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Flow dichroism of capsid DNA phages. II. Effect of DNA deletions and intercalating dyes
Author(s) -
Hall Stephen B.,
Schellman John A.
Publication year - 1982
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360211007
Subject(s) - circular dichroism , linear dichroism , chemistry , dichroism , intercalation (chemistry) , dna , crystallography , bacteriophage , biophysics , escherichia coli , biochemistry , optics , biology , organic chemistry , physics , gene
The flow linear dichroism of bacteriophage λ and its deletion mutants, λ b2 and λ b221 , was determined. The hydrodynamic behavior of the three phages differed slightly, but the magnitude of the dichroism was substantially the same with 〈cos 2 θ μ p 〉 = 0.364, 0.368, and 0.372, respectively. The dichroism of intercalating dyes combined with bacteriophage was used as a further probe of phage structure. The reduced dichroism from proflavin with T4 showed no change with time during the reaction, but the interpretation of the ligand dichroism is complicated by an alteration of the hydrodynamic behavior of the phage–dye complex relative to the phage alone. Ethidium with λ also produced a stable reduced dichroism, but the signal indicated an average orientation of intercalated dye that is different from the average base orientation. The reduced dichroism of ethidium changes with time as it penetrates λ b2 , eventually approaching the dichroism of the nucleotide bases. The implication of these findings on the plausibility of various simple DNA packing models is discussed.