Classical theory and calculations of circular dichroism in infinite helical polymers. [Polynucleotide sequences]

Technical Report · Wed Sep 01 04:00:00 EDT 1976

OSTI ID:7240498

Levin, A I

A new theory of optical activity in helical polymers is derived. Helical symmetry and periodic boundary conditions are applied to classical polarizability theory in order to express the infinite polymer result in closed form. Result is all order in inter-monomer interactions and gives the polymer circular dichroism bandshape in terms of monomer transition bandshapes. A complex unit of symmetry containing many optical transitions is also explicitly treated. This theory is applied to the following polynucleotide sequences: poly(A), poly(T), poly(G), poly(C), poly(A . T), poly(G . C), poly((A-T) . (A-T)), poly((G-C) . (G-C)), poly(A-T), poly(G-C), poly((A-G) . (C-T)), poly((A-C) . (G-T)), poly(A-C), poly(G-T), poly(A-G), poly(C-T) in RNA, and B and C form DNA geometries. Calculations are carried out for poly((A-A-T) . (A-T-T)) and poly((A-G-C) . (G-C-T)) in RNA and B-DNA geometries, and for polyadenylic acid and polyionsinic acid in nonstandard geometries. The CD difference spectra obtained upon melting of the two double-stranded polymers are very similar. Comparison of these difference spectra with calculated ones suggests that optical transitions near 272 nm (on A) and 288 nm (on T) are present. Premelting changes of the CD spectrum of poly(d(A-T) . d(A-T)) are due to a change in conformation in which the secondary structure goes from C- to B-type spectrum by increasing the A-type nature of the polymer. Such a change is not observed for poly(d(A) . d(T)); instead, a transition between two different B-type geometries occurs. 13 figures, 34 references. (DLC)

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7240498
• Report Number(s): LBL-5376
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360404* -- Materials-- Polymers & Plastics-- Physical Properties-- (-1987)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ANALYTICAL SOLUTION
CLASSICAL MECHANICS
COMPARATIVE EVALUATIONS
DICHROISM
ELECTROSTATICS
ENERGY-LEVEL TRANSITIONS
EQUATIONS
MECHANICS
MELTING
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHASE TRANSFORMATIONS
POLARIZATION
POLYMERS
SPECTRA
TEMPERATURE DEPENDENCE