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1.
A Gram-negative, aerobic, rod-shaped, and red-pigmented bacterial strain, HMC5104T, was isolated from a solar saltern, found in Jeungdo, Republic of Korea (34°59′47″N 126°10′02″E). The major fatty acids were summed feature 4 (comprising iso-C17:1 I and/or anteiso-C17:1 B; 37.2%), iso-C15:0 (20.4%), and iso-C17.0 30H (15.3%). The DNA G+C content was 46.0 mol%. The major isoprenoid quinone was menaquinone-7 (MK-7). A phylogenetic tree based on 16S rRNA gene sequences showed that strain HMC5104T formed a lineage within the genus Pontibacter, and was closely related to Pontibacter korlensis (95.9%), P. roseus (94.9%), and P. actiniarum (94.3%). Similarities to all other Pontibacter species were between 95.9–93.9%. On the basis of the evidence presented in this study, strain HMC5104T represents a novel species of the genus Pontibacter, for which the name Pontibacter salisaro sp. nov. is proposed. The type strain is HMC5104T (=KCTC 22712T = NBRC 105731T).  相似文献   

2.
A marine Streptomyces sp. 060524 capable of hydrolyzing the glycosidic bond of isoflavone glycosides, was isolated by detecting its β-glucosidase activity. 5 isoflavone aglycones were isolated from culture filtrates in soybean meal glucose medium. They were identified as genistein (1), glycitein (2), daidzein (3), 3′,4′,5,7-tetrahydroxyisoflavone (4), and 3′,4′,7-trihydroxyisoflavone (5), based on UV, NMR and mass spectral analysis. The Streptomyces can selectively hydroxylate at the 3′-position in the daidzein and genistein to generate 3′-hydroxydaidzein and 3′-hydroxygenistein, respectively. The Strain biotransformed more than 90% of soybean isoflavone glycosides into their aglycones within 108 h. 3′-hydroxydaidzein and 3′-hydroxygenistein exhibited stronger cytotoxicity against K562 human chronic leukemia than daidzein and genistein.  相似文献   

3.
A Gram-negative, rod-shaped, non-spore forming, non-motile and moderate halophilic bacteria designated as strain CMC-5 was isolated from decomposing seaweeds by enrichment culture. The growth of strain CMC-5 was assessed in synthetic seawater-based medium containing polysaccharide. The bacterium degraded and utilized agar, alginate, carrageenan, xylan, carboxymethyl cellulose and chitin. The strain was characterized using a polyphasic approach for taxonomic identification. Cellular fatty acid analysis showed the presence of iso-C15:0 as major fatty acid and significant amounts of iso-C17:1ω9c and C18:1ω7c . Phylogenetic analysis based on 16S rDNA sequence indicated that strain CMC-5 is phylogenetically related to Microbulbifer genus and 99% similar to type strain Microbulbifer elongatus DSM6810T. However in contrast to Microbulbifer elongatus DSM6810T, strain CMC-5 is non-motile, utilizes glucose, galactose, inositol and xylan, does not utilize fructose and succinate nor does it produce H2S. Further growth of bacterial strain CMC-5 was observed when inoculated in seawater-based medium containing sterile pieces of Gracilaria corticata thalli. The bacterial growth was associated with release of reducing sugar in the broth suggesting its role in carbon recycling of polysaccharides from seaweeds in marine ecosystem.  相似文献   

4.
Oligonucleotide analogues containing one or a few glycine, L-, and D-alanine residues instead of phosphodiester internucleotide linkages were synthesized (C3′-NH-C(O)-CH(X)-NH-C(O)-C4′, where X = H, (S)-CH3, and (R)-CH3. The stability of the duplexes of modified oligonucleotides with their wild-type complements was studied. The incorporation of glycine and L-alanine residues into internucleotide linkages was shown to noticeably decrease the stability of modified duplexes as compared to that of native ones (ΔT m∼−2°C per modification), whereas analogues containing D-alanine linkers form duplexes with increased stability (ΔT m∼+2°C per modification).  相似文献   

5.
Summary The growth of GH4C1, GH3, GH1, and GH3C15 rat pituitary tumor cell lines was studied in a serum-free medium (designated TRM-1) formulated with 1∶1 (vol/vol) mixture of Ham's F12 nutrient mixture and Dulbecco's modified Eagle's medium (F12-DME) containing 15 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), 50 μg/ml gentamicin supplemented with 10 μg/ml bovine insulin, 10 μg/ml human transferrin (Tf), 10 ng/ml selenous acid, 10 nM 3,5,3′-triiodothyronine (T3), 50 μM ethanolamine (Etn), and 500 μg/ml bovine serum albumin. Of the lines evaluated, only the GH1 failed to grow in TRM-1. Passage of the GH4C1 and GH3 lines from serum-containing medium into TRM-1 caused an initial selection resulting in cells that grew progressively at higher rates and finally were maintained indefinitely in TRM-1. These populations showed a requirement for supraphysiologic concentrations of T3 (1.0 to 10 nM). After adaptation of the GH4C1 line in TRM-1 for ≤20 generations, removal of components gave a less complex mixture containing 15 mM HEPES, 50 μ/ml gentamicin, 10 μg/ml Tf, 10 nM T3, and 50 μM Etn (designated TRM-2) that supported serial passage of the cells. Under these conditions, thyroid hormone dependence was lost progressively. When T3 was removed from TRM-2 adapted cells, a third population was selected that no longer required thyroid hormones and was only slightly stimulated by T3. These studies demonstrated that the combination of serum-containing and serum-free conditions can be used to select pituitary cell populations that a) required both serum-factor(s) and T3 for optimum growth, b) required supraphysiologic concentrations of T3 without serum proteins other than Tf and albumin, and c) were completely autonomous in that they proliferated in medium supplemented only with Tf and nutrients without necessity of other serum factor(s) or T3. This work was supported by grants CA-26617 and CA-38024 from the National Cancer Institute, Bethesda, MD, American Cancer Society grant BC-255, and grant 2225 from the Council for Tobacco Research, Inc., USA.  相似文献   

6.
 Direct cyclic voltammetry and 1H NMR spectroscopy have been combined to investigate the electrochemical and spectroscopic properties of cytochrome c 553 isolated from the alkaliphilic soil bacterium Bacillus pasteurii. A quasi-reversible diffusion-controlled redox process is exhibited by cytochrome c 553 at a pyrolitic graphite edge microelectrode. The temperature dependence of the reduction potential, measured using a non-isothermal electrochemical cell, revealed a discontinuity at 308 K. The thermodynamic parameters determined in the low-temperature range (275–308 K;ΔS°′=–162.7±1.2 J mol–1 K–1, ΔH°′=–53.0±0.5 kJ mol–1, ΔG°′=–4.5±0.1 kJ mol–1, E°′=+47.0±0.6 mV) indicate the presence of large enthalpic and entropic effects, leading, respectively, to stabilization and destabilization of the reduced form of cytochrome c 553. Both effects are more accentuated in the high-temperature range (308–323 K;ΔS°′=–294.1±8.4 J mol–1 K–1, ΔH°′=–93.4±3.1 kJ mol–1, ΔG°′=–5.8±0.6 kJ mol–1, E°′=+60.3±5.8 mV), with the net result being a slight increase of the standard reduction potential. These thermodynamic parameters are interpreted using the compensation theory of hydration of biopolymers as indicating the extrusion, upon reduction, of water molecules from the hydration sphere of the cytochrome. The low-T and high-T conformers differ by the number of water molecules in the solvation sphere: in the high-T conformer, the number of water molecules extruded upon reduction increases, as compared to the low-T conformer. The ionic strength dependence of the reduction potential at 298 K, treated within the frame of extended Debye-Hückel theory, yields values of E °′ (I=0) =–25.4±1.4 mV, z red=–11.3, and z ox=–10.3. The pH dependence of the reduction potential at 298 K shows a plateau in the pH range 7–10 and an increase at more acidic pH, allowing the calculation of pK O=5.5 and pK R=5.7, together with the estimate of the reduction potentials of completely protonated (+71 mV) and deprotonated (+58 mV) forms of cytochrome c 553. 1H NMR spectra of the oxidized paramagnetic cytochrome c 553 indicate the presence of a His-Met axial coordination of the low-spin (S=1/2) heme iron, which is maintained in the temperature interval 288–340 K at pH 7 and in the pH range 4.8–10.0 at 298 K. The temperature dependence of the hyperfine-shifted signals shows both Curie-type and anti-Curie-type behavior, with marked deviations from linearity, interpreted as indicating the presence of a fast equilibrium between the low-T and high-T conformers, having slightly different heme electronic structures resulting from the T-induced conformational change. Increasing the NaCl concentration in the range 0–0.2 M causes a slight change of the 1H NMR chemical shifts of the hyperfine-shifted signals, with no influence on their linewidth. The calculated lower limit value of the apparent affinity constant for specific ion binding is estimated as 5.2±1.1 M–1. The pH dependence of the isotropically shifted 1H NMR signals of the oxidized cytochrome displays at least one ionization step with pK O=5.7. The thermodynamic and spectroscopic data indicate a large solvent-derived entropic effect as the main cause for the observed low reduction potential of B. pasteurii cytochrome c 553. Received: 9 January 1998 / Accepted: 8 April 1998  相似文献   

7.
8.
An efficient transformation system for rice was established by co-cultivating calli, derived from 21-day-old scutellum, with Agrobacterium tumefaciens cells (OD600 = 0.04), maintained on filter paper, moistened with 4 mL of a medium, and supplemented with 400 μM acetosyringone, for a period of 2 days. Presence of the transgene was confirmed by polymerase chain reaction, and stable integration and copy number of the transgene were determined by Southern blot analysis. Among seven plants analyzed, six possessed single T-DNA integration events, while one plant was found to have two integrated copies of the T-DNA. A total of 45 T0 plants were grown in the greenhouse to obtain the T1 generation. T1 plants evaluated for presence of the transgene and for response to inoculation with the bacterial leaf blight pathogen, Xanthomonas oryzae pv. Oryzae, exhibited Mendelian segregation (3:1) for the transgene as well as enhanced resistance to bacterial blight  相似文献   

9.
Temperature fluctuations during storage and distribution of frozen foods lead to ice recrystallization and microstructural modifications that can affect food quality. Low temperature transitions may occur in frozen foods due to temperature fluctuations, resulting in less viscous and partially melted food matrices. This study systematically investigated the influence of state/phase transitions and temperature fluctuations on ice recrystallization during the frozen storage of salmon fillets. Using a modulated differential scanning calorimeter, we identified the characteristics glass transition temperature (T g ) of −27 °C and the onset temperature for ice crystal melting (T m ) of −17 °C in salmon. The temperature of salmon fillets in sealed plastic trays was lowered to −35 °C in a freezer to achieve the glassy state. The temperature (T) of frozen salmon fillets in sealed plastic trays was modulated to achieve a rubbery state (T > T m ), a partially freeze-concentrated state (T g  < T < T m ) and a glassy state (T < T g ). We performed temperature modulation experiments by exposing packaged salmon to room temperature twice a day for 2 to 26 min during 4 weeks of storage. We also analyzed ice crystal morphology using environmental scanning electron microscopy and X-ray computed tomography techniques to observe the pore distribution after sublimation of ice crystals. Melt–refreeze and isomass rounding mechanisms of ice recrystallization were noticed in the frozen salmon subjected to temperature modulations. Results show that ice crystal growth occurred even in the glassy state of frozen salmon during storage, with or without temperature fluctuations. Ice crystal size in frozen salmon was greater in the rubbery state (T > T m ) due to the increased mobility of unfrozen water compared to the glassy state. The morphological/geometric parameters of ice crystals in frozen salmon stored for 1 month differed significantly from those in 0-day storage. These findings are important to the frozen food industry because they can help optimize storage and distribution conditions and minimize quality loss of frozen salmon due to recrystallization.  相似文献   

10.
High resolution 13C-detected solid-state NMR spectra of the deuterated beta-1 immunoglobulin binding domain of the protein G (GB1) have been collected to show that all 15N, 13C′, 13Cα and 13Cβ sites are resolved in 13C–13C and 15N–13C spectra, with significant improvement in T 2 relaxation times and resolution at high magnetic field (750 MHz). The comparison of echo T 2 values between deuterated and protonated GB1 at various spinning rates and under different decoupling schemes indicates that 13T 2′ times increase by almost a factor of two upon deuteration at all spinning rates and under moderate decoupling strength, and thus the deuteration enables application of scalar-based correlation experiments that are challenging from the standpoint of transverse relaxation, with moderate proton decoupling. Additionally, deuteration in large proteins is a useful strategy to selectively detect polar residues that are often important for protein function and protein–protein interactions.  相似文献   

11.
A Gram-staining-negative, motile, non-spore-forming and rod-shaped bacterial strain, 20-23RT, was isolated from intestine of bensasi goatfish, Upeneus bensasi, and its taxonomic position was investigated by using a polyphasic study. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain 20-23RT belonged to the genus Shewanella. Strain 20-23RT exhibited 16S rRNA gene sequence similarity values of 99.5, 99.2, and 97.5% to Shewanella algae ATCC 51192T, Shewanella haliotis DW01T, and Shewanella chilikensis JC5T, respectively. Strain 20-23RT exhibited 93.1–96.0% 16S rRNA gene sequence similarity to the other Shewanella species. It also exhibited 98.3–98.4% gyrB sequence similarity to the type strains of S. algae and S. haliotis. Strain 20-23RT contained simultaneously both menaquinones and ubiquinones; the predominant menaquinone was MK-7 and the predominant ubiquinones were Q-8 and Q-7. The fatty acid profiles of strain 20–23RT, S. algae KCTC 22552T and S. haliotis KCTC 12896T were similar; major components were iso-C15:0, C16:0, C16:1 ω7c and/or iso-C15:0 2-OH and C17:1 ω8c. The DNA G+C content of strain 20-23RT was 53.9 mol%. Differential phenotypic properties and genetic distinctiveness of strain 20–23RT, together with the phylogenetic distinctiveness, revealed that this strain is distinguishable from recognized Shewanella species. On the basis of the data presented, strain 20-23RT represents a novel species of the genus Shewanella, for which the name Shewanella upenei sp. nov. is proposed. The type strain is 20–23RT (=KCTC 22806T =CCUG 58400T).  相似文献   

12.
Small-angle neutron scattering (SANS) on the unilamellar vesicle (ULV) populations (diameter 500 and 1,000 Å) in D2O was used to characterize lipid vesicles from dimyristoylphosphatidylcholine (DMPC) at three phases: gel Lβ′, ripple Pβ′ and liquid Lα. Parameters of vesicle populations and internal structure of the DMPC bilayer were characterized on the basis of the separated form factor (SFF) model. Vesicle shape changes from nearly spherical in the Lα phase to elliptical in the Pβ′ and Lβ′ phases. This is true for vesicles prepared via extrusion through pores with the diameter 500 Å. Parameters of the internal bilayer structure (thickness of the membrane and the hydrophobic core, hydration and the surface area of the lipid molecule) were determined on the basis of the hydrophobic–hydrophilic (HH) approximation of neutron scattering length density across the bilayer ρ(x) and of the step function (SF) approximation of ρ(x). DMPC membrane thickness in the Lα phase (T=30°C) demonstrates a dependence on the membrane curvature for extruded vesicles. Prepared via extrusion through 500 Å diameter pores, vesicle population in the Lα phase has the following characteristics: average value of minor semi-axis 266±2 Å, ellipse eccentricity 1.11±0.02, polydispersity 26%, thickness of the membrane 48.9±0.2 Å and of the hydrophobic core 19.9±0.4 Å, surface area 60.7±0.5 Å2 and number of water molecules 12.8±0.3 per DMPC molecule. Vesicles prepared via extrusion through pores with the diameter 1,000 Å have polydispersity of 48% and membrane thickness of 45.5±0.6 Å in the Lα phase. SF approximation was used to describe the DMPC membrane structure in Lβ′ (T=10°C) and Pβ′ (T=20°C) phases. Extruded DMPC vesicles in D2O have membrane thickness of 49.6±0.5 Å in the Lβ′ phase and 48.3±0.6 Å in the Pβ′ phase. The dependence of the DMPC membrane thickness on temperature was restored from the SANS experiment.  相似文献   

13.
Three different Salmonella enteritidis phages were isolated and purified from raw sewage by agar-layer technique. The sensitivity of the host organisms toward phages was changed when they were grown on different bacteriological media.The effect of single components of the medium on phage reproduction was determined by the omission of that substance from the medium. CaCl2, MgSO4, and glycerol each had a pronounced stimulatory effect on the phage reproduction, while bile salts had a profound inhibitory effect. The inhibitory effect of bile salts on phage growth was much greater on one strain of Salmonella enteritidis than on the other.  相似文献   

14.
A Gram-negative, motile and rod-shaped bacterial strain, designated S7-3T, was isolated from a tidal flat sediment at Saemankum on the western coast of Korea. Phylogenetic analyses based on 16S rRNA gene and gyrB sequences showed that strain S7-3T belonged to the genus Shewanella, clustering with Shewanella decolorationis S12T. Strain S7-3T exhibited 98.8 % 16S rRNA gene sequence similarity and 96.8 % gyrB sequence similarity to S. decolorationis S12T, respectively. The 16S rRNA gene sequence similarity values between strain S7-3T and other members of the genus Shewanella were in the range of 93.0–98.0 %. Strain S7-3T contained simultaneously both menaquinones (MK) and ubiquinones (Q); the predominant menaquinone was MK-7 and the predominant ubiquinones were Q-7 and Q-8. The fatty acid profiles of strain S7-3T and S. decolorationis JCM 21555T were similar; major components were C17:1 ω8c, iso-C15:0 and iso-C15:0 2-OH and/or C16:1 ω7c. The DNA G+C content of strain S7-3T was 51.8 mol% and its mean DNA–DNA relatedness value with S. decolorationis JCM 21555T was 43 %. Differential phenotypic properties of strain S7-3T, together with the phylogenetic and genetic distinctiveness, revealed that this strain is distinguishable from recognized Shewanella species. On the basis of the data presented, strain S7-3T is considered to represent a novel Shewanella species, for which the name Shewanella seohaensis sp. nov. is proposed. The type strain is S7-3T (=KCTC 23556T = CCUG 60900T).  相似文献   

15.
The 3′ half molecule of yeast tRNAAla (nucleotides 36–75) was hybridized with a DNA fragment (5′GGAATCGAACC 3′) and the hybrid was then digested withE. coli RNase H (from Boehringer). The enzyme can specifically cleave the 3′ half molecule at the 3′ side of nucleotide Ψ55, thus a fragment C3655 was prepared. The 3′-terminal T or TΨ of this fragment was removed by one or two cycles of periodate oxidation and β-elimination. The products were fragments C36-T54 and C36-G53. Three yeast tRNAAla fragments C56-A76, U55-A76 (with Ψ55 replaced by U), U54-A76 (with T54Ψ55 replaced by UU) were synthesized and ligated with three prepared fragments (C3655, C36-T54 and C36-G53) respectively by T4 RNA ligase. The products were further ligated with the 5′ half molecule (nu-cleotides 1–35). Using this method, one reconstituted yeast tRNAAla (tRNAr) and two yeast tRNAALa analogs: (i) tRNAa with U55 instead of Ψ55; (ii) tRNAb with U54U55 instead of T54Ψ55 were synthesized. The charging and incorporation activities of these three tRNAs were determined. In comparison with the reconstituted tRNA, the charging activity was 75% for tRNAa and 45% for tRNAb and the incorporation activity was 65% for tRNAa and 70% for tRNAb. These results suggest that the modified nucleotides T54 and Ψ55 play an important role in yeast tRNAAla function. Project supported by the National Natural Science Foundation of China.  相似文献   

16.
 An elite indica rice variety, ‘IR72’, was transformed with a cloned gene, Xa21, through particle bombardment. Molecular analysis of transgenic plants revealed the presence of a 3.8-kb EcoRV-digested DNA fragment corresponding to most of the Xa21 coding region and its complete intron sequence, indicating the integration of Xa21 into the genome of ‘IR72’. In the T1 generation, the transgene was inherited and segregated in a 3:1 ratio. After inoculation with the prevalent races 4 and 6 of Xanthomonas oryzae pv. oryzae (Xoo), T1 plants positive for the transgene were found to be resistant to bacterial blight (BB). We also observed that the level of resistance to race 4 of Xoo was higher due to the pyramiding of Xa21 and Xa4 present in ‘IR72’. Since the inactivation of the transgene Xa21 occurred in the two transgenic T1 plants, a larger progeny should be obtained for selecting homozygous line with a consistently higher level of resistance to the BB pathogen. Received: 13 October 1997 / Accepted: 21 October 1997  相似文献   

17.
The role of ATP and its stable analogue ATPγS [adenosine-5′-o-(3-thio)triphosphate] was studied in rat hippocampal neurotransmission under normoxic conditions and during oxygen and glucose deprivation (OGD). Field excitatory postsynaptic potentials (fEPSPs) from the dendritic layer or population spikes (PSs) from the soma were extracellularly recorded in the CA1 area of the rat hippocampus. Exogenous application of ATP or ATPγS reduced fEPSP and PS amplitudes. In both cases the inhibitory effect was blocked by the selective A1 adenosine receptor antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine) and was potentiated by different ecto-ATPase inhibitors: ARL 67156 (6-N,N-diethyl-D-β,γ-dibromomethylene), BGO 136 (1-hydroxynaphthalene-3,6-disulfonate) and PV4 [hexapotassium dihydrogen monotitanoundecatungstocobaltate(II) tridecahydrate, K6H2[TiW11CoO40]·13H2O]. ATPγS-mediated inhibition was reduced by the P2 antagonist suramin [8-(3-benzamido-4-methylbenzamido)naphthalene-1,3,5-trisulfonate] at the somatic level and by other P2 blockers, PPADS (pyridoxalphosphate-6-azophenyl-2′,4′-disulfonate) and MRS 2179 (2′-deoxy-N 6-methyladenosine 3′,5′-bisphosphate), at the dendritic level. After removal of both P2 agonists, a persistent increase in evoked synaptic responses was recorded both at the dendritic and somatic levels. This effect was prevented in the presence of different P2 antagonists. A 7-min OGD induced tissue anoxic depolarization and was invariably followed by irreversible loss of fEPSP. PPADS, suramin, MRS2179 or BBG (brilliant blue G) significantly prevented the irreversible failure of neurotransmission induced by 7-min OGD. Furthermore, in the presence of these P2 antagonists, the development of anoxic depolarization was blocked or significantly delayed. Our results indicate that P2 receptors modulate CA1 synaptic transmission under normoxic conditions by eliciting both inhibitory and excitatory effects. In the same brain region, P2 receptor stimulation plays a deleterious role during a severe OGD insult.  相似文献   

18.
The Arabidopsis AHL gene encodes a 3′(2′),5′-bisphosphate nucleotidase (BPNTase) involved in the reductive sulfate activation pathway. A bacterial expression vector containing AHL cDNA was randomly mutagenized with hydroxylamine and transformed into the E. coli cysteine auxotrophic mutant cysQ. Bacterial colonies that did not show evidence of complementation, i.e. those that exhibited slower growth on cysteine-free medium, were selected for further study. Sequencing of the AHL cDNA in one such clone revealed the conversion of cytosine 635 (C635) to thymine, resulting in an Alanine (A212) to Valine substitution. This microbial complementation procedure is useful in BPNTase structure-activity studies for biotechnological applications.  相似文献   

19.
20.
Adenosine-5′-methylphosphate (MepA) initiates the oligomerization of the 5′-phosphorimidazolide of uridine (ImpU) in the presence of montmorillonite clay. Longer oligomers form because the 5′-phosphate is blocked with a methyl group that prevents the formation of cyclic- and pyrophosphate-containing compounds. The MepA initiates 69–84% of the 5–9 charge oligomers, respectively. The montmorillonite catalyst also provides selectivity in the oligomerization reactions so that the main reaction pathway is MepA → MepA3′pU → MepA3′pU2′pU → MepA3′pU2′pU3′pU. MepA did not enhance the oligomerization of ImpA. The relative rates of the reactions were determined from an investigation of the products in competitive reactions. Selectivity was observed in the reaction of ImpU with equimolar amounts of MepA3′pU and MepA2′pU where the relative reaction rates are 10.3:1, respectively. In the reaction of ImpA with MepA3′pA and MepA2′pA the ImpA reacts 5.2 times faster with MepA3′pA. In the competitive reaction of ImpU and ImpA with MepA3′pA and MepA3′pU the elongation proceeds on MepA3′pA 5.6 times more rapidly than with MepA3′pU. There is no correlation between the extent of binding to the montmorillonite and reaction rates in the formation of longer oligomers. The formation of more than two sequential 2′,5′-linkages in the oligomer chain proceeds more slowly than the addition to a single 2′,5′-link or a 3′,5′-link and either chain termination or elongation by a 3′,5′-linage occurs. The central role that catalysis may have had in the prebiotic formation of biopolymers is discussed. Note added in proof: There are errors in the high resolution mass spectral data given in Section 4.2.1. The high resolution mass spectrum found for the cyclic dimer of UpUp (C-UpUp) was 657.02260. C18H21N4O16P2Na2 requires 657.02232. The high resolution mass spectrum found for the cyclic dimer of ApAp (C-ApAp) was 725.05850. C20H22N10O12P2Na3 requires 725.05839.  相似文献   

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