scholarly journals X-ray and UV Radiation Damage of dsDNA/Protein Complexes

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3132
Author(s):  
Paweł Wityk ◽  
Dorota Kostrzewa-Nowak ◽  
Beata Krawczyk ◽  
Michał Michalik ◽  
Robert Nowak
Keyword(s):  
Dna Damage ◽  
Simple Model ◽  
Uv Radiation ◽  
Protein Complexes ◽  
Chemical Processes ◽  
Model Systems ◽  
Degradation Pathways ◽  
X Ray ◽  
Physico Chemical ◽  
Sensitization Process

Radiation and photodynamic therapies are used for cancer treatment by targeting DNA. However, efficiency is limited due to physico-chemical processes and the insensitivity of native nucleobases to damage. Thus, incorporation of radio- and photosensitizers into these therapies should increase both efficacy and the yield of DNA damage. To date, studies of sensitization processes have been performed on simple model systems, e.g., buffered solutions of dsDNA or sensitizers alone. To fully understand the sensitization processes and to be able to develop new efficient sensitizers in the future, well established model systems are necessary. In the cell environment, DNA tightly interacts with proteins and incorporating this interaction is necessary to fully understand the DNA sensitization process. In this work, we used dsDNA/protein complexes labeled with photo- and radiosensitizers and investigated degradation pathways using LC-MS and HPLC after X-ray or UV radiation.

What does the biologist want from the physical scientist?

1987 ◽  
Vol 45 ◽  
pp. 538-539
Author(s):  
Michael Beer
Keyword(s):  
Nucleic Acid ◽  
Low Temperature ◽  
Protein Complexes ◽  
Simultaneous Detection ◽  
Inorganic Ions ◽  
Chemical Processes ◽  
X Ray ◽  
Carbon To Nitrogen Ratio ◽  
Acid Protein ◽  
Nitrogen Ratio

The Biologist is interested in discovering and then understanding the chemical processes in organisms. Crucial in his analysis is a knowledge of the structure of the system at various levels. At the level of the cell he must recognize the positions of particular macromolecules. For proteins or nucleoproteins this is best done with labeled antibodies. Inorganic ions like calcium or sodium can be localized by X-ray microprobe or EELS. From the designer he requires instruments in which the distribution of these species is not altered by the data collection. Specimen stability is favored by low temperature and efficient collection of data. That means simultaneous detection of all possible scattering events. Rapid display of the results as abundances requires computers of sufficient capability.Similar procedures look promising in the analysis of the structure of nucleic acid-protein complexes. Nucleic acids can be traced through phosphorus and protein through sulphur or perhaps carbon to nitrogen ratio.

Crystal chemistry and dissolution of calcium phosphate in dental enamel

1999 ◽  
Vol 63 (6) ◽  
pp. 791-800 ◽  
Author(s):  
S. E. P. Dowker ◽  
P. Anderson ◽  
J. C. Elliott ◽  
X. J. Gao
Keyword(s):  
Aqueous Media ◽  
Dental Enamel ◽  
Model Systems ◽  
X Ray ◽  
Physico Chemical ◽  
High Prevalence ◽  
Absorption Studies ◽  
X Ray Absorption ◽  
Inhomogeneous Porous Medium ◽  
Very High

AbstractThe mineral component (at least 95 wt. %) of dental enamel is hydroxyapatite (hydroxylapatite) with multiple substitutions. The biogenic origin of enamel is reflected in the unusual ribbon-like morphology of the crystals, which are extremely elongated in the c-axis direction, and their organized arrangement within the tissue. The study of enamel dissolution has been driven by the very high prevalence of dental caries. In enamel caries, the initial demineralization results in subsurface dissolution of mineral. While the surface remains intact, reversal of the lesion by remineralization is possible. Problems of understanding the physico-chemical processes in enamel demineralization include the general problems concerning the structure and chemistry of apatites formed in aqueous media. Added to these are the general problem of dissolution in an inhomogeneous porous medium and the complication that enamel apatite has a naturally variable composition which changes during demineralization. The use of model systems in caries research is illustrated by reference to X-ray absorption studies of enamel and synthetic analogues.

scholarly journals Study of Physico-Chemical Interactions during the Production of Silver Citrate Nanocomposites with Hemp Fiber

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2560
Author(s):  
Alexandru Cocean ◽  
Iuliana Cocean ◽  
Georgiana Cocean ◽  
Cristina Postolachi ◽  
Daniela Angelica Pricop ◽  
...  
Keyword(s):  
Thin Layer ◽  
Chemical Processes ◽  
Laser Deposition ◽  
Vibrational Modes ◽  
Hemp Fiber ◽  
X Ray ◽  
Eds Analysis ◽  
Physico Chemical ◽  
Silver Target ◽  
Hemp Fabric

In the study presented in this paper, the results obtained by producing nanocomposites consisting of a silver citrate thin layer deposited on hemp fiber surfaces are analyzed. Using the pulsed laser deposition (PLD) method applied to a silver target with impurities of nickel and iron, the formation of the silver citrate film is performed in various ways and the results are discussed based on Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy coupled with Energy Dispersive X-Ray (SEM-EDX) spectroscopy analyses. A mechanism of the physico-chemical processes that take place based on the FTIR vibrational modes and the elemental composition established by the SEM-EDS analysis is proposed. Inhibition of the fermentation process of Saccharomyces cerevisae is demonstrated for the nanocomposite material of the silver citrate thin layer, obtained by means of the PLD method, on hemp fabric. The usefulness of composite materials of this type can extend from sensors and optoelectronics to the medical fields of analysis and treatment.

Reconstruction of Chitin-Protein Complexes Using Correlation Averaging Methods: Ovipositor of the Ichneumon Fly Megarhyssa

1980 ◽  
Vol 38 ◽  
pp. 38-39
Author(s):  
L. T. Germinario ◽  
J. Blackwell ◽  
J. Frank
Keyword(s):  
Protein Complexes ◽  
Hexagonal Lattice ◽  
Uranyl Acetate ◽  
Optical Diffraction ◽  
Insect Cuticle ◽  
High Dose ◽  
Wide Angle ◽  
X Ray ◽  
Averaging Methods ◽  
Digital Correlation

This report describes the use of digital correlation and averaging methods 1,2 for the reconstruction of high dose electron micrographs of the chitin-protein complex from Megarhyssa ovipositor. Electron microscopy of uranyl acetate stained insect cuticle has demonstrated a hexagonal array of unstained chitin monofibrils, 2.4−3.0 nm in diameter, in a stained protein matrix3,4. Optical diffraction Indicated a hexagonal lattice with a = 5.1-8.3 nm3 A particularly well ordered complex is found in the ovipositor of the ichneumon fly Megarhyssa: the small angle x-ray data gives a = 7.25 nm, and the wide angle pattern shows that the protein consists of subunits arranged in a 61 helix, with an axial repeat of 3.06 nm5.

Investigation of the Effect of Uv-Assisted Oxidation and Nitridation of Hafnium Metal Films

2003 ◽  
Vol 780 ◽  
Author(s):  
C. Essary ◽  
V. Craciun ◽  
J. M. Howard ◽  
R. K. Singh
Keyword(s):  
Uv Radiation ◽  
Photoelectron Spectroscopy ◽  
Grazing Angle ◽  
X Ray Diffraction ◽  
Metal Thin Films ◽  
X Ray ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Silicon Interface

AbstractHf metal thin films were deposited on Si substrates using a pulsed laser deposition technique in vacuum and in ammonia ambients. The films were then oxidized at 400 °C in 300 Torr of O2. Half the samples were oxidized in the presence of ultraviolet (UV) radiation from a Hg lamp array. X-ray photoelectron spectroscopy, atomic force microscopy, and grazing angle X-ray diffraction were used to compare the crystallinity, roughness, and composition of the films. It has been found that UV radiation causes roughening of the films and also promotes crystallization at lower temperatures.Furthermore, increased silicon oxidation at the interface was noted with the UVirradiated samples and was shown to be in the form of a mixed layer using angle-resolved X-ray photoelectron spectroscopy. Incorporation of nitrogen into the film reduces the oxidation of the silicon interface.

Nucleophilicity and its parametrization

1989 ◽  
Vol 54 (1) ◽  
pp. 117-135
Author(s):  
Oldřich Pytela ◽  
Vítězslav Zima
Keyword(s):  
Regression Analysis ◽  
Linear Correlation ◽  
Correlation Equation ◽  
Chemical Processes ◽  
General Tendency ◽  
Orbital Interaction ◽  
Physico Chemical ◽  
Physical And Chemical ◽  
Two Parameter ◽  
Better Than

The method of conjugate deviations based on the regression analysis has been suggested for construction of a new nucleophilicity scale. This method has been applied to a set of 28 nucleophiles participating in 47 physical and chemical processes described in literature. The two-parameter nucleophilicity scale obtained represents-in the parameter denoted as ND-the general tendency to form a bond to an electrophile predominantly on the basis of the orbital interaction and-in the parameter denoted as PD-the ability to interact with a centre similar to the proton (basicity). The linear correlation equation involving the ND, PD parameters and the charge appears to be distinctly better than the most significant relations used. The correlation dependences have the physico-chemical meaning. From the position of individual nucleophiles in the space of the ND and PD parameters, some general conclusions have been derived about the factors governing the reactivity of nucleophiles.

scholarly journals Exposure of the cytoplasm to low-dose X-rays modifies ataxia telangiectasia mutated-mediated DNA damage responses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Munetoshi Maeda ◽  
Masanori Tomita ◽  
Mika Maeda ◽  
Hideki Matsumoto ◽  
Noriko Usami ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Ataxia Telangiectasia ◽  
Kinase Inhibitor ◽  
Surrogate Marker ◽  
X Rays ◽  
Ataxia Telangiectasia Mutated ◽  
Whole Cell ◽  
X Ray ◽  
Dna Damage Responses

AbstractWe recently showed that when a low X-ray dose is used, cell death is enhanced in nucleus-irradiated compared with whole-cell-irradiated cells; however, the role of the cytoplasm remains unclear. Here, we show changes in the DNA damage responses with or without X-ray microbeam irradiation of the cytoplasm. Phosphorylated histone H2AX foci, a surrogate marker for DNA double-strand breaks, in V79 and WI-38 cells are not observed in nucleus irradiations at ≤ 2 Gy, whereas they are observed in whole-cell irradiations. Addition of an ataxia telangiectasia mutated (ATM) kinase inhibitor to whole-cell irradiations suppresses foci formation at ≤ 2 Gy. ABL1 and p73 expression is upregulated following nucleus irradiation, suggesting the induction of p73-dependent cell death. Furthermore, CDKN1A (p21) is upregulated following whole-cell irradiation, indicating the induction of cell cycle arrest. These data reveal that cytoplasmic radioresponses modify ATM-mediated DNA damage responses and determine the fate of cells irradiated at low doses.

scholarly journals In situ monitoring of the influence of water on DNA radiation damage by near-ambient pressure X-ray photoelectron spectroscopy

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Marc Benjamin Hahn ◽  
Paul M. Dietrich ◽  
Jörg Radnik
Keyword(s):  
Dna Damage ◽  
Radiation Damage ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
In Situ Monitoring ◽  
Strong Increase ◽  
Oh Radicals ◽  
Strand Breaks ◽  
X Ray

AbstractIonizing radiation damage to DNA plays a fundamental role in cancer therapy. X-ray photoelectron-spectroscopy (XPS) allows simultaneous irradiation and damage monitoring. Although water radiolysis is essential for radiation damage, all previous XPS studies were performed in vacuum. Here we present near-ambient-pressure XPS experiments to directly measure DNA damage under water atmosphere. They permit in-situ monitoring of the effects of radicals on fully hydrated double-stranded DNA. The results allow us to distinguish direct damage, by photons and secondary low-energy electrons (LEE), from damage by hydroxyl radicals or hydration induced modifications of damage pathways. The exposure of dry DNA to x-rays leads to strand-breaks at the sugar-phosphate backbone, while deoxyribose and nucleobases are less affected. In contrast, a strong increase of DNA damage is observed in water, where OH-radicals are produced. In consequence, base damage and base release become predominant, even though the number of strand-breaks increases further.

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