... A Diffuse Reflectance Laser Flash Photolysis Study' IK Lednev? N. Mathivanan, and LJ Joh... more ... A Diffuse Reflectance Laser Flash Photolysis Study' IK Lednev? N. Mathivanan, and LJ Johnston; Steacie Institute for Molecular Sciences, National Research Council, Ottawa, Ontario, Canada KIA OR6 Received: April 29, 1994; In Final Form: August 13, 1994@ ...
Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventio... more Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventional biophysical techniques including solution NMR and X-ray crystallography for structural characterization of fibrils is limited because they are neither crystalline nor soluble. The Bayesian approach was utilized for extracting the deep UV resonance Raman (DUVRR) spectrum of the lysozyme fibrillar beta-sheet based on the hydrogen-deuterium exchange spectral data.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Langmuir-Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye con... more Langmuir-Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye containing a l,lO-dithia-l&crown-6 ether group have been found to complex with 'soft' polarisable ions such as Ag+ and Hg2+ in water. The films exhibited high sensitivity (stabilip constant of complex formation KPI l o 5 M-') and high selectivity (e.g. K(Ag+)/K(Pb2+) > 10 ) compared with aqueous solutions of similar ionophores. This was attributed to the predominant formation of complexes with ligand-cation stoichiometries of 2:l in the films.
Langmuir-Blodgett films of a benzothiazolium styryl dye containing al, lO-dithia-l8-crown-6 ether... more Langmuir-Blodgett films of a benzothiazolium styryl dye containing al, lO-dithia-l8-crown-6 ether group have been built-up from aqueous subphases of differing pH. The kinetics of the chromoionophore aggregate formation in a bilayer immersed in acidic water have been ...
Abstract We have developed photochemically controlled photonic crystals that may be useful in nov... more Abstract We have developed photochemically controlled photonic crystals that may be useful in novel recordable and erasable memories and/or display devices. These materials can operate in the UV, visible, or near-IR spectral regions. Information is recorded and ...
Spectrochimica Acta Part a Molecular and Biomolecular Spectroscopy, 1997
Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) ... more Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) spectra of two benzothiazolium styryl dyes containing a crown ether ring with sulfur and oxygen heteroatoms have been obtained at low concentration (10 -5-10 -7 M) in the presence of silver colloids. A preliminary assignment of the observed bands to particular vibrational modes has been made by comparison of infrared (IR), normal Raman (R) and SERS data obtained from thiacrown ether and benzothiazolium molecular fragments with SERRS spectra of a benzothiazolium styryl dye containing a normal crown ether ring and with assignments reported previously for related molecules. The results indicate that the sulfur atoms of both the benzothiazolium and the dithiacrown ether groups participate in adsorption at the silver surface; possible models of adsorption of these dyes and their fragments are discussed.
Http Dx Doi Org 10 1080 07391102 2013 786388, 2013
ABSTRACT Amyloid fibrils are associated with many neurodegenerative diseases. All known amyloids ... more ABSTRACT Amyloid fibrils are associated with many neurodegenerative diseases. All known amyloids including pathogenic and nonpathogenic forms display functional and structural heterogeneity (polymorphism) which determines the level of their toxicity. Despite a significant biological and biomedical importance, the nature of the amyloid fibril polymorphism remains elusive. We utilized for the first time three most advanced vibrational techniques to probe the core, the surface, and supramolecular chirality of fibril polymorphs. A new type of folding, aggregation phenomenon, spontaneous refolding from one polymorph to another, was discovered (Kurouski, Lauro et al., 2010). Hydrogen–deuterium exchange deep UV resonance Raman spectroscopy (Oladepo, Xiong et al., 2012) combined with advanced statistical analysis (Shashilov & Lednev, 2010) allowed for structural characterization of the highly ordered cross-β core of amyloid fibrils. We reported several examples showing significant variations in the core structure for fibril polymorphs. Amyloid fibrils are generally composed of several protofibrils and may adopt variable morphologies, such as twisted ribbons or flat-like sheets. We discovered the existence of another level of amyloid polymorphism, namely, that associated with fibril supramolecular chirality. Two chiral polymorphs of insulin, which can be controllably grown by means of small pH variations, exhibit opposite signs of vibrational circular dichroism (VCD) spectra (Kurouski, Dukor et al. 2012). VCD supramolecular chirality is correlated not only by the apparent fibril handedness but also by the sense of supramolecular chirality from a deeper level of chiral organization at the protofilament level of fibril structure. A small pH change initiates spontaneous transformation of insulin fibrils from one polymorph to another. As a result, fibril supramolecular chirality overturns both accompanying morphological and structural changes (Kurouski, Dukor et al. 2012). No conventional methods could probe the fibril surface despite its significant role in the biological activity. We utilized tip-enhanced Raman spectroscopy (TERS) to characterize the surface structure of an individual fibril due to a high depth and lateral spatial resolution of the method in the nanometer range (Kurouski, Deckert-Gaudig et al. 2012). It was found that the surface is strongly heterogeneous and consists of clusters with various protein conformations and amino acid composition.
The investigation of complex formation between a bicyclic diamide, a novel chelating agent for la... more The investigation of complex formation between a bicyclic diamide, a novel chelating agent for lanthanides and actinides, and lutetium in an acetonitrile solution is reported. A free ligand and its lutetium complexes showed weak, noncharacteristic near-UV absorption and no fluorescence, which limited the application of absorption and fluorescence spectroscopies for studying this system. Deep-UV Raman spectroscopy combined with chemometric analysis was shown to be a powerful tool for quantitative characterization of multiple equilibria between lutetium and a bicyclic diamide. Several chemometric methods were utilized for a comparative analysis of Raman spectroscopic data. It was found that a recently developed stepwise maximum angle calculation algorithm followed by alternative least squares (ALS) was more efficient than the commonly used combination of evolving factor analysis and ALS methods, especially when little or no information about the system composition and the spectra of individual components was available. A free ligand and 1:1, 1:2, and 1:3 metal-ligand complexes were distinguished in a bicyclic diamide-lutetium solution. The composition evolution of the solution during the course of titration with lutetium was described, and the stepwise stability constants of complex formation, K(1):K(2) = 0.80 +/- 0.15 (K(1,2) > 10(8) M(-1)) and K(3) = (5.5 +/- 1) x 10(3) M(-1), were estimated.
The photochemical behavior of Langmuir-Blodgett films built up from an amphiphilic benzothiazoliu... more The photochemical behavior of Langmuir-Blodgett films built up from an amphiphilic benzothiazolium styryl dye containing a l,lO-dithia-l8-crown-6 ether group, both in free form and complexed with Ag+ cations, has been studied. The isomerization reaction was slower in the films by 2 orders of magnitude relative to the solution and caused the decomposition of chromoionophore aggregates. Prolonged photolysis of the films with visible light (1 > 420 nm) resulted in an almost complete cycloaddition reaction with the formation of a cyclobutane adduct. The photoprocess was found to be partially reversible on exposure to U V light (1 = 310 nm).
were produced depending on the fibrillation processes. The polymorphism resulting in formation of... more were produced depending on the fibrillation processes. The polymorphism resulting in formation of curly (CAF) and straight amyloid fibrils (SAF) was respectively achieved with the centrifugal membrane filtration of the preformed a-synuclein oligomers and the agitated incubation of its monomeric form. It is demonstrated that the production of CAF and SAF represents two parallel mechanisms of amyloidogenesis via double-concerted and nucleationdependent fibrillation process, respectively. Differences in their secondary structures of the polymorphs have been suggested to be responsible for their characteristic morphologies with significant variations in physical properties, which were inherited for two consecutive generations to the daughter and granddaughter fibrils by self-propagation property. Accumulation of highly flexible and mechanically strong CAF eventually produced the hydrogel composed of the three-dimensional fibrillar network in fine nano-scale. The amyloid hydrogel was proven to be a suitable nanomatrix for enzyme entrapment, protecting the immobilized enzyme from the activity decrease due to repetitive catalytic reactions and heat treatment. Therefore, the nanoscaled fibrillar network of CAF is expected to be employed for various future applications in nanobiotechnology including drug delivery, tissue engineering and biosensor development.
The influence of electrostatic interactions on protein amyloidogenesis has been investigated usin... more The influence of electrostatic interactions on protein amyloidogenesis has been investigated using de novo designed repetitive polypeptides YEHK21 [GH6[(GA)3GY(GA)3GE(GA)3GY(GA)3GE]21GAH6] and YE8 [GH6[(GA)3GY(GA)3GE]8GAH6]. The beta-sheet forming polypeptides were designed with identical beta-strands but with variable substitution at the turns that enable precise location of charged residues (Topilina et al. Biopolymers 2007, 86 (4), 261-264; Topilina et al. Biopolymers 2010, submitted for publication; Topilina et al. Biomacromolecules 2006, 7 (4), 1104-11). Solubility, folding, and aggregation of YEHK21 and YE8 were shown to be controlled by charge distribution. Under those conditions favoring the development of charge, YEHK21 and YE8 have significant propensities to form intermolecular beta-sheet assemblies illustrating the potential of charged polypeptide chains to form ordered amyloid aggregates even in the absence of additional environmental factors such as the presence of polyelectrolytes, salts, and so on.
Spectrochimica Acta Part a Molecular Spectroscopy, Jun 1, 1992
Resonance and preresonance Raman spectra have been obtained in the region 400-1700 cm -1 for some... more Resonance and preresonance Raman spectra have been obtained in the region 400-1700 cm -1 for some benzothiazolium and indolinium steryl dyes containing a crown ether ring. Spectra arising from the trans isomers are observed selectively due to the resonance effect, and the principal features can be attributed to modes of the central conjugated PhN +CCCPh unit present in each of these molecules. Complex formation between the dye molecules and Mg 2+ in acetonitrile solution results in intramolecular electron transfer. This is observed in the Raman spectra as a downshift of a band assigned to PhO vibration in the crown ether unit, and upshifts of several bands associated with the PhN +CCCPh unit, including the phenyl ring, CC and +NC stretches. The results demonstrate the sensitivity of the Raman spectra to changes in the structure and bonding within these photochromic complexing agents on binding to metal ions, and indicate that they may serve as a useful probe for the complicated photoisomerization and complexation reactions of these interesting systems.
The new tetrathiafulvalene derivative 1, functionalised with an azobenzene substituent, has been ... more The new tetrathiafulvalene derivative 1, functionalised with an azobenzene substituent, has been synthesised. Cyclic voltammetric and spectroelectrochemical studies in solution demonstrate the reversible formation of the radical cation of 1. UVVIS spectroscopy suggests that ...
... A Diffuse Reflectance Laser Flash Photolysis Study' IK Lednev? N. Mathivanan, and LJ Joh... more ... A Diffuse Reflectance Laser Flash Photolysis Study' IK Lednev? N. Mathivanan, and LJ Johnston; Steacie Institute for Molecular Sciences, National Research Council, Ottawa, Ontario, Canada KIA OR6 Received: April 29, 1994; In Final Form: August 13, 1994@ ...
Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventio... more Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventional biophysical techniques including solution NMR and X-ray crystallography for structural characterization of fibrils is limited because they are neither crystalline nor soluble. The Bayesian approach was utilized for extracting the deep UV resonance Raman (DUVRR) spectrum of the lysozyme fibrillar beta-sheet based on the hydrogen-deuterium exchange spectral data.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Langmuir-Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye con... more Langmuir-Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye containing a l,lO-dithia-l&crown-6 ether group have been found to complex with 'soft' polarisable ions such as Ag+ and Hg2+ in water. The films exhibited high sensitivity (stabilip constant of complex formation KPI l o 5 M-') and high selectivity (e.g. K(Ag+)/K(Pb2+) > 10 ) compared with aqueous solutions of similar ionophores. This was attributed to the predominant formation of complexes with ligand-cation stoichiometries of 2:l in the films.
Langmuir-Blodgett films of a benzothiazolium styryl dye containing al, lO-dithia-l8-crown-6 ether... more Langmuir-Blodgett films of a benzothiazolium styryl dye containing al, lO-dithia-l8-crown-6 ether group have been built-up from aqueous subphases of differing pH. The kinetics of the chromoionophore aggregate formation in a bilayer immersed in acidic water have been ...
Abstract We have developed photochemically controlled photonic crystals that may be useful in nov... more Abstract We have developed photochemically controlled photonic crystals that may be useful in novel recordable and erasable memories and/or display devices. These materials can operate in the UV, visible, or near-IR spectral regions. Information is recorded and ...
Spectrochimica Acta Part a Molecular and Biomolecular Spectroscopy, 1997
Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) ... more Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) spectra of two benzothiazolium styryl dyes containing a crown ether ring with sulfur and oxygen heteroatoms have been obtained at low concentration (10 -5-10 -7 M) in the presence of silver colloids. A preliminary assignment of the observed bands to particular vibrational modes has been made by comparison of infrared (IR), normal Raman (R) and SERS data obtained from thiacrown ether and benzothiazolium molecular fragments with SERRS spectra of a benzothiazolium styryl dye containing a normal crown ether ring and with assignments reported previously for related molecules. The results indicate that the sulfur atoms of both the benzothiazolium and the dithiacrown ether groups participate in adsorption at the silver surface; possible models of adsorption of these dyes and their fragments are discussed.
Http Dx Doi Org 10 1080 07391102 2013 786388, 2013
ABSTRACT Amyloid fibrils are associated with many neurodegenerative diseases. All known amyloids ... more ABSTRACT Amyloid fibrils are associated with many neurodegenerative diseases. All known amyloids including pathogenic and nonpathogenic forms display functional and structural heterogeneity (polymorphism) which determines the level of their toxicity. Despite a significant biological and biomedical importance, the nature of the amyloid fibril polymorphism remains elusive. We utilized for the first time three most advanced vibrational techniques to probe the core, the surface, and supramolecular chirality of fibril polymorphs. A new type of folding, aggregation phenomenon, spontaneous refolding from one polymorph to another, was discovered (Kurouski, Lauro et al., 2010). Hydrogen–deuterium exchange deep UV resonance Raman spectroscopy (Oladepo, Xiong et al., 2012) combined with advanced statistical analysis (Shashilov & Lednev, 2010) allowed for structural characterization of the highly ordered cross-β core of amyloid fibrils. We reported several examples showing significant variations in the core structure for fibril polymorphs. Amyloid fibrils are generally composed of several protofibrils and may adopt variable morphologies, such as twisted ribbons or flat-like sheets. We discovered the existence of another level of amyloid polymorphism, namely, that associated with fibril supramolecular chirality. Two chiral polymorphs of insulin, which can be controllably grown by means of small pH variations, exhibit opposite signs of vibrational circular dichroism (VCD) spectra (Kurouski, Dukor et al. 2012). VCD supramolecular chirality is correlated not only by the apparent fibril handedness but also by the sense of supramolecular chirality from a deeper level of chiral organization at the protofilament level of fibril structure. A small pH change initiates spontaneous transformation of insulin fibrils from one polymorph to another. As a result, fibril supramolecular chirality overturns both accompanying morphological and structural changes (Kurouski, Dukor et al. 2012). No conventional methods could probe the fibril surface despite its significant role in the biological activity. We utilized tip-enhanced Raman spectroscopy (TERS) to characterize the surface structure of an individual fibril due to a high depth and lateral spatial resolution of the method in the nanometer range (Kurouski, Deckert-Gaudig et al. 2012). It was found that the surface is strongly heterogeneous and consists of clusters with various protein conformations and amino acid composition.
The investigation of complex formation between a bicyclic diamide, a novel chelating agent for la... more The investigation of complex formation between a bicyclic diamide, a novel chelating agent for lanthanides and actinides, and lutetium in an acetonitrile solution is reported. A free ligand and its lutetium complexes showed weak, noncharacteristic near-UV absorption and no fluorescence, which limited the application of absorption and fluorescence spectroscopies for studying this system. Deep-UV Raman spectroscopy combined with chemometric analysis was shown to be a powerful tool for quantitative characterization of multiple equilibria between lutetium and a bicyclic diamide. Several chemometric methods were utilized for a comparative analysis of Raman spectroscopic data. It was found that a recently developed stepwise maximum angle calculation algorithm followed by alternative least squares (ALS) was more efficient than the commonly used combination of evolving factor analysis and ALS methods, especially when little or no information about the system composition and the spectra of individual components was available. A free ligand and 1:1, 1:2, and 1:3 metal-ligand complexes were distinguished in a bicyclic diamide-lutetium solution. The composition evolution of the solution during the course of titration with lutetium was described, and the stepwise stability constants of complex formation, K(1):K(2) = 0.80 +/- 0.15 (K(1,2) > 10(8) M(-1)) and K(3) = (5.5 +/- 1) x 10(3) M(-1), were estimated.
The photochemical behavior of Langmuir-Blodgett films built up from an amphiphilic benzothiazoliu... more The photochemical behavior of Langmuir-Blodgett films built up from an amphiphilic benzothiazolium styryl dye containing a l,lO-dithia-l8-crown-6 ether group, both in free form and complexed with Ag+ cations, has been studied. The isomerization reaction was slower in the films by 2 orders of magnitude relative to the solution and caused the decomposition of chromoionophore aggregates. Prolonged photolysis of the films with visible light (1 > 420 nm) resulted in an almost complete cycloaddition reaction with the formation of a cyclobutane adduct. The photoprocess was found to be partially reversible on exposure to U V light (1 = 310 nm).
were produced depending on the fibrillation processes. The polymorphism resulting in formation of... more were produced depending on the fibrillation processes. The polymorphism resulting in formation of curly (CAF) and straight amyloid fibrils (SAF) was respectively achieved with the centrifugal membrane filtration of the preformed a-synuclein oligomers and the agitated incubation of its monomeric form. It is demonstrated that the production of CAF and SAF represents two parallel mechanisms of amyloidogenesis via double-concerted and nucleationdependent fibrillation process, respectively. Differences in their secondary structures of the polymorphs have been suggested to be responsible for their characteristic morphologies with significant variations in physical properties, which were inherited for two consecutive generations to the daughter and granddaughter fibrils by self-propagation property. Accumulation of highly flexible and mechanically strong CAF eventually produced the hydrogel composed of the three-dimensional fibrillar network in fine nano-scale. The amyloid hydrogel was proven to be a suitable nanomatrix for enzyme entrapment, protecting the immobilized enzyme from the activity decrease due to repetitive catalytic reactions and heat treatment. Therefore, the nanoscaled fibrillar network of CAF is expected to be employed for various future applications in nanobiotechnology including drug delivery, tissue engineering and biosensor development.
The influence of electrostatic interactions on protein amyloidogenesis has been investigated usin... more The influence of electrostatic interactions on protein amyloidogenesis has been investigated using de novo designed repetitive polypeptides YEHK21 [GH6[(GA)3GY(GA)3GE(GA)3GY(GA)3GE]21GAH6] and YE8 [GH6[(GA)3GY(GA)3GE]8GAH6]. The beta-sheet forming polypeptides were designed with identical beta-strands but with variable substitution at the turns that enable precise location of charged residues (Topilina et al. Biopolymers 2007, 86 (4), 261-264; Topilina et al. Biopolymers 2010, submitted for publication; Topilina et al. Biomacromolecules 2006, 7 (4), 1104-11). Solubility, folding, and aggregation of YEHK21 and YE8 were shown to be controlled by charge distribution. Under those conditions favoring the development of charge, YEHK21 and YE8 have significant propensities to form intermolecular beta-sheet assemblies illustrating the potential of charged polypeptide chains to form ordered amyloid aggregates even in the absence of additional environmental factors such as the presence of polyelectrolytes, salts, and so on.
Spectrochimica Acta Part a Molecular Spectroscopy, Jun 1, 1992
Resonance and preresonance Raman spectra have been obtained in the region 400-1700 cm -1 for some... more Resonance and preresonance Raman spectra have been obtained in the region 400-1700 cm -1 for some benzothiazolium and indolinium steryl dyes containing a crown ether ring. Spectra arising from the trans isomers are observed selectively due to the resonance effect, and the principal features can be attributed to modes of the central conjugated PhN +CCCPh unit present in each of these molecules. Complex formation between the dye molecules and Mg 2+ in acetonitrile solution results in intramolecular electron transfer. This is observed in the Raman spectra as a downshift of a band assigned to PhO vibration in the crown ether unit, and upshifts of several bands associated with the PhN +CCCPh unit, including the phenyl ring, CC and +NC stretches. The results demonstrate the sensitivity of the Raman spectra to changes in the structure and bonding within these photochromic complexing agents on binding to metal ions, and indicate that they may serve as a useful probe for the complicated photoisomerization and complexation reactions of these interesting systems.
The new tetrathiafulvalene derivative 1, functionalised with an azobenzene substituent, has been ... more The new tetrathiafulvalene derivative 1, functionalised with an azobenzene substituent, has been synthesised. Cyclic voltammetric and spectroelectrochemical studies in solution demonstrate the reversible formation of the radical cation of 1. UVVIS spectroscopy suggests that ...
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