OZONE AND ULTRAVIOLET-B IRRADIANCES: EXPERIMENTAL DETERMINATION OF THE RADIATION AMPLIFICATION FACTOR

Abstract— During the period 1981–1993, measurements of solar UV irradiances were made at the High-Alpine Research Station Jungfraujoch (Switzerland, 3576 m a.s.l.) to determine the radiation amplification factor (RAF) for the Robertson-Berger sunburn meter and for the narrow-band wavelength ranges of the Eppley filter spectrometer. The Robertson-Berger sunburn meter model 500 showed a RAF of 1.07 ± 0.15 at solar elevations between 20° and 60°. The RAF for human erythema is 1.1 in comparison. Therefore the Robertson-Berger sunburn meter is suitable to measure the influence of total atmospheric ozone variations on the effective erythemal irradiance. In the narrow-band wavelength ranges of the Eppley filter spectrometer the RAF increases greatly at shorter wavelengths with RAF of 1.06, 1.40 and 2.35 for the optical centers 315.1 nm, 311.1 nm and 305.2 nm, evaluated at 30° solar elevation. In order to minimize perturbations by aerosol optical depth and albedo in the evaluation of the RAF the ratios of UV irradiances to total irradiances were evaluated.     

THE EFFECT OF CHANGES OR DIFFERENCES IN ROBERTSON-BERGER RADIOMETER RESPONSIVITY ON SOLAR ULTRAVIOLET-B MEASUREMENT

Two long-term solar UV measurement campaigns, in the USA and in Austria, using Robertson-Berger radiometers found opposite trends for measured levels of ultraviolet-B radiation reaching the earth's surface. This could be a consequence of the method used to calibrate the radiometers. Changes or differences in responsivity were compensated for by adjusting the sensitivity of the field radiometers to match the output of a reference radiometer.
This radiometer intercomparison procedure has been evaluated in terms of the normalization wavelength to which the Robertson-Berger effective irradiance refers. There are small differences in spectral responsivities apparent in the radiometers used in the USA campaign, which require the field radiometers to be normalized at different wavelengths to match the response of the reference radiometer. This normalization wavelength is shown to depend on the time-averaged spectrum experienced by the instruments during the intercomparison. As a result there are substantial interradiometer variations in their calculated response to solar radiation when the measured spectral distribution is different from the spectrum used for the radiometer intercomparison procedure.     

ESTABLISHMENT and CHARACTERIZATION OF A MONOCLONAL ANTIBODY RECOGNIZING THE DEWAR ISOMERS OF(6–4)PHOTOPRODUCTS

Abstract— We established a monoclonal antibody(DEM–1) that recognizes UV-induced DNA damage other than cyclobutane pyrimidine dimers or(6–4)photoproducts. The binding ofDEM–1 antibody to 254 nm UV-irradiated DNA increased with subsequent exposure to UV wavelengths longer than 310 nm, whereas that of the 64M-2 antibody specific for the(6–4)photoproduct decreased with this treatment. Furthermore, the increase inDEM–1 binding was inhibited by the presence of the 64M-2 antibody during the exposure. We concluded that theDEM–1 antibody specifically recognized the Dewar photoproduct, which is the isomeric form of the(6–4)photoproduct. TheDEM–1 antibody, however, also bound to DNA irradiated with high fluences of 254 nm UV, suggesting that 254 nm UV could induce Dewar photoproducts without subsequent exposure to longer wavelengths of UV. Furthermore, an action spectral study demonstrated that 254 nm was the most efficient wavelength for Dewar photoproduct induction in the region from 254 to 365 nm, as well as cyclobutane dimers and(6–4)photoproducts, although the action spectrum values in the U V-B region were significantly higher compared with those for cyclobutane dimer and(6–4)photoproduct induction.     

SPECTRAL ALBEDO MEASUREMENTS IN THE UV and VISIBLE REGION OVER DIFFERENT TYPES OF SURFACES

Abstract— The spectral albedo of the earth's surface, i.e. the ratio between spectral irradiance reflected by the ground to all directions and global irradiance, was measured by a spectroradiometer in the UV and visible region from 290 nm to 800 nm with a spectral resolution of 1.5 nm at steps of 2 nm in the UV (290–400 nm) and 10 nm in the visible (400–800 nm) region. The measurements were performed over bare fertile soil, sand at the beach, concrete (autobahn) and snow as well as over different types of vegetation (grass, oats, rye, sugar-beet, stubble). As the albedo increases with increasing wavelengths for most types of surfaces considered, it is smaller in the UV than in the visible region. In the UVB region (λ < 315 nm) the measured albedo is as small as 0.016-0.017 over vegetation, 0.04-0.05 over bare fertile soil, 0.07-0.10 over concrete ("autobahn") and 0.62-0.76% over polluted snow with a small wavelength dependence. A somewhat higher albedo occurs in the UVA region (315 < λ < 400 nm) with values ranging from 0.02 over vegetation to 0.05 to 0.08 over bare soil. The albedo over dry bright sand, which is typically found at the beach, is significantly higher (0.14 at 300 nm to 0.24 at 400 nm) than over other snow-free surfaces, thus leading to an enhanced dose of biologically effective radiation at the beach.     

A NEW DOSIMETER FOR ULTRAVIOLET-B RADIATION

Abstract— A type of polycarbonate plastic was found to be sensitive to ultraviolet (UV) radiation. The damage to the material due to UV exposure was revealed by etching in a strong alkaline solution. The latent effect can be retained in the material for a period of at least 30 days. The material was tested for use as a detector of ultraviolet-B (UV-B 280–320 nm) radiation.
The response of the detector in the wavelength region between 254 and 365 nm was determined using a set of narrow-band filters and a 200 W UV xenon-mercury lamp. The maximum UV effect in the detector was observed at a wavelength of 290 nm. The spectral response curve was found to be similar to the human erythema action spectrum.
The detector may be miniaturized for dosimetric applications. The dose response curve is linear in the region up to an erythemal dose of 300 mJcm⁻². Laboratory and field tests showed that the dosimeter response to UV exposure was additive and was independent of dose rate. Further experiments suggested that the dosimeter was stable against changes in temperature and humidity.     

THE USE OF SHORT LIVED FLUORESCENT DYES TO CORRECT FOR ARTIFACTS IN THE MEASUREMENTS OF FLUORESCENCE LIFETIMES

Abstract— The ultrafast emission for fluorophores can be used as the effective excitation pulse for prompt response measurements by photo detectors in the same spectral region as that of unknown samples. This method corrects for such artifacts as wavelength and spatial dependence of the response function of the photodetector. It is shown that the emission from triphenylmethane dyes is an excellent effective pulse with relaxation time 2 ps in the red region of the spectrum. A microchannel plate photomultiplier has only a 35 ps increase in response or lag time between excitation at 420 nm and emission at 680 nm.     

THE WAVELENGTH DEPENDENCE OF THE EFFECT OF 8-METHOXYPSORALEN PLUS ULTRAVIOLET RADIATION ON THE INDUCTION OF LATENT SIMIAN VIRUS 40 FROM A MAMMALIAN CELL

Abstract— The effect of 8-methoxypsoralen (8-MOP) plus ultraviolet radiation (UV) of different wavelengths in the region 238–365 nm on the induction of SV40 from SV40-transformed Syrian hamster kidney cells was investigated. Results indicate that 8-MOP + UV treatment activates as much as 1000-fold more virus than UV alone at wavelengths in the region 302–365 nm. At wavelengths below 302 nm, 8-MOP addition to cells prior to irradiation shows little, if any, effect. A wavelength dependence for this viral induction is presented.     

THE ROLE OF HEMOGLOBIN IN THE PHOTOTAXIS OF THE NEMATODE Mermis nigrescens

Abstract A dense zone of crystalline hemoglobin in the head has been presumed to be involved in the photosensitivity of Mermis. With the aim of identifying its role, we have studied the wavelength dependence of the phototaxis. Measuring phototaxic efficiency at constant photon fluence rate (intensity), we find that the spectral response curve is approximately fiat from 350–540 nm and falls to an insignificant level by 580 nm. This is unlike the absorptance (fraction absorbed) spectrum of the hemoglobin pigmentation. Also, fluence-rate/response curves at 420 and 500 nm occur at the same fluence rates even though these wavelengths correspond to a maximum and a minimum of hemoglobin absorption. These results prove that the hemoglobin cannot be functioning as the visual pigment in phototaxis but, for reasons discussed, they neither confirm nor rule out a role as a shadowing pigment. The results are consistent with a shadowing role in the presence of contrast enhancement by the nervous system.
A steep fluence-rate dependence suggests that contrast enhancement does occur in Mermis phototaxis. The 420 or 500 nm fluence rate for half-maximal response is 6 times 10 photons s^-1 cm^-2 (about equivalent in effectiveness to pre-dawn twilight). The wide range of sensitivity, 350–560 nm, has interesting implications as to the nature of the visual pigment.
†NATO reaearch collaborator a n leave from the Department of Biophysics. Laboratorium voor Algemene Natuurkunde, Rijksuniversiteit Groningen, Westersin-gel 34. 9718 CM Groningen, The Netherlands.     

IMPROVED ANALYTIC CHARACTERIZATION OF ULTRAVIOLET SKYLIGHT

Abstract— We present an improved analytic characterization of diffuse spectral irradiance (skylight) for the wavelength range 280–380 nm and solar zenith angle range from 0 to 85°. The formulas achieve greater accuracy by (a) focusing on ratio representations and (b) adjusting the parameters to the more precise radiative transfer calculations of Dave, Braslau and Halpern.     

WAVELENGTH DEPENDENCE FOR AMT CROSSLINKING OF pBR322 DNA

Abstract The wavelength dependence for 4'aminomethyl-4,5',8-trimethylpsoralen crosslinking of a linearized plasmid DNA (pBR322) by narrow band UV-A light (298–382 nm) has been determined. Maximal levels of crosslinking occurred with light in the 322–346 nm range. Crosslinks were shown to be photoreversible by shorter wavelength photons (298 and 310 nm). The correlation between the wavelength dependence for crosslink formation and the optimal wavelength for most psoralen action spectra further supports the notion that crosslinks are the major lesion responsible for the effectiveness of psoralen plus ultraviolet A therapies.     

THE SPECTROSCOPY AND PHOTOCHEMISTRY OF ENAMINONITRILES INCLUDING THE SYNTHESIS AND IDENTIFICATION OF CIS-β-AMINOACRYLONITRILE

Abstract— The absorption spectral and photochemical properties of β-aminoacrylonitrile (AAN), β-aminocrotonitrile (ACN) and three other enaminonitriles have been studied. The synthesis and identification of cis -β-aminoacrylonitrile are also included. Each enaminonitrile has one intense absorption band (1–2 × 10⁴M^-1cm^-1) in the 254–273 nm region. Photoisomerization and photocyclization to imidazoles are observed. Imidazole formation is quite strongly inhibited by oxygen and the presence of oxygen can cause wavelength dependent photochemistry, other reactions and destruction of the reactant. The quantum yield of formation of imidazoles is low (<10^-4) for β-aminoacrylonitrile and β-aminocrotonitrile and photoisomerization dominates in those four cases where it can occur. Imidazole formation from a dimethylamino compound proves that the presence of H atoms on the amino group is not a prerequisite for photocyclization.     

THE WAVELENGTH DEPENDENCE OF HERPES SIMPLEX VIRUS INACTIVATION BY ULTRAVIOLET RADIATION

The effect of different wavelengths of ultraviolet (UV) radiation on Herpes simplex virus when assayed on mammalian cells (measured by plaque forming ability) was investigated. The wavelength dependence of viral inactivation was obtained for 11 different wavelengths over the region 238–297 nm. The resulting action spectrum does not closely follow the absorption spectrum of either nucleic acid or protein. The most effective wavelengths for viral inactivation are over the region 260–280 nm.     

ORIENTATION OF SHORT WAVELENGTH AND LONG WAVELENGTH PROTOCHLOROPHYLL SPECIES IN GREENING CHLOROPLASTS

Abstract— The orientation of protochlorophyll and Chi species with respect to the plane of thylakoid membranes was studied by measuring the fluorescence polarization ratio in magnetically oriented chloroplasts isolated from greening maize leaves and cucumber cotyledons. With viewing direction parallel to the plane of the photosynthetic membranes, in the spectral region of 620–660 nm, fluorescence polarization ratios of 1.0 were observed, whereas at longer wavelengths the fluorescence polarization ratios were much higher, and similar to that of fully green chloroplasts. The same result was obtained with chloroplasts isolated from leaves fed by δ-amino levulinic acid. These data indicate that the emitting oscillators of the short and long wavelength protochlorophyll species are oriented at random with respect to the plane of thylakoid membranes. Isotropy of the protochlorophyll species is discussed in terms of isotropic structures containing Chi precursors.     

EFFECT OF IONIZING RADIATION UPON TOTAL DIFFUSE SPECTRAL REFLECTANCE OF ULTRAVIOLET LIGHT BY SKIN

Abstract— Irradiation of guinea-pig skin with X rays and beta particles resulted in decreased total diffuse reflectance (DSR) of 330–400 nm light. Qualitatively, this response resembled that seen after irradiation of the skin of normal guinea-pigs with ultraviolet (UV) radiation of wavelength shorter than 300 nm or that of photosensitized guinea pigs with UV wavelengths longer than 300 nm. We postulate that the transformations which depress the DSR result from energy-transfer processes, independent of the class of radiation. Moreover, they are intimately related to subsequent changes in vascular permeabilities (delayed erythema) which occur after the same radiation exposures that lower the 330–400 nm DSR of skin surfaces.     

分光光度计波长校准用低压汞灯的研制

基于辉光放电原理,采用小功率点光源及高频开关电源设计分光光度计波长校准用WSHg-B型低压汞灯,并提出汞灯辐射光谱波长不确定度的分析方法。实验结果表明,WSHg-B型低压汞灯在200～700nm波长范围内,具有分布均匀的线光谱,相对强度稳定,适用于各类通用紫外可见分光光度计的波长校准,还可用于分辨率及光谱带宽的测试。     

ISOMERIZATION OF THE RETINYLIDENE CHROMOPHORE OF BACTERIORHODOPSIN IN LIGHT ADAPTATION: INTRINSIC ISOMERIZATION OF THE CHROMOPHORE AND ITS CONTROL BY THE APO-PROTEIN

Abstract— The dependence of the isomeric configuration of the retinylidene chromophore of bacteriorhodopsin on the pH value and on the wavelength of irradiation (in a photostationary state) were examined by high performance liquid chromatographic analyses of extracted retinal. The process of isomerization of the chromophore during light adaptation was also traced. More than 93% of all- trans and less than 5% of 13- cis retinal were extracted in the photostationary state for irradiation at 560 nm in the pH region of5–9 as well as for irradiation in the wavelength region of 400–650 nm at pH 7. Comparison of the above photostationary state composition with that of protonated n -butylamine Schiff base of retinal indicates that strong constraint is applied to the chromophore by the apo-protein. The constraint can be changed at low or high pH by a partial denaturation or transition of the apo-protein, which results in the generation of 11- cis retinal in the extract. At higher photon density, the isomerization process of the chromophore during light adaptation at pH 7 was characterized, as extracted isomeric retinal, by (1) the initial decrease in 13- cis and increase in all- trans , (2) a subsequent, transient toward the above photostationary state composition. The results are discussed in terms of both the photoisomerization pattern inherent in the retinylidene chromophore and the control by the apo-protein.     

ULTRAVIOLET ENHANCED REACTIVATION OF HERPES SIMPLEX VIRUS INACTIVATED BY DIFFERENT WAVELENGTHS OF UV RADIATION

The degree of ultraviolet enhanced reactivation (UVR) exhibited by mammalian cells when infected with Herpes simplex virus inactivated by different wavelengths of far ultraviolet (UV) radiation was measured. A wavelength dependence for this effect is presented over the wavelength region 238–297 nm. Within the limits of the deviations obtained, the degree of UVR exhibited is similar at each wavelength. This suggests that virus irradiated with different wavelengths of UV radiation received the same type of damage or that cells repaired the different types of viral damage with the same efficiency.     

DECONVOLUTION OF THE RED P700 DIFFERENCE SPECTRUM BASED ON A SET OF THREE GAUSSIAN COMPONENTS: FURTHER EVIDENCE FROM LITERATURE SPECTRA

Abstract Literature data on the light induced difference spectrum of the photosynthetic reaction centre complex P700 were analysed in the spectral region from 670-700 nm. In accordance to our previous Gaussian deconvolution of the flash induced difference spectrum and the linear dichroism spectrum of photosystem I particles from green plants, we present here fits of three representative difference spectra that were recorded at room temperature and at low temperature conditions, respectively. These fits are generated by using the same set of only three Gaussian components that we specified previously: (1) a disappearing wide band around 695 nm representing the absorption of the reduced special-pair of chlorophyll- a ; (2) an appearing narrower band at slightly shorter wavelength (In agreement with our previous results, this band shows half the oscillatory strength of the former band. It is therefore attributed to the non-oxidized chlorophyll- a in the special pair); and (3) a bathochromic bandshift centered around 688 nm, which indicates the local electrochromic response of chlorophyll-a antennae molecule(s) close to the site of the primary donor. Among the reports by several authors we attribute the variation of the difference spectra of P700 in the region from 670-720 nm mainly to a variation in the magnitude of the third component, the local electrochromic one. We can also account for the peculiar shape of the low temperature spectra, mainly by alteration of the extent of the electrochromic component. It seems reasonable that the electrochromic component reacts most sensitively against structural changes of the reaction centre protein complex (brought forth by different degrees of depletion from antennae or by variation of the temperature).     

LINEAR DICHROISM STUDY OF METALLOPORPHYRIN TRANSITION MOMENTS IN VIEW OF RADIATIONLESS INTERACTIONS WITH TRYPTOPHAN IN HEMOPROTEINS

We measured the linear dichroism of several metalloporphyrins embedded in stretched polyvinyl alcohol (PVA) films to estimate the orientation of the absorption transition moments, which in hemoproteins are relevant to the radiationless energy transfer between tryptophan and heme. The metalloporphyrins were derivatives of protoporphyrin IX (PPIX), namely Fe³⁺-PPIX (ferric-heme) and Fe²⁺CO-PPIX (CO-heme), Mg-PPIX (Mg-heme) and Zn-PPIX (Zn-heme). Measurements were conducted between 300 and 700 nm. In all cases the linear dichroism was wavelength dependent, indicating the presence of several transition moments with different orientations. We focused our attention on the near-UV (300–380 nm) and Soret (380450 nm) absorption bands. Deconvolution in terms of Gaussian components gave three components between 380 and 450 nm and only one in the 300–380 nm region. Deconvolution of the near-UV and Soret spectra of oxy-, deoxy- and carbonmonoxyhemoglobin gave very similar results, suggesting a very similar orientation of the various transition moments in the free and protein-embedded hemes. It should be stressed that the single 300–380 nm band is the only one responsible for the overlap integral that regulates the energy transfer from tryptophan to heme in hemoproteins (Gryczynski et al., Biophys. J . 63, 648–653, 1992). The dichroism of this single band indicated that its transition moment is oriented at about 60 from the α-γ meso-axis of the heme moiety. We conclude that the heme should be considered a linear oscillator when it acts as acceptor of energy transfer from tryptophans.     

THE FUNCTION OF PHYTOCHROME IN THE NATURAL ENVIRONMENT—II. THE INFLUENCE OF VEGETATION CANOPIES ON THE SPECTRAL ENERGY DISTRIBUTION OF NATURAL DAYLIGHT

Abstract— Qualitative changes in the spectral energy distribution (SED) of natural daylight within the 400–800 nm wavelength band have been followed within a wheat canopy. Selective attenuation of radiation by the canopy caused large decreases in the blue and red wavebands and, to a lesser extent, the green; far-red was largely transmitted. This resulted in a decrease in the red:far-red ratio from the values observed in natural daylight.
The spectral energy distribution below the canopy was found to be partially dependent on solar elevation and sky condition; it was also dependent on the age, height, leaf area index and chlorophyll content of the crop. The possible ecological significance of the wide variety of spectral energy distributions which have been observed are discussed in relation to phytochrome function.