Gas-phase photochemistry of the photoactive yellow protein chromophore trans-p-coumaric acid.

The photoisomerization of trans-p-coumaric acid (trans-CA) triggers a photocycle in photoactive yellow protein that ultimately mediates a phototactic response to blue light in certain purple bacteria. We have used fluorescence excitation and dispersed emission methods in a supersonic jet to investigate the nature of the electronic excited states involved in the initial photoexcitation and subsequent photoisomerization of trans-CA. We observed three distinct regions in the fluorescence excitation spectrum of trans-CA.

Gas Supersaturation Thresholds for Bubble Formation in and Damage to Sea Urchin Embryos.

Eggs and early embryonic stages of the sea urchin Lytechinus pictus were subjected to hyperbaric gas pressures and rapid decompression. All stages showed a remarkable tolerance to gas supersaturations. No damage or internal bubbles were apparent in the eggs after decompression from less than 240 atm nitrogen or 209 atm argon.