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The two intertwined strands of DNA are held together through base pairing--the formation of hydrogen bonds between bases located opposite each other on the two strands. DNA replication and transcription involve the breaking and re-forming of these hydrogen bonds, but it is difficult to probe these processes directly. For example, conventional DNA(More)
Guanosine monophosphate (GMP) in aqueous solutions has been studied with femtosecond broad-band transient absorption spectroscopy and by quantum-mechanical calculations. The sample was excited at 267 or 287 nm and probed between 270 and 1000 nm with 100 fs resolution, for various pH values between 2 and 7. At pH 2, when the guanine ring is ground-state(More)
Gold nanoparticles were surface modified with an ionizable and pH-sensitive monolayer of thiobarbituric acid (TBA). By variation of the pH value of the solution, nanoparticle aggregates can be produced in a controlled way. The aggregates thus prepared were irradiated with an intense pulsed laser at 532 nm. The products in solution were examined by(More)
In this article we reinvestigate the bimodal fluorescence of cytochrome c (Cyt c) by using excitation-wavelength-dependent fluorescence spectroscopy. We show that its major contributions at pH 3-7 do not arise from tryptophan (Trp-59) fluorescence as hitherto assumed. Instead, different chromophores of Cyt c contribute at different pH values. At pH 3-7, the(More)
Photoreduction of cytochrome c (Cyt c) has been reinvestigated using femtosecond-to-nanosecond transient absorption and stationary spectroscopy. Femtosecond spectra of oxidized Cyt c, recorded in the probe range 270-1000 nm, demonstrate similar evolution upon 266 or 403 nm excitation: an ultrafast 0.3 ps internal conversion followed by a 4 ps vibrational(More)
The vibronic spectrum of the adenine-thymine (A-T) base pair was obtained by one-color resonant two-photon ionization (R2PI) spectroscopy in a free jet of thermally evaporated A and T under conditions favorable for formation of small clusters. The onset of the spectrum at 35,064 cm-1 exhibits a large red shift relative to the pi-pi* origin of 9H-adenine at(More)
To understand the intrinsic properties of peptides, which are determined by factors such as intramolecular hydrogen bonding, van der Waals bonding and electrostatic interactions, the conformational landscape of isolated protein building blocks in the gas phase was investigated. Here, we present IR-UV double-resonance spectra of jet-cooled, uncapped peptides(More)
We present resonant two-photon ionization (R2PI), IR-UV, and UV-UV double resonance spectra of jet-cooled 2-aminopurine (2AP) as well as Fourier transform infrared (FTIR) gas phase spectra. 2AP is a fluorescing isomer of the nucleobase adenine. The results show that there is only one tautomer of 2AP which absorbs in the wavelength range 32,300-34,500(More)
A micelle-based method to synthesize dispersed polyaniline (PANI)-Au composite particles by direct oxidation of aniline using AuCl4- as the oxidant is presented. The obtained composite particles have a core-shell structure, where Au nanoparticles of 20 nm mean diameter are encapsulated by PANI of well-defined tetrahedron shape with 150 nm average edge(More)