scholarly journals Single-strand nuclease action on heat-denatured spermiogenic chromatin.

1976 ◽  
Vol 24 (8) ◽  
pp. 901-907 ◽  
Author(s):  
J D Hunter ◽  
A J Bodner ◽  
F T Hatch ◽  
R L Balhorn ◽  
J A Mazrimas ◽  
...  
Keyword(s):  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Elevated Temperatures ◽  
Chromatin Condensation ◽  
Heat Denaturation ◽  
S1 Nuclease ◽  
Nuclease Digestion ◽  
Aldehyde Groups ◽  
Phosphate Groups

The aim of this study was to compare the sensitivity of chromatin from representative cellular stages of spermiogenesis to a single-strandeded nuclease after heat denaturation. Thermal denaturation of chromatin was assayed in situ in fixed round, elongating and elongated spermatids and in testicular sperm from mice. Production of single-stranded deoxyribonucleic acid (DNA) at elevated temperatures was monitored by digesting chromatin with endonuclease specific for single-stranded DNA (S1 nuclease), staining the residual DNA with gallocyanin-chrome alum (GAC) and measuring the stain content by absorption cytophotometry. Changes in GCA staining were minimal over the temperature range of 22-90 degrees C in each cell type not exposed to nuclease. Staining of undigested cells decreased progressively with advancing cell maturity. Nuclease had no effect on the GCA content of round spermatids below 60 degrees C, but above this temperature there was a progressive decrease in GCA-stainable chromatin. Both round and elongating spermatid stages showed a significantly greater sensitivity to nuclease digestion than did more mature stages; sperm showed no effects of nuclease action below 80 degrees C. Progressive chromatin condensation and a concomitant decrease in the number of available DNA phosphate groups during spermiogenic cell maturation may be responsible for the observed decline in sensitivity to nuclease and decreased GCA staining. Thermal denaturation of round spermatids labeled with 3H-thymidine produced no change in autoradiographic mean nuclear grain counts, indicating no loss of thymidine-labeled DNA from the slides during denaturation. When round spermatids and sperm were hydrolyzed with hot tricholoroacetic acid before staining, both nuclear GCA content and autoradiograph grain count were partially reduced, indicating incomplete DNA removal. Almost complete loss of Feulgen-stainable material occurred in these cells and may be due to depurination and elimination of Feulgren-reactant aldehyde groups.

Mesophilic mutants of an obligate psychrophile, Micrococcus cryophilus

1969 ◽  
Vol 15 (10) ◽  
pp. 1145-1150 ◽  
Author(s):  
P-C. Tai ◽  
H. Jackson
Keyword(s):  
Growth Temperature ◽  
Metabolic Pathways ◽  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Elevated Temperatures ◽  
Maximum Growth ◽  
Maximal Growth ◽  
Denaturation Temperature ◽  
Maximum Growth Temperature ◽  
Thermal Denaturation Temperature

Several mutants with elevated maximal growth temperature (MGT) were developed from an obligate psychrophile, Micrococcus cryophilus ATCC 15174, by ultraviolet irradiation. Two of the mutants, T8 and M19, have the most similar characteristics to those of their parent. The mutants lost the ability to grow well at 0 °C and showed changes in metabolic pathways while acquiring the ability to grow at elevated temperatures. Heat resistance and deoxyribonucleic acid thermal denaturation temperature were shown to be unrelated to maximum growth temperature. The significance of the mutants is discussed.

Denaturation of deoxyribonucleic acid in situ effect of formaldehyde.

1975 ◽  
Vol 23 (6) ◽  
pp. 431-438 ◽  
Author(s):  
F Traganos ◽  
Z Darzyndiewicz ◽  
T Sharpless ◽  
M R Melamed
Keyword(s):  
Deoxyribonucleic Acid ◽  
Direct Action ◽  
Chromatin Condensation ◽  
Cross Linking ◽  
Dna Denaturation ◽  
Cell Type ◽  
Dna Interactions ◽  
Flow Through ◽  
Nuclear Deoxyribonucleic Acid

In situ denaturation of nuclear deoxyribonucleic acid (DNA) is studied by use of acridine orange to differentially stain native versus denatured DNA, and a flow-through cytofluorometer for measurements of cell fluorescence. Thermal- or acid-induced DNA denaturation is markedly influenced by formaldehyde. Two mechanisms of the formaldehyde action are distinguished. If cells are exposed to the agent during heating, DNA denaturation is facilitated, most likely by the direct action of formaldehyde as a "passive" denaturing agent on DNA. If cells are pretreated with formaldehyde which is then removed, DNA resistance to denaturation increases, presumably due to chromatin cross-linking. It is believed that both effects occur simultaneously in conventional techniques employing formaldehyde to study DNA in situ, and that the extent of each varies with the temperature and cell type (chromatin condensation). Thus, profiles of DNA denaturation of cells heated with formaldehyde do not represent characteristics of DNA denaturation in situ; DNA denaturation under these conditions is modulated by the reactivity of chromatin components with formaldehyde rather than by DNA interactions with the macromolecules of nuclear mileu.

scholarly journals DEOXYRIBONUCLEIC ACID CYTOPHOTOMETRY OF STAINED HUMAN LEUKOCYTES III. THERMAL DENATURATION OF CHROMATIN

1974 ◽  
Vol 22 (2) ◽  
pp. 120-126 ◽  
Author(s):  
STEPHEN C. DRESKIN ◽  
BRIAN H. MAYALL
Keyword(s):  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Single Cells ◽  
Human Lymphocytes ◽  
Freeze Substitution ◽  
Enzymatic Digestion ◽  
Single Strand ◽  
Different Temperatures ◽  
Potential Methods

Thermal denaturation of chromatin has been monitored in situ in single cells using absorption cytophotometry on gallocyanin-chrome alum (GCA)-stained preparations. Spreads of human lymphocytes were fixed by ethanol freeze-substitution, digested with ribonuclease and treated at different temperatures prior to staining. Treatment in 0.15 M NaCl-0.0l5 M Na citrate (pH 7.0) for 10 min was followed by 0.15 M NaCl-0.0l5 M Na citrate (pH 7.0) with 10% formalin at the same temperature for 20 min. The GCA staining was localized to nuclei and was measured cell by cell with an integrating scanning cytophotometer. Cellular GCA stain content increased progressively with treatment temperatures above 60°C until 90°C, when it was about 1.5 times that of cells treated at 22°C. Formation of single strand deoxyribonucleic acid at different temperatures was monitored by digesting slides with an endonuclease that is specific for single strand nucleic acids and then staining with GCA. Digestion had little effect on slides that had been treated at less than 70°C, but above this temperature it caused a progressive decrease in stain content up to 90°C, when the stain content was reduced to about one-half that of undigested cells. Both with and without enzymatic digestion, these new approaches to monitoring chromatin denaturation yield preparations that are stable and can be measured on any visible light absorption cytophotometer; in addition, the enzymatic approach exemplifies a class of potential methods in which biochemical procedures are adapted to cytophotometry.

scholarly journals Fractionation of chick oviduct chromatin. Nuclease-resistant deoxyribonucleic acid

1975 ◽  
Vol 151 (3) ◽  
pp. 497-503 ◽  
Author(s):  
J F Krall ◽  
S H Socher ◽  
N T Van ◽  
B W O'Malley
Keyword(s):  
Dna Sequences ◽  
Thermal Denaturation ◽  
Tissue Specificity ◽  
Deoxyribonucleic Acid ◽  
Micrococcal Nuclease ◽  
Chromosomal Protein ◽  
Nuclease Digestion ◽  
Nuclease Resistance ◽  
Limited Degree ◽  
Chromatin Proteins

Chromatin isolated from several chick tissues was treated with micrococcal nuclease. A limited degree of tissue specificity of chromatin DNA resistance to nuclease digestion was observed. No difference in the extent of nuclease resistance of chromatin DNA was detected during oestrogen-induced oviduct differentiation. This suggested that the amount of non-histone chromosomal protein does not play an important role in the sensitivity of chromatin DNA to nuclease digestion. Studies of nuclease resistance of chromatin DNA after dissociation and reconstitution of chromatin proteins and ethanol extraction of chromatin indicate that the histones protect the DNA from nuclease attack. Slow thermal denaturation of nuclease-resistant DNA suggests that the protected DNA sequences may be (A+T)-rich, and the (G+C)-rich satellites present in total chick DNA are sensitive to nuclease.

Detection and mapping of interactions between chromatin and the nuclear envelope in drosophila embryos

1995 ◽  
Vol 53 ◽  
pp. 764-765
Author(s):  
W.F. Marshall ◽  
A.F. Dernburg ◽  
B. Harmon ◽  
J.W. Sedat
Keyword(s):  
Nuclear Envelope ◽  
Chromatin Condensation ◽  
Three Dimensional ◽  
Physiological Role ◽  
Nuclear Surface ◽  
Intact Cells ◽  
Molecular Determinants ◽  
Surface Harmonic ◽  
Drosophila Embryos

Interactions between chromatin and nuclear envelope (NE) have been implicated in chromatin condensation, gene regulation, nuclear reassembly, and organization of chromosomes within the nucleus. To further investigate the physiological role played by such interactions, it will be necessary to determine which loci specifically interact with the nuclear envelope. This will not only facilitate identification of the molecular determinants of this interaction, but will also allow manipulation of the pattern of chromatin-NE interactions to probe possible functions. We have developed a microscopic approach to detect and map chromatin-NE interactions inside intact cells.Fluorescence in situ hybridization (FISH) is used to localize specific chromosomal regions within the nucleus of Drosophila embryos and anti-lamin immunofluorescence is used to detect the nuclear envelope. Widefield deconvolution microscopy is then used to obtain a three-dimensional image of the sample (Fig. 1). The nuclear surface is represented by a surface-harmonic expansion (Fig 2). A statistical test for association of the FISH spot with the surface is then performed.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

In Situ Polymerized Protic Ionogels for Fuel Cells at Elevated Temperatures

2021 ◽  
Author(s):  
Mengdou Zou ◽  
Jie Luo ◽  
Xurui Wang ◽  
Shuai Tan ◽  
Caihong Wang ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Elevated Temperatures

scholarly journals Phosphorus Kβ X-Ray emission spectroscopy detects non-covalent interactions of phosphate biomolecules in situ

2021 ◽  
Author(s):  
Zachary Mathe ◽  
Olivia McCubbin Stepanic ◽  
Sergey Peredkov ◽  
Serena DeBeer
Keyword(s):  
Nucleic Acids ◽  
Emission Spectroscopy ◽  
Adenine Nucleotides ◽  
X Ray ◽  
Non Covalent Interactions ◽  
Covalent Interactions ◽  
Phosphate Groups

Phosphorus is ubiquitous in biochemistry, found in the phosphate groups of nucleic acids and the energy-transferring system of adenine nucleotides (e.g. ATP). Kβ X-ray emission spectroscopy (XES) at phosphorus has...

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

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