scholarly journals 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

1968 ◽  
Vol 108 (4) ◽  
pp. 599-610 ◽  
Author(s):  
R A Cox ◽  
K Kanagalingam
Keyword(s):  
Secondary Structure ◽  
Rat Liver ◽  
Ribosomal Rna ◽  
Phosphate Buffer ◽  
Sodium Phosphate ◽  
Double Helix ◽  
Spectrophotometric Study ◽  
Guanidinium Chloride ◽  
Base Pairs ◽  
Sodium Phosphate Buffer

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°, 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° 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.

scholarly journals Thermal denaturation in acidic solutions of double-helical ribonucleic acid from virus-like particles found in Penicillium chrysogenum. A spectrophotometric study

1971 ◽  
Vol 125 (2) ◽  
pp. 655-665 ◽  
Author(s):  
R. A. Cox ◽  
K. Kanagalingam ◽  
Elisabeth Sutherland
Keyword(s):  
Base Pair ◽  
Penicillium Chrysogenum ◽  
Sodium Phosphate ◽  
Thermal Denaturation ◽  
Spectrophotometric Study ◽  
Base Pairs ◽  
Native Form ◽  
Acidic Solutions ◽  
Ph Values ◽  
Sodium Phosphate Buffer

1. Two species of double-helical RNA isolated from mycelium of Penicillium chrysogenum were titrated with acid at 25°C and 95°C (solvent 0.1m-sodium phosphate buffer). At 25°C denaturation occurred at about pH3. At 95°C in the denatured form cytosine residues titrated as a simple monobasic acid of pK3.9 compared with pK≃2.5 for the native form at 25°C. 2. On thermal denaturation in neutral and acidic solutions one species of RNA (38% rG·rC) ‘melted’ in three distinct stages, equivalent to a mixture of three species, namely one of about 25% rG·rC, another of about 33% rG·rC and a third of about 46% rG·rC: the relative proportions were 0.25:0.35:0.40. 3. On thermal denaturation in acidic solutions the increase in the fraction of ionized cytosine residues concomitant with the ‘melting’ of rG·rC base pair also affects the spectrum especially at 280nm and serves to enhance the contribution of rG·rC base pairs at this wavelength. The increment in ε(P) at 280nm on ‘melting’ an rG·rC base pair approaches 53501·mol−1·cm−1 depending on pH, compared with 33501·mol−1·cm−1 at pH7. In contrast ε(P) at 280nm is scarcely affected by ‘melting’ rA·rU base pairs or by the protonization of adenine residues. 4. Changes in the spectrum of Escherichia coli rRNA on denaturation in acidic solutions were studied to yield the mole fractions of rA·rU and rG·rC base pairs ‘melting’ at particular pH values.

Effects of sodium phosphate buffer on horseradish peroxidase thermal stability

2008 ◽  
Vol 93 (2) ◽  
pp. 569-574 ◽  
Author(s):  
L. Haifeng ◽  
L. Yuwen ◽  
C. Xiaomin ◽  
W. Zhiyong ◽  
W. Cunxin
Keyword(s):  
Thermal Stability ◽  
Horseradish Peroxidase ◽  
Phosphate Buffer ◽  
Sodium Phosphate ◽  
Sodium Phosphate Buffer

scholarly journals A study of the alkaline hydrolysis of fractionated reticulocyte ribosomal ribonucleic acid and its relevance to secondary structure

1968 ◽  
Vol 106 (3) ◽  
pp. 733-741 ◽  
Author(s):  
R A Cox ◽  
Hannah J. Gould ◽  
K Kanagalingam
Keyword(s):  
Secondary Structure ◽  
Phosphate Buffer ◽  
Potassium Hydroxide ◽  
Chain Scission ◽  
Average Chain Length ◽  
Guanidinium Chloride ◽  
Stable Species ◽  
Hairpin Loops ◽  
Ribosomal Ribonucleic Acid ◽  
Hydrolysis Of

1. RNA isolated from the sub-units of rabbit reticulocyte ribosomes was hydrolysed by 0·4n-potassium hydroxide at 20°. The probability of main-chain scission was calculated from the number-average chain length, which was obtained from S25,w in 0·01m-phosphate buffer. 2. The fraction, f, of the original secondary structure that the fragments re-formed at neutral pH in 4m-guanidinium chloride, as well as in 0·01m- and 0·1m-phosphate buffer, was derived from changes in extinction over the range 220–310mμ on thermal denaturation. 3. The secondary structure of RNA is regarded as an assembly of hairpin loops each of 2N+b residues on average, where N is the number of base-paired residues and b is the number of unpaired residues. 4. If chain scission takes place at random then 2N+b=logf/log(1–p). 5. For RNA from the smaller sub-unit 2N+b was estimated as 25±5 residues, compared with 30±5 residues for the less stable species and 35±5 residues for the more stable species of hairpin loop of RNA from the larger sub-unit.

Recovery of milk fat globule membrane (MFGM) from buttermilk: effect of Ca-binding salts

2019 ◽  
Vol 86 (3) ◽  
pp. 374-376 ◽  
Author(s):  
Vitaly L. Spitsberg ◽  
Liza Ivanov ◽  
Vladimir Shritz
Keyword(s):  
Phosphate Buffer ◽  
Milk Fat ◽  
Sodium Phosphate ◽  
Milk Fat Globule Membrane ◽  
Peripheral Protein ◽  
Sodium Phosphate Buffer ◽  
Milk Fat Globule ◽  
Fat Globule ◽  
First Time ◽  
Phosphate Groups

AbstractIn this Research Communication we present a study of the effect of Ca-binding salts on the recovery of milk fat globule membrane (MFGM) from buttermilk. Sodium phosphate buffer was used for the purpose of MFGM recovery from buttermilk for the first time and we showed that 0.1 M buffer at pH 7.2 was the most effective for the recovery of MFGM. The fact of high efficacy of sodium phosphate buffer in recovery of MFGM from buttermilk allowed us to suggest that MFGM in buttermilk is present in association with casein through Ca- bridges formed between phospholipids of MFGM and phosphate groups of casein, primarily with k-casein as the peripheral protein of casein micelles.

scholarly journals A spectrophotometric study of the secondary structure of ribonucleic acid isolated from the smaller and larger ribosomal subparticles of rabbit reticulocytes

1970 ◽  
Vol 117 (1) ◽  
pp. 101-118 ◽  
Author(s):  
R. A. Cox
Keyword(s):  
Escherichia Coli ◽  
Ionic Strength ◽  
Secondary Structure ◽  
Ribonucleic Acid ◽  
Spectrophotometric Study ◽  
Urea Concentration ◽  
Model Systems ◽  
Base Pairs ◽  
Virus Like Particles ◽  
Rabbit Reticulocytes

The spectrum of RNA from the smaller and larger subparticles of rabbit reticulocyte ribosomes was studied as a function of pH, ionic strength, urea concentration and temperature. It was inferred that both RNA species form short double-helical segments of not more than about 10 base-pairs in length. Not more than about 70% of the base residues may be located in double-helical segments. RNA from the larger subparticle is richer in guanine and cytosine residues and its secondary structure is the more stable. These conclusions are based on the use of double-helical RNA from virus-like particles and of unfractionated Escherichia coli tRNA as model systems.

scholarly journals Large-scale purification of hepatitis B surface antigen

1976 ◽  
Vol 3 (6) ◽  
pp. 626-631
Author(s):  
J Vnek ◽  
A M Prince
Keyword(s):  
Polyethylene Glycol ◽  
Hepatitis B ◽  
Surface Antigen ◽  
Phosphate Buffer ◽  
Sodium Phosphate ◽  
Large Scale ◽  
Hepatitis B Surface Antigen ◽  
Sodium Phosphate Buffer ◽  
Subsequent Elution ◽  
Polyethylene Glycol Precipitation

Hepatitis B surface antigen was concentrated and purified from plasma by two simple steps of purification. In the first step the antigen was purified 24-fold by polyethylene glycol precipitation. An additional 10-fold purification was achieved by batchwise adsorption to hydroxylapatite and subsequent elution with 0.02 M sodium phosphate buffer.

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