Mn-porphyrins in a four-helix bundle participate in photo-induced electron transfer with a bacterial reaction center.

Hybrid complexes incorporating synthetic Mn-porphyrins into an artificial four-helix bundle domain of bacterial reaction centers created a system to investigate new electron transfer pathways. The reactions were initiated by illumination of the bacterial reaction centers, whose primary photochemistry involves electron transfer from the bacteriochlorophyll dimer through a series of electron acceptors to the quinone electron acceptors. Porphyrins with diphenyl, dimesityl, or fluorinated substituents were synthesized containing either Mn or Zn. Electrochemical measurements revealed potentials for Mn(III)/Mn(II) transitions that are ~ 0.4 V higher for the fluorinated Mn-porphyrins than the diphenyl and dimesityl Mn-porphyrins. The synthetic porphyrins were introduced into the proteins by binding to a four-helix bundle domain that was genetically fused to the reaction center. Light excitation of the bacteriochlorophyll dimer of the reaction center resulted in new derivative signals, in the 400 to 450 nm region of light-minus-dark spectra, that are consistent with oxidation of the fluorinated Mn(II) porphyrins and reduction of the diphenyl and dimesityl Mn(III) porphyrins. These features recovered in the dark and were not observed in the Zn(II) porphyrins. The amplitudes of the signals were dependent upon the oxidation/reduction midpoint potentials of the bacteriochlorophyll dimer. These results are interpreted as photo-induced charge-separation processes resulting in redox changes of the Mn-porphyrins, demonstrating the utility of the hybrid artificial reaction center system to establish design guidelines for novel electron transfer reactions.

Domain wall energy and strain in Pt/Co/Ir thin films on piezoelectric transducers.

We study the energy and creep velocity of magnetic domain walls in perpendicularly magnetised Pt/Co/Ir thin films under strain. We find that the enhancement of domain wall creep velocity under strain from piezoelectric transducers is largest in films with the thinnest Co layers (0.56 nm), in which the strain causes the smallest relative change in perpendicular magnetic anisotropy and the largest relative change in domain wall creep velocity. We show how domain wall energy is predictive of the sensitivity of domain wall creep velocity to changes in strain, and thus provide a route to designing magnetic thin film systems for optimum strain control.

Pinning and hysteresis in the field dependent diameter evolution of skyrmions in Pt/Co/Ir superlattice stacks.

We have imaged Néel skyrmion bubbles in perpendicularly magnetised polycrystalline multilayers patterned into 1 µm diameter dots, using scanning transmission x-ray microscopy. The skyrmion bubbles can be nucleated by the application of an external magnetic field and are stable at zero field with a diameter of 260 nm. Applying an out of plane field that opposes the magnetisation of the skyrmion bubble core moment applies pressure to the bubble and gradually compresses it to a diameter of approximately 100 nm. On removing the field the skyrmion bubble returns to its original diameter via a hysteretic pathway where most of the expansion occurs in a single abrupt step. This contradicts analytical models of homogeneous materials in which the skyrmion compression and expansion are reversible. Micromagnetic simulations incorporating disorder can explain this behaviour using an effective thickness modulation between 10 nm grains.

IL-36γ is a crucial proximal component of protective type-1-mediated lung mucosal immunity in Gram-positive and -negative bacterial pneumonia.

Interleukin-36γ (IL-36γ) is a member of novel IL-1-like proinflammatory cytokine family that are highly expressed in epithelial tissues and several myeloid-derived cell types. Little is known about the role of the IL-36 family in mucosal immunity, including lung anti-bacterial responses. We used murine models of IL-36γ deficiency to assess the contribution of IL-36γ in the lung during experimental pneumonia. Induction of IL-36γ was observed in the lung in response to Streptococcus pneumoniae (Sp) infection, and mature IL-36γ protein was secreted primarily in microparticles. IL-36γ-deficient mice challenged with Sp demonstrated increased mortality, decreased lung bacterial clearance and increased bacterial dissemination, in association with reduced local expression of type-1 cytokines, and impaired lung macrophage M1 polarization. IL-36γ directly stimulated type-1 cytokine induction from dendritic cells in vitro in a MyD88-dependent manner. Similar protective effects of IL-36γ were observed in a Gram-negative pneumonia model (Klebsiella pneumoniae). Intrapulmonary delivery of IL-36γ-containing microparticles reconstituted immunity in IL-36γ-/- mice. Enhanced expression of IL-36γ was also observed in plasma and bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome because of pneumonia. These studies indicate that IL-36γ assumes a vital proximal role in the lung innate mucosal immunity during bacterial pneumonia by driving protective type-1 responses and classical macrophage activation.

Assessment of resuscitation as measured by markers of metabolic acidosis and features of injury.

AIMS: The best time for definitive orthopaedic care is often unclear in patients with multiple injuries. The objective of this study was make a prospective assessment of the safety of our early appropriate care (EAC) strategy and to evaluate the potential benefit of additional laboratory data to determine readiness for surgery. PATIENTS AND METHODS: A cohort of 335 patients with fractures of the pelvis, acetabulum, femur, or spine were included. Patients underwent definitive fixation within 36 hours if one of the following three parameters were met: lactate < 4.0 mmol/L; pH ≥ 7.25; or base excess (BE) ≥ -5.5 mmol/L. If all three parameters were met, resuscitation was designated full protocol resuscitation (FPR). If less than all three parameters were met, it was designated an incomplete protocol resuscitation (IPR). Complications were assessed by an independent adjudication committee and included infection; sepsis; PE/DVT; organ failure; pneumonia, and acute respiratory distress syndrome (ARDS). RESULTS: In total, 66 patients (19.7%) developed 90 complications. An historical cohort of 1441 patients had a complication rate of 22.1%. The complication rate for patients with only one EAC parameter at the point of protocol was 34.3%, which was higher than other groups (p = 0.041). Patients who had IPR did not have significantly more complications (31.8%) than those who had FPR (22.6%; p = 0.078). Regression analysis showed male gender and injury severity score to be independent predictors of complications. CONCLUSIONS: This study highlights important trends in the IPR and FPR groups, suggesting that differences in resuscitation parameters may guide care in certain patients; further study is, however, required. We advocate the use of the existing protocol, while research is continued for high-risk subgroups. Cite this article: Bone Joint J 2017;99-B:122-7.

Is Early Appropriate Care of axial and femoral fractures appropriate in multiply-injured elderly trauma patients?

BACKGROUND: Previous work established resuscitation parameters that minimize complications with early fracture management. This Early Appropriate Care (EAC) protocol was applied to patients with advanced age to determine if they require unique parameters to mitigate complications. METHODS: Between October 2010 and March 2013, 376 consecutive skeletally mature patients with unstable fractures of the pelvis, acetabulum, thoracolumbar spine, and/or proximal or diaphyseal femur fractures were treated at a level I trauma center and were prospectively studied. Patients aged ≤30 years (n = 114), 30 to 60 years (n = 184), and ≥60 years (n = 37) with Injury Severity Scores (ISS) ≥16 and unstable fractures of the pelvis, acetabulum, spine, and/or diaphyseal femur were treated within 36 h, provided they showed evidence of adequate resuscitation. ISS, Glasgow Coma Scale (GCS), and American Society of Anesthesiologists (ASA) classification were determined. Lactate, pH, and base excess (BE) were measured at 8-h intervals. Complications included pneumonia, pulmonary embolism (PE), acute renal failure, acute respiratory distress syndrome (ARDS), multiple organ failure (MOF), deep vein thrombosis, infection, sepsis, and death. RESULTS: Patients ≤30 years old (y/o) were more likely to sustain gunshot wounds (p = 0.039), while those ≥60 y/o were more likely to fall from a height (p = 0.002). Complications occurred at similar rates for patients ≤30 y/o, 30 to 60 y/o, and ≥60 y/o. There were no differences in lactate, pH, or BE at the time of surgery. For patients ≤30 y/o, there were increased overall complications if pH was <7.30 (p = 0.042) or BE <-6.0 (p = 0.049); patients ≥60 y/o demonstrated more sepsis if BE was <-6.0 (p = 0.046). CONCLUSIONS: EAC aims to definitively manage axial and femoral shaft fractures once patients have been adequately resuscitated to minimize complications. EAC is associated with comparable complication rates in young and elderly patients. Further study is warranted with a larger sample to further validate EAC in elderly patients. LEVEL OF EVIDENCE: level II prospective, comparative study.

Maternal variables associated with physiologic stress and perinatal complications in preterm infants.

OBJECTIVE: Complications of prematurity may be related to dysregulation of the hypothalamic-pituitary-adrenal axis in preterm infants. Increased intrauterine exposure to cortisol may be responsible for adverse prenatal programming and subsequent dysfunction of the infant's hypothalamic-pituitary-adrenal axis. The aim of the study was to describe maternal social variables and their association with infant cortisol levels and complications of prematurity. METHODS: Preterm infants <32 weeks' gestation were recruited. Primary outcomes were development of complications of prematurity and physiologic stress response, represented by cord blood and salivary cortisol levels on first day of life. Descriptive statistics and comparative analyses were performed. RESULTS: Fifteen of 31 infants enrolled developed a complication of prematurity. Infants of greater gestational age when prenatal care was established had lower cord blood cortisol (p = 0.009) and trended a higher risk of necrotizing enterocolitis (p = 0.069). Infants whose mothers smoked more showed significantly different salivary cortisol distributions on day 1 (p = 0.037), and were at greater risk for intraventricular hemorrhage (p = 0.018). CONCLUSIONS: The association between maternal social variables, hypothalamic-pituitary-adrenal axis dysregulation, and complications of prematurity supports the research model of physiologic dysregulation/allostatic load as a mechanism for complications in preterm infants. More research is warranted to investigate associations between maternal social variables, maternal stress levels, and adverse prenatal programming of the infant hypothalamic-pituitary-adrenal axis.

Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer.

The microscopic magnetization variation in magnetic domain walls in thin films is a crucial property when considering the torques driving their dynamic behaviour. For films possessing out-of-plane anisotropy normally the presence of Néel walls is not favoured due to magnetostatic considerations. However, they have the right structure to respond to the torques exerted by the spin Hall effect. Their existence is an indicator of the interfacial Dzyaloshinskii-Moriya interaction (DMI). Here we present direct imaging of Néel domain walls with a fixed chirality in device-ready Pt/Co/AlOx films using Lorentz transmission electron and Kerr microscopies. It is shown that any independently nucleated pair of walls in our films form winding pairs when they meet that are difficult to annihilate with field, confirming that they all possess the same topological winding number. The latter is enforced by the DMI. The field required to annihilate these winding wall pairs is used to give a measure of the DMI strength. Such domain walls, which are robust against collisions with each other, are good candidates for dense data storage.

Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain.

The perpendicular magnetic anisotropy K(eff), magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85-1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.

Ultrafast energy transfer and excited state coupling in an artificial photosynthetic antenna.

We have studied the energy transfer dynamics in an artificial light-harvesting dyad composed of a phthalocyanine (Pc) covalently linked to a carotenoid (Car). The combination of high temporal resolution transient absorption spectroscopy with global and target analysis allowed us to quantify the efficiency of the energy transfer from the S2 excited state of the Car to the Pc at 37%, close to values observed in some natural light-harvesting complexes. In addition, following selective excitation of the Pc, we have identified the spectral signatures of the S1 excited state of the Car which appear within the ≈30 fs time resolution of our measurement. This strongly indicates excited state coupling between the S1 state of Car and the Qx state of Pc, with important implications for the regulation of photosynthetic activity.

Natural attenuation of septic system nitrogen by anammox.

On-site disposal of sewage in septic systems can lead to groundwater plumes with NO(3)(-)-N concentrations exceeding the common drinking water limit of 10 mg/L. Currently, denitrification is considered as the principal natural attenuation process. However, at a large seasonal-use septic system in Ontario (256 campsites), a suboxic zone exists where nitrogen removal of up to 80% occurs including removal of NH(4)(+)-N. This zone has both NO(3)(-)-N and NH(4)(+)-N at >5 mg/L each. In the distal NH(4)(+)-rich zone, NH(4)(+)-N concentrations (8.1 ± 8.0 mg/L) are lower than in the proximal zone (48 ± 36 mg/L) and NH(4)(+)-N is isotopically enriched (concentration-weighted mean δ(15)N of +15.7‰) compared to the proximal zone (+7.8‰). Furthermore, δ(15)N-NH(4)(+) isotopic enrichment increases with depth in the distal zone, which is opposite to what would result if nitrification along the water table zone was the mechanism causing NH(4)(+) depletion. Bacterial community composition was assessed with molecular (DNA-based) analysis and demonstrated that groundwater bacterial populations were predominantly composed of bacteria from two Candidatus genera of the Planctomycetales (Brocadia and Jettenia). Together, these data provide strong evidence that anaerobic ammonium oxidation (anammox) plays an important role in nitrogen attenuation at this site.

Domain-wall depinning assisted by pure spin currents.

We study the depinning of domain walls by pure diffusive spin currents in a nonlocal spin valve structure based on two ferromagnetic Permalloy elements with copper as the nonmagnetic spin conduit. The injected spin current is absorbed by the second Permalloy structure with a domain wall, and from the dependence of the wall depinning field on the spin current density we find an efficiency of 6×10{-14} T/(A/m{2}), which is more than an order of magnitude larger than for conventional current induced domain-wall motion. Theoretically we find that this high efficiency arises from the surface torques exerted by the absorbed spin current that lead to efficient depinning.

Relationship between nonadiabaticity and damping in permalloy studied by current induced spin structure transformations.

By direct imaging we determine spin structure changes in Permalloy wires and disks due to spin transfer torque as well as the critical current densities for different domain wall types. Periodic domain wall transformations from transverse to vortex walls and vice versa are observed, and the transformation mechanism occurs by vortex core displacement perpendicular to the wire. The results imply that the nonadiabaticity parameter beta does not equal the damping alpha, in agreement with recent theoretical predictions. The vortex core motion perpendicular to the current is further studied in disks revealing that the displacement in opposite directions can be attributed to different polarities of the vortex core.

The design and synthesis of artificial photosynthetic antennas, reaction centres and membranes.

Artificial antenna systems and reaction centres synthesized in our laboratory are used to illustrate that structural and thermodynamic factors controlling energy and electron transfer in these constructs can be modified to optimize performance. Artificial reaction centres have been incorporated into liposomal membranes where they convert light energy to vectorial redox potential. This redox potential drives a Mitchellian, quinone-based, proton-transporting redox loop that generates a Deltamu H(+) of ca. 4.4 kcal mol(-1) comprising DeltapH ca. 2.1 and Deltapsi ca. 70 mV. In liposomes containing CF(0)F(1)-ATP synthase, this system drives ATP synthesis against an ATP chemical potential similar to that observed in natural systems.

Bias-induced forces in conducting atomic force microscopy and contact charging of organic monolayers.

Contact electrification, a surface property of bulk dielectric materials, has now been observed at the molecular scale using conducting atomic force microscopy (AFM). Conducting AFM measures the electrical properties of an organic film sandwiched between a conducting probe and a conducting substrate. This paper describes physical changes in the film caused by the application of a bias. Contact of the probe leads to direct mechanical stress and the applied electric field results in both Maxwell stresses and electrostriction. Additional forces arise from charge injection (contact charging). Electrostriction and contact charging act oppositely from the normal long-range Coulomb attraction and dominate when a charged tip touches an insulating film, causing the tip to deflect away from the film at high bias. A bias-induced repulsion observed in spin-coated PMMA films may be accounted for by either mechanism. In self-assembled monolayers, however, tunnel current signals show that the repulsion is dominated by contact charging.

Reproducible measurement of single-molecule conductivity.

A reliable method has been developed for making through-bond electrical contacts to molecules. Current-voltage curves are quantized as integer multiples of one fundamental curve, an observation used to identify single-molecule contacts. The resistance of a single octanedithiol molecule was 900 +/- 50 megohms, based on measurements on more than 1000 single molecules. In contrast, nonbonded contacts to octanethiol monolayers were at least four orders of magnitude more resistive, less reproducible, and had a different voltage dependence, demonstrating that the measurement of intrinsic molecular properties requires chemically bonded contacts.

Protection from pulmonary fibrosis in the absence of CCR2 signaling.

Pulmonary fibrosis can be modeled in animals by intratracheal instillation of FITC, which results in acute lung injury, inflammation, and extracellular matrix deposition. We have previously shown that despite chronic inflammation, this model of pulmonary fibrosis is lymphocyte independent. The CC chemokine monocyte-chemoattractant protein-1 is induced following FITC deposition. Therefore, we have investigated the contribution of the main monocyte-chemoattractant protein-1 chemokine receptor, CCR2, to the fibrotic disease process. We demonstrate that CCR2(-/-) mice are protected from fibrosis in both the FITC and bleomycin pulmonary fibrosis models. The protection is specific for the absence of CCR2, as CCR5(-/-) mice are not protected. The protection is not explained by differences in acute lung injury, or the magnitude or composition of inflammatory cells. FITC-treated CCR2(-/-) mice display differential patterns of cellular activation as evidenced by the altered production of cytokines and growth factors following FITC inoculation compared with wild-type controls. CCR2(-/-) mice have increased levels of GM-CSF and reduced levels of TNF-alpha compared with FITC-treated CCR2(+/+) mice. Thus, CCR2 signaling promotes a profibrotic cytokine cascade following FITC administration.

Photoswitched singlet energy transfer in a porphyrin-spiropyran dyad.

A photochromic nitrospiropyran moiety (Sp) has been covalently linked to a zinc (PZn) and to a free-base (P(H2)) porphyrin. In the resulting dyads (P(Zn)-Sp(c) and P(H2)-Sp(c)), the porphyrin first excited singlet states are unperturbed by the closed form of the attached spiropyran. Excitation of the spiropyran moiety of either dyad in the near-UV region results in ring opening to a merocyanine form (P-Sp(o)) that absorbs at 600 nm. The open form re-closes thermally in 2-methyltetrahydrofuran with a time constant of 20 s, or following irradiation into the 600 nm band. Excitation of the zinc porphyrin moiety in the merocyanine form of the dyad yields 1PZn-Sp(o). The lifetime of the zinc porphyrin excited state is reduced from its usual value of 1.8 ns to 130 ps by singlet-singlet energy transfer to the merocyanine moiety to give PZn-1Sp(o). The quantum yield of energy transfer is 0.93. Quenching is also observed in the free base dyad, where 1P(H2)-Sp(o) and P(H2)-1Sp(o) exchange singlet excitation energy. This photoswitchable quenching phenomenon provides light-activated control of the porphyrin excited states, and consequently control of any subsequent energy or electron-transfer processes that might be initiated by these excited states in more complex molecular photonic or optoelectronic devices.

Treatment of patients with refractory giardiasis.

Giardia lamblia is one of the most common parasitic infections. Although standard treatments are usually curative, some immunocompromised patients, including patients with acquired immunodeficiency syndrome as well as healthy patients, have giardiasis that is refractory to recommended regimens. We report our experience with 6 patients with giardiasis, for whom therapy with a combination of quinacrine and metronidazole resulted in cures for 5 of the 6 patients.

Cytokine immunotherapy during bacterial pneumonia: from benchtop to bedside.

Bacterial pneumonia is a leading cause of morbidity and mortality within the United States and abroad. Although broad-spectrum antibiotic regiments have led to advances in the treatment of pneumonia, this approach has resulted in the recent emergence of multidrug-resistant bacteria. This adverse effect of aggressive antibiotic therapy underscores the importance for understanding the host inflammatory response to pulmonary bacterial infections. This knowledge can then lead to the development of therapeutic modalities aimed at augmenting host responses, resulting in enhanced resolution of bacterial pneumonia. Ideally, future treatment would combine immunoadjuvant and conventional antibiotic therapy for the treatment of life-threatening bacterial pneumonia. The detailed study of several distinct animal models of bacterial pneumonia has identified cytokines involved in eradication of bacteria deposited within the pulmonary airspace. Furthermore, these studies have led to promising preliminary findings in animal models using therapeutic cytokine immunotherapy.