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Biophysical Journal 61: 1529-1539 (1992)
© 1992 the Biophysical Society

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Photobehavior of Halobacterium halobium

sinusoidal stimulation and a suppression effect of responses to flashes

Sabina Lucia, Cesare Ascoli and Donatella Petracchi

Istituto di Biofisica, Via S. Lorenzo 26, 56127 Pisa, Italy

ABSTRACT

Sequences of reversals recorded by single-cell observation of Halobacterium halobium are analyzed. Autocorrelation functions of spontaneous and stimulated reversals are computed; the results show that the only periodicity present in our data is that of the stimulus. Several different patterns of light stimuli were used. Responses to repetitive linear ramps of different slopes and to sinusoidal lights with different mean values and/or modulation depths are reported, showing that the modulation depth is the stimulus parameter most effective in eliciting photoresponses. Responses to more complex stimuli obtained by superimposing flashes to sinusoidal stimuli are also reported; a suppression effect depending on the phase of the sinusoidal stimulation is shown in responses to complex stimuli. A model which accounts for this effect is proposed.






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Copyright © 1992 by the Biophysical Society.