75 research outputs found
Sequential Proton Loss Electron Transfer in Deactivation of Iron(IV) Binding Protein by Tyrosine Based Food Components
The ironÂ(IV) binding protein ferrylmyoglobin,
MbFeÂ(IV)î—»O,
was found to be reduced by tyrosine based food components in aqueous
solution through a sequential proton loss electron transfer reaction
mechanism without binding to the protein as confirmed by isothermal
titration calorimetry. Dopamine and epinephrine are the most efficient
food components reducing ferrylmyoglobin to oxymyoglobin, MbFeÂ(II)ÂO<sub>2</sub>, and metmyoglobin, MbFeÂ(III), as revealed by multivariate
curve resolution alternating least-squares with second order rate
constants of 33.6 ± 2.3 L/mol/s (Δ<i>H</i><sup>⧧</sup> of 19 ± 5 kJ/mol, Δ<i>S</i><sup>⧧</sup> of −136 ± 18 J/mol K) and 228.9 ±
13.3 L/mol/s (Δ<i>H</i><sup>⧧</sup> of 110
± 7 kJ/mol, Δ<i>S</i><sup>⧧</sup> of 131
± 25 J/mol K), respectively, at pH 7.4 and 25 °C. The other
tyrosine based food components were found to reduce ferrylmyoglobin
to metmyoglobin with similar reduction rates at pH 7.4 and 25 °C.
These reduction reactions were enhanced by protonation of ferrylmyoglobin
and facilitated proton transfer at acidic conditions. Enthalpy–entropy
compensation effects were observed for the activation parameters (Δ<i>H</i><sup>⧧</sup> and Δ<i>S</i><sup>⧧</sup>), indicating the common reaction mechanism. Moreover, principal
component analysis combined with heat map were performed to understand
the relationship between density functional theory calculated molecular
descriptors and kinetic data, which was further modeled by partial
least squares for quantitative structure–activity relationship
analysis. In addition, a three tyrosine residue containing protein,
lysozyme, was also found to be able to reduce ferrylmyoglobin with
a second order rate constant of 66 ± 28 L/mol/s as determined
by a competitive kinetic method
Solubilities of Naringin Dihydrochalcone in Pure Solvents and Mixed Solvents at Different Temperatures
Naringin dihydrochalcone
(naringin DC) is an intense sweetener
and a strong antioxidant with potential applications in many food
and pharmaceutical products. However, the poor solubility and stability
of naringin DC in aqueous systems at room temperature severely limits
its applications in these areas. The solubility of naringin dihydochalone
was quantified in water, ethyl acetate, binary solvent mixtures of
methanol + water and ethanol + water by a synthetic method at different
temperatures. The solubility of naringin DC in a given solvent increases
with the rising temperature. The experimental data were well correlated
with an Apelblat equation and Universal Quasichemical model. Moreover,
the physical properties and crystal habit of naringin DC were discussed
through a thermogravimetric analyzer, a differential scanning colorimeter,
and a scanning electron microscope
Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands
Aqueous
solubility of zinc phytate (<i>K</i><sub>sp</sub> = (2.6
± 0.2) × 10<sup>–47</sup> mol<sup>7</sup>/L<sup>7</sup>), essential for zinc bioavailability from plant foods,
was found to decrease with increasing temperature corresponding to
Δ<i>H</i><sub>dis</sub> of −301 ± 22 kJ/mol
and Δ<i>S</i><sub>dis</sub> of −1901 ±
72 J/(mol K). Binding of zinc to phytate was found to be exothermic
for the stronger binding site and endothermic for the weaker binding
site. The solubility of the slightly soluble zinc citrate and insoluble
zinc phytate was found to be considerably enhanced by the food components
with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving
force for the enhanced solubility is mainly due to the complex formation
between zinc and the investigated food components rather than ligand
exchange and ternary complex formation as revealed by quantum mechanical
calculations and isothermal titration calorimetry. Histidine and citrate
are promising ligands for improving zinc absorption from phytate-rich
foods
Modified Method for Measuring the Solubility of Pharmaceutical Compounds in Organic Solvents by Visual Camera
A modified synthetic method with
a high definition visual camera
technique for measuring the solubility of solutes in solvents or mixed
solvents was proposed. To verify the reliability of the experimental
apparatus, the solubility of NH<sub>4</sub>Cl in water was determined
at different temperatures. The relative standard errors were less
than 1%, compared to the literature data. The solubilities of betulonic
acid in six organic solvents from (278.15 to 313.15) K were measured
and correlated with the Apelblat equation and universal quasichemical
equation, respectively. The modified method was quite concise and
user-friendly, and made the process of dissolution to become visualized
and automatic
Solubilities of Three Flavonoids in Different Natural Deep Eutectic Solvents at <i>T</i> = (288.15 to 328.15) K
The
solubilities of phloretin, phlorizin, and naringin dihydrochacone
(naringin DC) respectively were determined in a ternary system made
of natural deep eutectic solvents (NADES) at the temperature range
from 288.15 to 328.15 K with an analytical method. Compared with the
solubility of phloretin in water, there was a dramatic improvement
in the solubility of phloretin in the selected NADES, especially in
CCiH and CSH. The density and viscosity of four kinds of NADES choline
chloride + glucose + H<sub>2</sub>O, choline chloride + citric acid
+ H<sub>2</sub>O, citric acid + glucose + H<sub>2</sub>O, and choline
chloride + sucrose + H<sub>2</sub>O were studied in this work. The
solubility data were correlated with Apelblat equation and <i>λh</i> equation. The fitted results showed that the models
are capable of representing the data with high accuracy
Measurement and Correlation of Solubility of Theobromine, Theophylline, and Caffeine in Water and Organic Solvents at Various Temperatures
The
solubility of theobromine, theophylline, and caffeine in water
and five organic solvents including methanol, ethanol, 1-propanol,
ethyl acetate, and acetone was determined by a high performance liquid
chromatography method at <i>T</i> = (288.15 to 328.15) K
and atmospheric pressure. It was found that the solubility of theobromine,
theophylline, and caffeine in these solvents increased with increasing
temperature. The empirical Apelblat equation and universal quasichemical
model were used to correlate the experimental solubility. The results
showed that both models can satisfactorily correlate the solubility
data. The crystal forms of the solutes in equilibrium with the saturated
solution were analyzed using scanning electron microscopy and powder
X-ray diffraction
Expression of genes associated with auxin and GA signaling in ovaries after pollination and 2,4-D/GA<sub>3</sub> treatments.
<p>Expression of genes associated with auxin and GA signaling in ovaries after pollination and 2,4-D/GA<sub>3</sub> treatments.</p
Three trinuclear Ru(II) complexes containing 4,5-diazafluorene and 2,2′-bipyridine: synthesis, absorption spectrum, luminescence, and redox behavior
<div><p>Three heterotopic ligands L<sup>1</sup>, L<sup>2</sup>, and L<sup>3</sup> have been prepared by the reaction of 4,4′-bis(bromomethyl)-2,2′-bipyridine with 4,5-diazafluoren-9-oxime, 9-(2-hydroxy)phenylimino-4,5-diazafluorene, and 9-(4-hydroxy)phenylimino-4,5-diazafluorene, respectively, in DMF. The three ligands consist of two 4,5-diazafluorene units and one 2,2′-bipyridine unit. Ru(II) complexes [{Ru(bpy)<sub>2</sub>}<sub>3</sub>(μ<sub>3</sub>-L<sup>1−3</sup>)](PF<sub>6</sub>)<sub>6</sub> (bpy = 2,2′-bipyridine) were prepared by refluxing Ru(bpy)<sub>2</sub>Cl<sub>2</sub>·2H<sub>2</sub>O and the ligands in 2-methoxyethanol. The three Ru(II) complexes display metal-to-ligand charge-transfer absorption at 445–450 nm and one Ru(II)-centered oxidation at 1.32 V in CH<sub>3</sub>CN solution at room temperature. Upon excitation into the metal-to-ligand charge-transfer band, the emission intensities of [{Ru(bpy)<sub>2</sub>}<sub>3</sub>(μ<sub>3</sub>-L<sup>2</sup>)]<sup>6+</sup> and [{Ru(bpy)<sub>2</sub>}<sub>3</sub>(μ<sub>3</sub>-L<sup>3</sup>)]<sup>6+</sup> are almost equal to that of [{Ru(bpy)<sub>2</sub>}<sub>3</sub>(μ<sub>3</sub>-L<sup>1</sup>)]<sup>6+</sup> in CH<sub>3</sub>CN solution at room temperature, but weaker than that of [{Ru(bpy)<sub>2</sub>}<sub>3</sub>(μ<sub>3</sub>-L<sup>1</sup>)]<sup>6+</sup> in EtOH–MeOH (4 : 1, v/v) glassy matrix at 77 K.</p></div
Highly Iso-Selective and Active Catalysts of Sodium and Potassium Monophenoxides Capped by a Crown Ether for the Ring-Opening Polymerization of <i>rac</i>-Lactide
Sodium
and potassium complexes supported by a bulky monophenoxy with one
xanthenyl group at the ortho-position and 18-crown-6 or 15-crown-5
as an auxiliary ligand were synthesized and characterized. These complexes
are highly iso-selective and active catalysts for the controlled ring-opening
polymerization of <i>rac</i>-lactide. The best isotacticity
(<i>P</i><sub>m</sub>) achieved was 0.86, which is the highest
iso-selectivity reported to date for an alkali-metal complex. In addition,
the corresponding polymer exhibited a high <i>T</i><sub>m</sub> of 182 °C. Furthermore, the polymerization looks like
an anti-Arrhenius reaction, which is slower at high temperatures than
at low temperatures
Summary of the RNA-Seq data in ovaries during fruit set.
<p>Summary of the RNA-Seq data in ovaries during fruit set.</p
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