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Structural studies of bacteriophage T7 and T7 capsids


Ruark, John Edward (1978) Structural studies of bacteriophage T7 and T7 capsids. Master's thesis, California Institute of Technology.


The structures of bacteriophage T7 and T7 capsids have been investigated by small-angle X-ray scattering. Phage T7 has a radius of 301 ± 2 Å (excluding the phage tail), and a calculated volume of 1.14 ±.05 x 10^(-16) ml. The radius determined for. T7 phage in solution is about 30% greater than the radius measured from electron micrographs, indicating that considerable shrinkage and distortion occurs during sample preparation for electron microscopy. Thus the volume calculated from X-ray scattering in solution is almost twice that estimated from electron microscope measurements. Capsids that have a phage-like envelope and do not contain DNA were obtained from lysates of T7-infected E. coli (capsid II) and by separating the capsid component of T7 phage from the phage DNA using temperature shock (capsid IV). These capsids have outer radii of 2[8?]3-289 ± 2 Å and are thus significantly smaller than the envelope of T7 phage. The thickness of the envelopes of two forms of capsid II are 20 and 23 ± 2 Å. The volume in T7 phage available to package DNA is estimated to be 9.2 ± .4 x 10^(-17) ml or 2.1 times the volume of the B form of T7 DNA. A T7 precursor capsid (capsid I), believed to be capable of pulling in DNA, has a smaller outer diameter (261 ± 2 Å) and a thicker envelope (52 ± 4 Å) than capsids II and IV. Capsid I expands when pelleted in the ultracentrifuge, but expansion can be prevented by fixing with glutaraldehyde. A low resolution model for the capsid I envelope has been developed.

Item Type:Thesis (Master's thesis)
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Stroud, Robert M.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 July 1977
Record Number:CaltechTHESIS:03302010-083049438
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5654
Deposited By: Tony Diaz
Deposited On:16 Apr 2010 16:40
Last Modified:02 Dec 2020 01:07

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