Spectrophotometry Research Papers - Academia.edu (original) (raw)

The aim of this study was to evaluate, in vitro, the effect of iron on the dissolution of bovine enamel powder, when added to two carbonated beverages.Powdered enamel was produced by griding enamel fragments of bovine incisor in a steel... more

The aim of this study was to evaluate, in vitro, the effect of iron on the dissolution of bovine enamel powder, when added to two carbonated beverages.Powdered enamel was produced by griding enamel fragments of bovine incisor in a steel pestle and mortar. Particles between 75 and 106 μm were selected using appropriated meshes. At time zero, the carbonated beverage (Coke® or Sprite Zero®) was added to powdered enamel (1 mg enamel powder/10 μL of beverage) and vortexed for 30 s. The sample was immediately centrifuged (11,000 rpm) for 30 s and the supernatant was removed at 1 min 40 s. This procedure was repeated five times with the beverage containing increasing ferrous sulphate concentrations (1.25, 2.5, 5, 10, 15, 30 and 60 mmol/L). The phosphate released in the medium was analysed spectrophotometrically. Data were analysed using ANOVA and Tukey's test (p < 0.05).When iron at 30 and 60 mmol/L was added to Coke®, a significant reduction in the dissolution of powdered enamel was observed when compared to control (11 and 17%, respectively), while lower iron concentrations did not have any effect on enamel powder dissolution. Regarding Sprite Zero®, iron concentrations up to 10 mmol/L had no significant effect, while higher concentrations significantly increased enamel powder dissolution.The results suggest that iron can interfere with the dissolution of dental enamel powder in the presence of acidic beverages and the type of acid in these beverages seems to modulate this effect.

This study aims to determine whether or not cyanide content in various species of yams in the District of Tempel, Sleman, Yogyakarta. The samples were cassava (Manihot esculenta Crantz), water yam (Discorea Alata), intoxicating yam... more

This study aims to determine whether or not cyanide content in various species of yams in the District of Tempel, Sleman, Yogyakarta. The samples were cassava (Manihot esculenta Crantz), water yam (Discorea Alata), intoxicating yam (Dioscorea hispida Dennst), canna lilly (Canna discolor L), and taro (Colocasia esculenta). The qualitative test was performed by cementing the sample with aquadest and 10% tartrate acid and then covering the erlenmeyer that containing the sample with dry filter paper immersed in saturated picric acid and dampened with 8% sodium carbonate and then heating it. Quantitative tests were performed using a spectrum 20 with a wavelength of 590 nm. This quantitative test is based on forming a blue hydrindantin complex at pH 12 when cyanide is reacted with a ninhydrin complex. The results showed that in qualitative test, sample containing cyanide was indicated by the change of color of filter paper from yellow to brownish red. Quantitative results show that cyanid...

Citric acid (CIT, 0.3%) was assessed for its ability to reduce the pink color defect in ground, cooked (80C) turkey breast associated with nicotinamide hemochrome (NICHEME) and nitrosyl hemochrome (NITHEME). CIT incorporation in... more

Citric acid (CIT, 0.3%) was assessed for its ability to reduce the pink color defect in ground, cooked (80C) turkey breast associated with nicotinamide hemochrome (NICHEME) and nitrosyl hemochrome (NITHEME). CIT incorporation in nicotinamide-treated (NIC, 1.0%) samples (CIT plus NIC) reduced (P<0.05) redness by 51% compared to the control and 63% compared to the NIC-only treatment. CIT addition in sodium nitrite-treated (NIT, 10 ppm) samples (CIT plus NIT) was similar (P>0.05) in redness to the control and reduced (P<0.05) the redness by 43% compared to the NIT- only treatment. All treatments containing citric acid lowered the pH and increased (P<0.05) cooking loss compared to samples without citric acid. At the level tested, addition of citric acid would provide poultry processors a means to eliminate or significantly reduce the pink defect. However, the use of citric acid may require the addition of nonacid

Two-photon photoluminescence (TPPL) emission spectra of DNA-gold nanoparticle (AuNP) monoconjugates and the corresponding DNA-linked AuNP dimers are obtained by photon time-of-flight spectroscopy. This technique is combined with... more

Two-photon photoluminescence (TPPL) emission spectra of DNA-gold nanoparticle (AuNP) monoconjugates and the corresponding DNA-linked AuNP dimers are obtained by photon time-of-flight spectroscopy. This technique is combined with two-photon photoluminescence fluctuation correlation spectroscopy (TPPL-FCS) to simultaneously monitor the optical and hydrodynamic behaviour of these nano-assemblies in solution, with single-particle sensitivity and microsecond temporal resolution. In this study, the AuNPs have an average core diameter of 12 nm, which renders their dark-field plasmonic light scattering too weak for single-particle imaging. Moreover, as a result of the lack of plasmonic coupling in the dimers, the optical extinction, scattering and photoluminescence spectra of the DNA-AuNP complexes are not sufficiently different to distinguish between monomers and dimers. The use of TPPL-FCS successfully addresses these bottlenecks and enables the distinction between AuNP monomers and AuNP ...

By using a real-time assay that allows measurement of the phototactic orientation of the unicellular alga Chlamydomonas with millisecond time resolution, it can be shown that single photons not only induce transient direction changes but... more

By using a real-time assay that allows measurement of the phototactic orientation of the unicellular alga Chlamydomonas with millisecond time resolution, it can be shown that single photons not only induce transient direction changes but that fluence rates as low as 1 photon cell(-1) ...

The spectroscopic characteristics of the solid charge-transfer molecular complexes (CT) formed in the reaction of the electron donor 4-(aminomethyl) piperidine (4AMP) with the σ-acceptor iodine and the π-acceptors... more

The spectroscopic characteristics of the solid charge-transfer molecular complexes (CT) formed in the reaction of the electron donor 4-(aminomethyl) piperidine (4AMP) with the σ-acceptor iodine and the π-acceptors 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) have been studied in chloroform at 25°C. These were investigated through electronic, infrared spectra and thermal analysis as well as elemental analysis. The results show that the formed solid CT-complexes have the formulas [(4AMP)I](+)I3(-), [(4AMP)(DDQ)2] and [(4AMP)(TBCHD)] while in the case of 4AMP-TCNQ reaction, a short-lived CT complex is formed followed by rapid N-substitution by TCNQ forming the final reaction product 7,7,8-tricyano-8-aminomethylpiperidinylquinodimethane [TCAMPQDM] in full agreement with the known reaction stoichiometries in solution as well as the elemental measurements and the thermal analysis confirmed the structure of the obtained compounds. The formation constant kCT, molar extinction coefficient εCT, free energy change ΔG(0) and CT energy ECT have been calculated for the CT-complexes [(4AMP)I](+)I3(-), [(4AMP)(DDQ)2] and [(4AMP)(TBCHD)].

Hydrochlorous acid bleaches c-phycocyanin visible absorbance with a second-order rate constant (pH 7.4) of 1.3x10(3) M(-1) s(-1). In excess of protein, ca. 0.16 bilin moieties are disrupted by each reacted HOCl molecule. This indicates... more

Hydrochlorous acid bleaches c-phycocyanin visible absorbance with a second-order rate constant (pH 7.4) of 1.3x10(3) M(-1) s(-1). In excess of protein, ca. 0.16 bilin moieties are disrupted by each reacted HOCl molecule. This indicates that the main reaction takes place at the apoprotein level, with a total rate constant (in monomeric units concentration) of 2.5x10(4) M(-1) s(-1). This rate constant is too low to provide protection to other biomolecules under physiological conditions. The reported antiinflammatory properties of phycocyanin are not then related to the removal of HOCl. On the other hand, the rather slow reaction rate with HOCI could be beneficial to its role as antiinflammatory agent since it will allow the protein to maintain its integrity at the inflammation locus.

Stable radical 1, 1-dipheny-2-picrylhydrazyl (DPPH) is widely used at in vitro models to investigate antioxidant and radical scavenging abilities of natural extracts. This work presents comparative study on DPPH radical scavenging... more

Stable radical 1, 1-dipheny-2-picrylhydrazyl (DPPH) is widely used at in vitro models to investigate antioxidant and radical scavenging abilities of natural extracts. This work presents comparative study on DPPH radical scavenging capacity before and after UV irradiation of aqueous extract of Glycyrrhiza Glabra, a plant species belonging to the Indian flora. DPPH scavenging activities of different extract concentrations (at different incubation time intervals) were analyzed and compared by in vitro spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy. 9.93% and 16.79%, DPPH scavenging activities before and after UV irradiation respectively were found by spectrophotometry. By the EPR spectroscopy study statistical significant increase in DPPH radical scavenging for the Glycyrrhiza Glabra extracts was established after UV irradiation (78.39± 0.001%) comparing to the non irradiated samples (14.02± 0.02).

A continuous spectrophotometric assay has been developed for detecting beta-glucuronidase activity. In the assay, Para-nitrophenyl beta-D-glucuronide is cleaved to yield a chromophoric product. With the commercial E. coli enzyme, it is... more

A continuous spectrophotometric assay has been developed for detecting beta-glucuronidase activity. In the assay, Para-nitrophenyl beta-D-glucuronide is cleaved to yield a chromophoric product. With the commercial E. coli enzyme, it is demonstrated that the reactions can be continuously monitored by the increase of absorbance at 405 nm. The method is highly sensitive and able to detect less than 1.4 x 10(-4) U/mL of the enzyme activity in solution. Such a new assay offers significant advantages over the existing discontinuous methods and should be useful for both routine enzyme assay and accurate kinetic studies.