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Keane PM Wojdyla M Doorley GW Kelly JM Clark IP Parker AW Greetham GM Towrie M Magno LM Quinn SJ 《Physical chemistry chemical physics : PCCP》2012,14(18):6307-6311
The decay pathways of UV-excited cytosine polymers are investigated using picosecond time-resolved infrared spectroscopy. Similar yields of a non-emissive (1)nπ* state are found in the single-stranded dC(30) polymer as in the dCMP monomer, but with a longer lifetime in the polymer (80 ps vs. 39 ps). A longer lifetime is also found in the d(CpC) dinucleotide. No evidence of excimer states is observed, suggesting that localised (1)nπ* excited states are the most significant intermediates present on the picosecond timescale. 相似文献
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Robert L. Hall ‡ Peter F. Doorley ¶ Robert A. Niederman† 《Photochemistry and photobiology》1978,28(2):273-276
Abstract— Rhodopseudomonas sphaeroides NCIB 8253 chromatophores were treated with trypsin and pronase to determine which of the three reaction center subunits was exposed at the outer surface and susceptible to digestion. Trypsin (37°C, 60min) produced no detectable digestion of any subunit, based on SDS polyacrylamide gel electrophoresis analysis. Pronase (37°C, 60min) digested the H (28 kdalton) subunit but left the M (22 kdalton) and L (19 kdalton) subunits intact. We conclude that the H subunit is significantly exposed at the outer chromatophore surface but that the M and L subunits are probably not externally exposed. Chromatophores which had been pronase-treated were fully photochemically active, as measured by light-induced carotenoid bandshift at 522 nm. The H subunit is apparently unnecessary for primary photochemistry in situ. 相似文献
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Keane PM Wojdyla M Doorley GW Watson GW Clark IP Greetham GM Parker AW Towrie M Kelly JM Quinn SJ 《Journal of the American Chemical Society》2011,133(12):4212-4215
The role of N1-substitution in controlling the deactivation processes in photoexcited cytosine derivatives has been explored using picosecond time-resolved IR spectroscopy. The simplest N1-substituted derivative, 1-methylcytosine, exhibits relaxation dynamics similar to the cytosine nucleobase and distinct from the biologically relevant nucleotide and nucleoside analogues, which have longer-lived excited-state intermediates. It is suggested that this is the case because the sugar group either facilitates access to the long-lived (1)n(O)π* state or retards its crossover to the ground state. 相似文献
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Quinn S Doorley GW Watson GW Cowan AJ George MW Parker AW Ronayne KL Towrie M Kelly JM 《Chemical communications (Cambridge, England)》2007,(21):2130-2132
A strong infrared band at 1574 cm(-1) is observed following 267 nm excitation of 2'-deoxycytidine (tau = 37 +/- 4 ps) or 2'-deoxycytidine 5'-monophosphate (tau = 33 +/- 4 ps); this band is provisionally attributed to an 1n(N)pi* state and is absent for cytosine. 相似文献
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Cellular binding of cationic nanoparticles in the presence of serum proteins was probed with two-colour fluorescence microscopy. Cationic nanoparticles associate with serum proteins in solution and bind to the cell surface as a single anionic complex. Displacement of serum proteins from the nanoparticles was found to be protein dependent. 相似文献
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Elias B Creely C Doorley GW Feeney MM Moucheron C Kirsch-DeMesmaeker A Dyer J Grills DC George MW Matousek P Parker AW Towrie M Kelly JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(1):369-375
Transient species formed by photoexcitation (400 nm) of [Ru(dppz)(tap)2]2+ (1) (dppz = dipyrido[3,2-a:2',3'-c]phenazine; tap=1,4,5,8-tetraazaphenanthrene) in aqueous solution and when intercalated into a double-stranded synthetic polynucleotide, [poly(dG-dC)]2, have been observed on a picosecond timescale by both visible transient absorption (allowing monitoring of the metal complex intermediates) and transient infrared (IR) absorption spectroscopy (allowing direct study of the DNA nucleobases). By contrast with its behavior when free in aqueous solution, excitation of 1 when bound to [poly(dG-dC)]2 causes a strong increase in absorbance at 515 nm due to formation of the reduced complex [Ru(dppz)(tap)2]+ (rate constant=(2.0+/-0.2) x 10(9) s(-1)). The subsequent reformation of 1 proceeds with a rate constant of (1.1+/-0.2) x 10(8) s(-1). When the process is carried out in D2O, the rates of formation and removal of [Ru(dppz)(tap)2]+ are reduced (rate constants (1.5+/-0.3) x 10(9) and (0.7+/-0.2) x 10(8) s(-1) respectively) consistent with proton-coupled electron transfer processes. Picosecond transient IR measurements in the 1540-1720 cm(-1) region in D2O solution confirm that the reduction of 1 intercalated into [poly(dG-dC)]2 is accompanied by bleaching of IR ground-state bands of guanine (1690 cm(-1)) and cytosine (1656 cm(-1)), each with similar rate constants. 相似文献
7.
McGovern DA Quinn S Doorley GW Whelan AM Ronayne KL Towrie M Parker AW Kelly JM 《Chemical communications (Cambridge, England)》2007,(48):5158-5160
The photophysical properties of stacked G-tetrads in diverse systems, including concentrated solutions of 5'-guanosine monophosphate (5'-GMP), polyguanylic acid (poly(G)) and the G-rich oligodeoxynucleotide sequence characteristic of human telomeric DNA, are probed by ps-TRIR and compared to those of the monomeric 5'-GMP. 相似文献
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Two-colour fluorescence microscopy was used to track the cellular internalization of nanoparticles exposed to extracellular serum proteins. Single particle tracking revealed that nanoparticles and serum proteins are internalized and transported through the cell as a single complex. This study demonstrates the importance of nanoparticle-protein interactions in cellular applications. 相似文献
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