Determination of guanine plus cytosine content in Streptococcus pyogenes

1975 ◽  
Vol 21 (5) ◽  
pp. 722-724 ◽  
Author(s):  
James G. Stuart ◽  
Joseph J. Ferretti
Keyword(s):  
Streptococcus Pyogenes ◽  
Thermal Denaturation ◽  
Buoyant Density ◽  
Density Analysis

The guanine and cytosine content of Streptococcus pyogenes DNA was determined by thermal denaturation and buoyant density analysis to be 36.7% and 38.7%, respectively.

Chromosome age and segregation during sporulation of Bacillus megaterium

1978 ◽  
Vol 24 (10) ◽  
pp. 1227-1235 ◽  
Author(s):  
Anthony D. Hitchins
Keyword(s):  
Bacillus Megaterium ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Buoyant Density ◽  
Growth Period ◽  
Circular Dna ◽  
Chromosomal Segregation ◽  
Seven Generations ◽  
Minor Correction

The effect of chromosome age on segregation during sporulation was investigated. Vegetative cells of Bacillus megaterium were labeled with [Me-3H]thymine and then were grown at 30 °C in nonradioactive medium for various times before being allowed to sporulate. The ratio of the amount of label in sporal DNA to that in sporangial DNA, obtained after minor correction for the sporulation frequency, remained essentially constant as the postlabeling growth period was increased from one to seven generations. The spores were preferentially located at the older poles of sporangia, i.e. the poles formed by divisions occurring prior to those forming the sporangia. Therefore, it seems that old (labeled) chromosomes segregate randomly with respect to both the morphological and genealogical polarities of sporangia. Examination of total cell lysates by dye–buoyant density gradient centrifugation revealed the presence of covalently closed circular DNA from cells grown at 37 °C, but none was obtained from cells grown at 30 °C. Thus, possible interference by large amounts of extrachromosomal DNA in the determination of the chromosomal segregation pattern is unlikely.

DNA base composition of Neisseria, Moraxella, and Acinetobacter, as determined by measurement of buoyant density in CsCl gradients

1969 ◽  
Vol 15 (4) ◽  
pp. 335-338 ◽  
Author(s):  
K. Bøvre ◽  
M. Fiandt ◽  
W. Szybalski
Keyword(s):  
Buoyant Density ◽  
Mutual Transformation ◽  
Supporting Evidence ◽  
Dna Base Composition ◽  
Group I ◽  
Dna Base ◽  
Wide Range ◽  
Additional Support ◽  
Neisseria Flavescens

The guanine + cytosine contents (%(G + C)) of DNAs from 75 strains of asaccharolytic Neisseria, Moraxella, and Acinetobacter have been determined by measuring their buoyant densities in the CsCl gradient. The main purpose was to provide supporting evidence for taxonomic conclusions based on assay of genetic transformation to streptomycin resistance among the same strains and species.Three groups of neisseriae can be recognized, both by determination of %(G + C) and by transformation assay: (i) Neisseria flavescens and N. cinerea (46.5–49%), (ii) N. catarrhalis (41–42.5%), and (iii) N. caviae and N. ovis (44.5–45%). There is no transformation compatibility between group (i) and the other groups, whereas groups (ii) and (iii) show mutual transformation interactions. N. catarrhalis, N. caviae, and N. ovis, therefore, can also be considered as one group of nonpigmented, asaccharolytic neisseriae.Four groups of moraxellae can be distinguished: (i) Moraxella nonliquefaciens, M. lacunata, M. liquefaciens, and M. bovis (40–43%), (ii) M. osloensis (43–43.5%), (iii) M. phenylpyrouvica (43–43.5%), and (iv) M. kingii (44.5%). Although groups (ii) and (iii) are identical in terms of %(G + C), they exhibit low transformation compatibility, of the same order as between groups (i) and (ii). The distinctly higher G + C content of M. kingii DNA is consistent with its lack of transformation compatibility with other moraxellae.The similar %(G + C) range for the moraxellae and the nonpigmented, asaccharolytic neisseriae is consistent with the finding of some transformation compatibility between most of these organisms (except M. kingii) and provides additional support for the assumption that they are closely related.The Acinetobacter strains studied exhibit a wide range of G + C contents (38–45%) and hardly any transformation compatibility with neisseriae and moraxellae, even if some of them have matching %(G + C).It can be concluded that determination of the G + C contents of bacterial DNAs provides useful supplementary taxonomic data, but has only limited value as a sole taxonomic criterion.

scholarly journals Charge density analysis of two proton transfer complexes: Understanding hydrogen bonding and determination of in-crystal dipole moments

2008 ◽  
Vol 120 (6) ◽  
pp. 613-620 ◽  
Author(s):  
Reji Thomas ◽  
Shrinwantu Pal ◽  
Ayan Datta ◽  
Mariusz K. Marchewka ◽  
Henryk Ratajczak ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Charge Density ◽  
Dipole Moments ◽  
Density Analysis

On the mycophage of Penicillium chrysogenum

1973 ◽  
Vol 19 (1) ◽  
pp. 97-103 ◽  
Author(s):  
C. H. Nash ◽  
R. J. Douthart ◽  
L. F. Ellis ◽  
R. M. Van Frank ◽  
J. P. Burnett ◽  
...  
Keyword(s):  
Ribonucleic Acid ◽  
Penicillium Chrysogenum ◽  
Thermal Denaturation ◽  
Buoyant Density ◽  
Ion Concentration ◽  
Contour Length ◽  
Viral Dsrna ◽  
Viral Particles ◽  
Profile Characteristic ◽  
Isopycnic Centrifugation

A mycovirus has been purified from mycelia of Penicillium chrysogenum by isopycnic centrifugation in sucrose and in CsCl. Viral particles band with a buoyant density of 1.20 in sucrose and 1.38 in CsCl. Particles have icosohedral symmetry, are 35 nm in diameter, and have an absorption profile characteristic of nucleoprotein. One enzymatic activity, RNA polymerase, is associated with the purified mycophage. Nucleic acid extracted from purified virus has a buoyant density in CS2SO4 of 1.61, a molar extinction coefficient of εp (258 nm) of 7200, a s20, w of 13.0, and a pattern of circular dichroism characteristic of double-helical ribonucleic acid. Molecules of this double-stranded ribonucleic acid (dsRNA), examined by electron microscopy, have a mean contour length of 0.86 μm which corresponds to a molecular weight of about 2.0 × 106 daltons. This dsRNA is resolved further by acrylamide gel electrophoresis into three closely spaced bands. Thermal denaturation of the viral dsRNA is dependent on ionic strength and gives a linear relationship with the negative logarithm of the sodium ion concentration.

scholarly journals Study of Physical and Mechanical Properties of Centrifuged Concrete

2019 ◽  
Vol 18 (4) ◽  
pp. 319-329
Author(s):  
I. I. Palevoda ◽  
S. M. Zhamoidzik ◽  
D. S. Nekhan ◽  
D. S. Batan
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Cross Section ◽  
Outer Layer ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Physical And Mechanical Properties ◽  
Concrete Mixture ◽  
Density Analysis

The paper presents a complex of laboratory and theoretical studies of physical and mechanical properties in centrifuged concrete while using samples of sectoral cross-section which are cut in layers from a finished product. A post made of concrete having B40 grade for compression strength and manufactured while using centrifugation with the help of РТЦ-5 machine. Assessment of heterogeneity across section thickness has been carried out by visual determination of composition changes in cross section, determination of strength, density of the obtained concrete samples, and water content over cross section of concrete mix. According to the results of a visual study on composition of a concrete structure it has been revealed that 1/8 part of the structure (from an inner surface) does not have a large aggregate. Later, as it moves to periphery, there is an increase in coarse aggregate and a decrease in size and number of cells between grains of gravel. An analysis of experimental data has shown that properties of the centrifuged concrete in samples being sawn in layers change significantly: density of concrete in samples of an inner layer is lower by 8 % than in samples of an outer layer, and compressive strength of concrete – by 34 %, water content of concrete mixture of samples of the inner layer has turned out to be by 43 % higher than in samples of the outer layer. Approximating curves showing regularities of changes in density, concrete strength, water content of concrete mixture over thickness have been constructed in the paper. Linear and exponential equations have been obtained that describe changes in physical and mechanical properties of centrifuged concrete over section depending on structure properties as a whole, which, taking into account the obtained correction factors k1 and k2, can be used with an acceptable level of confidence in practical calculations of centrifuged concrete structures. Relationship between strength of centrifuged concrete varying over cross section and action of a centrifugal force of inertia has been revealed in the paper. An equation has been obtained that relates the strength of centrifuged concrete to its density. Analysis of the research results makes it possible to assert that the main source of loading perception in centrifuged concrete structures is outer layers.

Determination of the Density Distribution of Human Platelets - Methodological Aspects and Comparison with Other Tests for Platelet Activation

1982 ◽  
Vol 47 (03) ◽  
pp. 239-243 ◽  
Author(s):  
B A van Oost ◽  
I H van Hien-Hagg ◽  
B F E Veldhuyzen ◽  
A P M Timmermans ◽  
J J Sixma
Keyword(s):  
Platelet Activation ◽  
Gradient Centrifugation ◽  
Buoyant Density ◽  
Human Platelets ◽  
Thrombotic Disease ◽  
Platelet Aggregate ◽  
Thrombotic Complications ◽  
Methodological Aspects ◽  
Function Testing

SummaryStimulation of human platelets to release results in decreased buoyant density. This decreased density provides a tool to detect circulating platelets which have participated in a thrombotic process. Platelet density gradient centrifugation using Stractan was standardized and the effects of anticoagulation, temperature, and osmolarity were investigated. In 7 out of 32 patients with thrombotic disease less dense platelets were found. Platelet activation in the patient group was also indicated by spontaneous aggregation (10/32), decreased circulating platelet aggregate ratios (5/24) and elevated plasma β-thromboglobulin levels (2/11). Several of these tests were also abnormal in diabetes mellitus thrombocytosis, leukaemia and several systemic diseases with thrombotic complications. The platelet density test using Stractan is reproducible and independent of other tests for platelet activation and is therefore potentially a useful extension of platelet function testing in patients with thrombotic disease.

Determination of the buoyant density of canine distemper virus by radioassay

1975 ◽  
Vol 47 (4) ◽  
pp. 319-329 ◽  
Author(s):  
Aileen M. T. Armitage ◽  
H. J. C. Cornwell ◽  
N. G. Wright ◽  
A. R. Weir
Keyword(s):  
Canine Distemper Virus ◽  
Buoyant Density ◽  
Canine Distemper
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