In this work, a series of simple, rapid and effective photoelectrochemical methodologies have bee... more In this work, a series of simple, rapid and effective photoelectrochemical methodologies have been developed and successfully applied to the study of kinetic and thermodynamic characteristics of photocatalytic oxidation processes at TiO2 nanoparticulate films. As an application of the systematic studies of photocatalytic processes by photoelectrochemical techniques, a rapid, direct, absolute, environmental-friendly and accurate COD analysis method was successfully developed. In this work, the TiO2 nanoparticles colloid was prepared by the sol-gel method. The TiO2 nanoparticles were immobilized onto ITO conducting glass slides by dip-coating method. Thermal treatment was carried out to obtain nanoporous TiO2 films of different structures. At low calcination temperature (below 600°C), nanoporous TiO2 films of pure anatase phase were prepared. At high calcination temperature (above 600°C), nanoporous TiO2 films of mixed anatase and rutile phases were obtained. At these film electrodes,...
The aberrant autoxidation of norepinephrine (NE) in the presence of oxygen, which is accelerated ... more The aberrant autoxidation of norepinephrine (NE) in the presence of oxygen, which is accelerated by Fe(III), has been linked to the pathogenesis of the Parkinson's disease (PD). Adenosine triphosphate (ATP), as a neurotransmitter whose release can be stimulated by tissue damage and oxidative stress, is co-stored and often co-released with NE in presynaptic terminals. We have shown previously that ATP inhibits the iron-catalyzed dopamine oxidation, thereby decreasing the production of certain neurotoxins such as 6-hydroxydopamine. Whether ATP plays a similar role in Fe(III)-catalyzed NE oxidation and how it maintains the NE stability have not been investigated. Here, we studied the coordination in a ternary complex among NE, Fe(III), and ATP, and found that Fe(III) is coordinated as a octahedral center by NE and ATP. Voltammetry and mass spectrometry were employed to examine this ternary complex's modulation of the NE autoxidation. NE-Fe(III)-ATP plays a protective role to modulate the autoxidation and Fe(III)-catalyzed oxidation of NE. The ternary complex can be detected in the substantia nigra (SN), locus coeruleus (LC), and striatum regions of C57BL/6 wild-type mice. In contrast, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse brains displayed a significant decrease of the ternary complex in the SN region and an increase in the LC and striatum areas. We posit that the ternary complex is produced by noradrenergic neurons as a protective regulator against neuronal damage and oxidative stress, contributing to the lower vulnerability of LC neurons with respect to that of SN neurons.
t-Darpp, one of two protein isoforms encoded by the PPP1R1B gene, is overexpressed in gastric, es... more t-Darpp, one of two protein isoforms encoded by the PPP1R1B gene, is overexpressed in gastric, esophageal, colon, prostate, and breast cancers; and confers resistance to trastuzumab in Her2+ breast cancer cells. To gain insight into the trastuzumab-resistance mechanism of t-Darpp, we studied its structure, oligomerization status, metal-binding properties, and sites of phosphorylation. Circular dichroism spectroscopy analysis showed that recombinant t-Darpp exhibits 12% alpha helix, 29% beta strand, 24% beta turn and 35% random coil character at 25°C. Upon mild heat treatment (50°C for five min) the secondary structure does not appreciably change. Metal ion-binding analyses through inductively coupled plasma-mass spectrometry and graphite furnace-atomic absorption indicated that t-Darpp co-purifies with calcium, but not other metals commonly found in biological systems. The T75 site, critical for t-Darpp activation of the Akt signaling pathway, is a substrate for phosphorylation by c...
ABSTRACTt-Darpp is a protein encoded by the PPP1R1B gene and is expressed in breast, colon, esoph... more ABSTRACTt-Darpp is a protein encoded by the PPP1R1B gene and is expressed in breast, colon, esophageal, gastric, and prostate cancers, as well as in normal adult brain striatal cells. Overexpression of t-Darpp in cultured cells leads to increased protein kinase A activity and increased phosphorylation of AKT (protein kinase B). In HER2+ breast cancer cells t-Darpp confers resistance to the chemotherapeutic agent trastuzumab. To shed light on t-Darpp function, we studied its secondary structure, oligomerization status, metal-binding properties, and phosphorylation by cyclin dependent kinases 1 and 5. t-Darpp exhibits 12% alpha helix, 29% beta strand, 24% beta turn and 35% random coil structures. t-Darpp binds to calcium, but not to other metals commonly found in biological systems. The T39 site, critical for t-Darpp activation of the AKT signaling pathway, is a substrate for phosphorylation by cyclin-dependent kinase 1 (CDK1) and cyclin-dependent kinase 5 (CDK5). Gel filtration chrom...
Copper is an essential metal in all organisms. Reliably quantifying and identifying the copper co... more Copper is an essential metal in all organisms. Reliably quantifying and identifying the copper content and oxidation state is crucial, since the information is essential to understanding protein structure and function. Chromophoric ligands, such as Bathocuproine (BC) and its water-soluble analog, Bathocuproinedisulfonic acid (BCS), preferentially bind Cu(I) over Cu(II), and therefore have been widely used as optical probes to determine the oxidation state of copper bound by biomolecules. However, the BCS assay is commonly misused, leading to erroneous conclusions regarding the role of copper in biological processes. By measuring the redox potential of Cu(II)-BCS2 and conducting UV-vis absorption measurements in the presence of oxidizable amino acids, the thermodynamic origin of the potential artifacts becomes evident. The BCS assay was improved by introducing a strong Cu(II) chelator EDTA prior to the addition of BCS to prevent interference that might arise from Cu(II) present in the sample. The strong Cu(II) chelator rids of all the potential errors inherent in the conventional BCS assay. Applications of the improved assay to peptides and protein containing oxidizable amino acid residues confirm that free Cu(II) no longer leads to artifacts, thereby resolving issues related to this persistently misused colorimetric assay of Cu(I) in biological systems.
In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔGreg (0) ≥0.5 eV) i... more In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔGreg (0) ≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy-conversion efficiency of state-of-art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. By using Ru(dcbpy)(bpy)2 (2+) as the dye and Ru(bpy)2 (MeIm)2 (3+//2+) as the redox couple, a short-circuit current (Jsc ) of 4 mA cm(-2) and an open-circuit voltage (Voc ) of 0.9 V were obtained with a ΔGreg (0) of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2 (SCN)2 (1+/0) (ΔGreg (0) =0.0 eV), which produced an Jsc of 2.5 mA cm(-2) and Voc of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof-of-concept study demonstrates that high Voc values can be attained by significantly curtailing the dye-regeneration force.
In this work, a series of simple, rapid and effective photoelectrochemical methodologies have bee... more In this work, a series of simple, rapid and effective photoelectrochemical methodologies have been developed and successfully applied to the study of kinetic and thermodynamic characteristics of photocatalytic oxidation processes at TiO2 nanoparticulate films. As an application of the systematic studies of photocatalytic processes by photoelectrochemical techniques, a rapid, direct, absolute, environmental-friendly and accurate COD analysis method was successfully developed. In this work, the TiO2 nanoparticles colloid was prepared by the sol-gel method. The TiO2 nanoparticles were immobilized onto ITO conducting glass slides by dip-coating method. Thermal treatment was carried out to obtain nanoporous TiO2 films of different structures. At low calcination temperature (below 600°C), nanoporous TiO2 films of pure anatase phase were prepared. At high calcination temperature (above 600°C), nanoporous TiO2 films of mixed anatase and rutile phases were obtained. At these film electrodes,...
The aberrant autoxidation of norepinephrine (NE) in the presence of oxygen, which is accelerated ... more The aberrant autoxidation of norepinephrine (NE) in the presence of oxygen, which is accelerated by Fe(III), has been linked to the pathogenesis of the Parkinson's disease (PD). Adenosine triphosphate (ATP), as a neurotransmitter whose release can be stimulated by tissue damage and oxidative stress, is co-stored and often co-released with NE in presynaptic terminals. We have shown previously that ATP inhibits the iron-catalyzed dopamine oxidation, thereby decreasing the production of certain neurotoxins such as 6-hydroxydopamine. Whether ATP plays a similar role in Fe(III)-catalyzed NE oxidation and how it maintains the NE stability have not been investigated. Here, we studied the coordination in a ternary complex among NE, Fe(III), and ATP, and found that Fe(III) is coordinated as a octahedral center by NE and ATP. Voltammetry and mass spectrometry were employed to examine this ternary complex's modulation of the NE autoxidation. NE-Fe(III)-ATP plays a protective role to modulate the autoxidation and Fe(III)-catalyzed oxidation of NE. The ternary complex can be detected in the substantia nigra (SN), locus coeruleus (LC), and striatum regions of C57BL/6 wild-type mice. In contrast, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse brains displayed a significant decrease of the ternary complex in the SN region and an increase in the LC and striatum areas. We posit that the ternary complex is produced by noradrenergic neurons as a protective regulator against neuronal damage and oxidative stress, contributing to the lower vulnerability of LC neurons with respect to that of SN neurons.
t-Darpp, one of two protein isoforms encoded by the PPP1R1B gene, is overexpressed in gastric, es... more t-Darpp, one of two protein isoforms encoded by the PPP1R1B gene, is overexpressed in gastric, esophageal, colon, prostate, and breast cancers; and confers resistance to trastuzumab in Her2+ breast cancer cells. To gain insight into the trastuzumab-resistance mechanism of t-Darpp, we studied its structure, oligomerization status, metal-binding properties, and sites of phosphorylation. Circular dichroism spectroscopy analysis showed that recombinant t-Darpp exhibits 12% alpha helix, 29% beta strand, 24% beta turn and 35% random coil character at 25°C. Upon mild heat treatment (50°C for five min) the secondary structure does not appreciably change. Metal ion-binding analyses through inductively coupled plasma-mass spectrometry and graphite furnace-atomic absorption indicated that t-Darpp co-purifies with calcium, but not other metals commonly found in biological systems. The T75 site, critical for t-Darpp activation of the Akt signaling pathway, is a substrate for phosphorylation by c...
ABSTRACTt-Darpp is a protein encoded by the PPP1R1B gene and is expressed in breast, colon, esoph... more ABSTRACTt-Darpp is a protein encoded by the PPP1R1B gene and is expressed in breast, colon, esophageal, gastric, and prostate cancers, as well as in normal adult brain striatal cells. Overexpression of t-Darpp in cultured cells leads to increased protein kinase A activity and increased phosphorylation of AKT (protein kinase B). In HER2+ breast cancer cells t-Darpp confers resistance to the chemotherapeutic agent trastuzumab. To shed light on t-Darpp function, we studied its secondary structure, oligomerization status, metal-binding properties, and phosphorylation by cyclin dependent kinases 1 and 5. t-Darpp exhibits 12% alpha helix, 29% beta strand, 24% beta turn and 35% random coil structures. t-Darpp binds to calcium, but not to other metals commonly found in biological systems. The T39 site, critical for t-Darpp activation of the AKT signaling pathway, is a substrate for phosphorylation by cyclin-dependent kinase 1 (CDK1) and cyclin-dependent kinase 5 (CDK5). Gel filtration chrom...
Copper is an essential metal in all organisms. Reliably quantifying and identifying the copper co... more Copper is an essential metal in all organisms. Reliably quantifying and identifying the copper content and oxidation state is crucial, since the information is essential to understanding protein structure and function. Chromophoric ligands, such as Bathocuproine (BC) and its water-soluble analog, Bathocuproinedisulfonic acid (BCS), preferentially bind Cu(I) over Cu(II), and therefore have been widely used as optical probes to determine the oxidation state of copper bound by biomolecules. However, the BCS assay is commonly misused, leading to erroneous conclusions regarding the role of copper in biological processes. By measuring the redox potential of Cu(II)-BCS2 and conducting UV-vis absorption measurements in the presence of oxidizable amino acids, the thermodynamic origin of the potential artifacts becomes evident. The BCS assay was improved by introducing a strong Cu(II) chelator EDTA prior to the addition of BCS to prevent interference that might arise from Cu(II) present in the sample. The strong Cu(II) chelator rids of all the potential errors inherent in the conventional BCS assay. Applications of the improved assay to peptides and protein containing oxidizable amino acid residues confirm that free Cu(II) no longer leads to artifacts, thereby resolving issues related to this persistently misused colorimetric assay of Cu(I) in biological systems.
In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔGreg (0) ≥0.5 eV) i... more In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔGreg (0) ≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy-conversion efficiency of state-of-art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. By using Ru(dcbpy)(bpy)2 (2+) as the dye and Ru(bpy)2 (MeIm)2 (3+//2+) as the redox couple, a short-circuit current (Jsc ) of 4 mA cm(-2) and an open-circuit voltage (Voc ) of 0.9 V were obtained with a ΔGreg (0) of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2 (SCN)2 (1+/0) (ΔGreg (0) =0.0 eV), which produced an Jsc of 2.5 mA cm(-2) and Voc of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof-of-concept study demonstrates that high Voc values can be attained by significantly curtailing the dye-regeneration force.
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