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31.
The available and total niacin evolution during maturation of yellow pea lupine (Lupinus luteus L., cv. Juno), pea (Pisum sativum L., cv. Ergo), faba bean (Vicia faba sp. minor Harz, cv. Tibo) and in germinated and high-pressure heated peas (Pisum sativum L., cv. Esla) have been determined by capillary electrophoresis (CE). The results have been compared with those obtained by high-performance liquid chromatography (HPLC). The values obtained by CE were similar to those obtained by HPLC. Maturation of seeds significantly reduced the available and total niacin content in legumes. The available/total niacin ratio during seed maturation depends on the type of legume. In faba beans and peas, a reduction was observed which was more pronounced in the case of peas. For lupine seeds, the ripening produced an increase (34%) in the available/total niacin ratio 50 days after flowering (DAF). Pea germination produced an overall increase in available and total niacin content although the available/total niacin ratio decreased. High pressure heating of pea yielded an increase in the available niacin content and available/total niacin ratio but the total niacin content did not change. 相似文献
32.
Ivan Gitsov Iliya Bl. Rashkov Ivan M. Panayotov Alexandr Golub 《Journal of polymer science. Part A, Polymer chemistry》1989,27(2):639-646
The copolymerization of ε-caprolactone (ε-CL) with octamethylcyclotetrasiloxane (D4) and styrene (St) under the action of the second-stage potassium graphitide KC24 was investigated. The copolymerizations were carried out in bulk or in xylene at 20°C. The content of the block copolymer ε-CL/D4 in the polymerization mixture was 60–95%, the molecular weight ranging between 150,000 and 300,000. The data for the copolymers' composition obtained by 1H-NMR and GPC showed 14–20% of D4-units in the copolymer. The amount of the block copolymer ε-CL/St in the polymerization products was 0–87%, and the molecular weights in the case of copolymer formation were between 100,000 and 500,000. The content of St-units in the copolymers was from 10 to 75% as shown by GPC and 1H-NMR. The mechanism of action of the initiator is discussed. 相似文献
33.
Michal Svr
ek Pavol Baacký Anton Zajac 《International journal of quantum chemistry》1992,43(3):415-423
An exact solution for the electron-vibrational problem of the nonadiabatic molecular system has been obtained. By the quasi-particle transformation technique, the fermionic Hamiltonian has been derived and solved at the ab initio level. Results clearly and unambiguously show that the gap formation due to nonadiabatic electron–phonon coupling is mediated by the one-particle electron–phonon interaction term, whereas the two-particle one represents just a correction to the correlation energy. The temperature dependence of the gap and electronic specific heat connected with the electron–phonon coupling have also been derived. 相似文献
34.
Two simple modification methods for ordered mesoporous silicas were examined and compared. MCM-41 molecular sieve was physically coated with 4-cyano-4-biphenyl [4(4-pentenyloxy)]benzoate (CBPB) and chemically modified using trimethylethoxysilane. The structural and surface properties of the obtained materials were characterized using elemental analysis, thermogravimetry and nitrogen adsorption over a wide pressure range.It was shown that the pore size of the MCM-41 material was not decreased significantly after the coating procedure, even for high loadings of CBPB. Moreover, low pressure adsorption measurements indicated that significant fractions of the MCM-41 surface were not covered by CBPB, even for high CBPB loadings, which suggests that the attained coverage may be very nonuniform. The chemical bonding procedure led to a marked decrease in the pore size and change of surface properties.It was demonstrated that nitrogen adsorption measurements provide a means of a thorough characterization of modified MCM-41 materials, allowing to estimate the surface area, pore volume and pore size distribution. Moreover, low pressure adsorption data can be used to qualitatively or semiquantitatively assess the surface coverage of the coated/bonded organic groups, which may be used to estimate the uniformity of the coverage and therefore, the usefulness of the modification procedure. 相似文献
35.
The sorption of solvent vapours onto dried cellulose has been investigated. The time-dependence and the effect of the solvent-water ratio is discussed. The studies concerned the properties of methanol, ethanol, propanol and butanol. 相似文献
36.
Suspensions of lignite in a solution of a high molecular weight carboxymethylcellulose show peculiar rheological behaviour.
Unless the lignite concentration is sufficiently high, apparent viscosity and viscoelastic moduli of the suspension are lower
than those of the pure solution. This effect is not suppressed by changing pH and seems to be common for low-concentrated
suspensions in solutions of high molecular weight (bio)polymer. It is explained by specific structuring of the suspensions.
Lignite particles at lower concentration separate long cellulose chains and facilitate their movement under shear flow. The
particles loosen inter-chain contacts, disturb and release elastic gel-like structure formed by the long cellulose chains,
which results in the low strain oscillatory deformation, the decrease in the moduli and the increase in the loss angle. If
the amount of lignite particles is sufficiently high, suspension stiffening occurs as usual. No such effect was observed for
suspensions prepared from the low molecular weight derivative.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
37.
Density functional calculations are presented to unravel the first steps of nitrogen fixation of nitrogenase. The individual steps leading from the resting state to nitrogen binding at the FeMo-cofactor with a central nitrogen ligand are characterized. The calculations indicate that the Fe-Mo cage opens as dinitrogen binds to the cluster. In the resting state, the central cage is overall neutral. Electrons and protons are transferred in an alternating manner. Upon dinitrogen binding, one protonated sulfur bridge is broken. An axial and a bridged binding mode of dinitrogen have been identified. Adsorption at the Mo site has been investigated but appears to be less favorable than binding at Fe sites. 相似文献
38.
Sorel Tchewonpi Sagu Eva Landgrber Michal Rackiewicz Gerd Huschek Harshadrai Rawel 《Molecules (Basel, Switzerland)》2020,25(24)
Sorghum is of growing interest and considered as a safe food for wheat related disorders. Besides the gluten, α-amylase/trypsin-inhibitors (ATIs) have been identified as probable candidates for these disorders. Several studies focused on wheat-ATIs although there is still a lack of data referring to the relative abundance of sorghum-ATIs. The objective of this work was therefore to contribute to the characterization of sorghum ATI profiles by targeted proteomics tools. Fifteen sorghum cultivars from different regions were investigated with raw proteins ranging from 7.9 to 17.0 g/100 g. Ammonium bicarbonate buffer in combination with urea was applied for protein extraction, with concentration from 0.588 ± 0.047 to 4.140 ± 0.066 mg/mL. Corresponding electrophoresis data showed different protein profiles. UniProtKB data base research reveals two sorghum ATIs, and P81367; both reviewed and a targeted LC–MS/MS method was developed to analyze these. Quantifier peptides ELAAVPSR ( P81368) and TYMVR ( P81367) were identified and retained as biomarkers for relative quantification. Different reducing and alkylating agents were assessed and combination of tris (2 carboxyethyl) phosphine/iodoacetamide gave the best response. Linearity was demonstrated for the quantifier peptides with standard recovery between 92.2 and 107.6%. Nine sorghum cultivars presented up to 60 times lower ATI contents as compared to wheat samples. This data suggests that sorghum can effectively be considered as a good alternative to wheat. P81368相似文献
39.
Friedman LA You F Sabat M Harman WD 《Journal of the American Chemical Society》2003,125(49):14980-14981
The rhenium furan complexes TpRe(CO)(MeIm)(eta2-2-methylfuran) (1) and TpRe(CO)(MeIm)(eta2-2,5-dmethylfuran) (2) undergo Lewis acid-promoted cyclopentannulation reactions with enones and enals to generate 3-acetylcyclopentene complexes. During the reaction, a rearrangement occurs such that the alpha and beta carbons of the enone are incorporated into the new carbocycle. Treatment of these complexes with an oxidant (H2O2 or silver triflate) liberates the acetylcyclopentene. When a resolved form of the rhenium complex is used, the acetylcyclopentenes can be obtained enantioselectively. 相似文献
40.
THERMODYNAMICS OF PORPHYRIN BINDING TO SERUM ALBUMIN: EFFECTS OF TEMPERATURE, OF PORPHYRIN SPECIES and OF ALBUMIN-CARRIED FATTY ACIDS 总被引:1,自引:0,他引:1
Abstract Porphyrin binding to serum albumin was studied at the molecular level probing the effects of: porphyrin self-aggregation, porphyrin species, temperature and protein-bound fatty acids. Human serum albumin was found to have a single high-affinity site for porphyrin monomers, with binding constants of 2 x 106 , 5 x 107 and 3 x 108 (37o C, neutral pH, M −1 ), for hemato-, deutero- and protoporphyrins, respectively. Three equilibria models for the dimer binding were developed and tested. The data were found to fit best with a model proposing a single high-affinity binding site for the dimer, independent of and different than the monomer site. The binding constants of the hematoporphyrin and deuteroporphyrin dimers to human serum albumin (37o C, neutral pH, M−l ) being 4 x 10* and 5 x 108 respectively. The temperature dependence (Dp and HSA, 22-37o C) of the monomer binding showed the process to be entropy-driven (δGo = -45 kJ mol−1 ; δSo =+146 kJ mol−1 ; δHo = 0 kJ mol−1 ). For the dimer binding, the enthalpy change was found to be highly temperature-dependent implying continuous changes in the heat capacity of the system over the entire temperature range, the trend at the 37o C region fitting an entropy-driven process. The monomer vs dimer differences in temperature dependence strongly support separate and independent binding sites for these species. Similar thermodynamics were determined for fatty-acid carrying as well as for fatty-acid free HSA, with mild quantitative (but not qualitative) shifts. 相似文献