P-nitroacetophenone Research Articles

Smart TLC–densitometric methods for determination of ophthalmic ternary mixture containing chloramphenicol in the presence of its synthetic precursor: Comparative eco-scaling for greenness assessment

Green analytical methods have gained a growing interest in the field of pharmaceutical research to reduce impacts on the environment and enhance analysts’ health safety. Chloramphenicol (CHL), dexamethasone sodium phosphate (DSP) and tetrahydrozoline HCl (THZ) form an ophthalmic ternary mixture that is co-formulated for conjunctivitis treatment. In the present work, for time saving and higher sensitivity, two green thin-layer chromatography (TLC) methods were developed for the determination of this ophthalmic ternary mixture in the absence or presence of p-nitroacetophenone (PNA), a synthetic precursor of chloramphenicol. In both proposed methods, silica gel 60 F254 plates were used as the stationary phase. The mobile phase used for method (A) was ethanol‒water‒ammonia (7.0:2.5:0.5, V/V), while, for method (B), acetonitrile‒water‒ammonia (10.0:3.0:0.5, V/V) was used as the mobile phase. TLC separation was followed by quantitative determination of the aforementioned drugs at wavelengths 242.0 nm and 220.0 nm. Both methods were validated in compliance with the International Conference on Harmonisation (ICH) guidelines, where both methods were found to be reliable, reproducible, and selective. Statistical comparison of the developed methods was done with a reported high-performance liquid chromatography (HPLC) method where no significant difference was found. Analytical eco-scaling depends on penalty point which was calculated to be 92, 88 and 87 for methods A, B and the reported HPLC, respectively, suggesting that the proposed methods are eco-friendlier with penalty point scoring very high on the scale than the reported one.

N-Terminal Decarboxylation as a Probe for Intramolecular Contact Formation in γ-Glu-(Pro)n-Met Peptides.

The kinetics of intramolecular-contact formation between remote functional groups in peptides with restricted conformational flexibility were examined using designed peptides with variable-length proline bridges. As probes for this motion, free radicals were produced using the •OH-induced oxidation at the C-terminal methionine residue of γ-Glu-(Pro)n-Met peptides (n = 0–3). The progress of the radicals’ motion along the proline bridges was monitored as the radicals underwent reactions along the peptides’ backbones. Of particular interest was the reaction between the sulfur atom located in the side chain of the oxidized Met residue and the unprotonated amino group of the glutamic acid moiety. Interactions between them were probed by the radiation-chemical yields (expressed as G values) of the formation of C-centered, α-aminoalkyl radicals (αN) on the Glu residue. These radicals were monitored directly or via their reaction with p-nitroacetophenone (PNAP) to generate the optically detected PNAP•– radical anions. The yields of these αN radicals were found to be linearly dependent on the number of Pro residues. A constant decrease by 0.09 μM J–1 per spacing Pro residue of the radiation-chemical yields of G(αN) was observed. Previous reports support the conclusion that the αN radicals in these cases would have to result from (S∴N)+-bonded cyclic radical cations that arose as a result from direct contact between the ends of the peptides. Furthermore, by analogy with the rate constants for the formation of intramolecularly (S∴S)+-bonded radical cations in Met-(Pro)n-Met peptides (J. Phys. Chem. B2016, 120, 973227513096), the rate constants for the formation of intramolecularly (S∴N)+-bonded radical cations are activated to the same extent for all of the γ-Glu-(Pro)n-Met peptides. Thus, the continuous decrease of G(αN) with the number of Pro residues (from 0 to 3) suggests that the formation of a contact between the S-atom in the C-terminal Met residue and the N-atom of a deprotonated N-terminal amino group of Glu is controlled in peptides with 0 to 3 Pro residues by the relative diffusion of the S•+ and unoxidized N-atom. The overall rate constants of cyclization to form the (S∴N)-bonded radical cations were estimated to be 3.8 × 106, 1.8 × 106, and 8.1 × 105 s–1 for peptides with n = 0, 1, and 2 Pro residues, respectively. If activation is the same for all of the peptides, then these rate constants are a direct indication for the end-to-end dynamics along the chain.

Oxidative Degradation of Thiaproline Derivatives in Aqueous Solutions Induced by •OH Radicals

AbstractThe participation of neighboring amino and carboxyl groups in thiazolidyne‐4‐carboxylic acid (thiaproline) and its two derivatives, thiazolidyne‐2‐carboxylic acid and thiazolidyne‐2,4‐dicarboxylic acid, is demonstrated during .OH‐radical‐induced oxidation in aqueous solutions. The reaction of .OH radicals with these compounds does not lead to the expected one‐electron oxidized sulfur‐centered radical cations and subsequently to the intermolecularly (S∴S)‐bonded dimeric radical cations (even at very high concentration of thiaprolines (>50 mM)), but rather to the elimination of CO2 with the parallel formation of αN radicals. The latter radicals formed in thiaproline and thiazolidyne‐2,4‐dicarboxylic acid subsequently undergo β‐fragmentation of the CS bond, leading to the thiyl radicals (RS.). The αN and RS. radicals were probed and quantified by one‐electron reduction of p‐nitroacetophenone (PNAP) and by one‐electron oxidation of the monoanion of ascorbic acid (AH−), respectively. The calculated stabilization enthalpies of the αN radicals show that the loss of CO2 is thermodynamically a favorable process. The Gibbs free energies of β‐fragmentation processes in thiaproline and thiazolidyne‐2,4‐dicarboxylic acid are equal to −3.7 and −10.2 kJ mol−1, respectively, showing that at room temperature both are exergonic. A general .OH‐radical‐induced oxidation mechanism of thiaproline derivatives in aqueous solutions is proposed.

Resonance Raman spectroscopic and density functional theory study of p-nitroacetophenone (PNAP)

Resonance Raman spectra of p-nitroacetophenone(PNAP) have been obtained in resonance with the charge-transfer (CT) band using 252.7, 266 and 273.9 nm in methanol solvent. The spectra indicate that the Franck–Condon region photodissociation dynamics have multidimensional character with motion mainly along the C O stretching ν 8(1691 cm −1) and the benzene ring stretch ν 10(1593 cm −1). A preliminary resonance Raman intensity analysis was done and the results for PNAP were compared with nitrobenzene and aceptophenone. Our results indicate that –NO 2 is more photoactive than –COCH 3. The isomerization process of PNAP takes place somewhere after the wave packet leaves the Franck–Condon region.

Role of radiolytically generated species in radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution: Steady state and pulse radiolysis study

Radiation induced polymerization of sodium p-styrene sulphonate (SSS) in aqueous solution has been investigated by steady state and pulse radiolysis techniques. Effect of dose, dose rate, monomer concentration, pH and ambient conditions on polymerization was investigated. The reactions of primary radicals of water radiolysis such as OH radical, e − aq, H atom, O − and some oxidizing radicals like N 3, Cl − 2,Br − 2, and reducing specie like CO − 2 with SSS have also been investigated. SSS reacts with OH radical with a rate constant of 5.9×10 9 dm 3 mol −1s −1 at pH 6.3. The results indicate that ∼83% of OH radicals undergo electron transfer reaction resulting in a cation radical species while remaining ∼17% react via addition reaction. The hydrated electron reacts with SSS with a rate constant 1.3×10 10 dm 3 mol −1 s −1 to form an anion that undergoes fast protonation to form H-adduct at pH 6.3. At high pH (>10) the anion is able to transfer electron to methyl vilogen and p-nitro aceto phenone ( p-NAP) where as H-adduct is unable to transfer electron. At pH ∼1 H atom reaction with SSS is diffusion controlled with a rate constant of 5×10 9 dm 3 mol −1 s −1 and results in formation of H adduct. It was seen that anion reacts with solute an order faster than cation generated radiolytically indicating anionic initiation of polymerization of SSS. Molecular weight of the polymer formed by radiation polymerization, determined by viscosity measurement, are of the order of 10 7 and higher molecular weight polymers are obtained at lower dose rates. In presence of a crosslinking agent gelation of polymer is much faster than the monomer and a polymer concentration ∼20% is most efficiently crosslinked.

Kinetics of Aminodinitrotoluene Oxidations with Ozone and Hydroxyl Radical

Aminodinitrotoluenes [2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT)] are serious groundwater contaminants commonly found in soils and groundwaters near TNT production facilities. To evaluate the kinetics and pathways for their oxidation in peroxone (ozone and hydrogen peroxide) oxidizing systems where both hydroxyl (HO) radical and ozone are important oxidants, competition kinetics and modeling experiments were done. ADNTs react rapidly with both ozone and HO radical. From competition kinetics with resorcinol as a reference, ozone rate constants of 1.45 x 10 5 and 1.8 x 10 5 M -1 s -1 were determined for 2- and 4-ADNT, respectively. HO radical rate constants, determined using p-nitroacetophenone (PNAP) as a reference compound, are 1.6 x 10 9 and 1.9 x 10 9 M -1 s -1 for 2- and 4-ADNT, respectively. Although rate constants for HO radical oxidations are 4 orders of magnitude larger than those for ozone, modeling shows that ozone is the dominant oxidant for ADNTs in peroxone mixtures, except at ADNTs concentrations below 1 μM (200 ppb).

Studies on p-nitroacetophenone-sensitized lipid peroxidation

p-Nitroacetophenone (PNAP)-sensitized lipid peroxidation is studied in egg lecithin solutions and liposomes (lipid:sensitizer=100:1 and 50:1, w/w). Lipid peroxidation is studied by measuring malondialdehydes (MDA) using MDA-TBA (2-thiobarbituric acid) absorption assay and fluorescence assay and conjugated dienes by UV absorption assay simultaneously in lipid solutions. Membrane damage induced by PNAP-sensitized lipid peroxidation is studied in liposomes using the spin label technique. Mechanistic studies indicate the involvement of singlet oxygen (type II) in the reactions.

Studies on p-nitroacetophenone triplet state

p-Nitroacetophenone (PNAP) triplet state properties were investigated using laser flash photolysis and phosphorescence techniques. Acetonitrile solutions of PNAP produced short-lived (approximately 3 μs) triplets on excitation at 266 nm. PNAP produced phosphorescence on excitation at 278 nm with a decay time of 15 ms. The absorption and fluorescence properties of PNAP were also investigated.

Decarboxylation mechanism of the n-terminal glutamyl moiety in γ-glutamic acid and methionine containing peptides

The reaction of hydroxyl radicals with γ-glutamyl-methionine and γ-glutamyl-glycyl-methionyl-glycine at neutral pH results in similar N-terminal decarboxylation efficiency. The underlying mechanism involves an intramolecular proton transfer from the protonated N-terminal amino group of the glutamyl moiety to an initially formed hydroxy sulphuranyl radical at the methionine residue. This process leads to the formation of a three-electron bonded [> S∴NH 2] +- peptide intermediate subsequently decomposing into CO 2 and an α-amino radical of the structure H 2NCH .CH 2CH 2C(O)NH- peptide. This radical has been identified via reduction of a moderately good electron acceptor such as p-nitroacetophenone (PNAP). The arrangement within a sterically favourable 5-membered ring, as observed with methionine, is not a necessary prerequisite for the formation of [> S∴NH 2] +- type intermediate. Mechanistically, the formation of CO 2 and an α-amino radical suggests the occurrence of an intramolecular electron transfer from the carboxylate group to the electron-deficient center at the nitrogen within the S∴N-bond followed by homolytic bond breakage of the carbon-carboxylate bond. The decarboxylation benefits in particular from stabilization of the arising carbon-centered radical by a free lone pair from the α-amino group. This process seems to occur well in larger peptide structures provided they contain an N-terminal carboxyl group α to an amino function and they are flexible enough to allow the protonated amino function to interact with the hydroxyl sulphuranyl radical at the methionine residue.

Reaction of hydroxyl radicals with alkyl phosphates and the oxidation of phosphatoalkyl radicals by nitro compounds.

The rate constants for reactions of hydroxyl radicals with a number of alkyl phosphates have been determined by competition with KSCN. Hydroxyl radicals react with alkyl phosphates preferentially by H-abstraction at the alpha-position of the phosphate functions. The resulting alpha-phosphatoalkyl radicals are not very efficient one-electron reducing agents towards nitro compounds. They react with tetranitromethane (TNM) by addition to form adduct intermediates with absorption maxima at about 300 nm. The rate constants for decay of these TNM adducts to produce the nitroform anion (NF-) and the corresponding alpha-phosphato-alcohols have been determined by optical and/or conductance detection. The stability of these TNM adducts varies considerably with the chain length (methyl > ethyl > isopropyl) and number (trialkyl > dialkyl > monoalkyl) of the alkyl substituents. Additional formation of proton during or after the decay of the TNM adducts has been tentatively attributed to the hydrolysis of the alpha-phosphato-alcohols. Alpha-Phosphatoalkyl radicals derived from trimethyl, triethyl, triisopropyl, and diethyl phosphates react with p-nitroacetophenone (PNAP) very slowly (k < 5 x 10(7) dm3mol-1S-1) possibly forming adducts. One-electron reduction of PNAP by these radicals to PNAP.- was not observed under pulse radiolysis conditions. The rate constants for the reactions of .OH with glycerol 1-phosphate and glycerol 2-phosphate have been redetermined by competition with KSCN. Using the radical scavengers N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and TNM, the percentage of .OH attack at each carbon atom was obtained. Contrary to the simple alkyl phosphates described above, the alpha-position to the phosphate function is the least favoured (10-15% in glycerol 1-phosphate and 6% in glycerol 2-phosphate). These so-formed alpha-phosphatoalkyl radicals react with TNM also by forming adducts. The beta-phosphatoalkyl radicals in both cases eliminate inorganic phosphate on formation (k > 10(6)S-1). The gamma-phosphatoalkyl radical from glycerol 1-phosphate undergoes base-catalysed water elimination (kobs = 1.8 x 10(5)S-1 at pH 10.6) to give an oxidizing radical. Products in the gamma-radiolysis of N2O-saturated solutions of glycerol 1-phosphate and glycerol 2-phosphate have been identified and their yields determined. The mechanisms for their formation are discussed.

Addition of e-aq and H atoms to hypoxanthine and inosine and the reactions of alpha-hydroxyalkyl radicals with purines. A pulse radiolysis and product analysis study.

The reactions of hydrated electrons e-aq with hypoxanthine and inosine were followed using pulse radiolysis methods. In a neutral solution the electron adduct of inosine is immediately protonated at the heteroatoms of the purine ring by water (k >> 2.5 x 10(6)s-1) to give In(N,O-H).. These N,O-protonated intermediates have a single absorption maximum at 300 nm. In basic solution the protonation of the electron adduct of inosine by water leads to other intermediate products with an absorption maximum at 350 nm. These intermediates are believed to be the C-protonated electron adducts of inosine (In(N,O-H).). In (N,O-H). and In(C-H). differ strongly in their ability to reduce p-nitroacetophenone (PNAP). In(N,O-H). are strong reductants and reduce PNAP quantitatively to PNAP.-. Based on the pH dependence of PNAP.- yields, two types of tautomers of In(C-H). could be distinguished. One of the tautomers can reduce PNAP, albeit with slower rate than In(N,O-H)., the other tautomer has no reducing properties. The latter is the one with the higher pKa and therefore thermodynamically more stable. The absorption spectrum of the intermediates produced in the reaction of e-aq with hypoxanthine at neutral pH is very similar to that of In(N,O-H). with a maximum at 300 nm. However, no build-up at 350 nm was observed in basic solution as in the case of the electron adduct of inosine. The reaction of H atoms with inosine produces in basic solution intermediate radicals with the same absorption spectrum as the C-protonated electron adducts of inosine. It is suggested that both the reactions of e-aq and H. with inosine in basic solution produce the same radical, namely the H-adduct of inosine (In(C-H)) with the highest pKa. alpha-Hydroxyalkyl radicals were found to react very slowly with purine bases and nucleosides in neutral to basic solutions. In acidic solution their reactivity increases and a number of rate constants were determined by pulse radiolysis measurements at pH 0.4. The intermediates from the reaction of 2-hydroxy-2-propyl radicals with inosine could be observed pulse spectrometrically in neutral and in basic solutions. In basic solution this reaction leads to intermediates with the same absorption maximum at 350 nm as that of the H-adduct of inosine. Furthermore, the yield of acetone was found to increase strongly in basic pH.(ABSTRACT TRUNCATED AT 400 WORDS)

Interindividual variability of carbonyl reductase levels in human livers

Interindividual variability of carbonyl reductase levels in human livers (N = 11) was examined by measuring reductase activity toward various substrates and by western blot analysis using anti-rat ovarian carbonyl reductase CR2 antibody. The carbonyl reductase activity toward p-nitrobenzaldehyde (PNBA) ( 58.1 ± 5.4 nmol mg protein/min, mean ± SE) was highest among the substrates examined, followed by 4-benzoylpyridine (4BP) ( 14.4 ± 2.0 nmol mg protein/min and p-nitroacetophenone (PNAP) ( 2.00 ± 0.37 nmol mg protein/min). The reductase activity ( 6.33 ± 0.56 nmol mg protein/min) toward 13, 14-dihydro-15-keto-prostaglandin F 2α (ISKD-PGF 2α), which is a diagnostic substrate for rat ovarian carbonyl reductases, was relatively high compared to that in other species. Western blot analysis revealed that each human liver contained several immunoreactive proteins to anti-CR2 antibody. The activities toward 15KD-PGF 2α ( r = 0.85, P < 0.01) and 4BP ( r = 0.84, P < 0.01), but not PNBA ( r = 0.53, not significant) or PNAP ( r = 0.52, not significant), were closely correlated with the relative amounts of the high molecular weight immunoreactive proteins determined with a densitometer. Thus, the major carbonyl reductases in human liver are similar to those of rat ovarian enzymes.

Gonadotropin-induced ovarian carbonyl reductase in mice and hamsters: Comparison with carbonyl reductase in rats

We investigated the effects of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) on ovarian carbonyl reductase activities towards 13, 14-dihydro-15-ketoprostaglandin F 2α (15KD-PGF 2α), p-nitroacetophenone (PNAP) and p-nitrobenzaldehyde (PNBA) in mice and hamsters, and compared with their effects on those we observed previously in rats. The treatment with PMSG and hCG caused a significant increase in ovarian weights and superovulation in both mice and hamsters. Hamster ovary possessed appreciable carbonyl reductase activities towards all three substrates. whereas the activities were lower than those in rat ovary. The reductase activities were not increased by the treatment with gonadotropins, differing from rat ovarian carbonyl reductase. In untreated mice, carbonyl reductase activity towards 15KD-PGF 2α was not detected, whereas the activities towards PNAP and PNBA were detected, which activities were lower than those in rats and hamsters. The PNAP and PNBA reductase activities in mouse ovary were significantly increased up to 7.1- and 1.7-fold, respectively, by the treatment with gonadotropins. These results show that there are species differences in ovarian carbonyl reductase and response of the enzyme to gonadotropins.

ChemInform Abstract: Formation of Reducing Radicals on Radiolysis of Glutathione and Some Related Compounds in Aqueous Solution

The ˙OH-induced oxidation of glutathione in basic aqueous solution has been found to produce the sulphur-centred radical GS˙(GSSG–˙) and two reducing radicals. Decarboxylation, considered to be initiated by ˙OH radical addition to the nitrogen of the amino group on the γ-glutamyl unit, was found to be effective for methylated glutathione (GSMe) and opthalmic acid (GMe) but of minor importance for glutathione. The G-values for the strongly reducing α-amino radicals formed on decarboxylation were found to be 3.3, 3.3, and 0.5 for GSMe, GMe, and GSH, respectively, at pH 10.5. The formation of an additional strongly reducing radical with G= 2.2 at pH 10.5 was demonstrated by measuring the electron-transfer to p-nitroacetophenone (PNAP). This radical is not formed from GSMe or GMe. We suggest that the underlying mechanism for the formation of this species is based on pH-dependent conformational changes of glutathione followed by ˙OH addition to the cysteine sulphur, or hydrogen abstraction from the CH2 group in the α-position to the sulphur leading to the formation of a reducing carbon-centred radical.

Formation of reducing radicals on radiolysis of glutathione and some related compounds in aqueous solution

The ˙OH-induced oxidation of glutathione in basic aqueous solution has been found to produce the sulphur-centred radical GS˙(GSSG–˙) and two reducing radicals. Decarboxylation, considered to be initiated by ˙OH radical addition to the nitrogen of the amino group on the γ-glutamyl unit, was found to be effective for methylated glutathione (GSMe) and opthalmic acid (GMe) but of minor importance for glutathione. The G-values for the strongly reducing α-amino radicals formed on decarboxylation were found to be 3.3, 3.3, and 0.5 for GSMe, GMe, and GSH, respectively, at pH 10.5. The formation of an additional strongly reducing radical with G= 2.2 at pH 10.5 was demonstrated by measuring the electron-transfer to p-nitroacetophenone (PNAP). This radical is not formed from GSMe or GMe. We suggest that the underlying mechanism for the formation of this species is based on pH-dependent conformational changes of glutathione followed by ˙OH addition to the cysteine sulphur, or hydrogen abstraction from the CH2 group in the α-position to the sulphur leading to the formation of a reducing carbon-centred radical.

Radiation-induced molecular size changes in DNA in the presence of p-nitroacetophenone. Pulse radiolysis in conjunction with light-scattering measurements.

Native calf thymus DNA, denatured DNA, and synthetic nucleic acids (poly A, poly C, poly U, and poly G) crosslink upon irradiation with 16 MeV electrons in O2-free dilute aqueous solutions containing 0.5mol/l t-butanol and p-nitroacetophenone (PNAP) or nitrobenzene at concentrations between 10(-4) to 10(-3) mol/l. The occurrence of crosslinking was inferred from the increase of the light-scattering intensity after the irradiation with a 100ns electron pulse. The mechanism of crosslinking is based on the indirect action of radiation, typical 100eV yields G(X) being between 10(-5) and 10(-4). The attack of unsaturations in pendant bases by anion radicals PNAP- or by dimer anion radicals (PNAP)2 radical leading to pendant macroradicals appears to be feasible. Combination of the latter causes crosslinkages. Rate constants and yields of crosslinking depend strongly on the ionic strength. Evidence for counteracting kinetic salt- and steric hindrance effects has been obtained.

The Reactions of the 2′-deoxyadenosine Electron Adduct in Aqueous Solution. The Effects of the Radiosensitizerp-nitroacetophenone. A Pulse Spectroscopic and Pulse Conductometric Study

The reactions of the one electron adduct of 2'-deoxyadenosine dA(-), in aqueous solutions have been studied using pulse radiolysis techniques with optical absorption and conductivity detection. The dA(-) radical anion itself shows a weak and featureless optical absorption at greater than 300 nm. It reacts rapidly with H20 (k equals 6 x 10(4)M(-1)s(-1); t1/2 equals 210 ns) to yield at least three different protonated structures (dAH., dA'H., dA"H.). In neutral solutions the most important of these (dAH., lambda(max) equals 315 nm) decays by a first order process (t1/2 approximately equal to 9 microseconds). In basic solutions dAH. undergoes on OH- catalysed rearrangement into another neutral radical (dA"'H., lambda(max) equals 355 nm; k(dAH. plus OH-) equals 1.7 x 10(8)M(-1)s(-1)). p-Nitroacetophenone (PNAP) reacts rapidly with the protonated electron adducts of 2'-deoxyadenosine (k equals 5 x 10(9)M(-1)s(-1)). An electron transfer occurs with dAH to yield PNAP and a reoxidized form of 2'-deoxyadenosine. As indicated by its pK value of 8.8 the latter is not, however, simply a repaired 2'-deoxyadenosine molecule, but is suggested to include the elements of water. Species dA"'H.(and dA'H.) react with PNAP in a process which is clearly not an electron transfer but likely an addition reaction.

Effects of hypoxic cell radiosensitizers on the activity of ATPases.

Misonidazole (MIS, Ro-07-0582, 1-(2'-hydroxy-3'-methoxypropyl)-2nitroimidazole) was a gift from Hoffman-La Roche Ltd. Basle, Switzerland ; metronidazole (MET, 1-(2'-hydroxyethyl)-2-methyl-5-nitroimidazole) was purchased from May and Baker Ltd . England; PNAP (p-nitroacetophenone) and NDPP (Ro-03-6156, p-nitro-(3-dimethylamino)-propiophenone) were a gift from Dr . L. Revesz of the Karolinska Institute, Stockholm ; DNP (2,4-dinitrophenol) was provided by Fluka A .G.,Switzerland; ATP (adenosine-5'-triphosphoric acid disodium salt) was from Merck, Germany ; Tris (Trishydroxymethylaminomethane) was from Loba-Chimie, Wien ; EDTA (ethylendiaminotetraacetic acid) and dextran sulphate 500 were obtained from Sigma Chemical Co

On the Influence of p-Nitroacetophenone on Radiation-Induced Molecular Size Changes of DNA

DNA has been irradiated in aqueous solutions with 16 MeV electron pulses (duration: 50- 100 ns). In the presence of p-nitroacetophenone (PNAP) the light scattering intensity (LSI) increased after the pulse in Ar- and 02-saturated solutions indicating intermolecular crosslinking. The LSI increase was greatest in Ar-sat. solutions containing t-butanol (1 mol/1). In the absence of PNAP and t-butanol DNA was degraded as indicated by a decrease of LSI. The results contribute to the understanding of radiation-induced reactions, DNA undergoes in the presence of sensitizers of high electron affinity

Additive Sensitization of Bacterial Spores by Oxygen and p-Nitroacetophenone

In the bacterial spore, the sensitizing effects of both oxygen and p-nitroacetophenone (PNAP) can be separated into components. Each sensitizer has a component of damage which involves reactions of hydroxyl radicals (·OH), although the origins of these components may be different. Tests which use different concentrations of PNAP and O2 simultaneously have been run to seek interactions or additivities in their effects on lethal radiation sensitivity. The results show that the effects of the PNAP non-·OH component are additive to those of both O2 non-·OH components; however, the patterns of this additivity suggest that the chemical processes through which PNAP acts are similar to those of the $\text{high-}{\rm O}_{2}$ component (that is, the component which occurs at $[{\rm O}_{2}]>5\times 10^{-5} M$) but are different from those of the $\text{low-}{\rm O}_{2}$ component. There is also indirect evidence that the sensitizing reactions of the $\text{high-}{\rm O}_{2}$ component may replace those reaction...