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Professor,
Dept. Biology.
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Left:
A photoreceptor cell from the ventral eye of the horseshoe crab, Limulus
polyphemus. Right: This is a movie of a Limulus ventral
photoreceptor releasing calcium during a flash of light. A red color means
a high calcium ion concentration, blue means less. On the left is an image
of the cell and on the right is a profile of calcium dye fluorescence along
the length of the cell. The light flash begins at the time of the first
frame, when the cell's image first appears. |
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Dr.
Payne investigates mechanisms of visual excitation in photoreceptors. The
research concentrates on messenger molecules released by light inside photoreceptor
cells. These messengers mediate and modulate the electrical response of
the photoreceptor to light. One messenger under investigation is inositol
trisphosphate, which releases calcium from internal stores within a wide
range of animal and plant cells. When injected into the giant photoreceptors
of the horseshoe crab, inositol trisphosphate mimics excitation of the
cell by light. Biochemical studies have shown that light releases inositol
trisphosphate from the photoreceptor's membrane into the cell interior.
These giant photoreceptors are one of the few living cells in which the
actions of this important messenger can be easily studied. |
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