Oxidative protein folding in the mitochondrial intermembrane space

Disulfide bond formation is a crucial step for oxidative folding and necessary for the acquisition of a protein's native conformation. Introduction of disulfide bonds is catalyzed in specialized subcellular compartments and requires the coordinated action of specific enzymes. The intermembrane space of mitochondria has recently been found to harbor a dedicated machinery that promotes the oxidative folding of substrate proteins by shuttling disulfide bonds. The newly identified oxidative pathway consists of the redox-regulated receptor Mia40 and the sulfhydryl oxidase Erv1. Proteins destined to the intermembrane space are trapped by a disulfide relay mechanism that involves an electron cascade from the incoming substrate to Mia40, then on to Erv1, and finally to molecular oxygen via cytochrome c. This thiol–disulfide exchange mechanism is essential for the import and for maintaining the structural stability of the incoming precursors. In this review we describe the mechanistic parameters that define the interaction and oxidation of the substrate proteins in light of the recent publications in the mitochondrial oxidative folding field

Development of an intense positron source using a crystal--amorphous hybrid target for linear colliders

In a conventional positron source driven by a few GeV electron beam, a high amount of heat is loaded into a positron converter target to generate intense positrons required by linear colliders, and which would eventually damage the converter target. A hybrid target, composed of a single crystal target as a radiator of intense gamma--rays, and an amorphous converter target placed downstream of the crystal, was proposed as a scheme which could overcome the problem.This paper describes the development of an intense positron source with the hybrid target. A series of experiments on positron generation with the hybrid target has been carried out with a 8--GeV electron beam at the KEKB linac. We observed that positron yield from the hybrid target increased when the incident electron beam was aligned to the crystal axis and exceeded the one from the conventional target with the converter target of the same thickness, when its thickness is less than about 2 radiation length. The measurements in the temperature rise of the amorphous converter target was successfully carried out by use of thermocouples. These results lead to establishment to the evaluation of the hybrid target as an intense positron source.Comment: 17pages, 10figure

Tribological performance of palm kernel oil at various load using pin-on-disk tribotester / A.M.S. Zuan... [et al.]

Vegetables oil are known as an oil resources that is renewable, non-toxic and biodegradable compared to the petroleum oil. This properties brings the researcher to study on vegetable oil as a substitute resources for an application such as lubricants. In this study, the tribological properties of Palm Kernel Oil was studied by evaluating the wear and friction characteristics of aluminium (A1100) pin lubricated with different types of oils and tested using pin on disc machine in compliance with the ASTM G99 standard. The two oils used are Palm Kernel Oil and commercial semi-synthetic engine oil. The material for spherical ended pin is aluminium A1100 while material for steel disc is SKD-11. For each test, load are varied at 1 kg, 3 kg and 5 kg. The duration of each test located is 1 hour and the linear speed of the rotating disc are kept constant at 1.5 m/s. A fixed amount of 2.5 ml of lubricant is applied to the disc. From the analysis, the coefficient of friction obtained by palm kernel oil is better than semi-synthetic engine oil. However, the value of wear scar resulted from palm kernel oil is larger than semi-synthetic engine oil. Additional additives are needed to improve the wear scar of pin lubricated by Palm Kernel Oil in the future