RESUMO
We developed a microscopic scanning for vibrational circular dichroism (VCD) spectroscopy in which a quantum cascade laser is equipped with a highly focused infrared light source to attain a spatial resolution of 100 µm. This system was applied to the forewing of a European hornet to reveal how the protein domains are organised. Two-dimensional patterns were obtained from the VCD signals with steps of 100 µm. We scanned the 1500-1740 cm-1 wavenumber range, which covers amide I and II absorptions. Zone sequenced α-helical and ß-sheet domains within an area of 200 µm2 in membranes close to where two veins cross. The sign of the VCD signal at 1650 cm-1 changed from positive to negative when probed along the zone axis, intermediated by the absence of VCD activity. The significance of this zone is discussed from the viewpoint of the mechanical properties required for flying motion. These features are unattainable using conventional FTIR (Fourier transform infrared) or FT-VCD methods with a spatial resolution of â¼10 mm2.
Assuntos
Dicroísmo Circular , Animais , Estrutura Secundária de Proteína , Vibração , Domínios Proteicos , Proteínas/químicaRESUMO
This study reports the microscopic measurements of vibrational circular dichroism (VCD) on four different insect wings using a quantum cascade laser VCD system equipped with microscopic scanning capabilities (named multi-dimensional VCD [MultiD-VCD]). Wing samples, including (i) beetle, Anomala albopilosa (female), (ii) European hornet, Verspa crabro flavofasciata Cameron, 1903 (female), (iii) tiny dragonfly, Nannophya pygmae Rambur, 1842 (male), and (iv) dragonfly, Symetrum gracile Oguma, 1915 (male), were used in this study. Two-dimensional patterns of VCD signals (~10 mm × 10 mm) were obtained at a spatial resolution of 100 µm. Measurements covered the absorption peaks assigned to amides I and II in the range of 1500-1740 cm-1 . The measurements were based on the enhancement of VCD signals for the stereoregular linkage of peptide groups. The patterns were remarkably dependent on the species. In samples (i) and (ii), the wings comprised segregated domains of protein aggregates of different secondary structures. The size of each microdomain was approximately 100 µm. In contrast, no clear VCD spectra were detected in samples (iii) and (iv). One possible reason was that the chain of stereoregular polypeptides was too short to achieve VCD enhancement in samples (iii) and (iv). Notably, the unique features were only observed in the VCD spectra because the IR spectra were nearly the same among the species. The VCD results hinted at the connection of protein microscopic structures with the wing flapping mechanisms of each species.
Assuntos
Odonatos , Feminino , Masculino , Animais , Dicroísmo Circular , Estereoisomerismo , Peptídeos/química , ProteínasRESUMO
Extant organisms commonly use 20 amino acids in protein synthesis. In the translation system, aminoacyl-tRNA synthetase (ARS) selectively binds an amino acid and transfers it to the cognate tRNA. It is postulated that the amino acid repertoire of ARS expanded during the development of the translation system. In this study we generated composite phylogenetic trees for seven ARSs (SerRS, ProRS, ThrRS, GlyRS-1, HisRS, AspRS, and LysRS) which are thought to have diverged by gene duplication followed by mutation, before the evolution of the last universal common ancestor. The composite phylogenetic tree shows that the AspRS/LysRS branch diverged from the other five ARSs at the deepest node, with the GlyRS/HisRS branch and the other three ARSs (ThrRS, ProRS and SerRS) diverging at the second deepest node. ThrRS diverged next, and finally ProRS and SerRS diverged from each other. Based on the phylogenetic tree, sequences of the ancestral ARSs prior to the evolution of the last universal common ancestor were predicted. The amino acid specificity of each ancestral ARS was then postulated by comparison with amino acid recognition sites of ARSs of extant organisms. Our predictions demonstrate that ancestral ARSs had substantial specificity and that the number of amino acid types amino-acylated by proteinaceous ARSs was limited before the appearance of a fuller range of proteinaceous ARS species. From an assumption that 10 amino acid species are required for folding and function, proteinaceous ARS possibly evolved in a translation system composed of preexisting ribozyme ARSs, before the evolution of the last universal common ancestor.
Assuntos
Aminoacil-tRNA Sintetases , Aminoácidos/genética , Aminoacil-tRNA Sintetases/genética , Aminoacil-tRNA Sintetases/metabolismo , Filogenia , RNA de Transferência/metabolismoRESUMO
Much of the information about the size and shape of aerosols forming haze and the cloud layer of Venus is obtained from indirect inferences from nephelometers on probes and from the analysis of the variation of polarization with the phase angle and the glory feature from images of Venus. The microscopic imaging of Venus' aerosols has recently been advocated. Direct measurements from a fluorescence microscope can provide information on the morphology, density, and biochemical characteristics of the particles; thus, fluorescence microscopy is attractive for in situ particle characterization of the Venus cloud layer. Fluorescence imaging of Venus cloud particles presents several challenges owing to the sulfuric acid composition and corrosive effects. In this article, we identify the challenges and describe our approach to overcoming them for a fluorescence microscope based on an in situ biochemical and physical characterization instrument for use in the clouds of Venus from a suitable aerial platform. We report that pH adjustment using alkali was effective for obtaining fluorescence images and that fluorescence attenuation was observed after the adjustment, even when the acidophile suspension in concentrated sulfuric acid was used as a sample.
Assuntos
Atmosfera , Vênus , Aerossóis , Atmosfera/química , Microscopia de FluorescênciaRESUMO
Knowledge on the evolution of antioxidant systems in cyanobacteria is crucial for elucidating the cause and consequence of the rise of atmospheric oxygen in the Earth's history. In this study, to elucidate the origin and evolution of cyanobacterial antioxidant enzymes, we analyzed the occurrence of genes encoding four types of superoxide dismutases and three types of catalases in 85 complete cyanobacterial genomes, followed by phylogenetic analyses. We found that Fe superoxide dismutase (FeSOD), Mn superoxide dismutase (MnSOD), and Mn catalase (MnCat) are widely distributed among modern cyanobacteria, whereas CuZn superoxide dismutase (CuZnSOD), bifunctional catalase (KatG), and monofunctional catalase (KatE) are less common. Ni superoxide dismutase (NiSOD) is distributed among marine Prochlorococcus and Synechococcus species. Phylogenetic analyses suggested that bacterial MnSOD evolved from cambialistic Fe/MnSOD before the diversification of major bacterial lineages. The analyses suggested that FeSOD evolved from MnSOD before the origin of cyanobacteria. MnCat also evolved in the early stages of bacterial evolution, predating the emergence of cyanobacteria. KatG, KatE, and NiSOD appeared 2.3-2.5 billion years ago. Thus, almost all cyanobacterial antioxidant enzymes emerged before or during the rise of atmospheric oxygen. The loss and appearance of these enzymes in marine cyanobacteria may be also related to the change in the metal concentration induced by the increased oxygen concentration in the ocean.
Assuntos
Antioxidantes , Cianobactérias , Catalase/genética , Cianobactérias/genética , Oxigênio , Filogenia , Superóxido Dismutase/genéticaRESUMO
Cu(ii) complexes containing RR- or SS-2,2'-isopropylidene-bis(4-phenyl-2-oxazoline) (denoted as [Cu(RR- or SS-oxa)]2+) are known to catalyse many asymmetric organic reactions. Herein, the source of enantioselectivity was investigated by vibrational circular dichroism (VCD) spectroscopy. An achiral ß-diketonato ligand (denoted as LH), such as 1-phenyl-1,3-butanedione and dibenzoylmethane, was added to form [Cu(RR- or SS-oxa)L]+. Clear VCD peaks were obtained from a CDCl3 solution of [Cu(RR- or SS-oxa)]2+ or [Cu(RR- or SS-oxa)L]+ at 1000-1800 cm-1. It is to be noted that when LH was coordinated, a new VCD peak appeared at â¼1380 cm-1, which was assigned to the C-O asymmetric stretching vibration of L-. Theoretical simulation helped rationalise the results in terms of the transformation of coordinated L- into a twisted chiral form. The extent of steric control within the coordination sphere was demonstrated, revealing the first step for enantioselectivity during catalysis.
RESUMO
Paleotemperatures inferred from the isotopic compositions (δ18O and δ30Si) of marine cherts suggest that Earth's oceans cooled from 70 ± 15 °C in the Archean to the present â¼15 °C. This interpretation, however, has been subject to question due to uncertainties regarding oceanic isotopic compositions, diagenetic or metamorphic resetting of the isotopic record, and depositional environments. Analyses of the thermostability of reconstructed ancestral enzymes provide an independent method by which to assess the temperature history inferred from the isotopic evidence. Although previous studies have demonstrated extreme thermostability in reconstructed archaeal and bacterial proteins compatible with a hot early Earth, taxa investigated may have inhabited local thermal environments that differed significantly from average surface conditions. We here present thermostability measurements of reconstructed ancestral enzymatically active nucleoside diphosphate kinases (NDKs) derived from light-requiring prokaryotic and eukaryotic phototrophs having widely separated fossil-based divergence ages. The ancestral environmental temperatures thereby determined for these photic-zone organisms--shown in modern taxa to correlate strongly with NDK thermostability--are inferred to reflect ancient surface-environment paleotemperatures. Our results suggest that Earth's surface temperature decreased over geological time from â¼65-80 °C in the Archean, a finding consistent both with previous isotope-based and protein reconstruction-based interpretations. Interdisciplinary studies such as those reported here integrating genomic, geologic, and paleontologic data hold promise for providing new insight into the coevolution of life and environment over Earth history.
Assuntos
Archaea , Proteínas Arqueais/genética , Proteínas de Bactérias/genética , Cianobactérias , Evolução Molecular , Núcleosídeo-Difosfato Quinase/genética , Proteínas de Plantas/genética , Plantas , Archaea/enzimologia , Archaea/genética , Cianobactérias/enzimologia , Cianobactérias/genética , Planeta Terra , Fontes Hidrotermais/microbiologia , Oceanos e Mares , Plantas/enzimologia , Plantas/genética , Microbiologia da ÁguaRESUMO
A mixture of chiral low-molecular weight gelators, (1R,2R)- or (1S,2S)-N,N'-diperfluoroheptanoyl-1,2-diaminocyclohexane (denoted as RR- or SS-CF7, respectively) and (1R,2R)- or (1S,2S)-N,N'-diheptanoyl-1,2-diaminocyclohexane (denoted as RR- or SS-CH7, respectively), was used as a two-component gelator in acetonitrile solvent. The process of gelation was investigated by time-step vibrational circular dichroism (VCD) spectroscopy. The method enabled us to study the dynamical behavior of CF7 and CH7 molecules independent of their characteristic vibrational bands. We focused on the effects of the chirality relation between the two gelators. In the case of the enantiomeric mixtures (RR-CF7/RR-CH7 or SS-CF7/SS-CH7), the two components exhibited different time-courses in their VCD spectra. As for CF7, the couplet peak intensities assigned to C[double bond, length as m-dash]O stretching increased with time, while those for CH7 remained low. In the case of the racemic mixture (RR-CF7/SS-CH7 or SS-CF7/RR-CH7), the intensities of the peaks assigned to the C[double bond, length as m-dash]O stretching vibration for both CF7 and CH7 molecules maintained a constant level with time. The VCD results were compared with the SEM images of the freeze-dried gel samples taken at various time intervals. Furthermore, the mechanisms for the gelation of two-component systems are discussed.
RESUMO
Vibrational circular dichroism (VCD) spectroscopy was applied to study chirality recognition in the interlayer space of a clay mineral. Clay intercalation compounds including two kinds of chiral molecules were prepared. Firstly a cationic metal complex, Δ- or Λ-[Ru(phen)3]2+ (phen = 1,10-phenanthroline), was ion-exchanged into sodium montmorillonite. Thereafter a neutral organic molecule, R- or S-1,1'-bi-2-naphthol (denoted as R- or S-BINOL), was co-adsorbed. The solid state VCD spectra were recorded on the hybrid compounds thus prepared. The intensity of VCD peaks in the region of 1300-1400 cm-1, which were assigned to the bending vibrations of OH groups in BINOL, was remarkably dependent on the chirality relation between the two intercalated species. This implied that BINOL took a different conformation in response to the chirality of co-existing [Ru(phen)3]2+.
RESUMO
Vibrational circular dichroism (VCD) spectroscopy was applied to study intermolecular interactions on the surface of a clay mineral. A montmorillonite clay loaded with two kinds of chiral molecules was prepared. Firstly a cationic ruthenium(ii) complex, Δ- or Λ-[Ru(phen)3]2+ (phen = 1,10-phenanthroline), was ion-exchanged into sodium montmorillonite (denoted as [Ru(phen)3]2+/mont). Thereafter a neutral metal(iii) complex, Δ- or Λ-[M(acac)3] (acac = acetylacetonato; M = Co and Cr), was adsorbed spontaneously, when the complex was added to an aqueous dispersion of [Ru(phen)3]2+/mont (denoted as [M(acac)3]/[Ru(phen)3]2+/mont). VCD measurements were performed on a KBr disk containing ca. 1 wt% of solid [M(acac)3]/[Ru(phen)3]2+/mont. Both of the chiral components gave clear VCD peaks in the wavelength region of 1200-1800 cm-1. Attention was focussed on the spectral differences between the following two samples: the one containing a pair of co-adsorbed chelates with the same chirality (i.e. Λ-[M(acac)3]/Λ-[Ru(phen)3]2+/mont or Δ-[M(acac)3]/Δ-[Ru(phen)3]2+/mont) and the other containing a pair of co-adsorbed chelates with the opposite chirality (i.e. Δ-[M(acac)3]/Λ-[Ru(phen)3]2+/mont or Λ-[M(acac)3]/Δ-[Ru(phen)3]2+/mont). Notably a new peak shoulder appeared and the relative peak intensity of the couplet peaks varied, depending on the chirality relation between the co-existing complexes. With the help of theoretical calculations, these results were rationalized in terms of the stereoselective intermolecular interactions.
RESUMO
For de novo design of protein-protein interactions (PPIs), information on the shape and chemical complementarity of their interfaces is generally required. Recent advances in computational PPI design have allowed for de novo design of protein complexes, and several successful examples have been reported. In addition, a simple and easy-to-use approach has also been reported that arranges leucines on a solvent-accessible region of an α-helix and places charged residues around the leucine patch to induce interactions between the two helical peptides. For this study, we adopted this approach to de novo design a new PPI between the helical bundle proteins sulerythrin and LARFH. A non-polar patch was created on an α-helix of LARFH around which arginine residues were introduced to retain its solubility. The strongest interaction found was for the LARFH variant cysLARFH-IV-3L3R and the sulerythrin mutant 6L6D (KD=0.16 µM). This artificial protein complex is maintained by hydrophobic and ionic interactions formed by the inter-molecular helical bundle structure. Therefore, by the simple and easy-to-use approach to create de novo interfaces on the α-helices, we successfully generated an artificial PPI. We also created a second LARFH variant with the non-polar patch surrounded by positively charged residues at each end. Upon mixing this LARFH variant with 6L6D, mesh-like fibrous nanostructures were observed by atomic force microscopy. Our method may, therefore, also be applicable to the de novo design of protein nanostructures.
Assuntos
Hemeritrina/química , Repressores Lac/química , Complexos Multiproteicos , Mapas de Interação de Proteínas , Estrutura Secundária de Proteína/genética , Rubredoxinas/química , Sequência de Aminoácidos/genética , Sítios de Ligação , Dissulfetos/química , Escherichia coli/química , Hemeritrina/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Repressores Lac/metabolismo , Leucina , Ligação Proteica , Engenharia de Proteínas , Dobramento de Proteína , Rubredoxinas/metabolismo , Solventes/química , Sulfolobus/química , Sulfolobus/metabolismoRESUMO
The three-domain phylogenetic system of life has been challenged, particularly with regard to the position of Eukarya. The recent increase of known genome sequences has allowed phylogenetic analyses of all extant organisms using concatenated sequence alignment of universally conserved genes; these data supported the two-domain hypothesis, which place eukaryal species as ingroups of the Domain Archaea. However, the origin of Eukarya is complicated: the closest archaeal species to Eukarya differs in single-gene phylogenetic analyses depending on the genes. In this report, we performed molecular phylogenetic analyses of 23 aminoacyl-tRNA synthetases (ARS). Cytoplasmic ARSs in 12 trees showed a monophyletic Eukaryotic branch. One ARS originated from TACK superphylum. One ARS originated from Euryarchaeota and three originated from DPANN superphylum. Four ARSs originated from different bacterial species. The other 8 cytoplasmic ARSs were split into two or three groups in respective trees, which suggested that the cytoplasmic ARSs were replaced by secondary ARSs, and the original ARSs have been lost during evolution of Eukarya. In these trees, one original cytoplasmic ARS was derived from Euryarchaeota and three were derived from DPANN superphylum. Our results strongly support the two-domain hypothesis. We discovered that rampant-independent lateral gene transfers from several archaeal species of DPANN superphylum have contributed to the formation of Eukaryal cells. Based on our phylogenetic analyses, we proposed a model for the establishment of Eukarya.
Assuntos
Aminoacil-tRNA Sintetases/genética , Eucariotos/genética , Sequência de Aminoácidos/genética , Archaea/genética , Bactérias/genética , Sequência de Bases/genética , Evolução Biológica , Simulação por Computador , Células Eucarióticas , Evolução Molecular , Transferência Genética Horizontal/genética , Modelos Genéticos , Filogenia , Alinhamento de Sequência/métodosRESUMO
Bacteria and Eukarya have cell membranes with sn-glycerol-3-phosphate (G3P), whereas archaeal membranes contain sn-glycerol-1-phosphate (G1P). Determining the time at which cells with either G3P-lipid membranes or G1P-lipid membranes appeared is important for understanding the early evolution of terrestrial life. To clarify this issue, we reconstructed molecular phylogenetic trees of G1PDH (G1P dehydrogenase; EgsA/AraM) which is responsible for G1P synthesis and G3PDHs (G3P dehydrogenase; GpsA and GlpA/GlpD) and glycerol kinase (GlpK) which is responsible for G3P synthesis. Together with the distribution of these protein-encoding genes among archaeal and bacterial groups, our phylogenetic analyses suggested that GlpA/GlpD in the Commonote (the last universal common ancestor of all extant life with a cellular form, Commonote commonote) acquired EgsA (G1PDH) from the archaeal common ancestor (Commonote archaea) and acquired GpsA and GlpK from a bacterial common ancestor (Commonote bacteria). In our scenario based on this study, the Commonote probably possessed a G3P-lipid membrane synthesized enzymatically, after which the archaeal lineage acquired G1PDH followed by the replacement of a G3P-lipid membrane with a G1P-lipid membrane.
Assuntos
Archaea/enzimologia , Membrana Celular/química , Evolução Molecular , Glicerol Quinase/genética , Glicerolfosfato Desidrogenase/genética , Fosfolipídeos/metabolismo , Archaea/genética , Filogenia , Homologia de Sequência de AminoácidosRESUMO
Through various in situ analyses, we have revealed the structural changes that occur during the reversible melting-solidification process of layered alkylsiloxanes (CnLSiloxanes) with carbon numbers (n) of 18 and 16. In situ high-resolution solid-state (13)C nuclear magnetic resonance (NMR) analysis at controlled temperatures indicates drastic conformational changes of the long alkyl chains during the melting-solidification process. A (13)C NMR signal at 33 ppm, which shows the highest intensity at room temperature (RT), is assigned to an inner methylene group with an all-trans conformation. As the temperature increases, the 33-ppm signal intensity decreases while the signal intensity at 30.5 ppm simultaneously increases. The 30.5 ppm signal is assigned to an inner methylene group with a trans-gauche conformation. Subsequently, upon cooling, the signal at 33 ppm recovers, even after CnLSiloxanes have melted. In situ X-ray diffraction measurements at controlled temperatures reveal that the ordered arrangement of the long alkyl chains becomes disordered with elevating temperatures and reordered upon cooling to RT. In situ high-resolution solid-state (29)Si NMR analysis shows that the melting-solidification process progresses without any structural change in siloxane sheets of the CnLSiloxanes. Thus, the in situ analyses show that disordering of the long alkyl chains causes the CnLSiloxanes to melt. Because the majority of long alkyl chains are packed again in the ordered arrangement with the all-trans conformation upon cooling, the CnLSiloxanes are reversibly solidified and the CnLSiloxane structure is recovered.
RESUMO
Vibrational circular dichroism (VCD) spectroscopy was applied to gelation by a chiral low-molecular mass weight gelator, N,N'-diperfluoroalkanoyl-1,2-trans-diaminocyclohexane. Attention was focused on the winding effects of (-CF2 )n chains on the gelating ability. For this purpose, a series of gelators were synthesized with perfluoroalkyl chains of different length (n = 6-8). When gelation was studied using acetonitrile as a solvent, the fibrils took different morphologies, depending on the chain length: twisted saddle-like ribbon or helical ribbon from fibril (n = 6) and a helical ribbon from platelet (n = 8). The signs of VCD peaks assigned to the couplet of C=O stretching and to the C-F stretching were also dependent on n, indicating that a gelator molecule changed conformation on elongating perfluoroalkyl chains. A model is proposed for the aggregation modes in fibrils. Chirality 28:361-364, 2016. © 2016 Wiley Periodicals, Inc.
Assuntos
Dicroísmo Circular/métodos , Cicloexilaminas/química , Géis/química , Acetonitrilas/química , Microscopia Eletrônica de Varredura , Conformação Molecular , Estereoisomerismo , VibraçãoRESUMO
Theoretical studies have focused on the environmental temperature of the universal common ancestor of life with conflicting conclusions. Here we provide experimental support for the existence of a thermophilic universal common ancestor. We present the thermal stabilities and catalytic efficiencies of nucleoside diphosphate kinases (NDK), designed using the information contained in predictive phylogenetic trees, that seem to represent the last common ancestors of Archaea and of Bacteria. These enzymes display extreme thermal stabilities, suggesting thermophilic ancestries for Archaea and Bacteria. The results are robust to the uncertainties associated with the sequence predictions and to the tree topologies used to infer the ancestral sequences. Moreover, mutagenesis experiments suggest that the universal ancestor also possessed a very thermostable NDK. Because, as we show, the stability of an NDK is directly related to the environmental temperature of its host organism, our results indicate that the last common ancestor of extant life was a thermophile that flourished at a very high temperature.
Assuntos
Estabilidade Enzimática/genética , Evolução Molecular , Núcleosídeo-Difosfato Quinase/genética , Sequência de Aminoácidos , Proteínas Arqueais/química , Proteínas Arqueais/classificação , Proteínas Arqueais/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/classificação , Proteínas de Bactérias/genética , Sequência Consenso , Cristalografia por Raios X , Modelos Moleculares , Dados de Sequência Molecular , Núcleosídeo-Difosfato Quinase/química , Núcleosídeo-Difosfato Quinase/classificação , Origem da Vida , Filogenia , Homologia de Sequência de Aminoácidos , TemperaturaRESUMO
A non-polar patch on the surface of a protein can cause a reduction in the solubility and stability of the protein, and thereby induce aggregation. However, a non-polar patch may be required so that the protein can bind to another molecule. The mutant 6L-derived from the acidic, dimeric α-helical protein sulerythrin and containing six additional leucines arranged to form a non-polar patch on its surface when properly folded-has a substantially reduced solubility in comparison with that of wild-type sulerythrin. This reduced solubility appears to cause 6L to aggregate. To reverse this aggregation, we mutated 6L so that it contained three to six additional glutamates or aspartates that we predicted would surround the non-polar leucine patch on natively folded 6L. Although the introduction of three glutamates or aspartates increased solubility, the mutants still aggregate and have a reduced α-helical content. Conversely, mutants with six additional glutamates or aspartates appear to exist mostly as dimers and to have the same α-helical content as that of wild-type sulerythrin. Notably, the introduction of five lysines or five arginines at the positions held by the glutamates or aspartates did not recover solubility as effectively as did the negatively charged residues. These results demonstrate that negatively charged residues, but not positively charged ones, surrounding a non-polar patch on an acidic protein can completely reverse the decrease in its solubility caused by the patch of non-polar surface residues.
Assuntos
Ácidos/química , Proteínas/química , Cromatografia em Gel , Dicroísmo Circular , Modelos Moleculares , Conformação Proteica , Dobramento de Proteína , Solubilidade , Espectrometria de Fluorescência , Espectrofotometria UltravioletaRESUMO
Seafloor massive sulfides are a potential energy source for the support of chemosynthetic ecosystems in dark, deep-sea environments; however, little is known about microbial communities in these ecosystems, especially below the seafloor. In the present study, we performed culture-independent molecular analyses of sub-seafloor sulfide samples collected in the Southern Mariana Trough by drilling. The depth for the samples ranged from 0.52 m to 2.67 m below the seafloor. A combination of 16S rRNA and functional gene analyses suggested the presence of chemoautotrophs, sulfur-oxidizers, sulfate-reducers, iron-oxidizers and iron-reducers. In addition, mineralogical and thermodynamic analyses are consistent with chemosynthetic microbial communities sustained by sulfide minerals below the seafloor. Although distinct bacterial community compositions were found among the sub-seafloor sulfide samples and hydrothermally inactive sulfide chimneys on the seafloor collected from various areas, we also found common bacterial members at species level including the sulfur-oxidizers and sulfate-reducers, suggesting that the common members are widely distributed within massive sulfide deposits on and below the seafloor and play a key role in the ecosystem function.
Assuntos
Carbono/química , Sedimentos Geológicos/microbiologia , Ferro/química , Microbiota/genética , Enxofre/química , Archaea/genética , Archaea/isolamento & purificação , Archaea/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Sequência de Bases , Ecossistema , Sedimentos Geológicos/análise , Sedimentos Geológicos/química , Microbiota/fisiologia , Oceanos e Mares , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Sulfetos/químicaRESUMO
Energy transfer was investigated between two types of iridium(III) complexes, [Ir(dfppy)2(Cn-bpy)](+) (dfppyH = 2-(2',4'-difluorophenyl)pyridine; Cn-bpy = 4,4'-dialkyl-2,2'-bipyridine; dialkyl = dimethyl (C1), didodecyl (C12), and dinonyldecyl (C19)) and [Ir(piq)2(Cn-bpy)](+) (piqH = 1-phenylisoquinoline) as a donor and an acceptor, respectively. The complexes were co-adsorbed by colloidally dispersed synthetic saponite. The efficiency of energy transfer (η(ET)) was obtained from emission spectra at various donor-to-acceptor ratios (D/A) on the basis of the Förster-type energy transfer mechanism. For C1-bpy, η(ET) was as high as 0.5 with a D/A of ca. 20. The results implied that the photon energy captured by several donor molecules was collected by a single acceptor molecule (i.e. the harvesting of light energy). Enantioselectivity was observed, which indicates the participation of a contact pair of donor and acceptor molecules. For C12-bpy and C19-bpy, η(ET) was low and exhibited no enantioselectivity, because their long alkyl chains inhibited close contact between the donor and acceptor molecules.
RESUMO
The attempts of applying chiroptical spectroscopy to supramolecular chirality are reviewed with a focus on vibrational circular dichroism (VCD). Examples were taken from gels, solids, and monolayers formed by low-molecular mass weight chiral gelators. Particular attention was paid to a group of gelators with perfluoroalkyl chains. The effects of the helical conformation of the perfluoroalkyl chains on the formation of chiral architectures are reported. It is described how the conformation of a chiral gelator was determined by comparing the experimental and theoretical VCD spectra together with a model proposed for the molecular aggregation in fibrils. The results demonstrate the potential utility of the chiroptical method in analyzing organized chiral aggregates.