Fluorescence and phosphorescence of tryptophan in peptides of different length and sequence.

To interpret accurately protein fluorescence and phosphorescence, it is essential to achieve a better understanding of the luminescence properties of tryptophan (Trp, or W) in peptides. In published literature data on luminescence of peptides of varied length are scarce. This article describes studies of fluorescence and phosphorescence properties of the eight Trp-containing synthetic peptides: WAK, AWK, SWA, KYLWE, AVSWK, WVSWAK, WAKLAWE, and AVSWAKLARE.

Excited state structural changes of 10-cyano-9-tert-butyl-anthracene (CTBA) in polymer matrices.

Two main deactivation processes are suggested to be present in the electronic excited state of 10-cayano-9-tert-butyl-anthracene (CTBA): one leading to the Dewar strucure resulted from photochemical effect, similar to the case of 9-tert-butyl-anthracene (TBA), which is enhanced in solution, and another leads to a more planar structure leading to a Charge Transfer (CT) state and is enhanced in polymers. The presence of donor (tert-butyl group) and an acceptor (cyano group) along the line of 9,10 positions in CTBA confirm our hypothesis of CT state. Our suggestions were supported by steady state and time resolved fluorescence spectra results.

Single shot laser flash photolysis with a fibre-coupled reference beam monitor.

In the standard nanosecond laser photolysis method for kinetic studies, a Q-switched laser generates transient species, and absorption spectrophotometry provides a measure of their concentrations. The sample is placed between the monitoring source (a pulsed xenon arc or a flash lamp) and a monochromator, and a photomultiplier tube (PMT) is used for measuring the intensity of the light leaving the exit slit of the monochromator. With this (single-beam) arrangement, the laser-induced change in the absorbance of the sample, ΔA, can be calculated only if the intensity of the monitoring beam remains constant during the time interval of interest.

Formation and geminate quenching of singlet oxygen in purple bacterial reaction center.

The phosphorescence of singlet oxygen ((1)X( *)) photosensitized by the carotenoidless reaction center (RC) of Rhodobacter sphaeroides R26.1 has been investigated, using H(2)O and D(2)O as the suspending media. To enhance (under neutral conditions) the triplet quantum yield of the special pair P(870) (P) by the radical pair mechanism, the quinone acceptor Q(A) was removed by means of a chemical treatment.

Structural characterization of new Cd(2+) fluorescent sensor based on lumazine ligand: AM1 and ab initio studies.

6-Thienyllumazine (TLM) is synthesized as a new fluorescent sensor that is capable of indicating selectively the presence of Cd(2+) ion via a fluorescence signal. Experiment has been performed in the presence of Ni(2+), Co(2+), Cu(2+), Ag(+), Mn(2+), Hg(2+), Zn(2+), Pb(2+), and Mg(2+) metal ions in aqueous solutions. The product was characterized by elemental analysis, mass, and NMR spectra.

Atmospheric deposition of major and trace elements in Amman, Jordan.

Wet and dry deposition samples were collected in the capital of Jordan, Amman. Concentrations of Al, Ba, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V, Zn, Fe, Sr, Mg2+, Ca2+, Na+, K+, Cl-, NO3- and SO(4)(2-), along with pH were determined in collected samples. Mean trace metal concentrations were similar or less than those reported for other urban regions worldwide, while concentrations of Ca2+ and SO(4)(2-) were among the highest.

Singlet oxygen quenching by thione analogues of canthaxanthin, echinenone and rhodoxanthin.

Thione analogues of three naturally occurring carotenones (canthaxanthin, echinenone, and rhodoxanthin) were synthesized just over ten years ago, and it was reported that substitution of the oxygen atom by sulphur brings about a large red shift and some broadening in the optical absorption spectrum of the compound. Since the three carotenothiones are scarce, determination of their molar absorption coefficients presents a challenge. A method for relating the molar absorption coefficient of a carotenothione (Car-S) to that of its ketone analogue (Car-O) has been developed, which has revealed that the peak molar absorption coefficient of a Car-S is only about 60% of the corresponding value for Car-O.

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C(3)H(7)X where X = F, Cl, and Br.

HF, MP2, and B3LYP calculations with different basis sets have been used in the computation of the stabilization energies of C(3)H(7)X isomers, where X is F, Cl, and Br. The experimental stabilization energies of the structural isomers of C(3)H(7)Cl and C(3)H(7)Br have been reproduced via B3LYP calculations. However, the calculated stabilization energies of fluoropropane isomers from their reported enthalpies of formation have been reproduced in all methods of calculations in present work.