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1.
Hartman H 《Speculations in Science and Technology》1984,7(2):77-81
The endosymbiotic hypothesis for the origin of the eukaryotic cell has been applied to the origin of the mitochondria and chloroplasts. However as has been pointed out by Mereschowsky in 1905, it should also be applied to the nucleus as well. If the nucleus, mitochondria and chloroplasts are endosymbionts, then it is likely that the organism that did the engulfing was not a DNA-based organism. In fact, it is useful to postulate that this organism was a primitive RNA-based organism. This hypothesis would explain the preponderance of RNA viruses found in eukaryotic cells. The centriole and basal body do not have a double membrane or DNA. Like all MTOCs (microtubule organising centres), they have a structural or morphic RNA implicated in their formation. This would argue for their origin in the early RNA-based organism rather than in an endosymbiotic event involving bacteria. Finally, the eukaryotic cell uses RNA in ways quite unlike bacteria, thus pointing to a greater emphasis of RNA in both control and structure in the cell. The origin of the eukaryotic cell may tell us why it rather than its prokaryotic relative evolved into the metazoans who are reading this paper. 相似文献
2.
Jesik R Abramov V Antipov Y Baldin B Crittenden R Dauwe L Davis C Denisov S Dyshkant A Dzierba A Glebov V Goldberg H Gribushin A Koreshev V Krider J Krinitsyn A Li R Margulies S Marshall T Martin J Mendez H Petrukhin A Sirotenko V Smith P Solomon J Sulanke T Sulyaev R Vaca F Zieminski A Blusk S Bromberg C Chang P Choudhary B Chung W de Barbaro L Dlugosz W Dunlea J Engels E Fanourakis G Ginther G Hartman K Huston J Kapoor V Lirakis C Lobkowicz F Mani S Mansour J Maul A Miller R Oh B Pothier E 《Physical review letters》1995,74(4):495-498
3.
Balakin V Alexandrov VA Mikhailichenko A Flöttmann K Peters F Voss G Bharadwaj V Halling M Holt JA Buon J Jeanjean J LeDiberder F Lepeltier V Puzo P Heimlinger G Settles R Stierlin U Hayano H Ishihara N Nakayama H Oide K Shintake T Takeuchi Y Yamamoto N Bulos F Burke D Field R Hartman S Helm R Irwin J Iverson R Rokni S Roy G Spence W Tenenbaum P Wagner SR Walz D Williams S 《Physical review letters》1995,74(13):2479-2482
4.
Alverson G Baker WF Ballocchi G Benson R Berg D Blusk S Bromberg C Brown D Carey D Chand T Chandlee C Choudhary BC Chung WH de Barbaro L DeSoi W Dlugosz W Dunlea J Easo S Engels E Faissler W Fanourakis G Ferbel T Garelick D Ginther G Glass G Glaubman M Gutierrez P Hartman K Huston J Johnstone C Kapoor V Kourbanis L Lanaro A Lirakis C Lobkowicz F Lukens P Mani S Maul A Mansour J Miller R Nelson CA Oh BY Orris D Pothier E Prebys E Rajaram BM Roser R Ruddick K Shepard P Shivpuri RK Sinanidis A 《Physical review D: Particles and fields》1993,48(1):5-28
5.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Shuchen Z Zhong Yuanyuan 《Physical review letters》1993,71(21):3417-3420
6.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
7.
8.
John R. Van Camp Tish Young Rosemarie F. Hartman Seth D. Rose 《Photochemistry and photobiology》1987,45(3):365-370
Abstract— Photosensitized pyrimidine dimer splitting characterizes the enzymatic process of DNA repair by the DNA photolyases. Possible pathways for the enzymatic reaction include photoinduced electron transfer to or from the dimer. To study the mechanistic photochemistry of splitting by a sensitizer representative of excited state electron donors, a compound in which an indole is covalently linked to a pyrimidine dimer has been synthesized. This compound allowed the quantitative measurement of the quantum efficiency of dimer splitting to be made without uncertainties resulting from lack of extensive preassociation of the unlinked dimer and sensitizer free in solution. Irradiation of the compound with light at wavelengths absorbed only by the indolyl group (approximately 280 nm) resulted in splitting of the attached dimer. The quantum yield of splitting of the linked system dissolved in N2 0-saturated aqueous solution was found to be 0.04 ± 0.01. The fluorescence typical of indoles was almost totally quenched by the attached dimer. A splitting mechanism in which an electron is efficiently transferred intramolecularly from photoexcited indole to ground state dimer has been formulated. The surprisingly low quantum yield of splitting has been attributed to inefficient splitting of the resulting dimer radical anion. Insights gained from this study have important mechanistic implications for the analogous reaction effected by the DNA photolyases. 相似文献
9.
Petra J. W. Pouwels Robert Kaptein Rosemarie F. Hartman Seth D. Rose 《Photochemistry and photobiology》1995,61(6):575-583
A series of photo-CIDNP (chemically induced dynamic nuclear polarization) experiments were performed on pyrimidine monomers and dimers, using the electron-donor Nα-acetyltryptophan (AcTrp) as a photosensitizer. The CIDNP spectra give evidence for the existence of both the dimer radical anion, which is formed by electron transfer from the excited AcTrp* to the dimer, and its dissociation product, the monomer radical anion. The AcTrp spectra are completely different from those obtained with an oxidizing sensitizer like anthraquinone-2-sulfonate, because of different unpaired electron spin density distributions in pyrimidine radical anion and cation. In the spectra of the anti (1,3-dimethyluracil) dimers, polarization is detected that originates from a spin-sorting process in the dimer radical pair, pointing to a relatively long lifetime of the dimer radical anions involved. Although the dimer radical anions of the 1,1′-trimethylene-bridged pyrimidines may have a relatively long lifetime as well, their protons have only very weak hyperfine interaction, which explains why no polarization originating from the dimer radical pair is detected. In the spectra of the bridged pyrimidines, polarized dimer protons are observed as a result of spin sorting in the monomer radical pair, from which it follows that the dissociation of dimer radical anion into monomer radical anion is reversible. A study of CIDNP intensities as a function of pH shows that a pH between 3 and 4 is optimal for observing monomer polarization that originates from spin-sorting in the monomer radical pair. At higher pH the geminate recombination polarization is partly cancelled by escape polarization arising in the same product. 相似文献
10.
W. G. Herkstroeter P. A. Martic S. E. Hartman J. L. R. Williams S. Farid 《Journal of polymer science. Part A, Polymer chemistry》1983,21(8):2473-2490
Pyrene substituents covalently bounded to polyelectrolytes show not only excited-state interactions but also unique ground-state interactions in aqueous solution. The pyrene moieties in pyrenesubstituted ionic molecules also show these interactions when aqueous solutions of these molecules are treated with polyelectrolytes or surfactants well below their critical micelle concentrations. These hydrophobic interactions are revealed by changes in absorption, fluorescence, and excitation spectra. The well-resolved vibrational bands in the absorption and excitation spectra of pyrene become somewhat diffuse, whereas monomer fluorescence is reduced and replaced by excimer fluorescence. The rationale for these results is that the pyrene moieties in these ionic solutions seek out hydrophobic locations on the polyelectrolytes or surfactants, where pyrene aggregation is responsible for these interactions and the corresponding changes in spectra. 相似文献