Assessing the Structure and Equilibrium Conditions of Complex Coacervate Core Micelles by Varying Their Shell Composition and Medium Ionic Strength.

Complex coacervates result from an associative phase separation commonly involving oppositely charged polyelectrolytes. When this associative interaction occurs between charged-neutral diblock copolymers and oppositely charged homopolymers, a nanometric aggregate called a complex coacervate core micelle, C3M, is formed. Recent studies have addressed the issue of their thermodynamic or kinetic stability but without a clear consensus. To further investigate this issue, we have studied C3Ms formed by the combination of poly(diallyldimethylammonium) and copolymer poly(acrylamide)-b-poly(acrylate) using different preparation protocols. Dynamic light scattering and small-angle X-ray scattering measurements suggest that these structures are in an equilibrium condition because the aggregates do not vary with different preparation protocols or upon aging. In addition, their stability and structures are critically dependent on several parameters such as the density of neutral blocks in their shell and the ionic strength of the medium. Decreasing the amount of copolymer in the system and, hence, the density of neutral blocks in the shell results in an increase in the aggregate size because of the core growth, although their globular shape is retained. On the other hand, larger clusters of micelles were formed at higher ionic strengths. Partially replacing 77% of the copolymer with a homopolymer of the same charge or increasing the ionic strength of the system (above 100 mmol L-1 NaCl) leads to a metastable state, after which phase separation is eventually observed. SAXS analyses reveal that this phase separation above a certain salt concentration occurs due to the coagulation of individual micelles that seem to retain their individual globular structures. Overall, these results confirm earlier claims that equilibrium C3Ms are achieved close to 1:1 charge stoichiometry but also reveal that these conditions may vary at different shell densities or higher ionic strengths, which constitute vital information for envisioning future applications of C3Ms.

Early Detection of Optic Nerve Changes on Optical Coherence Tomography Using Deep Learning for Risk-Stratification of Papilledema and Glaucoma.

BACKGROUND: The use of artificial intelligence is becoming more prevalence in medicine with numerous successful examples in ophthalmology. However, much of the work has been focused on replicating the works of ophthalmologists. Given the analytical potentials of artificial intelligence, it is plausible that artificial intelligence can detect microfeatures not readily distinguished by humans. In this study, we tested the potential for artificial intelligence to detect early optic coherence tomography changes to predict progression toward papilledema or glaucoma when no significant changes are detected on optical coherence tomography by clinicians. METHODS: Prediagnostic optical coherence tomography of patients who developed papilledema (n = 93, eyes = 166) and glaucoma (n = 187, eyes = 327) were collected. Given discrepancy in average cup-to-disc ratios of the experimental groups, control groups for papilledema (n = 254, eyes = 379) and glaucoma (n = 441, eyes = 739) are matched by cup-to-disc ratio. Publicly available Visual Geometry Group-19 model is retrained using each experimental group and its respective control group to predict progression to papilledema or glaucoma. Images used for training include retinal nerve fiber layer thickness map, extracted vertical tomogram, ganglion cell thickness map, and ILM-RPE thickness map. RESULTS: Trained model was able to predict progression to papilledema with a precision of 0.714 and a recall of 0.769 when trained with retinal nerve fiber layer thickness map, but not other image types. However, trained model was able to predict progression to glaucoma with a precision of 0.682 and recall of 0.857 when trained with extracted vertical tomogram, but not other image types. Area under precision-recall curve of 0.826 and 0.785 were achieved for papilledema and glaucoma models, respectively. CONCLUSIONS: Computational and analytical power of computers have become an invaluable part of our lives and research endeavors. Our proof-of-concept study showed that artificial intelligence (AI) algorithms have the potential to detect early changes on optical coherence tomography for prediction of progression that is not readily observed by clinicians. Further research may help establish possible AI models that can assist with early diagnosis or risk stratification in ophthalmology.

MALDImID: Spatialomics R package and Shiny app for more specific identification of MALDI imaging proteolytic peaks using LC-MS/MS-based proteomic biomarker discovery data.

Matrix-assisted laser desorption/ionization (MALDI) imaging of proteolytic peptides from formalin-fixed paraffin embedded (FFPE) tissue sections could be integrated in the portfolio of molecular pathologists for protein localization and tissue classification. However, protein identification can be very tedious using MALDI-time-of-flight (TOF) and post-source decay (PSD)-based fragmentation. Hereby, we implemented an R package and Shiny app to exploit liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic biomarker discovery data for more specific identification of peaks observed in bottom-up MALDI imaging data. The package is made available under the GPL 3 license. The Shiny app can directly be used at the following address: https://biosciences.shinyapps.io/Maldimid.

Ultrastructure and Surface Composition of Glutathione-Terminated Ultrasmall Silver, Gold, Platinum, and Alloyed Silver-Platinum Nanoparticles (2 nm).

Alloyed ultrasmall silver-platinum nanoparticles (molar ratio Ag:Pt = 50:50) were prepared and compared to pure silver, platinum, and gold nanoparticles, all with a metallic core diameter of 2 nm. They were surface-stabilized by a layer of glutathione (GSH). A comprehensive characterization by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential centrifugal sedimentation (DCS), and UV spectroscopy showed their size both in the dry and in the water-dispersed state (hydrodynamic diameter). Solution NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and DOSY) showed the nature of the glutathione shell including the number of GSH ligands on each nanoparticle (about 200 with a molecular footprint of 0.063 nm2 each). It furthermore showed that there are at least two different positions for the GSH ligand on the gold nanoparticle surface. Platinum strongly reduced the resolution of the NMR spectra compared to silver and gold, also in the alloyed nanoparticles. X-ray photoelectron spectroscopy (XPS) showed that silver, platinum, and silver-platinum particles were at least partially oxidized to Ag(+I) and Pt(+II), whereas the gold nanoparticles showed no sign of oxidation. Platinum and gold nanoparticles were well crystalline but twinned (fcc lattice) despite the small particle size. Silver was crystalline in electron diffraction but not in X-ray diffraction. Alloyed silver-platinum nanoparticles were almost fully amorphous by both methods, indicating a considerable internal disorder.

Adjuvant effect of mesoporous silica SBA-15 on anti-diphtheria and anti-tetanus humoral immune response.

Routine immunization against diphtheria and tetanus has drastically reduced the incidence of these diseases worldwide. Anti-diphtheria/tetanus vaccine has in general aluminum salt as adjuvant in its formulation that can produce several adverse effects. There is a growing interest in developing new adjuvants. In this study, we evaluated the efficiency of SBA-15 as an adjuvant in subcutaneous immunization in mice with diphtheria (dANA) and tetanus (tANA) anatoxins as well as with the mixture of them (dtANA). The tANA molecules and their encapsulation in SBA-15 were characterized using Small-Angle X-ray Scattering (SAXS), Dynamical Light Scattering (DLS), Nitrogen Adsorption Isotherm (NAI), Conventional Circular Dichroism (CD)/Synchrotron Radiation Circular Dichroism (SRCD) Spectroscopy, and Tryptophan Fluorescence Spectroscopy (FS). The primary and secondary antibody response elicited by subcutaneous immunization of High (HIII) and Low (LIII) antibody responder mice with dANA, tANA, or dtANA encapsulated in the SBA-15 were determined. We demonstrated that SBA-15 increases the immunogenicity of dANA and tANA antigens, especially when administered in combination. We also verified that SBA-15 modulates the antibody response of LIII mice, turning them into high antibody responder. Thus, these results suggest that SBA-15 may be an effective adjuvant for different vaccine formulations.

Staphylococcus aureus Exfoliative Toxin E, Oligomeric State and Flip of P186: Implications for Its Action Mechanism.

Staphylococcal exfoliative toxins (ETs) are glutamyl endopeptidases that specifically cleave the Glu381-Gly382 bond in the ectodomains of desmoglein 1 (Dsg1) via complex action mechanisms. To date, four ETs have been identified in different Staphylococcus aureus strains and ETE is the most recently characterized. The unusual properties of ETs have been attributed to a unique structural feature, i.e., the 180° flip of the carbonyl oxygen (O) of the nonconserved residue 192/186 (ETA/ETE numbering), not conducive to the oxyanion hole formation. We report the crystal structure of ETE determined at 1.61 Å resolution, in which P186(O) adopts two conformations displaying a 180° rotation. This finding, together with free energy calculations, supports the existence of a dynamic transition between the conformations under the tested conditions. Moreover, enzymatic assays showed no significant differences in the esterolytic efficiency of ETE and ETE/P186G, a mutant predicted to possess a functional oxyanion hole, thus downplaying the influence of the flip on the activity. Finally, we observed the formation of ETE homodimers in solution and the predicted homodimeric structure revealed the participation of a characteristic nonconserved loop in the interface and the partial occlusion of the protein active site, suggesting that monomerization is required for enzymatic activity.

Molecular insights on CALX-CBD12 interdomain dynamics from MD simulations, RDCs, and SAXS.

Na+/Ca2+ exchangers (NCXs) are secondary active transporters that couple the translocation of Na+ with the transport of Ca2+ in the opposite direction. The exchanger is an essential Ca2+ extrusion mechanism in excitable cells. It consists of a transmembrane domain and a large intracellular loop that contains two Ca2+-binding domains, CBD1 and CBD2. The two CBDs are adjacent to each other and form a two-domain Ca2+ sensor called CBD12. Binding of intracellular Ca2+ to CBD12 activates the NCX but inhibits the NCX of Drosophila, CALX. NMR spectroscopy and SAXS studies showed that CALX and NCX CBD12 constructs display significant interdomain flexibility in the apo state but assume rigid interdomain arrangements in the Ca2+-bound state. However, detailed structure information on CBD12 in the apo state is missing. Structural characterization of proteins formed by two or more domains connected by flexible linkers is notoriously challenging and requires the combination of orthogonal information from multiple sources. As an attempt to characterize the conformational ensemble of CALX-CBD12 in the apo state, we applied molecular dynamics (MD) simulations, NMR (1H-15N residual dipolar couplings), and small-angle x-ray scattering (SAXS) data in a combined strategy to select an ensemble of conformations in agreement with the experimental data. This joint approach demonstrated that CALX-CBD12 preferentially samples closed conformations, whereas the wide-open interdomain arrangement characteristic of the Ca2+-bound state is less frequently sampled. These results are consistent with the view that Ca2+ binding shifts the CBD12 conformational ensemble toward extended conformers, which could be a key step in the NCXs' allosteric regulation mechanism. This strategy, combining MD with NMR and SAXS, provides a powerful approach to select ensembles of conformations that could be applied to other flexible multidomain systems.

Typical Lung Carcinoids with Metastasis: Potential Role of MicroRNAs in the Regulation of Adaptive Immunity Associated with Disease: a Case Study.

BACKGROUND/AIMS: Lung carcinoids are uncommon neuroendocrine tumours. Molecular features of lung carcinoids have been poorly defined. microRNAs (miRNAs) are potent gene expression regulators with important roles in cancer development and progression. However, little is known on the role of miRNAs in the pathogenesis of lung carcinoids. Our goals were to identify commonly deregulated miRNAs in a rare case of lung carcinoid of typical histology with metastasis, as well as map miRNA target genes in pathways potentially associated with disease development and progression. METHODS: miRNA expression profiles were assessed using the TaqMan Low Density Arrays, which is a platform including 384 miRNAs. miRNA profiles were generated in the tumor and its corresponding lymph node metastasis, compared to reference normal lung tissues. Furthermore, miRNA expression was validated in a separate, publicly available external dataset (n=19 typical lung carcinoids; 2/19 were metastatic tumors, compared to six normal lung tissues, GSE77380). Following this analysis, computational tools were applied for data interpretation. miRTarBase was used to determine miRNA-target genes, followed by ToppGene Suite analysis to identify pathways and biological functions. In addition, the expression of genes targeted by miRNAs was validated in a second, separate external dataset (n=13 tumour samples, GSE35679). GEO2R data analysis tool was used in both validation analyses (miRNAs and genes). RESULTS: We identified 15 commonly significantly downregulated miRNAs (fold change, FC≥2 and p<0.05) in the tumour and its paired metastasis, with further decreasing levels in the metastatic lesion. Downregulation of miR-126-3p and miR-146b-5p was validated in the external dataset GSE77380. In addition, SOX2 and TCF4 genes, targeted by miR-126-3p, were consistently overexpressed in a subset of six typical lung carcinoids from the external dataset GSE35679. Pathways analysis showed that miRNAs miR-126-3p and miR-146b-5p target genes with a role in the regulation of adaptive immune response. CONCLUSION: Our results contribute to the identification of miRNA expression changes in a typical lung carcinoid and its corresponding lymph node metastasis. Down-regulated levels of miR-126-3p and miR-146b-5p and target gene over-expression could play a role in the progression of this case of primary typical lung carcinoid to regional metastasis. Identified miRNAs and target genes are potential candidates for validation in a larger number of cases.

Controlling the Surface Functionalization of Ultrasmall Gold Nanoparticles by Sequence-Defined Macromolecules.

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by 1 H NMR spectroscopy, 1 H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative 1 H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm2 per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles.

Good management practices of venomous snakes in captivity to produce biological venom-based medicines: achieving replicability and contributing to pharmaceutical industry.

One of the factors responsible for lack of reproducible findings may be attributed to the raw material used. To date, there are no apparent studies examining reproducibility using venoms for the development of new toxin-based drugs with respect to regulatory agencies' policies. For this reason, protocols were implemented to produce animal toxins with quality, traceability, and strict compliance with Good Manufacturing Practices. This required validation of the production chain from the arrival of the animal to the vivarium, followed by handling, housing, as well as compliance with respect to extraction, freeze-drying, and, finally, storage protocols, aimed at generating compounds to serve as candidate molecules applicable in clinical trials. Currently, to produce quality snake venoms to support reproductive studies, the Center for the Study of Venoms and Venomous Animals (CEVAP) from São Paulo State University (UNESP), São Paulo, Brazil has 449 microchipped snakes through rigid and standardized operating procedures for safety, health, and welfare of animals. Snakes were frequently subjected to vet clinical examination, anthelmintic, and antiparasitic treatment. Venom milk used to destroy prey was collected from each animal in individual plastic microtubes to avoid contamination and for traceability. In addition, venoms were submitted to microbiological, and biochemical toxicological analyses. It is noteworthy that investigators are responsible for caring, maintaining, and manipulating snakes and ensuring their health in captivity. This review aimed to contribute to the pharmaceutical industry the experimental experience and entire snake venom production chain required to generate quality products for therapeutic human consumption.

Graphene THz filter-switch dividers based on dipole-quadrupole and magneto-optical resonance effects.

We propose and analyze a multifunctional THz graphene-based component with graphene elements placed on a dielectric substrate. The structure of the device consists of a disc shaped resonator coupled to three graphene waveguides that excite the dipole or quadrupole resonance of surface plasmon polaritons in the resonator. The graphene resonator can be magnetized by a DC magnetic field. This device fulfills filtering of the input signal and can be used as a power divider and also as a switch. The division mechanism of the T-junction can be provided by application of a DC magnetic field or by changing the Fermi energy of the graphene resonator via an electrostatic field. Some peculiarities of the two mechanisms are discussed. Numerical simulations show that for a central frequency of 7.12 THz, devices in the OFF state have the two output ports isolated from the input port at a central frequency of about 27 dB provided by the dipole mode resonance. In the ON state and the division regime, the transmission to the output ports is around -(4÷5)dB in the 3-dB bandwidth of about 12%.

Orbital Apex Syndrome Secondary to Invasive Aspergillus Infection: A Case Series and Literature Review.

BACKGROUND: Invasive fungal sinusitis carries high morbidity and mortality and often poses a diagnostic challenge. Orbital apex syndrome (OAS) is not an uncommon presentation in the setting of invasive fungal sinusitis. Delays in diagnosis and appropriate treatment can result in permanent visual dysfunction and, potentially, death. We present 2 cases of OAS secondary to invasive sinus aspergillosis, detailing the diagnostic process, treatment, and outcome for both patients. Subsequently, we present a review of the literature and combined analysis of our 2 patients plus 71 cases from previously published reports. METHODS: Literature review was performed to identify demographic, diagnostic, clinical, and treatment data of patients with OAS caused by Aspergillus species. RESULTS: The review resulted in 52 included articles with 71 patients, plus our 2 reported patients, leading to a total of 73 subjects included in the analysis. The average age of patients at presentation was 59.9 years. A combination of visual disturbance and pain (headache and/or periocular pain) was the most common presentation reported (46 cases; 63%). Diabetes mellitus was reported in 15 cases (21%), with more than half specifically noted to have poorly controlled diabetes. After diabetes, the second most common cause of immunocompromise was chronic steroid use (n = 13; 18%). Empiric antifungal treatment was started in 10 patients (14%), while 25 patients (34%) were first treated with systemic steroids due to a concern for an inflammatory etiology. Time to diagnosis from initial presentation was on average 7.4 weeks (range of 0.3-40 weeks). Approximately 78% of the cases (57 of 73) had biopsies with histology that confirmed Aspergillus fungal morphology, and 30/73 (41%) had diagnostic fungal cultures. The majority of the cases received monotherapy with intravenous (IV) amphotericin B (36 patients; 49%) and IV voriconazole (19 patients; 26%), with a combination of the 2 or more antifungal agents being used in 11 patients (15%). Forty patients (55%) showed signs of clinical improvement with treatment, while 33 (45%) patients did not experience any improvement or continued to deteriorate, and 23 (32%) died in the course of their reported follow-up. CONCLUSIONS: The present cases illustrate well the challenge in the diagnosis and treatment of OAS due to invasive sinus aspergillosis. Our review and analysis of 73 cases support the notion that a high index of suspicion leading to early biopsy with histology and fungal culture is paramount for diagnosis. Early empiric antifungal treatment and debridement can potentially reduce morbidity and mortality.

Telemedicine Evaluations in Neuro-Ophthalmology During the COVID-19 Pandemic: Patient and Physician Surveys.

BACKGROUND: The novel coronavirus 2019 (COVID-19) pandemic has transformed health care. With the need to limit COVID-19 exposures, telemedicine has become an increasingly important format for clinical care. Compared with other fields, neuro-ophthalmology faces unique challenges, given its dependence on physical examination signs that are difficult to elicit outside the office setting. As such, it is imperative to understand both patient and provider experiences to continue to adapt the technology and tailor its application. The purpose of this study is to analyze both neuro-ophthalmology physician and patient satisfaction with virtual health visits during the time of the COVID-19 pandemic. METHODS: Across three institutions (NYU Langone Health, Indiana University Health, and Columbia University Medical Center), telemedicine surveys were administered to 159 patients. Neuro-ophthalmologists completed 157 surveys; each of these were linked to a single patient visit. Patient surveys consisted of 5 questions regarding visit preparation, satisfaction, challenges, and comfort. The physician survey included 4 questions that focused on ability to gather specific clinical information by history and examination. RESULTS: Among 159 patients, 104 (65.4%) reported that they were satisfied with the visit, and 149 (93.7%) indicated that they were comfortable asking questions. Sixty-eight (73.9%) patients found the instructions provided before the visit easy to understand. Potential areas for improvement noted by patients included more detailed preparation instructions and better technology (phone positioning, Internet connection, and software). More than 87% (137/157) of neuro-ophthalmologists surveyed reported having performed an examination that provided enough information for medical decision-making. Some areas of the neuro-ophthalmologic examination were reported to be easy to conduct (range of eye movements, visual acuity, Amsler grids, Ishihara color plates, and pupillary examination). Other components were more difficult (saccades, red desaturation, visual fields, convergence, oscillations, ocular alignment, and smooth pursuit); some were especially challenging (vestibulo-ocular reflex [VOR], VOR suppression, and optokinetic nystagmus). Clinicians noted that virtual health visits were limited by patient preparation, inability to perform certain parts of the examination (funduscopy and pupils), and technological issues. CONCLUSIONS: Among virtual neuro-ophthalmology visits evaluated, most offer patients with appointments that satisfy their needs. Most physicians in this cohort obtained adequate clinical information for decision-making. Even better technology and instructions may help improve aspects of virtual health visits.

Hydrometeorological conditions in the semiarid and east coast regions of Northeast Brazil in the 2012-2017 period.

Various studies have identified that between 2012 and 2017, Brazil's semiarid region suffered severe drought. However, few studies have analyzed whether this drought also affected the eastern coastal region of Northeast Brazil (ENEB). Therefore, the objective of this work is to identify rainfall anomalies in these regions and verify the hydrometeorological impact on reservoirs in the 2012-2017 interval. For this purpose, we used precipitation data and atmospheric variables in the period from 1981 to 2017 to investigate the rainy season and associated dynamic patterns, as well as the consequences of these mechanisms on the variation of the water parameters of important reservoirs. The results indicated that rain events in the ENEB during 2012-2017 presented similar climatological behavior, without the characteristic of a drought event as observed in the semiarid region. The meteorological analyses showed that the combination of convergence with moisture over the Atlantic Ocean possibly favored greater frequency of shallow convective rainfall in ENEB, an important factor to explain the absence of generalized negative anomalies in the region. As a consequence, the reservoirs did not suffer from water collapse, unlike in the semiarid region.

CALX-CBD1 Ca2+-Binding Cooperativity Studied by NMR Spectroscopy and ITC with Bayesian Statistics.

The Na+/Ca2+ exchanger of Drosophila melanogaster, CALX, is the main Ca2+-extrusion mechanism in olfactory sensory neurons and photoreceptor cells. Na+/Ca2+ exchangers have two Ca2+ sensor domains, CBD1 and CBD2. In contrast to the mammalian homologs, CALX is inhibited by Ca2+ binding to CALX-CBD1, whereas CALX-CBD2 does not bind Ca2+ at physiological concentrations. CALX-CBD1 consists of a ß-sandwich and displays four Ca2+-binding sites at the tip of the domain. In this study, we used NMR spectroscopy and isothermal titration calorimetry (ITC) to investigate the cooperativity of Ca2+ binding to CALX-CBD1. We observed that this domain binds Ca2+ in the slow exchange regime at the NMR chemical shift timescale. Ca2+ binding restricts the dynamics in the Ca2+-binding region. Experiments of 15N chemical exchange saturation transfer and 15N R2 dispersion allowed the determination of Ca2+ dissociation rates (∼30 s-1). NMR titration curves of residues in the Ca2+-binding region were sigmoidal because of the contribution of chemical exchange to transverse magnetization relaxation rates, R2. Hence, a novel, to our knowledge, approach to analyze NMR titration curves was proposed. Ca2+-binding cooperativity was examined assuming two different stoichiometric binding models and using a Bayesian approach for data analysis. Fittings of NMR and ITC binding curves to the Hill model yielded nHill ∼2.9, near maximal cooperativity (nHill = 4). By assuming a stepwise model to interpret the ITC data, we found that the probability of binding from 2 up to 4 Ca2+ is approximately three orders of magnitude higher than that of binding a single Ca2+. Hence, four Ca2+ ions bind almost simultaneously to CALX-CBD1. Cooperative Ca2+ binding is key to enable this exchanger to efficiently respond to changes in the intracellular Ca2+ concentration in sensory neuronal cells.

Molecular Structure and Functional Analysis of Pyocin S8 from Pseudomonas aeruginosa Reveals the Essential Requirement of a Glutamate Residue in the H-N-H Motif for DNase Activity.

Multidrug resistance (MDR) is a serious threat to public health, making the development of new antimicrobials an urgent necessity. Pyocins are protein antibiotics produced by Pseudomonas aeruginosa strains to kill closely related cells during intraspecific competition. Here, we report an in-depth biochemical, microbicidal, and structural characterization of a new S-type pyocin, named S8. Initially, we described the domain organization and secondary structure of S8. Subsequently, we observed that a recombinant S8 composed of the killing subunit in complex with the immunity (ImS8) protein killed the strain PAO1. Furthermore, mutation of a highly conserved glutamic acid to alanine (Glu100Ala) completely inhibited this antimicrobial activity. The integrity of the H-N-H motif is probably essential in the killing activity of S8, as Glu100 is a highly conserved residue of this motif. Next, we observed that S8 is a metal-dependent endonuclease, as EDTA treatment abolished its ability to cleave supercoiled pUC18 plasmid. Supplementation of apo S8 with Ni2+ strongly induced this DNase activity, whereas Mn2+ and Mg2+ exhibited moderate effects and Zn2+ was inhibitory. Additionally, S8 bound Zn2+ with a higher affinity than Ni2+ and the Glu100Ala mutation decreased the affinity of S8 for these metals, as shown by isothermal titration calorimetry (ITC). Finally, we describe the crystal structure of the Glu100Ala S8 DNase-ImS8 complex at 1.38 Å, which gave us new insights into the endonuclease activity of S8. Our results reinforce the possibility of using pyocin S8 as an alternative therapy for infections caused by MDR strains, while leaving commensal human microbiota intact.IMPORTANCE Pyocins are proteins produced by Pseudomonas aeruginosa strains that participate in intraspecific competition and host-pathogen interactions. They were first described in the 1950s and since then have gained attention as possible new antibiotics. However, there is still only scarce information about the molecular mechanisms by which these molecules induce cell death. Here, we show that the metal-dependent endonuclease activity of pyocin S8 is involved with its antimicrobial action against strain PAO1. We also describe that this killing activity is dependent on a conserved Glu residue within the H-N-H motif. The potency and selectivity of pyocin S8 toward a narrow spectrum of P. aeruginosa strains make this protein an attractive antimicrobial alternative for combatting MDR strains, while leaving commensal human microbiota intact.

Structure of and influence of a tick complement inhibitor on human complement component 5.

To provide insight into the structural and functional properties of human complement component 5 (C5), we determined its crystal structure at a resolution of 3.1 A. The core of C5 adopted a structure resembling that of C3, with the domain arrangement at the position corresponding to the C3 thioester being very well conserved. However, in contrast to C3, the convertase cleavage site in C5 was ordered and the C345C domain flexibly attached to the core of C5. Binding of the tick C5 inhibitor OmCI to C5 resulted in stabilization of the global conformation of C5 but did not block the convertase cleavage site. The structure of C5 may render possible a structure-based approach for the design of new selective complement inhibitors.

Amyloid Formation by Short Peptides in the Presence of Dipalmitoylphosphatidylcholine Membranes.

The aggregation of two short peptides, [RF] and [RF]4 (where R = arginine and F = phenylalanine), at dipalmitoylphosphatidylcholine (DPPC) model membranes was investigated at the air-water interface using the Langmuir technique and vesicles in aqueous solutions. The molar ratio of the peptide and lipid components was varied to provide insights into the peptide-membrane interactions, which might be related to their cytotoxicity. Both peptides exhibited affinity to the DPPC membrane interface and rapidly adopted ß-sheet-rich structures upon adsorption onto the surface of the zwitterionic membrane. Results from adsorption isotherm and small-angle X-ray scattering experiments showed changes in the structural and thermodynamic parameters of the membrane with increasing peptide concentration. Using atomic force microscopy, we showed the appearance of pores through the bilayer membranes and peptide aggregation at different interfaces, suggesting that the hydrophobic residues might have an effect on both pore size and layer structure, facilitating the membrane disruption and leading to different cytotoxicity effects.

Structure and Thermotropic Behavior of Bovine- and Porcine-Derived Exogenous Lung Surfactants.

Two commercial exogenous pulmonary surfactants, Curosurf and Survanta, are investigated. Their thermotropic behavior and associated structural changes for the samples in bulk are characterized and described. For Survanta, the obtained results of differential scanning calorimetry showed a thermogram with three peaks on heating and only a single peak on cooling. Curosurf on the other hand, presents calorimetric thermograms with only one peak in both the heating and cooling scans. This distinct thermotropic behavior between the two pulmonary surfactants, a consequence of their particular compositions, is associated with structural changes that were evaluated by simultaneous small- and wide-angle X-ray scattering experiments with in situ temperature variation. Interestingly, for temperatures below ∼35 °C for Curosurf and ∼53 °C for Survanta, the scattering data indicated the coexistence of two lamellar phases with different carbon chain organizations. For temperatures above these limits, the coexistence of phases disappears, giving rise to a fluid phase in both pulmonary surfactants, with multilamelar vesicles for Curosurf and unilamellar vesicles for Survanta. This process is quasi-reversible under cooling, and advanced data analysis for the scattering data indicated differences in the structural and elastic properties of the pulmonary surfactants. The detailed and systematic investigation shown in this work expands on the knowledge of the structure and thermodynamic behavior of Curosurf and Survanta, being relevant from both physiological and biophysical perspectives and also providing a basis for further studies on other types of pulmonary surfactants.

Central retinal artery occlusion occurring 30 years after successful revascularization surgery for moyamoya disease: case report.

We report a case of central retinal artery occlusion (CRAO) leading to unilateral blindness occurring in a moyamoya patient 30 years after successful pial synangiosis when she was 6 years old. Imaging studies at the time of the CRAO revealed total occlusion of the ipsilateral cervical and intracranial internal carotid artery, a vessel shown to be patent on MRI/MRA studies for decades previously. This case demonstrates that long-term follow-up of operated moyamoya patients may reveal late secondary complications, of which physicians, patients, and families need to be aware.