Effects of Alkali Halides and Other Inorganic Salts on Radiation Inactivation of Taka-amylase in Aqueous System

Effects of alkali halides on radiation inactivation of Taka-amylase A were investigated in connection with their synergistic action to the radiation inactivation of microorganisms. Effective concentrations of these halides in protection against irradiation inactivation of this enzyme were well corresponded to that observed in the synergistic action to microorganisms. Removal of dissolved oxygen from halide solutions decreased their protective effect. Irradiated alkali halide solutions of relatively higher concentrations exhibited the inactivating action to this enzyme, and various types of addition effects of halogens and halogenoxyacids were observed with or without irradiation. Sodium nitrite showed effective protection even with higher radiation doses, and the heavy metal cations, Cu⁺⁺ and Fe⁺⁺⁺, also gave a protective action in low concentrations. From these observations, the possible interpretation on the mode of protection of alkali halides was attempted.     

Modification of Combined Effect of Radiation and Sodium Chloride on Microorganisms by Chemical Agents during Irradiation

Effects of various chemical agents on the synergistic action of NaCl to the radiation inactivation of bacteria and yeast were studied. The remarkable modification of the radiation lethal effect by some reagents is considered to be a strong evidence for an indirect nature of NaCl synergistic action during irradiation. Most of these modification effects were restricted to the actions during irradiation, supporting the free radical hypothesis in which the short-life active species formed by radiation were considered to attack bacterial cells. Furthermore, pre-irradiation effects under various conditions suggest that the enhancement of radiation lethal effect by NaCl may involve the intracellular events.     

The After Effect of Irradiated Halogenophenol Solutions on the Viability of Escherichia coli

Gamma irradiation has been found to induce a remarkable bactericidal activity in an aqueous soltion of p-bromophenol even at the non-toxic lower concentrations, but not in a crystalline form or under a frozen state. Effects of concentration of reagents, temperature, pH, radiation dose, oxygen and some additives during irradiation on the radiation induction of bactericidal activity in the p-bromophenol solution were investigated. The results suggest that the induced activity is attributable to some long-life products, formed as a result of radiolysis of p-bromophenol and in coupling with radiolysis of water. The processes of formation and destruction of such bactericidal factor(s) were considerably influenced by several conditions during irradiation. Based on the experimental results, relationship between radiolysis process and induction of bactericidal activity was discussed.     

Ectomycorrhizal fungi: A new source of atmospheric methyl halides?

Incomplete source budgets for methyl halides – compounds that release inorganic chlorine and bromine radicals which, in turn, catalyze atmospheric ozone depletion – limit our ability to predict the fate of the stratospheric ozone layer. We report here the first measured emissions of methyl chloride, methyl bromide, and methyl iodide from ectomycorrhizal fungi. We grew nine fungal isolates on growth media containing halide concentrations similar to those found in soils and plant tissues. The observed range of emissions was 0.003–65 μg methyl chloride, 0.001–3 μg methyl bromide, and 0.02–12 μg methyl iodide g^?1 dry weight fungi day^?1. Species varied in production rates of methyl chloride vs. methyl bromide vs. methyl iodide. Cenococcum geophilum, a widespread ectomycorrhizal fungus, was further tested to investigate the effects of halide substrate concentration in growth media. Emissions from this species increased linearly with increasing concentrations of both bromide and iodide. In addition, a subset of four fungi was studied with two media concentrations each of chloride, bromide, and iodide (0.2 or 20 mm ). These fungi had similar responses to halide concentration, despite 1000‐fold differences in baseline emission rates between isolates. Finally, high chloride concentrations (20 mm ) in media did not appear to inhibit emissions of methyl bromide or methyl iodide. Overall, ectomycorrhizal fungi might be an important source of methyl halides to the atmosphere, and substrate concentrations and community composition may influence production levels in ecosystems.     

Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation

The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology.     

Salt effects on the conformational stability of the visual G-protein-coupled receptor rhodopsin

Membrane protein stability is a key parameter with important physiological and practical implications. Inorganic salts affect protein stability, but the mechanisms of their interactions with membrane proteins are not completely understood. We have undertaken the study of a prototypical G-protein-coupled receptor, the α-helical membrane protein rhodopsin from vertebrate retina, and explored the effects of inorganic salts on the thermal decay properties of both its inactive and photoactivated states. Under high salt concentrations, rhodopsin significantly increased its activation enthalpy change for thermal bleaching, whereas acid denaturation affected the formation of a denatured loose-bundle state for both the active and inactive conformations. This behavior seems to correlate with changes in protonated Schiff-base hydrolysis. However, chromophore regeneration with the 11-cis-retinal chromophore and MetarhodopsinII decay kinetics were slower only in the presence of sodium chloride, suggesting that in this case, the underlying phenomenon may be linked to the activation of rhodopsin and the retinal release processes. Furthermore, the melting temperature, determined by means of circular dichroism and differential scanning calorimetry measurements, was increased in the presence of high salt concentrations. The observed effects on rhodopsin could indicate that salts favor electrostatic interactions in the retinal binding pocket and indirectly favor hydrophobic interactions at the membrane protein receptor core. These effects can be exploited in applications where the stability of membrane proteins in solution is highly desirable.     

Effect of deicing chloride salts on ion accumulation in spruce (Picea abies (L.) sp.)

Among the inorganic chloride salts, NaCl, CaCl₂ and in a minor proportion KCl and MgCl₂ are used as deicing agents. Mixturs of these salts were merely applied with respect to their physico-chemical properties, but their effect on roadside vegetation has never been studied so far. From a screening of different salt mixtures on ion accumulation in needles and twigs of spruce tress (Picea abies sp.) it was shown that the presence of a small amount of calcium in the salt treatments had some beneficial effects on ion regulation. In the presence of calcium, sodium accumulation could be reduced. But more straightforward was its effect on the selectivity between sodium and potasium in favour of the latter. Chloride concentrations did not alter very much; their role in the presence of monovalent cations is nevertheless obvious and is discussed. The study also confirms the presence of potassium retranslocation in conifer trees. The ion characteristics are briefly discussed with respect to the ecological effects of chloride salts on tress.     

CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites

The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI₃. In this work, inorganic perovskite composition CsPbI₃ is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI₂–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.     

Benzyloxy Derivatives of Triazine-based Coupling Reagents Designed for an Efficient Solid Phase Peptide Synthesis on Polystyrene Resin

Coupling reagents resembling the structure of Merrifield resin were designed and prepared from 2-chloro-4,6-dibenzyloxy-1,3,5-triazine and the different tertiary bases N-methylmorpholine, N-methylpiperidine, and DABCO. As previously observed for DMTMM, the appropriate N-(4,6-dibenzyloxy-1,3,5-triazin-2-yl) ammonium chloride salts were not suitable as efficient coupling reagents because of their low stability. On the other hand, the stability of the N-(4,6-dibenzyloxy-1,3,5-triazin-2-yl) ammonium tetrafluoroborates was suitable enough for prolonged storage and convenient application in SPPS. Moreover, we observed that the superactive intermediates formed during activation of Fmoc–Aib–OH with 4,6-dibenzyloxy-1,3,5-triazine-based coupling reagents lead to an increase in its concentration inside the polystyrene resin. Therefore, we hypothesize that this increase can enhance efficiency of 4,6-dibenzyloxy-1,3,5-triazine-based coupling reagents in SPPS.     

The radiation response of cultured mammalian V79-S171 cells exposed to a wide concentration range of sulphate salt solutions.

The radiation response of Chinese hamster cells (V79) exposed to a wide concentration range of Li2SO4, Na2SO4 or K2SO4 has been examined and compared with the radiation response of cells treated in an identical manner with LiCl, NaCl, or KCl solutions. At hypotonic salt concentrations, cells were radiosensitized by both the chloride and sulphate salts. At high salt concentrations, approximately greater than 0.9 M, a radioprotective effect was observed with both chloride and sulphate salts. At intermediate salt concentrations from about 0.2 to 0.9 M, the cells that were treated with the sulphate salt solutions were radioprotected; cells treated with chloride salt solutions were radiosensitized. The difference in radiation response was attributed to the difference in anions for the two types of salts used.     

The role of high ionic concentrations in protection against X-irradiation

Various levels of protection against x-irradiation damage in bacteriophage T1 may be obtained by the addition of inorganic salts to the aqueous virus suspensions during irradiation. The highest survival values are obtained with the nitrite salts, and their protective power is attributed primarily to their function as reducing agents. The nitrate ion shows greater protection than the corresponding sulfate or chloride ions. This may be due in part to the lower energy level of the nitrate ion, by reason of resonance. Since greater expenditure of incident energy is required to raise the ion from the ground state, the energy thus dissipated may be ineffective in the inactivation of virus particles. The ammonium salts exhibit protection of a different order of magnitude from that of the metallic salts. It is postulated that NH₄⁺ protects in a threefold way: (a) dehydration, (b) reduction, in which the ammonia is oxidized to nitrite and the nitrite to nitrate, and (c) stabilization of the virus protein. Metallic salts likewise protect, but a point of maximum protection is reached in lower concentrations than in the case of the ammonium salts. After this maximum protection is reached, there is a rapid decline in survival with increased concentration. This prevents protection of the order of magnitude that can be obtained with the ammonium salts. It is postulated that a specific cationic interaction with the phage may be responsible for the decreased protection. Bacteriophage is protected during x-irradiation by an alkaline pH, in the case of NH₄OH. This protection could not be produced with NaOH, presumably because of the greater hydrolysis of the protein components of the virus particle in solutions of NaOH, whereas NH₄OH stabilizes the protein.     

Synergistic Actions of Halogenophenols on Radiation Inactivation of Microorganisms

The combined effects of radiations and halogenophenols were investigated. The activities of these reagents to increase the radiolethality during irradiation were demonstrated with E. coli and Z. soya. Some relationships between chemical structure and activity were revealed as follows at pH 6 and 8: (1) effectiveness of substituted halogen was in the order of I>Br>Cl; (2) effectiveness of the monosubstituting position on a benzene ring of halogenophenols was increased in the order of p->m->o-; (3) effectiveness increased with increasing the number of halogen atom. The halogenophenol action was also found to be considerably pH-dependent. In the case of chlorinated derivatives, the synergistic activity to increase the radiolethality was intensified on the acidic side, though bromides and iodides were more effective on the basic side.     

Effects of ultraviolet radiation on the membranes ofChara corallina

Summary The effects of 253.7 nm ultraviolet (UV) radiation on the membrane properties ofChara corallina have been studied. UV irradiation caused depolarization of the membrane potential (p.d.) and a decrease in membrane resistance. These effects were largely reversible with steady values being obtained within 40 minutes after the UV was turned off. The effects on ionic fluxes of Na⁺, K⁺ and Cl^– have also been studied using radioactive tracer techniques. The influxes were unchanged by irradiation. The chloride efflux was increased sevenfold during the irradiation period but recovered to the pre-irradiation value within 30 minutes after the irradiation period. The potassium efflux was also increased and reached a maximum 10 minutes after irradiation. The resting potential and the average depolarized p.d. reached during irradiation were in good agreement with those calculated from permeability coefficients indicated by the observed passive fluxes, using the Goldman equation for p.d. However, the plasmalemma resistance and its change due to irradiation did not match the values calculated from the same permeability coefficients used to estimate p.d. This disagreement, and an apparent imbalance in the charge transferred across the resting or irradiated plasmalemma, suggest the participation of another ion species as well as K⁺, Na⁺ and Cl^–.     

Metabolite specific effects of solar UV-A and UV-B on alder and birch leaf phenolics

We measured the concentrations of ultraviolet (UV)‐absorbing phenolics varying in response to exclusion of either solar UV‐B or both solar UV‐A and UV‐B radiations in leaves of grey alder (Alnus incana) and white birch (Betula pubescens) trees under field conditions. In alder leaves 20 and in birch leaves 13 different phenolic metabolites were identified. The response to UV exclusion varied between and within groups of phenolics in both tree species. The changes in concentration for some metabolites suggest effects of only UV‐A or UV‐B, which band being effective depending on the metabolite. For some other metabolites, the results indicate that UV‐A and UV‐B affect concentrations in the same direction, while for a few compounds there was evidence suggesting opposite effects of UV‐A and UV‐B radiation. Finally, the concentration of some phenolics did not significantly respond to solar UV. We observed only minor effects on the summed concentration of all determined phenolic metabolites in alder and birch leaves, thus indicating that measuring only total phenolics concentration may not reveal the effects of radiation. Here, we show that the appropriate biological spectral weighting functions for plant‐protective responses against solar UV radiation extend in most cases – but not always – into the UV‐A region and more importantly that accumulation of different phenolic metabolites follows different action spectra. This demonstrates under field conditions that some of the implicit assumptions of earlier research simulating ozone depletion and studying the effects of UV radiation on plant secondary metabolites need to be reassessed.     

Factors Affecting Autocatalysis of Botulinum A Neurotoxin Light Chain*

The light chain of botulinum neurotoxin serotype A undergoes autocatalytic fragmentation into two major peptides during purification and storage (Ahmed S. A. et al. 2001, J. Protein Chem. 20:221–231) by both intermolecular and intramolecular mechanisms (Ahmed S. A. etal. 2003, Biochemistry 42:12539–12549). In this study, we investigated the effects of buffers and salts on this autocatalytic reaction in the presence and absence of zinc chloride. In the presence of zinc chloride, the fragmentation reaction was enhanced in each of acetate, MES, HEPES and phosphate buffers with maximum occurring in acetate when compared to those in the absence of zinc chloride. Adding sodium chloride in phosphate buffer in the presence of zinc chloride increased the extent of proteolysis. Irrespective of the presence of zinc chloride, adding sodium chloride or potassium chloride in phosphate buffer elicited an additional proteolytic reaction. Higher concentrations of sodium phosphate buffer enhanced the autocatalytic reaction in the absence of zinc chloride. In contrast, in the presence of zinc chloride, higher concentrations of sodium phosphate decreased the autocatalytic reaction. Optimum pH of autocatalysis was not affected significantly by the absence or presence of zinc chloride. Like zinc chloride, other chlorides of divalent metals, such as magnesium, cobalt, iron and calcium also enhanced the autocatalytic reaction. Polyols such as ethylene glycol protected the light chain from fragmentation. Exposure of light chain to UV radiation led to enhanced fragmentation. In order to avoid fragmentation, the protein should be stored frozen in a low concentration buffer of neutral or higher pH devoid of any metal. Our results provide a choice of buffers and salts for isolation, purification and storage of intact botulinum neurotoxin serotype A light chain.     

The effect of radiation therapy combined with natural killer cells against spontaneous murine fibrosarcoma

The effect of radiation therapy combined with lymphoid cells against spontaneous murine fibrosarcoma (FSa-II) was investigated bothin vivo andin vitro. In thein vivo experiment, syngeneic C3H mice were divided into 3 groups. Animals in the first group were injected with 1 x 10⁵ tumor cells into the right hind leg. Animals in the second and third groups were injected with 1 x 10⁵ tumor cells mixed with 1 x 10⁷ normal lymphoid cells (NLC) or effector lymphoid cells (ELC), respectively. ELC were obtained from spleen and lymph nodes of FSa-II-bearing mice and incubatedin vitro for 40 hr to eliminate suppressor T cell function. NLC were obtained from normal mice and incubated in the same way. Irradiation was given using¹³⁷Cs unit 3 days after cell inoculation. 12 out of 14 mice (85.7%) inoculated with tumor cells mixed with NLC did not show any tumor growth at 60 Gy local irradiation. 12 out of 21 mice (57.1 %) inoculated with tumor cells alone and 6 out of 10 (60%) with tumor cells mixed with ELC rejected tumors at the same radiation dose. This synergistic effect with NLC was not observed when NLC was inoculated after irradiation, indicating that lymphoid cells should be in contact with tumor cells before irradiation. In the⁵¹Cr release assay, lymphoid cells obtained from whole body irradiated (WBI) mice showed 17.8% lysis without irradiation and 28.8% lysis at 5 Gy irradiation. Untreated NLC showed almost no cytotoxic effect at the same radiation dose. This synergistic effect disappeared when WBI lymphoid cells were treated with anti asialo GM1 and complement. These results suggested that NK cells might be important in this synergistic effect with irradiation. To obtain a sufficient level of synergistic effect by in vitro combined treatment of mixed tumor cell - NLC culture and irradiation - incubation for more than 12 hrs and 8 hrs appeared to be necessary before and after irradiation, respectively.     

Effects of Chemical Agents on Radiation Inactivation of Streptomyces Protease in Aqueous System

Inactivation of crystalline enzyme, Streptomyces protease G, by γ-ray irradiation in an aqueous system has been investigated. It is indicated that inactivation of the enzyme is attributable mainly to the indirect action of radiation. The inactivation curve is exponential and the G-value for enzyme inactivation is calculated as 0.1 at an enzyme concentration of 1×10^?5m, which is not influenced by varying pH. Effects of various other solutes on radiation inactivation have been also studied. Halogen ions, especially iodine ion, and nitrite ion are most protective among various inorganic anions examined, and alkali metal and alkali earth metal cations are ineffective. Among various organic compounds examined, sulfur-containg compounds and unsaturated compounds are generally effective for protection of enzyme activity against radiation damages. The protective effect of benzene is enhanced by the substitution of electron donating groups. Chloroform and chloral are found to act as a synergist for irradiation inactivation.     

Chromosomal aberrations in bone-marrow cells of mice given a normal or a calcium-deficient diet supplemented with various heavy metals

Mice kept on a normal (1.1% calcium) or low-calcium (0.03%) diet were exposed for one month to zinc chloride (0.5% Zn), lead acetate (0.5% Pb) or cadmium chloride (0.06% Cd) or to a mixture of these salts at half the above concentrations. These concentrations, given in a poor calcium diet, represent an LD 50/30 days. After the mice were killed bone-marrow cells were assayed for chromosomal aberrations, and serum calcium was determined. Chromosomal aberrations were detected in the mice maintained on a low-calcium diet and exposed to lead, zinc or a mixture of lead, zinc and cadmium. The possible mechanism for the synergistic action on genetic effects of the lack of calcium and intoxication by heavy metals are discussed, and it is recommended that routine attention be given to the state of calcium metabolism in heavy-metal intoxication.     

Effect of various salts on the growth and development of Geotrichum candidum,the causal agent of carrot sour rot

This study evaluated the efficacy of ammonium, calcium, potassium and sodium salts as possible alternatives to synthetic fungicides in the control of Geotrichum candidum, the causal agent of sour rot on carrots. In vitro mycelial growth of G. candidum was completely halted by ammonium bicarbonate and carbonate; calcium oxide; potassium benzoate, carbonate and sorbate; sodium benzoate, carbonate and fluoride (2% w/v). Potassium and sodium bicarbonate also reduced mycelial growth by 77.78% and 90.60%, respectively, and the difference between the effects of sodium bicarbonate and the first group of salts was not statistically significant (p < 0.05). With the exception of potassium and sodium bicarbonate, the above‐mentioned salts also halted or strongly reduced arthrospore germination. Potassium bicarbonate, and sodium bicarbonate, acetate and propionate significantly increased conidiation (p < 0.05). Of all the salts tested in vitro, only ammonium bicarbonate and carbonate, calcium oxide and sodium fluoride were toxic to G. candidum. In in vivo studies, all the calcium salts tested (acetate, chloride, citrate, formate, lactate, oxide, propionate and silicate), several of the sodium salts (acetate, bicarbonate, chloride and fluoride) and potassium bicarbonate exhibited both protective and curative activity against G. candidum, significantly reducing the severity of sour rot in comparison to pathogen‐inoculated controls (p < 0.05). Although no curative was observed with ammonium bicarbonate, ammonium carbonate, potassium carbonate, potassium chloride, sodium carbonate or sodium citrate, these salts also demonstrated significant protective activity against sour rot when compared to controls (p < 0.05). In sum, the study findings show that all of the selected salts may be used to control carrot sour rot, except for sodium fluoride, which exhibited phytotoxicity to carrots.     

Effects of melanin on high- and low- linear energy transfer (LET) radiation response of human epithelial cells

The search for effective radioprotectors is of major concern in the medical, military, environmental, and space sciences. Conventional radioprotectors are generally effective only during a single irradiation and display their radioprotective properties only at high, toxic concentrations. In addition, they reduce somatic radiation effects but are poorly efficient in protecting from hereditary stochastic radiation effects. In this respect, the pigment melanin merits attention. Experiments referring to potential melanin effects on the ionising radiation response have been carried out with different biological systems, both in vivo and in vitro. In this paper, we present results on the response to high- and low-linear energy transfer (LET) radiation of a human mammary epithelial cell line, H184B5 F5-1 M/10, supplemented by melanin. The incorporation of auto-oxidative (l-dopa) melanin was linear for concentrations from 3 to 10 μg/ml in the growth medium. Concentrations of up to 250 μg/ml did not significantly impair the cells proliferative ability. No significant protective effect of melanin on the survival of cultured cells after exposure to alpha-particles (130 keV/μm) or x-rays was observed. Received: 24 March 1997 / Accepted in revised form: 14 November 1997