Papers by Tirayut Vilaivan
Label free electrochemical DNA biosensor for COVID-19 diagnosis
Talanta
Scientific Reports, 2020
Staphylococcus aureus strains carrying enterotoxin A gene (sea) causes food poisoning and cannot ... more Staphylococcus aureus strains carrying enterotoxin A gene (sea) causes food poisoning and cannot be distinguished from non-pathogenic strains by the culture method. Here, we developed a rapid, specific and sensitive visual detection of sea using loop-mediated isothermal amplification (LAMP) combined with nanogold probe (AuNP) or styryl dye (STR). LAMP-AuNP and LAMP-STR can detect as low as 9.7 fg (3.2 sea copies) and 7.2 sea copies, respectively, which were lower than PCR (97 fg or 32 sea copies). The excellent performance of these new assays was demonstrated in food samples using crude DNA lysates. While the culture method detected 104 CFU/g in ground pork and 10 CFU/mL in milk in 5–7 days, LAMP-AuNP could detect down to 10 CFU/g for both samples in 27 minutes. Analyzing 80 pork and milk samples revealed that the LAMP-AuNP showed 100% sensitivity, 97–100% specificity and 97.5–100% accuracy, which were superior to the culture method, and comparable to PCR but without requirement of ...
Journal of Agricultural and Food Chemistry, 2019
We report herein a practical method for non-lethal detection of the antibiotic sulfamethazine in ... more We report herein a practical method for non-lethal detection of the antibiotic sulfamethazine in pig body fluids via the combination of simple extraction and paper spray mass spectrometry (PS-MS). This method requires minimal sample preparation, while still providing high sensitivities and accuracies in complex matrices including pig whole blood (LOD = 7.9 g/L; recovery = 95.4-103.7%), pig serum (LOD = 11.5 g/L; recovery = 103.2-106.2%), and synthetic urine (LOD = 11.2 g/L; recovery = 99.1-103.2%). Given a known correlation between the level of sulfamethazine in body fluids and edible tissues, this method shows great promise as a practical and non-lethal solution for rapid testing of the drug, which can substantially aid managerial decision in the livestock industry.
Molecules
In the fight towards eradication of malaria, identifying compounds active against new drug target... more In the fight towards eradication of malaria, identifying compounds active against new drug targets constitutes a key approach. Plasmodium falciparum 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase (PfHPPK) has been advanced as a promising target, as being part of the parasite essential folate biosynthesis pathway while having no orthologue in the human genome. However, no drug discovery efforts have been reported on this enzyme. In this study, we conducted a three-step screening of our in-house antifolate library against PfHPPK using a newly designed PfHPPK-GFP protein construct. Combining virtual screening, differential scanning fluorimetry and enzymatic assay, we identified 14 compounds active against PfHPPK. Compounds’ binding modes were investigated by molecular docking, suggesting competitive binding with the HMDP substrate. Cytotoxicity and in vitro ADME properties of hit compounds were also assessed, showing good metabolic stability and low toxicity. The most active compo...
Acta crystallographica. Section F, Structural biology and crystallization communications, 2009
Trypanosoma cruzi dihydrofolate reductase-thymidylate synthase (TcDHFR-TS) was crystallized in co... more Trypanosoma cruzi dihydrofolate reductase-thymidylate synthase (TcDHFR-TS) was crystallized in complexes with the dihydrotriazine-based or quinazoline-based antifolates C-448, cycloguanil (CYC) and Q-8 in order to gain insight into the interactions of this DHFR enzyme with classical and novel inhibitors. The TcDHFR-TS-C-448-NDP-dUMP crystal belonged to space group C222(1) with two molecules per asymmetric unit and diffracted to 2.37 angstrom resolution. The TcDHFR-TS-CYC, TcDHFR-TS-CYC-NDP and TcDHFR-TS-Q-8-NDP crystals belonged to space group P2(1) with four molecules per asymmetric unit and diffracted to 2.1, 2.6 and 2.8 angstrom resolution, respectively. Crystals belonging to the two different space groups were suitable for structure determination.
Novel thiolated amino-alcohols as chiral ligands for copper-catalyzed asymmetric nitro-aldol reactions
Tetrahedron Letters, 2007
Thiolated amino-alcohols have been synthesized and evaluated as a potential new class of chiral l... more Thiolated amino-alcohols have been synthesized and evaluated as a potential new class of chiral ligands for copper-catalyzed nitro-aldol reactions. The model nitro-aldol reaction took place smoothly at ambient temperature in the presence of catalytic amounts (5–15mol%) of the ligands and copper(II) acetate to afford the nitro-aldol product in good to excellent yield without accompanying dehydration. Amino-alcohol ligands bearing N-(2-alkylthio)benzyl substituents
Journal of Natural Products, 2010
RSC Advances, 2014
Internally pyrene-labeled pyrrolidinyl PNA yields much larger fluorescence increase than terminal... more Internally pyrene-labeled pyrrolidinyl PNA yields much larger fluorescence increase than terminally labeled PNA upon hybridization with complementary DNA.
Facile conversion of ATP-binding RNA aptamer to quencher-free molecular aptamer beacon
Bioorganic & medicinal chemistry letters, Jan 15, 2018
We have developed RNA-based quencher-free molecular aptamer beacons (RNA-based QF-MABs) for the d... more We have developed RNA-based quencher-free molecular aptamer beacons (RNA-based QF-MABs) for the detection of ATP, taking advantage of the conformational changes associated with ATP binding to the ATP-binding RNA aptamer. The RNA aptamer, with its well-defined structure, was readily converted to the fluorescence sensors by incorporating a fluorophore into the loop region of the hairpin structure. These RNA-based QF-MABs exhibited fluorescence signals in the presence of ATP relative to their low background signals in the absence of ATP. The fluorescence emission intensity increased upon formation of a RNA-based QF-MAB·ATP complex.
Pyrrolidinyl PNA polypyrrole/silver nanofoam electrode as a novel label-free electrochemical miRNA-21 biosensor
Biosensors & bioelectronics, Jan 6, 2017
A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nuclei... more A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportion...
N-Salicyl-�-aminoalcohols as a New Class of Ligand for Catalytic Asymmetric Strecker Reactions
Tetrahedron Lett, 2003
Tetrahedron Lett, 2001
Novel pyrrolidinyl peptide nucleic acids comprising alternate sequences of nucleobase-modified D-... more Novel pyrrolidinyl peptide nucleic acids comprising alternate sequences of nucleobase-modified D-proline and b-amino acid spacers selected from L-aminopyrrolidine-2-carboxylic acid, D-aminopyrrolidine-2-carboxylic acid, (1R,2S)-2-aminocyclopentane carboxylic acid and b-alanine were synthesized using solid phase methodology. Gel-binding shift assay revealed that only the homothymine PNA decamer bearing D-aminopyrrolidine-2-carboxylic acid spacer binds with (dA) 10 .
Immobilization-free electrochemical DNA detection with anthraquinone-labeled pyrrolidinyl peptide nucleic acid probe
Talanta, 2015
Electrochemical detection provides a simple, rapid, sensitive and inexpensive method for DNA dete... more Electrochemical detection provides a simple, rapid, sensitive and inexpensive method for DNA detection. In traditional electrochemical DNA biosensors, the probe is immobilized onto the electrode. Hybridization with the DNA target causes a change in electrochemical signal, either from the intrinsic signal of the probe/target or through a label or a redox indicator. The major drawback of this approach is the requirement for probe immobilization in a controlled fashion. In this research, we take the advantage of different electrostatic properties between PNA and DNA to develop an immobilization-free approach for highly sequence-specific electrochemical DNA sensing on a screen-printed carbon electrode (SPCE) using a square-wave voltammetric (SWV) technique. Anthraquinone-labeled pyrrolidinyl peptide nucleic acid (AQ-PNA) was employed as a probe together with an SPCE that was modified with a positively-charged polymer (poly quaternized-(dimethylamino-ethyl)methacrylate, PQDMAEMA). The electrostatic attraction between the negatively-charged PNA-DNA duplex and the positively-charged modified SPCE attributes to the higher signal of PNA-DNA duplex than that of the electrostatically neutral PNA probe, resulting in a signal change. The calibration curve of this proposed method exhibited a linear range between 0.35 and 50nM of DNA target with a limit of detection of 0.13nM (3SDblank/Slope). The sub-nanomolar detection limit together with a small sample volume required (20μL) allowed detection of <10fmol (<1ng) of DNA. With the high specificity of the pyrrolidinyl PNA probe used, excellent discrimination between complementary and various single-mismatched DNA targets was obtained. An application of this new platform for a sensitive and specific detection of isothermally-amplified shrimp's white spot syndrome virus (WSSV) DNA was successfully demonstrated.
Solid-phase synthesis of novel peptide nucleic acids
Journal of the Chemical Society, Perkin Transactions 1, 1997
... Lysine was included at the C-terminus to prevent self-aggregation of the oligomers as suggest... more ... Lysine was included at the C-terminus to prevent self-aggregation of the oligomers as suggested by Egholm and co-workers.2 The presence of an additional positively ... All other reagents were obtained at highest purity grade available either from Aldrich Chemical Company Ltd. ...
ChemInform Abstract: Enantioselective Synthesis of 4-Heterosubstituted Cyclopentenones
ChemInform, 2013
Clicked polycyclic aromatic hydrocarbon as a hybridization-responsive fluorescent artificial nucleobase in pyrrolidinyl peptide nucleic acids
Tetrahedron, 2012
ABSTRACT Pyrene as well as other aromatic hydrocarbons could be successfully incorporated in to p... more ABSTRACT Pyrene as well as other aromatic hydrocarbons could be successfully incorporated in to pyrrolidinyl peptide nucleic acid bearing a D-prolyl-2-aminocyclopentane carboxylic acid backbone (acpcPNA) as a base surrogate via a triazole linker employing Cu- catalyzed alkyne-azide cycloaddition (click chemistry). The labeling can be performed via a pre-clicked pyrene monomer or by post-synthetic modification of azide-containing acp cPNA on solid support. Thermal denaturation experiments suggested that the pyrene-triazole unit can be have as a universal base in the acpcPNA system. The mode of base-pairing has been proposed based on molecular dynamics simulations. Importantly, the fluorescence spectra of the pyrene-labeled single stranded acpcPNA and its hybrid with DNA are quite different. The ratio of emission s at 380 and 460 nm changed significantly (up to a factor of 7) upon hybrid formation with complementary DNA.
Pyrrolidinyl Peptide Nucleic Acid Homologues: Effect of Ring Size on Hybridization Properties
Organic Letters, 2012
The effect of ring size of four- to six-membered cyclic β-amino acid on the hybridization propert... more The effect of ring size of four- to six-membered cyclic β-amino acid on the hybridization properties of pyrrolidinyl peptide nucleic acid with an alternating α/β peptide backbone is reported. The cyclobutane derivatives (acbcPNA) show the highest T(m) and excellent specificity with cDNA and RNA.
CHEMICAL & PHARMACEUTICAL BULLETIN, 2011
Plants belonging to the genus Gardenia have proved to produce a variety of cycloartane triterpeno... more Plants belonging to the genus Gardenia have proved to produce a variety of cycloartane triterpenoids, some of which display interesting biological activities. 1-5) Additionally, extracts of various species exhibiting anti-implantation and abortifacient effects, 6) and antiulcer, 7) antibacterial, 8) diuretic, analgesic, hypertensive, and larvicidal activities 9,10) have been reported. Previous investigations on the plants in this genus have led to the isolation of an array of structurally diverse cycloartanes with a wide range of biological activities, particularly cytotoxic and anti-human immunodeficiency virus (HIV) effects. 2,3) Recently, we have also reported the isolation and identification of a number of cytotoxic 3,4seco-cycloartane triterpenoids from two species found in Thailand, G. sootepensis and G. tubifera. 11,12) This prompted us to investigate another plant in this genus, G. obtusifolia. The current paper describes the isolation, characterization and cytotoxicity of four new cycloartane triterpenes (1-4) from the EtOAc extract of apical buds of G. obtusifolia, together with five known compounds, dikamakiartanes A, C and D (5-7), 5a-cycloart-24-ene-3,16,23-trione (8) and secaubryenol (9). Results and Discussion Gardenoin E (1) was obtained as a white, amorphous solid. Its molecular formula was established as C 30 H 46 O 3 by the high resolution-electrospray ionization-mass spectrum (HR-ESI-MS) ion at m/z 477.3341 [MϩNa] ϩ (Calcd 477.3345), indicating eight degrees of unsaturation. The IR absorption bands at 3439 and 1712 cm Ϫ1 implied the presence of hydroxyl and carbonyl functionalities. The 1 H-NMR spectrum (Table 1) displayed a pair of doublets at d H 0.58 and 0.79 (Jϭ4.1 Hz), characteristic of the C-19 methylene protons of cyclopropane ring of a cycloartane triterpene. 13-16) The 13 C-NMR and heteronuclear single quantum coherence (HSQC) data revealed the presence of 30 nonequivalent carbons including two ketone carbonyls, six tertiary methyls, one secondary methyl, nine methylenes, six methines (one oxygenated and one olefinic) and six quaternary carbons (one olefinic). These NMR data indicated that three of the eight units of unsaturation come from one carbon-carbon double bond and two carbonyls. Therefore, the remaining five degrees required 1 to comprise a pentacyclic core. The above NMR data strongly suggested that 1 was a normal cycloartanone-type triterpenoid. The existence of two geminal vinylmethyls connected to a carbonyl group was corroborated by heteronuclear multiple bond connectivity (HMBC) correlations from olefinic proton at d H 6.11 (H-24) to a carbonyl (d C 202.6, C-23), Me-26 and Me-27. The NMR data of 1 were similar to those of 5a-cycloart-24-ene-3,16,23-trione (8), 2) except for the presence of a hydroxyl group at C-16 in
Bioorganic & Medicinal Chemistry Letters, 2011
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Papers by Tirayut Vilaivan