The action of photochemically generated radicals from hydrogen peroxide on deoxyribonucleic acid and simple model substances

1953 ◽  
Vol 141 (905) ◽  
pp. 562-580 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Simple Model ◽  
Deoxyribonucleic Acid ◽  
Ultra Violet ◽  
Phosphate Esters ◽  
Appreciable Effect ◽  
X Rays ◽  
Simple Assumption ◽  
Model Substances ◽  
Quartz Tubes

The effects on deoxyribonucleic acid (DNA) and simple model substances of irradiation with ultra-violet and near ultra-violet light have been studied in the presence of hydrogen peroxide at various concentrations in glass and quartz tubes. It is found that the rate of loss of the viscosity agrees with that caused by X-rays, on the simple assumption that each hydrogen peroxide molecule decomposed gives rise to two hydroxyl radicals. Oxygen has very little effect on the actions of the irradiation in glass tubes, but has an appreciable effect in quartz tubes. The following processes have been noted: (1) breakage of the phosphate-sugar link; (2) oxidation of the sugar; (3) fission of the bonds between the sugar and the bases; (4) oxidation of the bases; (5) liberation of the free phosphate. The liberation of phosphate from DNA as well as mono-, di- and tri-ethylphosphates and simple nucleotides has been studied. The results are in accordance with the hypothesis that liberation of phosphate from mono-phosphate esters occurs as the result of a simple re­action; while that of di- and tri-phosphate esters occurs as the result of two and three con­secutive reactions, respectively. DNA behaves as a di-ester and the fraction of phosphate-sugar links broken in unit time in the irradiation calculated on this basis is in close agreement with that observed in the case of simpler phosphate esters. The liberation of free phosphate occurs as a consequence of the oxidation of the alkyl or sugar groups.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

scholarly journals New Polyporphyrin Arrays with Controlled Fluorescence Obtained by Diaxial Sn(IV)-Porphyrin Phenolates Chelation with Cu2+ Cation

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 829
Author(s):  
Galina M. Mamardashvili ◽  
Dmitriy A. Lazovskiy ◽  
Ilya A. Khodov ◽  
Artem E. Efimov ◽  
Nugzar Z. Mamardashvili
Keyword(s):  
Chemical Species ◽  
Ultra Violet ◽  
X Rays ◽  
Structure And Properties ◽  
Paramagnetic Resonance ◽  
1H Nuclear Magnetic Resonance ◽  
Infra Red ◽  
Connection Type ◽  
Chelation Reaction ◽  
Electron Paramagnetic

New coordination oligomers and polymers of Sn(IV)-tetra(4-sulfonatophenyl)porphyrin have been constructed by the chelation reaction of its diaxialphenolates with Cu2+. The structure and properties of the synthesized polyporphyrin arrays were investigated by 1H Nuclear Magnetic Resonance (1H NMR), Infra Red (IR), Ultra Violet - Visible (UV-Vis) and fluorescence spectroscopy, mass spectrometry, Powder X-Rays Diffraction (PXRD), Electron Paramagnetic Resonance (EPR), thermal gravimetric, elemental analysis, and quantum chemical calculations. The results show that the diaxial coordination of bidentate organic ligands (L-tyrazine and diaminohydroquinone) leads to the quenching of the tetrapyrrole chromophore fluorescence, while the chelation of the porphyrinate diaxial complexes with Cu2+ is accompanied by an increase in the fluorescence in the organo-inorganic hybrid polymers formed. The obtained results are of particular interest to those involved in creating new ‘chemo-responsive’ (i.e., selectively interacting with other chemical species as receptors, sensors, or photocatalysts) materials, the optoelectronic properties of which can be controlled by varying the number and connection type of monomeric fragments in the polyporphyrin arrays.

‘After-effect’ in Aqueous Solutions of Deoxyribonucleic Acid irradiated with X-Rays

Nature ◽  
1953 ◽  
Vol 171 (4365) ◽  
pp. 1153-1154 ◽  
Author(s):  
MALCOLM DANIELS ◽  
GEORGE SCHOLES ◽  
JOSEPH WEISS
Keyword(s):  
Aqueous Solutions ◽  
Deoxyribonucleic Acid ◽  
X Rays ◽  
After Effect

The Effects of X-rays, Cathode, and Ultra-violet Rays on Yeast

Radiology ◽  
1931 ◽  
Vol 17 (6) ◽  
pp. 1171-1175 ◽  
Author(s):  
Ralph W. G. Wyckoff ◽  
Basile J. Luyet
Keyword(s):  
Ultra Violet ◽  
X Rays

Inhibition of nucleic acid synthesis caused by X-irradiation of the nucleolus

1960 ◽  
Vol 152 (948) ◽  
pp. 387-396 ◽  
Keyword(s):  
Nucleic Acid ◽  
Ultra Violet ◽  
Acid Synthesis ◽  
Nucleic Acid Synthesis ◽  
Effective Diameter ◽  
X Rays ◽  
Narrow Beam ◽  
Equal Dose ◽  
X Irradiation

Living cells grown in tissue culture have been irradiated with a narrow beam of soft X-rays of effective diameter 2·5 μ. The method has been used in conjunction with quantitative ultra-violet photomicrography to investigate the role of the nucleolus in nucleic acid synthesis. The results show that X-irradiation of the nucleolus reduces the amount of nucleic acid synthesized in the nucleus when measured 3 to 7 h after irradiation, whereas X-irradiation of the nuclear sap with an equal dose does not show this effect. The significance of this is discussed.

Sign in / Sign up

Export Citation Format

Share Document