Evaluation of an Economical Sunlamp that Emits a Near Solar UV Power Spectrum for Conducting Photoimmunological and Sunscreen Immune Protection Studies

Expense and inconvenience have restricted the use of the filtered xenon are lamp (solar simulator) as a UV source for conducting large-scale animal studies. Because sunscreen immunoprotective levels are significantly affected by the UV power spectrum of the source it is imperative that a solar simulating source be used for accurate measurements of sunscreen protection levels that are relevant to human UV exposures from sunlight. However, relatively inexpensive sunlamps, e. g. the UVA-340, that emit a UV power spectrum similar to that of a solar simulator are available. Unlike FS-type UVB sunlamps, which have a significant amount of effective immunosuppressive nonsolar UV energy at wavelengths below 295 nm, the immunosuppression effectiveness spectrum of UVA-340 sunlamps was nearly identical to that of a solar simulator. The purpose of this study was to evaluate this sunlamp for conducting photoimmunological and sunscreen immune protection studies. Groups of C3H mice were exposed to a range of UVA-340 sunlamp doses (0.25 KJ/m² to 20.0 KJ/m²) to establish a dose-response curve and determine the minimum immune suppression dose (MISD) for induction of local-type suppression of contact hypersensitivity (CH). The MISD, defined as the lowest UV dose given to produce ～50% suppression of the CH response in mice, was determined to be 1.0 kJ/m² for UVA-340 sunlamps. Immune protection tests on four marketed sunscreen lotions (sun protection factors [SPF] 4, 8, 15 and 30) were then conducted with UVA-340 sunlamps using MISD as the endpoint. The immune protection factors for these sunscreens were equivalent to the level of protection predicated by their labeled SPF. These results are similar to those we have previously obtained using a solar simulator. We conclude from these data that the immunosuppressive effects of UVA-340 sunlamps are similar to those of a solar simulator; however, further studies are needed to determine if UVA-340, or similar, sunlamps are a viable alternative to the solar simulator for conducting large-scale animal experiments that require a relevant UV solar spectrum.     

Optical activity in the biaryl series

The relationship between the CD spectra of the chiral biaryls and their stereochemical configuration, as a function of the dihedral angle between the molecular planes of the aromatic moieties, has been investigated for biphenyl, 1,1′-binaphthyl, 1,1′-bianthryl and 9,9′-bianthryl in the exciton approximation and, for the 1,1′-binaphthyls, in the π-SCF approximation. Both methods provide unambiguous assignments of absolute configuration except for biaryls with a critical dihedral angle of π/2 in those with effective D_data2 chromophoric symmetry, or 100–110° in the case of the 1,1′-binaphthyls.     

Engineering switches, genetically

Ostermeier, Guntas, and Mitchel describe a new approach to design enzymes that are allosterically regulated by an unrelated ligand . The resulting protein, constructed by nonhomologous recombination and genetic screens, displays switch-like behavior.     

Electron spin resonance spectra of some phosphonyl radicals and related species

The isotropic ESR spectra of a number of phosphonyl radicals (X₂$\text{P}$O), the dimethylphosphinyl radical, and the phosphoranyl radical (MeO)₃$\text{P}$OBu-t, are described, and accurate values of the phosphorus hyperfine splittings and g-factors are reported. For X₂$\text{P}$O, the value of a(P) increases and the g-factor decreases as the electronegativity of X increases. There is a linear relationship between a(P) for X₂$\text{P}$O and ¹J(PH) for X₂P(O)H, but the same relationship does not hold for Me₂P- and Me₂PH. The spectrum of the di-n-hexylphosphonyl radical shows coupling to two pairs of α-methylene protons, and this non-equivalence is attributed to the pyramidal structure of the phosphonyl radical.     

Folic acid analogs. Modifications in the benzene-ring region. 5. 2′,6′-diazafolic acid

The synthesis of 2′,6′-diazafolic acid was accomplished by the condensation of 2-acetylamino-4(3H)pteridinone-6-earboxaldehyde (XIV) with diethyl N-[(5-amino-2-pyrimidinyl)carbonyl]-L-glutamate (XIII) followed by reduction of the anil double bond and alkaline hydrolylic cleavage of the N²-acetyl and ethyl ester protecting groups. Intermediate XIII was prepared by starling with 5-nitro-2-styrylpyrimidine (VI) and proceeding via 5-arnino-2-styrylpyrimidine (IX). The henzyloxycarbonyl derivative of IX was prepared and oxidized to the corresponding 5-benzyloxycarbonylaminopyrimidine-2-carboxylic acid (XI). The coupling of XI with diethyl L-glutamate followed by hydrogenolysis of the henzyloxycarbonyl function afforded the desired intermediate XIII. 2′,6′-Diazafolic acid was a potent inhibitor of Streptococcus faecium and displayed marginal activity against leukemia 1,1210 in mice.     

Kinetics and mechanism of aromatic thalliation and mercuriation-an NMR study

The rates of reaction of Tl (III) tris(trifluoroacetate) with benzene toluene and t-butylbenzene in solvent trifluoroacetic acid have been measured by an NMR method. The reaction products have been unambiguously determined from the thallium-hydrogen coupling constants. In the case of toluene, p-tolylthallium bis(trifluoroacetate) crystallised from reaction mixtures.Thalliation was shown to be reversible and to be between one and two orders of magnitude slower than mercuriation. The inductive order of the reactivity (tBu > Me ? H) was found in contrast to the hyperconjugative order for mercuriation. Hammett plots using σ⁺ values yielded a ? value of ?7.4 but the limited data correlated better with σ values (? = ?12.8). A primary isotope effect of 5.0 was found for toluene indicating rate-determining proton transfer. The mechanism is discussed in the light of these and other findings. In addition the rates of interconversion of the products of mercuriation of toluene are reported from NMR data.     

Coulomb interaction in the one-dimensional free-electron model

In the limiting case of the free-electron theory where the electron motion is constricted to one dimension, the one-dimensional Coulomb potential gives rise to divergent interaction integrals. It is shown that a proposal by Olszewski to remove the divergenses by first evaluating the integrals in the three-dimensional case and then passing to the limit of one dimension only is incorrect, and that convergent integrals may only be obtained by suitably modifying the original one-dimensional Coulomb potential between particles.

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Zusammenfassung In dem Grenzfall des Modells der Freien Elektronen, in dem die Elektronenbewegung auf eine Dimension eingeschrÄnkt ist, ergibt das eindimensionale Coulombpotential divergente Wechselwirkungsintegrale. Es wird gezeigt, da\ ein Vorschlag von Olszewski zur Aufhebung der Divergenz durch übergang von dreidimensionalen zum eindimensionalen Integral falsch ist. Konvergente Integrale können nur durch geeignete VerÄnderung des ursprünglichen eindimensionalen Coulombpotentials erhalten werden.

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Résumé Dans le cas limite de la théorie de l'électron libre à une dimension, le potentiel coulombien donne lieu à des intégrales d'interaction divergentes. On montre que la proposition d'Oszewski pour éliminer les divergences, en évaluant d'abord les intégrales tridimensionnelles et en passant à la limite à une dimension, est incorrecte et que des intégrales convergentes ne peuvent Être obtenues qu'en modifiant le potentiel coulombien unidimensionnel entre particules.

     

Reactions of ketenes with ethoxyalkynes: Synthesis of 2,2,4-trialkylcyclobutane-1,3-diones

Treatment of dimethyl ketene with ethoxyacetylene 1a, 1-ethoxyoct-1-yne 1b, and 1-ethoxytetrade-1-yne 1c afforded the 3-ethoxycyclobutenones 2a–c. Hydrolysis of 2a–c with dilute hydrochloric acid gave the cyclobutane-1,3-diones 3a–c. The ¹H NMR spectra of these compounds indicate that in CDCl₃ solution 2,2-dimethylcyclobutane-1,3-dione 3a exists as the diketone, whereas the 2,2,4-trialkylcyclobutane-1,3-diones 3b and 3c exist as the monoenols.