Publications by authors named "Yung-Han Chen"

Monitoring the healing progress of diabetic foot ulcers is a challenging process. Accurate segmentation of foot ulcers can help podiatrists to quantitatively measure the size of wound regions to assist prediction of healing status. The main challenge in this field is the lack of publicly available manual delineation, which can be time consuming and laborious.

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This research investigated real-time fingertip detection in frames captured from the increasingly popular wearable device, smart glasses. The egocentric-view fingertip detection and character recognition can be used to create a novel way of inputting texts. We first employed Unity3D to build a synthetic dataset with pointing gestures from the first-person perspective.

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Prion diseases are transmissible fatal neurodegenerative disorders affecting humans and other mammals. The disease transmission can occur between different species but is limited by the sequence homology between host and inoculum. The crucial molecular event in the progression of this disease is prion formation, starting from the conformational conversion of the normal, membrane-anchored prion protein (PrP) into the misfolded, β-sheet-rich and aggregation-prone isoform (PrP), which then self-associates into the infectious amyloid form called prion.

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Lysine 5,6-aminomutase (5,6-LAM) and ornithine 4,5-aminomutase (4,5-OAM) are two of the rare enzymes that use assistance of two vitamins as cofactors. These enzymes employ radical generating capability of coenzyme B12 (5'-deoxyadenosylcobalamin, dAdoCbl) and ability of pyridoxal-5'-phosphate (PLP, vitamin B6) to stabilize high-energy intermediates for performing challenging 1,2-amino rearrangements between adjacent carbons. A large-scale domain movement is required for interconversion between the catalytically inactive open form and the catalytically active closed form.

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Iron is essential for pathogen survival, virulence, and colonization. Feo is suggested to function as the ferrous iron (Fe(2+)) transporter. The enterobacterial Feo system is composed of 3 proteins: FeoB is the indispensable component and is a large membrane protein likely to function as a permease; FeoA is a small Src homology 3 (SH3) domain protein that interacts with FeoB; FeoC is a winged-helix protein containing 4 conserved Cys residues in a sequence suitable for harboring a putative iron-sulfur (Fe-S) cluster.

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We performed spectroscopic and functional characterization on cyanobacterium Synechocystis PCC6803 with mutations of charged residues of the cytoplasmic side of cytochrome (Cyt) b559 in photosystem II (PSII). All of the mutant cells grew photoautotrophically and assembled stable PSII. However, R7Eα, R17Eα and R17Lβ mutant cells grew significantly slower and were more susceptible to photoinhibition than wild-type cells.

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Article Synopsis
  • The crystal structure of lysine 5,6-aminomutase shows it can exist in an "open" state, but must transition to a "closed" state for effective catalysis involving cofactors and substrates.
  • Studies with various D-lysine analogues demonstrate that these compounds bind to the enzyme and facilitate the necessary chemical reactions, suggesting the presence of a closed state even though a crystal structure of it is not yet available.
  • Spectroscopic evidence reveals that these analogues can influence the enzyme to switch between open and closed forms, highlighting the complexity of the catalytic process for lysine turnover.
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Adenosylcobalamin- and pyridoxal-5'-phosphate-dependent lysine 5,6-aminomutase utilizes free radical intermediates to mediate 1,2-amino group rearrangement, during which an elusive high-energy aziridincarbinyl radical is proposed to be central in the mechanism of action. Understanding how the enzyme participates in stabilizing any of the radical intermediates is fundamentally significant. Y263F mutation abolished the enzymatic activity.

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The assimilatory nitrate reductase (NarB) of N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801 is a monomeric enzyme with dual affinity for substrate nitrate. We purified the recombinant NarB of Cyanothece sp.

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The neurotoxicity of Aβ is associated with the formation of free radical by interacting with redox active metals such as Cu(2+). However, the relationship between ion-interaction, ion-driven free radical formation, and Aβ conformation remains to be further elucidated. In the present study, we investigated the correlation of Cu(2+) interaction and Cu(2+)-driven free radical formation with Aβ40 conformation.

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The functional role of cytochrome (cyt) b(559) in photosystem II (PSII) was investigated in H22K alpha and Y18S alpha cyt b(559) mutants of the cyanobacterium Synechocystis sp. PCC6803. H22K alpha and Y18S alpha cyt b(559) mutant carries one amino acid substitution on and near one of heme axial ligands of cyt b(559) in PSII, respectively.

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We demonstrate that the steady state reaction of lysine 5,6-aminomutase with substrate analogue 4-thia-l-lysine generates a radical intermediate, which accumulates in the enzyme to an electron paramagnetic resonance (EPR) detectable level. EPR line width narrowing of approximately 1 mT due to [4'-(2)H] labeling of the pyridoxal-5'-phosphate (PLP), an isotropic hyperfine coupling of 40 MHz for the proton at C4' of PLP derived from (2)H electron nuclear double resonance (ENDOR) measurement, and spin density delocalization onto the (31)P of PLP realized from observations of the (31)P ENDOR signal provide unequivocal identification of the radical as a substrate-PLP-based species. X- and Q-band EPR spectra fittings demonstrate that this radical is spin coupled with the low spin Co(2+) in cob (II) alamin and the distance between the two species is about 10 A.

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We identified a spontaneously generated mutant from Synechocystis sp. PCC6803 wild-type cells grown in BG-11 agar plates containing 5 mM Glu and 10 microM DCMU. This mutant carries an R7L mutation on the alpha-subunit of cyt b559 in photosystem II (PSII).

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