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Ultraviolet dichroism of fd bacteriophage
1Department ofBiophysics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Biophysical Journal
|February 13, 2009
Summary
Ultraviolet dichroism reveals the internal structure of the bacterial virus fd. DNA and protein components exhibit distinct orientations, providing insights into viral architecture.
Area of Science:
- Biophysics
- Structural Biology
- Molecular Virology
Background:
- Bacterial virus fd (filamentous phage) structure is crucial for its biological function.
- Understanding the precise arrangement of DNA and proteins within fd is key to viral assembly and infection mechanisms.
Purpose of the Study:
- To investigate the internal structure of bacterial virus fd.
- To determine the orientation of DNA and protein components within the virus particle.
Main Methods:
- Oriented ultraviolet (UV) dichroism measurements of fd virus solutions.
- Flow orientation through a capillary tube to align virus particles.
- Analysis using a theoretical model incorporating DNA and protein absorption spectra.
Main Results:
- UV dichroism exhibited positive values at >262 nm and <239 nm, and negative values in between.
- Dichroic ratios were measured at 280 nm (1.22) and 250 nm (0.83).
- Calculated DNA base plane semiangle of 25° ±5°, with protein (tryptophan, tyrosine) oriented parallel to the virus axis.
Conclusions:
- The observed dichroism results from the additive effects of negative DNA dichroism and positive protein dichroism.
- The study successfully determined the semiangle of the cone described by DNA base plane normals.
- Protein components are predominantly aligned with the longitudinal axis of the fd virus.
