Modulation of ligand-heme reactivity by binding pocket residues demonstrated in cytochrome c' over the femtosecond-second temporal range

The ability of hemoproteins to discriminate between diatomic molecules, and the subsequent affinity for their chosen ligand, is fundamental to the existence of life. These processes are often controlled by precise structural arrangements in proteins, with heme pocket residues driving reactivity and specificity. One such protein is cytochrome c', which has the ability to bind nitric oxide (NO) and carbon monoxide (CO) on opposite faces of the heme, a property that is shared with soluble guanylate cycle. Like soluble guanylate cyclase, cytochrome c' also excludes O completely from the binding pocket. Previous studies have shown that the NO binding mechanism is regulated by a proximal arginine residue (R124) and a distal leucine residue (L16). Here, we have investigated the roles of these residues in maintaining the affinity for NO in the heme binding environment by using various time-resolved spectroscopy techniques that span the entire femtosecond-second temporal range in the UV-vis spectrum, and the femtosecond-nanosecond range by IR spectroscopy. Our findings indicate that the tightly regulated NO rebinding events following excitation in wild-type cytochrome c' are affected in the R124A variant. In the R124A variant, vibrational and electronic changes extend continuously across all time scales (from fs-s), in contrast to wild-type cytochrome c' and the L16A variant. Based on these findings, we propose a NO (re)binding mechanism for the R124A variant of cytochrome c' that is distinct from that in wild-type cytochrome c'. In the wider context, these findings emphasize the importance of heme pocket architecture in maintaining the reactivity of hemoproteins towards their chosen ligand, and demonstrate the power of spectroscopic probes spanning a wide temporal range. © 2013 FEBS.

Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Reconfigurable self-assembly through chiral control of interfacial tension

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 481 (2012): 348–351, doi:10.1038/nature10769.From determining optical properties of simple molecular crystals to establishing preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical, and optical properties of both synthetic and biological matter at macroscopic lengthscales1,2. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials3-6. An example of particular interest is smectic liquid crystals, where the 2D layered geometry cannot support twist, expelling chirality to the edges in a manner analogous to the expulsion of a magnetic field from superconductors7-10. Here, we demonstrate a previously unexplored consequence of this geometric frustration which leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes11, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This finding suggests an analogy between chiral twist which is expelled to the edge of 2D membranes, and amphiphilic surfactants which are expelled to oil-water interfaces12. Similar to surfactants, chiral control of interfacial tension drives the assembly of myriad polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ enables dynamical control of line tension that powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials which can easily be moved, stretched, attached to one another, and transformed between multiple conformational states, thus enabling precise assembly and nano-sculpting of highly dynamical and designable materials with complex topologies.This work was supported by the National Science Foundation (NSF-MRSEC-0820492, NSF-DMR-0955776, NSF-MRI 0923057) and Petroleum Research Fund (ACS-PRF 50558-DNI7).2012-07-0

Left ventricular twist mechanics during incremental cycling and knee extension exercise in healthy men

Purpose: The objective of the present study was to investigate left ventricular (LV) twist mechanics in response to incremental cycling and isometric knee extension exercises. Methods: Twenty-six healthy male participants (age = 30.42 ± 6.17 years) were used to study peak twist mechanics at rest and during incremental semi-supine cycling at 30 and 60% work rate maximum (W) and during short duration (15 s contractions) isometric knee extension at 40 and 75% maximum voluntary contraction (MVC), using two-dimensional speckle tracking echocardiography. Results: Data presented as mean ± standard deviation or median (interquartile range). LV twist increased from rest to 30% W (13.21° ± 4.63° to 20.04° ± 4.76°, p  0.05), whilst twisting velocity increased (rest 89.15° ± 21.77° s to 75% MVC 124.32° ± 34.89° s, p  0.05) then increased from 40 to 75% MVC [−98.44 (43.54)° s to −138.42 (73.29)° s, p < 0.01]. Apical rotations and rotational velocities were greater than basal during all conditions and intensities (all p < 0.01). Conclusion: Cycling increased LV twist to 30% W which then remained unchanged thereafter, whereas twisting velocities showed further increases to greater intensities. A novel finding is that LV twist was unaffected by incremental knee extension, yet systolic and diastolic twisting velocities augmented with isometric exercise

Claudin-containing exosomes in the peripheral circulation of women with ovarian cancer

<p>Abstract</p> <p>Background</p> <p>The absence of highly sensitive and specific serum biomarkers makes mass screening for ovarian cancer impossible. The claudin proteins are frequently overexpressed in ovarian cancers, but their potential as prognostic, diagnostic, or detection markers remains unclear. Here, we have explored the possible use of these proteins as screening biomarkers for ovarian cancer detection.</p> <p>Methods</p> <p>Claudin protein shedding from cells was examined by immunoblotting of conditioned culture media. The presence of claudins in exosomes released from ovarian cancer cells was demonstrated by sucrose gradient separation and immunogold electron microscopy experiments. Claudin-4-containing exosomes in the plasma of ovarian cancer patients were evaluated in a pilot panel of 63 ovarian cancer patients and 50 healthy volunteers. The CA125 marker was also assessed in these samples and compared with claudin-4 positivity.</p> <p>Results</p> <p>We show that full-length claudins can be shed from ovarian cancer cells in culture and found in the media as part of small lipid vesicles known as exosomes. Moreover, 32 of 63 plasma samples from ovarian cancer patients exhibited the presence of claudin-4-containing exosomes. In contrast, only one of 50 samples from individuals without cancer exhibited claudin-4-positive exosomes. In our small panel, at a specificity of 98%, the claudin-4 and CA125 tests had sensitivities of 51% and 71%, respectively. The two tests did not appear to be independent and were strongly correlated.</p> <p>Conclusion</p> <p>Our work shows for the first time that claudin-4 can be released from ovarian cancer cells and can be detected in the peripheral circulation of ovarian cancer patients. The development of sensitive assays for the detection of claudin-4 in blood will be crucial in determining whether this approach can be useful, alone or in combination with other screening methods, for the detection of ovarian cancer.</p

Amelioration of Streptozotocin-Induced Diabetes in Mice with Cells Derived from Human Marrow Stromal Cells

Pluri-potent bone marrow stromal cells (MSCs) provide an attractive opportunity to generate unlimited glucose-responsive insulin-producing cells for the treatment of diabetes. We explored the potential for human MSCs (hMSCs) to be differentiated into glucose-responsive cells through a non-viral genetic reprogramming approach.Two HMSC lines were transfected with three genes: PDX-1, NeuroD1 and Ngn3 without subsequent selection, followed by differentiation induction in vitro and transplantation into diabetic mice. Human MSCs expressed mRNAs of the archetypal stem cell markers: Sox2, Oct4, Nanog and CD34, and the endocrine cell markers: PDX-1, NeuroD1, Ngn3, and Nkx6.1. Following gene transfection and differentiation induction, hMSCs expressed insulin in vitro, but were not glucose regulated. After transplantation, hMSCs differentiated further and approximately 12.5% of the grafted cells expressed insulin. The graft bearing kidneys contained mRNA of insulin and other key genes required for the functions of beta cells. Mice transplanted with manipulated hMSCs showed reduced blood glucose levels (from 18.9+/-0.75 to 7.63+/-1.63 mM). 13 of the 16 mice became normoglycaemic (6.9+/-0.64 mM), despite the failure to detect the expression of SUR1, a K(+)-ATP channel component required for regulation of insulin secretion.Our data confirm that hMSCs can be induced to express insulin sufficient to reduce blood glucose in a diabetic mouse model. Our triple gene approach has created cells that seem less glucose responsive in vitro but which become more efficient after transplantation. The maturation process requires further study, particularly the in vivo factors influencing the differentiation, in order to scale up for clinical purposes

Left ventricular speckle tracking-derived cardiac strain and cardiac twist mechanics in athletes: a systematic review and meta-analysis of controlled studies

Background: The athlete’s heart is associated with physiological remodeling as a consequence of repetitive cardiac loading. The effect of exercise training on left ventricular (LV) cardiac strain and twist mechanics are equivocal, and no meta-analysis has been conducted to date. Objective: The objective of this systematic review and meta-analysis was to review the literature pertaining to the effect of different forms of athletic training on cardiac strain and twist mechanics and determine the influence of traditional and contemporary sporting classifications on cardiac strain and twist mechanics. Methods: We searched PubMed/MEDLINE, Web of Science, and ScienceDirect for controlled studies of aged-matched male participants aged 18–45 years that used two-dimensional (2D) speckle tracking with a defined athlete sporting discipline and a control group not engaged in training programs. Data were extracted independently by two reviewers. Random-effects meta-analyses, subgroup analyses, and meta-regressions were conducted. Results: Our review included 13 studies with 945 participants (controls n = 355; athletes n = 590). Meta-analyses showed no athlete–control differences in LV strain or twist mechanics. However, moderator analyses showed greater LV twist in high-static low-dynamic athletes (d = –0.76, 95% confidence interval [CI] –1.32 to –0.20; p < 0.01) than in controls. Peak untwisting velocity (PUV) was greater in high-static low-dynamic athletes (d = –0.43, 95% CI –0.84 to –0.03; p < 0.05) but less than controls in high-static high-dynamic athletes (d = 0.79, 95% CI 0.002–1.58; p = 0.05). Elite endurance athletes had significantly less twist and apical rotation than controls (d = 0.68, 95% CI 0.19–1.16, p < 0.01; d = 0.64, 95% CI 0.27–1.00, p = 0.001, respectively) but no differences in basal rotation. Meta-regressions showed LV mass index was positively associated with global longitudinal (b = 0.01, 95% CI 0.002–0.02; p < 0.05), whereas systolic blood pressure was negatively associated with PUV (b = –0.06, 95% CI –0.13 to –0.001; p = 0.05). Conclusion: Echocardiographic 2D speckle tracking can identify subtle physiological differences in adaptations to cardiac strain and twist mechanics between athletes and healthy controls. Differences in speckle tracking echocardiography-derived parameters can be identified using suitable sporting categorizations