Search results for "Spectrophotometry"

Fennel waste-based films suitable for protecting cultivations.

2007

Biodegradable, flexible, and moisture-resistant films were obtained by recycling fennel waste and adding to fennel homogenates the bean protein phaseolin that was modified or not modified by the enzyme transglutaminase. All films were analyzed for their morphology, mechanical properties, water vapor permeability, and susceptibility to biodegradation under soil-like conditions. Our experiments showed that transglutaminase treatment of the phaseolin-containing fennel waste homogenates allowed us to obtain films comparable in their mechanical properties and water vapor permeability to the commercial films Ecoflex and Mater-Bi. Furthermore, biodegradability tests demonstrated that the presence …

Equilibrium coverage fluctuations: a new approach to quantify reversible adsorption of proteins.

2005

Protein dynamics observed by tunable mid-IR quantum cascade lasers across the time range from 10 ns to 1 s

2017

We have developed a spectrometer based on tunable quantum cascade lasers (QCLs) for recording time-resolved absorption spectra of proteins in the mid-infrared range. We illustrate its performance by recording time-resolved difference spectra of bacteriorhodopsin in the carboxylic range (1800–1700 cm− 1) and on the CO rebinding reaction of myoglobin (1960–1840 cm− 1), at a spectral resolution of 1 cm− 1. The spectrometric setup covers the time range from 4 ns to nearly a second with a response time of 10–15 ns. Absorption changes as low as 1 × 10− 4 are detected in single-shot experiments at t > 1 μs, and of 5 × 10− 6 in kinetics obtained after averaging 100 shots. While previous time-res…

Ultrafast excitation dynamics of low energy pigments in reconstituted peripheral light-harvesting complexes of photosystem I

2000

AbstractUltrafast dynamics of a reconstituted Lhca4 subunit from the peripheral LHCI-730 antenna of photosystem I of higher plants were probed by femtosecond absorption spectroscopy at 77 K. Intramonomeric energy transfer from chlorophyll (Chl) b to Chl a and energy equilibration between Chl a molecules observed on the subpicosecond time scale are largely similar to subpicosecond energy equilibration processes within LHCII monomers. However, a 5 ps equilibration process in Lhca4 involves unique low energy Chls in LHCI absorbing at 705 nm. These pigments localize the excitation both in the Lhca4 subunit and in LHCI-730 heterodimers. An additional 30–50 ps equilibration process involving red …

Hydrothermal Synthesis of Ionic Liquid [Bmim]OH-Modified TiO2 Nanoparticles with Enhanced Photocatalytic Activity under Visible Light

2010

TiO(2) nanocomposites modified with the ionic liquid [Bmim]OH are synthesized by a hydrothermal procedure. X-ray diffraction, Zeta-potential measurement, TEM, thermogravimetric analysis, photoluminescence, UV/Vis, FTIR, and X-ray photoelectron spectroscopy are used to characterize the TiO(2) nanocomposites. The TiO(2) nanocomposites consist of pure anatase particles of about 10 nm. The modification of [Bmim]OH on the surface of the TiO(2) particles extends the TiO(2) absorption edge to the visible-light region. The electrochemical redox potentials indicated that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of [Bmim]OH match well with the valen…

High-Performance TiO2 Nanoparticle/DOPA-Polymer Composites

2014

Many natural materials are complex composites whose mechanical properties are often outstanding considering the weak constituents from which they are assembled. Nacre, made of inorganic (CaCO 3 ) and organic constituents, is a textbook example because of its strength and toughness, which are related to its hierarchical structure and its well-defi ned organic–inorganic interface. Emulating the construction principles of nacre using simple inorganic materials and polymers is essential for understanding how chemical composition and structure determine biomaterial functions. A hard multilayered nanocomposite is assembled based on alternating layers of TiO 2 nanoparticles and a 3-hydroxytyramine…

Oral intake of cadmium, cobalt, copper, iron, lead, nickel, manganese and zinc in the university student's diet.

1993

A duplicate diet meal study was carried out with a group of university students living in a hostel, in order to estimate the intake of Zn, Cd, Co, Cu, Fe, Mn, Ni and Pb. Zn, Cu, Fe, Mn and Ni were determined by flame atomic absorption spectrophotometry and Cd, Co and Pb by graphite furnace atomic absorption spectrophotometry after a nitric acid wet digestion procedure. The estimated intake values from the contents of breakfast, lunch, dinner and drinks were compared with the values of the Provisional Tolerable Daily Intake (PTDI) in the case of Cd and Pb, Recommended Dietary Allowances (RDA) of Co, Fe and Zn and Estimated Safe and Adequate Dietetic Daily Intake (ESADDI) of Cu and Mn. Neithe…

Purification and spectroscopic studies on catechol oxidases from Lycopus europaeus and Populus nigra: evidence for a dinuclear copper center of type …

1999

We purified two catechol oxidases from Lycopus europaeus and Populus nigra which only catalyze the oxidation of catechols to quinones without hydroxylating tyrosine. The molecular mass of the Lycopus enzyme was determined to 39,800 Da and the mass of the Populus enzyme was determined to 56,050 Da. Both catechol oxidases are inhibited by thiourea, N-phenylthiourea, dithiocarbamate, and cyanide, but show different pH behavior using catechol as substrate. Atomic absorption spectrosopic analysis found 1.5 copper atoms per protein molecule. Using EPR spectroscopy we determined 1.8 Cu per molecule catechol oxidase. Furthermore, EPR spectroscopy demonstrated that catechol oxidase is a copper enzym…

Spectrophotometric investigation of the binding of vitamin E to water-containing reversed micelles.

2002

The distribution constants of vitamin E partitioned between apolar organic phase and water-containing reversed micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT), didodecyldimethylammonium bromide (DDAB), soybean phosphatidylcholine (lecithin) and tetraethylene glycol monododecyl ether (C12E4) have been evaluated by a spectrophotometric method. The results suggest that in the presence of domains from apolar organic solvent to surfactant and to water, vitamin E is partitioned between the micellar palisade layer and the organic solvent and also that its binding strength to reversed micelles depends mainly by specific interactions between the head group of vitamin E and that of the sur…

Analytical methodologies for atomic spectrometric determination of metallic oxides in UV sunscreen creams.

2000

In this study, methodologies for determining titanium oxide, zinc oxide and iron oxide are proposed and assayed in commercial sunscreen products. The proposed methodology for TiO2, determination in sunscreens is based on a microwave-assisted treatment for digesting the organic components in a closed teflon reactor in presence of HNO3 and HCl. Titanium is determined by inductive coupled plasma emission spectrometry (ICP-AES). The proposed methodologies for measuring ZnO and Fe2O3 are based on a sample emulsification in water with a non ionic tensioactive and IBMK, followed by Zn and Fe determination by flame atomic absorption spectrometry (FAAS). The methodologies allow a precise and accurat…