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1.
FENG Juan WANG Qian ZHANG Xujia HUANG Youguo Al Xicheng ZHANG Xingkang & ZHANG JianpingState Key Laboratory for Structural Chemistry of Unstable Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing China National Laboratory of Biomacromolecules Institute of Biophysics Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2004,47(1)
The LH2 complex from Rhodopsudomonas (Rps.) palustris is unique in the heterogeneous carotenoid compositions. The dynamics of triplet excited state Carotenoids (3Car*) has been investigated by means of sub-microsecond time-resolved absorption spectroscopy both at physiological temperature (295 K) and at cryogenic temperature (77 K). Broad and asymmetric Tn←T-1 transient absorption was observed at room temperature following the photo-excitation of Car at 532 nm, which suggests the contribution from various carotenoid compositions having different numbers of conjugated C=C double bonds (Nc=c). The triplet absorption bands of different carotenoids, which superimposed at room temperature, could be clearly distinguished upon decreasing the temperature down to 77 K. At room temperature the shorter-wavelength side of the main Tn←T1 absorption band decayed rapidly to reach a spectral equilibration with a characteristic time constant of-1 μs, the same spectral dynamics, however, was not observed at 77 K. The 相似文献
2.
Thermochromatium (Tch.) tepidum是一种中等嗜热的紫色光合细菌, 最佳生长温度为48-50 ℃; 其捕光天线复合物2 (LH2)含有非均一性脱辅基蛋白和类胡萝卜素(Car), 且高分辨率晶体结构未知. 我们通过超快光谱研究了分别采用去垢剂n-dodecyl-β-D-maltoside (DDM)和lauryldimethylamine oxide (LDAO)制备的LH2的激发态动力学, 观测到由细菌叶绿素(BChl)的Qy态介导的B800-to-B850单重态能量传递过程(时间尺度~1.2 ps, 用DDM制备的LH2), 以及由类胡萝卜素S2态介导的Car-to-Car和Car-to-BChl 单重态能量传递过程(~100 fs). 结果表明C=C共轭双键数目(NC=C)为11和12的两类Car共处于同一LH2复合物中; 相对于源自其它菌种、构成组分相对简单的LH2, Tch. tepidum的LH2中B800-B850的相对取向有较大差异. 本工作发现LH2中低含量类胡萝卜素组分anhydrorhodovibrin (NC=C=12)起着高效“能量陷阱”的作用, 可能是一种重要的光保护机制; 基于类胡萝卜素的超快谱带位移现象提出(OH-)spirilloxanthin(NC=C=13)距BChl分子可能比其它类胡萝卜素更近. 这些研究结果有助于进一步理解苛刻自然条件下生长的Tch. tepidum的捕光和光保护机制. 相似文献
3.
K.Razi Naqvi T.B Melø B.Bangar Raju Tamás Jávorfi Ilian Simidjiev Gyözö Garab 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2659-2667
Laser-induced changes in the absorption spectra of isolated light-harvesting chlorophyll a/b complex (LHC II) associated with photosystem II of higher plants have been recorded under anaerobic conditions and at ambient temperature by using multichannel detection with sub-microsecond time resolution. Difference spectra (ΔA) of LHC II aggregates have been found to differ from the corresponding spectra of trimers on two counts: (i) in the aggregates, the carotenoid (Car) triplet–triplet absorption band (ΔA>0) is red-shifted and broader; and (ii) the features attributable to the perturbation of the Qy band of a chlorophyll a (Chla) by a nearby Car triplet are more pronounced, than in trimers. Aggregation, which is known to be accompanied by a reduction in the fluorescence yield of Chla, is shown to cause a parallel decline in the triplet formation yield of Chla; on the other hand, the efficiency (100%) of Chla-to-Car transfer of triplet energy and the lifetime (9.3 μs) of Car triplets are not affected by aggregation. These findings are rationalized by postulating that the antenna Cars transact, besides light-harvesting and photoprotection, a third process: energy dissipation within the antenna. The suggestion is advanced that luteins, which are buried inside the LHC II monomers, as well as the other, peripheral, xanthophylls (neoxanthin and violaxanthin) quench the excited singlet state of Chla by catalyzing internal conversion, a decay channel that competes with fluorescence and intersystem crossing; support for this explanation is presented by recalling reports of similar behaviour in bichromophoric model compounds in which one moiety is a Car and the other a porphyrin or a pyropheophorbide. 相似文献
4.
Marta Worzakowska 《Journal of Thermal Analysis and Calorimetry》2010,100(2):685-693
A series of N-alkyl-N-alkyl′-pyrrolidinium-bis(trifluoromethanesulfonyl) imide (TFSI−) room temperature ionic liquids (RTILs) has been investigated by means of thermogravimetric analysis (TG), differential scanning
calorimetry, FT-IR spectroscopy, and X-ray diffraction analysis. These compounds exhibit a thermal stability up to 548–573 K.
The mass loss starting temperature, T
ml, falls in a narrow range of temperatures: 578–594 K. FT-IR spectra, performed before and after 24 h isothermal experiments
at 553 and 573 K, have confirmed their great thermal stability. Below the ambient temperature, these compounds exhibit a complex
behavior. N-methyl-N-propyl-pyrrolidinium-TFSI is the sole liquid which crystallizes without forming any amorphous phase even after quenching
in liquid nitrogen. Its crystalline phase has a melting point, T
m, of 283 ± 1 K. When the amorphous solid is heated, the N-butyl-N-ethyl-pyrrolidinium-TFSI presents a glass transition temperature, T
g, at 186 K followed by a cold crystallization, T
cc, at 225 K, and a final T
m at 262 K. The N-butyl-N-methyl-pyrrolidinium-TFSI exhibits a T
g between 186 and 181 K, its cold crystallization leading to two different solid phases. Solid phase I has a melting point
T
I,m = 252 K and phase II, T
II,m = 262 K. When the amorphous phase is obtained at a cooling rate of 10 K/min, its T
cc is 204 K, and a metastable solid phase (III) is obtained which transforms into the phase II at 226 K. However, when the sample
is quenched, the amorphous phase transforms into phase II at T
cc = 217 K and phase I at 239 K. P15-TFSI exhibits the most complicated pattern as, on cooling, it leads to both a crystallized phase at 237 K and an amorphous
phase at 191 K. On heating, after a T
g at 186 K and a T
cc at 217 K, two solid–solid phase transitions are observed at 239 K and 270 K, the final T
m being 279 K. 相似文献
5.
The data on the solubility of helium in water and aqueous solutions of sodium chloride at a temperature of T = 293–353 K and a He partial pressure of p
2 = 0.1–20 MPa are used to calculate the standard parameters of the Sechenov salt effect and estimate, within the formalism
of the McMillan-Mayer theory, the parameters of the pairwise solute-solute interaction. 相似文献
6.
G. V. Girichev V. V. Rybkin V. V. Tyunina A. V. Krasnov N. V. Tverdova N. P. Kuz’mina I. G. Zaitseva 《Russian Journal of Inorganic Chemistry》2011,56(1):99-103
A mass spectrometric study of the saturated vapor over ytterbium tris(hexafluoroacetylacetonate) Yb(hfa)3 (hfa = CF3-C(O)-CH-C(O)-CF3) and of the vapor overheated up to the thermal decomposition temperature of the complex is presented. The vapor composition
changes markedly with increasing temperature. At T ≈ 370 K, the mass spectrum of the vapor over Yb(hfa)3 indicates the presence of ions containing one to three metal atoms. As the temperature is raised, the ion currents due to
oligomer ions decrease. The oligomers are not detected at T > 440 K. The total decomposition temperature of Yb(hfa)3 is 663(9) K. The second-law enthalpy of sublimation (ΔH
so (380 K)) is 134 ± 7 kJ/mol for the monomer and 138 ± 10 kJ/mol for the dimer. The enthalpy of dissociation of the dimer into
monomer molecules is nearly equal to the enthalpy of sublimation of the monomer and dimer: ΔH
dis(380 K) = 130 ± 15 kJ/mol. 相似文献
7.
V. N. Smirnov 《Kinetics and Catalysis》2011,52(2):166-169
The results of our experimental studies and an analysis of the published data on the rate constant for the reaction Fe + O2 = FeO + O in the forward (I) and reverse (−I) direction are reported. The data obtained in this work are described by the
expressions k
1 = 6.2 × 1014exp(−11100 K/T) cm3 mol−1 s−1 and k
−1 = 6.0 × 1013exp(−588 K/T) cm3 mol−1 s−1 (T = 1500–2500 K). The generalized expressions for the temperature dependences of these rate constants derived by combining
our results with the literature data can be presented as k
1 = 9.4 × 1014(T/1000)0.022exp(−11224 K/T) cm3 mol−1 s−1 (T = 1500–2500 K) and k
−1 = 1.8 × 1014(1000/T)0.37exp(−367 K/T) cm3 mol−1 s−1 (T = 200–2500 K). 相似文献
8.
One new metal – organic coordination framework formulated as [{Cu(4,4′-bipy)(CH3COO)2}·3H2O]n (1) (where 4,4′-bipy=4,4′-bipyridine) has been hydrothermally synthesised and characterised by elemental analysis, IR and electronic
spectroscopy, variable temperature magnetic moment measurement and single crystal X-ray diffraction study. Single crystal
X-ray analysis reveals that 1 is one dimensional polymeric compound in which acetate ligand shows both mono- and bidentate bonding mode, and 4,4′-bipy
acts as bridging ligand which supports the formation of infinite chains. The global feature of the χ
M
T vs. T curve in 1 is characteristic of moderate antiferromagnetic interaction and the best fit parameters from 300 down to 2 K are found as
J = −78.7 cm−1. 相似文献
9.
N. N. Smirnova Yu. A. Zakharova V. A. Ruchenin O. G. Zamyshlyayeva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(4):539-547
The temperature dependence of the heat capacity of cross-linked and branched (co)polymers based on tris- and bis-(pentafluorophenyl)germanes is studied in the temperature range of 6–7 to 535–570 K, using adiabatic vacuum and differential
scanning calorimeters. In the indicated temperature range, physical transformations are revealed and their thermodynamic characteristics
are determined. The obtained experimental data are used to calculate the thermodynamic functions of (co)polymers: C
p
/°, H°(T) - H°(0), S°(T) - S°(0), and G°(T) - H°(0) in the range of T → 0 to 535 K for the branched (co)polymer and from T → 0 to 500 K for the cross-linked polymer. Their standard entropies of formation are determined at 298.15 K. The obtained
results are compared with analogous data for hyperbranched perfluorinated polyphenylenegermane studied earlier. The effect
of the structure of polyphenylenegermanes on their thermodynamic properties is analyzed. 相似文献
10.
The heat capacities of N-(tert-butoxycarbonyl)-l-phenylalanine (abbreviated to NTBLP in this article), as an important chemical intermediates used to synthesize proteins
and polypeptides, were measured by means of a fully automated adiabatic calorimeter over the temperature range from 78 to
350 K. The measured experimental heat capacities were fitted to a polynomial equation as a function of temperature. The thermodynamic
functions, H
T − H
298.15K and S
T − S
298.15K, were calculated based on the heat capacity polynomial equation in the temperature range of (80–350 K) with an interval of
5 K. The thermal stability of the compound was further studied using TG and DSC analyses; a possible mechanism for thermal
decomposition of the compound was suggested. 相似文献
11.
Ju-Lan Zeng Sai-Bo Yu Bo Tong Li-Xian Sun Zhi-Cheng Tan Zhong Cao Dao-Wu Yang Jing-Nan Zhang 《Journal of Thermal Analysis and Calorimetry》2011,103(3):1087-1093
An N-tert-butyloxycarbonylated organic synthesis intermediate, (S)-tert-butyl 1-phenylethylcarbamate, was prepared and investigated by means of differential scanning calorimetry (DSC) and thermogravimetry
(TG). The molar heat capacities of (S)-tert-butyl 1-phenylethylcarbamate were precisely determined by means of adiabatic calorimetry over the temperature range of 80-380 K.
There was a solid–liquid phase transition exhibited during the heating process with the melting point of 359.53 K. The molar
enthalpy and entropy of this transition were determined to be 29.73 kJ mol−1 and 82.68 J K−1 mol−1 based on the experimental C
p–T curve, respectively. The thermodynamic functions, [HT0 - H298.150 H_{T}^{0} - H_{298.15}^{0} ] and [ST0 - S298.150 S_{T}^{0} - S_{298.15}^{0} ], were calculated from the heat capacity data in the temperature range of 80–380 K with an interval of 5 K. TG experiment
showed that the pyrolysis of the compound was started at the temperature of 385 K and terminated at 510 K within one step. 相似文献
12.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
13.
J. Leitner M. Hampl K. Růžička M. Straka D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2008,91(3):985-990
The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature
dependence of the molar heat capacity in the form C
pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T
2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy
at 298.15 K S
m0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf
H
0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional
theory. 相似文献
14.
L. E. Agafonova A. I. Druzhinina R. M. Varushchenko O. V. Polyakova 《Moscow University Chemistry Bulletin》2010,65(5):285-294
The heat capacity, thermodynamic properties of fusion, and purity of the ethyl ester of butanoic acid were determined by adiabatic
calorimetry in the temperature range from 8 to 372 K. The pT-parameters of the ester for the equilibrium liquid-vapor were measured by comparative ebulliometry in the “atmospheric” range
of pressure from 10.8 to 101.7 kPa. The obtained data were used to derive the normal boiling temperature (T
n.b), the enthalpies of vaporization at T = 298.15 K and T
n.b, and the main thermodynamic functions (changes of S, H, G) in the crystal and liquid states of the temperature interval studied and in the ideal gas state at T = 298.15 K. The experimental vapor pressures of the narrow temperature interval, ΔT = 62 K were extended to the entire range of the liquid, T
cr − T
tp0 = 394.3 K, from the triple, T
tp0, to the critical, T
cr, temperatures. 相似文献
15.
Z. H. Zhang Z. C. Tan Y. S. Li L. X. Sun 《Journal of Thermal Analysis and Calorimetry》2006,85(3):551-557
The molar heat capacities of the room temperature
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)
were measured by an adiabatic calorimeter in temperature range from 80 to
390 K. The dependence of the molar heat capacity on temperature is given as
a function of the reduced temperature X
by polynomial equations, C
P,m
(J K–1 mol–1)=
195.55+47.230 X–3.1533 X
2+4.0733 X
3+3.9126 X
4 [X=(T–125.5)/45.5] for the solid phase (80~171
K), and C
P,m (J
K–1 mol–1)=
378.62+43.929 X+16.456 X
2–4.6684 X
3–5.5876 X
4 [X=(T–285.5)/104.5] for the liquid phase (181~390
K), respectively. According to the polynomial equations and thermodynamic
relationship, the values of thermodynamic function of the BMIBF4
relative to 298.15 K were calculated in temperature range from 80 to 390 K
with an interval of 5 K. The glass translation of BMIBF4
was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar
enthalpy of combustion of BMIBF4 was determined to
be Δc
H
m
o=
– 5335±17 kJ mol–1. The standard
molar enthalpy of formation of BMIBF4 was evaluated
to be Δf
H
m
o=
–1221.8±4.0 kJ mol–1 at T=298.150±0.001 K. 相似文献
16.
A. V. Markin N. N. Smirnova I. E. Boronina V. A. Ruchenin A. G. Lyapin 《Russian Chemical Bulletin》2008,57(9):1975-1980
Temperature dependences of the heat capacities of disordered graphite-like nanostructures prepared by the thermobaric treatment
of fullerite C60 (p = 2 and 8 GPa, T = 1373 K) were measured in the temperature ranges from 7 to 360 K in an adiabatic vacuum calorimeter and from 330 to 650
K in a differential scanning calorimeter. At T < 50 K, the dependences obtained were analyzed using the Debye theory of the heat capacity of solids and its multifractal
version. The fractal dimensions D were determined and some conclusions on the heterodynamic character of the structures studied were made. The thermodynamic
functions C
p
o
T), H
o(T) − H
o(0), S
o(T) − S
o(0), and G
o(T) − H
o(0) were calculated in the temperature range from T → 0 to 610 (650) K. The thermodynamic properties of the graphite-like nanostructures studied and some carbon allotropes were
compared. The standard entropies of formation Δf
S
o of the graphite nanostructures studied and diamond were calculated along with the standard entropies of the reactions of
their synthesis from the face-centered cubic phase of fullerite C60 and their interconversions at T = 298.15 K.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1940–1945, September, 2008. 相似文献
17.
Densities of solutions of tetramethyl-bis-urea (TMbU) or “Mebicarum” in H2O and D2O, with solute mole fraction concentrations (x
2) ranging up to 3.2 × 10−3, have been measured at 288.15, 298.15, 308.15 and 318.15 K using a precision vibrating-tube densimeter. The limiting apparent
molar volumes, V
φ,2
∞, and expansibilities, E
p, φ, 2
∞, of the solute have been calculated. The isotope effect δ V
φ,2
∞(H2O → D2O;T) is negative, monotonously decreases in magnitude with temperature and reverses sign at T ≈ 318 K. Water (H2O, D2O) and TMbU molecules in infinitely- and highly-dilute aqueous solutions form H(D)-bonded hydration complexes with a high packing density.
The hydration of TMbU should be treated as a superposition of two mechanisms, hydrophobic and hydrophilic, with the latter one predominating. 相似文献
18.
A. V. Markin I. A. Letyanina N. N. Smirnova V. V. Sharutin O. V. Molokova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(8):1315-1321
The temperature dependence of heat capacity C
p
° = f(T) of triphenylantimony bis(acetophenoneoximate) Ph3Sb(ONCPhMe)2 was measured for the first time in an adiabatic vacuum calorimeter in the range of 6.5–370 K and a differential scanning
calorimeter in the range of 350–463 K. The temperature, enthalpy, and entropy of fusion were determined. Treatment of low-temperature
(20 K ≤ T ≤ 50 K) heat capacity was performed on the basis of Debye’s theory of the heat capacity of solids and its multifractal model
and, as a consequence, a conclusion was drawn on the type of structure topology. Standard thermodynamic functions C
p
°(T), H°(T) — H°(0), S°(T), and G°(T) — H°(0) were calculated according to the experimental data obtained for the compound mentioned in the crystalline and liquid
states for the range of T → 0–460 K. The standard entropy of the formation of crystalline Ph3Sb(ONCPhMe)2 was determined at T = 298.15 K. 相似文献
19.
M. A. V. Ribeiro da Silva Cláudia P. F. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(1):21-25
The standard (p
0=0.1
MPa) molar enthalpy of formation, Δf
H
0
m, for crystalline N-phenylphthalimide
was derived from its standard molar enthalpy of combustion, in oxygen, at
the temperature 298.15 K, measured by static bomb-combustion calorimetry,
as –206.0±3.4 kJ mol–1. The
standard molar enthalpy of sublimation, Δg
cr
H
0
m
, at T=298.15 K, was derived, from high
temperature Calvet microcalorimetry, as 121.3±1.0 kJ mol–1.
The derived standard molar enthalpy of formation, in the gaseous state,
is analysed in terms of enthalpic increments and interpreted in terms of molecular
structure. 相似文献
20.
A. Migdał-Mikuli N. Górska E. Szostak 《Journal of Thermal Analysis and Calorimetry》2007,90(1):223-228
Phase transition and thermal decomposition of hexadimethylsulfoxidealuminium chloride were studied by differential scanning
calorimetry (DSC), thermogravimetry (TG) and simultaneous differential thermal analysis (SDTA). The gaseous products of the
decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In the temperature range of 95–300 K, [Al(DMSO)6]Cl3 indicates one phase transition at T
ch=244.96 K (on heating) and at T
cc=220.87 K (on cooling). Large thermal hysteresis of the phase transition (∼24 K) indicates its first order character. Large
value of transition entropy (ΔS≈40 J mol−1 K−1) suggests its configurational character. Thermal decomposition of the title compound proceeds in four main stages. In the
first stage, which starts just above ca. 300 K, the compound loses two DMSO molecules per one formula unit and undergoes into
[Al(DMSO)4]Cl3. In the second stage, the next three DMSO ligands are released and simultaneously decomposed. The third stage, which continues
up to ca. 552 K, is connected with a loss of the last DMSO ligand and the formation of AlCl3. In the fourth stage AlCl3 reacts with carbon monoxide that originates from the decomposition of DMSO, and first aluminium oxychloride and next solid
Al2O3 plus carbon are created. 相似文献