A spectrophotometric study of the denaturation of deoxyribonucleic acid in the presence of urea or formaldehyde and its relevance to the secondary structure of single-stranded polynucleotides

Abstract

1. The thermal denaturation of DNA from rat liver was studied spectrophotometrically. In sodium phosphate buffers denaturation led to a single-stranded form having, at 25 degrees , about 25% of the hypochromism of the intact double helix. 2. The hypochromism of the denatured form was the same in 1mm- as in 10mm-sodium phosphate buffer and was scarcely affected by reaction with formaldehyde. The hypochromism was decreased by about 40% in the presence of 8m-urea. 3. The hypochromism of denatured DNA at low ionic strengths was about the same as that of fragments of reticulocyte ribosomal RNA that were too short to form double-helical secondary structure and about the same as that of RNA after reaction with formaldehyde. 4. The spectrum of DNA was slightly affected by the presence of 8m-urea or 4m-guanidinium chloride. The differences in the spectrum of the native and denatured forms of DNA in 0.1m-sodium phosphate buffer, in 8m-urea-10mm-sodium phosphate buffer and in 4m-guanidinium chloride-10mm-sodium phosphate buffer, pH7.6, were similar but not identical. 5. Denatured rat liver DNA appears to have no double-helical character at 25 degrees in 10mm-sodium phosphate buffer, pH7.6; increasing the buffer concentration to 0.1m leads to a more compact form in which about 40% of the residues form base pairs.

A single‐step procedure for the isolation of individual mRNA species from crude lysates of Physarum polycephalum

“…1251- Iabelled poly(A)+-mRNA hybrid was 75°C in 0.1 x SSC and was 65°C in 0.01 x SSC (table 2). The shift of 10°C for a IO-fold decrease in the buffer concentration is in accord with a 12°C shift noted for rat liver DNA [22] and also with a shift of 13°C noted for double-stranded RNA isolated from virus-like particles of Penicillium chrysogenum [23]. The high resistance of the RNA -DNA hybrid to RNase treatment (table 2) reveals the absence of long tails of non-hybridised mRNA.…”

Inhibition of NaCl-induced heat shock protein 72 expression renders MDCK cells susceptible to high urea concentrations

“…The blots were stripped and rehybridized for GAPDH to demonstrate comparable RNA loading Fig. 5A tions, which are easily reached in the papilla of the concentrating kidney, inhibit enzyme functions, have denaturing effects on nucleic acids and other cellular macromolecules, and promote apoptosis in inner medullary collecting duct cells [6,13,21]. In agreement with a recent report by Sheikh-Hamad and coworkers [20], the highly specific p38 kinase inhibitor SB203580, added at a concentration of 100 µM to the hypertonic medium, significantly reduced HSP72 mRNA expression.…”

Urea stress is more akin to EGF exposure than to hypertonic stress in renal medullary cells

“…Urea is a potent denaturant of proteins (35) and nucleic acids (10). Urea increases expression of the stress-responsive transcription factor Gadd153 (40) and the cytoprotective enzyme heme oxygenase-1 (30) in an oxidative stress-depen- Fig.…”