Alex Angerhofer | University of Florida (original) (raw)
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Papers by Alex Angerhofer
Medical Hypotheses, 2008
Humans have relatively low plasma ascorbate levels and high serum uric acid levels compared to mo... more Humans have relatively low plasma ascorbate levels and high serum uric acid levels compared to most mammals due to the presence of genetic mutations in L-gulonolactone oxidase and uricase, respectively. We review the major hypotheses for why these mutations may have occurred. In particular, we suggest that both mutations may have provided a survival advantage to early primates by helping maintain blood pressure during periods of dietary change and environmental stress. We further propose that these mutations have the inadvertent disadvantage of increasing our risk for hypertension and cardiovascular disease in today's society characterized by Western diet and increasing physical inactivity. Finally, we suggest that a ''planetary biology'' approach in which genetic changes are analyzed in relation to their biological action and historical context may provide the ideal approach towards understanding the biology of the past, present and future.
High-frequency EPR not only increases the g-resolution, but also the attainable time-resolution i... more High-frequency EPR not only increases the g-resolution, but also the attainable time-resolution in a transient/pulsed EPR experiment . For that reason we have built a multi-frequency super-heterodyne spectrometer with a sub-nanosecond detection time-resolution for transient EPR, which currently operates at 120 and 240 GHz. The design of this unique spectrometer is based largely on quasi-optical elements, resulting in very low
![Research paper thumbnail of Low oxidation potential conducting polymers based on 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5-dialkoxybenzenes](https://attachments.academia-assets.com/85851290/thumbnails/1.jpg)
](Synthetic Metals, 1999
Palladium<atalyzed coupling techniques have been used to prepare a series of 1,4-bis[2-(3,4-ethyl... more Palladium<atalyzed coupling techniques have been used to prepare a series of 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5~ialkoxybenzenes which can be polymerized chemically or electrochemically. The polymers have been characterized by electrochemistry, spectroelectrochemistry, in situ EPR electrochemistry, and in situ conductivity. The highly electron rich nature of these polymers leads to extremely low oxidation potentials (E,n,p=-0.15 to-0.35V vs. AgJAg'). Mild polymerization conditions can be used, resulting in fewer side reactions and more stable polymers; e.g. only a 25% loss in electroactivity occurs over 3000 redox cycles when switching polymer 2c. These polymers are stable over a broad potential range, allowing them to be used as modified electrode materials; for example, ferrocene can be repeatedly oxidized and reduced on the polymer surface. In situ EPR electrochemistry and in situ conductivity were used to better understand the polymer redox processes, which are solvent-dependent. Maximum conductivity is attained in the bipolaronic state, but stable polarons can be formed in certain solvents. The polymers are electrochromic, reversibly switching from red to blue upon oxidation with electronic bandgaps at co. 1.9 eV.
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 2001
ABSTRACT The magnetic field spin effect on photoluminescence of charge-transfer single crystal ca... more ABSTRACT The magnetic field spin effect on photoluminescence of charge-transfer single crystal caused by annihilation of triplet excitons and controlled by Zeeman and zero-field splitting (ZFS) interactions is investigated Phase transition related to reorientation of dibromo-anthracene molecules in the (x-y) plane of ZFS tensor of anthracene molecule is observed at T=205 K. When the temperature approaches the phase transition point at orientation of ZFS axis z parallel to the magnetic field the rate of spin-lattice relaxation dramatically increases and hence the magnitude of the magnetic field spin effect sharply drops down.
Journal of the American Chemical Society, 2008
Journal of Industrial Microbiology & Biotechnology, 2012
Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction... more Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction of molecular oxygen. While an archaeal laccase has only recently been described (LccA from the culture broth of Haloferax volcanii), this enzyme appears promising for biotechnology applications based on its robust bilirubin oxidase and laccase activities as well as its ability to withstand prolonged exposure to extreme conditions. To further optimize LccA productivity and develop an option for LccA purification from whole cells, the encoding gene was modified through deletion of the twin-arginine translocation motif and N-terminal propeptide, and the modified genes were expressed in Escherichia coli. With this approach, LccA was readily purified (overall yield up to 54 %) from the soluble fraction of E. coli as a 74-kDa monomer with syringaldazine oxidizing activity as high as 33 U mg−1. LccA proteins prepared from H. volcanii culture broth and the soluble fraction of E. coli cells were...
Applied Catalysis B: Environmental, 2008
This communication reports a size-controlled synthesis of water-soluble 2,2'-diphenyl-1-picry... more This communication reports a size-controlled synthesis of water-soluble 2,2'-diphenyl-1-picrylhydrazyl (DPPH) nanoparticles (NPs). These nanoparticles exhibit size-dependent absorption spectra and fast spin exchange-narrowed single-line EPR spectra. The linewidths of the EPR spectra of these water-soluble nanoparticles are approximately 1.5-1.8 G, which are equal or close to the narrowest line width (1.5 G) of the common DPPH standard in the form of water-insoluble microcrystals. In addition, these NPs are stable over a wide pH range of 3.0 to 10.0. These properties make these water-soluble DPPH NPs suitable for use as a new type of EPR standard, which is important for fundamental research and practical applications in fields such as the food industry and the life sciences. Furthermore, the DPPH NPs can potentially be used as a spin probe in biomedical studies.
The Journal of …, 2007
Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which cont... more Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which contains a Mn(II) ion coordinated by four identical conserved residues. The similarity between the two Mn(II) sites has precluded previous attempts to distinguish them spectroscopically and complicated efforts to understand the catalytic mechanism. A multifrequency cw-EPR approach has now enabled us to show that the two Mn ions can be distinguished on the basis of their differing fine structure parameters and to observe that acetate and formate bind to Mn(II) in only one of the two sites. The EPR evidence is consistent with the hypothesis that this Mn-binding site is located in the N-terminal domain, in agreement with predictions based on a recent X-ray structure of the enzyme.
Journal of Biological …, 2004
Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependen... more Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependent oxalate decarboxylase have recently been proposed involving high oxidation states of manganese. We have examined the oxalate decarboxylase from ...
Archives of Biochemistry and Biophysics, 2011
Oxalate oxidase (E.C. 1.2.3.4) catalyzes the oxygen-dependent oxidation of oxalate to carbon diox... more Oxalate oxidase (E.C. 1.2.3.4) catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction that is coupled with the formation of hydrogen peroxide. Although there is currently no structural information available for oxalate oxidase from Ceriporiopsis subvermispora (CsOxOx), sequence data and homology modeling indicate that it is the first manganese-containing bicupin enzyme identified that catalyzes this reaction. Interestingly,
Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction... more Laccases are multicopper oxidases that couple
the oxidation of phenolic polymers to the reduction of
molecular oxygen. While an archaeal laccase has only
recently been described (LccA from the culture broth of
Haloferax volcanii), this enzyme appears promising for
biotechnology applications based on its robust bilirubin
oxidase and laccase activities as well as its ability to
withstand prolonged exposure to extreme conditions. To
further optimize LccA productivity and develop an option
for LccA purification from whole cells, the encoding gene
was modified through deletion of the twin-arginine translocation motif and N-terminal propeptide, and the modified
genes were expressed in Escherichia coli. With this
approach, LccA was readily purified (overall yield up to
54 %) from the soluble fraction ofE. colias a 74-kDa
monomer with syringaldazine oxidizing activity as high as
33 U mg
-1
. LccA proteins prepared fromH. volcaniiculture
broth and the soluble fraction ofE. colicells were compared
by ICP-AES, EPR, DSC, CD, and UV–Vis spectroscopy and
found to have a similar folding pattern withTmvalues and a
rich b-sheet structure analogous to other multicopper oxidases. However, in contrast to theH. volcanii-purified LccA,
which was loaded with copper, copper was not fully incorporated into the type-I Cu center ofE. colipurified LccA,
thus, providing insight into avenues for further optimization
Medical Hypotheses, 2008
Humans have relatively low plasma ascorbate levels and high serum uric acid levels compared to mo... more Humans have relatively low plasma ascorbate levels and high serum uric acid levels compared to most mammals due to the presence of genetic mutations in L-gulonolactone oxidase and uricase, respectively. We review the major hypotheses for why these mutations may have occurred. In particular, we suggest that both mutations may have provided a survival advantage to early primates by helping maintain blood pressure during periods of dietary change and environmental stress. We further propose that these mutations have the inadvertent disadvantage of increasing our risk for hypertension and cardiovascular disease in today's society characterized by Western diet and increasing physical inactivity. Finally, we suggest that a ''planetary biology'' approach in which genetic changes are analyzed in relation to their biological action and historical context may provide the ideal approach towards understanding the biology of the past, present and future.
High-frequency EPR not only increases the g-resolution, but also the attainable time-resolution i... more High-frequency EPR not only increases the g-resolution, but also the attainable time-resolution in a transient/pulsed EPR experiment . For that reason we have built a multi-frequency super-heterodyne spectrometer with a sub-nanosecond detection time-resolution for transient EPR, which currently operates at 120 and 240 GHz. The design of this unique spectrometer is based largely on quasi-optical elements, resulting in very low
Synthetic Metals, 1999
Palladium<atalyzed coupling techniques have been used to prepare a series of 1,4-bis[2-(3,4-ethyl... more Palladium<atalyzed coupling techniques have been used to prepare a series of 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5~ialkoxybenzenes which can be polymerized chemically or electrochemically. The polymers have been characterized by electrochemistry, spectroelectrochemistry, in situ EPR electrochemistry, and in situ conductivity. The highly electron rich nature of these polymers leads to extremely low oxidation potentials (E,n,p=-0.15 to-0.35V vs. AgJAg'). Mild polymerization conditions can be used, resulting in fewer side reactions and more stable polymers; e.g. only a 25% loss in electroactivity occurs over 3000 redox cycles when switching polymer 2c. These polymers are stable over a broad potential range, allowing them to be used as modified electrode materials; for example, ferrocene can be repeatedly oxidized and reduced on the polymer surface. In situ EPR electrochemistry and in situ conductivity were used to better understand the polymer redox processes, which are solvent-dependent. Maximum conductivity is attained in the bipolaronic state, but stable polarons can be formed in certain solvents. The polymers are electrochromic, reversibly switching from red to blue upon oxidation with electronic bandgaps at co. 1.9 eV.
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 2001
ABSTRACT The magnetic field spin effect on photoluminescence of charge-transfer single crystal ca... more ABSTRACT The magnetic field spin effect on photoluminescence of charge-transfer single crystal caused by annihilation of triplet excitons and controlled by Zeeman and zero-field splitting (ZFS) interactions is investigated Phase transition related to reorientation of dibromo-anthracene molecules in the (x-y) plane of ZFS tensor of anthracene molecule is observed at T=205 K. When the temperature approaches the phase transition point at orientation of ZFS axis z parallel to the magnetic field the rate of spin-lattice relaxation dramatically increases and hence the magnitude of the magnetic field spin effect sharply drops down.
Journal of the American Chemical Society, 2008
Journal of Industrial Microbiology & Biotechnology, 2012
Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction... more Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction of molecular oxygen. While an archaeal laccase has only recently been described (LccA from the culture broth of Haloferax volcanii), this enzyme appears promising for biotechnology applications based on its robust bilirubin oxidase and laccase activities as well as its ability to withstand prolonged exposure to extreme conditions. To further optimize LccA productivity and develop an option for LccA purification from whole cells, the encoding gene was modified through deletion of the twin-arginine translocation motif and N-terminal propeptide, and the modified genes were expressed in Escherichia coli. With this approach, LccA was readily purified (overall yield up to 54 %) from the soluble fraction of E. coli as a 74-kDa monomer with syringaldazine oxidizing activity as high as 33 U mg−1. LccA proteins prepared from H. volcanii culture broth and the soluble fraction of E. coli cells were...
Applied Catalysis B: Environmental, 2008
This communication reports a size-controlled synthesis of water-soluble 2,2'-diphenyl-1-picry... more This communication reports a size-controlled synthesis of water-soluble 2,2'-diphenyl-1-picrylhydrazyl (DPPH) nanoparticles (NPs). These nanoparticles exhibit size-dependent absorption spectra and fast spin exchange-narrowed single-line EPR spectra. The linewidths of the EPR spectra of these water-soluble nanoparticles are approximately 1.5-1.8 G, which are equal or close to the narrowest line width (1.5 G) of the common DPPH standard in the form of water-insoluble microcrystals. In addition, these NPs are stable over a wide pH range of 3.0 to 10.0. These properties make these water-soluble DPPH NPs suitable for use as a new type of EPR standard, which is important for fundamental research and practical applications in fields such as the food industry and the life sciences. Furthermore, the DPPH NPs can potentially be used as a spin probe in biomedical studies.
The Journal of …, 2007
Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which cont... more Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which contains a Mn(II) ion coordinated by four identical conserved residues. The similarity between the two Mn(II) sites has precluded previous attempts to distinguish them spectroscopically and complicated efforts to understand the catalytic mechanism. A multifrequency cw-EPR approach has now enabled us to show that the two Mn ions can be distinguished on the basis of their differing fine structure parameters and to observe that acetate and formate bind to Mn(II) in only one of the two sites. The EPR evidence is consistent with the hypothesis that this Mn-binding site is located in the N-terminal domain, in agreement with predictions based on a recent X-ray structure of the enzyme.
Journal of Biological …, 2004
Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependen... more Several molecular mechanisms for cleavage of the oxalate carbon-carbon bond by manganese-dependent oxalate decarboxylase have recently been proposed involving high oxidation states of manganese. We have examined the oxalate decarboxylase from ...
Archives of Biochemistry and Biophysics, 2011
Oxalate oxidase (E.C. 1.2.3.4) catalyzes the oxygen-dependent oxidation of oxalate to carbon diox... more Oxalate oxidase (E.C. 1.2.3.4) catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction that is coupled with the formation of hydrogen peroxide. Although there is currently no structural information available for oxalate oxidase from Ceriporiopsis subvermispora (CsOxOx), sequence data and homology modeling indicate that it is the first manganese-containing bicupin enzyme identified that catalyzes this reaction. Interestingly,
Laccases are multicopper oxidases that couple the oxidation of phenolic polymers to the reduction... more Laccases are multicopper oxidases that couple
the oxidation of phenolic polymers to the reduction of
molecular oxygen. While an archaeal laccase has only
recently been described (LccA from the culture broth of
Haloferax volcanii), this enzyme appears promising for
biotechnology applications based on its robust bilirubin
oxidase and laccase activities as well as its ability to
withstand prolonged exposure to extreme conditions. To
further optimize LccA productivity and develop an option
for LccA purification from whole cells, the encoding gene
was modified through deletion of the twin-arginine translocation motif and N-terminal propeptide, and the modified
genes were expressed in Escherichia coli. With this
approach, LccA was readily purified (overall yield up to
54 %) from the soluble fraction ofE. colias a 74-kDa
monomer with syringaldazine oxidizing activity as high as
33 U mg
-1
. LccA proteins prepared fromH. volcaniiculture
broth and the soluble fraction ofE. colicells were compared
by ICP-AES, EPR, DSC, CD, and UV–Vis spectroscopy and
found to have a similar folding pattern withTmvalues and a
rich b-sheet structure analogous to other multicopper oxidases. However, in contrast to theH. volcanii-purified LccA,
which was loaded with copper, copper was not fully incorporated into the type-I Cu center ofE. colipurified LccA,
thus, providing insight into avenues for further optimization