Natural ocean iron fertilization and climate variability over geological periods.

Marine primary producers are largely dependent on and shape the Earth's climate, although their relationship with climate varies over space and time. The growth of phytoplankton and associated marine primary productivity in most of the modern global ocean is limited by the supply of nutrients, including the micronutrient iron. The addition of iron via episodic and frequent events drives the biological carbon pump and promotes the sequestration of atmospheric carbon dioxide (CO2 ) into the ocean. However, the dependence between iron and marine primary producers adaptively changes over different geological periods due to the variation in global climate and environment. In this review, we examined the role and importance of iron in modulating marine primary production during some specific geological periods, that is, the Great Oxidation Event (GOE) during the Huronian glaciation, the Snowball Earth Event during the Cryogenian, the glacial-interglacial cycles during the Pleistocene, and the period from the last glacial maximum to the late Holocene. Only the change trend of iron bioavailability and climate in the glacial-interglacial cycles is consistent with the Iron Hypothesis. During the GOE and the Snowball Earth periods, although the bioavailability of iron in the ocean and the climate changed dramatically, the changing trend of many factors contradicted the Iron Hypothesis. By detangling the relationship among marine primary productivity, iron availability and oceanic environments in different geological periods, this review can offer some new insights for evaluating the impact of ocean iron fertilization on removing CO2 from the atmosphere and regulating the climate.

Research and Scholarship During the COVID-19 Pandemic: A Wicked Problem.

This study focuses on the impacts of the COVID-19 pandemic on research and scholarship at a research university in the United States. Building on studies in higher education policy, we conceptualized the COVID-19 pandemic as a 'wicked problem' that is complex, nonlinear, unique, and requiring urgent solutions. Wicked problems highlight pre-existing struggles, and therefore, recent challenges in higher education inform the methods and the findings of this study. Qualitative and quantitative survey data from 408 faculty, staff, and students explicate the reasons for reduced research output and adaptations made for increased or sustained productivity, health, and wellness that influenced research activities. The analysis showed that most respondents experienced reduced productivity mostly due to increased work responsibilities, limited access to research fields, and inadequate resources. Despite self-reported reduced productivity, participants from the University we studied experienced increases in funding during the pandemic. Thus, the findings also reported on the adaptations for sustained or increased productivity. These included new research pursuits, participation in conference and learning opportunities across geographic regions, and purchase of computer equipment/accessories for home offices. A small percentage of respondents mentioned improved health and well-being; however, many linked reduced research activities to health and well-being issues such as anxiety and fear about the pandemic and being overwhelmed due to work and home-life expectations. Knowledge of the challenges and opportunities presented within the first year of the pandemic can provide a basis for solutions to wicked problems higher education may face in the future.

Outwelling of total alkalinity and dissolved inorganic carbon from the Hooghly River to the adjacent coastal Bay of Bengal.

The seasonal variability of the lateral flux of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) of the tropical Hooghly estuary is analyzed in this work. In situ observations of water temperature, salinity, dissolved oxygen, TAlk, and pH were measured in four different stations of the Hooghly estuary. It was measured once every month during 2015-2016, and subsequently, DIC was estimated. A carbon budget was constructed to quantify carbon flows through the freshwater-marine continuum of the Hooghly estuary, and plausible impacts on the adjacent coastal ocean, the northern Bay of Bengal, were examined. The biogeochemical mass balance box model was used to compute the seasonal flow of carbon flux, and subsequently, the annual budgeting of lateral fluxes of TAlk and DIC to the adjacent coastal ocean was carried out. The net annual TAlk and DIC flux from the Hooghly estuary to the adjacent coastal ocean were 4.45 ± 1.90 × 1011 mol and 4.59 ± 1.70 × 1011 mol, respectively. The net annual DIC flux of the Hooghly estuary is about 30 to 60 times higher than surface area integrated air-water CO2 flux, which is an indication of promoting acidification in the adjacent coastal ocean. The present study indicates that the lateral DIC flux has increased substantially in the Hooghly estuary during the last two decades. The increase in inorganic carbon load in the Hooghly estuary due to the enhanced discharge of inorganic and organic matter load in the upper reaches of the estuary led to this increase in lateral DIC flux. The results strongly establish the need of having such regional studies for better understanding the estuarine carbon dynamics, and its role in controlling the adjacent coastal ocean dynamics.

Differential Impact of Extended Criteria Donors After Brain Death or Circulatory Death in Adult Liver Transplantation.

Using grafts from extended criteria donors (ECDs) and donation after circulatory death (DCD) donors is a strategy to address organ shortage in liver transplantation (LT). We studied the characteristics and outcomes of ECD and DCD grafts. We retrospectively studied consecutive adults who underwent deceased donor LT between 2006 and 2019. ECD was defined using modified Eurotransplant criteria. Our primary outcomes were graft and patient survival. A total of 798 grafts were used for LT, of which 93.1% were donation after brain death (DBD; 59.9% were also ECD) and 6.9% were DCD grafts (49.1% were also ECD). Among DBD graft recipients, donors having >33% liver steatosis or 3 ECD criteria resulted in poorer graft survival. Otherwise ECD graft recipients had similar graft and patient survival compared with non-ECD graft recipients. DCD graft recipients also had similar patient survival compared with DBD recipients. However, DCD grafts from an ECD appeared to have worse outcomes. DCD graft recipients experienced higher rates of early allograft dysfunction (50.9% versus 24.7%; P < 0.001) and ischemic biliopathy (16.4% versus 1.5%; P < 0.001) compared with DBD graft recipients. Use of DBD grafts from ECDs did not impact outcomes unless there was significant donor steatosis or 3 Eurotransplant criteria were met. DCD graft recipients have similar patient survival compared with DBD graft recipients as long as the donor was not an ECD. We recommend that DBD donors with 3 or more ECD features or >33% steatosis and DCD donors with any ECD features be used with caution in adult LT.

Epidemiology and outcomes of primary sclerosing cholangitis with and without inflammatory bowel disease in an Australian cohort.

BACKGROUND & AIMS: Epidemiological data on primary sclerosing cholangitis (PSC) outside the Northern hemisphere are limited. Similarly, the impact of inflammatory bowel disease (IBD) on PSC outcomes remains unclear. We aimed to study the epidemiology and outcomes of PSC patients with and without IBD in an Australian cohort. METHODS: We retrospectively studied PSC patients attending two tertiary referral hospitals over 20 years. Diagnosis of PSC was made according to international guidelines by positive cholangiography and/or liver biopsy (for small duct PSC) with supporting clinical and laboratory evidence. RESULTS: Of 208 PSC patients (61% male) were studied (2271patient-years follow-up). The median age of PSC diagnosis was similar for PSC-IBD and PSC-only patients (40 years vs 42 years, P = .35). All 33 deaths occurred in PSC-IBD patients while there were no deaths in PSC-only patients (21% vs 0%, P < .01). However, there were no significant differences in liver transplantation (PSC-only 25% vs PSC-IBD 31%, P = .45) and transplant-free survival between PSC-only and PSC-IBD patients (P = .43). On multivariate Cox regression, only elevated international normalized ratio (INR) was associated with a greater risk of death or liver transplant (HR 2.0, 95% CI 1.1-3.6, P = .02). Development of gastrointestinal malignancy was higher in the PSC-IBD group compared to PSC-only group (22% vs 2%, P < .01). CONCLUSION: Australian PSC patients have similar characteristics compared to European and North American cohorts. IBD is a significant predictor of gastrointestinal malignancies. Deaths were more common in PSC-IBD but overall transplant-free survival remained similar in PSC-IBD and PSC-only groups. An elevated INR was an independent predictor of death or liver transplantation.

Harmful algal blooms and climate change: Learning from the past and present to forecast the future.

Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. These pressures will be manifest as alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal blooms frustrates most hope of forecasting their future prevalence. Summarized here is the consensus of a recent workshop held to address what currently is known and not known about the environmental conditions that favor initiation and maintenance of harmful algal blooms. There is expectation that harmful algal bloom (HAB) geographical domains should expand in some cases, as will seasonal windows of opportunity for harmful algal blooms at higher latitudes. Nonetheless there is only basic information to speculate upon which regions or habitats HAB species may be the most resilient or susceptible. Moreover, current research strategies are not well suited to inform these fundamental linkages. There is a critical absence of tenable hypotheses for how climate pressures mechanistically affect HAB species, and the lack of uniform experimental protocols limits the quantitative cross-investigation comparisons essential to advancement. A HAB "best practices" manual would help foster more uniform research strategies and protocols, and selection of a small target list of model HAB species or isolates for study would greatly promote the accumulation of knowledge. Despite the need to focus on keystone species, more studies need to address strain variability within species, their responses under multifactorial conditions, and the retrospective analyses of long-term plankton and cyst core data; research topics that are departures from the norm. Examples of some fundamental unknowns include how larger and more frequent extreme weather events may break down natural biogeographic barriers, how stratification may enhance or diminish HAB events, how trace nutrients (metals, vitamins) influence cell toxicity, and how grazing pressures may leverage, or mitigate HAB development. There is an absence of high quality time-series data in most regions currently experiencing HAB outbreaks, and little if any data from regions expected to develop HAB events in the future. A subset of observer sites is recommended to help develop stronger linkages among global, national, and regional climate change and HAB observation programs, providing fundamental datasets for investigating global changes in the prevalence of harmful algal blooms. Forecasting changes in HAB patterns over the next few decades will depend critically upon considering harmful algal blooms within the competitive context of plankton communities, and linking these insights to ecosystem, oceanographic and climate models. From a broader perspective, the nexus of HAB science and the social sciences of harmful algal blooms is inadequate and prevents quantitative assessment of impacts of future HAB changes on human well-being. These and other fundamental changes in HAB research will be necessary if HAB science is to obtain compelling evidence that climate change has caused alterations in HAB distributions, prevalence or character, and to develop the theoretical, experimental, and empirical evidence explaining the mechanisms underpinning these ecological shifts.

A profile of an endosymbiont-enriched fraction of the coral Stylophora pistillata reveals proteins relevant to microbial-host interactions.

This study examines the response of Symbiodinium sp. endosymbionts from the coral Stylophora pistillata to moderate levels of thermal "bleaching" stress, with and without trace metal limitation. Using quantitative high throughput proteomics, we identified 8098 MS/MS events relating to individual peptides from the endosymbiont-enriched fraction, including 109 peptides meeting stringent criteria for quantification, of which only 26 showed significant change in our experimental treatments; 12 of 26 increased expression in response to thermal stress with little difference affected by iron limitation. Surprisingly, there were no significant increases in antioxidant or heat stress proteins; those induced to higher expression were generally involved in protein biosynthesis. An outstanding exception was a massive 114-fold increase of a viral replication protein indicating that thermal stress may substantially increase viral load and thereby contribute to the etiology of coral bleaching and disease. In the absence of a sequenced genome for Symbiodinium or other photosymbiotic dinoflagellate, this proteome reveals a plethora of proteins potentially involved in microbial-host interactions. This includes photosystem proteins, DNA repair enzymes, antioxidant enzymes, metabolic redox enzymes, heat shock proteins, globin hemoproteins, proteins of nitrogen metabolism, and a wide range of viral proteins associated with these endosymbiont-enriched samples. Also present were 21 unusual peptide/protein toxins thought to originate from either microbial consorts or from contamination by coral nematocysts. Of particular interest are the proteins of apoptosis, vesicular transport, and endo/exocytosis, which are discussed in context of the cellular processes of coral bleaching. Notably, the protein complement provides evidence that, rather than being expelled by the host, stressed endosymbionts may mediate their own departure.

In situ strain-level detection and identification of Vibrio parahaemolyticus using surface-enhanced Raman spectroscopy.

The outer membrane of a bacterium is composed of chemical and biological components that carry specific molecular information related to strains, growth stages, expressions to stimulation, and maybe even geographic differences. In this work, we demonstrate that the biochemical information embedded in the outer membrane can be used for rapid detection and identification of pathogenic bacteria using surface-enhanced Raman spectroscopy (SERS). We used seven different strains of the marine pathogen Vibrio parahaemolyticus as a model system. The strains represent four genetically distinct clades isolated from clinical and environmental sources in Washington, U.S.A. The unique quasi-3D (Q3D) plasmonic nanostructure arrays, optimized using finite-difference time-domain (FDTD) calculations, were used as SERS-active substrates for sensitive and reproducible detection of these bacteria. SERS barcodes were generated on the basis of SERS spectra and were used to successfully detect individual strains in both blind samples and mixtures. The sensing and detection methods developed in this work could have broad applications in the areas of environmental monitoring, biomedical diagnostics, and homeland security.

Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas.

Oceanic high-nitrate, low-chlorophyll environments have been highlighted for potential large-scale iron fertilizations to help mitigate global climate change. Controversy surrounds these initiatives, both in the degree of carbon removal and magnitude of ecosystem impacts. Previous open ocean enrichment experiments have shown that iron additions stimulate growth of the toxigenic diatom genus Pseudonitzschia. Most Pseudonitzschia species in coastal waters produce the neurotoxin domoic acid (DA), with their blooms causing detrimental marine ecosystem impacts, but oceanic Pseudonitzschia species are considered nontoxic. Here we demonstrate that the sparse oceanic Pseudonitzschia community at the high-nitrate, low-chlorophyll Ocean Station PAPA (50 degrees N, 145 degrees W) produces approximately 200 pg DA L(-1) in response to iron addition, that DA alters phytoplankton community structure to benefit Pseudonitzschia, and that oceanic cell isolates are toxic. Given the negative effects of DA in coastal food webs, these findings raise serious concern over the net benefit and sustainability of large-scale iron fertilizations.

MELD-GRAIL and MELD-GRAIL-Na Are Not Superior to MELD or MELD-Na in Predicting Liver Transplant Waiting List Mortality at a Single-center Level.

Background: Controversy exists regarding the best predictive model of liver transplant waiting list (WL) mortality. Models for end-stage liver disease-glomerular filtration rate assessment in liver disease (MELD-GRAIL) and MELD-GRAIL-Na were recently described to provide better prognostication, particularly in females. We evaluated the performance of these scores compared to MELD and MELD-Na. Methods: Consecutive patients with cirrhosis waitlisted for liver transplant from 1998 to 2017 were examined in this single-center study. The primary outcome was 90-d WL mortality. MELD, MELD-Na, MELD-GRAIL, and MELD-GRAIL-Na at the time of WL registration were compared. Model discrimination was assessed with area under the receiver operating characteristic curves and Harrell's C-index after fitting Cox models. Model calibration was examined with Grønnesby and Borgan's modification of the Hosmer-Lemeshow formula and by comparing predicted/observed outcomes across model strata. Results: The study population comprised 1108 patients with a median age of 53.5 (interquartile range 48-59) y and male predominance (74.9%). All models had excellent areas under the receiver operating characteristic curves for the primary outcome (MELD 0.89, MELD-Na 0.91, MELD-GRAIL 0.89, MELD-GRAIL-Na 0.89; all comparisons P > 0.05). Youden index cutoffs for 90-d mortality were as follows: MELD, 19; MELD-Na, 22; MELD-GRAIL, 18; and MELD-GRAIL-Na, 17. Variables associated with 90-d mortality on multivariable Cox regression were sodium, bilirubin, creatinine, and international normalized ratio. There were no differences in model discrimination using Harrell's C-index. All models were well calibrated; however, divergence between observed and predicted mortality was noted with scores ≥25. Conclusion: There were no demonstrable differences in discrimination or calibration of GRAIL-based models compared with MELD or MELD-Na in our cohort. This suggests that GRAIL-based models may not have meaningful improvements in discriminatory ability when applied to other settings.

Australian fire nourishes ocean phytoplankton bloom.

An unprecedented devastating forest fire occurred in Australia from September 2019 to March 2020. Satellite observations revealed that this rare fire event in Australia destroyed a record amount of more than 202,387 km2 of forest, including 56,471 km2 in eastern Australia, which is mostly composed of evergreen forest. The released aerosols contained essential nutrients for the growth of marine phytoplankton and were transported by westerly winds over the Southern Ocean, with rainfall-induced deposition to the ocean beneath. Here, we show that a prominent oceanic bloom, indicated by the rapid growth of phytoplankton, took place in the Southern Ocean along the trajectory of fire-born aerosols in response to atmospheric deposition. Calculations of carbon released during the fire versus carbon absorbed by the oceanic phytoplankton bloom suggest that they were nearly equal. This finding illustrates the critical role of the oceans in mitigating natural and anthropogenic carbon dioxide releases to the atmosphere, which are a primary driver of climate change.

Exploring Variability of Trichodesmium Photophysiology Using Multi-Excitation Wavelength Fast Repetition Rate Fluorometry.

Fast repetition rate fluorometry (FRRf) allows for rapid non-destructive assessment of phytoplankton photophysiology in situ yet has rarely been applied to Trichodesmium. This gap reflects long-standing concerns that Trichodesmium (and other cyanobacteria) contain pigments that are less effective at absorbing blue light which is often used as the sole excitation source in FRR fluorometers-potentially leading to underestimation of key fluorescence parameters. In this study, we use a multi-excitation FRR fluorometer (equipped with blue, green, and orange LEDs) to investigate photophysiological variability in Trichodesmium assemblages from two sites. Using a multi-LED measurement protocol (447+519+634 nm combined), we assessed maximum photochemical efficiency (F v /F m ), functional absorption cross section of PSII (σ PSII ), and electron transport rates (ETRs) for Trichodesmium assemblages in both the Northwest Pacific (NWP) and North Indian Ocean in the vicinity of Sri Lanka (NIO-SL). Evaluating fluorometer performance, we showed that use of a multi-LED measuring protocol yields a significant increase of F v /F m for Trichodesmium compared to blue-only excitation. We found distinct photophysiological differences for Trichodesmium at both locations with higher average F v /F m as well as lower σ PSII and non-photochemical quenching (NPQ NSV ) observed in the NWP compared to the NIO-SL (Kruskal-Wallis t-test df = 1, p < 0.05). Fluorescence light response curves (FLCs) further revealed differences in ETR response with a lower initial slope (α ETR ) and higher maximum electron turnover rate ( E T R P S I I m a x ) observed for Trichodesmium in the NWP compared to the NIO-SL, translating to a higher averaged light saturation E K (= E T R P S I I m a x /α ETR ) for cells at this location. Spatial variations in physiological parameters were both observed between and within regions, likely linked to nutrient supply and physiological stress. Finally, we applied an algorithm to estimate primary productivity of Trichodesmium using FRRf-derived fluorescence parameters, yielding an estimated carbon-fixation rate ranging from 7.8 to 21.1 mgC mg Chl-a-1 h-1 across this dataset. Overall, our findings demonstrate that capacity of multi-excitation FRRf to advance the application of Chl-a fluorescence techniques in phytoplankton assemblages dominated by cyanobacteria and reveals novel insight into environmental regulation of photoacclimation in natural Trichodesmium populations.

Engineering a non-native hydrogen production pathway into Escherichia coli via a cyanobacterial [NiFe] hydrogenase.

Biotechnology is a promising approach for the generation of hydrogen, but is not yet commercially viable. Metabolic engineering is a potential solution, but has largely been limited to native pathway optimisation. To widen opportunities for use of non-native [NiFe] hydrogenases for improved hydrogen production, we introduced a cyanobacterial hydrogen production pathway and associated maturation factors into Escherichia coli. Hydrogen production is observed in vivo in a hydrogenase null host, demonstrating coupling to host electron transfer systems. Hydrogenase activity is also detected in vitro. Hydrogen output is increased when formate production is abolished, showing that the new pathway is distinct from the native formate dependent pathway and supporting the conclusion that it couples cellular NADH and NADPH pools to molecular hydrogen. This work demonstrates non-native hydrogen production in E. coli, showing the wide portability of [NiFe] hydrogenase pathways and the potential for metabolic engineering to improve hydrogen yields.

Structure of tumor suppressor p53 and its intrinsically disordered N-terminal transactivation domain.

Proteins with intrinsically disordered domains are implicated in a vast range of biological processes, especially in cell signaling and regulation. Having solved the quaternary structure of the folded domains in the tumor suppressor p53 by a multidisciplinary approach, we have now determined the average ensemble structure of the intrinsically disordered N-terminal transactivation domain (TAD) by using residual dipolar couplings (RDCs) from NMR spectroscopy and small-angle x-ray scattering (SAXS). Remarkably, not only were we able to measure RDCs of the isolated TAD, but we were also able to do so for the TAD in both the full-length tetrameric p53 protein and in its complex with a specific DNA response element. We determined the orientation of the TAD ensemble relative to the core domain, found that the TAD was stiffer in the proline-rich region (residues 64-92), which has a tendency to adopt a polyproline II (PPII) structure, and projected the TAD away from the core. We located the TAD in SAXS experiments on a complex between tetrameric p53 and four Taz2 domains that bind tightly to the TAD (residues 1-57) and acted as "reporters." The p53-Taz2 complex was an extended cross-shaped structure. The quality of the SAXS data enabled us to model the disordered termini and the folded domains in the complex with DNA. The core domains enveloped the response element in the center of the molecule, with the Taz2-bound TADs projecting outward from the core.

Split-Thickness Skin Grafting: A Primer for Orthopaedic Surgeons.

Soft-tissue defects pose a unique challenge to the treating orthopaedic surgeon. Such defects are commonly encountered after orthopaedic injuries or infection, and the management of these wounds varies significantly. Skin grafting has gained popularity in the management of such soft-tissue defects due to its ability to provide coverage, re-epithelialize, and have a relatively high success rate. One of the most frequently used types of skin graft in orthopaedics is the split-thickness skin graft (STSG). Understanding the proper indications, technique, and management of the STSG foreshadows its success or failure. This review focuses on the indications, technique, alternatives, and complications surrounding the utilization of the STSG in the management of orthopaedic injuries.

Experimental Techniques to Assess Coral Physiology in situ Under Global and Local Stressors: Current Approaches and Novel Insights.

Coral reefs are declining worldwide due to global changes in the marine environment. The increasing frequency of massive bleaching events in the tropics is highlighting the need to better understand the stages of coral physiological responses to extreme conditions. Moreover, like many other coastal regions, coral reef ecosystems are facing additional localized anthropogenic stressors such as nutrient loading, increased turbidity, and coastal development. Different strategies have been developed to measure the health status of a damaged reef, ranging from the resolution of individual polyps to the entire coral community, but techniques for measuring coral physiology in situ are not yet widely implemented. For instance, while there are many studies of the coral holobiont response in single or limited-number multiple stressor experiments, they provide only partial insights into metabolic performance under more complex and temporally and spatially variable natural conditions. Here, we discuss the current status of coral reefs and their global and local stressors in the context of experimental techniques that measure core processes in coral metabolism (respiration, photosynthesis, and biocalcification) in situ, and their role in indicating the health status of colonies and communities. We highlight the need to improve the capability of in situ studies in order to better understand the resilience and stress response of corals under multiple global and local scale stressors.

The H187R mutation of the human prion protein induces conversion of recombinant prion protein to the PrP(Sc)-like form.

Prion diseases are associated with a conformational switch in the prion protein (PrP) from its normal cellular form (denoted PrP(C)) to a disease-associated "scrapie" form (PrP(Sc)). A number of PrP(Sc)-like conformations can be generated by incubating recombinant PrP(C) at low pH, indicating that protonation of key residues is likely to destabilize PrP(C), facilitating its conversion to PrP(Sc). Here, we examine the stability of human PrP(C) with pH and find that PrP(C) fold stability is significantly reduced by the protonation of two histidine residues, His187 and His155. Mutation of His187 to an arginine, which imposes a permanently positively charged residue in this region of the protein, has a dramatic effect on the folding of PrP(C), resulting in a molecule that displays a markedly increased propensity to oligomerize. The oligomeric form is characterized by an increased ß-sheet content, loss of fixed side chain interactions, and partial proteinase resistance. Hence, the protonation state of H187 appears to be crucial in determining the conformation of PrP; the unprotonated form favors native PrP(C), while the protonated form favors PrP(Sc)-like conformations. These results are relevant to the pathogenic H187R mutation found in humans, which is associated with an inherited prion disease [also termed Gerstmann-Sträussler-Scheinker (GSS) syndrome] with unusual features such as childhood neuropsychiatric illness. Our data imply that the intrinsic instability of the PrP(C) conformation in this variant is caused by a positive charge at this site in the protein. This mutation is distinct from all those associated with GSS, which have much more subtle physical consequences. The degree of instability might be the cause of the unusually early onset of mental disturbance in affected individuals.

14-3-3 activation of DNA binding of p53 by enhancing its association into tetramers.

Activation of the tumour suppressor p53 on DNA damage involves post-translational modification by phosphorylation and acetylation. Phosphorylation of certain residues is critical for p53 stabilization and plays an important role in DNA-binding activity. The 14-3-3 family of proteins activates the DNA-binding affinity of p53 upon stress by binding to a site in its intrinsically disordered C-terminal domain containing a phosphorylated serine at 378. We have screened various p53 C-terminal phosphorylated peptides for binding to two different isoforms of 14-3-3, epsilon and gamma. We found that phosphorylation at either S366 or T387 caused even tighter binding to 14-3-3. We made by semi-synthesis a tetrameric construct comprised of the tetramerization plus C-terminal domains of p53 that was phosphorylated on S366, S378 and T387. It bound 10 times tighter than did the monomeric counterpart to dimeric 14-3-3. We showed indirectly from binding curves and directly from fluorescence-detection analytical ultracentrifugation that 14-3-3 enhanced the binding of sequence-specific DNA to p53 by causing p53 dimers to form tetramers at lower concentrations. If the in vitro data extrapolate to in vivo, then it is an attractive hypothesis that p53 activity may be subject to control by accessory proteins lowering its tetramer-dimer dissociation constant from its normal value of 120-150 nM.

Metabolic performance and thermal and salinity tolerance of the coral Platygyra carnosa in Hong Kong waters.

Stress-tolerant coral species, such as Platygyra spp., are considered to be well adapted to survive in marginal reefs, but their physiological response to short term exposure to abnormally high temperature and lowered salinity remains poorly understood. Using non-invasive techniques to quantitatively assess the health of Platygyra carnosa (e.g. respiration, photosynthesis, biocalcification and whiteness), we identified the plasticity of its energetics and physiological limits. Although these indicators suggest that it can survive to increasing temperature (25-32 °C), its overall energetics were seriously diminished at temperatures >30 °C. In contrast, it was well adapted to hyposaline waters (31-21 psu) but with reduced biocalcification, indicating short term adaptation for expected future changes in salinity driven by increased amounts and intensities of precipitation. Our findings provide useful insights to the effect of these climate drivers on P. carnosa metabolism and thus better forecast changes in their health status under future climate change scenarios.