546 research outputs found
Electrostatic contributions to the kinetics and thermodynamics of protein assembly.
No full textThe role of electrostatic interactions in the assembly of a native protein structure was studied using fragment complementation. Contributions of salt, pH, or surface charges to the kinetics and equilibrium of calbindin D(9k) reconstitution was measured in the presence of Ca(2+) using surface plasmon resonance and isothermal titration calorimetry. Whereas surface charge substitutions primarily affect the dissociation rate constant, the association rates are correlated with subdomain net charge in a way expected for Coulomb interactions. The affinity is reduced in all mutants, with the largest effect (260-fold) observed for the double mutant K25E+K29E. At low net charge, detailed charge distribution is important, and charges remote from the partner EF-hand have less influence than close ones. The effects of salt and pH on the reconstitution are smaller than mutational effects. The interaction between the wild-type EF-hands occurs with high affinity (K(A) = 1.3 x 10(10) M(-1); K(D) = 80 pM). The enthalpy of association is overall favorable and there appears to be a very large favorable entropic contribution from the desolvation of hydrophobic surfaces that become buried in the complex. Electrostatic interactions contribute significantly to the affinity between the subdomains, but other factors, such as hydrophobic interactions, dominate
A reassessment of the distribution of the common Antarctic scallop Adamussium colbecki (Smith, 1902)
No full textK. v. Brudzewski: Wo ist der wirkliche Brennpunkt einer Linse? Klinische Monatsbl. f. Augenheilk. 38, 671-676. 1900
No full textK. V. BRUDZEWSKI: WO IST DER WIRKLICHE BRENNPUNKT EINER LINSE? KLINISCHE MONATSBL. F. AUGENHEILK. 38, 671-676. 1900
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (-)
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (25) (a0005)
K. v. Brudzewski: Wo ist der wirkliche Brennpunkt einer Linse? Klinische Monatsbl. f. Augenheilk. 38, 671-676. 1900 (25) (p0253
K. Bjerke: Über die Berechnung des Brechwertes der Linse nach Myopieoperationen. v. Graefes Archiv f. Ophthalm. 55 (3), 389-413
No full textK. BJERKE: ÜBER DIE BERECHNUNG DES BRECHWERTES DER LINSE NACH MYOPIEOPERATIONEN. V. GRAEFES ARCHIV F. OPHTHALM. 55 (3), 389-413
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (-)
Zeitschrift für Psychologie und Physiologie der Sinnesorgane (33) (a0001)
K. Bjerke: Über die Berechnung des Brechwertes der Linse nach Myopieoperationen. v. Graefes Archiv f. Ophthalm. 55 (3), 389-413 (33) (p0364
Differential adaptations between cold-stenothermal environments in the bivalve Lissarca cf. miliaris (Philobryidae) from the Scotia Sea islands and Antarctic Peninsula
No full textThe cold stenothermal nature of the Southern Ocean, and highly adapted fauna living within, raises the question of how much intra-specific variation there is among invertebrate populations, and how variation may have a role in speciation processes through ecological divergence, natural selection, and reproductive isolation. Despite decades of collecting biological material, this question remains largely unanswered, and many studies compare ‘populations’ of pooled material from wide geographic ranges to compensate for sampling constraints. In this study, variations in ecophysiological traits are explored by measuring growth, reproduction, and shell morphology among six populations of the small bivalve Lissarca cf. miliaris (Philippi, 1845) from the Southern Ocean, which experience subtle differences in temperature, disturbance, and food availability. There are significant differences in shell morphology and growth among different populations and slower growth rates at higher latitude populations. Prodissoconch sizes show an inverse ‘U’ shaped relationship with latitude, and are correlated with egg size at South Georgia and King George Island’s Potter Cove. Higher brood sizes at the South Georgia population represent a trade-off with lower egg size, and correlate with shell morphology by offering lower internal capacity to brood young. Lower investment into offspring and morphological variations in Lissarca cf. miliaris highlight the importance of local scale environmental variations on species’ ecology. These variations in physical traits appear to be underestimated in the Southern Ocean, but may be important drivers of ecological divergence and speciation, which should be considered in future genetic investigations on different invertebrate populations
Taxonomic composition and microdistribution of fauna on a natural whale fall at 1400 m depth in the Southern Ocean
No full text
Plasticity in shell morphology and growth among deep-sea protobranch bivalves of the genus Yoldiella (Yoldiidae) from contrasting Southern Ocean regions
No full textThe ecology of Antarctic deep-sea fauna is poorly understood and few studies have gone beyond assessing biodiversity when comparing deep regions of the Southern Ocean. Protobranch bivalves are ubiquitous in the deep ocean and are widely distributed in the Southern Ocean. This paper examines the potential respon ses to environmental differences in the common protobranchs Yoldiella valettei, Yoldiella ecaudata, and Yoldiella sabrina from contrasting deep-sea environments of the Weddell Sea, Scotia Sea, Amundsen Sea, and South Atlantic. There are significant differences in morphology between deep-sea regions in all species and a significant difference in shell weight in Y. valettei between the Amundsen Sea and Weddell Seas. Growth rates of Y. valettei and Y. ecaudata in the Amundsen Sea are also higher than elsewhere and Y. valettei have heaviest shells in the Amundsen Sea, suggesting more favourable conditions for calcification and growth. The plasticity observed among deep-sea regions in the Southern Ocean is likely to be driven by different oceanographic influences affecting temperature and food fluxes to the benthos, and demonstrate the species’ ability to differentially adapt between cold-stenothermal environments. This study suggests that subtle changes in the environment may lead to a divergence in the ecology of invertebrate populations and showcases the protobranch bivalves as a future model group for the study of speciation and radiation processes through cold-stenothermal environments
Reproductive morphology of the deep-sea protobranch bivalves Yoldiella ecaudata, Yoldiella sabrina, and Yoldiella valettei (Yoldiidae) from the Southern Ocean
No full textThe protobranch bivalves of the Southern Ocean are poorly understood ecologically, despite their high abundances in soft sediments from the shelf to the deep sea. The subclass has a long evolutionary history predating the formation of the polar front, and knowledge of their reproductive biology is key to understanding better their successful radiation into the Southern Ocean, and within deep-sea basins. In this study, we for the first time investigate the reproductive morphology of three deep-water protobranchs; Yoldiella ecaudata from 500 m in the Amundsen Sea; Y. sabrina from between 200 and 4,730 m in the Amundsen Sea, Scotia Sea, and South Atlantic; and Y. valettei from 1,000 m in the Scotia Sea. All three species demonstrate evidence of lecithotrophic larval development with maximum oocyte size of 130.4, 187.9, and 120.6 µm in Y. ecaudata, Y. sabrina, and Y. valettei, respectively, further supported by prodissoconch I measurements. There is evidence for simultaneous hermaphroditism in Y. valettei. Asynchronous oocyte development within specimens of Y. ecaudata and Y. valettei is described, and also between populations of Y. sabrina separated by depth. The reproductive characteristics, comparable to those of North Atlantic deep-sea protobranch species, are discussed in the context of the cold thermally stable conditions prevailing on the deep-Antarctic continental shelf and deep sea. The requirement for reclassification of this complex subclass is also discussed in relation to observed soft anatomy and shell characteristics
Dynamics of Conformational Ca2+-Switches in Signaling Networks Detected by a Planar Plasmonic Device
No full textCa2+-sensor proteins regulate a variety of intracellular processes by adopting specific conformations in response to finely tuned changes in Ca2+-concentration. Here we present a surface plasmon resonance (SPR)-based approach, which allows for simultaneous detection of conformational dynamics of four Ca2+-sensor proteins (calmodulin, recoverin, GCAP1, and GCAP2) operating in the vertebrate phototransduction cascade, over variations in Ca2+ concentration in the 0.1-0.6 mu M range. By working at conditions that quantitatively mimic those found in the cell, we show that the method is able to detect subtle differences in the dynamics of each Ca2+-sensor, which appear to be influenced by the presence of free Mg2+ at physiological concentration and by posttranslational modifications such as myristoylation. Comparison between the macroscopic Ca2+-binding constants, directly measured by competition with a chromophoric chelator, and the concerted binding-conformational switch detected by SPR at equilibrium reveals the relative contribution of the conformational change process to the SPR signal. This process appears to be influenced by the presence of other cations that perturb Ca2+-binding and the conformational transition by competing with Ca2+, or by pure electrostatic screening. In conclusion, the approach described here allows a comparative analysis of protein conformational changes occurring under physiologically relevant molecular crowding conditions in ultrathin biosensor layers
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