BCHMX-C4, HMX-C4 and CL-20-C4, respectively. Their corresponding exothermic decompostion processes were covered by energy changes of 1749, 1938, 1213 and 2639 J g −1 , which are lower than that of their pure cyclic nitramines. It was also proved that C4 matrix has significant effect on the activation energy distribution of RDX, BCHMX and CL-20, whose initial autocatalysis effect was inhibited or weakened. With regard to HMX-C4, the activation energy of its initial step is much lower than that of the second step.

The enthalpies of dissolution for ammonium dipicrylamide (ADPA) in dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP) were measured using a RD496-2000 Calvet microcalorimeter at 298.15 K under atmospheric pressure. Empirical formulae for the calculation of the enthalpies of dissolution (ΔdissH) were obtained from the experimental data of the dissolution processes of ADPA in DMSO and NMP. The linear relationships between the rate (k) and the molality (b) were found. The corresponding kinetic equations describing the two dissolution processes were d α / d t = 10 − 2.38 ( 1 − α ) 0.86 for the dissolution of ADPA in DMSO, and d α / d t = 10 − 2.49 ( 1 − α ) 0.83 for the dissolution of ADPA in NMP, respectively.

Glucose is an essential substrate for lactose synthesis and an important energy source in milk production. Glucose uptake in the mammary gland, therefore, plays a critical role in milk synthesis. Facilitative glucose transporters (GLUT) mediate glucose uptake in the mammary gland. Glucose transporter 1 (GLUT1) is the major facilitative glucose transporter expressed in the bovine mammary gland and has been shown to localize to the basolateral membrane of mammary epithelial cells. Glucose transporter 1 is, therefore, thought to play a major role in glucose uptake during lactation. The objective of this study was to determine the transport kinetic properties and substrate specificity of bovine GLUT1 using the Xenopus oocyte model. Bovine GLUT1 (bGLUT1) was expressed in Xenopus oocytes by microinjection of in vitro transcribed cRNA and was found to be localized to the plasma membrane, which resulted in increased glucose uptake. This bGLUT1-mediated glucose uptake was dramatically inhibited by specific facilitative glucose transport inhibitors, cytochalasin B, and phloretin. Kinetic analysis of bovine and human GLUT1 was conducted under zero-trans conditions using radio-labeled 2-deoxy-D-glucose and the principles of Michaelis-Menten kinetics. Bovine GLUT1 exhibited a Michaelis constant (K(m)) of 9.8 ± 3.0mM for 2-deoxy-d-glucose, similar to 11.7 ± 3.7 mM for human GLUT1. Transport by bGLUT1 was inhibited by mannose and galactose, but not fructose, indicating that bGLUT1 may also be able to transport mannose and galactose. Our data provides functional insight into the transport properties of bGLUT1 in taking up glucose across mammary epithelial cells for milk synthesis.

The thermal decomposition behavior of composite modified double-base propellant containing hexanitrohexaazaisowurtzitane (CL-20/CMDB propellant) was studied by microcalorimetry. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The effect of different proportion of CL-20 to the thermal decomposition behavior, kinetics, and thermal hazard was investigated at the same time. The critical temperature of thermal explosion (T b), the self acceleration decomposition temperature (T SADT), and the adiabatic decomposition temperature rise (ΔT ad) were calculated to evaluate the thermal hazard of the CL-20/CMDB propellant. It shows that the CMDB propellant with 38% CL-20 has relative lower values of E and lgA, and with 18% CL-20 has the highest potential hazard.

Ca(2+) is an important regulatory ion and alteration of mitochondrial Ca(2+) homeostasis can lead to cellular dysfunction and apoptosis. Ca(2+) is transported into respiring mitochondria via the Ca(2+) uniporter, which is known to be inhibited by Mg(2+). This uniporter-mediated mitochondrial Ca(2+) transport is also shown to be influenced by inorganic phosphate (Pi). Despite a large number of experimental studies, the kinetic mechanisms associated with the Mg(2+) inhibition and Pi regulation of the uniporter function are not well established. To gain a quantitative understanding of the effects of Mg(2+) and Pi on the uniporter function, we developed here a mathematical model based on known kinetic properties of the uniporter and presumed Mg(2+) inhibition and Pi regulation mechanisms. The model is extended from our previous model of the uniporter that is based on a multistate catalytic binding and interconversion mechanism and Eyring's free energy barrier theory for interconversion. The model satisfactorily describes a wide variety of experimental data sets on the kinetics of mitochondrial Ca(2+) uptake. The model also appropriately depicts the inhibitory effect of Mg(2+) on the uniporter function, in which Ca(2+) uptake is hyperbolic in the absence of Mg(2+) and sigmoid in the presence of Mg(2+). The model suggests a mixed-type inhibition mechanism for Mg(2+) inhibition of the uniporter function. This model is critical for building mechanistic models of mitochondrial bioenergetics and Ca(2+) handling to understand the mechanisms by which Ca(2+) mediates signaling pathways and modulates energy metabolism.

The high-pressure thermal properties and their correlation with burning rates of the composite modified double base (CMDB) propellants containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz), a substitute of hexogen (RDX), were investigated using the high-pressure differential scanning calorimetry (PDSC). The results show that there is a main exothermal decomposition process with the heating of each propellant. High pressure can restrain the volatilization of NG, accelerate the main decomposition reaction, and make the reaction occur easily. High pressure can change the main decomposition reaction mechanism function and kinetics, and the control process obeys the rule of Avrami–Erofeev equation at high pressure and chemical reaction at normal pressure. However, the mechanism function can not be changed by the ballistic modifier. The correlation between PDSC characteristic values and burning rates was carried out and found that u and $$ \left( {p \, \Updelta H_{\text{d}} { / }\Updelta T} \right)^{ 1 / 2} $$ keep a good linear relation, k u keeps a similar changing trend with u, and it can be used to study the effect of the ballistic modifier or the other component on the burning rates.

NADH-ubiquinone oxidoreductase (Complex I, European Commission No. 1.6.5.3) is one of the respiratory complexes that generate the proton-motive force required for the synthesis of ATP in mitochondria. The catalytic mechanism of Complex I has not been well understood, due to the complicated structure of this enzyme. Here, we develop a kinetic model for Complex I that accounts for electron transfer from NADH to ubiquinone through protein-bound prosthetic groups, which is coupled to the translocation of protons across the inner mitochondrial membrane. The model is derived based on the tri-bi enzyme mechanism combined with a simple model of the conformational changes associated with proton transport. To study the catalytic mechanism, parameter values are estimated by analyzing kinetic data. The model is further validated by independent data sets from additional experiments, effectively explaining the effect of pH on enzyme activity. Results imply that matrix pH significantly affects the enzyme turnover processes. The overall kinetic analysis demonstrates a hybrid ping-pong rapid-equilibrium random bi-bi mechanism, consolidating the characteristics from previously reported kinetic mechanisms and data.

A novel high energy material, 1-amino-1-methylamino-2,2-dinitroethlyene (AMFOX-7), was synthesized by the reaction of 1,1-diamino-2,2-dinitroethylene (FOX-7) and methylamine aqueous solution in N-methyl pyrrolidone at 80 °C. The thermal behavior and non-isothermal decomposition kinetics of AMFOX-7 were studied with DSC and TG/DTG methods. The kinetic equation of thermal decomposition reaction can be expressed as: x 10 5 /RT). The critical temperature of thermal explosion of AMFOX-7 is 244.89 °C. The specific heat capacity of AMFOX-7 was determined with micro-DSC method and theoretical calculation method, and the standard molar specific heat capacity is 199.39 J·mol -1 ·K -1 at 298.15 K. Adiabatic time-to-explosion of AMFOX-7 was also calculated to be 215.41 s. AMFOX-7 has higher thermal stability than FOX-7.

Ca2+ transport through mitochondrial Ca2+ uniporter is the primary Ca2+ uptake mechanism in respiring mitochondria. Thus, the uniporter plays a key role in regulating mitochondrial Ca2+. Despite the importance of mitochondrial Ca2+ to metabolic regulation and mitochondrial function, and to cell physiology and pathophysiology, the structure and composition of the uniporter functional unit and kinetic mechanisms associated with Ca2+ transport into mitochondria are still not well understood. In this study, based on available experimental data on the kinetics of Ca2+ transport via the uniporter, a mechanistic kinetic model of the uniporter is introduced. The model is thermodynamically balanced and satisfactorily describes a large number of independent data sets in the literature on initial or pseudo-steady-state influx rates of Ca2+ via the uniporter measured under a wide range of experimental conditions. The model is derived assuming a multi-state catalytic binding and Eyring's free-energy barrier theory-based transformation mechanisms associated with the carrier-mediated facilitated transport and electrodiffusion. The model is a great improvement over the previous theoretical models of mitochondrial Ca2+ uniporter in the literature in that it is thermodynamically balanced and matches a large number of independently published data sets on mitochondrial Ca2+ uptake. This theoretical model will be critical in developing mechanistic, integrated models of mitochondrial Ca2+ handling and bioenergetics which can be helpful in understanding the mechanisms by which Ca2+ plays a role in mediating signaling pathways and modulating mitochondrial energy metabolism.

Glucose is the primary precursor for the synthesis of lactose, which controls milk volume by maintaining the osmolarity of milk. Glucose uptake in the mammary gland plays a key role in milk production. Glucose transport across the plasma membranes of mammalian cells is carried out by 2 distinct processes: facilitative transport, mediated by a family of facilitative glucose transporters (GLUT); and sodium-dependent transport, mediated by the Na+/glucose cotransporters (SGLT). Transport kinetic studies indicate that glucose transport across the plasma membrane of the lactating bovine mammary epithelial cell has a K(m) value of 8.29 mM for 3-O-methyl-D-glucose and can be inhibited by both cytochalasin-B and phloretin, indicating a facilitative transport process. This is consistent with the observation that in the lactating bovine mammary gland, GLUT1 is the predominant glucose transporter. However, the bovine lactating mammary gland also expresses GLUT3, GLUT4, GLUT5, GLUT8, GLUT12, and sodium-dependent SGLT1 and SGLT2 at different levels. Studies of protein expression and cellular and subcellular localizations of these transporters are needed to address their physiological functions in the mammary gland. From late pregnancy to early lactation, expression of GLUT1, GLUT8, GLUT12, SGLT1, and SGLT2 mRNA increases from at least 5-fold to several hundred-fold, suggesting that these transporters may be regulated by lactogenic hormones and have roles in milk synthesis. The GLUT1 protein is detected in lactating mammary epithelial cells. Its expression level decreases from early to late lactation stages and becomes barely detectable in the nonlactating gland. Both GLUT1 mRNA and protein levels in the lactating mammary gland are not significantly affected by exogenous bovine growth hormone, and, in addition, GLUT1 mRNA does not appear to be affected by leptin.

Using a multi-temperature artificial ageing testing apparatus and a standard method of determining the effective centralite/stabilizer content, the effective centralite/stabilizer content for varying time period in propellants heated at 95 degrees C, 90 degrees C, 85 degrees C, 75 degrees C and 65 degrees C was measured. Bethelot's equation and Semenov's equation in the temperature range of 65-95 degrees C for 81 propellants were established. The safe storage life at 30 degrees C, kinetic parameters [the apparent activation energy (E) and the pre-exponential constant (A)] and isolife temperatures obtained from the established equations and the activation energy (E(alpha=0.5)) obtained by integral isoconversional non-linear method for 81 propellants: single-base gun propellants (DF-01-DF-16), double-base gun propellants (SF-01-SF-13), tri-base gun propellants (SG-01-SG-02), nitramine gun propellants (GSF-01-GSF-18), double-base propellants (ST-01-ST-13), and composite modified double-base propellants (GST-01-GST-19), were given. Information was obtained on the effective centralite/stabilizer consumption reaction and the kinetic compensation effect.

The competitive reactions of reducing sugar production and degradation in the subcritical water hydrolysis of rice straw were investigated to optimise reducing sugar yield. The optimised conditions (280°C, 20 MPa, rice straw concentration of 5 wt.% and agitation speed of 200 rpm) resulted in a reducing sugar yield of 0.346 g/g rice straw because of the enhanced reducing sugar production and decreased sugar degradation. The sugar yield increased when the temperature increased from 250°C to 280°C, but it decreased when the temperature further increased to 300°C because of the degradation of monosaccharides (e.g. glucose and xylose) into by-products (e.g. 2-methyltetrahydrofuran and acetic acid). A first-order reaction model was developed to elucidate the competitive reaction kinetics of sugar production and degradation at various temperatures. The highest reducing sugar yield based on the model was achieved at 280°C with the highest production and lowest degradation rates.

Acetic acid (AcH) pretreatment of sugarcane bagasse with the catalysis of sulfuric acid (SA) could greatly enhance the enzymatic digestibility of cellulose. However, polysaccharide dissolution happened inevitably during the pretreatment. It was found that the simplest model, which assumes that the total polysaccharides were reactive to be dissolved, could not well describe the kinetic behavior of polysaccharide dissolution. A novel pseudo-homogenous kinetic model was thus developed by introducing a parameter termed as "potential dissolution degree" (δ(d)) based on the multilayered structure of cell wall. It was found that solid xylan and glucan dissolutions were a first-order reaction with respect to the dissolvable fraction. Due to the delignification action of AcH, polysaccharide dissolutions were enhanced in AcH media compared with those in aqueous system. Acetylizations of cellulose and sugars were also observed, and AcH concentration showed a significant influence on the degree of acetylization.

Caenorhabditis elegans (C. elegans) is an attractive animal model for biological and biomedical research because it permits relatively easy genetic dissection of cellular pathways, including insulin/IGF-like signaling (IIS), that are conserved in mammalian cells. To explore C. elegans as a model system to study the regulation of the facilitative glucose transporter (GLUT), we have characterized the GLUT gene homologues in C. elegans: fgt-1, R09B5.11, C35A11.4, F53H8.3, F48E3.2, F13B12.2, Y61A9LA.1, K08F9.1 and Y37A1A.3. The exogenous expression of these gene products in Xenopus oocytes showed transport activity to unmetabolized glucose analogue 2-deoxy-D-glucose only in FGT-1. The FGT-1-mediated transport activity was inhibited by the specific GLUT inhibitor phloretin and exhibited a Michaelis constant (K m) of 2.8 mM. Mannose, galactose, and fructose were able to inhibit FGT-1-mediated 2-deoxy-D-glucose uptake (P < 0.01), indicating that FGT-1 is also able to transport these hexose sugars. A GFP fusion protein of FGT-1 was observed only on the basolateral membrane of digestive tract epithelia in C. elegans, but not in other tissues. FGT-1::eGFP expression was observed from early embryonic stages. The knockdown or mutation of fgt-1 resulted in increased fat staining in both wild-type and daf-2 (mammalian insulin receptor homologue) mutant animals. Other common phenotypes of IIS mutant animals, including dauer formation and brood size reduction, were not affected by fgt-1 knockdown in wild-type or daf-2 mutants. Our results indicated that in C. elegans, FGT-1 is mainly a mammalian GLUT2-like intestinal glucose transporter and is involved in lipid metabolism.

Background Mitochondrial 2-oxoglutarate (α-ketoglutarate) dehydrogenase complex (OGDHC), a key regulatory point of tricarboxylic acid (TCA) cycle, plays vital roles in multiple pathways of energy metabolism and biosynthesis. The catalytic mechanism and allosteric regulation of this large enzyme complex are not fully understood. Here computer simulation is used to test possible catalytic mechanisms and mechanisms of allosteric regulation of the enzyme by nucleotides (ATP, ADP), pH, and metal ion cofactors (Ca2+ and Mg2+). Results A model was developed based on an ordered ter-ter enzyme kinetic mechanism combined with con-formational changes that involve rotation of one lipoic acid between three catalytic sites inside the enzyme complex. The model was parameterized using a large number of kinetic data sets on the activity of OGDHC, and validated by comparison of model predictions to independent data. Conclusions The developed model suggests a hybrid rapid-equilibrium ping-pong random mechanism for the kinetics of OGDHC, consistent with previously reported mechanisms, and accurately describes the experimentally observed regulatory effects of cofactors on the OGDHC activity. This analysis provides a single consistent theoretical explanation for a number of apparently contradictory results on the roles of phosphorylation potential, NAD (H) oxidation-reduction state ratio, as well as the regulatory effects of metal ions on ODGHC function.

A database of thermodynamic properties is developed, which extends a previous database of glycolysis and tricarboxylic acid cycle by adding the reactions of the pentose phosphate pathway. The raw data and documented estimations of solution properties are made electronically available. The database is determined by estimation of a set of parameters representing species-level free energies of formation. The resulting calculations provide thermodynamic and network-based estimates of thermodynamic properties for six reactions of the pentose phosphate pathway for which estimates are not available in the preexisting literature. Optimized results are made available in ThermoML format. Because calculations depend on estimated hydrogen and metal cation dissociation constants, an uncertainty and sensitivity analysis is performed, revealing 23 critical dissociation constants to which the computed thermodynamic properties are particularly sensitive. DATABASE URL: http://www.biocoda.org/thermo