2,395 research outputs found
BILIPROTEINS FROM THE BUTTERFLY Pieris brassicae STUDIED BY TIME-RESOLVED FLUORESCENCE AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY
The fluorescence decay time of the biliverdin IX7 chromophore present in biliproteins isolated from Pieris brassicae is determined to be 44 ± 3 ps. This value suggests a cyclic helical chromophore structure. The vibrational frequencies determined by CARS-spectroscopy are compared with those of model compounds. The data confirm that the chromophore in the protein-bound state adopts a cyclic-helical, flexible conformation
Direct mail selection by joint modeling of the probability and quantity of response
Operations such as integration or modularization of databases can be considered as operations on database universes. This paper describes some operations on database universes. Formally, a database universe is a special kind of table. It turns out that various operations on tables constitute interesting operations on database universes as well.
Status of advanced propulsion for space based orbital transfer vehicle
A new Orbital Transfer Vehicle (OTV) propulsion system will be required to meet the needs of space missions beyond the mid-1990's. As envisioned, the advanced OTV will be used in conjunction with Earth-to-orbit vehicles, Space Station, and Orbit Maneuvering Vehicle. The OTV will transfer men, large space structures, and conventional payloads between low Earth and higher energy orbits. Space probes carried by the OTV will continue the exploration of the solar system. When lunar bases are established, the OTV will be their transportation link to Earth. NASA is currently funding the development of technology for advanced propulsion concepts for future Orbital Transfer Vehicles. Progress in key areas during 1986 is presented
Picosecond time-resolved fluorescence of phycobiliproteins
The α- and ÎČ-subunits of C-phycocyanin from Mastigocladus laminosus were prepared according to revised procedures. Both subunits are isolated as dimers, which can be dissociated into monomers with detergent mixtures. The fluorescence decay kinetics are similar for the respective monomers and dimers. In no case could they be fitted by only one (α-subunit) or two exponentials (ÎČ-subunit) which are predicted by theory for samples with a unique chromophoreâprotein arrangement containing one and two chromophores, respectively. It is suggested that there exists a heterogeneity among the chromophores of the subunits, which may persist in the highly aggregated complexes present in cyanobacterial antennas
Energy transfer within phycocyanin trimers of Mastigocladus laminosus studied by picosecond time-resolved transient absorption spectroscopy
The transient absorption recovery induced in phycocyanin trimers by picosecond pulses of
variable wavelength (570 â 620 nm) has been recorded and analyzed by applying a least-squares
multi-exponential fit procedure.
The results suggest that in native PC trimers the chromophores exhibit a microheterogeneity
with the effect that the derived apparent lifetimes are functions of excitation and probing wavelength.
It is suggested that, due to strong excitonic coupling between a-84 and Ă-84
chromophores, the lifetime of the terminal acceptor state is reduced to about 900 ps; the apparent
energy transfer time from chromophore ÎČ-155 to a-84 and Ă-84 chromophores varies between
20â50 ps depending on the actual chromophore-protein arrangement (microheterogeneity)
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