摘要:

Abstract—Direct time‐resolved detection of the luminescence at 1270 nm from ‘singlet oxygen’ was used to estimate the quantum yield of singlet oxygen production (ΦΔ) from a series of related porphyrins in benzene and in D2O. From this and available data the fraction of oxygen quenching interactions leading to singlet oxygen production (SΔ) was derived in most cases. A marked increase in ΦΔvalue was observed for di‐haematoporphyrin ester (DHE) in cetyltrimethyl ammonium bromide/D2O solution in comparison to D2O alone, this increase is attributed to a major structural alteration of DHE on introduction of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09501.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—1,2‐bis(4‐Hydroxyphenyl)‐3,4‐dihydro‐6‐hydroxynaphthalene (6) is a non‐steroidal ligand for the estrogen receptor that displays photofluorogenic properties. It binds to the receptor with an affinity greater than that of estradiol (150%), and it is esentially non‐fluorescent. However, upon brief UV irradiation in protic media it is converted efficiently to an aryl tetraenedione system (8) that is highly fluorescent, but has low affinity for the receptor (0.35%). The aryltetraenedione has a complex electronic spectrum, with absorbance (and fluorescence excitation) bands extending beyond 450 nm. Both the maxima (εmax) and the intensity (φfof the fluorescence emission of the aryl tetraenedione are solvent dependent. The tetraenedione (8) is structurally related to a tetraenedione (13) obtained by photocyclization of diethylstilbestrol(l0); since tetraenedione 13 is essentially non‐fluorescent, it appears that the aryl dienone chromophore in 8 is responsible for its fluorescence. Photolysis of 6 in non‐protic media results in a direct photocyclization‐oxidation to benzodihydrochrysene system 9 that is unstable and has less desirable fluorescent properties. The formation of 8 from 6 in protic media (as contrasted to the formation of 9 in non‐protic media) is thought to arise from the competition that operates on the primary photocyclization product, dihydrophenanthrene (7): In protic media, ketonization proceeds more rapidly than oxidation (aromatization), while in aprotic media, oxidation is more rapid. This photofluorogenic ligand for the estrogen receptor should enable interesting fluorescence binding studies with the estrog

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09502.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The quantum yields of internal conversion (energy loss) of the photoexcited chlorophyllsaandbin ethanol at 24°C have been determined by measuring the quantum yields of the competing radiative (fluorescence) and non‐radiative (intersystem crossing) deactivation processes (which lead to energy storing species) by means of emission and laser‐induced optoacoustic spectroscopy, respectively. The values for internal conversion of chlorophyllaare 10% and 14% in the presence and absence of molecular oxygen, respectively. The corresponding yields for chlorophyllbare negligibly small. The internal conversion in chlorophyllais attributed to vibronic coupling with the substituents of the porphin system, since internal conversion was found to be substantially reduced for unsubstituted Mg‐porphin in ethanol and for chlorophyllawhen dissolved in a viscou

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09503.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The fluorescence of the dansyl group, covalently bound to lysine or tyrosine, was studied in model compounds and enzymes. The fluorescence lifetime of the model compounds strongly depends on solvent polarity and is different for the sulfonamide or sulfate binding type. These compounds rotate as spheres having radii corresponding to the molecules’dimensions. For the enzymes, we found a biexponential total fluorescence decay, because the dansyl groups were either located at two different lysines or bound to oxygen and nitrogen of the same tyrosine, the label always being surrounded by water. Dynamic fluorescence depolarization measurements showed, that the label rotates freely and fast relative to the protein which behaves as a sphere. In a peptide, however, some amino acids rotate together with the la

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09504.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The photoinduction of petite colonies and cell toxicity in non‐growing yeast,Saccharomyces cerevisiae, by 3‐a‐zido‐6‐a‐mino‐10‐m‐ethylacridinium chloride (AAMAC) has been examined. The results presented here indicate that mitochondrial DNA damage in resting yeast which occurs following irradiation of AAMAC‐treated cells for short time periods is probably mediated through a covalent adduct between AAMAC and DNA. Furthermore, the photoreaction which contributes to biological activity is dependent on the presence of oxygen. Pre‐irradiated AAMAC, which no longer exhibited the short‐term photo‐induction of biological effects showed a second biological activity. In this case longer irradiation times, e.g. 30 min, were required to induce petites for resting yeast. Again there was a strong dependence on the presence of oxygen. These results suggest that both processes may be effected through oxygen intermediat

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09505.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The response of a normal human cell strain, IMR‐90 and a line derived from it by SV40 transformation were compared after treatmentin vitrowith hematoporphyrin derivative (HPD) and red light. Transformed cells were inactivated at a significantly higher rate than normal cells when assayed by clonogenic survival. Co‐treatment with HPD and light also induces cellular resistance to enzymatic cleavage by trypsin; transformed cells exhibit a greater resistance than the normal cells to detachment from the growing surface. These data indicate that transformed cells may possess intrinsic characteristics that render them more sensitive than normal cells to HPD‐induced phototoxicity and that the plasma membrane may be the site of differential t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09506.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—Previous work obtained from Chinese hamster V‐79 cells indicated that, immediately following exposure, UV‐induced lesions acted as blocks to elongation of nascent strands, but gradually lost that ability over a 10 h period after exposure to 10 J/m2. The work reported herein attempted to examine possible cell cycle mediated alterations in the recovery of DNA synthesis. Kinetic incorporation of radiolabeled thymidine studies indicated that there may have been a more rapid recovery of DNA synthesis in cells irradiated in G1or G2vscells irradiated in S phase. DNA fiber autoradiograms prepared from synchronous cells indicated that after irradiation in any phase of the cell cycle, the length of newly synthesized DNA was equal to control lengths 1 h after exposure to 5.0 J/m2(or 1 h after entering S phase for cells irradiated in G1or G2). This observed recovery was not solely due to an excision process. No cell cycle mediated difference in the number of dimers induced or removed as a function of cell cycle position was observed. These results appear to be consistent with a continuum of effects, with initiation effects dominating the response at low fluences, gapped synthesis at intermediate fluences and elongation inhibition at high fluences. The fluences at which each event dominates may be cell‐line s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09507.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—The tRNA metabolism which accompanies illumination of growingE. colicells has been examined in conditions that led to growth delay. (i) Thein vivoformation of the 8–13 link was followed by a fluorimetric procedure and revealed pseudo‐first order kinetics very close to those obtainedin vimunder the same illumination conditions. The yield of 8–13 link appears to be quantitative (± 10%). Comparison of these kinetics with the radiochromatographic data of Blanchetotet al. (1984) suggests the transient formation during illumination of a new RNase‐T,‐resistant dinucleotide in tRNA distinct from the 8–13 link. (ii) Evidence is provided that under illumination some tRNA molecules lack one or more bases in a specific position in the sequence, thus yielding discrete fragments after aniline treatment. (iii) During the growth lag, uracil incorporation into nucleic acids occurs at an apparent rate between 4–8% of that normally observed during exponential growth. Evidence is provided however that the pyrimidine ribonucleoside triphosphate pools are strongly perturbed after illumination. Comparison of exogenous [3H]uracil incorporation into two strains proficient or deficient in uracil biosynthesis suggests a derepression of the endogenous path after light treatment. In addition, the UTP‐to‐CTP conversion is inhibited. In spite of preferential incorporation of exogenously labelled uracil in tRNA after illumination, a possible pyrimidine base turnover cannot be proved. These data are compatible with tRNA repair (Blanchetotet al., 1984) involvin

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09508.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—ICR 2A frog and normal human skin fibroblasts were exposed to either 5 J/m2of 254 nm UV or 50 kJ/m2of the Mylar‐filtered solar UV wavelengths produced by a fluorescent sunlamp. Following these approximately equitoxic treatments, cells were incubated in medium containing the DNA synthesis inhibitors hydroxyurea (HU) and 1–β‐D‐arabinofuranosyl cytosine (ara C) for 0–20 min (human fibroblasts) or 0–4 h (frog cells) to accumulate DNA breaks resulting from enzymatic incision during excision repair. It was found that breaks were formed in human cells at about a 200‐f‐old higher rate compared with the ICR 2A cells indicating a relatively low capacity for excision repair in the frog cells. In addition, the rate of DNA break formation in solar UV‐irradiated cells was only one‐third of the level detected in 254 nm‐irradiated cells. This result is consistent with the conclusion that the pathway(s) involved in the repair of solar UV‐induced DNA damages differs from the repair of lesions produced in

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09509.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Abstract—It is shown that glycerol in the bathing solutions of a bacteriorhodopsin model membrane slows the photoresponse. The early stage of the photoresponse is only slightly affected while the later stage is appreciably retarded. These results are in agreement with previous measurements by other investigators on the temporal behavior of the photoreaction cycle in viscous bathing solutions. Data is fit to an equation of the form τ=A ηmexp(Δ/kT) where t is a time constant characterizing the photoresponse, τ is the viscosity of the bathing solution and Δ is the activation energy for the thermally driven p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb09510.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY