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This chapter will give a brief review about the present understanding of pores in tests of benthic foraminifera. The interpretation of the pore function changed through time, and a couple of theories were proposed. The research about the functionality of pores recently became of new interest because it seems likely that they are involved in the respiration pathways of some benthic foraminifera. The fact that several benthic species are able to survive anoxia points out the importance for a better understanding of these respiration pathways and which adaptions differentiate these species from species which cannot survive in oxygen-depleted habitats. Nitrate respiration seems to be widespread among foraminifera from oxygen-depleted habitats, and thus knowledge if and in how far the pores are involved in the process of denitrification would help to understand the process of denitrification in eukaryotic foraminiferal cells.

Recent benthic foraminifera and their distribution in surface sediments were studied on a transect through the Peruvian oxygen minimum zone (OMZ) between 10 and 12°S. The OMZ with its steep gradients of oxygen concentrations allows determinations of the oxygen-dependent changes of species compositions in a relatively small area. Our results from sediments of 13 multicorer stations from 79 to 823 m water depth demonstrate that calcareous species, especially bolivinids, dominate the assemblages throughout the OMZ. The depth distribution of several species matches distinct ranges of bottom water oxygen levels. The distribution pattern inferred a proxy which allows estimating dissolved oxygen concentrations for reconstructing oxygen levels in the geological past.

Modeling and proxy studies indicate that a reduction of Atlantic Meridional Overturning Circulation (AMOC) strength profoundly impacts temperatures and salinities in the (sub)tropical Atlantic, especially on subsurface levels. While previous studies focused on prominent periods of AMOC reduction during the last deglaciation, we aim to test whether similar reconfigurations of the subtropical hydrography occurred during the moderate climatic alterations punctuating the last interglacial Marine Isotope Stage (MIS) 5. Here, we present temperature and salinity records from a Florida Straits core by combining d18O and Mg/Ca analyses on surface (Globigerinoides ruber, white) and deep‐dwelling (Globorotalia crassaformis) foraminifera covering MIS 5 in high resolution. The data reveal increasing salinities at intermediate depths during interglacial cooling episodes, decoupled from relatively stable surface conditions. This probably indicates the spatial expansion of saline subtropical gyre waters due to enhanced Ekman downwelling and might also point to a changed density structure and altered geostrophic balance in Florida Straits. Notably, these oceanographic alterations are not consistently occurring during periods of AMOC reduction. The data suggest that the expansion of gyre waters into Florida Straits was impeded by the increasing influence of Antarctic Intermediate Water (AAIW) from MIS 5.5 to ∼107 kyr BP. Afterward, increasingly positive benthic d13C values imply a recession of AAIW, allowing the temporary expansion of gyre waters into Florida Straits. We argue that the inferred transient subtropical salt accumulation and warm pool expansion might have played a pivotal role in reinvigorating meridional overturning and dampen the severity of interglacial cold phases.

Culturing experiments were performed with the benthic foraminifer Ammonia aomo - riensis from Flensburg Fjord, western Baltic Sea. The experiments simulated a projected rise in atmospheric CO2 concentrations. We exposed specimens to 5 seawater pCO2 levels ranging from 618 μatm (pH 7.9) to 3130 μatm (pH 7.2) for 6 wk. Growth rates and mortality differed significantly among pCO2 treatments. The highest increase of mean test diameter (19%) was observed at 618 μatm. At partial pressures >1829 μatm, the mean test diameter was observed to decrease, by up to 22% at 3130 μatm. At pCO2 levels of 618 and 751 μatm, A. aomoriensis tests were found intact after the experiment. The outer chambers of specimens incubated at 929 and 1829 μatm were severely damaged by corrosion. Visual inspection of specimens incubated at 3130 μatm revealed wall dissolution of all outer chambers, only their inner organic lining stayed intact. Our results demonstrate that pCO2 values of ≥929 μatm in Baltic Sea waters cause reduced growth of A. aomoriensis and lead to shell dissolution. The bottom waters in Flensburg Fjord and adjacent areas regularly experience pCO2 levels in this range during summer and fall. Increasing atmospheric CO2 concentrations are likely to extend and intensify these periods of undersaturation. This may eventually slow down calcification in A. aomoriensis to the extent that net carbonate precipitation terminates. The possible disappearance of this species from the Baltic Sea and other areas prone to seasonal undersaturation would likely cause significant shifts in shallow-water benthic ecosystems in the near future.

The Atlantic-Mediterranean exchange of water at Gibraltar represents a significant heat and freshwater sink for the North Atlantic and is a major control on the heat, salt and freshwater budgets of the Mediterranean Sea. Consequently, an understanding of the response of the exchange system to external changes is vital to a full comprehension of the hydrographic responses in both ocean basins. Here, we use a synthesis of empirical (oxygen isotope, planktonic foraminiferal assemblage) and modeling (analytical and general circulation) approaches to investigate the response of the Gibraltar Exchange system to Atlantic freshening during Heinrich Stadials (HSs). HSs display relatively flat W–E surface hydrographic gradients more comparable to the Late Holocene than the Last Glacial Maximum. This is significant, as it implies a similar state of surface circulation during these periods and a different state during the Last Glacial Maximum. During HS1, the gradient may have collapsed altogether, implying very strong water column stratification and a single thermal and δ18Owater condition in surface water extending from southern Portugal to the eastern Alboran Sea. Together, these observations imply that inflow of Atlantic water into the Mediterranean was significantly increased during HS periods compared to background glacial conditions. Modeling efforts confirm that this is a predictable consequence of freshening North Atlantic surface water with iceberg meltwater and indicate that the enhanced exchange condition would last until the cessation of anomalous freshwater supply into to the northern North Atlantic. The close coupling of dynamics at Gibraltar Exchange with the Atlantic freshwater system provides an explanation for observations of increased Mediterranean Outflow activity during HS periods and also during the last deglaciation. This coupling is also significant to global ocean dynamics, as it causes density enhancement of the Atlantic water column via the Gibraltar Exchange to be inversely related to North Atlantic surface salinity. Consequently, Mediterranean enhancement of the Atlantic Meridional Overturning Circulation will be greatest when the overturning itself is at its weakest, a potentially critical negative feedback to Atlantic buoyancy change during times of ice sheet collapse.

This study investigates the land-ocean interactions along the northern margin of the Gulf of Cadiz in the vicinity of the Guadiana River. Benthic foraminifera and sedimentological characteristics were analysed in a sedimentary sequence spanning ca. 5000 years (core 8, 22 m water depth) retrieved from the inner shelf prodeltaic wedge. The analyses were integrated in a temporal framework based on accelerated mass spectrometry radiocarbon dating. Paleoenvironmental changes and sediment transfer mechanisms from the continent to the shelf were investigated and related to climatic oscillations and anthropogenic impact in the region. The results allowed the identification of two main periods of deposition. The first period, from ca. 5150 cal. BP (core base) to 1500-1200 cal. BP, is characterised by a mix of fine and coarse sediments, relatively constant percentages of terrigenous and bioclasts, and benthic foraminifera species characteristic of coastal environments. These features indicate an environment strongly influenced by discharge from the Guadiana River. The second period, from ca. 1500-1200 cal. BP to ca. 200 cal. BP (core top), is characterised by silt-clay fraction dominated sediments, an increase in terrigenous sediment towards the top, and benthic foraminifera species characteristic of environments with low levels of energy. An increase in the level of human occupation associated with changes in climate led to widespread erosion and soil loss to the continental shelf during this period, with possible silting up of the Guadiana eastern distributary, allowing the transport of high amounts of sediment to the shelf by the western distributary that led to the enhancement of fine sedimentation and the formation of the prodeltaic wedge in the area of the studied core. info:eu-repo/semantics/publishedVersion

The surface water hydrography along the western Iberian margin, as part of the North Atlantic's eastern boundary upwelling system, consists of a complex, seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling. Not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions, such as during marine isotope stage (MIS) 2, and how North Atlantic meltwater events, especially Heinrich events, affected them. To help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern Iberian margin (MD95-2040, MD95-2041, MD99-2336, and MD99-2339). The records reveals that with the exception of the Heinrich events and Greenland Stadial (GS) 4 hydrographic conditions along the western Iberian margin were not much different from the present. During the Last Glacial Maximum (LGM), subtropical surface and subsurface waters penetrated poleward to at least 40.6°N (site MD95-2040). Export productivity was, in general, high on the western margin during the LGM and low in the central Gulf of Cadiz, in agreement with the modern situation. During the Heinrich events and GS 4, on the other hand, productivity was high in the Gulf of Cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling. Heinrich event 1 had the strongest impact on the hydrography and productivity off Iberia and was the only period when subarctic surface waters were recorded in the central Gulf of Cadiz. South of Lisbon (39°N), the impact of the other Heinrich events was diminished, and not all of them led to a significant cooling in the surface waters. Thus, climatic impacts of Heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region.

[1] This paper documents the migration of the Polar Front (PF) over the Iberian margin during some of the cold climatic extremes of the last 45 ka. It is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42°N. Planktonic δ18O (Globigerina bulloides), ice-rafted detritus concentrations, and the relative abundance of the polar foraminifera Neogloboquadrina pachyderma sinistral were used to track the PF position. These three data sets, compared from core to core, show a consistent evolution of the sea surface paleohydrology along the Iberian margin over the last 45 ka. We focused on five time slices representative of cold periods under distinct paleoenvironmental forcings: the 8.2 ka event and the Younger Dryas (two recent cold events occurring within high values of summer insolation), Heinrich events 1 and 4 (reflecting major episodes of massive iceberg discharges into the North Atlantic), and the Last Glacial Maximum (typifying the highest ice volume accumulated in the Northern Hemisphere). For each event, we generated schematic maps mirroring past sea surface hydrological conditions. The maps revealed that the Polar Front presence along the Iberian margin was restricted to Heinrich events. The sea surface conditions during the Last Glacial Maximum were close to those at present day, except for the northern sites which briefly experienced subarctic conditions.

Gerhard Friedrich Lutze was born in Braunschweig, Germany, on 12 April 1932 to Hildegard and Paul Gustav Friedrich Lutze who was an electronic engineer. Gerd attended the Wilhelm-Gymnasium and reformed Oberrealschule in Braunschweig. He moved up a year because he was an extremely gifted student, and graduated from a class of five students. Gerd studied at the Universities of Tubingen and Braunschweig. At the latter, Professor Paul Dorn proposed that Gerd pursue the doctoral thesis in which he established a foraminiferal and ostracodal biostratigraphy for Lower Saxony (NW Germany) that closely correlated with the existing ammonite zonation. While pursuing his doctorate, Gerd developed and maintained contact with biostratigraphers and micropaleontologists in oil companies and at the Bundesanstalt fur Bodenforschung, Hanover, among which were Franz Bettenstaedt, Helmut Bartenstein, and Heinrich Hiltermann, and his first wife Brunhilde Grabert. He also became acquainted with Inge and Eugen Seibold in Tubingen. In discussions about his doctoral research, Gerd often emphasized the importance of the applicability of micro-fossil biostratigraphy to commercial needs, as well as his affection for the scientific approach. Upon completion of his thesis in January 1958, Gerd was awarded the title doctor rerum naturarum , and then became a postdoctoral research assistant (“Wissenschaftlicher Assistent”) at the Geological Institute of the University of Braunschweig. From there he left for Los Angeles, having been awarded a fellowship of the German Research Foundation (DFG) to work at the …

A crude extract of demineralized bone matrix caused an altered differentiation of limb bud cells which was seen within 5 days in culture. Using this bioassay system we purified two factors to homogeneity and found that according to their N-terminal sequences they corresponded to TGF-beta 1 and TGF-beta 2 isolated from platelets. Biochemical analyses and biological studies (molecular mass determination, inactivation by reducing agents and proteases, antibody neutralization, competitive binding to TGF-beta receptors and influence on protein expression) provided additional evidence that the two proteins isolated from demineralized bone matrix were apparently identical to TGF-beta 1 and TGF-beta 2. Proteoglycan content, alkaline phosphatase activity and response of the cells to PTH stimulated adenylate cyclase were quantitatively changed by the factors. Culturing limb bud cells on polycarbonate membranes resulted in a rapid and extensive growth and differentiation of the cells to palpable tissue pieces. Relative to controls distinct cell and tissue morphology was observed macroscopically and in histological sections of these tissue pieces.

[1] Mg/Ca, Sr/Ca, and stable isotope measurements have been performed on tests from the planktonic foraminifers Globigerinoides ruber (white), Globigerina bulloides, and Neogloboquadrina pachyderma (right coiling) in samples from Ocean Drilling Program site 977A in the Alboran Sea (Western Mediterranean). The evolution of different water masses between 250 and 150 ka is described. Warm substages were characterized by strong seasonality and thermal stratification of the water column. By contrast, less pronounced seasonality and basin stratification seem to prevail during cold substages. Several periods of stratification due to the low salinity of the upper water mass occurred during the formation of organic-rich layers and also during a possible Heinrich-like event at 220 ka. The three foraminifer species studied show a common and large shell Sr/Ca variability in short timescales, suggesting changes in the global ocean Sr/Ca ratio as one of the main causes of variations in shell composition.

The living benthic foraminiferal assemblages in Kiel Fjord (SW Baltic Sea) were investigated in the years 2005 and 2006. The faunal studies were accomplished by geochemical analyses of surface sediments. In general, sediment pollution by copper, zinc, tin and lead is assessed as moderate in comparison with levels reported from other areas of the Baltic Sea. However, the inner Kiel Fjord is still exposed to a high load of metals and organic matter due to enhanced accumulation of fine-grained sediments in conjunction with potential pollution sources as shipyards, harbours and intensive traffic. The results of our survey show that the dominant environmental forcing of benthic foraminifera is nutrients availability coupled with human impact. A comparison with faunal data from the 1960s reveals apparent changes in species composition and population densities. The stress-tolerant species Ammonia beccarii invaded Kiel Fjord. Ammotium cassis had disappeared that reflects apparently the changes in salinity over the last 10 years. These changes in foraminiferal community and a significant increase of test abnormalities indicate an intensified environmental stress since the 1960s.

Early diagenetic features are noticed in the vicinity of carbonate platforms. Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show the strict relation between micro-scale euhydral crystallites of inorganic precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca ratios than expected for their pelagic environment in the time interval of ~100 000–550 000 calendar years before present. Laser ablation Mg/Ca (Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed 4–6 times elevated (2–3 times depleted) ratios, when ablating the diagenetic overgrowth. Crystalline overgrowth in proportions of 10–20% are estimated to cause the observed geochemical alteration. The extent of foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the composition of the bulk sediment, especially the content of high-magnesium calcite. Anomalous ratios of >6 mmol/mol only occur, when high-magnesium calcite has dissolved within the sediment. The older parts (back to ~800 kyrs) of the records are characterized by similar trends of Mg/Ca and Sr/Ca. We discuss possible scenarios to accommodate the obtained geochemical information.

A detailed, high-resolution stratigraphic analysis of the Mediterranean Outflow contourite system at the continental slope of the Gulf of Cadiz has been carried out through the correlation between a dense network of seismic reflection profiles (sparker, airgun, 3.75 kHz and parametric echosounder — TOPAS), Calypso giant piston and standard gravity cores. From such correlation we determine a stacking pattern constituted by four main seismic units (a–d) that are internally structured into ten subunits. Each subunit shows a single sequence formed by transparent seismic facies at the base to smooth, parallel reflectors of moderate to high amplitude facies at the top, being well correlated in the cores with a coarsening-upward sequence. The latest Pleistocene–Holocene deposits form glacial/interglacial depositional sequences related to cycles with a frequency range below the Milankovitch band that corresponds to millennial timescale climatic changes such as Dansgaard–Oeschger (1.5 ka) and Bond Cycles (10–15 ka). Oxygen isotope records of planktonic foraminifera and the occurrence of ice-rafted debris (IRD) in the most recent contourite subunits show clear evidence of the influence of the North Atlantic climatic conditions, especially the climatic Heinrich events (H) in the slope sedimentation of the Gulf of Cadiz and then in the circulation of the Mediterranean Outflow Water (MOW). The coarser contourite deposits are mostly associated with the Last Glacial Maximum, Younger Dryas and Heinrich events on the central area of the middle slope. During globally cooler conditions, the MOW was denser so that it was more active in deeper areas than today. On the other hand, during warm periods the MOW became less dense favoring an increased intensity of the MOW on the distal area of the upper slope. Therefore, spatial and vertical fluctuations of the MOW contourite system are strongly affected by global climate and oceanographic changes, being clearly influenced by iceberg discharges and probably also, by the resumption of thermohaline circulation in the North Atlantic Ocean during ice melting periods., Sí

GrpE is the nucleotide-exchange factor of the DnaK chaperone system. Escherichia coli cells with the classical temperature-sensitive grpE280 phenotype do not grow under heat-shock conditions and have been found to carry the G122D point mutation in GrpE. To date, the molecular mechanism of this defect has not been investigated in detail. Here, we examined the structural and functional properties of isolated GrpE(G122D) in vitro. Similar to wild-type GrpE, GrpE(G122D) is an elongated dimer in solution. Compared to wild-type GrpE, GrpE(G122D) catalyzed the ADP/ATP exchange in DnaK only marginally and did not compete with wild-type GrpE in interacting with DnaK. In the presence of ADP, GrpE(G122D) in contrast to wild-type GrpE, did not form a complex with DnaK detectable by size-exclusion chromatography with on-line static light-scattering and differential refractometry. Apparently, GrpE(G122D) in the presence of ADP binds to DnaK only with much lower affinity than wild-type GrpE. GrpE(G122D) could not substitute for wild-type GrpE in the refolding of denatured proteins by the DnaK/DnaJ/GrpE chaperone system. In the crystal structure of a (Delta1-33)GrpE(G122D).DnaK-ATPase complex, which as yet is the only available structure of a GrpE variant, Asp122 does not interact directly with neighboring residues of GrpE or DnaK. The far-UV circular dichroism spectra of mutant and wild-type GrpE proved slightly different. Possibly, a discrete change in conformation impairs the formation of the complex with DnaK and renders GrpE(G122D) virtually inactive as a nucleotide exchange factor. In view of the drastically reduced ADP/ATP-exchange activity of GrpE(G122D), the heat sensitivity of grpE280 cells might be explained by the ensuing slowing of the chaperone cycle and the increased sequestering of target proteins by high-affinity, ADP-liganded DnaK, both effects being incompatible with efficient chaperone action required for cell growth.

Integrin receptors are crucial players in cell adhesion and migration. Identification and characterization of cellular proteins that interact with their short alpha and beta cytoplasmic tails will help to elucidate the molecular mechanisms by which integrins mediate bi-directional signaling across the plasma membrane. Integrin alpha2beta1 is a major collagen receptor but to date, only few proteins have been shown to interact with the alpha2 cytoplasmic tail or with the alpha2beta1 complex. In order to identify novel binding partners of a alpha2beta1cytoplasmic domain complex, we have generated recombinant GST-fusion proteins, incorporating the leucine zipper heterodimerization cassettes of Jun and Fos. To ascertain proper functionality of the recombinant proteins, interaction with natural binding partners was tested. GST-alpha2 and GST-Jun alpha2 bound His-tagged calreticulin while GST-beta1 and GST-Fos beta1 proteins bound talin. In screening assays for novel binding partners, the immobilized GST-Jun alpha2/GST-Fos beta1 heterodimeric complex, but not the single subunits, interacted specifically with endothelial cell-derived vimentin. Vimentin, an abundant intermediate filament protein, has previously been shown to co-localize with alphavbeta3-positive focal contacts. Here, we provide evidence that this interaction also occurs with alpha2beta1-enriched focal adhesions and we further show that this association is lost after prolonged adhesion of endothelial cells to collagen.

The Tasmanian Gateway, focus of ODP Leg 189, is a key oceanographic area within the Southern Ocean. Our investigations concentrate on the last -500,000 years of sedimentation at Sites 1168 (western Tasmanian margin), 1170 and 1171 (Tasman Rise), and 1172 (East Tasman Plateau). A suite of geochemical proxy data reflecting paleo-export production, terrigenous flux, and sea surface temperature, constrain temporal and spatial variations in surface water masses and oceanographic frontal systems over these sites. Interglacial periods were commonly of low productivity and less affected by terrigenous matter supply, suggesting that the position of the Subtropical Convergence remained south of Tasman Rise. Only during early MIS 11 and MIS 9 over the southern Tasman Rise, and during MIS 7 over the northern Tasman Rise, did enhanced marine productivity, combined with an enhanced terrigenous flux, indicate waxing influence of subantarctic waters. During glacial MIS 2, marine productivity and terrigenous flux increased significantly at Sites 1168, 1170, and 1171 implying that the Subtropical Convergence moved northward to ∼42°S west of Tasmania. East of Tasmania, the presence of the East Australian Current caused the Subtropical Convergence to remain south of East Tasman Plateau. Glacial MIS 6 appears to have been different from MIS 2. The Subtropical Convergence stayed north of East Tasman Plateau, but clearly south of Site 1168 on the western Tasmanian margin. Strongly enhanced marine productivity and terrigenous flux during MIS 10 and 12 at Sites 1168, 1170, and 1172 suggest the dominant influence of subantarctic waters and the position of the Subtropical Convergence north of East Tasman Plateau. At South Tasman Rise, in contrast, the reduced terrigenous flux implies that Site 1171 moved outside the belt of westerly winds. Marine productivity ceased at that time mainly due to iron limitation.

20 pages, 8 figures, 1 table.-- Printed version published Mar 30, 2004., The response of coccolithophore assemblages to short-term millennial and centennial climatic changes over the last 50 kyr is studied in core M39029-7 from the Gulf of Cadiz (Atlantic Ocean) and core MD95-2043 from the Alboran Sea (Western Mediterranean Sea). The nannoplankton data are compared with oxygen isotopes, U37k′-SST and other biogeochemical and sedimentological proxies to obtain a new perspective of the paleoceanography and paleoecology of the area during these short-term climatic changes. Coccolithophores indicate that Heinrich events (HE) were characterised by the presence of cold, low salinity and turbid water masses on both sides of the Strait of Gibraltar. High abundances of the Lower Photic Zone (LPZ) species Florisphaera profunda in the Gulf of Cadiz synchronous with HE are interpreted as being an evidence of upper water-column stratification on the Atlantic side. These episodes coincided with input of terrigenous material, especially during H2. Surface waters during Dansgaard-Oeschger (DO) Stadials were also cold and turbid, while most of DO Interstadials were characterised by warm-water flora. The increase in small placoliths (small Gephyrocapsa and Emiliania huxleyi (4 μm), which is considered here as a cold-water indicator. The sharp decrease in large specimens of E. huxleyi related to the warming trend in the last deglaciation can be used as a biostratigraphic reference level that marks—at least approximately—the deglaciation and the beginning of the Holocene. Peaks of F. profunda are observed during Termination 1 (T1) in the Alboran Sea. They are isochronous with the “Organic-Rich Layer 1” recognised in the Western Mediterranean. In this interval, the water column of the region was stratified as a consequence of the global increase in the sea level following the deglaciation. Quantitative analyses of the coccolithophore assemblage allow us to interpret that coccolithophore production has been higher in the Alboran Sea than in the Gulf of Cadiz during the Holocene., This study was supported by an FPU grant from the Ministry of Education, Culture and Sport of Spain to E. Colmenero-Hidalgo and by Spanish project CLI 1998-1002-CO2-O2 and FEDER project 1FD97-1178. Sedimentological and stable-isotope work on core M39029-7 was funded by the Deutsche Forschungsgemeinschaft (Grants Scha355/15 and Za157/15).

Small heat shock proteins (sHsps) are ubiquitous molecular chaperones that bind denatured proteins in vitro, thereby facilitating their subsequent refolding by ATP-dependent chaperones. The mechanistic basis of this refolding process is poorly defined. We demonstrate that substrates complexed to sHsps from various sources are not released spontaneously. Dissociation and refolding of sHsp bound substrates relies on a disaggregation reaction mediated by the DnaK system, or, more efficiently, by ClpB/DnaK. While the DnaK system alone works for small, soluble sHsp/substrate complexes, ClpB/DnaK-mediated protein refolding is fastest for large, insoluble protein aggregates with incorporated sHsps. Such conditions reflect the situation in vivo, where sHsps are usually associated with insoluble proteins during heat stress. We therefore propose that sHsp function in cellular protein quality control is to promote rapid resolubilization of aggregated proteins, formed upon severe heat stress, by DnaK or ClpB/DnaK.

Deep marine currents are strongly influenced by climatic changes. They also deposit, rework, and sort sediment, and can generate kilometer-scale sedimentary bodies (drifts). These drifts are made of thoroughly bioturbated, stacked sedimentary sequences called contourites [Gonthier et al., 1984]. As a consequence, change in the direction or intensity of currents can be recorded in the sediments.

The vic two-component signal transduction system of Streptococcus pneumoniae is essential for growth. The vic operon comprises three genes encoding the following: VicR, a response regulator of the OmpR family; VicK, its cognate histidine kinase; and VicX, a putative protein sharing 55% identity to the predicted product (YycJ) of an open reading frame in the Bacillus subtilis genome. We show that not only is vic essential for viability but it also influences virulence and competence. A putative transcriptional start site for the vic operon was mapped 16 bp upstream of the ATG codon of vicR . Only one transcript of 2.9 kb, encoding all three genes, was detected by Northern blot analysis. VicK, an atypical PAS domain-containing histidine kinase, can be autophosphorylated in vitro, and VicR functions in vitro as a phospho-acceptor protein. (PAS is an acronym formed from the names of the proteins in which the domains were first recognized: the Drosophila period clock protein [PER], vertebrate aryl hydrocarbon receptor nuclear translocator [ARNT], and Drosophila single-minded protein [SIM].) PAS domains are commonly involved in sensing intracellular signals such as redox potential, which suggests that the signal for vic might also originate in the cytoplasm. Growth rate, competence, and virulence were monitored in strains with mutations in the vic operon. Overexpression of the histidine kinase, VicK, resulted in decreased virulence, whereas the transformability of a null mutant decreased by 3 orders of magnitude.

Trigger Factor (TF) is the first chaperone that interacts with nascent chains of cytosolic proteins in Escherichia coli. Although its chaperone activity requires association with ribosomes, TF is present in vivo in a 2-3 fold molar excess over ribosomes and a fraction of it is not ribosome-associated after cell lysis. Here we show that TF follows a three-state equilibrium. Size exclusion chromatography, crosslinking and analytical ultracentrifugation revealed that uncomplexed TF dimerizes with an apparent Kd of 18 microM. Dimerization is mediated by the N-terminal ribosome binding domain and the C-terminal domain of TF, whereas the central peptidyl prolyl isomerase (PPlase) and substrate binding domain does not contribute to dimerization. Crosslinking experiments showed that TF is monomeric in its ribosome-associated state. Quantitative analysis of TF binding to ribosomes revealed a dissociation constant for the TF-ribosome complex of approximately 1.2 microM. From these data we estimate that in vivo most of the ribosomes are in complex with monomeric TF. Uncomplexed TF, however, is in a monomer-dimer equilibrium with approximately two thirds of TF existing in a dimeric state.

Sea surface temperature (SST) profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a W-E latitudinal transect encompassing the Gulf of Cadiz (Atlantic Ocean), the Alboran Sea, and the southern Tyrrhenian Sea (western Mediterranean). The results document the sensitivity of the Mediterranean region to the short climatic changes of the North Atlantic Ocean, particularly those involving the latitudinal position of the polar front. The amplitude of the SST oscillations increases toward the Tyrrhenian Sea, indicating an amplification effect of the Atlantic signal by the climatic regime of the Mediterranean region. All studied cores show a shelter cooling phase (700 years) for the Younger Dryas (YD) than that observed in the North Atlantic region (1200 years). This time diachroneity is related to an intra-YD climatic change documented in the European continent. Minor oscillations in the southward displacement of the North Atlantic polar front may also have driven this early warming in the studied area. During the Holocene a regional diachroneity propagating west to east is observed for the SST maxima, 11.5-10.2 kyr B.P. in the Gulf of Cadiz, 10-9 kyr B.P. in the Alboran Sea, and 8.9-8.4 kyr B.P. in the Thyrrenian Sea. A general cooling trend from these SST maxima to present day is observed during this stage, which is marked by short cooling oscillations with a periodicity of 730+/-40 years and its harmonics.

DnaK, a Hsp70 acting in concert with its co-chaperones DnaJ and GrpE, is essential for Escherichia coli to survive environmental stress, including exposure to elevated temperatures. Here we explored the influence of temperature on the structure of the individual components and the functional properties of the chaperone system. GrpE undergoes extensive but fully reversible conformational changes in the physiologically relevant temperature range (transition midpoint at approximately 48 degrees C), as observed with both circular dichroism measurements and differential scanning calorimetry, whereas no thermal transitions occur in DnaK and DnaJ between 15 degrees C and 48 degrees C. The conformational changes in GrpE appear to be important in controlling the interconversion of T-state DnaK (ATP-liganded, low affinity for polypeptide substrates) and R-state DnaK (ADP-liganded, high affinity for polypeptide substrates). The rate of the T --R conversion of DnaK due to DnaJ-triggered ATP hydrolysis follows an Arrhenius temperature dependence. In contrast, the rate of the R --T conversion due to GrpE-catalyzed ADP/ATP exchange increases progressively less with increasing temperature and even decreases at temperatures above approximately 40 degrees C, indicating a temperature-dependent reversible inactivation of GrpE. At heat-shock temperatures, the reversible structural changes of GrpE thus shift DnaK toward its high-affinity R state.

The bacterial chaperone SecB assists translocation of proteins across the inner membrane. The mechanism by which it differentiates between secretory and cytosolic proteins is poorly understood. To identify its binding motif, we screened 2688 peptides covering sequences of 23 proteins for SecB binding. The motif is approximately 9 residues long and is enriched in aromatic and basic residues, whereas acidic residues are disfavored. Its identification allows the prediction of binding regions within protein sequences with up to 87% accuracy. SecB-binding regions occur statistically every 20-30 residues. The occurrence and affinity of binding regions are similar in SecB-dependent and -independent secretory proteins and in cytosolic proteins, and SecB lacks specificity toward signal sequences. SecB cannot thus differentiate between secretory and non-secretory proteins via its binding specificity. This conclusion is supported by the finding that SecB binds denatured luciferase, thereby allowing subsequent refolding by the DnaK system. SecB may rather be a general chaperone whose involvement in translocation is mediated by interactions of SecB and signal sequences of SecB-bound preproteins with the translocation apparatus.

The molecular chaperone DnaK, the Hsp70 homolog of Escherichia coli, binds hydrophobic polypeptide segments in extended conformation. The co-chaperone DnaJ (Hsp40) has been reported to bind native and denatured proteins as well as peptides. We tested pseudo-peptides of D-amino acids as ligands for both chaperones. In comparison to the parent all-L peptide, these mimetics had either enantiomorphic side chain positions combined with retained main chain direction (normal all-D peptide) or unchanged side chain topology together with reverse direction of the peptide backbone (retro all-D peptide). The peptides were labeled with acrylodan (a), and their binding to DnaK and DnaJ was monitored by the accompanying increase in fluorescence intensity. The parent all-L peptide a-CALLLSAARR bound to both DnaK (Kd = 0.1 microM) and DnaJ (Kd = 9.2 microM). In contrast, the normal all-D and retro all-D peptides did not bind to DnaK; they bound, however, to DnaJ with Kd values of 6.8 microM and 0.9 microM, respectively. The emission spectra of the DnaJ-bound peptides suggests that DnaJ bound both D-peptides with the same main chain direction as L-peptides. Binding of the normal all-D and all-L peptides inhibited the DnaJ-induced stimulation of DnaK ATPase. However, binding of the retro all-D analog to DnaJ did not impair the stimulation, indicating the existence of separate binding sites for peptides and DnaK.

The polypeptide binding and release cycle of the molecular chaperone DnaK (Hsp70) of Escherichia coli is regulated by the two co-chaperones DnaJ and GrpE. Here, we show that the DnaJ-triggered conversion of DnaK.ATP (T state) to DnaK.ADP.Pi (R state), as monitored by intrinsic protein fluorescence, is monophasic and occurs simultaneously with ATP hydrolysis. This is in contrast with the T--R conversion in the absence of DnaJ which is biphasic, the first phase occurring simultaneously with the hydrolysis of ATP (Theyssen, H., Schuster, H.-P., Packschies, L., Bukau, B., and Reinstein, J. (1996) J. Mol. Biol. 263, 657-670). Apparently, DnaJ not only stimulates ATP hydrolysis but also couples it with conformational changes of DnaK. In the absence of GrpE, DnaJ forms a tight ternary complex with peptide.DnaK.ADP.Pi (Kd = 0.14 microM). However, by monitoring complex formation between DnaK (1 microM) and a fluorophore-labeled peptide in the presence of ATP (1 mM), DnaJ (1 microM), and varying concentrations of the ADP/ATP exchange factor GrpE (0.1-3 microM), substoichiometric concentrations of GrpE were found to shift the equilibrium from the slowly binding and releasing, high-affinity R state of DnaK completely to the fast binding and releasing, low-affinity T state and thus to prevent the formation of a long lived ternary DnaJ. substrate.DnaK.ADP.Pi complex. Under in vivo conditions with an estimated chaperone ratio of DnaK:DnaJ:GrpE = 10:1:3, both DnaJ and GrpE appear to control the chaperone cycle by transient interactions with DnaK.

Publisher Summary The chapter presents a study related to molecular chaperones and their interactions through analytical ultracentrifugation and other methodologies. After a brief introduction into basic principles of the technique, the chapter presents practical examples to illustrate the ability of the methodology to resolve controversial questions in the chaperone field and discusses some results in the context of other methodologies used to determine quaternary structure. In an analytical ultracentrifugation experiment an analysis is made of the distribution of molecules according to their masses within a field of gravitation. This analysis can also be done using a preparative centrifuge, where the concentration gradient is measured after the run and drop fractionation of the contents of the tubes; however, in this case only final concentration profiles are obtained from a single centrifugation run and sedimentation must occur in the presence of preformed density gradients (for example, of glycerol or sucrose). The chapter discusses that determination of protein quaternary structure should never be based exclusively on relative methods. Only a few methodologies, such as analytical ultracentrifugation techniques, unambiguously deliver molecular masses of homo- or hetero-complexes in solution without the need for arbitrary assumptions. The chapter demonstrates the practicality of investigating the comparably large chaperonin heterocomplexes under equilibrium. The chapter concludes by stating that the investigation of chaperonin-substrate interactions will be a productive field for future analytical ultracentrifugation experiments.

The gene encoding the dihydropteroate synthase of staphylococcus aureus has been cloned, sequenced and expressed in Escherichia coli. The protein has been purified for biochemical characterization and X-ray crystallographic studies. The enzyme is a dimer in solution, has a steady state kinetic mechanism that suggests random binding of the two substrates and half-site reactivity. The crystal structure of apo-enzyme and a binary complex with the substrate analogue hydroxymethylpterin pyrophosphate were determined at 2.2 A and 2.4 A resolution, respectively. The enzyme belongs to the group of “ TIM-barrel” proteins and crystallizes as a non-crystallographic dimer. Only one molecule of the substrate analogue bound per dimer in the crystal. Sequencing of nine sulfonamide-resistant clinical isolates has shown that as many as 14 residues could be involved in resistance development. The residues are distributed over the surface of the protein, which defies a simple interpretation of their roles in resistance. Nevertheless, the three-dimensional structure of the substrate analogue binary complex could give important insight into the molecular mechanism of this enzyme.

The mitochondrial chaperone mhsp70 mediates protein transport across the inner membrane and protein folding in the matrix. These two reactions are effected by two different mhsp70 complexes. The ADP conformation of mhsp70 favors formation of a complex on the inner membrane; this 'import complex' contains mhsp70, its membrane anchor Tim44 and the nucleotide exchange factor mGrpE. The ATP conformation of mhsp70 favors formation of a complex in the matrix; this 'folding complex' contains mhsp70, the mitochondrial DnaJ homolog Mdj1 and mGrpE. A precursor protein entering the matrix interacts first with the import complex and then with the folding complex. A chaperone can thus function as part of two different complexes within the same organelle.

GroEL and DnaK with their cofactors constitute the major chaperone systems promoting protein folding in theEscherichia colicytosol. The ability of GroEL to bind and promote folding of a substrate released from DnaK led to the proposal that the DnaK and GroEL systems act successively along a protein folding pathway. Here we have investigated the role of both systems in preventing aggregation and assisting refolding of firefly luciferase denatured by guanidinium chloride and heat. We find that DnaK and GroEL compete with each other for binding to non-native luciferase. Addition of ATP and co-operating proteins results in release of luciferase from either chaperone in a non-native conformation. Only a small fraction of luciferase molecules released from GroEL can reach the native state. Instead, the released luciferase must bind repeatedly to the DnaK system, and only then is it able to fold to the native state. Thus, during a folding reaction, DnaK and GroEL do not obligatorily act in succession by promoting earlier and later protein folding steps, respectively. Rather, the two chaperone systems and perhaps others can form a lateral network of co-operating proteins. This chaperone network is proposed to be of particular importance for the assisted refolding of proteins that are unfolded by stress treatment such as heat shock and whose size is too large to allow folding inside the substrate binding cavity of the GroEL ring underneath GroES.

The E. coli heat shock response is regulated at the transcriptional level through stress-dependent controls of the heat shock promoter-specific sigma32 subunit of RNA polymerase. A key aspect of this regulation, the sensing of stress and transmission of this information to sigma32, involves the chaperone system formed by the DnaK, DnaJ and GrpE heat shock proteins. This system mediates stress- dependent controls of levels and activity of sigma32 which rely, at least in part, on direct association of DnaK and DnaJ with sigma32. We identified DnaK binding sites within the sigma32 sequence by probing a cellulose-bound peptide library scanning sigma32. Two sites with high affinity for DnaK, containing the motifs RKLFFNLR and LRNWRIVK, were located centrally and peripherally, respectively, to the region C of sigma32, previously implicated genetically in chaperone-dependent control of sigma32 levels. Cloning and sequencing of rpoH homologs from five Gram-negative proteobacteria revealed that region C, including the DnaK binding motif central to it, is highly conserved among sigma32 homologs but missing in the other sigma factors. We propose that binding of DnaK to region C is central to a conserved regulatory mechanism allowing the sensing of stress by the heat shock gene transcription machinery.

An undisturbed 16 m late Pliocene-Pleistocene sediment core spanning 2.6 Myr of deposition was recovered from the Manihiki Plateau by the German research vessel Sonne in 1990. This core 34KL complements the heavily disturbed late Pliocene-Pleistocene core sections of DSDP Site 317, and is well suited for stratigraphic correlation. The sediments consist of calcareous microfossils (93–97% CaCO3), minor portions of siliceous microfossils and detrital minerals. All important calcareous microfossil zones could be identified and correlated with the magnetostratigraphic and isotope stratigraphic events, stages and periods. Due to the high degree of silica dissolution, the late Quaternary radiolarian Buccinosphaera invaginata Zone is the only siliceous fossil zone which could be identified. An interval with Globigerinoides gomitulus/pink was found within the middle Pleistocene which is clearly distinguished from the Globigerinoides ruber/pink interval of the late Pleistocene. The magnetostratigraphic Gauss-Matuyama and Matuyama-Brunhes boundaries as well as the Olduvai and Jaramillo events were clearly identified. The δ180 curve displays the 100 kyr (Milankovitch) and the 41 kyr (Laplace) cyclicity periods. The beginning of the Laplace Period and the last occurrence of the calcareous nannofossil Discoaster brouweri, which marks the end of the Pliocene, fall within the base of the Olduvai Event. There is also a marked drop in sedimentation rates around this time, which seems to be a regional phenomenon. Prominent 3.5 kHz subbottom reflectors at 8 ms and 15 ms reflection time are related to lithologic changes near the Mid-Pleistocene Revolution (MPR) and the beginning of the Laplace Period or the Pleistocene, respectively. It is possible to trace these reflectors laterally to the eroded eastern edge of the Manihiki Plateau where they can be tied to older strata.

Sediments of 13 piston cores from opposite continental slopes of the South China Sea, off southern China and Sabah (northern Borneo), were analyzed by sedimentological methods and dated by oxygen isotope stratigraphy. Sediments mostly consist of hemipelagic clay with 20% carbonate off Sabah and 40% off China. We calculated terrigenous and carbonate accumulation rates for up to 11 time-slices from the Holocene to oxygen-isotope stage 6. Terrigenous accumulation rates generally increase with water depth and reach a maximum at the middle slope off Sabah and at the lower continental slope off China. During glacial and interglacial times this distribution pattern did not markedly change, despite an increase of accumulation rates for glacial periods by a factor of 2 to 5 compared to interglacial periods. Rates are negatively correlated with positions of sea level, which controls the partition of fluviatile terrigenous material for deposition on shelf, slope, and abyssal plain. Carbonate accumulation rates are higher off China by a factor of 2 compared to Sabah, probably indicating higher calcareous plankton productivity.

Based on a morphological taxonomic revision of available species, and supported by a separate molecular phylogenetic study, we identified Onthophagus (Palaeonthophagus) medius (Kugelann, 1792) as a good western palaearctic species and a sibling species of O. vacca (Linnaeus, 1767). In this paper we diagnose and illustrate the key morphological features and distribution of both species. A neotype is designated for Copris medius Kugelann, 1792.

If the concept of recycling is further pursued, serious consideration must be given to waste wood as a resource material particularly since waste wood contains a of of metals which are claimable and can be easily sold. The equipment already exists to process both waste wood and bark but two further requirements must be met if this is to develop profitably: Firstly disposal companies must make both materials available for recycling in a usable condition. Wood and bark must be separated from other waste at the time of collection which would happen automatically if the concept of recycling were more generally adopted. Secondly, prospective customers must be prepared to buy the processes material and, if necessary, adapt their machinery to handle it. Both of these requirements are already being met in some measure and we can be optimistic about the future of recycling of wood waste and bark. Processing of waste wood into charcoal is a new and increasingly important application. Bark, so far a non-usuable waste product of forestry is increasingly recognised as high-quality raw material. Bark can be processed in the same machines as waste wood to obtain highquality compost and biologically good cover material (mulch) for agriculture and horticulture. Cost accounting for the processor is very positive.

Durch potentionstatische und potentiokinetische Polarisationsmessungen an verschiedenen 18 Cr-10 Ni-Stahlen mit Molybdangehalten bis zu 4,3% in 25 und 45 proz. Ammoniumrhodanidlosungen wurde festgestellt, das die Ursache der Lochkorrosion im Potentialbereich von –300 bis +250 m V H auf einer unvollstandigen Passivierung beruht. Die Ausbildung stabiler Passivschichten wird hier durch die Bildung und lokale oxidative Wiederauflosung sulfidischer Deckschichten gestort. Oberhalb +250 m V H wirken Rhodanidionen in den schwachsauren Ammoniumrhodanidlosungen ahnlich wie Chloridionen als passivitatszerstorendes Agens. Die Durch potentionstatische Halteversuche ermittelten Grenzpotentiale der stabilen Lochkorrosion werden mit zunehmendem Molybdangehalt von –300 bis nach –150 m V H verschoben. Die geringste Lochkorrosionsneigung zeigte der Stahl mit dem hochsten Molybdangehalt. Pitting corrosion of austenitic CrNiMo-steels in concentrated ammoniumrhodanide solutions Quasipotentiostatic and potentiokinetic polarisation measurements at various 18 Cr-10 Ni steels with molybdenum contents up to 4,3% were performed in 25 and 45% ammoniumrhodanide solutions. It was found that pitting corrosion is caused by incomplete passivation in the potential range of –300 to +250 m V H. At these potentials the formation of stable passive layers is hindered by the formation and local oxidative dissolution of sulfidic layers. Above +250 m V H rhodanide ions act in these weak acidic ammoniumrhodanide solutions as agents which destroy passive layers, comparable with chloride ions. The limiting potentials for stable pitting corrosion, obtained from potentiostatic experiments, are shifted from –300 to –150 m V H with increasing molybdenum content of the steel. The least tendency of pitting corrosion was found for that steel with the highest molybdenum content.

The reversible crosslinked protein complex L13–L21 was isolated from Escherichia coli ribosomes in milligram amounts. Tight couples (70 S) were crosslinked with the bifunctional reagent diepoxybutane. The reacted ribosomes were separated into their subunits by sucrose gradient centrifugation in the presence of 1 m m magnesium. The crosslinked subunits were analyzed by symmetrical two-dimensional gel electrophoresis. One crosslinked protein complex detected within the large subunit was purified by salt extraction, acidic acid extraction, and ion-exchange chromatography. Two-dimensional gel electrophoresis and immunological results established L13 and L21 as the components of this crosslink.