Johnny Hendriks

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Photoactive yellow protein (PYP) is a eubacterial photoreceptor and a structural prototype of the PAS domain superfamily of receptor and regulatory proteins. We investigate the activation mechanism of PYP using time-resolved Fourier transform infrared (FTIR) spectroscopy. Our data provide structural, kinetic, and energetic evidence that the putative(More)
The flavoprotein AppA from Rhodobacter sphaeroides contains an N-terminal, FAD-binding BLUF photoreceptor domain. Upon illumination, the AppA BLUF domain forms a signaling state that is characterized by red-shifted absorbance by 10 nm, a state known as AppA(RED). We have applied ultrafast spectroscopy on the photoaccumulated AppA(RED) state to investigate(More)
A dynamic mathematical model of Carbon-dioxide Accelerated Ammonia Release (CAAR) was developed based on the known knowledge of the chemistry of ammonia (NH3) in liquid solution, mass transfer inside liquid and across liquid-gaseous interface, and a new concept of CAAR. It calculated the NH3 concentration, release and emission at transient and steady state(More)
In this study we have investigated binding of the fluorescent hydrophobicity probe Nile Red to the photoactive yellow protein (PYP), to characterize the exposure and accessibility of hydrophobic surface upon formation of the signaling state of this photoreceptor protein. Binding of Nile Red, reflected by a large blue shift and increase in fluorescence(More)
Indoor air quality in animal buildings is very important to the health of agricultural workers and animals. Carbon dioxide (CO2) and ammonia (NH3) are two of the most important pollutants in pig houses. Four tests were conduced in a mechanically ventilated pig house to study release behaviors of CO2 and NH3 from liquid manure using impulse, pulse and step(More)
Light-dependent pH changes were measured in unbuffered solutions of wild type photoactive yellow protein (PYP) and its H108F and E46Q variants, using two independent techniques: transient absorption changes of added pH indicator dyes and direct readings with a combination pH electrode. Depending on the absolute pH of the sample, a reversible protonation as(More)
We have studied the kinetics of the blue light-induced branching reaction in the photocycle of photoactive yellow protein (PYP) from Ectothiorhodospira halophila, by nanosecond time-resolved UV/Vis spectroscopy. As compared to the parallel dark recovery reaction of the presumed blue-shifted signaling state pB, the light-induced branching reaction showed a(More)
Fourier transform infrared (FTIR) spectroscopy was applied to the blue-light photoreceptor photoactive yellow protein (PYP) to investigate water structural changes possibly involved in the photocycle of PYP. Photointermediates were stabilized at low temperature, and difference IR spectra were obtained between intermediate states and the original state of(More)
The Photoactive Yellow Protein (PYP) from Halorhodospira halophila (formerly Ectothiorhodospira halophila) is increasingly used as a model system. As such, a thorough understanding of the photocycle of PYP is essential. In this study we have combined information from pOH- (or pH-) dependence and (kinetic) deuterium isotope effects to elaborate on existing(More)
The redox-midpoint potential of the FAD chromophore in the BLUF domain of anti-transcriptional regulator AppA from Rhodobacter sphaeroides equals ∼-260mV relative to the calomel electrode. Altering the structure of its chromophore-binding pocket through site-directed mutagenesis brings this midpoint potential closer to that of free flavin in aqueous(More)