Effects of X-Irradiation on the Various Enzymic Functions of NADP+-Linked Isocitrate Dehydrogenase

1971 ◽  
Vol 49 (5) ◽  
pp. 510-515 ◽  
Author(s):  
Peggy Holland ◽  
Clive Little
Keyword(s):  
Aqueous Solution ◽  
Isocitrate Dehydrogenase ◽  
Catalytic Properties ◽  
Sulfhydryl Groups ◽  
X Ray ◽  
Dilute Aqueous Solution ◽  
X Irradiation ◽  
G Value ◽  
Catalytic Functions ◽  
Allosteric Properties

Highly purified NADP+-linked isocitrate dehydrogenase was X-irradiated in dilute aqueous solution and proved to be very radiosensitive, being inactivated with a G value of 0.5. The catalytic functions of the enzyme were destroyed at the same rate. However, unlike most allosteric enzymes, the allosteric properties were not more radiosensitive than the catalytic properties. X-ray inactivation was associated with the destruction of seven to eight sulfhydryl groups. The first four sulfhydryls destroyed were extremely radiosensitive, having G values for destruction of almost 2. Comparison with several reagents known to attack sulfhydryl groups suggested that sulfhydryl destruction was sufficient to account for the X-ray response of the enzyme. Destruction of the single essential methionine did not seem significant in the inactivation. X-ray inactivation was also associated with increases in the Km values for isocitrate and manganese.

A Small-Angle X-Ray Scattering Study on Pre-Irradiated Malate Synthase. The Influence of Formate, Superoxide Dismutase, and Catalase on the X-Ray Induced Aggregation of the Enzyme

1985 ◽  
Vol 40 (5-6) ◽  
pp. 364-372 ◽  
Author(s):  
P. Zipper ◽  
R. Wilfing ◽  
M. Kriechbaum ◽  
H. Durchschlag
Keyword(s):  
Aqueous Solution ◽  
Superoxide Dismutase ◽  
Small Angle ◽  
Malate Synthase ◽  
X Ray ◽  
X Ray Scattering ◽  
X Irradiation ◽  
The Mean ◽  
Induced Aggregation ◽  
Ray Scattering

Abstract The sulfhydryl enzyme malate synthase from baker’s yeast was X-irradiated with 6 kGy in air-saturated aqueous solution (enzyme concentration: ≃ 10 mg/ml; volume: 120 μl), in the absence or presence of the specific scavengers formate, superoxide dismutase, and catalase. After X-irradiation, a small aliquot of the irradiated solutions was tested for enzymic activity while the main portion was investigated by means of small-angle X-ray scattering. Additionally, an unir­radiated sample without additives was investigated as a reference. Experiments yielded the fol­lowing results: 1. X-irradiation in the absence of the mentioned scavengers caused considerable aggregation, fragmentation, and inactivation of the enzyme. The dose Dt37 for total (= repairable + non­-repayable) inactivation resulted as 4.4 kGy. The mean radius of gyration was found to be about 13 nm. The mean degree of aggregation was obtained as 5.7, without correction for fragmenta­tion. An estimation based on the thickness factor revealed that about 19% of material might be strongly fragmented. When this amount of fragments was accordingly taken into account, a value of 7.1 was obtained as an upper limit for the mean degree of aggregation. The observed retention of the thickness factor and the finding of two different cross-section factors are in full accord with the two-dimensional aggregation model established previously (Zipper and Durchschlag, Radiat. Environ. Biophys. 18, 99 - 121 (1980)). 2. The presence of catalytic amounts of superoxide dismutase and/or catalase, in the absence of formate, during X-irradiation reduced both aggregation and inactivation significantly. 3. The presence of formate (10 or 100 mᴍ) during X-irradiation led to a strong decrease of aggregation and inactivation. This effect was more pronounced with the higher formate concen­tration or when superoxide dismutase and/or catalase were simultaneously present during X-irradiation. The presence of formate also reduced the amount of fragments significantly. 4. The results clearly show that the aggregation and inactivation of malate synthase upon X-irradiation in aqueous solution are mainly caused by OH·; to a minor extent O·̄2 and H2O2 are additionally involved in the damaging processes.

X-IRRADIATION OF RIBOSE AND DEOXYRIBOSE DERIVATIVES

1962 ◽  
Vol 40 (1) ◽  
pp. 1553-1565
Author(s):  
D. K. Myers
Keyword(s):  
Aqueous Solution ◽  
Nucleic Acids ◽  
The Other ◽  
Free Sugar ◽  
Blood Samples ◽  
Other Hand ◽  
Dilute Aqueous Solution ◽  
X Irradiation ◽  
In Cells

During X-irradiation of ribosides and deoxyribosides in dilute aqueous solution, purine and sugar moieties were destroyed at approximately the same rate. Pyrimidine moieties, on the other hand, were destroyed more rapidly, resulting in a fairly rapid liberation of free sugar during irradiation of pyrimidine ribosides or deoxyribosides. No marked differences in the rates of destruction of ribose and deoxyribose derivatives were observed in these experiments.Similar reactions were observed during irradiation of blood samples. However, acid-soluble ribonucleotides in the blood proved to be much more sensitive than the nucleic acids or proteins to destruction by X-radiation. The significance of these findings is discussed with relation to the damage produced in cells by X-irradiation.

X-IRRADIATION OF RIBOSE AND DEOXYRIBOSE DERIVATIVES

1962 ◽  
Vol 40 (11) ◽  
pp. 1553-1565 ◽  
Author(s):  
D. K. Myers
Keyword(s):  
Aqueous Solution ◽  
Nucleic Acids ◽  
The Other ◽  
Free Sugar ◽  
Blood Samples ◽  
Other Hand ◽  
Dilute Aqueous Solution ◽  
X Irradiation ◽  
In Cells

During X-irradiation of ribosides and deoxyribosides in dilute aqueous solution, purine and sugar moieties were destroyed at approximately the same rate. Pyrimidine moieties, on the other hand, were destroyed more rapidly, resulting in a fairly rapid liberation of free sugar during irradiation of pyrimidine ribosides or deoxyribosides. No marked differences in the rates of destruction of ribose and deoxyribose derivatives were observed in these experiments.Similar reactions were observed during irradiation of blood samples. However, acid-soluble ribonucleotides in the blood proved to be much more sensitive than the nucleic acids or proteins to destruction by X-radiation. The significance of these findings is discussed with relation to the damage produced in cells by X-irradiation.

Sulfhydril Groups and the Concerted Inhibition of NADP+-Linked Isocitrate Dehydrogenase

1972 ◽  
Vol 50 (10) ◽  
pp. 1109-1113 ◽  
Author(s):  
Clive Little ◽  
Peggy Holland
Keyword(s):  
Binding Site ◽  
Dehydrogenase Activity ◽  
Isocitrate Dehydrogenase ◽  
Lipid Peroxide ◽  
Cysteine Residue ◽  
Sulfhydryl Groups ◽  
Sulfhydryl Reagents ◽  
Carboxylase Activity ◽  
X Irradiation

Mixtures of glyoxalate and oxaloacetate have been shown to inhibit highly purified pig heart NADP+ -linked isocitrate dehydrogenase in a strongly concerted manner. The α-ketoglutarate reductive carboxylase activity of the enzyme was also inhibited, but to a lesser extent than the dehydrogenase activity. Modification of sulfhydryl groups in the enzyme by certain reagents led to a diminution of the inhibition, although the extent of this effect depended on the reagent used. N-Ethylmaleimide was most effective at diminishing the concerted inhibition, whereas oxidation of the sulfhydryl groups by X-irradiation or lipid peroxide had no effect. It was concluded that the effect of sulfhydryl reagents on the inhibition was probably due to the modification of one specific cysteine residue which is possibly adjacent to the binding site on the enzyme for glyoxalate.

Efficient capturing of hydrogen peroxide in dilute aqueous solution by co-crystallisation with amino acids

CrystEngComm ◽  
2021 ◽  
Author(s):  
Ryota Yamaguchi ◽  
Rika Tanaka ◽  
Mayu Maetani ◽  
Hiroyasu Tabe ◽  
Yusuke Yamada
Keyword(s):  
Aqueous Solution ◽  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Single Crystal ◽  
X Ray ◽  
Dilute Aqueous Solution

Hydrogen peroxide (H2O2) in dilute aqueous solution can be efficiently captured by co-crystallisation with enantiomeric and racemic amino acids as evidenced by colourimetric titration and the single crystal X-ray structural...

Eds Of Radioactive Particles By Self-Induced Fluorescence

1990 ◽  
Vol 48 (2) ◽  
pp. 238-239
Author(s):  
Gregory L. Finch ◽  
Richard G. Cuddihy
Keyword(s):  
Electron Beam Irradiation ◽  
Nuclear Reactor ◽  
X Rays ◽  
Reactor Accident ◽  
Internal Radiation ◽  
X Ray ◽  
External Sources ◽  
X Irradiation ◽  
Available Information ◽  
Individual Particles

The elemental composition of individual particles is commonly measured by using energydispersive spectroscopic microanalysis (EDS) of samples excited with electron beam irradiation. Similarly, several investigators have characterized particles by using external monochromatic X-irradiation rather than electrons. However, there is little available information describing measurements of particulate characteristic X rays produced not from external sources of radiation, but rather from internal radiation contained within the particle itself. Here, we describe the low-energy (< 20 KeV) characteristic X-ray spectra produced by internal radiation self-excitation of two general types of particulate samples; individual radioactive particles produced during the Chernobyl nuclear reactor accident and radioactive fused aluminosilicate particles (FAP). In addition, we compare these spectra with those generated by conventional EDS.Approximately thirty radioactive particle samples from the Chernobyl accident were on a sample of wood that was near the reactor when the accident occurred. Individual particles still on the wood were microdissected from the bulk matrix after bulk autoradiography.

Structural Study of a new Compound Based on Acid 1,4-Cyclohexanedicarboxylic (1,4-CDC)

2010 ◽  
Vol 6 (1) ◽  
pp. 891-896
Author(s):  
Manel Halouani ◽  
M. Dammak ◽  
N. Audebrand ◽  
L. Ktari
Keyword(s):  
Aqueous Solution ◽  
Water Molecules ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Compound I ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
X Ray ◽  
Cell Parameters ◽  
Cyclohexanedicarboxylic Acid

One nickel 1,4-cyclohexanedicarboxylate coordination polymers, Ni2 [(O10C6H4)(COO)2].2H2O  (I), was hydrothermally synthesized from an aqueous solution of Ni (NO3)2.6H2O, (1,4-CDC) (1,4-CDC = 1,4-cyclohexanedicarboxylic acid) and tetramethylammonium nitrate. Compound (I) crystallizes in the monoclinic system with the C2/m space group. The unit cell parameters are a = 20.1160 (16) Å, b = 9.9387 (10) Å, c = 6.3672 (6) Å, β = 97.007 (3) (°), V= 1263.5 (2) (Å3) and Dx= 1.751g/cm3. The refinement converged into R= 0.036 and RW = 0.092. The structure, determined by single crystal X-ray diffraction, consists of two nickel atoms Ni (1) and Ni (2). Lots of ways of which is surrounded by six oxygen atoms, a carboxyl group and two water molecules.

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