Biomedical subjects

Yuanzhi Song

Publications and source records attributed to Yuanzhi Song.

7 recordsLinked to original sources

PubMed2006

Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode.

DFT-B3LYP/6-31G (d, p) and HF/6-31G (d, p) calculations are performed for deoxidized norepinephrineat (NP(R)) and its oxidized form (NP(O)). The electrochemistry of norepinephrineat (NP) was studied by cyclic voltammetry (CV) at a pyrolytic graphite electrode modified by Nafion multi-walled carbon nanotubes (MWNTs) in phosphate buffers at pH 6.0, showing that the standard electrode potential of half reaction for NP(O), H+/NP(R) is 0.75l V. This experimental standard electrode potential of half reaction is consistent with that calculated using the energies of solvation and sum of electronic and thermal free energies of NP(R) and NP(O). The frontier orbital theory and Mülliken charges of molecular explain the electrochemical behavior of CV at modified electrode well. The singlet vertical excited states for NP(R) and NP(O) are also discussed.

Buffers↗

PubMed2006

Theoretical studies on electrochemistry of p-aminophenol.

Geometric parameters, vibrational frequencies and thermochemical values of p-quinonimine (p-Q) and p-aminophenol (p-AP) were computed by ab initio calculation (HF) and density function theory (DFT) with the 6-31G(d,p) basis set. Cyclic voltammetry with a goldren electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that standard electrode potential of half reaction for (p-Q) and (p-AP) is 0.728V. Standard electrode potential of half reaction for p-Q and p-AP were calculated using the sum of electronic and thermal free energies of p-Q and p-AP with normal hydrogen electrode (NHE) as a reference electrode. The results show that the theoretical standard electrode potential of half reaction for p-Q and p-AP is 0.682V at B3LYP/6-31G(d,p) level and 0.622V at HF/6-31G(d,p) level, respectively, indicating that computed standard electrode potential at B3LYP/6-31G(d,p) level are more reliable than that at HF/6-31G(d,p) level.

Aminophenols↗

PubMed2006

Theoretical analysis on retention behavior of pigments in reversed-phase high-performance liquid chromatographic (HPLC).

Quantitative structure-retention relationship (QSRR) models have been used successfully to predict and explain retention behavior of pigments in reversed-phase high-performance liquid chromatography (HPLC). The semi-empirical quantum chemical method (PM3) in Gaussian98 was employed to calculate a set of molecular descriptors of pigments. Using multiple linear regression (MLR), we obtained empirical functions with high correlation coefficient between retention times and quantum-chemical descriptors. This analysis indicated that the proposed QSRR models were satisfactory.

Chromatography, High Pressure Liquid↗

PubMed2006

Calculation of standard electrode potential of half reaction for benzoquinone and hydroquinone.

Geometric parameters, the vibrational frequencies and thermochemical values of benzoquinone and hydroquinone were computed using ab initio molecular orbital calculations (HF) and density function theory (B3LYP) methods with the 6-31G(d) basis set, respectively. The calculated frequencies for benzoquinone and hydroquinone were used for the assignment of the IR frequencies observed in the experimental IR spectrum. Cyclic voltammetry with a glassy carbon electrode of hydroquinone solutions in phosphate buffers at pH 7.0 showed that standard electrode potential of half reaction for benzoquinone and hydroquinone is 0.714V. Standard electrode potential of half reaction for benzoquinone and hydroquinone was calculated using the sum of electronic and thermal free energies, enthalpies of sublimation and energies of solvation for benzoquinone and hydroquinone.

Benzoquinones↗

PubMed2005

Density-functional theory studies on standard electrode potentials of half reaction for L-adrenaline and adrenalinequinone.

DFT (B3LY/6-31G(d) and B3PW91/6-31G(d)) calculations are performed for L-adrenaline and adrenalinequinone. The calculated IR spectrum of L-adrenaline is used for the assignment of IR frequencies that are observed in the experimental IR spectrum. Cyclic voltammetry with a platinum electrode of L-adrenaline solutions in phosphate buffers at pH 1 shows that standard electrode potential of half reaction for L-adrenaline and adrenalinequinone is 0.803 V. Standard electrode potential of half reaction for L-adrenaline and adrenalinequinone is calculated using the energies of solvation and the sum of electronic and thermal free energies of L-adrenaline and adrenalinequinone.

Electrochemistry↗

PubMed2005

Density-functional theory and ab initio Hartree-Fork studies on the structural parameters and chemical activity of the free radicals generated by benzoquinone and hydroquinone.

Density-functional theory (DFT) calculations were performed for calculation of the theoretical spectra and the chemical activities of free radicals generated by benzoquinone and hydroquinone as well as the transition states, and the calculated spectra were used for the assignment of the frequencies observed in the experimental IR spectra. The calculated geometrical parameters, the predicted IR spectra, and the chemical activities of free radicals and transition states were also compared with those of benzoquinone and hydroquinone. The reactive mechanisms of free radicals generated by benzoquinone and hydroquinone are also discussed using ab initio Hartree-Fork (HF) methods.

Benzoquinones↗

PubMed2005

Theoretical analysis of the retention behavior of alcohols in gas chromatography.

Quantitative structure-retention relationship (QSRR) models for the chromatographic (GC) retention times of alcohols on Superox 20M-diglycerol polarity stationary phase have been developed. Semi-empirical quantum chemical method (AM1) in MOPAC and Hartree-Fock (HF) method in Gaussian 98 implemented were employed to calculate a set of molecular descriptors of alcohols and ethyl acetate. Using multiple linear regression (MLR), we obtained the empirical functions with high correlation coefficient between retention times and quantum-chemical descriptors. The retention mechanism of alcohols of separation operating in the gas chromatogram was discussed. The results indicated that the QSRR models proposed were satisfactory.

Alcohols↗