SOLAR DOSIMETRY WITH REPAIR DEFICIENT BACTERIAL SPORES: ACTION SPECTRA, PHOTOPRODUCT MEASUREMENTS AND A COMPARISON WITH OTHER BIOLOGICAL SYSTEMS

Abstract— Populations of radiation sensitive spores ( Bacillus subtilis UVSSP), vegetative bacteria ( E. coli K12-AB2480) and bacteriophage ( E. coli phage T4vx) have been considered as possible biological dosimeters to integrate DNA-absorbed solar energy incident on the Earth's surface.
Irradiation of spores of B. subtilis UVSSP with monochromatic far- and near-UV radiation and solar radiation have indicated that these radiations have a similar efficiency in inducing spore photoproducts per lethal event. Action spectra for lethality taken with the three radiation sensitive biological systems show a similar pattern in each case with a broad shoulder in the 334–365 nm wavelength region. This finding indicates a relatively high susceptibility of the DNA to chemical alteration in this wavelength range. Although less sensitive to sunlight than the other biological systems tested, the B. subtilis UVSSP spore mutant has the advantage of temperature independence of inactivation, stability between irradiation and assay and a simple, reproducible irradiation and assay procedure. Field measurements have supported the utility of this mutant as a sunlight dosimeter.     

An investigation of mononuclear and binuclear palladium(II) complexes of egta (egta = glycine,N,N′-(1,2-ethanediylbis(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) by 1H-, 13C- and 15N-n.m.r. methods

1:1 and 2:1 palladium(II) complexes of egta^4– (egta^4– = glycine, N,N-(1,2-ethanediylbis)(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) were prepared by 1:1 and 2:1 addition of K₂PdCl₄ to K₄egta, and examined by ¹H-, ¹³C- and ¹⁵N-n.m.r. methods. The 1:1 complex, [Pd(egta)]^2– in solution, utilizes a square-planar coordination comprised of two nitrogen and two glycinato carboxylate donors of egta^4–, leaving two glycinato carboxylates pendant. The complex has a cis-(R,S) stereochemistry which places both pendant carboxylates below the PdN₂O₂ square plane and the tether backbone of egta^4– in the up, up sense above the same plane. The cis-(R,S) assignment was assisted by computer simulations of the ¹³C-n.m.r. spectrum for four possible isomers. Only cis-(R,S) and trans-(R,R) calculated ¹³C-spectra were compatible with the observed ¹³C-n.m.r. pattern. The HH NOESY spectrum of [Pd(egta)]^2– detects long range coupling of the backbone –OCH₂CH₂O– linkage with both coordinated and pendant glycinato CH₂ moieties. The cis-(R,S) isomer's tortional movements allow such contacts whereas a trans-(R,R) isomer does not. The 2:1 complex, [Pd₂(egta)(H₂O)₂] in solution has an extended-chain structure with each palladium(II) center coordinated in the mer-iminodiacetate-like coordination with two bound glycinato-functionalities.     

Molecular and absolute crystal structure of pindolol-1-(1H-indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol: A specific beta-adrenoreceptor antagonist with partial agonist activity

The crystal and molecular structure of pindolol, 1-(1H indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol, has been determined by direct methods. Crystals are tetragonal, ,a=b=15.809(4),c=11.246(2) Å,Z=8,D _c=1.174 mg m^–3. The finalR-factor for 2271 reflections withI>2(I) is 0.038. Refinement by full-matrix least-squares on F² also enabled the absolute configuration of the structure to be established. The molecule is essentially planar, including much of the side-chain which is stabilized by the existence of two intramolecular H-bonds, between the ethyl oxygen and OH group, and between the OH and side-chain amide groups, respectively. The crystal structure is formed by three intermolecular hydrogen bonds including two side-chain-side-chain interactions, between ethyl oxygen to amide and OH to amide, and an interaction between the side-chain OH to indole NH.     

Five coordination modes of 4-aminopyrimidine with N-hydroxy-ethylethylenediaminetriacetatoruthenate(II)

Summary The complex [Ru^II(hedta)(4NH₂pym)]⁻, hedta³⁻ = N-hydroxyethylethylenediaminetriacetate, 4NH₂pym = 4-aminopyrimidine, exists at pH 7 as five different coordination isomers, which are most readily distinguished by their electrochemical waves in comparison with the 2-aminopyridine (2NH₂py) complex. The 2NH₂py complex exhibits N(1) (pyridine bound), exo-NH₂ (amine bound) and N(1), NH₂-chelated species. The 4NH₂pym complex forms N(1), exo-amine and N(3), NH₂-chelated isomers analogues to the 2NH₂py species, but also engages in η² (olefin bound) coordination of the dearomatized 4NH₂pym ring in C(5)–C(6), and another η² type of complex involving electron density between N(1) and N(3) of the ring (η³ form). N(1), η² and η³ isomers have also been detected for unsubstituted pyrimidine (pym), 4-methylprimidine (4CH₃pym) and 2-aminopyrimidine (2NH₂pym). Electrochemical waves (V versus NHE) for the five isomers are assigned as follows: (Ru^II/III) exo-NH₂ (0.06 V), N(1) (0.29 V), η² (0.49 V); (Ru^II/III) η³ (0.76 V); N(3), NH₂-chelated (1.09 V).     

The influence of pentaamminerhodium(III) on the1H n.m.r. spectra and pyrrole pKas of coordinated imidazoles and pyrazoles

Summary The following [(NH₃)₅RhLH]Cl₃ salts were preparedvia the [(NH₃)₅Rh(O₃SCF₃)](O₃SCF₃)₂ synthetic route; LH=1-methylimidazole (1CH₃imH), 2-methylimidazole (2CH₃imH), 4-methylimidazole (4CH₃imH), 5-methylimidazole(5CH₃imH), and pyrazole (pyzH). pK_a's at 25.0°C were determined for [(NH₃)₅RhLH]³⁺ complexes as follows: 2CH₃imH, 10.4±0.1; 5CH₃imH/4CH₃imH isomer mixture, 10.3±0.1; pyzH, 6.54±0.05. The influence on the pK_a's of imidazoles is dominated by withdrawal of the rhodium(III) centre and may be compensated by the presence of ring methylation by only 0.5log units for cobalt(III) and rhodium(III) derivatives, compared to 1.3 units for the -withdrawing ruthenium(III) centre. In the case of the -acceptor pyrazole ring, [(NH₃)₅Rh]³⁺ is observed to serve as a slight -donor and raises the pK_a above the cobalt(III) analogue. The¹H n.m.r. spectra of [(NH₃)₅RhLH]³⁺ complexes of the substituted imidazoles and pyrazole exhibit a deshielding order. C–2H>C–5H>C–4H for imidazoles and C–3H>C–5H>C–4H for pyrazole, as do their cobalt(III) analogues. The magnitude of values (=_{free L}-_complex) are virtually the same as in the cobalt(III) systems which shows that TIP influences are unimportant compared to ring rehybridization in estabilishing chemical shifts for both the cobalt(III) and rhodium(III) complexes. The imidazolato and pyrazolato complexes exhibit resonances upfield of the respective substituted imidazole or pyrazole complex in keeping with more negative charge on the rings; the influence is largest at C–2H of imidazolates and C–3H of pyrazolate.     

Thermogravimetric determination of magnesium,potassium and lead by precipitation with dilituric acid

The thermolysis curves of magnesium, potassium, and lead diliturate have established that either the hydrated or anhydrous forms of these precipitates are stable enough for their gravimetric use to be possible. Magnesium and lead were determined by precipitation with dilituric acid while potassium was precipitated with trimethylamine diliturate.     

REPAIR OF NEAR (365 nm)- AND FAR (254 nm)-UV DAMAGE TO BACTERIOPHAGE OF ESCHERICHIA COLI

Abstract: Intact bacteriophage have been irradiated at 365 nm or at 254 nm and then analysed for DNA photoproducts or injected into their bacterial host to test susceptibility of the damage to both phage and host-cell mediated repair systems. Both thymine dimers and single-strand breaks are induced in the phage DNA by 365 nm radiation. The dimers appear to be the major lethal lesion (approximately 2 dimers per lethal event) in both repair deficient bacteriophage T4 and bacteriophage λ. after irradiation with either 254 nm or 365 nm radiation. Damage induced in T4 by either wavelength is equally susceptible to x -gene reactivation (repair sector approximately 0.5). v -gene reactivation acts on a larger fraction of the near-UV damage (repair sector of 0.82 at 365 nm as against 0.66 at 254 nm). The host-cell mediated photoreactivation system is only slightly less effective for near-UV damage but host-cell reactivation (as measured by comparing survival of phage λ. on a uvr⁺ and a uvr^- host) is effective against a far smaller sector of near-UV damage (0.35) than far-UV damage (0.85). Weigle-reactivation (far-UV induced) of near-UV damage to phage λ is not observed. The results suggest that unless the near-UV damaged phage DNA is repaired immediately after injection. the lesions rapidly lose their susceptibility to repair with a consequent loss of activity of the phage particles.     

REC A +-DEPENDENT SYNERGISM BETWEEN 365 NM AND IONIZING RADIATION IN LOG-PHASE ESCHERICHIA COLI: A MODEL FOR OXYGEN-DEPENDENT NEAR-UV INACTIVATION BY DISRUPTION OF DNA REPAIR

Abstract —The oxygen dependence of 365 nm inactivation of colony-forming ability of Escherichia coli has been investigated in two series of DNA repair-deficient K12 mutants grown to mid-exponential phase. All strains except a uvr A rec A double mutant are more sensitive to inactivation under O₂ and show a lower threshold dose. The inactivation of photoreactivating enzyme in a crude cell extract and DNA repair disruption are both reduced when irradiation is carried out under nitrogen. The rec A gene-dependent synergism between 365 nm and ionising radiation is reversible if cells are incubated in full growth medium before ionising radiation treatment. In a wildtype strain, incubation for 2.5 h in full growth medium after 10⁶ J m^-2 365 nm radiation changes a sensitised response to a protection from ionising radiation. Protection is not seen at 1.5 times 10⁶ J m^-2. A tentative model for near UV lethality in logarithmic phase cells is suggested which proposes two classes of lesions. One requires oxygen for it's induction, is rapidly fixed as a lethal event as a result of repair disruption, and is primarily responsible for cell death after aerobic 365 nm irradiation. The other lesion, possibly pyrimidine dimers, may lead to cell death under anaerobic conditions.