1,946 research outputs found
Histidine 454 plays an important role in polymerization of human glutamate dehydrogenase
AbstractAlthough previous chemical modification studies have suggested several residues to be involved in the maintenance of the quaternary structure of glutamate dehydrogenase (GDH), there are conflicting views for the polymerization process and no clear evidence has been reported yet. In the present study, cassette mutagenesis at seven putative positions (Lys333, Lys337, Lys344, Lys346, Ser445, Gly446, and His454) was performed using a synthetic human GDH gene to examine the polymerization process. Of the mutations at the seven different sites, only the mutagenesis at His454 results in depolymerization of the hexameric GDH into active trimers as determined by HPLC gel filtration analysis and native gradient polyacrylamide gel electrophoresis. The mutagenesis at His454 has no effects on expression or stability of the protein. The KM values for NADH and 2-oxoglutarate were 1.5-fold and 2.5-fold greater, respectively, for the mutant GDH than for wild-type GDH, indicating that substitution at position 454 had appreciable effects on the affinity of the enzyme for both NADH and 2-oxoglutarate. The Vmax values were similar for wild-type and mutant GDH. The kcat/KM value of the mutant GDH was reduced up to 2.8-fold. The decreased efficiency of the mutant, therefore, results from the increase in KM values for NADH and 2-oxoglutarate. The results with cassette mutagenesis and HPLC gel filtration analysis suggest that His454 is involved in the polymerization process of human GDH
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Elevated cellular cholesterol in Familial Alzheimerās presenilin 1 mutation is associated with lipid raft localization of Ī²-amyloid precursor protein
Familial Alzheimerās disease (FAD)-associated presenilin 1 (PS1) serves as a catalytic subunit of Ī³-secretase complex, which mediates the proteolytic liberation of Ī²-amyloid (AĪ²) from Ī²-amyloid precursor protein (APP). In addition to its proteolytic role, PS1 is involved in non-proteolytic functions such as protein trafficking and ion channel regulation. Furthermore, postmortem AD brains as well as AD patients showed dysregulation of cholesterol metabolism. Since cholesterol has been implicated in regulating AĪ² production, we investigated whether the FAD PS1-associated cholesterol elevation could influence APP processing. We found that in CHO cells stably expressing FAD-associated PS1 ĪE9, total cholesterol levels are elevated compared to cells expressing wild-type PS1. We also found that localization of APP in cholesterol-enriched lipid rafts is substantially increased in the mutant cells. Reducing the cholesterol levels by either methyl-Ī²-cyclodextrin or an inhibitor of CYP51, an enzyme mediating the elevated cholesterol in PS1 ĪE9-expressing cells, significantly reduced lipid raft-associated APP. In contrast, exogenous cholesterol increased lipid raft-associated APP. These data suggest that in the FAD PS1 ĪE9 cells, the elevated cellular cholesterol level contributes to the altered APP processing by increasing APP localized in lipid rafts
Analysis of Problems in Cut Slope Survey and Design Based on Case Studies
In construction of roads or large residential complexes, the formation of large scale cut slopes is inevitable due to the large proportion of mountains in Korea. The problems involving the slope stability has emerged as a major concern. Inaccurate subsurface exploration can result in slope failure during or after the construction, thereby increasing the construction cost and delaying the construction duration. This study reviews problems involving the cut slope survey methods, design criteria, and examining the collapse mechanisms through various case studies. This study suggests the optimum survey methods and design criteria based on the possible failure mechanisms
Small intestinal model for electrically propelled capsule endoscopy
The aim of this research is to propose a small intestine model for electrically propelled capsule endoscopy. The electrical stimulus can cause contraction of the small intestine and propel the capsule along the lumen. The proposed model considered the drag and friction from the small intestine using a thin walled model and Stokes' drag equation. Further, contraction force from the small intestine was modeled by using regression analysis. From the proposed model, the acceleration and velocity of various exterior shapes of capsule were calculated, and two exterior shapes of capsules were proposed based on the internal volume of the capsules. The proposed capsules were fabricated and animal experiments were conducted. One of the proposed capsules showed an average (SD) velocity in forward direction of 2.91 Ā± 0.99 mm/s and 2.23 Ā± 0.78 mm/s in the backward direction, which was 5.2 times faster than that obtained in previous research. The proposed model can predict locomotion of the capsule based on various exterior shapes of the capsule
Asymptomatic Tubular Duplication of the Transverse Colon in an Adult
Colonic duplication is a rare congenital anomaly of the alimentary tract. In most cases, symptomatic duplications of the colon are recognized and treated by childhood. It is uncommon for these lesions to be detected in the adulthood since they present with vague symptoms if at all. We experienced a case of asymptomatic tubular duplication of the transverse colon in a 40-year-old female. Barium enema revealed a tubular duplication of the transverse colon. The duplicated segment arose from the mid ascending colon and incorporated just proximal to the splenic flexure, running parallel to the transverse colon and communicating with it at both ends. Colonoscopy demonstrated a normal colonic mucosa in the duplicated segment. The diameter of its lumen gradually narrowed proximally and the colonoscope could not be passed through the proximal opening of the segment. The patient did not need any treatment. Duplications of the alimentary tract can be found at any age. The possibility of congenital lesions in the adult population should not be overlooked
Boundary integral equation method for resonances in gradient index cavities designed by conformal transformation optics
In the case of two-dimensional gradient index cavities designed by the
conformal transformation optics, we propose a boundary integral equation method
for the calculation of resonant mode functions by employing a fictitious space
which is reciprocally equivalent to the physical space. Using the Green's
function of the interior region of the uniform index cavity in the fictitious
space, resonant mode functions and their far-field distributions in the
physical space can be obtained. As a verification, resonant modes in
lima\c{c}on-shaped transformation cavities were calculated and mode patterns
and far-field intensity distributions were compared with those of the same
modes obtained from the finite element method.Comment: 13 pages, 6 figure
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