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.     

Comparisons of NMR spectral quality and success in crystallization demonstrate that NMR and X-ray crystallography are complementary methods for small protein structure determination

X-ray crystallography and NMR spectroscopy provide the only sources of experimental data from which protein structures can be analyzed at high or even atomic resolution. The degree to which these methods complement each other as sources of structural knowledge is a matter of debate; it is often proposed that small proteins yielding high quality, readily analyzed NMR spectra are a subset of those that readily yield strongly diffracting crystals. We have examined the correlation between NMR spectral quality and success in structure determination by X-ray crystallography for 159 prokaryotic and eukaryotic proteins, prescreened to avoid proteins providing polydisperse and/or aggregated samples. This study demonstrates that, across this protein sample set, the quality of a protein's [15N-1H]-heteronuclear correlation (HSQC) spectrum recorded under conditions generally suitable for 3D structure determination by NMR, a key predictor of the ability to determine a structure by NMR, is not correlated with successful crystallization and structure determination by X-ray crystallography. These results, together with similar results of an independent study presented in the accompanying paper (Yee, et al., J. Am. Chem. Soc., accompanying paper), demonstrate that X-ray crystallography and NMR often provide complementary sources of structural data and that both methods are required in order to optimize success for as many targets as possible in large-scale structural proteomics efforts.     

Cyclophosphamides from aminosugars and aminonucleosides

Condensation of bis-(2-chloroethyl)phosphoramidic dichloride with 3′-amino-3′-deoxy-N,N-dimethyladenosine afforded the 2′,3′-cyclicphosphorodiamidate (III). By an improved synthesis, methyl 3-amino-3-deoxy-β-D-ribofuranoside was obtained as a model compound for conversion to the analogous 2,3-cyclicphosphorodiamidate (XII). Existence of the latter as two diastereomers due to phosphorus asymmetry was shown by nmr analysis, using comparison with the 5-(O-p-nitrobenzoate) (XIII) as a basis for assignments.     

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.