ESTROGEN RECEPTOR EXPRESSION ON BREAST CANCER PATIENTS' SURVIVAL UNDER SHAPE RESTRICTED COX REGRESSION MODEL.

For certain subtypes of breast cancer, study findings show that their level of estrogen receptor expression is associated with their risk of cancer death, and also suggests a non-linear effect on the hazard of death. A flexible form of the proportional hazards model, (∣ ) = () exp( )(), is desirable to facilitate a rich class of covariate effect on a survival outcome to provide meaningful insight, where the functional form of () is not specified except for its shape. Prior biologic knowledge on the shape of the underlying distribution of the covariate effect in regression models can be used to enhance statistical inference.

Multiple free radical scavenging reactions of aurones.

A series of naturally occurring 3',4'-dihydroxy aurones have been studied with regard to multiple free radical scavenging reactions in the gas and two liquid phases using density functional theory (DFT). All of the aurones prefer to perform (2 + n)-HAT mechanism to trap 2 + n free radicals, where n is the sum of the numbers of catechol and guaiacyl units in the gas and benzene phases. The second HAT reaction favours occurring in the same catechol moiety of the first HAT mechanism occurring OH group due to the formation of a stable quinone and the highly exothermic step of the final stable product formation.

The structure and hydrogen-bond properties of -alkyl--methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide and DMSO mixtures.

Mixing ionic liquids (ILs) with molecular solvents can extend the practical applications of ILs and overcome the drawbacks of neat ILs. Knowledge on the structure and hydrogen-bond interaction properties of IL-molecular solvent mixtures is essential for chemical applications. In this work, the structure and hydrogen-bond features of N-alkyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([CnMPyr][Tf2N], n = 3, 4, 6 and 8) and DMSO mixtures were studied using Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations.

Effects of different ester chains on the antioxidant activity of caffeic acid.

Caffeic acid ester derivatives have been widely found in propolis extract and plants. In this work, the effect of ester groups with different aromatic and alkyl chains on the antioxidant activity of caffeic acid was performed on the double H/e process using DFT calculations. We found that 1) O3-H3⋯O4 intramolecular hydrogen-bonds exist in the catechol moiety of the investigated compounds, which have the same strength and are closed shell interactions, weak-strength and electrostatic in nature, making the 4-OH more favourable than 3-OH to trap free radicals.

Fabrication of Asymmetric Phosphatidylserine-Containing Lipid Vesicles: A Study on the Effects of Size, Temperature, and Lipid Composition.

The asymmetric distribution of lipids in plasma membranes is closely related to the physiological functions of cells. To improve our previous approach in fabricating asymmetric vesicles, we defined a parameter, asymmetric degree, in this work and investigated the effects of vesicle size, incubation temperature, and lipid composition on the formation process of asymmetric phosphatidylserine (PS)-containing lipid vesicles. The results indicate that all of the three factors have marked but different effects on the time-dependent asymmetric degree of the vesicles as well as the flip and flop rate constants of the PS lipids.

Free radical scavenging potency of ellagic acid and its derivatives in multiple H/e processes.

The reaction energetics of the multiple free radical scavenging mechanisms of ellagic acid and its derivatives were studied by DFT method. Ellagic acid and its derivatives that bear catechol or guaiacyl moieties can proceed multiple free radical scavenging processes. Intramolecular hydrogen-bonds were found in the most stable geometries of the investigated compounds and can influence the antioxidant activity of the related groups and hydrogen atom/proton loss sequence.

Structures and non-covalent interaction behaviours of binary systems containing the ionic liquid 1-(2'-hydroxylethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and chloroform.

Mixtures of ionic liquids (ILs) and molecular solvents can overcome the drawbacks (high viscosity, high polarity, and high cost) of pure ILs and extend their practical use. The structural and interaction properties of ILs form the bases for understanding their properties. In this work, the structural properties of the mixtures of an IL, 1-(2'-hydroxylethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2OHMIM][TfN]), with chloroform, a molecular solvent of weak polarity, in various concentrations were analysed using Fourier transform infrared spectroscopy and density functional theory calculations.

Role of C‒H bond in the antioxidant activities of rooperol and its derivatives: A DFT study.

Rooperol and its derivatives, derived from the Hypoxis rooperi plant, are polyphenolic and norlignan compounds with excellent antioxidant activities. The reaction enthalpies for the free-radical scavenging by rooperol and its six derivatives were studied using density functional theory. We found that the C-H groups played a significant role in the antioxidant activities in non-polar phases.

Local Acid Strength of Solutions and Its Quantitative Evaluation Using Excess Infrared Nitrile Probes.

We propose the concept of local acidity in condensed-phase chemistry in this work. The feature is demonstrated in trifluoroethanol (TFE) by employing two Fourier-transform infrared spectroscopy (FTIR) nitrile probes, acetonitrile (CHCN) and benzonitrile (PhCN). Specifically, three positive excess peaks were found in the binary systems composed of TFE and a probe using excess spectroscopy.

The structure and interaction properties of two task-specific ionic liquids and acetonitrile mixtures: A combined FTIR and DFT study.

The mixtures of ionic liquid (IL) and acetonitrile (CHCN) can be used as reaction media, supercapacitors and thermally stable electrolytes. The macroscopic properties of ILs-CHCN mixtures have been extensively studied. However, some fundamental questions regarding the microscopic properties of ILs-CHCN mixtures still remain to be answered.

A combination of FTIR and DFT to study the microscopic structure and hydrogen-bonding interaction properties of the [BMIM][BF] and water.

The structure and hydrogen-bond interaction property of water and a model ionic liquid (IL): 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF]) were studied using the combination of Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. The O‒D stretching vibration region of the deuterated water was an area of special focus. Excess infrared spectroscopy with enhanced resolution was applied to analyse the original infrared spectra of v(O‒D).

Theoretical insight into the antioxidative activity of isoflavonoid: The effect of the C2=C3 double bond.

Isoflavonoids are one of the most important groups of naturally occurring antioxidants. Their structural features are important for evaluating their antioxidative activity. In this work, density functional theory (DFT) methods were applied to investigate the influence of the C2=C3 double bond on the antioxidative activity of isoflavonoids based on three currently accepted radical scavenging mechanisms from the viewpoint of thermodynamics.

The structure and hydrogen-bond behaviours of binary systems containing ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate and methanol/ethanol.

Mixing ionic liquids (ILs) with a molecular cosolvent can largely reduce the high viscosities, high polarities, and high costs of ILs. The macroscopic properties of IL-cosolvent mixtures have been studied extensively. However, some fundamental questions regarding the microscopic properties of the binary mixtures still remain to be answered.

Effect of Imidazolium-Based Ionic Liquids on the Structure and Phase Behavior of Palmitoyl-oleoyl-phosphatidylethanolamine.

Among various applications, ionic liquids (ILs) have been used as antimicrobial agents in laboratories, possibly through induction of the leakage of bacteria. A molecular-level understanding of the mechanism that describes how ILs enhance the permeation of membranes is still lacking. In this study, the effects of imidazolium-based ILs with different alky chain lengths on the structure and phase behavior of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE), which is a representative bacteria-membrane-rich lipid, have been investigated.

DFT Studies on the Antioxidant Activity of Naringenin and Its Derivatives: Effects of the Substituents at C3.

The radical scavenging activity of a flavonoid is largely influenced by its structure. The effects of the substituents at C3 position on the antioxidant activity of naringenin were carried out using the density functional theory (DFT) method. The reaction enthalpies related with the three well-established mechanisms were analyzed.

A DFT-based study of the hydrogen-bonding interactions between myricetin and ethanol/water.

Flavonoids are vital constituents of propolis that are responsible for its medicinal activity. Flavonoid extraction commonly employs ethanol and water as solvents. In the extraction reaction, hydrogen-bonding interactions play a crucial role.

Substituent Effects on the Radical Scavenging Activity of Isoflavonoid.

Understanding the role of substituents is of great importance for the preparation of novel phenolic compounds with enhanced antioxidative properties. In this work, the antioxidative activity of isoflavonoid derivatives with different substituents placed at the C2 position was determined by density functional theory (DFT) calculations. The bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA) related to hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were calculated.

The influence of the H5⋯OC4 intramolecular hydrogen-bond (IHB) on the antioxidative activity of flavonoid.

Flavonoids widely found in natural foods are characterized by acting as antioxidants compounds. There are close relationship between the antiradical activities and structural properties of flavonoids. In this work, density functional theory (DFT) methods were applied to investigate the influence of the H5⋯OC4 intramolecular hydrogen-bond (IHB) on the antiradical activity of flavonoid based on three prevalently accepted radical scavenging mechanisms: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT) and sequential proton-loss electron-transfer (SPLET).

The influence of C2C3 double bond on the antiradical activity of flavonoid: Different mechanisms analysis.

Flavonoids widely found in bee products are excellent antioxidants. The structural features are important in evaluating the antiradical activity of flavonoid. In this work, the density functional theory (DFT) methods were applied to investigate the influence of C2C3 double bond on the antiradical activity of flavonoid based on three prevalently accepted radical scavenging mechanisms from the thermodynamic aspect.

The antioxidative activity of piceatannol and its different derivatives: Antioxidative mechanism analysis.

The naturally occurring stilbenes piceatannol and its derivatives are excellent antioxidants. In this work, the antioxidative activities of piceatannol and different piceatannol derivatives have been investigated using the density functional theory (DFT) method based on three widely accepted radical scavenging mechanisms, namely, the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). The gas and four solvent phases, namely, bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA) and electron transfer enthalpy (ETE), related to these mechanisms were calculated to elucidate the antioxidative capacities of the investigated compounds.

The Substituent Effect on the Radical Scavenging Activity of Apigenin.

Flavonoids widely found in natural foods are excellent free radical scavengers. The relationship between the substituent and antioxidative activity of flavonoids has not yet been completely elucidated. In this work, the antioxidative activity of apigenin derivatives with different substituents at the C3 position was determined by density functional theory (DFT) calculations.

The surrounding environments on the structure and antioxidative activity of luteolin.

Luteolin is an excellent antioxidant found in a wide variety of natural foods, such as honey and pollen. In this work, the effect of the surrounding environments on the structure and antioxidative activity of luteolin was carried out using density functional theory (DFT) calculation. The studied environments are gas, benzene, chloroform, pyridine, acetonitrile, ethanol, DMSO, and water.

Identifying Different Halogen-/Hydrogen-Bonding Interaction Modes in Binary Systems that Contain an Acetate Ionic Liquid and Various Halobenzenes.

Elucidation of the nature of noncovalent interactions between ionic liquids (ILs) and halogenated molecules is of particular importance for both fundamental research and drug development. Herein, the noncovalent interactions between 1-butyl-3-methyl-imidazolium acetate and three halobenzenes C F X (X=I, Br, H) were investigated. The iodine derivative shows the strongest interaction with the IL, followed by C F Br and C F H.

Controllable engineering of asymmetric phosphatidylserine-containing lipid vesicles using calcium cations.

A novel method to produce controllable asymmetric lipid vesicles using Ca is reported. The enrichment of negatively charged phosphatidylserine (PS) molecules in the inner leaflet is found not due to charge-charge attraction, but rather a modulation effect on the occupying size of the headgroups of PS molecules.