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Linear dichroism and orientation of the phycomyces photopigment: I. Response and absorption studies. II. Fluorescence studies


Jesaitis, Algirdas J. (1973) Linear dichroism and orientation of the phycomyces photopigment: I. Response and absorption studies. II. Fluorescence studies. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/C2AX-J941.


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The response of five strains of the fungus Phycomyces to linearly polarized light was studied. The sporangiophores of the strains, C2, C5, C9, C158, and NRRL 1555 (wildtype) differed primarily in optical attenuation. Their abilities to distinguish between longitudinally and transversely polarized blue light were found to be approximately the same.

The angle (with respect to the transverse axis) at which the [...] vector of the polarized light must be oriented to give a maximum response during perpendicular incidence into the cell was measured. It was found to be 42° ± 3° for 280 nm light in the wild type strain. In the C158 strain this angle was 7° ± 3° at 456 nm and 7 ± 8° at 486 nm.

The in vivo attenuation of polarized light as a function of the angle between the [...] vector and the cell axis was measured. The maximum transmission differences resulting from anisotropic attenuation were 4 ± 2% at 320 nm, 3 ± 2% at 456 nm, and 2 ± 1% at 486 nm.

These results indicate that the polarized light effect in Phycomyces cannot arise from reflections at the cell surface, nor from attenuations due to internal screening or scattering and, therefore, must be due to the dichroism and orientation of the visual pigment.

An attempt was made to detect the presence of the photopigment in cell wall and plasmalemma fractions using fluorescence kinetics and polarization. Excitation of these preparations with high intensity 488 nm laser light and monitoring fluorescence intensity with a microphotometer, a fluorescence decay and a periodic dependence of fluorescence intensity on the [...] vector angle of exciting light was found. The relevance of this fluorescence to the in vivo photosystem is questionable because of the high excitation intensity necessary to produce any detectable fluorescence.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Delbruck, Max
Thesis Committee:
  • Unknown, Unknown
Defense Date:18 April 1973
Record Number:CaltechETD:etd-08092006-084855
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3066
Deposited By: Imported from ETD-db
Deposited On:09 Aug 2006
Last Modified:21 Dec 2019 04:06

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