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171.
Trey K. Sato Mary Tremaine Lucas S. Parreiras Alexander S. Hebert Kevin S. Myers Alan J. Higbee Maria Sardi Sean J. McIlwain Irene M. Ong Rebecca J. Breuer Ragothaman Avanasi Narasimhan Mick A. McGee Quinn Dickinson Alex La Reau Dan Xie Mingyuan Tian Jeff S. Piotrowski Jennifer L. Reed Yaoping Zhang Joshua J. Coon Chris Todd Hittinger Audrey P. Gasch Robert Landick 《PLoS genetics》2016,12(11)
172.
Roche C. de Guzman Shanel M. Tsuda Minh-Thi N. Ton Xiao Zhang Alan R. Esker Mark E. Van Dyke 《PloS one》2015,10(8)
Hair-derived keratin biomaterials composed mostly of reduced keratin proteins (kerateines) have demonstrated their utility as carriers of biologics and drugs for tissue engineering. Electrostatic forces between negatively-charged keratins and biologic macromolecules allow for effective drug retention; attraction to positively-charged growth factors like bone morphogenetic protein 2 (BMP-2) has been used as a strategy for osteoinduction. In this study, the intermolecular surface and bulk interaction properties of kerateines were investigated. Thiol-rich kerateines were chemisorbed onto gold substrates to form an irreversible 2-nm rigid layer for surface plasmon resonance analysis. Kerateine-to-kerateine cohesion was observed in pH-neutral water with an equilibrium dissociation constant (KD) of 1.8 × 10−4 M, indicating that non-coulombic attractive forces (i.e. hydrophobic and van der Waals) were at work. The association of BMP-2 to kerateine was found to be greater (KD = 1.1 × 10−7 M), within the range of specific binding. Addition of salts (phosphate-buffered saline; PBS) shortened the Debye length or the electrostatic field influence which weakened the kerateine-BMP-2 binding (KD = 3.2 × 10−5 M). BMP-2 in bulk kerateine gels provided a limited release in PBS (~ 10% dissociation in 4 weeks), suggesting that electrostatic intermolecular attraction was significant to retain BMP-2 within the keratin matrix. Complete dissociation between kerateine and BMP-2 occurred when the PBS pH was lowered (to 4.5), below the keratin isoelectric point of 5.3. This phenomenon can be attributed to the protonation of keratin at a lower pH, leading to positive-positive repulsion. Therefore, the dynamics of kerateine-BMP-2 binding is highly dependent on pH and salt concentration, as well as on BMP-2 solubility at different pH and molarity. The study findings may contribute to our understanding of the release kinetics of drugs from keratin biomaterials and allow for the development of better, more clinically relevant BMP-2-conjugated systems for bone repair and regeneration. 相似文献
173.
174.
Melissa B. Rooney Michael J. Honeychurch Fabiola M. Selvaraj Robert E. Blankenship Alan M. Bond Hans C. Freeman 《Journal of biological inorganic chemistry》2003,8(3):306-317
The reversible formal potentials of auracyanin A and auracyanin B, two closely related "blue" copper proteins from the photosynthetic bacterium Chloroflexus aurantiacus, have been determined by protein film voltammetry in the range 4相似文献
175.
Alexander F. Arendsen Jonathan Hadden Graeme Card Alan S. McAlpine Susan Bailey Vjacheslav Zaitsev Elizabeth H. M. Duke P. F. Lindley Monika Kröckel Alfred X. Trautwein Martinus C. Feiters John M. Charnock C. David Garner Sophie J. Marritt Andrew J. Thomson Ingeborg M. Kooter Michael K. Johnson Willy A. M. van den Berg Walter M. A. M. van Dongen W. R. Hagen 《Journal of biological inorganic chemistry》1998,3(1):81-95
The three-dimensional structure of the native "putative prismane" protein from Desulfovibrio vulgaris (Hildenborough) has been solved by X-ray crystallography to a resolution of 1.72?Å. The molecule does not contain a [6Fe-6S] prismane cluster, but rather two 4Fe clusters some 12?Å apart and situated close to the interfaces formed by the three domains of the protein. Cluster 1 is a conventional [4Fe-4S] cubane bound, however, near the N-terminus by an unusual, sequential arrangement of four cysteine residues (Cys 3, 6, 15, 21). Cluster 2 is a novel 4Fe structure with two μ2-sulfido bridges, two μ2-oxo bridges, and a partially occupied, unidentified μ2 bridge X. The protein ligands of cluster 2 are widely scattered through the second half of the sequence and include three cysteine residues (Cys 312, 434, 459), one persulfido-cysteine (Cys 406), two glutamates (Glu 268, 494), and one histidine (His 244). With this unusual mixture of bridging and external type of ligands, cluster 2 is named the "hybrid" cluster, and its asymmetric, open structure suggests that it could be the site of a catalytic activity. X-ray absorption spectroscopy at the Fe K-edge is readily interpretable in terms of the crystallographic model when allowance is made for volume contraction at 10?K; no Fe··Fe distances beyond 3.1?Å could be identified. EPR, Mössbauer and MCD spectroscopy have been used to define the oxidation states and the magnetism of the clusters in relation to the crystallographic structure. Reduced cluster 1 is a [4Fe-4S]1+ cubane with S?=?3/2; it is the first biological example of a "spin-admixed" iron-sulfur cluster. The hybrid cluster 2 has four oxidation states from (formally) all FeIII to three FeII plus one FeIII. The four iron ions are exchange coupled resulting in the system spins S?=?0, 9/2, 0 (and 4), 1/2, respectively, for the four redox states. Resonance Raman spectroscopy suggests that the bridging ligand X which could not be identified unambiguously in the crystal structure is a solvent-exchangeable oxygen. 相似文献
176.
Sequence-specific protein-nucleic acid recognition is determined, in part, by hydrogen bonding interactions between amino acid side-chains and nucleotide bases. To examine the repertoire of possible interactions, we have calculated geometrically plausible arrangements in which amino acids hydrogen bond to unpaired bases, such as those found in RNA bulges and loops, or to the 53 possible RNA base-pairs. We find 32 possible interactions that involve two or more hydrogen bonds to the six unpaired bases (including protonated A and C), 17 of which have been observed. We find 186 "spanning" interactions to base-pairs in which the amino acid hydrogen bonds to both bases, in principle allowing particular base-pairs to be selectively targeted, and nine of these have been observed. Four calculated interactions span the Watson-Crick pairs and 15 span the G:U wobble pair, including two interesting arrangements with three hydrogen bonds to the Arg guanidinum group that have not yet been observed. The inherent donor-acceptor arrangements of the bases support many possible interactions to Asn (or Gln) and Ser (or Thr or Tyr), few interactions to Asp (or Glu) even though several already have been observed, and interactions to U (or T) only if the base is in an unpaired context, as also observed in several cases. This study highlights how complementary arrangements of donors and acceptors can contribute to base-specific recognition of RNA, predicts interactions not yet observed, and provides tools to analyze proposed contacts or design novel interactions. 相似文献
177.
We examined patterns of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) loading to a small urban stream
during baseflow and stormflow. We hypothesized that lower DOC and TDN contributions from impervious surfaces would dilute
natural hydrologic flowpath (i.e., riparian) contributions during storm events in an urban watershed, resulting in lower concentrations
of DOC and TDN during storms. We tested these hypotheses in a small urban watershed in Portland, Oregon, over a 3-month period
during the spring of 2003. We compared baseflow and stormflow chemistry using Mann–Whitney tests (significant at p<0.05). We also applied a mass balance to the stream to compare the relative significance of impervious surface contributions
versus riparian contributions of DOC and TDN. Results showed a significant increase in stream DOC concentrations during stormflows
(median baseflow DOC = 2.00 mg l−1 vs. median stormflow DOC = 3.46 mg l−1). TDN streamwater concentrations, however, significantly decreased with stormflow (median baseflow TDN = 0.75 mg l−1 vs. median stormflow TDN = 0.56 mg l−1). During storms, remnant riparian areas contributed 70–74% of DOC export and 38–35% of TDN export to the stream. The observed
pattern of increased DOC concentrations during stormflows in this urban watershed was similar to patterns found in previous
studies of forested watersheds. Results for TDN indicated that there were relatively high baseflow nitrogen concentrations
in the lower watershed that may have partially masked the remnant riparian signal during stormflows. Remnant riparian areas
were a major source of DOC and TDN to the stream during storms. These results suggest the importance of preserving near-stream
riparian areas in cities to maintain ambient carbon and nitrogen source contributions to urban streams. 相似文献
178.
Michael M?ller Alan Forrest Yi-Gang Wei Anton Weber 《Plant Systematics and Evolution》2011,292(3-4):223-248
Based on a considerably enlarged sampling, a phylogenetic analysis of the largest group of didymocarpoid Gesneriaceae, the ??advanced Asiatic and Malesian genera??, was performed, covering all but 3 of the 60 genera presently recognised in this group (20 of these, mostly from China, are monotypic). The results suggest that no fewer than 17 out of the 57 genera examined are poly- (or rarely para-)phyletic. Highly polyphyletic are Briggsia, Chirita, Henckelia and Raphiocarpus. Only a dozen of the non-monotypic genera (including the three species-richest genera, Cyrtandra, Aeschynanthus and Agalmyla) are confirmed as monophyletic entities, though some exhibit considerable genetic variation. For eight genera, no statement can be made, as only one (of two or several) species was included in the analysis. For a dozen of the (particularly Chinese) monotypic genera a close relationship (or possible congenerity) with other genera was found. In China, only Allostigma, Cathayanthe, Conandron and Metapetrocosmea seem to have no strong affinities to other genera, indicating that they represent phylogenetically isolated lineages or represent remnants of previously larger and earlier diversified groups. The present study forms the foundation for targeted molecular, morphological and phytogeographic studies of the polyphyletic and monotypic genera and particular of clades of genera with interrelations uncovered here for the first time. 相似文献
179.
180.
Combinatorial actions of bacterial effectors revealed by exploiting genetic tools in yeast 下载免费PDF全文
Alan Huett 《Molecular systems biology》2017,13(1)
While yeast has been extensively used as a model system for analysing protein–protein and genetic interactions, in the context of bacterial pathogenesis, the use of yeast‐based tools has largely been limited to identifying interactions between pathogen effectors and host targets. In their recent work, Ensminger and colleagues (Urbanus et al, 2016 ) use the combinatorial power of yeast genetics to systematically screen all known Legionella pneumophila effector proteins for effector–effector interactions. They provide new insights into how bacterial effectors balance host cell perturbation and describe mechanisms used by “meta‐effectors” to directly modulate target effector activity. 相似文献