7-Ray irradiation

The application of flavonoids for the treatment of various diseases associated with free radical overproduction is considered in Chapter 29. However, it seems useful to discuss here some studies describing the activity of flavonoids under certain pathophysiological conditions. Oral pretreatment with rutin of rats, in which gastric lesions were induced by the administration of 100% ethanol, resulted in the reduction of the area of gastric lesions [157]. Rutin was found to be an effective inhibitor of TBAR products in the gastric mucosa induced by 50%i ethanol [158]. Rutin and quercetin were active in the reduction of azoxymethanol-induced colonic neoplasma and focal area of dysplasia in the mice [159], Chemopreventive effects of quercetin and rutin were also shown in normal and azoxymethane-treated mouse colon [160]. Flavonoids exhibited radioprotective effect on 7-ray irradiated mice [161], which was correlated with their antioxidative activity. Dietary flavones and flavonols protected against the toxicity of the environmental contaminant dioxin [162], Rutin inhibited ovariectomy-induced osteopenia in rats [163],... 

Certain chiral organic compounds create crystalline environments and act as enantio-controlling media (7) even though they do not function as true catalysts. Natta s asymmetric reaction of prochiral trans-1,3-pentadiene, which was included in the crystal lattice of chiral perhydro-triphenylene as a host compound, to form an optically active, isotactic polymer on 7-ray irradiation, is a classic example of such a chiral molecular lattice (Scheme 1) (2). Weak van der Waals forces cause a geometric arrangement of the diene monomer that favors one of the possible enantiomeric sequences. 

Piantanida and Piazzi (Refs 100 115) conducted expts on expls and proplnts which had been subjected to 7-ray irradiation. Proplnts containing 0—7% diethylphenyiurea and 0—5%... 

Since oxygen is not consumed in the over-all reaction, it does not affect G Fe3+). This dosimeter shows no dose rate effect under the usual conditions of 7-ray irradiation since all of the above reactions except Reaction 6 are fast, and this reaction has a half-life of 14 seconds in 0.001M ferrous sulfate (1). 

This paper reports the effect of both electron beam and 7-ray irradiation on the amino acids of ground beef at dose levels varying from 2-50 megarads. For electron beam irradiation, two energy levels and two power levels were used to give varying dose rates for each total dose. 

Table V. Effect of Electron Beam and 7-Ray Irradiation on Cystine...

The data of Table IV seem to indicate slightly less damage to amino acids with 7-irradiation than with 24 m.e.v. electrons. The marked stability of these amino acids in beef to 7-irradiation has also recently been observed by Rhodes and Southern (39) and is somewhat in contrast to the earlier report of Tsien and Johnson (50). The rather extensive losses of glutamate reported in the earlier work may have been caused by incomplete recoveries from the analytical columns or by differences in irradiation procedure. Our samples were irradiated from a cobalt-60 source, while the earlier samples were irradiated from spent fuel rods. It has recently been reported (15) that 7-ray irradiation of glutamic acid yields the corresponding a-keto acid, the amount obtained depending on irradiation conditions. 

Our data also indicate greater stability of the amino acids in beef than was observed in the case of 7-ray irradiation of insulin. In the latter case, Drake et al. (8) found that in addition to cystine, tyrosine, phenylalanine, proline, and histidine were quite radio sensitive. Instability of tyrosine in proteins on 7-ray irradiation has also been reported by Hatano (16), who states that in protein, tyrosine is the most sensitive amino acid. Kolo-miichenko and Morozova (24) found about 20% destruction of tryptophan, tyrosine, and histidine following 1.5 Mrads 7-ray irradiation of egg albumin. 

Electron beam and 7-ray irradiation of ground beef have been compared with regard to amino acid destruction. The most sensitive acid to irradiation was cystine, followed by tryptophan and histidine. The greatest amounts of destruction were obtained with 24 m.e.v., 200 juamps electron beam irradiation. Electron beam density appeared to be as important as total irradiation dose in destroying amino acids. In general, little damage to amino acids and thus to the nutritive value of beef was produced by irradiation. 

Rates of radiation induced polymerizations are normally determined by dilatometric [85] or gravimetric [84] experiments. Some of the first quantitative results from cyclopentadiene [86] and a-methylstyrene [87] were obtained by competitive kinetic methods, based on the retarding effect of ammonia and amines. This approach tends to yield maximum values for Rp. More recently, however, a procedure combining stationary state kinetic and conductance measurements has been described [88, 89], and further refined [85]. Because the ions generated by 7-ray irradiation have a transient existence, the kinetic treatment leads to expressions which are very similar to those derived for homogeneous free radical polymerizations [90]. A simplified version of the kinetic scheme is as follows ... 

As with isobutyl vinyl ether the result from 7-ray irradiation must represent the reactivity of naked free ions and this fep is at least 10 ... 

More hydrogen atoms than hydroxyl radicals are formed in 7-ray irradiated acid solutions. In 0.8 N sulfuric acid, G(H) is 3.65 and G(OH) is 2.95. As the pH increases above 3, the difference in G(H) — G(OH) decreases. Recent determinations of radical and molecular yields are in reasonable agreement with these values. - ... 

Poluektov and Mekhrynshev [166] have also studied the liquid phase oxidation of trichloroethylene, but initiated by 7-ray irradiation from a cobalt-60 source. It is questionable whether they avoided complications from thermal initiation and they did not pay particular attention to purity (as was found necessary by Mayo and Honda [165]), but the oxidations do show similar kinetic features. The rate of oxidation was found to be proportional to the first power of the concentration of the substrate, to the square root of the rate of initial active centre formation, and to the oxygen concentration only at low oxygen pressures. At high pressures, the rate was zero order with respect to oxygen. The overall activation energy was found to be 7.5 kcal mole-1. 

UV—Ultraviolet irradiation X—X-ray irradiation 7—7-ray irradiation A—annealing D—doping RT—room temperature. For example UV77KA195K means Ultraviolet irradiation at 77°K followed by annealing at 195°K. 

Thermoluminescence measurements were also made on X-ray and 7-ray irradiated KN3 from 47 to 255°K, yielding activation energies and pre-exponential factors [74,75]. Because the heating rates are different from those used for the UV-irradiated KN3, it is difficult to relate the two sets of data. Since thermoluminescence is sensitive to impurity content, there are also problems in relating studies on crystals grown in different laboratories. However, Townsend et al. [74,75] determined pre-exponential factors which have also been obtained from kinetic studies of the decay of ESR and optical spectra, enabling a comparison with determinations from annealing studies of ESR and optical bonds. In X-ray... 

A novel example of an asymmetric synthesis in which a prochiral diene monomer is included in the crystal lattice of a chiral host compound which can form an optically active polymer on 7-ray irradiation was reported by Farina et al [208]. By irradiation of trans-1,3-pentadiene (LXXIX) included in ( XT )- or (+)(,S )-perhydrotriphenylene (LXXIX) of trans-anti-trans-anti configuration in the solid state, isotactic OA polymers, of opposite sign, were obtained the rotatory powers are weak but unambiguous. 

After that 1,3 pentadiene (XXXIII) was trapped into / -(-)-perhydrotriphenylene (M 93°) (XXXIV) and made it form an inclusion compound, polymerization was carried out under 7-ray irradiation. As a result, trans 1,4-isotactic polypentadiene (XXXV) showing [a] D = 2.5° 0.3° (in chloroform) was yielded. 

Inclusion polymerization of various monomers in PHTP is similar to urea and thiourea The polymerization was initiated by 7-ray irradiation which gave highly regulated polymers for example, the polymerization of 1,3-tra/i.s-pentadiene gave the l,4-/ran5-isotactic polymer [66]. 

---