Reduction of Friction Using Microabrasive Air Jet Machining.

In this paper, we introduce a microabrasive air jet (micro-AAJ) machining system and describe machining results obtained while using it. Our research activities have focused on the development of micro-AAJ machining methods for friction reduction without requiring a mask. Through this study, we want to show that such processing is possible without a mask when using the AAJ method. In this paper, a micro-AAJ machining system is introduced, and the processing results are described. By comparing the friction coefficient of texturing under various conditions, the relative relationship between the surface shape and the friction coefficient can be identified. We investigated the effect of the relationship between rotating velocity, traverse speed, density of the patterned area and injection pressure on friction. The friction is decreased with a low traverse speed and high-density patterned area under high-speed driving conditions, as verified by experiments using a friction test system.

Rat liver 10-formyltetrahydrofolate dehydrogenase, carbamoyl phosphate synthetase 1 and betaine homocysteine S-methytransferase were co-purified on Kunitz-type soybean trypsin inhibitor-coupled sepharose CL-4B.

An Asp/His catalytic site of 10-formyltetrahydrofolate dehydrogenase (FDH) was suggested to have a similar catalytic topology with the Asp/His catalytic site of serine proteases. Many studies supported the hypothesis that serine protease inhibitors can bind and modulate the activity of serine proteases by binding to the catalytic site of serine proteases. To explore the possibility that soybean trypsin inhibitor (SBTI) can recognize catalytic sites of FDH and can make a stable complex, we carried out an SBTI-affinity column by using rat liver homogenate. Surprisingly, the Rat FDH molecule with two typical liver proteins, carbamoyl-phosphate synthetase 1 (CPS1) and betaine homocysteine S-methyltransferase (BHMT) were co-purified to homogeneity on SBTI-coupled Sepharose and Sephacryl S-200 followed by Superdex 200 FPLC columns. These three liver-specific proteins make a protein complex with 300 kDa molecular mass on the gel-filtration column chromatography in vitro. Immuno-precipitation experiments by using anti-FDH and anti-SBTI antibodies also supported the fact that FDH binds to SBTI in vitro and in vivo. These results demonstrate that the catalytic site of rat FDH has a similar structure with those of serine proteases. Also, the SBTI-affinity column will be useful for the purification of rat liver proteins such as FDH, CPS1 and BHMT.

Analytical method validation and monitoring of diacetyl in liquors from Korean market.

Diacetyl is a natural fermentation by-product and is an important flavor component of certain liquors. This paper aims to validate the high performance liquid chromatography (HPLC) method based on derivatization with 1,2-diaminobenzene for diacetyl quantification in liquor samples. A limit of quantitation of 0.039 mg/L was obtained. Coefficient regression (R2) of calibration curve for the HPLC-UV method exceeded 0.999, showing adequate linearity on the standard curve. Relative standard deviation values obtained from intraday and interday analysis for precision were 2.5 and 4.1%, respectively. Using the validated method, the contents of diacetyl in liquors (12 types, 389 samples) distributed throughout Korea were monitored. The average diacetyl content of all analyzed liquor samples ranged from trace amounts to 3.655 mg/L (microbrewery beer). The highest average diacetyl content was found in fruit wines (0.432 mg/L), followed by red wine (0.320 mg/L) and general distilled spirits (0.249 mg/L). In takju and yakju, no distinctive effect of sterilization on diacetyl content was found.

Photocurable, solventless, solution-processable, silica-nanoparticle-dispersed acryl hybrid materials.

Solventless silica-acryl hybrid materials composed of organically modified silica nanoparticles and acryl monomers were fabricated using a simple sol-gel process and solvent evaporation. The homogeneously dispersed silica-acryl hybrid materials can be formed into films through a simple solution-coating process and UV curing. The silica-acryl hybrid materials exhibited good photocurability with -90% conversion upon UV exposure and a high transmittance of above 95% in the visible wavelength region regardless of the silica nanoparticle content. In particular, the silica-acryl hybrid materials exhibited increased mechanical hardness and thermal stability directly proportional to the content of silica nanoparticles and exhibited a good surface roughness of -1 nm. Therefore, these silica-acryl hybrid materials are good candidates for coating applications in electronic, electro-optic, and energy devices.

A three-step proteolytic cascade mediates the activation of the peptidoglycan-induced toll pathway in an insect.

The recognition of lysine-type peptidoglycans (PG) by the PG recognition complex has been suggested to cause activation of the serine protease cascade leading to the processing of Spätzle and subsequent activation of the Toll signaling pathway. So far, two serine proteases involved in the lysine-type PG Toll signaling pathway have been identified. One is a modular serine protease functioning as an initial enzyme to be recruited into the lysine-type PG recognition complex. The other is the Drosophila Spätzle processing enzyme (SPE), a terminal enzyme that converts Spätzle pro-protein to its processed form capable of binding to the Toll receptor. However, it remains unclear how the initial PG recognition signal is transferred to Spätzle resulting in Toll pathway activation. Also, the biochemical characteristics and mechanism of action of a serine protease linking the modular serine protease and SPE have not been investigated. Here, we purified and cloned a novel upstream serine protease of SPE that we named SAE, SPE-activating enzyme, from the hemolymph of a large beetle, Tenebrio molitor larvae. This enzyme was activated by Tenebrio modular serine protease and in turn activated the Tenebrio SPE. The biochemical ordered functions of these three serine proteases were determined in vitro, suggesting that the activation of a three-step proteolytic cascade is necessary and sufficient for lysine-type PG recognition signaling. The processed Spätzle by this cascade induced antibacterial activity in vivo. These results demonstrate that the three-step proteolytic cascade linking the PG recognition complex and Spätzle processing is essential for the PG-dependent Toll signaling pathway.

Mannose-binding lectin without the aid of its associated serine proteases alters lipopolysaccharide-mediated cytokine/chemokine secretion from human endothelial cells.

Coupling between certain pathogen-associated molecular patterns and corresponding pattern recognition receptors of endothelial cells is important for the mediation of vascular inflammatory responses. Mannose-binding lectin (MBL) recognizes certain carbohydrate structures of microbes and subsequently activates the complement system as well as facilitates the phagocytosis of targets. We investigated whether MBL can intervene in the interaction between bacterial lipopolysaccharide (LPS) and endothelial cells to modulate subsequent inflammatory responses. In response to LPS, human umbilical vein endothelial cells (HUVEC) produced various cytokines/chemokines. Addition of the purified human MBL/MBL-associated serine proteases (MASP) complex or recombinant human MBL enhanced LPS-mediated cytokine/chemokine secretion by HUVEC, including interleukin-8 (IL-8), IL-6 and monocyte chemoattractant protein-1 in a dose-dependent manner. This enhancing effect was ameliorated by the addition of anti-MBL antibody or mannan. Among the cytokines/chemokines we analysed, IL-6 showed the greatest increase of secretion in the presence of native MBL/MASP complex or recombinant MBL. MBL, regardless of its association with MASP, alters LPS-mediated cytokine/chemokine secretion of HUVEC. Besides the well-known functions of MBL, to activate the lectin-complement pathway and to facilitate clearance of targets, alteration of cytokine/chemokine secretion may provide an additional role for MBL in modulating vascular inflammation.

Clustering of peptidoglycan recognition protein-SA is required for sensing lysine-type peptidoglycan in insects.

Recognition of lysine-type peptidoglycan by peptidoglycan recognition protein (PGRP)-SA provokes the activation of the Toll and prophenoloxidase pathways. Here we reveal that a soluble fragment of lysine-type peptidoglycan, a long glycan chain with short stem peptides, is a potent activator of the Drosophila Toll pathway and the prophenoloxidase activation cascade in the beetle Tenebrio molitor. Using this peptidoglycan fragment, we present biochemical evidence that clustering of PGRP-SA molecules on the peptidoglycan is required for the activation of the prophenoloxidase cascade. We subsequently highlight that the lysozyme-mediated partial digestion of highly cross-linked lysine-type peptidoglycan dramatically increases the binding of PGRP-SA, presumably by inducing clustering of PGRP-SA, which then recruits the Gram-negative bacteria-binding protein 1 homologue and a modular serine protease containing low-density lipoprotein and complement control protein domains. The crucial role of lysozyme in the prophenoloxidase activation cascade is further confirmed in vivo by using a lysozyme inhibitor. Taken together, we propose a model whereby lysozyme presents a processed form of lysine-type peptidoglycan for clustering of PGRP-SA that recruits Gram-negative bacteria-binding protein 1 and the modular serine protease, which leads to the activation of both the Toll and prophenoloxidase pathways.