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751.
C A Ghiron R Santus M Bazin J Butler E J Land A J Swallow 《Biochimica et biophysica acta》1986,869(3):363-366
Charge transfer has been observed between oxidised tryptophan-26 units and the tyrosine-21 or -24 of the coat protein of fd phage. The transfer is likely to be intramolecular. The rates suggest that the aromatic units are in a rigid region and that they may have at least two different environments. No apparent interaction occurs with the DNA, consistent with tryptophan and tyrosine units not being in contact with the bases. 相似文献
752.
Motion and vision: why animals move their eyes 总被引:5,自引:0,他引:5
M. F. Land 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(4):341-352
Nearly all animals with good vision have a repertoire of eye movements. The majority show a pattern of stable fixations with
fast saccades that shift the direction of gaze. These movements may be made by the eyes themselves, or the head, or in some
insects the whole body. The main reason for keeping gaze still during fixations is the need to avoid the blur that results
from the long response time of the photoreceptors. Blur begins to degrade the image at a retinal velocity of about 1 receptor
acceptance angle per response time. Some insects (e.g. hoverflies) stabilise their gaze much more rigidly than this rule implies,
and it is suggested that the need to see the motion of small objects against a background imposes even more stringent conditions
on image motion. A third reason for preventing rotational image motion is to prevent contamination of the translational flow-field,
by which a moving animal can judge its heading and the distances of objects. Some animals do let their eyes rotate smoothly,
and these include some heteropod molluscs, mantis shrimps and jumping spiders, all of which have narrow linear retinae which
scan across the surroundings. Hymenopteran insects also rotate during orientation flights at speeds of 100–200° s−1. This is just consistent with a blur-free image, as are the scanning speeds of the animals with linear retinae.
Accepted: 29 April 1999 相似文献
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754.