Water-soluble lysine-containing polypeptides. III. Sequential lysine-glycine polypeptides. A circular dichroism and electron microscopy study of annealed complexes with DNA, sonicated DNA, and denatured DNA

Abstract

. Can. J. Cheni. 54, 3884 (1976). Circular dichroic spectra, turbidity n~easuren~ents, and electron micrographs have been taken of annealled complexes of native, sonicated. and denat~~red DNA's in association with several sequential lysine-glycine copolypeptides. The results indicate that: (I) the n~olecular weigh: and strandedness of the DNA influences not only the assymmetric orgaiiization of the DNA in the complexes but also the size and shape of the complexes formed; (2) the hydrophobic nature (or sequence) of the polypeptide influences the shape of the complexes formed.SANDRA L. KIELLAND et Ross E. WILLIA~IS. Can. J. Chem. 54, 3884 (1976). Des spectres du dichroi'sme circulaire, des rnesures de turbidit6 ansi que des micrographics electroniques cle complexes entre 1'ADN (nature!, trait6 aux ultrasons et denature) et quelques poljpeptides lysine-glycine de sequence regulikre ont Ct C pris. Les rCsultats niontrent que: (I) la presence de cleux chaines associees dans la molCcule de 1'ADN ainsi que le poids mol6cu-iaire de celle-ci influence non seulenient l'organisation asymetrique de 1'ADN dans les complexes mais aussi la grandeur et la forme de ces derniers; (2) la forme des complexes dCpend de la nature hydrophobique (ou i6quence) du polypeptide.

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

“…Using X-ray diffraction to address the structure within polyamine-DNA condensates, Schellman and Parthasarathy (1984) discard the notion of stabilization due to long-range electrostatic repulsive and attractive forces but suggest the condensate is some sort of liquid crystal with counterions between the helices resulting in a stable three-dimensional phase of high structural order. This liquid-crystalline state is also the model favored by Kielland and Williams (1976). DNA condensates may have enough long-range order to show that order in X-ray diffraction studies (Maniatis et al, 1974;Schellman & Parthasarathy, 1984), but there may be enough long-range chiral order to affect the CD of the DNA condensates.…”

“…Electron microscopy on sppermidine-DNA condensates (Marx & Ruben, 1983) showed that these particular condensates are toroids. On the other hand, Kielland and Williams (1976) used electron microscopy to observe negative condensates formed from DNA and poly(amino acids) by NaCl gradients and found many different preparation-dependent condensates. Using X-ray diffraction to address the structure within polyamine-DNA condensates, Schellman and Parthasarathy (1984) discard the notion of stabilization due to long-range electrostatic repulsive and attractive forces but suggest the condensate is some sort of liquid crystal with counterions between the helices resulting in a stable three-dimensional phase of high structural order.…”

“…X-ray diffraction of fibers pulled from solutions of DNA condensates show the B conformation for the secondary structure of DNA (Maniatis, 1974). This has lead to the proposal that the anomalous CD spectra of DNA condensates are due to liquid-crystal-like packing of the DNA (Kielland & Williams, 1976; Reich et al, 1980; . Evdokimov (1983) has shown that the CD spectrum of the DNA binding drug daunomycin is altered when bound to condensates.…”