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Endothermic reactions

Kate L Henderson, Mingjie Li, Salette Martinez, Edwin A Lewis, Robert P Hausinger, Joseph P Emerson
BACKGROUND: TauD is a nonheme iron(II) and α-ketoglutarate (αKG) dependent dioxygenase, and a member of a broader family of enzymes that oxidatively decarboxylate αKG to succinate and carbon dioxide thereby activating O2 to perform a range of oxidation reactions. However before O2 activation can occur, these enzymes bind both substrate and cofactor in an effective manner. Here the thermodynamics associated with substrate and cofactor binding to FeTauD are explored. METHODS: Thermal denaturation of TauD and its enzyme-taurine, enzyme-αKG, and enzyme-taurine-αKG complexes are explored using circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC)...
February 15, 2017: Biochimica et Biophysica Acta
M A Ahmed, A A Brick, A A Mohamed
A new approach for removal of indigo carmine blue (IC) dye which is extensively used in jeans manufacture was successfully performed on novel mesoporous [LDH] nanoparticles prepared by sol-gel route using CTAB as shape and pore directing agent. The physicochemical features were monitored by X-ray diffraction (XRD), Fourier transformer infra-red (FTIR), N2 adsorption-desorption isotherm, Field emission electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). The influence of reaction parameters affecting dye adsorption including contact time, initial dye concentration, pH and temperature were investigated...
February 2, 2017: Chemosphere
Jaruwan Siritapetawee, Chutima Talabnin, Jarunee Vanichtanankul, Chomphunuch Songsiriritthigul, Kanjana Thumanu, Chun-Jung Chen, Nantarat Komanasin
In this study, the binding of a glycosylated serine protease (EuP-82) with human fibrinogen was investigated by the isothermal titration calorimetry (ITC). The ITC analysis indicated that the binding of EuP-82 to fibrinogen in the conditions with or without the activator (Ca(2+) ) was an exothermic reaction (dominant negative enthalpy), which tended to be driven by hydrogen bonding and van der Waals interactions. In contrast, the binding of fibrinogen-EuP-82 in the condition with the inhibitor (Zn(2+) ) was an unfavorable endothermic reaction...
February 1, 2017: Biotechnology and Applied Biochemistry
Weston Thatcher Borden
Thermochemical data are used to show that, of the 89.9 kcal/mol difference between the endothermicity of H2 addition to N2 (ΔH = 47.9 kcal/mol) and the exothermicity of H2 addition to acetylene (ΔH = -42.0 kcal/mol), less than half is due to a stronger π bond in N2 than in acetylene. The other major contributor to the difference of 89.9 kcal/mol between the enthalpies of hydrogenation of N2 and acetylene is that the pair of N-H bonds that are created in the addition of H2 to N2 are significantly weaker than the pair of C-H bonds that are created in the addition of H2 to acetylene...
February 9, 2017: Journal of Physical Chemistry. A
Graham Dawson, Wei Chen, Luhua Lu, Kai Dai
The adsorption properties of two nanomorphologies of trititanate, nanotubes (TiNT) and plates (TiNP), prepared by the hydrothermal reaction of concentrated NaOH with different phases of TiO2, were examined. It was found that the capacity for both morphologies towards methylene blue (MB), an ideal pollutant, was extremely high, with the TiNP having a capacity of 130 mg/g, higher than the TiNT, whose capacity was 120 mg/g at 10 mg/L MB concentration. At capacity, the well-dispersed powders deposit on the floor of the reaction vessel...
January 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Man Wang, Gang Li, Lihui Huang, Jing Xue, Quan Liu, Nan Bao, Ji Huang
Activated carbons were derived from Enteromorpha prolifera immersed in H3PO4 solution or the H3PO4 solution mixed with sodium benzenesulfonate (SBS), producing AC and AC-SBS. NaOH solution was employed in regeneration of ciprofloxacin (CIP)-loaded AC and AC-SBS to obtain RAC and RAC-SBS. The properties of the original and regenerated activated carbons were characterized by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption/desorption isotherms and Fourier transform infrared spectroscopy (FTIR)...
January 18, 2017: Ecotoxicology and Environmental Safety
Amartya Roy, Paromita Seal, Jyotirmoy Sikdar, Sanghamitra Banerjee, Rajen Haldar
Linezolid, one of the reserve antibiotic of oxazolidinone class has wide range of antimicrobial activity. Here we have conducted a fundamental study concerning the dynamics of its interaction with bovine serum albumin (BSA), and the post binding modification of the later by employing different spectroscopic (absorption, fluorescence and circular dichroism (CD) spectroscopy) and molecular docking tools. Gradual quenching of the tryptophan (Trp) fluorescence upon addition of linezolid to BSA confirms their interaction...
January 19, 2017: Journal of Biomolecular Structure & Dynamics
Laurean Ilies, Mayuko Isomura, Shin-Ichi Yamauchi, Tomoya Nakamura, Eiichi Nakamura
Upon zincation of two acidic protons attached to the nitrogen and the sp-carbon atoms, a N-protected 2-ethynylaniline cyclizes to a 2,3-dizincioindole at 120 °C. Driven by the energy gain due to formation of two C-Zn bonds, this reaction occurs smoothly without side reactions, although this transformation is intrinsically endothermic in its bare anionic form. The resulting dizinc intermediate can be functionalized with one or two different electrophiles either inter- or intramolecularly on either C(2) or C(3) selectively, depending on the choice of catalyst and the electrophiles...
December 28, 2016: Journal of the American Chemical Society
Bholanath Maity, Debasis Koley
The effect of substituents in disilene mediated N2O activation was studied at the M06-2X/QZVP//ωB97xD/TZVP level of theory. The relationship between structural diversity and the corresponding reactivity of six disilenes (IA-F(t)) in the presence of four different substituents (-NMe2, -Cl, -Me, -SiMe3) is addressed in this investigation. We primarily propose two plausible mechanistic routes: Pathway I featuring disilene → silylene decomposition followed by N2O coordination and Pathway II constituting the N2O attack without Si-Si bond cleavage...
December 20, 2016: Journal of Physical Chemistry. A
Ahmad A Tolba, Said I Mohamady, Shimaa S Hussin, Takaya Akashi, Yuka Sakai, Ahmed A Galhoum, Eric Guibal
The grafting of amino and carboxylic acid groups on cellulose increased La(III) sorption efficiency of cellulose: maximum sorption capacity increased from 38mgLag(-1) for cellulose to 101 and 170mgLag(-1) for amino derivative (PAC) and amino-carboxylic derivative (PCMC). Langmuir equation successfully fits sorption isotherms while uptake kinetics are effectively modeled using the pseudo-first order rate equation (though resistance to intraparticle diffusion plays a significant role in the control of metal recovery)...
February 10, 2017: Carbohydrate Polymers
Qian Gan, Yongyu Qi, Yahong Xiong, Yinlian Fu, Xueyi Le
Two new mononuclear mixed ligand copper(II) complexes [Cu(PBO)(Gly-gly)(H2O)]·ClO4·1.5H2O (1) and [Cu(PBO)(Gly-L-leu)(H2O)]·ClO4 (2) (PBO is 2-(2'-pyridyl)benzoxazole, Gly-gly and Gly-L-leu are Glycyl-glycine anion and Glycyl-L-leucine anion, respectively), have been prepared and characterized by various analytical and spectral techniques. The interactions of the complexes with DNA were investigated using multi-spectroscopic methods (absorption, emission, circular dichroism), viscometry and electrochemical titration as well as molecular docking technique...
December 15, 2016: Journal of Fluorescence
Tahshina Begum, Manoj Mondal, Manash Protim Borpuzari, Rahul Kar, Golap Kalita, Pradip K Gogoi, Utpal Bora
A bis-N-heterocyclic carbene (NHC) functionalized with chloropropyltriethoxysilane over silica was used to synthesize a well-defined immobilized palladium complex. This complex is a suitable and easily retrievable catalyst for Suzuki-Miyaura cross-coupling reactions under mild aqueous conditions. Excellent yields and conversions were obtained with low palladium loadings (down to 0.03 mol% Pd). The catalyst can be reused up to six cycles without the loss of its activity. The catalytic role of the NHC complex of palladium during coupling between bromobenzene and phenylboronic acid was investigated theoretically...
January 3, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Fatih Gul, Ibrahim Y Orhan, Furkan S Ceylan, Nadir B Akdeniz, H Abdulkadir Karadag
PURPOSE: Temperature sensitivity is found in all multicelleular organisms, as well as in most primitive life forms. The ubiquity of this temperature sensitivity is an indicator of its effects at the multicellular, cellular and molecular levels [1]. Previous studies have shown that temperature-based regulation is present in the transcriptional process [2]. RNA Thermometers, temperature-sensitive sequences, have been shown to act on heat-shock genes to regulate temperature-dependant systems in many organisms [3,4]...
December 1, 2016: Clinical and Investigative Medicine. Médecine Clinique et Experimentale
JungSoo Kim, Richard M Cox, P B Armentrout
The kinetic-energy dependences of the reactions M(+) + CO where M(+) = Re(+), Os(+), and Ir(+) are studied using guided ion-beam tandem mass spectrometry. Formation of both MO(+) and MC(+) was observed in endothermic processes for all three metals. Modeling of the data provides thresholds that yield 0 K bond dissociation energies (BDEs, in eV) of 4.67 ± 0.09 (Re(+)-O), 4.82 ± 0.14 (Os(+)-O), 4.25 ± 0.11 (Ir(+)-O), 5.13 ± 0.12 (Re(+)-C), 6.14 ± 0.14 (Os(+)-C), and 6.58 ± 0.12 (Ir(+)-C). These BDEs agree well with literature values within experimental uncertainties demonstrating that ground state products are formed for all cases even though some of the reactions are formally spin forbidden...
November 21, 2016: Journal of Chemical Physics
Hao Zhang, Xing Zhou, Jian He, Tao Wang, Xiaohu Luo, Li Wang, Ren Wang, Zhengxing Chen
Recombinant amylosucrase from Neisseria polysaccharea was utilized to modify native and acid-thinned starches. The molecular structures and physicochemical properties of modified starches were investigated. Acid-thinned starch displayed much lower viscosity after gelatinization than did the native starch. However, the enzyme exhibited similar catalytic efficiency for both forms of starch. The modified starches had higher proportions of long (DP>33) and intermediate chains (DP 13-33), and X-ray diffraction showed a B-type crystalline structure for all modified starches...
April 1, 2017: Food Chemistry
Chao Liu, Huiyan Zhang, Rui Xiao, Shubin Wu
Thermogravimetric characteristics of chitin and chitosan and their potentials to produce value-added organonitrogen chemicals were separately evaluated via TG/DSC-FTIR and Py-GC/MS. Results shown that chitin had the better thermal stability and higher activation energy than chitosan because of the abundant acetamido group. Furthermore, the dominated volatilization in active pyrolysis of chitin contributed to its endothermic property, whereas the charring in chitosan led to the exothermal. During fast pyrolysis, the acetamido group in chitin and chitosan was converted into acetic acid or acetamide...
January 20, 2017: Carbohydrate Polymers
B B Xiao, X B Jiang, X L Yang, Q Jiang, F Zheng
Pt1ML/Pd3Al, which comprises a Pd3Al core protected by a Pt monolayer, may experience Al dealloying because of the strong affinity of Al toward O. To circumvent this issue, the Pt2ML/Os/Pd3Al catalyst has been designed to suppress the migration of Al by inserting an Os monolayer at the interface between the Pd3Al core and two Pt monolayers. On the basis of segregation energies, Al leaching from the core to the 1st layer is determined to be endothermic even under O coverage, indicating an energetic preference for Al to reside in the core structure...
October 25, 2016: Physical Chemistry Chemical Physics: PCCP
Maria Demireva, JungSoo Kim, P B Armentrout
Guided ion beam mass spectrometry (GIBMS) is used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal gadolinium cation (Gd(+)) with O2, CO2, and CO and for reactions of GdO(+) with CO, O2, and Xe. GdO(+) is formed through barrierless and exothermic processes in the reactions of Gd(+) with O2 and CO2. All other reactions observed are endothermic, and analyses of their kinetic energy dependent cross sections yield 0 K bond dissociation energies (BDEs) for GdO(+), GdC(+), and GdCO(+)...
October 21, 2016: Journal of Physical Chemistry. A
Xu Jiao, Yuvaraja Gutha, Weijiang Zhang
The utilization of CS/PVA/CuO as a novel adsorbent for the removal of Pb(II) from aqueous solution has been examined in a batch adsorption process with several experimental conditions including initial solution pH, dose, contact time, initial metal ion concentration, and temperature. The new and novel material was characterized by structural (XRD), spectral (FTIR), morphological with elemental (SEM with EDS), and size of the nanoparticles (TEM) analyses. The pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetics equations were used to analyze the kinetic data of the adsorption process and the data was fitted well with the pseudo-second-order kinetic model with R(2) values (close to the unity)...
January 1, 2017: Colloids and Surfaces. B, Biointerfaces
Peter Portius, Martin Davis
A convenient synthetic route to poly(tetrazolato) silicon complexes is described based on the four reactive centres of the N-rich, highly endothermic tetraazides of the type Si(N3)4(L2). Hypercoordinate azido(tetrazolato) silicon complexes Si(N3)2(N4C-R)2(L2), R = CH3, C6H5, 4-C6H4CH3 (4a, 5, 6, 7) and Si(N3)2(N4C-L)2 (9, L = 2-C5H4N), L2 = 2,2'-bipyridine, 1,10-phenanthroline, with SiN6 skeletons were synthesised via multiple [3 + 2] dipolar cycloaddition reactions starting from Si(N3)4(L2) and a nitrile. The isolated new complexes were characterised by standard analytical methods, single crystal X-ray diffraction and differential scanning calorimetry (4a,b)...
October 13, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
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