3DEEM spectroscopy analysis to assess the EPS composition in different carriers in HMBR systems.

A hybrid membrane bioreactor (HMBR) with biological band carriers (Reactor A) and an HMBR with suspended honeycomb carriers (Reactor B) were conducted in parallel to investigate the effects of different carriers on extracellular polymeric substances (EPS). Composition and concentration of EPS were examined by three-dimensional excitation-emission matrix (3DEEM) fluorescence spectra and parallel factor analysis (PARAFAC). 3DEEM spectra demonstrated that the main organic substances of the EPS in two reactors were protein-like, humic acid-like and fulvic acid-like substances. The fluorescence intensity (FI) indicated that the protein-like composition was dominant in EPS, and its intensity in reactor B was stronger than that in A (392.94 > 250.25). Results of the FI identified from the 3DEEM by PARAFAC showed that the EPS in two reactors included two humic acid-like compositions C1 (230, 320/406 nm), C2 (250, 360/440 nm) and one protein-like C4 (230, 280/340 nm), while C3 was fulvic acid-like (220/429 nm) and protein-like (230/357 nm) in reactor A and B, respectively. The proportion and FI of protein-like substances in reactor B were higher than that in A. Consequently, it was concluded that reactor A could control the membrane fouling effectively, compared with reactor B.

Investigations on the interactions between naphthalimide-based anti-tumor drugs and human serum albumin by spectroscopic and molecular modeling methods.

The interactions between the three kinds of naphthalimide-based anti-tumor drugs (NADA, NADB, NADC) and human serum albumin (HSA) under simulated physiological conditions were investigated by fluorescence spectroscopy, circular dichroism spectroscopy and molecular modeling. The results of the fluorescence quenching spectroscopy showed that the quenching mechanisms for different drugs were static and their affinity was in a descending order of NADA > NADB > NADC. The relative thermodynamic parameters indicated that hydrophobic force was the predominant intermolecular force in the binding of NAD to HSA, while van der Waals interactions and hydrogen bonds could not be ignored. The results of site marker competitive experiment confirmed that the binding site of HSA primarily took place in site I. Furthermore, the molecular modeling study was consistent with these results. The study of circular dichroism spectra demonstrated that the presence of NADs decreased the α-helical content of HSA and induced the change of the secondary structure of HSA.

Dysfunction of Rice Mitochondrial Membrane Induced by Yb3+.

Ytterbium (Yb), a widely used rare earth element, is treated as highly toxic to human being and adverseness to plant. Mitochondria play a significant role in plant growth and development, and are proposed as a potential target for ytterbium toxicity. In this paper, the biological effect of Yb(3+) on isolated rice mitochondria was investigated. We found that Yb(3+) with high concentrations (200 ~ 600 µM) not only induced mitochondrial membrane permeability transition (mtMPT), but also disturbed the mitochondrial ultrastructure. Moreover, Yb(3+) caused the respiratory chain damage, ROS formation, membrane potential decrease, and mitochondrial complex II activity reverse. The results above suggested that Yb(3+) with high concentrations could induce mitochondrial membrane dysfunction. These findings will support some valuable information to the safe application of Yb-based agents.

Study on Biological Effects of La(3+) on Rat Liver Mitochondria by Microcalorimetric and Spectroscopic Methods.

The effects of lanthanum on heat production of mitochondria isolated from Wistar rat liver were investigated with microcalorimetry; simultaneously, the effects on mitochondrial swelling and membrane potential (Δψ) were determined by spectroscopic methods. La(3+) showed only inhibitory action on mitochondrial energy turnover with IC50 being 55.8 µmol L(-1). In the spectroscopic experiments, La(3+), like Ca(2+), induced rat liver mitochondrial swelling and decreased membrane potential (Δψ), which was inhibited by the specific permeability transition inhibitor, cyclosporine A (CsA). The induction ability of La(3+) was stronger than that of Ca(2+). These results demonstrated that La(3+) had some biotoxicity effect on mitochondria; the effects of La(3+) and Ca(2+) on rat liver mitochondrial membrane permeability transition (MPT) are different, and La represents toxic action rather than Ca analogy.

Effects of La(III) and Ca(II) on isolated Carassius auratus liver mitochondria: heat production and mitochondrial permeability transition.

The effects of lanthanum and calcium on heat production of mitochondria isolated from Carassius auratus liver were investigated by microcalorimetry, and their effects on mitochondrial swelling and membrane potential (Δψ) were determined by spectroscopic methods. La(3+) showed only inhibitory action on mitochondrial energy turnover with inhibition concentration of 50 % (IC50) being 71.2 µmol L(-1). Similarly, Ca(2+) restrained the heat production of mitochondria, and the IC50 of Ca(2+) was much higher than that of La(3+). In the spectroscopic experiments, La(3+) and Ca(2+) induced fish liver mitochondrial swelling and decreased membrane potential (Δψ), and the induction ability of La(3+) was stronger than that of Ca(2+). It is concluded that the effects of La(3+) and Ca(2+) on fish liver mitochondria differ, and La represents toxic action rather than Ca analogy.

Membrane permeability transition and dysfunction of rice mitochondria effected by Er(III).

Herein, the biological effects of heavy rare earth ion Er(III) on rice mitochondria were comprehensively investigated mainly by spectroscopic methods. The experimental results demonstrated that Er(III) could lead to the swelling of rice mitochondria, collapse of mitochondrial transmembrane potential, decrease of membrane fluidity, promotion of H(+) permeability and suppression of K(+) permeability. These further indicated that Er(III) could induce the mitochondrial permeability transition (MPT) and the dysfunction of rice mitochondria. The ultra-structure change of mitochondria observed by transmission electron microscopy (TEM) also proved that Er(III) induced MPT. Moreover, the testing results of the protective effect of four different agents on mitochondrial swelling implied that the thiol chelation on the mitochondrial inner membrane was the main reason that caused the MPT.

Investigation of the interaction between quercetin and human serum albumin by multiple spectra, electrochemical impedance spectra and molecular modeling.

Quercetin (Qu), a flavonoid compound, exists widely in the human diet and exhibits a variety of pharmacological activities. This work is aimed at studying the effect of Qu on the bioactive protein, human serum albumin (HSA) under simulated biophysical conditions. Multiple spectroscopic methods (including fluorescence and circular dichroism), electrochemical impedance spectra (EIS) and molecular modeling were employed to investigate the interaction between Qu and HSA. The fluorescence quenching and EIS experimental results showed that the fluorescence quenching of HSA was caused by formation of a Qu-HSA complex in the ground state, which belonged to the static quenching mechanism. Based on the calculated thermodynamic parameters, it concluded that the interaction was a spontaneous process and hydrogen bonds combined with van der Waal's forces played a major role in stabilizing the Qu-HSA complex. Molecular modeling results demonstrated that several amino acids participated in the binding process and the formed Qu-HSA complex was stabilized by H-bonding network at site I in sub-domain IIA, which was further confirmed by the site marker competitive experiments. The evidence from circular dichroism (CD) indicated that the secondary structure and microenvironment of HSA were changed. Alterations in the conformation of HSA were observed with a reduction in the amount of α helix from 59.9% (free HSA) to 56% (Qu-HSA complex), indicating a slight unfolding of the protein polypeptides.

Spectroscopic studies on the interactions between CdTe quantum dots coated with different ligands and human serum albumin.

This paper investigates the interactions between human serum albumin (HSA) and CdTe quantum dots (QDs) with nearly identical hydrodynamic size, but capped with four different ligands (MPA, NAC, and GSH are negatively charged; CA is positively charged) under physiological conditions. The investigation was carried out using fluorescence spectroscopy, circular dichroism (CD) spectra, UV-vis spectroscopy, and dynamic light scattering (DLS). The results of fluorescence quenching and UV-vis absorption spectra experiments indicated the formation of the complex of HSA and negatively charged QDs (MPA-CdTe, NAC-CdTe, and GSH-CdTe), which was also reconfirmed by the increasing of the hydrodynamic radius of QDs. The K(a) values of the three negatively charged QDs are of the same order of magnitude, indicating that the interactions are related to the nanoparticle itself rather than the ligands. ΔH<0 and ΔS>0 implied that the electrostatic interactions play predominant roles in the adsorption process. Furthermore, it was also proven that QDs can induce the conformational changes of HSA from the CD spectra and the three-dimensional fluorescence spectra of HSA. However, our results demonstrate that the interaction mechanism between the positively charged QDs (CA-CdTe) and HSA is significantly different from negatively charged QDs. For CA-CdTe QDs, both the static and dynamic quenching occur within the investigated range of concentrations. According to the DLS results, some large-size agglomeration also emerged.

Interaction of human serum albumin with 10-hydroxycamptothecin: spectroscopic and molecular modeling studies.

In this work, fluorescence spectroscopy in combination with circular dichroism spectroscopy and molecular modeling was employed to investigate the binding of 10-hydroxycamptothecin (HCPT) to human serum albumin (HSA) under simulative physiological conditions. The experiment results showed that the fluorescence quenching of HSA by HCPT was a result of the formation of HCPT-HSA complex. The corresponding association constants (K (a)) between HCPT and HSA at four different temperatures were determined according to the modified Stern-Volmer equation. The results of thermodynamic parameters ΔG, ΔH, and ΔS indicated that hydrogen bonds and van der Waals forces played major roles for HCPT-HSA association. Site marker competitive displacement experiment indicated that the binding of HCPT to HSA primarily took place in sub-domain IIA (site I). Molecular docking study further confirmed the binding mode and the binding site obtained by fluorescence and site marker competitive experiments. The conformational investigation showed that the presence of HCPT decreased the α-helical content of HSA and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of HSA molecules.

Effect of Ce(III) on heat production of mitochondria isolated from hybrid rice.

The effect of cerium on mitochondria isolated from hybrid rice Shanyou 63 (Oryza sativa L) was investigated. Through in vivo culture, low dose Ce3+ promoted, but higher dose Ce3+, restrained mitochondrial heat production. However, through vitro incubation, Ce3+ showed only inhibitory action on mitochondrial energy turnover, the concentration required for 50% inhibition being 46.7 µM. In addition, Ce3+, like Ca2+, induced rice mitochondrial swelling and decreased membrane potential (△ψ), which was inhibited by the specific permeability transition inhibitor cyclosporine A (CsA). The induction approached a constant level while mitochondrial metabolism was fully prevented by Ce3+. These results demonstrated that cerium influenced rice mitochondria in vivo and in vitro via different action pathways, and the latter involved the opening of rice mitochondrial permeability.

Studies on the interaction between benzophenone and bovine serum albumin by spectroscopic methods.

The interaction between benzophenone (BP) and bovine serum albumin (BSA) was investigated by the methods of fluorescence spectroscopy combined with UV-Vis absorption and circular dichroism (CD) measurements under simulative physiological conditions. The experiment results showed that the fluorescence quenching of BSA by BP was resulted from the formation of a BP-BSA complex and the corresponding association constants (Ka) between BP and BSA at four different temperatures had been determined using the modified Stern-Volmer equation. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be -43.73 kJ mol(-1) and -53.05 J mol(-1) K(-1), respectively, which suggested that hydrogen bond and van der Waals force played major roles in stabilizing the BP-BSA complex. Site marker competitive experiments indicated that the binding of BP to BSA primarily took place in site I (sub-domain IIA). The conformational investigation showed that the presence of BP decreased the α-helical content of BSA and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.

Spectroscopic studies on the interaction of fluorine containing triazole with bovine serum albumin.

The binding of one fluorine including triazole (C(10)H(9)FN(4)S, FTZ) to bovine serum albumin (BSA) was studied by spectroscopic techniques including fluorescence spectroscopy, UV-Vis absorption, and circular dichroism (CD) spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by FTZ was the result of forming a complex of BSA-FTZ, and the binding constants (K (a)) at three different temperatures (298, 304, and 310 K) were 1.516 × 10(4), 1.627 × 10(4), and 1.711 × 10(4) mol L(-1), respectively, according to the modified Stern-Volmer equation. The thermodynamic parameters ΔH and ΔS were estimated to be 7.752 kJ mol(-1) and 125.217 J mol(-1) K(-1), respectively, indicating that hydrophobic interaction played a major role in stabilizing the BSA-FTZ complex. It was observed that site I was the main binding site for FTZ to BSA from the competitive experiments. The distance r between donor (BSA) and acceptor (FTZ) was calculated to be 7.42 nm based on the Förster theory of non-radioactive energy transfer. Furthermore, the analysis of fluorescence data and CD data revealed that the conformation of BSA changed upon the interaction with FTZ.

Studies on the interaction between benzidine and bovine serum albumin by spectroscopic methods.

The interaction between bovine serum albumin (BSA) and benzidine (BD) in aqueous solution was investigated by fluorescence spectroscopy, circular dichroism (CD) spectra and UV-Vis spectroscopy, as well as resonance light scattering spectroscopy (RLS). It was proved from fluorescence spectra that the fluorescence quenching of BSA by BD was a result of the formation of BD-BSA complex, and the binding constants (K (a)) were determined according to the modified Stern-Volmer equation. The enthalpy change (DeltaH) and entropy change (DeltaS) were calculated to be -34.11 kJ mol(-1) and -25.89 J mol(-1) K(-1), respectively, which implied that van der Waals force and hydrogen bond played predominant roles in the binding process. The addition of increasing BD to BSA solution caused the gradual enhancement in RLS intensity, exhibiting the forming of the aggregate. Moreover, the competitive experiments of site markers suggested that the binding site of BD to BSA was located in the region of subdomain IIA (sudlow site I). The distance (r) between the donor (BSA) and the acceptor (BD) was 4.44 nm based on the Förster theory of non-radioactive energy transfer. The results of synchronous fluorescence and CD spectra demonstrated the microenvironment and the secondary conformation of BSA were changed.

Spectroscopic studies on the binding of cobalt(II) 1,10-phenanthroline complex to bovine serum albumin.

The binding interaction of the cobalt(II) 1,10-phenanthroline complex (Co(phen) (3) (2+) , phen = 1,10-phenanthroline) with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-Vis absorption and circular dichroism measurements under simulative physiological conditions. The experiment results showed that the fluorescence intensity of BSA was dramatically decreased owing to the formation of Co(phen) (3) (2+) -BSA complex. The corresponding association constants (K (a)) between Co(phen) (3) (2+) and BSA at four different temperatures were calculated according to the modified Stern-Volmer equation. The enthalpy change (DeltaH degrees ) and entropy change (DeltaS degrees ) were calculated to be -2.73 kJ mol(-1) and 82.27 J mol(-1) K(-1), respectively, which suggested that electrostatic interaction and hydrophobic force played major roles in stabilizing the Co(phen) (3) (2+) -BSA complex. Site marker competitive experiments indicated that the binding of Co(phen) (3) (2+) to BSA primarily took place in site I of BSA. A value of 4.11 nm for the average distance r between Co(phen) (3) (2+) (acceptor) and tryptophan residues of BSA (donor) was derived from Förster's energy transfer theory. The conformational investigation showed that the presence of Co(phen) (3) (2+) resulted in the change of BSA secondary structure and induced the slight unfolding of the polypeptides of protein, which confirmed the microenvironment and conformational changes of BSA molecules.

Spectroscopic studies on the interaction of Congo Red with bovine serum albumin.

The binding interaction of Congo Red (CGR) with bovine serum albumin (BSA) was investigated by spectroscopic techniques including fluorescence spectroscopy, UV-vis absorption, and circular dichroism (CD) spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by CGR was the result of the formation of a BSA-CGR complex, and the corresponding binding constants (K(a)) at the four different temperatures (292, 298, 304, and 310K) were obtained according to the modified Stern-Volmer equation. The thermodynamic parameters DeltaH and DeltaS were calculated to be -12.67kJmol(-1) and 58.60Jmol(-1)K(-1), respectively, which suggested that both hydrophobic force and hydrogen bond played major roles in stabilizing the BSA-CGR complex. Site marker competitive experiments showed that the binding of CGR to BSA primarily took place in site I of BSA. The distance r between CGR (acceptor) and tryptophan residues of BSA (donor) was calculated to be 3.89nm based on Förster's non-radioactive energy transfer theory. The conformational investigation showed that the presence of CGR resulted in the change of BSA secondary structure and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.

Interaction of malachite green with bovine serum albumin: determination of the binding mechanism and binding site by spectroscopic methods.

The interaction between malachite green (MG) and bovine serum albumin (BSA) under simulative physiological conditions was investigated by the methods of fluorescence spectroscopy, UV-vis absorption and circular dichroism (CD) spectroscopy. Fluorescence data showed that the fluorescence quenching of BSA by MG was the result of the formation of the MG-BSA complex. According to the modified Stern-Volmer equation, the effective quenching constants (K(a)) between MG and BSA at four different temperatures were obtained to be 3.734 x 10(4), 3.264 x 10(4), 2.718 x 10(4), and 2.164 x 10(4)L mol(-1), respectively. The enthalpy change (Delta H) and entropy change (DeltaS) were calculated to be -27.25 kJ mol(-1) and -11.23 J mol(-1)K(-1), indicating that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. Site marker competitive experiments indicated that the binding of MG to BSA primarily took place in sub-domain IIA. The binding distance (r) between MG and the tryptophan residue of BSA was obtained to be 4.79 nm according to Förster theory of non-radioactive energy transfer. The conformational investigation showed that the presence of MG decreased the alpha-helical content of BSA (from 62.6% to 55.6%) and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.

Microcalorimetric investigation on effects of La(III) on metabolic activity of mitochondria isolated from hybrid rice.

Rare earth elements (REEs) have beneficial influence on plant growth and are widely used in agriculture practice, but little is known about the behavior of the REEs in mitochondria of plant cell. Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in mitochondria isolated from hybrid rice Liangyoupeijiu (Oryza sativa L.), and the effect of La(III) on its mitochondrial metabolism was investigated. From the obtained heat flux curves, the crucial parameters including as activity recovery rate constant (k) and maximum heat power (P(max)) were determined. Application of La(3+) in concentrations ranging from 0 to 120 microg/ml significantly increased k and P(max) values with the high point reaching 346 and 222% of the control, respectively. Concentrations from 140-150 microg/ml had the opposite effect. These results were consistent with previous reports on the effects of REEs on plant growth. It was concluded that the La-induced change of mitochondrial metabolic activity is a possible mechanism by which La(III) ions influences hybrid rice growth.

Microcalorimetric study of the effect of Ce(III) on metabolic activity of mitochondria isolated from indice rice 9311.

Rare earth elements (REEs) have beneficial influence on plant growth and are widely used in agriculture practice, but little is known about behavior of the REEs on mitochondria in plant cells. Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in mitochondria isolated from indice rice 9311 (Oryza sativa L.), and the effect of Ce(III) on mitochondrial metabolism was investigated. By analyzing the obtained heat flux curves, the crucial parameters such as activity recovery rate constant (k) and maximum heat power (P(m)) were investigated. Application of Ce3+ in concentrations ranging from 0 to 120 microg/ml significantly increased k and P(m) values, with the maximum reaching 261 and 180% of the control, respectively. Concentrations from 140 to 150 microg/ml had the opposite effect. These results were consistent with previous reports on the effects of REEs on plant growth. It was concluded that the Ce(III)-induced change of mitochondrial metabolic activity is a possible mechanism by which Ce(III) influenced indice rice 9311 growth.

Spectroscopic investigation of the interaction between copper (II) 2-oxo-propionic acid salicyloyl hydrazone complex and bovine serum albumin.

The interaction between copper (II) 2-oxo-propionic acid salicyloyl hydrazone (Cu(II)L) and bovine serum albumin (BSA) under physiological conditions was investigated by the methods of fluorescence spectroscopy, UV-Vis absorption, and circular dichroism spectroscopy. Fluorescence data showed that the fluorescence quenching of BSA by Cu(II)L was the result of the formation of the BSA-Cu(II)L complex. The apparent binding constants (K (a)) between Cu(II)L and BSA at four different temperatures were obtained according to the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS), for the reaction were calculated to be -80.79 kJ mol(-1) and -175.48 J mol(-1) K(-1) according to van't Hoff equation. The results indicated that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. The binding distance (r) between Cu(II)L and the tryptophan residue of BSA was obtained to be 4.1 nm according to Förster's nonradioactive energy transfer theory. The conformational investigation showed that the application of Cu(II)L increased the hydrophobicity of amino acid residues and decreased the alpha-helical content of BSA (from 62.71% to 37.31%), which confirmed some microenvironmental and conformational changes of BSA molecules.

Spectroscopic studies on the interaction of lanthanum(III) 2-oxo-propionic acid salicyloyl hydrazone complex with bovine serum albumin.

The interaction of lanthanum(III) 2-oxo-propionic acid salicyloyl hydrazone complex (La(III)L(2)) with bovine serum albumin (BSA) was studied under physiological conditions. Fluorescence spectroscopy in combination with UV-vis absorption and circular dichroism (CD) spectroscopy were used to investigate the binding mechanism, binding constants and conformational changes of BSA in the presence of La(III)L(2). It was found that the fluorescence quenching of BSA by La(III)L(2) resulted mainly from the formation of a La(III)L(2)-BSA complex. The enthalpy change (delta H) and entropy change (deltaS) were found to be -41.03 kJ/mol and -32.61 J/mol/K, respectively, which indicated that van der Waals' interactions and hydrogen bonds were the predominant intermolecular force in stabilizing the complex. The distance r between the donor (BSA) and acceptor (La(III)L(2)) was found to be 4.35 nm, according to Förster theory of non-radioactive energy transfer. Moreover, the conformational changes of BSA by La(III)L(2) were analysed by means of synchronous fluorescence spectra, CD and three-dimensional fluorescence spectra. The experiment results confirmed some microenvironmental and conformational changes of BSA molecules in the presence of La(III)L(2).