The pressure dependence of the buoyant density of DNA as a function of base composition

Biopolymers ◽  
1971 ◽  
Vol 10 (12) ◽  
pp. 2615-2617 ◽  
Author(s):  
William Bauer ◽  
Fred Prindaville ◽  
Jerome Vinograd
Keyword(s):  
Pressure Dependence ◽  
Base Composition ◽  
Buoyant Density

scholarly journals FURTHER STUDIES OF INFECTIOUS DNA EXTRACTED FROM MYCOBACTERIOPHAGES

1966 ◽  
Vol 123 (2) ◽  
pp. 327-340 ◽  
Author(s):  
Margret I. Sellers ◽  
Tohru Tokunaga
Keyword(s):  
Mycobacterium Smegmatis ◽  
Base Composition ◽  
Thermal Denaturation ◽  
Buoyant Density ◽  
Plaque Formation ◽  
Double Stranded Dna ◽  
Calf Thymus ◽  
Phage Dna ◽  
Dna Thermal Denaturation ◽  
Adenine Thymine

Results of the previous investigation in which it was found that DNA extracted from D29 mycobacteriophage was infectious for Mycobacterium smegmatis 607, have been extended. DNA extracted from mycobacteriophage D4 and D32 produced plaques when plated on their respective hosts; D28 DNA, extracted in the same manner and tested under similar conditions, failed to show infectivity. Species barriers were not crossed by mycobacteriophage DNA; bacteria resistant to intact phage were not infected with the phage DNA. The efficiency of plating of the DNA is very much lower than that of intact phage; infection of a given host was not accomplished by DNA when titration for plaque formation by the intact phage was less than 109 PFU. The base composition of DNA extracted from the four mycobacteriophages and the three propagating hosts was very similar. The bases were paired, adenine with thymine and guanine with cytosine. A relatively higher per cent of guanine-cytosine than of adenine-thymine, was found. The buoyant density of each DNA in CsCl was linearly related to its guanine-cytosine content whereas with the exception of D28 DNA, thermal denaturation temperatures failed to show this relationship. However, the thermal transition profiles were characteristic of double stranded DNA. Additional evidence that D29 DNA forms complexes with basic proteins was obtained. Binding between calf thymus histone and between RNAase and D29 DNA readily occurs with a resultant loss in DNA infectivity. Trypsin and D29 DNA are only weakly reactive.

Dependence of the buoyant density of single-stranded DNA on base composition

1969 ◽  
Vol 45 (2) ◽  
pp. 367-374 ◽  
Author(s):  
Silvano Riva ◽  
Italo Barrai ◽  
Luigi Cavalli-Sforza ◽  
Arturo Falaschi
Keyword(s):  
Base Composition ◽  
Buoyant Density ◽  
Single Stranded Dna

Mise en évidence d'ADN extrachromosomique chez Rhizobium meliloti

1978 ◽  
Vol 24 (8) ◽  
pp. 960-966 ◽  
Author(s):  
M. Bechet ◽  
J. B. Guillaume
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Base Composition ◽  
Density Gradient Centrifugation ◽  
Rhizobium Meliloti ◽  
Gradient Centrifugation ◽  
Buoyant Density ◽  
Sedimentation Analysis ◽  
Extrachromosomal Dna ◽  
Very High

Seven effective (nitrogen-fixing) strains of Rhizobium meliloti have been studied. By sedimentation analysis of their alkaline lysates in alkaline sucrose gradients, a plasmid was found in four strains. In a strain (2011 str 3) which gave no result with this method, supercoiled DNA was detected by CsCl-dye buoyant density gradient centrifugation. That result was confirmed by analytical Cs2SO4–Ag+ density gradients, which showed a heterogeneity in the average base composition of the DNA extracted from three strains, including the 2011 str 3 strain. Two of those last strains seemed to contain an extrachromosomal DNA of very high molecular weight.

scholarly journals Characterization of cytoplasmic and nuclear genomes in the colorless alga Polytoma. II. General characterization of organelle nucleic acids.

1976 ◽  
Vol 69 (2) ◽  
pp. 371-382 ◽  
Author(s):  
C Siu ◽  
H Swift ◽  
K Chiang
Keyword(s):  
Nucleic Acids ◽  
Chlamydomonas Reinhardtii ◽  
Ribosomal Rna ◽  
Base Composition ◽  
Buoyant Density ◽  
Main Band ◽  
Major Species ◽  
A Minor ◽  
Cytoplasmic Ribosomes

Polytoma obtusum has a main band DNA (alpha) with a buoyant density in CsC1 of rho = 1.711 g/ml and a light DNA satellite (beta) with rho = 1.682 g/ml. beta-DNA was substantially enriched in a fraction containing small leucoplast fragments and some mitochondria, which was obtained in a pellet sedimenting between 3,000 g and 5,000 g. A crude mitochondrial pellet was also obtained by sedimenting at 12,000 g to recover particulates remaining in the supernate after 10 min at 5,000 g. This fraction contained a third DNA component (gamma) with rho = 1.714 g/ml. We have concluded that the leucoplasts of P. obtusum contain the beta-DNA (1.6882) and the mitochondria possess the gamma-component (1.714). Two distinct classess of ribosomes were isolated and separated by sucrose density gradients, a major 79S species and a minor species at 75S. The major species possessed the 25S and 18S ribosomal RNA (rRNA), characteristic of cytoplasmic ribosomes, and these particles co-sedimented in sucrose gradients with the 79S cytoplasmic ribosomes of Chlamydomonas reinhardtii. The minor species was present in about 2% of the total ribosomal population but showed an eight-to-ninefold enrichment in the leucoplast pellet, suggesting that it was of organelle origin. These 73S particles had RNA components migrating very closely with the 18S and 25S species of the 79S ribosomes, but the base composition of the rRNA from these two classes of ribosomes was significantly different; the rRNA from the 79S ribosomes had a G+C mole ratio of 50.0%, while the rRNA from the 73S class had a ratio of 47.5%. By comparison, chloroplast ribosomes of C. reinhardtii were found to sediment at 70S and contain rRNA molecules of 23S and 16S, with a G + C content of 51.0%. These findings support the concept that the Polytoma leucoplast possesses characteristic genetic and protein-forming systems.

DNA BASE COMPOSITION OF SOME FREE-LIVING NEMATODE SPECIES

1969 ◽  
Vol 11 (4) ◽  
pp. 993-1000 ◽  
Author(s):  
R. Behme ◽  
J. Pasternak
Keyword(s):  
Refractive Index ◽  
Base Composition ◽  
Buoyant Density ◽  
Gc Content ◽  
Nematode Species ◽  
Refractive Index Gradient ◽  
Free Living ◽  
Dna Base Composition ◽  
Dna Base ◽  
Dnase Treatment

The mean base compositions (% GC) of DNA samples from five free-living nematodes were determined by CsCl equilibrium buoyant-density centrifugation and thermal denaturation studies. Both methods gave similar results indicating that there is no extensive replacement of the usual bases in nematode DNA. From the ultracentrifugation studies the % GC content of the DNA of Caenorhabditis briggsae (Dougherty and Nigon, 1949) Dougherty, 1953, Turbatrix aceti (Müller, 1783) Peters, 1927, Rhabditis (Rhabditis) anomala Hertwig, 1922 (Dougherty 1955), Panagrellus redivivus (Linn, 1767) T. Goodey, 1945, and Panagrellus silusiae (de Man, 1913) T. Goodey, 1945 was 36, 40, 42, 44 and 44, respectively.The sample of DNA from T. aceti showed two distinct ultraviolet absorbing bands in a CsCl gradient. The band at 1.688 g/cm3 proved to be a polysaccharide. It gave a distinctive refractive index pattern when viewed with the schlieren optical system, was insensitive to DNase treatment and was removed by a-amylase treatment. On the other hand, the material banding at 1.699 g/cm3 was shown to be DNA. This band produced no disturbance in the refractive index gradient. It was not altered by a-amylase treatment, but it was DNase sensitive.Since P. redivivus and P. silusiae were found to have the same DNA base composition their ability to interbreed was examined. These two forms were cross-fertile and the offspring were fully fertile.

scholarly journals Physicochemical properties of kinetoplast DNA from Crithidia acanthocephali. Crithidia luciliae, and Trypanosoma lewisi.

1975 ◽  
Vol 67 (2) ◽  
pp. 378-399 ◽  
Author(s):  
D L Fouts ◽  
J E Manning ◽  
D R Wolstenholme
Keyword(s):  
Base Composition ◽  
Unit Length ◽  
Buoyant Density ◽  
Cesium Chloride ◽  
Kinetoplast Dna ◽  
Molar Ratios ◽  
Trypanosoma Lewisi ◽  
Crithidia Luciliae ◽  
Sequence Homologies ◽  
Thermal Melting

The protozoa Crithidia and Trypanosoma contain within a mitochondrion a mass of DNA known as kinetoplast DNA (kDNA) which consists mainly of an association of thousands of small circular molecules of similar size held together by topological interlocking. Using kDNA from Crithidia acanthocephali, Crithidia luciliae, and Trypanosoma lewisi, physicochemical studies have been carried out with intact associations and with fractions of covalently closed single circular molecules, and of open single circular and unit length linear molecules obtained from kDNA associations by sonication, sucrose sedimentation, and cesium chloride-ethidium bromide equilibrium centrifugation. Buoyant density analyses failed to provide evidence for base composition heterogeneity among kDNA molecules within a species. The complementary nucleotide strands of kDNA molecules of all three species had distinct buoyant densities in both alkaline and neutral cesium chloride. For C. acanthocephali kDNA, these buoyant density differences were shown to be a reflection of differences in base composition between the complementary nucleotide strands. The molar ratios of adenine: thymine:guanine:cytosine, obtained from deoxyribonucleotide analyses were 16.8:41.0:28.1:14.1 for the heavy strand and 41.6:16.6:12.8:29.0 for the light strand. Covalently closed single circular molecules of C. acanthocephali (as well as intact kDNA associations of C. acanthocephali and T. lewisi) formed a single band in alkaline cesium chloride gradients, indicating their component nucleotide strands to be alkaline insensitive. Data from buoyant density, base composition, and thermal melting analyses suggested that minor bases are either rare or absent in Crithidia kDNA. The kinetics of renaturation of 32P labeled C. acanthocephali kDNA measured using hydroxyapatite chromatography were consistent with at least 70% of the circular molecules of this DNA having the same nucleotide sequence. Evidence for sequence homologies among the kDNAs of all three species was obtained from buoyant density analyses of DNA in annealed mixtures containing one component kDNA strand from each of two species.

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