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The self-complementary DNA decamer duplex d(CTGAATTCAG)2 and its modified counterpart d(CTGA[2AP]TTCAG)2, where the innermost adenine (6-aminopurine) has been replaced with the fluorescent analogue 2-aminopurine (2AP), have been studied by fluorescence and NMR spectroscopy and simulated by molecular dynamics. Both decamers are recognized and cleaved by the(More)
The fluorescence from a purified, aggregate form of the light-harvesting chlorophyll a/b protein has a lifetime of 1.2 +/- 0.5 ns at low excitation intensity, but the lifetime decreases significantly when the intensity of the 20-ps, 530-nm excitation pulse is increased above about 10(16) photons/cm2. A solubilized, monomeric form of the protein, on the(More)
2-Aminopurine (2AP) absorption and fluorescence excitation and emission spectra in a series of solvents have been measured to assess effects of solvent polarity. Emission spectra of the free base shift to the red in solvents of a higher dielectric constant, including water but excepting dioxane. Excitation spectra also red-shift, except in water. A change(More)
The sequence, temperature, concentration, and solvent dependence of singlet energy transfer from normal DNA bases to the 2-aminopurine base in synthesized DNA oligomers were investigated by optical spectroscopy. Transfer was shown directly by a variable fluorescence excitation band at 260-280 nm. Adenine (A) is the most efficient energy donor by an order of(More)
Absorption and fluorescence excitation and emission spectra of the B DNA duplex decamer d[CTGA(2AP)TTCAG]2, where emission from the 2AP (2-aminopurine) base dominates, have been measured as a function of temperature. A low-temperature excitation band in the 260-270-nm region disappears near the duplex melting temperature, Tm = 27 degrees C, but then(More)
Incorporation of 2-aminopurine (2AP) in place of adenine gives an optical probe of local and global DNA conformation. The temperature dependence of the absorption of the duplex d[CTGA(2AP)-TTCAG]2 DNA decamer shows that the helix has approximately an all-or-none melting transition. Absorbance at wavelengths of 260 and 330 nm monitors the average normal base(More)
Rebinding of carbon monoxide to the beta chain of hemoglobin after photodissociation by a laser flash is intramolecular below about 200 K. Above 25 K, rebinding occurs via classical over-the-barrier motion; below, quantum-mechanical tunneling dominates. Both are described by an energy spectrum peaked at Epeak=4.0 kilojoules per mole. The barrier width d(E),(More)
Binding of carbon monoxide to the separated alpha and beta chains of hemoglobin, with and without bound p-mercuribenzoate, has been measured at temperatures from 5 to 340 K for times 2 mus to 1 ks using flash photolysis. All four proteins exhibit three different rebinding processes. The data are interpreted by a model in which the carbon monoxide, moving(More)
Time-resolved fluorescence decay of a single-stranded DNA decamer d(CTGAAT5CAG), where d5 is the fluorescent base 1-(beta-D-2'-deoxyribosyl)-5-methyl-2-pyrimidinone, was measured and analyzed at several temperatures. The d5 base in the decamer is resolved into three states according to their fluorescence decay lifetime characteristics and temperature(More)
Polarity of the surrounding medium affects the excited states of UV-B sunscreens. Therefore understanding excited state processes in a mixed polarity model system similar to skin is essential. We report the excited state lifetimes, quantum yields, radiative and non-radiative rates of three sunscreens. Among the three UV-B sunscreens studied, octyl(More)