Search results for "bleaching"
showing 10 items of 107 documents
Dominance of Chain Entanglement over Transient Sticking on Chain Dynamics in Hydrogen-Bonded Supramolecular Polymer Networks in the Melt
2018
The chain dynamics in supramolecular polymer networks is determined by the interplay of the kinetics of transient interchain association and relaxation of the network chains themselves. This interplay can be addressed by studying model supramolecular polymer networks in which the number of associative side groups and the molar mass of the covalently jointed backbone polymers are both varied systematically. To realize this idea, we use precursor chains with three different molar masses, which comes along with different extents of entanglement in the melt state. For each molar mass, the precursor polymers are functionalized with three different relative contents of associative side groups, gi…
Imaging of Keratin Dynamics during the Cell Cycle and in Response to Phosphatase Inhibition
2004
Publisher Summary The characterization and development of autofluorescent proteins, most prominently of the green florescent protein, have provided tools to label cellular structures such that they can be examined in living cells. This chapter highlights the potential of live cell imaging in providing novel and unprecedented insights into the dynamic organization of the keratin cytoskeleton and outlines the important aspects of this method. The live cell imaging experiments suggest that the driving force behind the vectorial and dynamic keratin distribution patterns relies both on microtubules and microfilaments and their associated factors. The studies on the dynamics of the keratin cytosk…
Titanium dioxide in dental enamel as a trace element and its variation with bleaching
2017
Background Titanium is a less studied trace element in dental enamel. Literature relates an increased Titanium concentration with a decreased enamel crystal domain size, which in turn is related to a higher color value. The aim of our study was to analyze the effect of tooth bleaching agents on its concentration in dental enamel by means of confocal Raman spectroscopy. Material and methods Human teeth were randomly distributed in six experimental groups (n=10) and submitted to different bleaching protocols according to the manufacturer´s instructions. Confocal Raman spectroscopy was carried out in order to identify and quantify the presence of titanium dioxide molecules in enamel prior to a…
Removal of Chromophore-proximal Polar Atoms Decreases Water Content and Increases Fluorescence in a Near Infrared Phytofluor
2015
Genetically encoded fluorescent markers have revolutionized cell and molecular biology due to their biological compatibility, controllable spatiotemporal expression, and photostability. To achieve in vivo imaging in whole animals, longer excitation wavelength probes are needed due to the superior ability of near infrared light to penetrate tissues unimpeded by absorbance from biomolecules or autofluorescence of water. Derived from near infrared-absorbing bacteriophytochromes, phytofluors are engineered to fluoresce in this region of the electromagnetic spectrum, although high quantum yield remains an elusive goal. An invariant aspartate residue is of utmost importance for photoconversion in…
meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species
2015
Susceptibility to interact with trifluoroacetic acid (TFA) of selected free-base porphyrins, including a novel lipophilic 3-n-pentadecyl(phenoxy)-ethoxy-phenyl-substituted porphyrin, and photostability of their diprotonated compounds was explored in benzene and N,N-dimethylformamide (DMF). Results have been discussed in terms of the commonly applied pK a -based procedure and confronted with a simple approach derived from experimentally-determined correlations reflecting the porphyrins affinity for TFA. Density functional theory (DFT) has proved the porphyrin moiety creates stable diprotonated species involving two TFA molecules, in which the fluorine atoms effectively contribute to the over…
Two-photon excitation microscopy of tryptophan-containing proteins.
2002
We have examined the feasibility of observing single protein molecules by means of their intrinsic tryptophan emission after two-photon excitation. A respiratory protein from spiders, the 24-meric hemocyanin, containing 148 tryptophans, was studied in its native state under almost in vivo conditions. In this specific case, the intensity of the tryptophan emission signals the oxygen load, allowing one to investigate molecular cooperativity. As a system with even higher tryptophan content, we also investigated latex spheres covered with the protein avidin, resulting in 340 tryptophans per sphere. The ratio of the fluorescence quantum efficiency to the bleaching efficiency was found to vary b…
Photoblinking and photobleaching of rylene diimide dyes.
2010
We investigate photoblinking and photobleaching of perylene diimide (PDI) and its higher homologue terrylene diimide (TDI). Single molecule fluorescence trajectories of the dye molecules embedded in PMMA under ambient conditions exhibit "on"-"off" blinking in the time range from ms to s. Due to the limited statistics of individual trajectories we construct ensemble distributions of "on" and "off" times which follow power laws with similar power law coefficients (m(on) ≈ 1.18, m(off) ≈ 1.31). The blinking is attributed to reversible formation of radical cations which are presumably created by electron transfer from higher excited triplet states T(n) of the molecules to acceptor levels in the…
Knowledge and decisions in environmental contexts : a case study of the pulp and paper industry
2003
In vivo evaluation of the effects of 10% carbamide peroxide and 3.5% hydrogen peroxide on the enamel surface
2007
Objectives: Bleaching of vital teeth performed at home by the patient under the dentist’s supervision, using low-concentration peroxides and custom-fitted trays specifically designed for this purpose, is one of several options for this type of dental treatment, whether alone or in combination with another in-office bleaching technique. The objective of this study is to analyse the effect on the enamel surface of two bleaching products recommended for this technique. Materials & methods: Two bleaching products were used: VivaStyle (Vivadent), a 10% carbamide peroxide, and FKD (Kin), a 3.5% hydrogen peroxide. They were applied in trays to the anterior teeth of 20 patients (10 in each group). …