Oi Wah Liew

Binding interaction of quercetin -3 -β -galactoside and its synthetic derivatives with SARS-CoV 3CLpro : Structure-activity relationship studies reveal salient pharmacophore features

Abstract The 3C-like protease (3CLpro) of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is one of the most promising targets for discovery of drugs against SARS, because of its critical role in the viral life cycle. In this study, a natural compound called quercetin-3-β-galactoside was identified as an inhibitor of the protease by molecular docking, SPR/FRET-based bioassays, and mutagenesis studies. Both molecular modeling and Q189A mutation revealed that Gln189 plays a key role in the binding. Furthermore, experimental evidence showed that the secondary structure and enzymatic activity of SARS-CoV 3CLpro were not affected by the Q189A mutation. With the help of molecular modeling, eight new derivatives of the natural product were designed and synthesized. Bioassay results reveal salient features of the structure–activity relationship of the new compounds: (1) removal of the 7-hydroxy group of the quercetin moiety decreases the bioactivity of the derivatives; (2) acetoxylation of the sugar moiety abolishes inhibitor action; (3) introduction of a large sugar substituent on 7-hydroxy of quercetin can be tolerated; (4) replacement of the galactose moiety with other sugars does not affect inhibitor potency. This study not only reveals a new class of compounds as potential drug leads against the SARS virus, but also provides a solid understanding of the mechanism of inhibition against the target enzyme.

Signature Optical Cues: Emerging Technologies for Monitoring Plant Health.

Optical technologies can be developed as practical tools for monitoring plant health by providing unique spectral signatures that can be related to specific plant stresses. Signatures from thermal and fluorescence imaging have been used successfully to track pathogen invasion before visual symptoms are observed. Another approach for non-invasive plant health monitoring involves elucidating the manner with which light interacts with the plant leaf and being able to identify changes in spectral characteristics in response to specific stresses. To achieve this, an important step is to understand the biochemical and anatomical features governing leaf reflectance, transmission and absorption. Many studies have opened up possibilities that subtle changes in leaf reflectance spectra can be analyzed in a plethora of ways for discriminating nutrient and water stress, but with limited success. There has also been interest in developing transgenic phytosensors to elucidate plant status in relation to environmental conditions. This approach involves unambiguous signal creation whereby genetic modification to generate reporter plants has resulted in distinct optical signals emitted in response to specific stressors. Most of these studies are limited to laboratory or controlled greenhouse environments at leaf level. The practical translation of spectral cues for application under field conditions at canopy and regional levels by remote aerial sensing remains a challenge. The movement towards technology development is well exemplified by the Controlled Ecological Life Support System under development by NASA which brings together technologies for monitoring plant status concomitantly with instrumentation for environmental monitoring and feedback control.

Discovery of novel small molecule inhibitors of dengue viral NS2B-NS3 protease using virtual screening and scaffold hopping.

By virtual screening, compound 1 was found to be active against NS2B-NS3 protease (IC(50) = 13.12 ± 1.03 μM). Fourteen derivatives (22) of compound 1 were synthesized, leading to the discovery of four new inhibitors with biological activity. In order to expand the chemical diversity of the inhibitors, small-molecule-based scaffold hopping was performed on the basis of the common scaffold of compounds 1 and 22. Twenty-one new compounds (23, 24) containing quinoline (new scaffold) were designed and synthesized. Protease inhibition assays revealed that 12 compounds with the new scaffold are inhibitors of NS2B-NS3 protease. Taken together, 17 new compounds were discovered as NS2B-NS3 protease inhibitors with IC(50) values of 7.46 ± 1.15 to 48.59 ± 3.46 μM, and 8 compounds belonging to two different scaffolds are active to some extent against DENV based on luciferase reporter replicon-based assays. These novel chemical entities could serve as lead structures for discovering therapies against DENV.

Growth differentiation factor 15 in heart failure with preserved vs. reduced ejection fraction.

Growth differentiation factor 15 (GDF15) is a cytokine highly expressed in states of inflammatory stress. We aimed to study the clinical correlates and prognostic significance of plasma GDF15 in heart failure with preserved ejection fraction (HFpEF) vs. reduced ejection fraction(HFrEF), compared with N‐terminal pro‐brain natriuretic peptide (NT‐proBNP), an indicator of haemodynamic wall stress.

Mechanism of NS2B-mediated activation of NS3pro in dengue virus: molecular dynamics simulations and bioassays.

ABSTRACT The NS2B cofactor is critical for proteolytic activation of the flavivirus NS3 protease. To elucidate the mechanism involved in NS2B-mediated activation of NS3 protease, molecular dynamic simulation, principal component analysis, molecular docking, mutagenesis, and bioassay studies were carried out on both the dengue virus NS3pro and NS2B-NS3pro systems. The results revealed that the NS2B-NS3pro complex is more rigid than NS3pro alone due to its robust hydrogen bond and hydrophobic interaction networks within the complex. These potent networks lead to remodeling of the secondary and tertiary structures of the protease that facilitates cleavage sequence recognition and binding of substrates. The cofactor is also essential for proper domain motion that contributes to substrate binding. Hence, the NS2B cofactor plays a dual role in enzyme activation by facilitating the refolding of the NS3pro domain as well as being directly involved in substrate binding/interactions. Kinetic analyses indicated for the first time that Glu92 and Asp50 in NS2B and Gln27, Gln35, and Arg54 in NS3pro may provide secondary interaction points for substrate binding. These new insights on the mechanistic contributions of the NS2B cofactor to NS3 activation may be utilized to refine current computer-based search strategies to raise the quality of candidate molecules identified as potent inhibitors against flaviviruses.

MicroRNA and Heart Failure

Heart failure (HF) imposes significant economic and public health burdens upon modern society. It is known that disturbances in neurohormonal status play an important role in the pathogenesis of HF. Therapeutics that antagonize selected neurohormonal pathways, specifically the renin-angiotensin-aldosterone and sympathetic nervous systems, have significantly improved patient outcomes in HF. Nevertheless, mortality remains high with about 50% of HF patients dying within five years of diagnosis thus mandating ongoing efforts to improve HF management. The discovery of short noncoding microRNAs (miRNAs) and our increasing understanding of their functions, has presented potential therapeutic applications in complex diseases, including HF. Results from several genome-wide miRNA studies have identified miRNAs differentially expressed in HF cohorts suggesting their possible involvement in the pathogenesis of HF and their potential as both biomarkers and as therapeutic targets. Unravelling the functional relevance of miRNAs within pathogenic pathways is a major challenge in cardiovascular research. In this article, we provide an overview of the role of miRNAs in the cardiovascular system. We highlight several HF-related miRNAs reported from selected cohorts and review their putative roles in neurohormonal signaling.

Overview of MicroRNAs in Cardiac Hypertrophy, Fibrosis, and Apoptosis

MicroRNAs (miRNAs) are non-coding RNAs that play essential roles in modulating the gene expression in almost all biological events. In the past decade, the involvement of miRNAs in various cardiovascular disorders has been explored in numerous in vitro and in vivo studies. In this paper, studies focused upon the discovery of miRNAs, their target genes, and functionality are reviewed. The selected miRNAs discussed herein have regulatory effects on target gene expression as demonstrated by miRNA/3′ end untranslated region (3′UTR) interaction assay and/or gain/loss-of-function approaches. The listed miRNA entities are categorized according to the biological relevance of their target genes in relation to three cardiovascular pathologies, namely cardiac hypertrophy, fibrosis, and apoptosis. Furthermore, comparison across 86 studies identified several candidate miRNAs that might be of particular importance in the ontogenesis of cardiovascular diseases as they modulate the expression of clusters of target genes involved in the progression of multiple adverse cardiovascular events. This review illustrates the involvement of miRNAs in diverse biological signaling pathways and provides an overview of current understanding of, and progress of research into, of the roles of miRNAs in cardiovascular health and disease.

Effects of light spectrum in flatbed scanner densitometry of stained polyacrylamide gels

Coomassie Brilliant Blue is arguably the most common dye used in staining polyacrylamide electrophoresis gels. A densitometric analysis into the extent of coloring by the dye can provide a quantitative measure of the amount of protein present. In this work, the experimentally determined spectral optical density distributions of Coomassie Blue-stained gels with various masses of proteins present allowed the optical density range response using different illumination to be predicted. Numerical modeling uncovered the spectrum of light has pronounced effects on the optical density range; wherein a higher scale translates to improved sensitivity. Generally, two factors contribute positively to this effect: (i) having the spectrum peak close to the 593-nm maximal absorption band of Coomassie Blue and (ii) possessing a spectrum width as narrow as possible. Based on this, we demonstrate that cost-effective densitometry can be achieved using a flatbed scanner with red light-emitting diode (LED) illumination, yielding results comparable to that of a commercial densitometer.

Novel non-peptide β-secretase inhibitors derived from structure-based virtual screening and bioassay

This Letter describes an efficient approach by integrating virtual screening with bioassay technology for finding small organic inhibitors targeting beta-secretase (BACE-1). Fifteen hits with inhibitory potencies ranging from 2.8 to 118 microM (IC(50)) against beta-secretase were successfully identified. Compound 12 with IC(50) of 2.8 microM is the most potent hit against BACE-1. Docking simulation from gold 3.0 suggests putative binding mode of 12 in BACE-1 and potential key pharmacophore groups for further designing of non-peptide compounds as more powerful inhibitors against BACE-1.

Surface-scribed transparency-based microplates

Transparency sheets, which are normally associated with use on overhead projectors, offer lowered costs and high amenability for optical diagnostics in microplate instrumentation. An alternative microplate design in which circles are scribed on the surface of the transparency to create the boundaries to hold the drop in place is investigated here. The 3D profile of the scribed regions obtained optically showed strong likelihood of affecting three-phase contact line interactions. During dispensation, the contact angle (≈95°) was larger than the drop advancing state (≈80°) due to a period of nonadhesion, where the contact angle later reduced to the drop advancing state followed by increase in the liquid area coverage on the substrate. It was established that 50 μL was needed to fill the well fully, and the maximum volume retainable before breaching was 190 μL. While the tilt angle needed for displacement reduced significantly from 50 to 95 μL, this was markedly better than nonscribed surfaces, where tilt angles always had to be kept to within 30°. It was found that there was greater ability to fill the well with smaller volumes with dispensation at the center. This was attributed to the growing contact line not meeting the scribed edge in parallel if liquid was dispensed closer to it, wherein pinning reduction in some directions permitted liquid travel along the scribed edge to undergo contact angle hysteresis. Fluorescence measurements conducted showed no performance compromise when using scribed transparency microplates over standard microplates.