DIFFUSE SPECTRAL REFLECTANCE MODIFICATION OF SKIN BY U.V. IRRADIATION

Abstract— Irradiation of guinea pig skin in vivo with light shorter than 300 nm produced a significant decrease in 330–400 nm reflectance. A similar decrease in reflectance was seen by irradiation of excised guinea pig and human skin. Chemical or physical vasodilation had no effect on the 240–400 nm reflectance. Irradiation of guinea pig skin in vivo with light longer than 300 nm produced no change in 330–400 nm reflectance unless photosensitized with 8-MOP. U.V. irradiation of skin (in the presence of suitable endogenous or exogenous photo-sensitizers) may result in the formation of new products that effectively absorb 330–400 nm photons.     

A COMPARISON OF LIGHT-TRIGGERED SPECTRAL CHANGES IN RHODOPSIN AND ISORHODOPSIN

Abstract— This report describes spectral changes associated with the transformation of metarhodopsin I to metarhodopsin II following light excitation of isorhodopsin and rhodopsin. Irradiated isorhodopsin gives rise to an equilibrium mixture of metarhodopsin I and metarhodopsin II which at 2°C and pH 6.8 favors the former. Isorhodopsin and rhodopsin are converted to metarhodopsin II via metarhodopsin I at very similar rates and activation parameters for the conversions are essentially identical. It is concluded that the initial cis to trans isomerization erases all differences in the two pigments.     

同系规律的联系和比较

本文由同系能级线性规律E=a+b(2k-1)/ksin(kπ/(2N+1))推导出了文献[6]提出的同系递变规律E=a+b/N,在推导的过程中得到一个新的比同系递变规律好的同系函数E=a+b((2k-1)/(N+1/2)).用文献[2][9]发表的96组光电子能谱数据和文献[1]发表的159组电子光谱数据对最近提出的五种同系规律进行了检验、比较,我们认为同系能级线性规律比较好。     

DEHYDRATION OF U.V. IRRADIATED URIDINE AND ITS DERIVATIVES

Abstract— Ultraviolet irradiation of uridine, oligonucleotides and long chain Poly U produces a variety of photoproducts including a hydrated base arising from the addition of water to the 5,6 double bond. Both the hydration and dehydration reactions in a nucleotide are sensitive to the position of the phosphate linkage. The 5' mononucleotide is less easily hydrated than the 3'. Conversely, the dehydration process in the nucleoside and the nucleotides is most rapid for uridine and decreases progressively in rate as a phosphate is added to the 2', 5' or 3' position respectively. In the compound UpU the dehydration is a two component reaction with the two dehydration rates similar to those of 5' and 3' mononucleotides respectively. In higher order oligonucleotides the dehydration rate is slower than any of the rates for 5' and 3' monophosphates or 3', 5' diphosphates. The dehydration rate decreases rapidly for oligonucleotides up to chain lengths of 6 or 8 and then decreases at a diminishing rate. Long chain Poly U (7gt; 200 nucleotides) dehydrates at approximately 1/5 the rate of Up. In addition the initial alkaline treatment to dehydrate irradiated Poly U may result in chain breakage but this effect is not seen in subsequent cycles of irradiation and dehydration. The chain length effect on dehydration rate is only slightly decreased by the presence of 7M urea in the dehydration mixture. Quantitative data is presented on the effect of ternpcrature, and pH on the rate constant for dehydration of Up and its derivatives.     

COMPARISON OF SURVIVAL OF A U.V.-IRRADIATED URACIL-REQUIRING STRAIN OF ESCHERICHIA COLI B IN THE PRESENCE OF CHLORAMPHENICOL AND IN THE ABSENCE OF THE ESSENTIAL METABOLITE

Abstract— Restoration of viability of E. coli B U- after a total dose of 900 ergs/mm2 U.V. in the presence of chloramphenicol and in the absence of uracil was studied. Both treatments result in the recovery of the same fraction of the irradiated bacterial population. There is no additive effect if both treatments are applied to the same irradiated culture.     

高纯甲烷纯气体中的杂质分析——CCQM K66国际比对

针对国际CCQM组织的K66高纯甲烷纯度分析关键比对,建立高纯甲烷中杂质的分析和定量方法.根据标准物质的制备过程和对稀释气中杂质的分析结果,对比对过程中的测量不确定度进行了评定.比对样品甲烷中氩气、氮气、乙烷和二氧化碳含量的测定结果分别为2.005、3.601、1.477、2.615 μmol/mol,相对扩展不确定度(k=2)分别为1.5%、4.5%、1.5%、1.6%.     

EFFECTS OF SENSITIZED AND UNSENSITIZED LONGWAVE U.V.-IRRADIATION ON THE SOLUTION PROPERTIES OF DNA

Abstract— Two types of photoreactions occur in DNA irradiated in aqueous systems with longwave u.v.-light (Λ > 295 nm), namely, (a) thymine dimerization, and (b) single- and double-strand breakage of the sugar phosphate backbone; these two reactions are unrelated. The presence of acetophenone as a photosensitizer caused an increase in dimerization by a factor of 16, and an increase in single-strand breaks by a factor of 4. The number of thymine dimers per single-strand break is about 100 in the sensitized and 25 in the unsensitized reaction. The alteration of the radius of gyration of DNA molecules is that expected by the degradation observed. At the same time the change in hyperchromicity is very small. Therefore as far as can be detected by these methods of investigation the gross conformation of the DNA double helix is stable against thymine dimerization.     

THE U.V. PHOTOCHEMISTRY OF CYTIDYLIC ACID

Abstract The ultraviolet (u.v.) irradiation of the 3' isomer of cytidylic acid (Cp) produces the hydrate (Cp*) with water added across the 5–6 double bond. The yield of this photo-product has been measured by, (a) separating the photoproduct by electrophoresis and (b) by observing the loss in absorbance. When corrections are made for reversal of the hydrate during the experiment, both methods gave the same result. Cross sections and quantum yields for the production of the hydrate were measured over the wavelength range 220 to 290 nm and over a pH range from 1 to 10. The quantum yield is markedly dependent on pH being higher by a factor of 6 to 10 for the neutral form. We have also demonstrated the existence of a very short lived photoproduct (half life 8–9 min) in both Cp3' and Cp5': The nature of this short lived product is not known.     

STUDIES OF THE ROLE OF THE COAT PROTEIN IN THE U.V. PHOTOINACTIVATION OF U(1) AND U(2) STRAINS OF TMV*

Abstract— Two properties of the u.v. inactivation process in the u.v. sensitive U(2) strain have been investigated: (1) The increased binding of protein to RNA induced by irradiation of the virus at 254 nm; (2) The action spectrum for u.v. inactivation of U(2) between 250 nm and 285 nm. The extent of the u.v. induced binding of protein to RNA is similar to that previously found in the resistant U(1) strain, thereby eliminating the possibility that the capacity for this binding phenomenon bears any correlation to the difference in u.v. sensitivities of these two viruses at 254 nm. The results indicate that the radiation induced interaction of protein and RNA in U(1) and U(2) are probably similar. The action spectrum for U(2) resembles the absorption spectrum of the RNA between 250 nm and 285 nm implicating the RNA as the primary absorber leading to inactivation of the virus in this region of the spectrum. Quantum yields calculated for U(2) virus and free TMV-RNA irradiated at 254 nm reveal that the irradiated free RNA may be as much as 1–4 times more sensitive to inactivation at this wavelength than RNA in the intact virus. It is concluded that the coat protein of U(2) probably offers some protection to the enclosed RNA against u.v. damage at 254 nm, therefore, the difference in u.v. sensitivity between U(1) and U(2) TMV at this wavelength is a consequence of a difference in the degree of protection offered by the respective coat proteins to the enclosed RNA.     

COMPARISON OF PHAGE T4 denV ENDONUCLEASE V AND M. Luteus UV-DNA ENDONUCLEASE BY SEROLOGY AND DNA HYBRIDIZATION

Abstract Antibodies were raised in rabbits against purified endonuclease V, the product of the bacteriophage T4 denV gene, which incises DNA at the site of UV-induced pyrimidine dimers. These antibodies cross-reacted with the purified UV-DNA endonuclease from M. luteus in both enzyme-linked immunosorbent assay and Western assays. However, no sequence similarity was detected between the denV gene and M. luteus DNA by hybridization. The two endonucleaes are remarkably similar in enzymatic activity, and their antigenic similarities have been preserved despite differences in their DNA sequences.     

SPECTRAL AND PHOTOCHEMICAL PROPERTIES OF CURCUMIN

Curcumin, bis(4-hydroxy-3-methoxyphenyl)-l,6-heptadiene-3,5-dione, is a natural yellow-orange dye derived from the rhizome of Curcuma longa, an East Indian plant. In order to understand the photobiology of curcumin better we have studied the spectral and photochemical properties of both curcumin and 4-(4-hydroxy-3-methoxy-phenyl)-3-buten-2-one (hC, half curcumin) in different solvents. In toluene, the absorption spectrum of curcumin contains some structure, which disappears in more polar solvents, e.g. ethanol, acetonitrile. Curcumin fluorescence is a broad band in acetonitrile (λ_max= 524 nm), ethanol (λ_max= 549 nm) or micellar solution (λ_max= 557 nm) but has some structure in toluene (λ_max= 460, 488 nm). The fluorescence quantum yield of curcumin is low in sodium dodecyl sulfate (SDS) solution (φ= 0.011) but higher in acetonitrile (φ= 0.104). Curcumin produced singlet oxygen upon irradiation (φ > 400 nm) in toluene or acetonitrile (Φ= 0.11 for 50 μM curcumin); in acetonitrile curcumin also quenched ¹O₂ (k_q, = 7 × 10⁶ M^?1 s^?1). Singlet oxygen production was about 10 times lower in alcohols and was hardly detectable when curcumin was solubilized in a D₂O micellar solution of Triton X-100. In SDS micelles containing curcumin no singlet oxygen phosphorescence could be observed. Curcumin photogenerates superoxide in toluene and ethanol, which was detected using the electron paramagnetic resonance/spin-trapping technique with 5,5-dimethyl-pyrroline-.N-oxide as a trapping agent. Unidentified carbon-centered radicals were also detected. These findings indicate that the spectral and photochemical properties of curcumin are strongly influenced by solvent. In biological systems, singlet oxygen, superoxide and products of photodegradation may all participate in curcumin phototoxicity depending on the environment of the dye.     

PROPERTIES OF AN UNUSUAL PHOTOPRODUCT OF U.V. IRRADIATED THYMIDYLYL-THYMIDINE

Abstract— One of the four major photoproducts formed by UV irradiation of TpT in aqueous solution has a number of unusual properties. This compound, which we arbitrarily call TpT⁴, is produced irreversibly from TpT with single-hit kinetics and seems to represent a novel pathway for TpT photolysis different from the conventional cyclobutane ring dimer formation. This communication describes the preparative isolation of TpT⁴ by ion-exchange chromatography on DEAE-cellulose and its UV, fluorescence and IR spectra. TpT⁴ has an absorption maximum at 325 mμ, fluoresces at 405 mμ when excited at 325 mμ, and has an IR spectrum consistent with the assumption that one of the thymine rings has been converted to a pyrimidin-2-one structure. In addition, TpT⁴ appears to have both pyrimidine rings linked together and does not contain a peroxide group as previously supposed. Spectrophotometric titration shows that TpT⁴ has a pKâ of 10.75 and is unstable to prolonged treatment at extreme pH. A model structure consistent with the present data is given. This model contains the glycosidic and phosphodiester bonds intact with a 5-methylpyrimidine-2-one ring and a thymine ring joined in ether linkage at the C₄ positions, with an OH at the C₄ position in the thymine ring.     

光谱实验室的建设和管理

阐述冶金、铸造等行业用于金属成分分析的直读发射光谱仪实验室的建设和管理。从仪器的调研、选型，实验室选址，基础设施设备的准备，仪器的安装、调试、验收、日常分析，实验室管理等几个方面，分别作了介绍。     

聚(苯乙烯-甲基丙烯酸甲酯-砜)的合成及其紫外光降解

本文研究了苯乙烯、甲基丙烯酸甲酯、二氧化硫三元共聚合反应。其产品的特性用元素分析,红外和紫外光谱,NMR,DSC,TG等进行了详细地表征。该产品只有一个玻璃化温度132.5℃,故认为它是一个共聚物——聚(苯乙烯-甲基丙烯酸甲酯-砜),而不是一个均聚物的混合物。将聚(苯乙烯-砜)、聚(苯乙烯-甲基丙烯酸甲酯-砜)、聚甲基丙烯酸甲酯分别加热时,它们分别在252℃、272℃、282℃开始分解。当这些产品的溶液用三支30瓦的低压汞灯辐照时,聚(苯乙烯-砜)溶液的粘度下降速度比聚(苯乙烯-甲基丙烯酸甲酯-砜)快,聚甲基丙烯酸甲酯最慢。     

DECREASED SURVIVAL RESULTING FROM LIQUID-HOLDING OF U.V.-IRRADIATED ESCHERICHIA COLI C AND SCHZZOSACCHAROMYCES POMBE

Abstract— Ultraviolet-irradiated cells of E. coli C and of haploid wild type yeast Schizosac-charomyces pombe , held in buffer at 22°-25°C for various periods of time prior to plating, show a lower survival than those plated immediately after irradiation. This 'negative liquid-holding effect' (NLHE) contrasts 'liquid-holding recovery' (LHR), found in a number of other E. coli strains and in Saccharomyces cerevisiae . NLHE was observed at all u.v. doses tested. The effect is maximal at holding temperatures in the range 25–30°C, it is very small at 5°C and (in E. coli C) at 44°C. NLHE and LHR resemble each other in several respects. In E. coli both effects are inhibitable by the dark repair inhibitors acriflavine, caffeine and potassium cyanide. They do not occur in nutrient broth, and they are much reduced if the irradiated cells were illuminated with photoreactivating light before holding. NLHE in S. pombe shows characteristics similar to those observed in E. coli C . Mutations leading to increased u.v. sensitivity in E. coli C and S. pombe can alter the liquid-holding response so that LHR is observed. Tetrad analysis of crosses between u.v.-sensitive and u.v.-resistant S. pombe strains indicates that a single chromosome region can control both u.v. sensitivity and liquid-holding response. Several possibilities explaining NLHE are discussed. From current knowledge about dark repair processes and from the similarities between NLHE and LHR in E. coli it seems likely that the two effects reflect slight changes in the efficiency of dark repair.