6302136
Ultrafast fluorescence resonance energy transfer in the micelle and the gel phase of a PEO-PPO-PEO triblock copolymer: excitation wavelength dependence.
Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to rhodamine 6G (R6G) is studied in the micelle and the gel phase of a triblock copolymer, (PEO)20-(PPO)70-(PEO)20 (Pluronic P123 (P123)) by picosecond and femtosecond emission spectroscopy. The time constants of FRET were obtained from the rise time of the acceptor (R6G) emission. In a P123 micelle, FRET occurs in multiple time scales: 2.5, 100, and 1700 ps. In the gel phase, three rise components are observed: 3, 150, and 2600 ps. According to a simple Förster model, the ultrafast (2.5 and 3 ps) components of FRET correspond to donor-acceptor distance RDA=13 +/- 2 A. The ultrafast FRET occurs between a donor and an acceptor residing at close contact at the corona (PEO) region of a P123 micelle. With increase in the excitation wavelength (lambdaex) from 375 to 435 nm, the relative contribution of the ultrafast component of FRET ( approximately 3 ps) increases from 13% to 100% in P123 micelle and from 1% to 100% in P123 gel. It is suggested that at lambdaex = 435 nm, mainly the highly polar peripheral region is probed where FRET is very fast due to close proximity of the donor and the acceptor. The 100 and 150 ps components correspond to RDA = 25 +/- 2 A and are ascribed to FRET from C480 deep inside the micelle to an acceptor (R6G) in the peripheral region. The very long component of FRET (1700 ps in micelle and 2600 ps component in gel) may arise from diffusion of the donor from outside the micelle to the interior followed by fast FRET.
20484682
Ultrafast proton transfer of pyranine in a supramolecular assembly: PEO-PPO-PEO triblock copolymer and CTAC.
Excited-state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) is studied in a polymer-surfactant aggregate using femtosecond emission spectroscopy. The polymer-surfactant aggregate is a supramolecular assembly consisting of a triblock copolymer (PEO)(20)-(PPO)(70)-(PEO)(20) (P123) and a cationic surfactant, cetyltrimethylammonium chloride (CTAC). ESPT of the protonated species (HA) in HPTS leads to the formation of A(-). The dynamics of ESPT may be followed from the decay of the HA emission (at approximately 440 nm) and rise of the A(-) emission (at approximately 550 nm). Both steady-state and time-resolved studies suggest that ESPT of HPTS in P123-CTAC aggregate is much slower than that in bulk water, in P123 micelle, or in CTAC micelle. The ratio of the steady-state emission intensities (HA/A(-)) in P123-CTAC aggregate is 2.2. This ratio is approximately 50, 12, and 2 times higher than that respectively in water, in P123 micelle, and in CTAC micelle. Retardation of ESPT causes an increase in the rise time of the A(-) emission of HPTS. In P123-CTAC aggregate, A(-) displays three rise times: 30, 250, and 2400 ps. These rise times are longer than those in CTAC micelle (23, 250, and 1800 ps), in bulk water (0.3, 3, and 90 ps), and in P123 micelle (15 and 750 ps). The rate constants for initial proton transfer, recombination, and dissociation of the ion pair are estimated using a simple kinetic scheme. The slow fluorescence anisotropy decay of HPTS in P123-CTAC aggregate is analyzed in terms of the wobbling-in-cone model.
40815524
Constrained photophysics of partially and fully encapsulated charge transfer probe (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester inside cyclodextrin nano-cavities: evidence of cyclodextrins cavity dependent complex stoichiometry.
The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the α- and β-CD show different stoichiometries as observed from the Benesi-Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous α- and β-CD solutions.
8239089
Remodeling of the antegonial angle region in the human mandible: a panoramic radiographic cross-sectional study.
OBJECTIVES
This study analyzed changes in the antegonial region in relation to age, gender, and dental status.


STUDY DESIGN
A total of one thousand patients (five hundred males and five hundred females), who were prescribed panoramic radiograph for various purposes were included in the study. The patients were categorized according to age, gender and dentition status. Panoramic radiographs were traced and antegonial angles and depths were measured.


RESULTS
A trend of decrease in the antegonial angle and increase in antegonial depth with age was observed in both males and females. Furthermore there were differences between right and left side antegonial angle and depth, with left side angle more than right and right side depth more than left. There was a significant decrease in the values of antegonial angle and significant increase in the values of antegonial depth as the dentition status changed from completely dentulous to partially dentulous and from partially dentulous to completely edentulous state.


CONCLUSIONS
The antegonial angle decreases with the advancing age and thereby increases the antegonial depth. Similar trends are seen when teeth are lost. Furthermore there is an inherent asymmetry in the antegonial region in right and left side.
207128360
Spectroscopic and electronic structure studies of phenolate Cu(II) complexes: phenolate ring orientation and activation related to cofactor biogenesis.
A combination of spectroscopies and DFT calculations have been used to define the electronic structures of two crystallographically defined Cu(II)-phenolate complexes. These complexes differ in the orientation of the phenolate ring which results in different bonding interactions of the phenolate donor orbitals with the Cu(II), which are reflected in the very different spectroscopic properties of the two complexes. These differences in electronic structures lead to significant differences in DFT calculated reactivities with oxygen. These calculations suggest that oxygen activation via a Cu(I) phenoxyl ligand-to-metal charge transfer complex is highly endergonic (>50 kcal/mol), hence an unlikely pathway. Rather, the two-electron oxidation of the phenolate forming a bridging Cu(II) peroxoquinone complex is more favorable (11.3 kcal/mol). The role of the oxidized metal in mediating this two-electron oxidation of the coordinated phenolate and its relevance to the biogenesis of the covalently bound topa quinone in amine oxidase are discussed.
13636170
Accuracy of Quadratic Versus Linear Interpolation in Noninvasive Electrocardiographic Imaging (ECGI)
Electrocardiographic Imaging (ECGI) is a cardiac functional imaging modality, noninvasively reconstructing epicardial potentials, electrograms and isochrones (activation maps) from multi-channel body surface potential recordings. The procedure involves solving Laplace’s equation in the source-free volume conductor between torso and epicardial surfaces, using Boundary Element Method (BEM). Previously, linear interpolation (LI) on three-noded triangular surface elements was used in the BEM formulation. Here, we use quadratic interpolation (QI) for potentials over six-noded linear triangles. The performance of LI and QI in ECGI is evaluated through direct comparison with measured data from an isolated canine heart suspended in a human-torso-shaped electrolyte tank. QI enhances the accuracy and resolution of ECGI reconstructions for two different inverse methods, Tikhonov regularization and Generalized Minimal Residual (GMRes) method, with the QI-GMRes combination providing the highest accuracy and resolution. QI reduces the average relative error (RE) between reconstructed and measured epicardial potentials by 25%. It preserves the amplitude (average RE reduced by 48%) and morphology of electrograms better (average correlation coefficient for QI ∼ 0.97, LI ∼ 0.92). We also applied QI to ECGI reconstructions in human subjects during cardiac pacing, where QI locates ventricular pacing sites with higher accuracy (≤ 10 mm) than LI (≤ 18 mm).
24052464
Chemically induced unfolding of bovine serum albumin by urea and sodium dodecyl sulfate: a spectral study with the polarity-sensitive charge-transfer fluorescent probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester.
Sensitivity of the charge-transfer (CT) band of the fluorescence probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester (MAPAME) towards the polarity of its immediate environment is employed to investigate the binding interaction of the probe with bovine serum albumin (BSA) and uncoiling of BSA by the denaturants urea and sodium dodecyl sulfate micelles. Binding of the probe with BSA produces a blue shift and enhanced intensity of the CT emission band which clearly point toward a decrease in polarity of the immediate environment of MAPAME. This is expected, since binding with BSA moves the probe from a polar water environment to a much less polar, hydrophobic protein interior, where the CT band is expected to be blue-shifted. Higher intensity arises due to fewer non-radiative decay paths available to the probe in the hydrophobic protein environment. Chemically induced unfolding of BSA by urea and sodium dodecyl sulfate is tracked by monitoring the induced spectral changes of the protein-bound probe MAPAME. Red-edge excitation shift or REES, fluorescence resonance energy transfer (FRET) and anisotropy measurements are used to investigate and monitor these binding and unfolding processes.