Circular differential scattering and circular differential absorption of DNA-protein condensates and of dyes bound to DNA-protein condensates

Abstract

DNA-protein condensates that give positive and negative psi-type circular dichroism (CD) spectra (psi condensates) bind intercalative and nonintercalative dyes. CD depends both on circular differential scattering and on circular differential absorption; scattering-corrected CD measurements are approximations to circular differential absorption. The circular differential scattering and scattering-corrected CD patterns observed in the DNA absorption band of psi condensates are mimicked in the induced CD band of intercalators bound to psi condensates. The induced scattering-corrected CD and circular differential scattering patterns of the groove-binding dye Hoechst 33342 bound to psi condensates are the inverse of the patterns seen with intercalative dyes, whereas the groove-binding dye manganese(III) meso-tetrakis(4-N-methylpyridyl)porphine [MnIIITMpyP-4] shows no significant induced CD patterns. The large circular differential scattering and scattering-corrected CD bands are interpreted as resulting from long-range chiral packing, rather than near-neighbor short-range interactions. Dyes intercalated into the DNA of the psi condensates have the same type of long-range chiral packing as the DNA bases. Therefore, the psi-type CD spectra seen in the UV spectra originating from the long-range packing of the DNA bases are also observed in the visible spectra when dyes are intercalated in the DNA of the psi condensates. Our interpretation comes from the observation that the induced circular differential scattering and circular differential absorption of the dye bound to the psi condensates depend only upon the sign of the circular differential absorption and the pattern of the circular differential scattering of the psi condensates without bound dye.(ABSTRACT TRUNCATED AT 250 WORDS)

Chiral carbon dots and their effect on the optical properties of photosensitizers

“…The redshiing (210 nm to 270 nm) of the CD spectra for the same precursor molecules (Dand L-methionine) may be due to the absorption attening (AF) and circular differential scattering phenomena exhibited by biomolecules. 36 Castiglioni et al showed that absorption attening (AF) and light scattering (LS) are mainly observed in the case of an aggregate system, and this is true for our carbon dot system as we synthesize carbon dots using a bottom-up approach from different biomolecules. 37 There is a report that solvents can also affect the CD spectra.…”

Structural contributions to the intracellular targeting strategies of antimicrobial peptides

“…Adding more than four molar equivalents of buforin II amide to the DNA duplex leads to the formation of a DNA condensate with the spectra then dominated by circular intensity differential light scattering. The spectra obtained for buforin II amide DNA condensates are similar in appearance to those observed for positive ψ condensates formed by incubating DNA with poly(lysine-alanine) and are indicative of the formation of structures with long range order [42]. Interestingly buforin II amide, bound to the DNA duplex in the concentration range inducing the initial changes in near-UV CD, is shown to adopt an extended conformation rather than the helical conformation adopted in membranes or proposed from an MD simulation study [9].…”

Circular dichroism and the interactions of water soluble porphyrins with DNA—A minireview

“…Nonintercalators either give no signal or signals which do not correlate with whether they are bound to (+) or (−). 15,16 The electron density of intercalated porphyrins couple to that of the polynucleotide "antenna" 15 and this self-recognition and communication among the porphyrin moieties is accomplished without direct contact among them. Through the use of resonance light scattering (RLS), discussed below, we could show that the porphyrins do not form self-aggregates under the conditions at which they produce enhanced CD signals with psi condensates.…”