Search results for "Spider"
showing 10 items of 97 documents
Population history in social spiders repeated: colony structure and lineage evolution inStegodyphus mimosarum(Eresidae)
2009
Social cooperative spiders from diverse taxonomic families share life-history and demographic traits, including highly inbred colony structure. The combination of traits suggests constrained pathways for social evolution in spiders. The genus Stegodyphus has three independently evolved social species, which can be used as replicate samples to analyse population constraints in evolutionary time. We tested colony structure and population history of the social S. mimosarum from South and East Africa using mitochondrial DNA variation, and we compared the results to published data for the independently evolved social congener S. dumicola. S. mimosarum had many and diverse haplotypes (5-7% sequen…
High-yield Production of Amyloid-β Peptide Enabled by a Customized Spider Silk Domain
2020
AbstractDuring storage in the silk gland, the N-terminal domain (NT) of spider silk proteins (spidroins) keeps the aggregation-prone repetitive region in solution at extreme concentrations. We observe that NTs from different spidroins have co-evolved with their respective repeat region, and now use an NT that is distantly related to previously used NTs, for efficient recombinant production of the amyloid-β peptide (Aβ) implicated in Alzheimer’s disease. A designed variant of NT from Nephila clavipes flagelliform spidroin, which in nature allows production and storage of β-hairpin repeat segments, gives exceptionally high yields of different human Aβ variants as a solubility tag. This tool e…
Hemocyanin from E. californicum encapsulated in silica gels: oxygen binding and conformational states.
2007
Cooperativity depends on the existence of equilibria among functionally distinct conformational states that are affected by homo and heterotropic effectors. In order to isolate the quaternary conformations of hemocyanin from E. californicum, the 24-meric giant protein was encapsulated in wet, nanoporous silica gels, either in the absence or presence of oxygen. The deoxy- and oxy-hemocyanin gels exhibit a p50 for oxygen of 11 and 2.5 torr, respectively, values in close agreement with those for hemocyanin in solution. The observed Hill coefficients are lower than unity, indicating a conformational heterogeneity within each locked conformational state, a finding in agreement with the assumptio…
All hierarchical levels are involved in conformational transitions of the 4×6-meric tarantula hemocyanin upon oxygenation
2002
The respiratory protein of the tarantula Eurypelma californicum is a 4 x 6-meric hemocyanin that binds oxygen with high cooperativity. This requires the existence of different conformations which have been confirmed by small angle X-ray scattering (SAXS). Here we present reconstructed 3D-models of the oxy- and deoxy-forms of tarantula hemocyanins, as obtained by fitting small angle X-rays scattering curves on the basis of known X-ray structures and electron microscopy of related hemocyanins. For the first time, the involvement of movements at all levels of the quaternary structure was confirmed for an arthropod hemocyanin upon oxygenation. The two identical 2 x 6-meric half-molecules of the…
Tarantula Hemocyanin Shows Phenoloxidase Activity
1998
An enzyme generally catalyzes one well defined reaction with high specificity and efficiency. We report here in contrast that the copper protein hemocyanin of the tarantula Eurypelma californicum exhibits two different functions. These occur at the same active site. While hemocyanin usually is an oxygen carrier, its function can be transformed totally to monophenoloxidase and o-diphenoloxidase activity after limited proteolysis with trypsin or chymotrypsin. N-acetyldopamine (NADA) is more effectively oxidized than L-dopa or dopamine. This irreversible functional switch of tarantula hemocyanin function is limited to the two subunits b and c of its seven subunit types. A conserved phenylalani…
Eresus kollari (Araneae: Eresidae) calls for heathland management
2011
Northwest Europe’s largest heather-dominated sandy habitats are located in the nature reserve Lu¨neburgerHeide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as theladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of thesespecies. The habitat requirements of this endangered spider species were investigated in order to obtain data that will helpstabilize the last remnants of the species’ population in northwest Germany. Several heathland habitats were surveyed bypitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic reg…
Gluing the ‘unwettable’: soil-dwelling harvestmen use viscoelastic fluids for capturing springtails
2014
Gluing can be a highly efficient mechanism of prey capture, as it should require less complex sensory–muscular feedback. Whereas it is well known in insects, this mechanism is much less studied in arachnids, except spiders. Soil-dwelling harvestmen (Opiliones, Nemastomatidae) bear drumstick-like glandular hairs (clavate setae) at their pedipalps, which were previously hypothesized to be sticky and used in prey capture. However, clear evidence for this was lacking to date. Using high-speed videography, we found that the harvestman Mitostoma chrysomelas was able to capture fast-moving springtails (Collembola) just by a slight touch of the pedipalp. Adhesion of single clavate setae increased p…
Air Pollution Research Based on Spider Web and Parallel Continuous Particulate Monitoring—A Comparison Study Coupled with Identification of Sources
2021
Air pollution is monitored mainly in urban or industrial areas, even if it is known that in rural ones, low emission can significantly worsen air quality. Hence, cheap and easily accessible methods of monitoring are needed. Recently, spider webs biomonitoring is getting popular, however, there is no information about its comparison with active methods. In this study, PTEs accumulated on spider webs were compared with results from continuous particulate monitor (CPM). Generally, higher potentially toxic elements concentrations were noted in spider web, with exception in the case of Zn. Zn may be present rather in smaller fractions, hence it needs more time for accumulation on spider web whil…
Small-angle X-ray scattering reveals differences between the quaternary structures of oxygenated and deoxygenated tarantula hemocyanin
1996
Small-angle X-ray scattering (SAXS) curves have been recorded for the oxygenated and deoxygenated states of the 4 x 6-meric hemocyanin from the tarantula Eurypelma californicum. A comparison of the curves shows that the quaternary structures of the two states are different by three criteria, which all indicate that the hemocyanin is less compact in the oxygenated compared to the deoxygenated form: (a) The radius of gyration is 8.65 +/- 0.05 nm for the deoxy- and 8.80 +/- 0.05 nm for the oxy-form. (b) The maximum particle dimension amounts to 25.0 +/- 0.5 nm for the deoxy- and to 27.0 +/- 0.5 nm for the oxy-form. (c) A dip in the intramolecular distance distribution function p(r) is more pro…
Bohr-effect and buffering capacity of hemocyanin from the tarantula E. californicum.
2003
A previous report showed that binding of oxygen to the 24-meric hemocyanin from E. californicum does not correlate linearly with the release of protons as known from hemoglobin. However, this unusual complex phenomenological observation could not be explained at that time. Here, I present a full analysis of the thermodynamic coupling between protons and oxygen for the 24-meric tarantula hemocyanin in Ringer-solution based on the Nested-MWC-model. A strategy is presented which allows to reduce the number of free parameters when fitting the model to the data by including explicitly the equilibrium constants for binding of protons to the different conformations. The results show that the Neste…