The simplest views of long-range electron transfer utilize flat one-dimensional barrier tunneling models, neglecting structural details of the protein medium. The pathway model of protein electron ...transfer reintroduces structure by distinguishing between covalent bonds, hydrogen bonds, and van der Waals contacts. These three kinds of interactions in a tunneling pathway each have distinctive decay factors associated with them. The distribution and arrangement of these bonded and nonbonded contacts in a folded protein varies tremendously between structures, adding a richness to the tunneling problem that is absent in simpler views. We review the pathway model and the predictions that it makes for protein electron transfer rates in small proteins, docked proteins, and the photosynthetic reactions center. We also review the formulation of the protein electron transfer problem as an effective two-level system. New multi-pathway approaches and improved electronic Hamiltonians are described briefly as well.
The immune system has been implicated in the pathophysiology of endometriosis. To determine if modulation of the immune system influences endometriotic implant growth and protein production, the ...following experiment was conducted.
Female rats with surgically induced endometriosis were treated with either the immunosuppressive agent pentoxifylline (Pent; 5 mg/kg BW; N = 16) or a vehicle (N = 16) for 7 consecutive days, then killed. Twenty-four hours before death, 8 animals from each group were injected intraperitoneally with the immunostimulatory agent lipopolysaccharide (LPS; 200 micrograms/kg BW). At death, endometriotic implants were measured and protein production assessed by two-dimensional polyacrylamide gel electrophoresis.
Pentoxifylline significantly (P < 0.001) reduced endometriotic implant size (2.15 +/- 0.65 mm2 vs. 17.13 +/- 1.98 mm2) whereas LPS was without effect (18.32 +/- 2.57 mm2 vs. 17.13 +/- 1.98 mm2). Pentoxifylline also suppressed production of a portion of the proteins that comprise the implant specific group of proteins, ENDO-2, whereas LPS induced the production of two additional ENDO-2 proteins.
Immunomodulatory agents can modulate rat endometriotic implant growth and production of implant-specific proteins.
Planktonic foraminiferal δ18O time series from three well‐dated, high sedimentation rate cores near the Florida Keys (24.4°N, 83.3°W) exhibit repeated centennial to millennial‐scale oscillations ...during the late Holocene. Isotopic shifts of 0.2–0.3‰ over the past 5200 years represent changes in sea‐surface temperature (SST) of 1.0–1.5°C or salinity variability of 1–2 psu. The largest significant isotopic events are centered at approximately 200, 2000, 3200, and prior to 4000 calendar years BP. High Florida Current δ18O during the Little Ice Age (LIA) correlates with published records of high δ18O in the Sargasso Sea and low SST off the coast of west Africa. An interval of generally low δ18O in the Florida Straits from 1800 to 500 years BP is synchronous with the Medieval Warm Period off west Africa but leads low δ18O in the Sargasso Sea by several hundred years. Synchronous cooling across the subtropical gyre during the LIA is difficult to explain using interannual North Atlantic Oscillation patterns but may be consistent with the simulated effects of reduced solar irradiance. At frequencies between 1/1000 and 1/300 years during the Late Holocene, Florida Current δ18O is coherent with a published estimate of 14C production rate. Radiocarbon production seems to lead δ18O at these frequencies, but uncertainty in the phase calculation precludes a clear lead‐lag relationship. At frequencies lower than 1/300 years, Florida Current δ18O is coherent and in phase with atmospheric Δ14C. The coherence of Δ14C and δ18O at periods >1000 years implies oceanic circulation may play a role in modulating atmospheric radiocarbon on millennial timescales.
Benthic foraminiferal δ13C and Cd/Ca studies suggest that deep Atlantic circulation during the Last Glacial Maximum was very different from today, with high‐nutrient (low δ13C, high Cd) deep Southern ...Ocean Water (SOW) penetrating far into the North Atlantic. However, if some glacial δ13C values are biased by productivity artifacts and/or air‐sea exchange processes, then the existing δ13C data may be consistent with the continual dominance of North Atlantic Deep Water (NADW). Cibicidoides wuellerstorfi Cd/Ca results presented here indicate that the glacial North Atlantic was strongly enriched in dissolved Cd below ∼2500 m depth. If NADW formation was still vigorous relative to SOW formation, these data could be explained by either increased preformed nutrient levels in the high‐latitude North Atlantic or by increased organic matter remineralization within lower NADW. High glacial Zn/Ca values in the same samples, however, are best explained by a substantially increased mixing with Zn‐rich SOW. The cause was most likely a partial replacement of NADW by less dense Glacial North Atlantic Intermediate Water. This reorganization also lowered deep North Atlantic CO32− concentrations by perhaps 10 to 15 μmol kg−1.
Stable isotopic measurements of G. sacculifer and C. wuellerstorfi in a core from the western equatorial Atlantic imply that there are parallel, suborbital oscillations in surface water hydrography ...and deep water circulation occurring during oxygen isotope stages 2 and 3. Low values of G. sacculifer δ18O accompany high values of C. wuellerstorfi δ13C, linking warmer sea surface temperatures (SSTs) in the tropics with increased production of lower North Atlantic Deep Water (NADW). The amplitude of the δ18O oscillations is 0.6‰ (or 2°–3°C), which is superimposed on a glacial/interglacial amplitude of about 2.1‰. Using the G. sacculifer δ18O data, we calculate that surface waters were colder during stage 2 than calculated by CLIMAP 1976, 1981. The longer‐period (>2 kyr) oscillations in air temperature recorded in the Greenland and Antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial Atlantic. The magnitude of these oscillations in tropical SST is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone. The apparent synchroneity of equatorial SST and polar air temperature changes, as well as the amplitude of the SST changes at the equator, are consistent with the climate effects expected from changes in the atmosphere's greenhouse gas content (H2Ovapor, CO2, and CH4).
The climatology of the North Atlantic LOZIER, M. S; BRECHNER OWENS, W; CURRY, R. G
Progress in oceanography,
1995, 1995-1-00, 19950101, Letnik:
36, Številka:
1
Journal Article
Recenzirano
Data from approximately 144,000 hydrographic stations in the North Atlantic have been retrieved from the national Oceanic Data Centre and analysed to produce maps of mean pressure, temperature, ...salinity and oxygen on selected potential density surfaces for the domain bounded by 0 degree -85 degree W and 0 degree -65 degree N. The data span the period from 1904 to 1990 with the majority of the data from the last four decades. The data set for this region is 60% larger than that used in the production of Levitus' Climatological World Atlas. This increase in stations, coupled with smoothing scales specific to the North Atlantic rather than the global ocean, considerably improves the resolution of the basin's features. The mean property fields and their associated standard deviations are resolved on a one-degree grid with little smoothing, contrasting with the Levitus Atlas where properties, although presented on a one-degree grid, have been smoothed on the order of 1000km. Another important feature of this database is the process by which irregularly spaced data are averaged onto a regular grid. In a significant departure from the Levitus analysis, which averaged on depth surfaces, these data were averaged on potential density surfaces, thus eliminating an artificial mixing of water mass properties. The database is used to describe the baroclinicity of well-known features such as the Gulf Stream, the North Atlantic Current and the Deep Western Boundary Current, and to elucidate the recirculations associated with these currents. It additionally resolves several new features in the intermediate and deep North Atlantic. These features include the signature of a large scale deep recirculation that extends southwestward from the eastward extension of the North Atlantic Current to the separation point of the Gulf Stream near Cape Hatteras. This recirculation, which spans approximately 2000m of the water column, encompasses more local recirculations and potentially mixes subpolar and subtropical waters. Furthermore, in the upper thermocline, this database reveals a coherent Azores Current that stretches from the Gulf Stream system south of the Tail of the Grand Banks to Madeira. This flow is marked by divergences to the south and convergences from the north such that its downstream transport is not much changed.
To test the hypothesis that endometriotic tissue secretes endometriotic-specific proteins into the peritoneal fluid (PF) of women with endometriosis.
A prospective design was utilized in this study.
...Tertiary care, university-based center and reproductive endocrinology laboratory.
Women of reproductive age who were infertile with endometriosis (n = 19), as well as without endometriosis (n = 7), and fertile women undergoing tubal ligation (n = 6).
Collection of PF fluid via laparoscopy.
Peritoneal fluid proteins were isolated and assessed by two-dimensional polyacrylamide gel electrophoresis.
Two-dimensional electrophoresis of PF proteins isolated a group of proteins (M(r) = 32 to 40 kd, pI = 4.5 to 5.2) in all PF samples that was similar to the rat endometriotic implant-specific protein, Endo-1. This group of proteins consisted of 5 to 12 individual proteins with endometriosis PF containing a significantly higher number of proteins (median = 11) compared with either PF from infertile women without endometriosis (median = 8) or from women undergoing tubal ligation (median = 7). In addition, one protein (M(r) = 32 kd, pI = 5.8), termed EPF-32, was detected predominantly (18 of 19 samples analyzed) in PF from women with endometriosis. This protein was also detected in PF from infertile women without endometriosis (2 of 7 samples) but not in the PF of fertile women undergoing tubal ligation (0 of 6 samples). The appearance of this protein was not associated with the severity of endometriosis.
It is concluded from this study that PF from women with endometriosis predominantly contains a 32-kd protein (EPF-32) compared with the PF of women without the disease. The role of EPF-32 in the pathophysiology of endometriosis is not established but this protein may function as a diagnostic marker for endometriosis.
Benthic foraminiferal Cd/Ca from an intermediate depth, western South Atlantic core documents the history of southward penetration of North Atlantic Intermediate Water (NAIW). Cd seawater estimates ...(CdW) for the last glacial are consistent with the production of NAIW and its export into the South Atlantic. At ∼14.5 ka concurrently with the onset of the Bølling‐Allerød to Younger Dryas cooling, the NAIW contribution to the South Atlantic began to decrease, marking the transition from a glacial circulation pattern to a Younger Dryas circulation. High CdW in both the deep North Atlantic and the intermediate South Atlantic imply reduced export of deep and intermediate water during the Younger Dryas and a significant decrease in northward oceanic heat transport. A modern circulation was achieved at ∼9 ka, concurrently with the establishment of Holocene warmth in the North Atlantic region, further supporting a close linkage between deepwater variability and North Atlantic climate.
We have measured Zn/Ca ratios in two taxa of Holocene‐aged benthic foraminifera from throughout the world's oceans. Zn/Ca is controlled by bottom water dissolved Zn concentration and, like Cd/Ca and ...Ba/Ca, by bottom water saturation state with respect to calcite. Measurements on “live‐collected” foraminifera suggest that the saturation effect occurs during growth and is not a postdepositional artifact. Zn/Ca could be a sensitive paleoceanographic tracer because deep water masses have characteristic Zn concentrations that increase about tenfold from the deep North Atlantic to the deep North Pacific. In addition, since Zn/Ca responds to a different range of saturation states than Cd/Ca, the two may be used together to evaluate changes in deep water carbonate ion (CO32−) concentration.
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