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  • 1
    Online Resource
    Online Resource
    Secretin PulD: Association with pilot PulS, structure, and ion-conducting channel formation
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 14 ( 1999-07-06), p. 8173-8177
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 14 ( 1999-07-06), p. 8173-8177
    Abstract: The outer membrane protein PulD (secretin) of Klebsiella oxytoca is required for transport of pullulanase across this membrane. We have purified a multimeric PulD complex from an Escherichia coli strain expressing all the proteins involved in pullulanase secretion. The outer membrane-anchored lipoprotein PulS was found to copurify with PulD. The molar ratio of the two proteins is close to 1:1, and the size of the complex is ≈1 MDa. Scanning transmission electron and cryo-electron microscopy analyses showed that the purified complex is a cylindrical structure having a central cavity of ≈7.6 nm and peripheral radial spokes. Fusion of proteoliposomes containing the purified complex with a planar lipid bilayer resulted in the appearance of small, voltage-activated, ion-conducting channels. We conclude that the central cavity seen in the electron microscope is part of a large gated channel and propose that the observed current fluctuations correspond to voltage-induced, relatively minor displacements of domains in the purified complex rather than to a complete opening of the secretin channel.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.14.8173
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
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    detail.hit.zdb_id: 1461794-8
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  • 2
    Online Resource
    Online Resource
    Nitrososphaera viennensis , an ammonia oxidizing archaeon from soil
    Proceedings of the National Academy of Sciences ; 2011
    In:  Proceedings of the National Academy of Sciences Vol. 108, No. 20 ( 2011-05-17), p. 8420-8425
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 20 ( 2011-05-17), p. 8420-8425
    Abstract: Genes of archaea encoding homologues of ammonia monooxygenases have been found on a widespread basis and in large amounts in almost all terrestrial and marine environments, indicating that ammonia oxidizing archaea (AOA) might play a major role in nitrification on Earth. However, only one pure isolate of this group from a marine environment has so far been obtained, demonstrating archaeal ammonia oxidation coupled with autotrophic growth similar to the bacterial counterparts. Here we describe the cultivation and isolation of an AOA from soil. It grows on ammonia or urea as an energy source and is capable of using higher ammonia concentrations than the marine isolate, Nitrosopumilus maritimus . Surprisingly, although it is able to grow chemolithoautotrophically, considerable growth rates of this strain are obtained only upon addition of low amounts of pyruvate or when grown in coculture with bacteria. Our findings expand the recognized metabolic spectrum of AOA and help explain controversial results obtained in the past on the activity and carbon assimilation of these globally distributed organisms.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1013488108
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2011
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 3
    Online Resource
    Online Resource
    Stoichiometric model of the photosynthetic unit of Ectothiorhodospira halochloris
    Proceedings of the National Academy of Sciences ; 1986
    In:  Proceedings of the National Academy of Sciences Vol. 83, No. 23 ( 1986-12), p. 8972-8976
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 83, No. 23 ( 1986-12), p. 8972-8976
    Abstract: A stoichiometric model of the photosynthetic unit of Ectothiorhodospira halochloris has been obtained by means of scanning transmission electron microscope mass determination and mass mapping in conjunction with polyacrylamide gel electrophoresis. One reaction center, consisting of four single polypeptides, including one cytochrome, is surrounded by six identical light-harvesting complexes, each containing three polypeptides with 2:2:2 stoichiometry. This stoichiometric model was incorporated into the three-dimensional structure of the photosynthetic unit as derived from surface relief reconstructions of the two surfaces of shadowed membranes. The reaction center protrudes substantially from both membrane surfaces and has the cytochrome attached to the periplasmic face in a noncentrosymmetric fashion. The reaction center may assume various orientations within the photosynthetic complexes.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.83.23.8972
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1986
    detail.hit.zdb_id: 209104-5
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  • 4
    Online Resource
    Online Resource
    Controlled unzipping of a bacterial surface layer with atomic force microscopy
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 23 ( 1999-11-09), p. 13170-13174
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 23 ( 1999-11-09), p. 13170-13174
    Abstract: We have combined high-resolution atomic force microscopy (AFM) imaging and force spectroscopy to gain insight into the interaction forces between the individual protomers of the hexagonally packed intermediate (HPI) layer of Deinococcus radiodurans . After imaging the HPI layer, the AFM stylus was attached to individual protomers by enforced stylus-sample contact to allow force spectroscopy experiments. Imaging of the HPI layer after recording force-extension curves allowed adhesion forces to be correlated with structural alterations. By using this approach, individual protomers of the HPI layer were found to be removed at pulling forces of ≈300 pN. Furthermore, it was possible to sequentially unzip entire bacterial pores formed by six HPI protomers. The combination of high-resolution AFM imaging of individual proteins with the determination of their intramolecular forces is a method of studying the mechanical stability of supramolecular structures at the level of single molecules.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.23.13170
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
    detail.hit.zdb_id: 209104-5
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  • 5
    Online Resource
    Online Resource
    Arrhythmias, elicited by catecholamines and serotonin, vanish in human chronic atrial fibrillation
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 30 ( 2014-07-29), p. 11193-11198
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 30 ( 2014-07-29), p. 11193-11198
    Abstract: Atrial fibrillation (AF) is the most common heart rhythm disorder. Transient postoperative AF can be elicited by high sympathetic nervous system activity. Catecholamines and serotonin cause arrhythmias in atrial trabeculae from patients with sinus rhythm (SR), but whether these arrhythmias occur in patients with chronic AF is unknown. We compared the incidence of arrhythmic contractions caused by norepinephrine, epinephrine, serotonin, and forskolin in atrial trabeculae from patients with SR and patients with AF. In the patients with AF, arrhythmias were markedly reduced for the agonists and abolished for forskolin, whereas maximum inotropic responses were markedly blunted only for serotonin. Serotonin and forskolin produced spontaneous diastolic Ca 2+ releases in atrial myocytes from the patients with SR that were abolished or reduced in myocytes from the patients with AF. For matching L-type Ca 2+ -current (I Ca,L ) responses, serotonin required and produced ∼100-fold less cAMP/PKA at the Ca 2+ channel domain compared with the catecholamines and forskolin. Norepinephrine-evoked I Ca,L responses were decreased by inhibition of Ca 2+ /calmodulin-dependent kinase II (CaMKII) in myocytes from patients with SR, but not in those from patients with AF. Agonist-evoked phosphorylation by CaMKII at phospholamban (Thr-17), but not of ryanodine2 (Ser-2814), was reduced in trabeculae from patients with AF. The decreased CaMKII activity may contribute to the blunting of agonist-evoked arrhythmias in the atrial myocardium of patients with AF.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1324132111
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
    detail.hit.zdb_id: 209104-5
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  • 6
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    Online Resource
    Synchronization of oscillatory responses in visual cortex correlates with perception in interocular rivalry
    Proceedings of the National Academy of Sciences ; 1997
    In:  Proceedings of the National Academy of Sciences Vol. 94, No. 23 ( 1997-11-11), p. 12699-12704
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 94, No. 23 ( 1997-11-11), p. 12699-12704
    Abstract: In subjects suffering from early onset strabismus, signals conveyed by the two eyes are not perceived simultaneously but in alternation. We exploited this phenomenon of interocular suppression to investigate the neuronal correlate of binocular rivalry in primary visual cortex of awake strabismic cats. Monocularly presented stimuli that were readily perceived by the animal evoked synchronized discharges with an oscillatory patterning in the γ-frequency range. Upon dichoptic stimulation, neurons responding to the stimulus that continued to be perceived increased the synchronicity and the regularity of their oscillatory patterning while the reverse was true for neurons responding to the stimulus that was no longer perceived. These differential changes were not associated with modifications of discharge rate, suggesting that at early stages of visual processing the degree of synchronicity rather than the amplitude of responses determines which signals are perceived and control behavioral responses.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.94.23.12699
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1997
    detail.hit.zdb_id: 209104-5
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  • 7
    Online Resource
    Online Resource
    Mitochondrial Lon of Saccharomyces cerevisiae is a ring-shaped protease with seven flexible subunits
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 12 ( 1999-06-08), p. 6787-6790
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 12 ( 1999-06-08), p. 6787-6790
    Abstract: Lon (or La) is a soluble, homooligomeric ATP-dependent protease. Mass determination and cryoelectron microscopy of pure mitochondrial Lon from Saccharomyces cerevisiae identify Lon as a flexible ring-shaped heptamer. In the presence of ATP or 5′-adenylylimidodiphosphate, most of the rings are symmetric and resemble other ATP-driven machines that mediate folding and degradation of proteins. In the absence of nucleotides, most of the rings are distorted, with two adjacent subunits forming leg-like protrusions. These results suggest that asymmetric conformational changes serve to power processive unfolding and translocation of substrates to the active site of the Lon protease.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.12.6787
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
    detail.hit.zdb_id: 209104-5
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  • 8
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    Online Resource
    Temporal evolution of beta bursts in the parkinsonian cortical and basal ganglia network
    Proceedings of the National Academy of Sciences ; 2019
    In:  Proceedings of the National Academy of Sciences Vol. 116, No. 32 ( 2019-08-06), p. 16095-16104
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 32 ( 2019-08-06), p. 16095-16104
    Abstract: Beta frequency oscillations (15 to 35 Hz) in cortical and basal ganglia circuits become abnormally synchronized in Parkinson’s disease (PD). How excessive beta oscillations emerge in these circuits is unclear. We addressed this issue by defining the firing properties of basal ganglia neurons around the emergence of cortical beta bursts (β bursts), transient (50 to 350 ms) increases in the beta amplitude of cortical signals. In PD patients, the phase locking of background spiking activity in the subthalamic nucleus (STN) to frontal electroencephalograms preceded the onset and followed the temporal profile of cortical β bursts, with conditions of synchronization consistent within and across bursts. Neuronal ensemble recordings in multiple basal ganglia structures of parkinsonian rats revealed that these dynamics were recapitulated in STN, but also in external globus pallidus and striatum. The onset of consistent phase-locking conditions was preceded by abrupt phase slips between cortical and basal ganglia ensemble signals. Single-unit recordings demonstrated that ensemble-level properties of synchronization were not underlain by changes in firing rate but, rather, by the timing of action potentials in relation to cortical oscillation phase. Notably, the preferred angle of phase-locked action potential firing in each basal ganglia structure was shifted during burst initiation, then maintained stable phase relations during the burst. Subthalamic, pallidal, and striatal neurons engaged and disengaged with cortical β bursts to different extents and timings. The temporal evolution of cortical and basal ganglia synchronization is cell type-selective, which could be key for the generation/ maintenance of excessive beta oscillations in parkinsonism.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1819975116
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 209104-5
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  • 9
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    Online Resource
    Prediction of human errors by maladaptive changes in event-related brain networks
    Proceedings of the National Academy of Sciences ; 2008
    In:  Proceedings of the National Academy of Sciences Vol. 105, No. 16 ( 2008-04-22), p. 6173-6178
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 105, No. 16 ( 2008-04-22), p. 6173-6178
    Abstract: Humans engaged in monotonous tasks are susceptible to occasional errors that may lead to serious consequences, but little is known about brain activity patterns preceding errors. Using functional MRI and applying independent component analysis followed by deconvolution of hemodynamic responses, we studied error preceding brain activity on a trial-by-trial basis. We found a set of brain regions in which the temporal evolution of activation predicted performance errors. These maladaptive brain activity changes started to evolve ≈30 sec before the error. In particular, a coincident decrease of deactivation in default mode regions of the brain, together with a decline of activation in regions associated with maintaining task effort, raised the probability of future errors. Our findings provide insights into the brain network dynamics preceding human performance errors and suggest that monitoring of the identified precursor states may help in avoiding human errors in critical real-world situations.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0708965105
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2008
    detail.hit.zdb_id: 209104-5
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  • 10
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    Increased functional connectivity indicates the severity of cognitive impairment in multiple sclerosis
    Proceedings of the National Academy of Sciences ; 2011
    In:  Proceedings of the National Academy of Sciences Vol. 108, No. 47 ( 2011-11-22), p. 19066-19071
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 47 ( 2011-11-22), p. 19066-19071
    Abstract: Correlations in spontaneous brain activity provide powerful access to large-scale organizational principles of the CNS. However, making inferences about cognitive processes requires a detailed understanding of the link between these couplings and the structural integrity of the CNS. We studied the impact of multiple sclerosis, which leads to the severe disintegration of the central white matter, on functional connectivity patterns in spontaneous cortical activity. Using a data driven approach based on the strength of a salient pattern of cognitive pathology, we identified distinct networks that exhibit increases in functional connectivity despite the presence of strong and diffuse reductions of the central white-matter integrity. The default mode network emerged as a core target of these connectivity modulations, showing enhanced functional coupling in bilateral inferior parietal cortex, posterior cingulate, and medial prefrontal cortex. These findings imply a complex and diverging relation of anatomical and functional connectivity in early multiple sclerosis and, thus, add an important observation for understanding how cognitive abilities and CNS integrity may be reflected in the intrinsic covariance of functional signals.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1110024108
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2011
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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