𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Extrinsic cotton effect and helix-coil transition in a DNA-polycation complex

✍ Scribed by G. Bhat; A. C. Roth; R. A. Day

Publisher
Wiley (John Wiley & Sons)
Year
1977
Tongue
English
Weight
559 KB
Volume
16
Category
Article
ISSN
0006-3525

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

A strong, positive, extrinsic CD band ([θ]~242.5~ = ∼2 × 10^−3^ deg cm^2^/dmole) has been observed for a α‐bromo‐poly[methylene‐1,4‐phenylenecarbonyloxyethylene(dimethylamino) bromide] (I). The extrinsic Cotton effect is attributed to the ordered arrangement of the aromatic chromophores along the DNA helix.

The extrinsic band had a linear dependence on the amount of polycation I added from r ≤ 0.3 to r = ∼0.5, but decreased thereafter. Addition of the polycation decreased the positive CD band of DNA at 275 nm. The transformation of B → C form in the presence of salts or other polycations caused similar changes. The decrease in [θ]~275~ was reversed at higher concentrations of the polycation (r > 0.4).

Thermal denaturation studies indicated both stabilization of the helix conformation (Δ__t__~m~ = 21°C) and a high degree of cooperativity in the melting of DNA‐polycation complex as compared to native calf thymus DNA. Using the linear relationship between r (polycation residue/DNA phosphate) and F (fraction of bound base pairs), a value of 0.6 was derived for β (number of monomer residues of polycation/nucleotide).

Both electrostatic and hydrophobic effects probably influence the stability of the DNA‐polycation complex, since the strength of the 242.5 nm CD band is a function of both salt and urea concentrations.

📜 SIMILAR VOLUMES

Extrinsic cotton effect and helix-coil t
Extrinsic cotton effect and helix-coil transition in a DNA-polycation complex
✍ G. Bhat; A. C. Roth; R. A. Day 📂 Article 📅 1978 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 29 KB

On p. 1713 in the first line of the Synopsis the value for [8]242.5 should be -2.2 X deg deg cm2/dmole. Also, on p. 1716, fourth paragraph, line cm2/dmole instead of -2 X 3, the DNA is a solution of A = -0.5 units, not 0.05 units.

Helix–coil transition in nucleoprotein:
Helix–coil transition in nucleoprotein: Renaturation of polylysine–DNA and polylysine–nucleohistone complexes
✍ Hsueh Jei Li; Catherine Chang; Manuel Weiskopf; Benjamin Brand; Arnold Rotter 📂 Article 📅 1974 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 976 KB

## Abstract Thermal denaturation and renaturation of directly mixed and reconstituted polylysine–DNA, directly mixed polylysine–nucleohistone complexes, and NaCl‐treated nucleohistones in 2.5 × 10^−4^ __M__ EDTA, pH 8.0 have been studied. At the same input ratio of polylysine to DNA, the percent of

Helix–coil transition in nucleoprotein.
Helix–coil transition in nucleoprotein. Effect of ionic strength on thermal denaturation of polylysine–DNA complexes
✍ Hsueh Jei Li; Benjamin Brand; Arnold Rotter; Catherine Chang; Manuel Weiskope 📂 Article 📅 1974 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 938 KB

Thermal denaturation of direct-mixed and reconstituted polylysine-DNA complexes in 2.5 X 10-4 M EDTA, pH 8.0 and various concentrations of NaCl has been studied. For both complexes, increasing ionic strength of the solution raises T,, the melting temperature of free base pairs. The linear dependence

Ionic and structural effects on the ther
Ionic and structural effects on the thermal helix-coil transition of DNA complexed with natural and synthetic polyamines
✍ T. J. Thomas; V. A. Bloomfield 📂 Article 📅 1984 🏛 Wiley (John Wiley & Sons) 🌐 English ⚖ 604 KB

Polyamines are ubiquitous cellular components that interact strongly with nucleic acids. Although many of the interactions of oligocations with DNA can be rationalized with polyelectrolyte theories that treat counterions as point charges, some structural effects are evident. We have explored the eff