WAVELENGTH DEPENDENCE (150–290 nm) OF THE FORMATION OF THE CYCLOBUTANE DIMER AND THE (6–4) PHOTOPRODUCT OF THYMINE

The action cross sections for the formation of the cyclobutane dimer and the (6-4) photoproduct of thymine as well as the absorption cross sections of thymine were determined in the wavelength region between 150 and 290 nm. Thymine films sublimed on glass plates were irradiated by monochromatic photons in a vacuum; the induced photoproducts were quantitatively analyzed by high-performance liquid chromatography (HPLC). Under our conditions, two major peaks appeared on the HPLC chromatograms of irradiated samples. The two peaks were identified as being the cis-syn cyclobutane dimer and the (6-4) photoproduct, based on their HPLC retention times, absorption spectra in the effluent, and photochemical reactivity. The fractions of the two photoproducts increased linearly with the fluence at low fluences over the entire wavelength range. Their action cross sections were determined by the slopes of the linear fluence response curve at 10 nm intervals between 150 and 290 nm. The two action spectra showed a similar wavelength dependence and had a maximum at 270 nm as well as two minor peaks at 180 and 220 nm, at which wavelengths the peaks of the absorption spectrum of thymine sublimed on a CaF2 crystal plate appeared. The quantum yields had relatively constant values of around 0.008 for the dimer and 0.013 for the (6-4) photoproduct above 200 nm, decreasing to 0.003 and 0.006, respectively, at 150 nm as the wavelength became shorter.     

CYCLOBUTANE DIMERS AND (6-4)PHOTOPRODUCTS IN HUMAN CELLS ARE MENDED WITH THE SAME PATCH SIZES

The size of excision repair patches corresponding to excision of (6-4) pyrimidine-pyrimidone photoproducts and (5-5, 6-6) cyclobutane dimers have been independently determined by using bromodeoxyuridine substitution and density increases in isopycnic gradients of small DNA fragments. The two classes of photoproducts were distinguished by using (a) a xeroderma pigmentosum (XP) revertant cell line that excises (6-4) photoproducts normally, but does not excise cyclobutane dimers from bulk DNA or from an actively transcribed sequence; (b) an XP cell line containing the denV gene of bacteriophage T4, which repairs only cyclobutane dimers by a unique glycosylase mechanism, and (c) normal cells analyzed during time intervals in which cyclobutane dimer repair is the main repair process in action. The patch sizes for the two lesions were similar under all conditions and were estimated to be approximately 30-40 bases. These values are slightly large than corresponding estimates for Escherichia coli and Saccharomyces cerevisiae but close to estimates from in vitro experiments with human cell extracts. The size of 30 bases may consequently be very close to the actual distance between cleavage sites made on either side of a photoproduct during repair.     

CONFORMATIONS OF DEOXYDODECANUCLEOTIDES WITH PYRIMIDINE (6-4) PYRIMIDONE PHOTOADDUCTS

Abstract— We have carried out molecular mechanical simulations of dodecanucleotide d(CGCGAAXYCGCG).d(CGCGX'Y'TTCGCG) with XY being CC, TC, TT and CT and X'Y'being their corresponding base paired dinucleotides on the complementary strand. Simulations were also carried out with the corresponding pyrimidine (6-4)-pyrimidone photoadducts incorporated in these dodecanucleotides. As in the case of the cyclobutane dimer incorporated dodecanucleotide structures (Rao et al., 1984), those regions of the DNA modified by6–4 pyrimidine adducts are found to undergo little conformational changes except in the dimer region. The conformational characteristics of the6–4 pyrimidine adduct incorporated structures seem to be influenced by the nature of the base at the 3' end of the dimer. Specifically, favorable hydrogen bonding interactions between the 5' end base and its preceding phosphate group are present in structures which have cytosine at the 3' end of the photodimer. The energetics of these structures relative to those without incorporated dimers have been discussed and the results have been analysed in the light of the currently prevalent ideas on the role of the6–4 photoadducts in mutagenesis in various organisms.     

THE USE OF SPECIFIC RADIOIMMUNOASSAYS TO DETERMINE ACTION SPECTRA FOR THE PHOTOLYSIS OF (6-4) PHOTOPRODUCTS

Abstract. A radioimmunoassay (RIA) was developed which specifically detects a photoproduct produced by the near-UV photolysis of pyrimidine(6-4)pyrimidone photoproducts. This assay was used in conjunction with a previously characterized RIA which specifically detects (6-4) photoproducts to determine the relative efficiency of wavelengths between 265 and 435 nm for photolysing these lesions. The rate of loss of antibody-binding sites associated with (6-4) photoproducts correlates with the production of those associated with its photolysis product. Action spectra for both the loss of (6-4) photoproducts and the induction of the photolysis product parallel the absorption spectrum of the (6-4) photoproduct.     

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.     

IRRADIATION OF CIRCULAR DNA WITH 254 nm RADIATION OR SENSITIZATION IN THE PRESENCE OF Ag+ EVIDENCE FOR UNWINDING BY PHOTOPRODUCTS OTHER THAN PYRIMIDINE DIMERS

Abstract— Structural alterations of DNA irradiated with UV light were analyzed by the agarose gel technique. Relaxed, circular pAT 153 DNA molecules were sensitized by broad band radiation with a maximum at 313 nm in the presence of silver ions or irradiated with 254 nm light in buffer only. In both cases the electrophoretic mobility of DNA topoisomers was altered as a linear function of UV exposure. For DNA irradiated in the sensitized reaction the unwinding angle per site sensitive to Micrococcus luteus pyrimidine dimer endonuclease was found tobe–11.4°. This value is significantly smaller thanthe–14.3° already known for DNA topoisomers irradiated with 254 nm light. The irradiated DNAs were a very good substrate for the Escherichia coli photoreactivating enzyme (PRE). However, the photoenzymic removal of all sites sensitive to the endonuclease specific for pyrimidine dimers was not coupled to a full restoration of the original electrophoretic mobility. Thirty and 23% of the unwinding were still present in the photoreactivated topoisomers and the unwinding angles per pyrimidine dimer were then recalculatedas–10.1°and–8.7° for DNAs irradiated with 254 nm and sensitized, respectively. The limited difference between these two values could result from the different base composition of the pyrimidine dimers generated in the conditions of irradiation used. These results show that the tertiary structure of DNA is measureably altered by UV photodamages other than pyrimidine dimers.     

CHARACTERIZATION OF THE (6-4) PHOTOPRODUCT OF 2'-DEOXYCYTIDYLYL-(3'->5')-THYMIDINE AND OF ITS DEWAR VALENCE ISOMER

Far-UV irradiation of dCpT in aqueous solution was found to generate the corresponding pyrimidine (6-4) pyrimidone photoadduct and the related Dewar valence isomer. The two photoproducts of dCpT were found to undergo deamination in aqueous solution, giving rise to the corresponding dUpT derivatives at a relatively slow rate. It was also shown that the Dewar isomer is much more alkali-labile than its (6-4) precursor.     

4-(6-甲氧基-8-喹啉偶氮)-间苯二酚与Ni(Ⅱ)的显色反应

研究了4-(6-甲氧基-8-喹啉偶氮)-间苯二酚(MQAR)与Ni(Ⅱ)的显色反应。确立了Ni(Ⅱ)与MQAR显色反应的条件,配合物的最大吸收波长为570nm,对比度为98nm,镍含量在0.2-1.6mg·L-1范围内服从比耳定律,表观摩尔吸光系数为2.63×104L·mol-1·cm-1,表观稳定常数为1.26×10(10),Sandell灵敏度为2.17×10-3μg·cm-2。用于人发和血清中镍的测定,取得了满意的结果。     

WAVELENGTH DEPENDENT FORMATION OF THYMINE DIMERS AND (6-4)PHOTOPRODUCTS IN DNA BY MONOCHROMATIC ULTRAVIOLET LIGHT RANGING FROM 150 TO 365 nm

We investigated the wavelength dependence of cyclobutane thymine dimer and (6-4)photoproduct induction by monochromatic UV in the region extending from 150 to 365 nm, using an enzyme-linked immunosorbent assay with two monoclonal antibodies. Calf thymus DNA solution was irradiated with 254-365 nm monochromatic UV from a spectrograph, or with 220-300 nm monochromatic UV from synchrotron radiation. Thymine dimers and (6-4)photoproducts were fluence-dependently induced by every UV below 220 nm extending to 150 nm under dry condition. We detected the efficient formation of both types of damage in the shorter UV region, as well as at 260 nm, which had been believed to be the most efficient wavelength for the formation of UV lesions. The action spectra for the induction of thymine dimers and (6-4)photoproducts were similar from 180 to 300 nm, whereas the action spectrum values for thymine dimer induction were about 9- and 1.4-fold or more higher than the values for (6-4)photoproduct induction below 160 nm and above 313 nm, respectively.     

非MAO的茂钛均相催化体系催化苯乙烯间规聚合——[Cp~*TiMe_3]/[Ph_3C]~+[B(C_6F_5)_4]~-催化体系

非ＭＡＯ的茂钛均相催化体系催化苯乙烯间规聚合———［ＣｐＴｉＭｅ３］／［Ｐｈ３Ｃ］＋［Ｂ（Ｃ６Ｆ５）４］－催化体系许光学林尚安（中山大学高分子研究所广州５１０２７５）关键词茂钛络合物，茂金属催化剂，苯乙烯，间规聚苯乙烯间规聚苯乙烯（ｓＰＳ）由于具...     

AN UNUSUAL ADDITION AND RING-CLOSURE REACTION OF 1-(2-BROMOETHYL)-2,3-DIHYDRO- 3-PROPYL-1,3,2-BENZO-DIAZAPHOSPHORIN-4(1H)-ONE 2-OXIDE WITH CARBON DISULFIDE FOR A NEW AND CONVENIENT SYNTHESIS OF THE FUSED PHOSPHORUS HETEROCYCLIC COMPOUND

ABSTRACT

The reaction of 1-(2-bromoethyl)-2,3-dihydro-3-propyl-1,3,2-benzodiazaphosphorin-4(1H)-one 2-oxide with carbon disulfide takes an alternative pathway in the use of different bases. The sodium hydride mediated reaction leads to the formation of the tricyclic fused 1,2,3,4,4a,4b,5,6-octahydro-6-oxo-5-propyl-4-thia-3,4b,4a-thiazphosphaphenanthridine 4a-oxide via addition of H-P bond across the double bond of carbon disulfide followed by intramolecular cyclization. In the presence of triethylamine, refluxing a mixture of 1-(2-bromoethyl)-2,3-dihydro-3-propyl-1,3,2-benzodiazaphosphorin-4(1H)-one 2-oxide with carbon disulfide in benzene takes an unusual course with formation in excellent yield of the first example of fused phosphorus heterocyclic 4-[1′-(β-bromoethyl)-4′-oxo- 3′-propyl-1′,2′,3′,4′-tetrahydro-1,3,2-benzodiazaphosphorin-2′- sulfide]-1,2,3,4,4a,4b,5,6-octahydro-6-oxo-5-propyl-3,4b, 4a-thiazphosphaphenanthridine 4a,2′-dioxide, which was confirmed by spectroscopic methods, microanalyses and single crystal X-ray structure determination.     

STUDIES ON ORGANOPHOSPHORUS COMPOUNDS. PART VI.† THE REACTION OF ALKOXIDES WITH 2,4-BIS(4-METHOXYPHENYL)-1,3,2,4-DITHIADIPHOSPHETANE 2,4-DISULFIDE (LR). A NEW APPROACH FOR THIO-INEZIN

Abstract

Sodium alkoxide, a hard nucleophile, reacts with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (LR) on phosphorus to give O-alkyl S-sodium-(4-methoxyphenyl) phosphonothiolothionate 5 as an intermediate. Compound 5 reacts with benzyl (or benzoyl) chloride to give good yields of O-alkyl S-benzyl (benzoyl) (4-methoxy-phenyl)phosphonothiolothionate (6a–e).