Isolation and characterization of Candida kefyr orotidine-5′- phosphate decarboxylase (URA3) gene

Candida kefyr is a common yeast species that can be found in fermented milk and cheeses. As a first step to developing a gene transfer system for C. kefyr, the orotidine-5′-phosphate decarboxylase (URA3) gene was cloned, using degenerate PCR and genome walking. The uninterrupted open reading frame of the C. kefyr URA3 gene spans 801 bp, corresponding to 267 amino acid residues. The functionality of the gene was confirmed by complementation of ura3 auxotrophs of C. albicans and Saccharomyces cerevisiae. Phylogenetic analysis of the deduced amino acid sequence indicated that it shares a high degree of homology with other Candida URA3 homologues. The GenBank Accession No. of the C. kefyr URA3 gene is FJ914763. Copyright © 2009 John Wiley & Sons, Ltd.link_to_subscribed_fulltex

Entrapment of a Trigonopsis variabilis D-amino acid oxidase variant F54Y for oxidative deamination of cephalosporin C

Trigonopsis variabilis D-amino acid oxidase (TvDAAO) is an enzyme used in the industrial bioconversion of cephalosporin C (CPC) into 7-aminocephalosporanic acid, a crucial biosynthetic nucleus for a wide spectrum of semi-synthetic cephem antibiotics. Using homology modeling and site-directed mutagenesis, we have previously shown that the TvDAAO variant F54Y possesses improved catalytic activity and thermostability. To further explore its industrial application, the conditions for immobilization of the enzyme were examined in the present investigation. The results showed that entrapment in a calcium alginate (Ca-alginate) matrix using 2% alginate, 500mM CaCl 2, and 15min stabilization appeared to be optimal for the immobilization of F54Y. The entrapped enzyme allowed complete CPC conversion. The entrapped enzyme also showed good operational stability and retained at least 90% of its original activity after 20 reaction cycles. To conclude, the entrapment of F54Y in Ca-alginate appeared to be a simple and efficient biocatalysis system with potential application in the antibiotics industry. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.link_to_subscribed_fulltex

A single Phe54Tyr substitution improves the catalytic activity and thermostability of Trigonopsis variabilis d-amino acid oxidase

The industrial importance of Trigonopsis variabilis d-amino acid oxidase (TvDAAO) is represented by its biocatalytic oxidative deamination of cephalosporin C (CPC) to yield glutaryl-7-aminocephalosporanic acid (GL-7-ACA). The process has been incorporated into a two-step bioconversion to produce 7-aminocephalosporanic acid, the crucial synthetic nucleus for several semi-synthetic cephalosporin antibiotics. A homology model of TvDAAO indicated that residue F54 is in a close proximity to the in silico docked CPC. Substitution of this F54 to Tyr (F54Y) resulted in 6-fold improvement in k cat,app and ~2.5-fold increase in K i of GL-7-ACA. Heat treatment (55°C, 60min) did not decrease the activity of F54Y. It is suggested that the Tyr substitution might initiate hydrogen bond formation with the amino group of CPC and facilitate deamination. Faster substrate turnover, reduced GL-7-ACA inhibition and improved thermostability of the F54Y substitution render it a useful candidate in industrial production of semi-synthetic cephems. © 2009 Elsevier B.V.link_to_subscribed_fulltex

Metergoline-induced cell death in Candida krusei

Metergoline possesses potent antifungal activity against Candida krusei, a notorious yeast species that is inherently resistant to the common antifungal agents. In an attempt to elucidate the action mechanisms of metergoline, the present study was designed to investigate its effects on a number of classical markers of apoptosis in C. krusei. The results showed that transient exposure (2. h) to metergoline led to a massive intracellular accumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane potential in a concentration-dependent fashion. Analyses of the treated fungal cells after prolonged incubation (12. h) with metergoline by flow cytometry and fluorescence microscopy clearly demonstrated phosphatidylserine externalization, the presence of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling-positive cells and fungal cells undergoing necrosis. Taken together, our data provide evidence that metergoline elicited cell death process in C. krusei through elevation of the intracellular ROS level and perturbation of mitochondrial homeostasis, followed by damage of nucleus and eventual cell demise. © 2011 The British Mycological Society.link_to_subscribed_fulltextThe 2nd International Conference on Drug Discovery and Therapy (ICDDT 2010), Dubai, UAE, 1-4 February 2010. In Fungal Biology, 2011, v. 115 n. 3, p. 302-30

Is teenage obesity associated with depression and low self-esteem?: A pilot study

Objectives: A pilot study to explore the impact of perceived and actual overweight on self-esteem and depression in Hong Kong teenagers. Methods: A cross-sectional questionnaire study on 152 Chinese adolescents aged 12-16 was conducted in a secondary school in Hong Kong. Overweight was defined as a body mass index (BMI) above 90 percentile of age-adjusted BMI reference. The short form Beck Depression Inventory (BDI-13) and the Chinese version of Piers-Harris 2 Self-Concept Scale were used to measure depression and self-esteem respectively. Results: Our results showed that perceived overweight but not actual overweight female subjects had statistically significantly lower Piers-Harris score and higher depression score. Kruskal-Wallis test showed that depression was significantly more common in female teenagers who perceived themselves as being overweight but who were not actually overweight compared to those with normal BMI and body image. On the contrary, male teenagers who perceived themselves as thin were more at risk for lower Piers-Harris subscale scores. Conclusions: Our findings suggest that perceived body image has more detrimental impact on depression and self-esteem than actual body mass index in both male and female Hong Kong teenagers. This may reflect a probable influence from the mass media, advertisement, or prevailing societal values in over-promoting a slim body-image which may result in self-depreciating tendencies if female teenagers perceived themselves as being overweight. Health care professionals need to pay attention to body image perception rather than focusing solely on the physical build of teenagers.link_to_subscribed_fulltex

Purpurin inhibits biofilm development in non-albicans Candida fungi

This abstract is based on research that was funded entirely or partially by an outside source: Health and Medical Research Fund (HKSAR) 11100992 and 12111292. Seeding Funding for Basic Research (HKU) 201211159011.Poster Session 22 - P2: no. 548OBJECTIVE: To investigate the in vitro effect of purpurin on biofilm development of non-albicans Candida fungi. METHOD: Biofilms of five non-albicans Candida fungi (C. glabrata ATCC 90030, C. tropicalis ATCC 13803, C. parapsilosis ATCC 22019, C. krusei ATCC 6258, C. dubliniensis MYA-646) were prepared in pre-sterilized, polystyrene, flat-bottomed 96-well microtitre plates. Standard cell suspension (100 μL, 107 cells/mL in YNB) was transfer...link_to_OA_fulltex

ZnO nanorods for light-emitting diode applications

We investigated the influence of the growth method, growth conditions, and post-growth treatments on the ZnO nanorod properties and the performance of heterojunction light emitting diodes (LEDs) based on ZnO nanorods. Due to small lattice mismatch between GaN and ZnO, we will mainly consider p-GaN/n-ZnO nanorod heterojunctions. The influence of p-GaN substrate and the influence of growth method and growth conditions used for ZnO nanorods on the LED performance will be discussed. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).link_to_subscribed_fulltex

Blending community service and teaching to open vision care and eye health awareness to university students

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