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The interactions between human serum albumin (HSA) and fluphenazine (FPZ) in the presence or absence of rutin or quercetin were studied by fluorescence, absorption and circular dichroism (CD) spectroscopy and molecular modeling. The results showed that the fluorescence quenching mechanism was static quenching by the formation of an HSA-FPZ complex. Entropy change (Δ S0) and enthalpy change (Δ H0) values were 68.42 J/(mol ⋅K) and −4.637 kJ/mol, respectively, which indicated that hydrophobic interactions and hydrogen bonds played major roles in the acting forces. The interaction process was spontaneous because the Gibbs free energy change (Δ G0) values were negative. The results of competitive experiments demonstrated that FPZ was mainly located within HSA site I (sub-domain IIA). Molecular docking results were in agreement with the experimental conclusions of the thermodynamic parameters and competition experiments. Competitive binding to HSA between flavonoids and FPZ decreased the association constants and increased the binding distances of FPZ binding to HSA. The results of absorption, synchronous fluorescence, three-dimensional fluorescence, and CD spectra showed that the binding of FPZ to HSA caused conformational changes in HSA and simultaneous effects of FPZ and flavonoids induced further HSA conformational changes. [ABSTRACT FROM AUTHOR]

In this work, the binding characteristics of methylene blue (MB) to human serum albumin (HSA) and the influence of Cu2+ and Fe3+ on the binding affinity ofMBto HSAwere investigated using fluorescence, absorption, circular dichroism(CD) spectroscopy andmolecular modelling. The results of competitive binding experiments using the site probes ketoprofen and ibuprofen as specific markers suggested that MB was located in site I within sub-domain IIA of HSA. The molecular modelling results agreed with the results of competitive site marker experiments and the results of CD spectra indicated that the interaction betweenMB and HSA caused the conformational changes in HSA. The binding affinity ofMB to HSAwas enhanced but to a different extent in the presence of Cu2+ and Fe3+, respectively, which indicated that the influence of different metal ions varied. Enhancement of the binding affinity of MB to HSA in the presence of Cu2+ is due to the formation of Cu2+-HSA complex leading to the conformational changes in HSA, whereas in the presence of Fe3+, enhancement of the binding affinity is due to the greater stability of the Fe3+-HSA-MB complex compared with the MB-HSA complex. [ABSTRACT FROM AUTHOR]

Soybean isoflavone ( SIF) has been demonstrated to have neuroprotective effects induced by β-amyloid peptides ( Aβ) through suppressing oxidative stress; however, the explicit mechanisms still remain uncovered. In the present study, 32 Wistar rats were randomly divided into four groups: an Aβ1-42-treated group, a SIF + Aβ1-42 group, a SIF-treated group and a control group. We measured the protein content of 8-hydroxydeoxyguanosine (8- Ohd G) and m RNA expression of 8-oxoguanine DNA glycosylase ( OGG1). The protein expression of OGG1, Bcl-xl, Bad, beta subunit of ATP synthase ( ATPB) and pyruvate dehydrogenase ( PDH) in brain was also measured. The results showed that the level of 8- OHd G in both SIF groups was significantly decreased compared to the Aβ1-42-treated group ( p < 0.05), while the m RNA and protein expression of OGG1 in the SIF + Aβ1-42 groups were up-regulated compared with the Aβ1-42-treated groups ( p < 0.05). The expression of Bcl-xl was up-regulated in the SIF-treated group compared with the Aβ1-42-treated groups ( p < 0.05), while the expression of Bad was down-regulated in the two SIF-treated groups ( p < 0.05). Aβ1-42 significantly down-regulated the expression of ATPase and PDH proteins compared with the control group ( p < 0.05). SIF reversed the down-regulation effects on the mitochondrial energy metabolic enzymes induced by Aβ1-42 ( p < 0.05) in the rats. These results suggest that SIF alleviate the oxidative stress in neurons and mitochondria of rat brains mediated by Aβ1-42, and these protective effects might be associated with the regulation of OGG1, Bad, Bcl-xl, ATPB and PDH. [ABSTRACT FROM AUTHOR]