Structural basis for binding and transfer of heme in bacterial heme-acquisition systems.

Periplasmic heme-binding proteins (PBPs) in Gram-negative bacteria are components of the heme acquisition system. These proteins shuttle heme across the periplasmic space from outer membrane receptors to ATP-binding cassette (ABC) heme importers located in the inner-membrane. In the present study, we characterized the structures of PBPs found in the pathogen Burkholderia cenocepacia (BhuT) and in the thermophile Roseiflexus sp. RS-1 (RhuT) in the heme-free and heme-bound forms. The conserved motif, in which a well-conserved Tyr interacts with the nearby Arg coordinates on heme iron, was observed in both PBPs. The heme was recognized by its surroundings in a variety of manners including hydrophobic interactions and hydrogen bonds, which was confirmed by isothermal titration calorimetry. Furthermore, this study of 3 forms of BhuT allowed the first structural comparison and showed that the heme-binding cleft of BhuT adopts an "open" state in the heme-free and 2-heme-bound forms, and a "closed" state in the one-heme-bound form with unique conformational changes. Such a conformational change might adjust the interaction of the heme(s) with the residues in PBP and facilitate the transfer of the heme into the translocation channel of the importer.

Highly efficient blue electroluminescence based on thermally activated delayed fluorescence.

Organic compounds that exhibit highly efficient, stable blue emission are required to realize inexpensive organic light-emitting diodes for future displays and lighting applications. Here, we define the design rules for increasing the electroluminescence efficiency of blue-emitting organic molecules that exhibit thermally activated delayed fluorescence. We show that a large delocalization of the highest occupied molecular orbital and lowest unoccupied molecular orbital in these charge-transfer compounds enhances the rate of radiative decay considerably by inducing a large oscillator strength even when there is a small overlap between the two wavefunctions. A compound based on our design principles exhibited a high rate of fluorescence decay and efficient up-conversion of triplet excitons into singlet excited states, leading to both photoluminescence and internal electroluminescence quantum yields of nearly 100%.

Designing receptor agonists with enhanced pharmacokinetics by grafting macrocyclic peptides into fragment crystallizable regions.

Short half-lives in circulation and poor transport across the blood-brain barrier limit the utility of cytokines and growth factors acting as receptor agonists. Here we show that surrogate receptor agonists with longer half-lives in circulation and enhanced transport rates across the blood-brain barrier can be generated by genetically inserting macrocyclic peptide pharmacophores into the structural loops of the fragment crystallizable (Fc) region of a human immunoglobulin. We used such 'lasso-grafting' approach, which preserves the expression levels of the Fc region and its affinity for the neonatal Fc receptor, to generate Fc-based protein scaffolds with macrocyclic peptides binding to the receptor tyrosine protein kinase Met. The Met agonists dimerized Met, inducing biological responses that were similar to those induced by its natural ligand. Moreover, lasso-grafting of the Fc region of the mouse anti-transferrin-receptor antibody with Met-binding macrocyclic peptides enhanced the accumulation of the resulting Met agonists in brain parenchyma in mice. Lasso-grafting may allow for designer protein therapeutics with enhanced stability and pharmacokinetics.

A convenient method to estimate the glass transition temperature of small organic semiconductor materials.

For a long period of time, while the glass transition temperature (Tg) had been mainly focused on in polymer science, the Tg values of small organic materials have been recognized to be important not only in medicines but also in a wide variety of organic optoelectronics in recent years. In this study, we report a useful and convenient "melt-blending" method to estimate organic semiconductor materials' Tg values, which are hard to observe when each material exists independently. We revealed that some cases reported incorrect Tg values.

De novo Fc-based receptor dimerizers differentially modulate PlexinB1 function.

Signaling by single-pass transmembrane receptors often involves a formation of ligand-induced receptor dimers with particular conformation, and bivalent receptor binders can modulate receptor functions by inducing different receptor dimer conformations, although such agents are difficult to design. Here, we describe the generation of both antagonistic and agonistic receptor dimerizers toward PlexinB1 (PlxnB1), a receptor for semaphorin 4D (Sema4D), by grafting two different PlxnB1-binding peptides onto the human immunoglobulin G1 (IgG1) Fc protein. The function-modulating activity of a peptide Fc was strongly dependent on the type of the peptide as well as the grafting site, with the best variants showing activity at an nM concentration range. Structural analysis of each peptide-PlxnB1 complex revealed that the agonistic Fc dimerizes PlxnB1 in a face-to-face fashion similar to that induced by Sema4D, whereas antagonistic Fc would induce signaling-incompetent PlxnB1 dimer conformation, enforcing the idea that plexin activation is primarily controlled by the receptor orientation within the dimer.

Lasso-grafting of macrocyclic peptide pharmacophores yields multi-functional proteins.

Protein engineering has great potential for devising multifunctional recombinant proteins to serve as next-generation protein therapeutics, but it often requires drastic modifications of the parental protein scaffolds e.g., additional domains at the N/C-terminus or replacement of a domain by another. A discovery platform system, called RaPID (Random non-standard Peptides Integrated Discovery) system, has enabled rapid discovery of small de novo macrocyclic peptides that bind a target protein with high binding specificity and affinity. Capitalizing on the optimized binding properties of the RaPID-derived peptides, here we show that RaPID-derived pharmacophore sequences can be readily implanted into surface-exposed loops on recombinant proteins and maintain both the parental peptide binding function(s) and the host protein function. We refer to this protein engineering method as lasso-grafting and demonstrate that it can endow specific binding capacity toward various receptors into a diverse set of scaffolds that includes IgG, serum albumin, and even capsid proteins of adeno-associated virus, enabling us to rapidly formulate and produce bi-, tri-, and even tetra-specific binder molecules.

＜Editors' Choice＞ Efficacy of pectoral nerve block type-2 (Pecs II block) versus serratus plane block for postoperative analgesia in breast cancer surgery: a retrospective study.

Thoracic wall nerve blocks reduce postoperative acute pain after breast cancer surgery (BCS); however, their short-term effects and the most effective technique remain unclear. To compare the effects of pectoral nerve block type-2 (Pecs II block) and serratus plane block for postoperative short-term analgesia, we retrospectively reviewed 43 BCS patients who underwent Pecs II block (n=22) or serratus plane block (n=21). The primary outcome was the proportion of patients with no complaints of pain 2 months post-BCS. The odds ratio (OR) was assessed, adjusting for axillary lymph node dissection. The secondary outcomes were pain severity 24 hours and 2 months post-operation using the numerical rating scale score, and morphine consumption within 24 hours. The proportion of patients without pain 2 months post-BCS was significantly less with Pecs II block than in patients with serratus plane block (55% vs. 19%, adjusted OR, 5.04; 95% confidence interval, 1.26-20.07; P=0.02); the median [interquartile range] score for pain 2 months post-operation was also significantly lower with Pecs II block (Pecs II block 0.5 [0-1] vs. serratus plane block 1 [1-2]); P=0.03). Regarding post-BCS acute analgesia, the median [interquartile range] postoperative 24-hour pain score was 2 [1-3] and 3 [1.5-3.5], and the median morphine consumption within 24 hours was 1.5 [0.75-5.5] and 3 [1.5-10] mg in Pecs II block and serratus plane block (P=0.47 and P=0.11), respectively. This study suggests that Pecs II block prevents short-term post-BCS pain better than serratus plane block. However, further studies are needed in order to support this finding.

Proposal of auxiliary diagnosis index for autism spectrum disorder using near-infrared spectroscopy.

Lack of a diagnostic index is a problem that needs to be overcome in the diagnosis of autism spectrum disorder (ASD), because this problem prevents an objective assessment based on biomarkers. This paper describes the development of a diagnostic index for ASD using near-infrared spectroscopy (NIRS). We investigated continuous prefrontal hemodynamic changes depending on reciprocal disposition of working memory and nonworking memory tasks using two-channel NIRS. NIRS signals in the prefrontal cortex were compared between high-functioning ASD subjects ([Formula: see text]) and typically developed (TD) subjects ([Formula: see text]). The brain activities of the TD subjects were related to experimental design. These results were not confirmed in brain activities of ASD subjects, although the task performance rate was almost equivalent. The brain activities of TD subjects and ASD subjects were evaluated using a weighted separability (WS) index obtained from the feature phase of oxy-hemoglobin and its differential value. Calculation of the [Formula: see text]-test (TD subject versus ASD subject) confirmed that WS was significant. This result showed that the proposed index was useful for evaluation of the brain activity of ASD subjects.

Crystal structure of bacterial haem importer complex in the inward-facing conformation.

Pathogenic bacteria remove iron from the haem of host tissues and use it as a catalytic center of many enzymes. Haem uptake by pathogenic bacteria is facilitated by the membrane-integrated haem importer, which belongs to the type II ATP-binding cassette (ABC) transporter. Here we present crystal structures of Burkholderia cenocepacia haem importer BhuUV complexed with the periplasmic haem-binding protein BhuT and in the absence of BhuT. The transmembrane helices of these structures show an inward-facing conformation, in which the cytoplasmic gate of the haem translocation pathway is completely open. Since this conformation is found in both the haem- and nucleotide-free form, the structure of BhuUV-T provides the post-translocation state and the missing piece in the transport cycle of the type II importer. Structural comparison with the outward-facing conformation reported for the haem importer ortholog HmuUV from Yersenia pestis gives mechanistic insights into conformational transitions and haem secretion during the haem transport cycle.

Zinc complexes exhibiting highly efficient thermally activated delayed fluorescence and their application to organic light-emitting diodes.

Metal complexes emitting thermally activated delayed fluorescence based on intra-ligand charge transfer and enhanced by metallization were synthesized. Organic light-emitting diodes using a thermally stable zinc complex processed by vacuum vapor deposition achieved an external quantum efficiency of nearly 20%.

Paprika Pigments Attenuate Obesity-Induced Inflammation in 3T3-L1 Adipocytes.

Obesity is related to various diseases, such as diabetes, hyperlipidemia, and hypertension. Adipocytokine, which is released from adipocyte cells, affects insulin resistance and blood lipid level disorders. Further, adipocytokine is related to chronic inflammation in obesity condition adipocyte cells. Paprika pigments (PPs) contain large amounts of capsanthin and capsorubin. These carotenoids affect the liver and improve lipid disorders of the blood. However, how these carotenoids affect adipocyte cells remains unknown. Present study examined the effects of PP on adipocytokine secretion, which is related to improvement of metabolic syndrome. In addition, suppressive effects of PP on chronic inflammation in adipocyte cells were analyzed using 3T3-L1 adipocyte cells and macrophage cell coculture experiments. PP promoted 3T3-L1 adipocyte cells differentiation upregulated adiponectin mRNA expression and secretion. Further, coculture of adipocyte and macrophage cells treated with PP showed suppressed interleukin-6 (IL-6), tumor necrosis factor- α (TNF- α ), monocyte chemotactic protein-1 (MCP-1), and resistin mRNA expression, similarly to treatment with troglitazone, which is a PPAR γ ligand medicine. Conclusion. These results suggest that PP ameliorates chronic inflammation in adipocytes caused by obesity. PP adjusts adipocytokine secretion and might, therefore, affect antimetabolic syndrome diseases.

Modulation of polymer refractive indices with diamond nanoparticles for metal-free multilayer film mirrors.

Modulation of the refractive index of a polymer was achieved by combining it with diamond nanoparticles (NDs). The increase in the refractive index was controlled by the amount of NDs added, according to the Lorentz-Lorenz equation. The refractive index of poly(vinyl alcohol) (PVA), which was used as the base polymer, increased from 1.52 to 1.88. A multilayer film consisting of alternating layers of ND-PVA composite and poly(methyl methacrylate) exhibited ca. 80% reflectance with 10 bilayers.