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Fulltext Crystal structure, Hirshfeld surface analysis and computational study of the 1:2 co-crystal formed between N,N'-bis-(pyridin-4-ylmeth-yl)ethane-diamide and 4-chloro-benzoic acid

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2020 Feb 01;76(Pt 2):245-253.
PMID: 32071755 DOI: 10.1107/S2056989020000572

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2·2C7H5ClO2, comprises two half mol-ecules of oxalamide (4 LH2), as each is disposed about a centre of inversion, and two mol-ecules of 4-chloro-benzoic acid (CBA), each in general positions. Each 4 LH2 mol-ecule has a (+)anti-periplanar conformation with the pyridin-4-yl residues lying to either side of the central, planar C2N2O2 chromophore with the dihedral angles between the respective central core and the pyridyl rings being 68.65 (3) and 86.25 (3)°, respectively, representing the major difference between the independent 4 LH2 mol-ecules. The anti conformation of the carbonyl groups enables the formation of intra-molecular amide-N-H⋯O(amide) hydrogen bonds, each completing an S(5) loop. The two independent CBA mol-ecules are similar and exhibit C6/CO2 dihedral angles of 8.06 (10) and 17.24 (8)°, indicating twisted conformations. In the crystal, two independent, three-mol-ecule aggregates are formed via carb-oxy-lic acid-O-H⋯N(pyrid-yl) hydrogen bonding. These are connected into a supra-molecular tape propagating parallel to [100] through amide-N-H⋯O(amide) hydrogen bonding between the independent aggregates and ten-membered {⋯HNC2O}2 synthons. The tapes assemble into a three-dimensional architecture through pyridyl- and methyl-ene-C-H⋯O(carbon-yl) and CBA-C-H⋯O(amide) inter-actions. As revealed by a more detailed analysis of the mol-ecular packing by calculating the Hirshfeld surfaces and computational chemistry, are the presence of attractive and dispersive Cl⋯C=O inter-actions which provide inter-action energies approximately one-quarter of those provided by the amide-N-H⋯O(amide) hydrogen bonding sustaining the supra-molecular tape.
Psychiatric sequelae of Amok

Tan EK, Carr JE

Cult Med Psychiatry, 1977 Apr;1(1):59-67.
PMID: 756354

The authors present evidence of an indigenous diagnostic system by which Malay culture defines Amok, and of the disparate relations between individual conceptualization, behavior, and tradition which contributes to the labeling process. Amok is viewed as a cultural prescription for violent behavior in response to a given set of conditions. It is not a disease but rather a behavioral sequence, perceived as illness, that may be precipitated by various etiological factors. Finally, evidence is presented to support the hypothesis that traditional forms of Amok are being replaced by new variants in which psychopathology is increasingly evident.
Allomonal and hepatotoxic effects following methyl eugenol consumption in Bactrocera papayae male against Gekko monarchus

Wee SL, Tan KH

J Chem Ecol, 2001 May;27(5):953-64.
PMID: 11471947 DOI: 10.1023/A:1010387020135

Methyl eugenol (ME), is converted into two major phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and trans-coniferyl alcohol, following consumption by the male fruit fly Bactrocera papayae. Chemical analysis of wild male B. papayae rectal glands, where the compounds are sequestered, revealed the presence of ME metabolites in varying quantities. These phenylpropanoids are shown to be involved in the fruit fly defense both in no-choice and choice feeding tests against the Malayan spiny gecko, Gekko monarchus. After being acclimatized to feeding on fruit flies, geckos consumed significantly fewer ME-fed male flies than controls that consumed all the ME-deprived male flies offered throughout a two-week period. Diagnosis of dissected livers from geckos that consumed ME-fed male flies revealed various abnormalities. These included discoloration and hardening of liver tissue, whitening of the gallbladder, or presence of tumor-like growths in all geckos that consumed ME-fed male flies. Control geckos fed on ME-deprived male flies had healthy livers. When given an alternative prey, geckos preferred to eat untreated house flies, Musca domestica to avoid preying on ME-fed fruit flies.
Evidence of natural hybridization between two sympatric sibling species of Bactrocera dorsalis complex based on pheromone analysis

Wee SL, Tan KH

J Chem Ecol, 2005 Apr;31(4):845-58.
PMID: 16124255 DOI: 10.1007/s10886-005-3548-6

Bactrocera carambolae and B. papayae are major fruit fly pests and sympatric sibling species of the B. dorsalis complex. They possess distinct differences in male pheromonal components. In the 1990's, wild Bactrocera fruit flies with morphological traits intermediate between those of B. carambolae and B. papayae were often captured in traps baited with methyl eugenol (ME). Chemical analyses of rectal glands of ME-fed males revealed that the laboratory Fl, F2, and backcross hybrids possessed ME-derived sex pheromonal components ranging from that typical of B. papayae to that of B. carambolae without any specific trend, which included a combination of pheromonal components from both parental species within an individual hybrid. ME-fed hybrids without any ME-derived pheromonal components were also detected. Further chemical analysis of rectal glands from wild Bactrocera males, after ME feeding in the laboratory, showed a combination of pheromonal components similar to that found in the ME-fed, laboratory-bred hybrids. These findings present circumstantial evidence for the occurrence of a natural hybrid of the two Bactrocera species.
Male sex pheromonal components derived from methyl eugenol in the hemolymph of the fruit fly Bactrocera papayae

Hee AK, Tan KH

J Chem Ecol, 2004 Nov;30(11):2127-38.
PMID: 15672660 DOI: 10.1023/B:JOEC.0000048778.02561.70

Pharmacophagy of methyl eugenol (ME)--a highly potent male attractant, by Bactrocera papayae results in the hydroxylation of ME to sex pheromonal components, 2-ally-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (CF). These compounds, which are also male attractants, are then sequestered and stored in the rectal gland prior to their release during courtship at dusk. Chemical analyses of the digestive tract (excluding the crop and rectal gland) showed the absence of the sex pheromonal components and their precursor, ME. However, B. papayae males were attracted to and fed on the ME-fed male hemolymph extracts but not on hemolymph extracts of ME-deprived males. After thin layer chromatography in a hexane:ethyl acetate solvent system, flies were attracted to and fed on the original point on the TLC plate where the hemolymph extract had been spotted, suggesting that the pheromone components were bound in polar complexes. Chemical analyses of the ME-fed male hemolymph and crop extracts revealed the presence of the sex pheromonal components. The presence of the ME-derived pheromonal components and the absence of ME in the hemolymph suggest that the hemolymph is involved in the transportation of sex pheromonal components from the crop to the rectal gland.
Fulltext Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells: implications in chromosome rearrangement

Tan SN, Sim SP

BMC Cancer, 2018 04 12;18(1):409.
PMID: 29649994 DOI: 10.1186/s12885-018-4327-4

BACKGROUND: Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, caspase-activated deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC.
METHODS: We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced.
RESULTS: BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient.
CONCLUSIONS: These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells.
Fulltext DNA, RNA, and protein extraction: the past and the present

Tan SC, Yiap BC

J Biomed Biotechnol, 2009;2009:574398.
PMID: 20011662 DOI: 10.1155/2009/574398

Extraction of DNA, RNA, and protein is the basic method used in molecular biology. These biomolecules can be isolated from any biological material for subsequent downstream processes, analytical, or preparative purposes. In the past, the process of extraction and purification of nucleic acids used to be complicated, time-consuming, labor-intensive, and limited in terms of overall throughput. Currently, there are many specialized methods that can be used to extract pure biomolecules, such as solution-based and column-based protocols. Manual method has certainly come a long way over time with various commercial offerings which included complete kits containing most of the components needed to isolate nucleic acid, but most of them require repeated centrifugation steps, followed by removal of supernatants depending on the type of specimen and additional mechanical treatment. Automated systems designed for medium-to-large laboratories have grown in demand over recent years. It is an alternative to labor-intensive manual methods. The technology should allow a high throughput of samples; the yield, purity, reproducibility, and scalability of the biomolecules as well as the speed, accuracy, and reliability of the assay should be maximal, while minimizing the risk of cross-contamination.
Fulltext Alternanthera sessilis Red Ethyl Acetate Fraction Exhibits Antidiabetic Potential on Obese Type 2 Diabetic Rats

Tan KK, Kim KH

Evid Based Complement Alternat Med, 2013;2013:845172.
PMID: 23606892 DOI: 10.1155/2013/845172

The antidiabetic potential of Alternanthera sessilis Red was investigated using the obese type 2 diabetic rats induced by high fat diet and streptozotocin. Three fractions (hexane, ethyl acetate, and water) were obtained from the crude ethanol extract of Alternanthera sessilis Red. Alternanthera sessilis Red ethyl acetate fraction (ASEAF) was found to possess the most potent antihyperglycemic effect through oral glucose tolerance test. The ASEAF was subsequently given to the diabetic rats for two weeks. It was found that two-week administration of ASEAF reduces the fasting blood glucose level, triglyceride level, and free fatty acid level of the rats. ASEAF-treated diabetic rats showed higher pancreatic insulin content and pancreatic total superoxide dismutase activity compared to the untreated diabetic rats. Also, the insulin sensitivity indexes suggested that ASEAF ameliorates the insulin resistant state of the diabetic rats. In conclusion, ASEAF could be developed into a potential antidiabetic agent for the management of type 2 diabetes.
Fulltext A 1:2 co-crystal of 2,2'-thiodi-benzoic acid and tri-phenyl-phosphane oxide: crystal structure, Hirshfeld surface analysis and computational study

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2018 Dec 01;74(Pt 12):1764-1771.
PMID: 30574371 DOI: 10.1107/S205698901801544X

The asymmetric unit of the title co-crystal, 2,2'-thiodi-benzoic acid-tri-phenyl-phosphane oxide (1/2), C14H10O4S·2C18H15OP, comprises two mol-ecules of 2,2'-thiodi-benzoic acid [TDBA; systematic name: 2-[(2-carb-oxy-phen-yl)sulfan-yl]benzoic acid] and four mol-ecules of tri-phenyl-phosphane oxide [TPPO; systematic name: (di-phenyl-phosphor-yl)benzene]. The two TDBA mol-ecules are twisted about their di-sulfide bonds and exhibit dihedral angles of 74.40 (5) and 72.58 (5)° between the planes through the two SC6H4 residues. The carb-oxy-lic acid groups are tilted out of the planes of the rings to which they are attached forming a range of CO2/C6 dihedral angles of 19.87 (6)-60.43 (8)°. Minor conformational changes are exhibited in the TPPO mol-ecules with the range of dihedral angles between phenyl rings being -2.1 (1) to -62.8 (1)°. In the mol-ecular packing, each TDBA acid mol-ecule bridges two TPPO mol-ecules via hy-droxy-O-H⋯O(oxide) hydrogen bonds to form two three-mol-ecule aggregates. These are connected into a three-dimensional architecture by TPPO-C-H⋯O(oxide, carbon-yl) and TDBA-C-H⋯(oxide, carbon-yl) inter-actions. The importance of H⋯H, O⋯H/H⋯O and C⋯H/H⋯C contacts to the calculated Hirshfeld surfaces has been demonstrated. In terms of individual mol-ecules, O⋯H/H⋯O contacts are more important for the TDBA (ca 28%) than for the TPPO mol-ecules (ca 13%), as expected from the chemical composition of these species. Computational chemistry indicates the four independent hy-droxy-O-H⋯O(oxide) hydrogen bonds in the crystal impart about the same energy (ca 52 kJ mol-1), with DTBA-phenyl-C-H⋯O(oxide) inter-actions being next most stabilizing (ca 40 kJ mol-1).
The current state of understanding of oncology expanded access programs in Malaysia

Yong FL, Tan WC

Med J Malaysia, 2024 Mar;79(2):191-195.
PMID: 38553925

INTRODUCTION: An expanded access program (EAP) is a regulatory mechanism that provides access to an investigational drug, which is not approved for use, in treating life-threatening conditions when all the standard-ofcare treatments are exhausted.
MATERIALS AND METHODS: An online, anonymous, voluntary survey was conducted to assess the level of knowledge and understanding about EAPs among Malaysian oncologists using SurveyMonkey® between April 2020 and June 2020. Oncologists who had enquired about EAP in the past, were invited at random to participate in the survey. Participants who did not provide consent or failed to complete the survey were excluded.
RESULTS: A total of 15 oncologists participated in the survey, from both public (46.6%) and private (46.6%) practices. Most respondents (80%) had filed between 1 to 10 EAP applications in the past 12 months. For 73.3% respondents, resources or training were not provided for EAPs from institutions. Around 53% of the respondents reported that their knowledge of EAPs and application processes including country regulations is 'good'. The majority of respondents (73.3%) reported that the educational modules on an overview of EAPs, country regulations and the EAP application process will be beneficial. Most participants received information about the existing EAPs either by reaching out to a pharmaceutical sponsor or through another health care provider and some received information about the existing EAPs through their institutions or patients/caregivers. Most of the respondents recommended that pharmaceutical companies should have readily available information related to the availability and application of EAPs for all pipeline products on their websites.
DISCUSSION: EAPs are crucial treatment access pathways to provide investigational drugs to patients who have exhausted their treatment options and are not eligible for participation in clinical trials. Malaysian oncologists have a fair understanding about the EAPs and the application processes.
CONCLUSION: Additional training and awareness are needed for Malaysian oncologists to upscale the utilisation of EAPs.
Fulltext Drosophila melanogaster: Deciphering Alzheimer's Disease

Tan FHP, Azzam G

Malays J Med Sci, 2017 Mar;24(2):6-20.
PMID: 28894399 MyJurnal DOI: 10.21315/mjms2017.24.2.2

Alzheimer's disease (AD) is the most widespread neurodegenerative disorder worldwide. Its pathogenesis involves two hallmarks: aggregation of amyloid beta (Aβ) and occurrence of neurofibrillary tangles (NFTs). The mechanism behind the disease is still unknown. This has prompted the use of animal models to mirror the disease. The fruit fly, Drosophila melanogaster has garnered considerable attention as an organism to recapitulate human disorders. With the ability to monopolise a multitude of traditional and novel genetic tools, Drosophila is ideal for studying not only cellular aspects but also physiological and behavioural traits of human neurodegenerative diseases. Here, we discuss the use of the Drosophila model in understanding AD pathology and the insights gained in discovering drug therapies for AD.
Effectiveness of mHealth apps on adherence and symptoms to oral anticancer medications: a systematic review and meta-analysis

Chow SM, Tan BK

Support Care Cancer, 2024 Jun 12;32(7):426.
PMID: 38864924 DOI: 10.1007/s00520-024-08635-8

PURPOSE: Despite the rapid expansion of mHealth apps, their adoption has not always been based on evidence of effectiveness on patient outcomes. This systematic review aimed to determine the effect of mHealth apps on adherence and symptom to oral anticancer medications (OAMs) and identify the app design that led to such effects.
METHODS: Pubmed, Cochrane Central, PsycINFO, EMBASE, and WoS were searched from inception to April 2023. Randomised controlled trials (RCTs) that evaluated effects of mHealth apps on primary outcomes OAM adherence and symptom burden were included. Two reviewers independently assessed risk-of-bias using Cochrane Risk-of-Bias version 2 and extracted the data. Quality of evidence was assessed using GRADE. The protocol was registered in PROSPERO (CRD42023406024).
RESULTS: Four RCTs involving 806 patients with cancer met the eligibility criteria. mHealth apps features included a combinations of symptom reporting, medication reminder, automated alert to care team, OAM and side effect information, one study implemented structured follow-up by a nurse. The intervention group showed no significant difference in OAM adherence (relative ratio 1.20; 95% CI 1.00 to 1.43), but significantly improved symptoms to OAMs with a lower standardised mean symptom burden score of 0.49 (SMD - 0.49; 95% CI - 0.93 to - 0.06), and a 25% lower risk of grade 3 or 4 toxicity (risk ratio 0.75; 95% CI 0.58 to 0.95) compared to usual care.
CONCLUSION: These findings suggest a potential role for mHealth app in managing OAM side effect. Further research should explore the role of AI-guided algorithmic pathways on the interactive features of mHealth apps.
Fulltext A 1:1:1 co-crystal solvate comprising 2,2'-di-thiodi-benzoic acid, 2-chloro-benzoic acid and N,N-di-methyl-formamide: crystal structure, Hirshfeld surface analysis and computational study

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2019 Apr 01;75(Pt 4):475-481.
PMID: 31161060 DOI: 10.1107/S205698901900375X

The asymmetric unit of the three-component title compound, 2,2'-di-thiodi-benzoic acid-2-chloro-benzoic acid-N,N-di-methyl-formamide (1/1/1), C14H10O4S2·C7H5ClO2·C3H7NO, contains a mol-ecule each of 2,2'-di-thiodi-benzoic acid (DTBA), 2-chloro-benzoic acid (2CBA) and di-methyl-formamide (DMF). The DTBA mol-ecule is twisted [the C-S-S-C torsion angle is 88.37 (17)°] and each carb-oxy-lic group is slightly twisted from the benzene ring to which it is connected [CO2/C6 dihedral angles = 7.6 (3) and 12.5 (3)°]. A small twist is evident in the mol-ecule of 2CBA [CO2/C6 dihedral angle = 4.4 (4)°]. In the crystal, the three mol-ecules are connected by hydrogen bonds with the two carb-oxy-lic acid residues derived from DTBA and 2CBA forming a non-symmetric eight-membered {⋯HOCO}2 synthon, and the second carb-oxy-lic acid of DTBA linked to the DMF mol-ecule via a seven-membered {⋯HOCO⋯HCO} heterosynthon. The three-mol-ecule aggregates are connected into a supra-molecular chain along the a axis via DTBA-C-H⋯O(hydroxyl-2CBA), 2CBA-C-H⋯O(hydroxyl-DTBA) and DTBA-C-H⋯S(DTBA) inter-actions. Supra-molecular layers in the ab plane are formed as the chains are linked via DMF-C-H⋯S(DTBA) contacts, and these inter-digitate along the c-axis direction without specific points of contact between them. A Hirshfeld surface analysis points to additional but, weak contacts to stabilize the three-dimensional architecture: DTBA-C=O⋯H(phenyl-DTBA), 2CBA-Cl⋯H(phenyl-DTBA), as well as a π-π contact between the delocalized eight-membered {⋯HOC=O}2 carb-oxy-lic dimer and the phenyl ring of 2CBA. The latter was confirmed by electrostatic potential (ESP) mapping.
Fulltext Feeding Practices during the COVID-19 Lockdown: Is there a Difference between Stay-at-Home Mothers and Work-from-Home Mothers?

Tan ST, Rajan DS

Malays J Med Sci, 2022 Dec;29(6):164-169.
PMID: 36818892 DOI: 10.21315/mjms2022.29.6.16

This study aims to compare the feeding practices adopted by stay-at-home mothers and work-from-home mothers during the COVID-19 lockdown. Feeding practices were assessed using a 39-item validated Comprehensive Feeding Practices Questionnaire (CFPQ). The Multivariate Analysis of Covariance (MANCOVA) was used to determine the mean difference in feeding practices by maternal employment status after adjusting for the mother's age and educational attainment and the child's age and gender. The current study revealed that a noticeable proportion of mothers adopted feeding practices that encourage balance and variety (4.45 ± 0.62), promote a healthy environment (4.34 ± 0.81) and impose dietary restrictions for health (4.32 ± 1.04) during the COVID-19 pandemic. There was no significant difference (P > 0.05) in the mean scores of feeding practices across maternal employment status, except for the emotion regulation and modelling subscales. Work-from-home mothers had a significantly higher mean score in the emotion regulation subscale than stay-at-home mothers (F = 14.892, P < 0.001). In comparison to work-from-home mothers, stay-at-home mothers had a significantly higher mean score in the modelling subscale during the COVID-19 pandemic (F = 4.163, P = 0.044). In conclusion, there was just a modest variation in the feeding practices adopted by stay-at-home mothers and work-from-home mothers in this unprecedented pandemic.
Fulltext Curcumin Combination Chemotherapy: The Implication and Efficacy in Cancer

Tan BL, Norhaizan ME

Molecules, 2019 Jul 10;24(14).
PMID: 31295906 DOI: 10.3390/molecules24142527

Many chemotherapeutic drugs have been used for the treatment of cancer, for instance, doxorubicin, irinotecan, 5-fluorouracil, cisplatin, and paclitaxel. However, the effectiveness of chemotherapy is limited in cancer therapy due to drug resistance, therapeutic selectivity, and undesirable side effects. The combination of therapies with natural compounds is likely to increase the effectiveness of drug treatment as well as reduce the adverse outcomes. Curcumin, a polyphenolic isolated from Curcuma longa, belongs to the rhizome of Zingiberaceae plants. Studies from in vitro and in vivo revealed that curcumin exerts many pharmacological activities with less toxic effects. The biological mechanisms underlying the anticancer activity of co-treatment curcumin and chemotherapy are complex and worth to discuss further. Therefore, this review aimed to address the molecular mechanisms of combined curcumin and chemotherapy in the treatment of cancer. The anticancer activity of combined nanoformulation of curcumin and chemotherapy was also discussed in this study. Taken together, a better understanding of the implication and underlying mechanisms of action of combined curcumin and chemotherapy may provide a useful approach to combat cancer diseases.
Fulltext The 1:2 co-crystal formed between N,N'-bis(pyridin-4-ylmeth-yl)ethanedi-amide and benzoic acid: crystal structure, Hirshfeld surface analysis and computational study

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2020 Jan 01;76(Pt 1):102-110.
PMID: 31921461 DOI: 10.1107/S2056989019016840

The crystal and mol-ecular structures of the title 1:2 co-crystal, C14H14N4O2·2C7H6O2, are described. The oxalamide mol-ecule has a (+)-anti-periplanar conformation with the 4-pyridyl residues lying to either side of the central, almost planar C2N2O2 chromophore (r.m.s. deviation = 0.0555 Å). The benzoic acid mol-ecules have equivalent, close to planar conformations [C6/CO2 dihedral angle = 6.33 (14) and 3.43 (10)°]. The formation of hy-droxy-O-H⋯N(pyrid-yl) hydrogen bonds between the benzoic acid mol-ecules and the pyridyl residues of the di-amide leads to a three-mol-ecule aggregate. Centrosymmetrically related aggregates assemble into a six-mol-ecule aggregate via amide-N-H⋯O(amide) hydrogen bonds through a 10-membered {⋯HNC2O}2 synthon. These are linked into a supra-molecular tape via amide-N-H⋯O(carbon-yl) hydrogen bonds and 22-membered {⋯HOCO⋯NC4NH}2 synthons. The contacts between tapes to consolidate the three-dimensional architecture are of the type methyl-ene-C-H⋯O(amide) and pyridyl-C-H⋯O(carbon-yl). These inter-actions are largely electrostatic in nature. Additional non-covalent contacts are identified from an analysis of the calculated Hirshfeld surfaces.
Fulltext N,N'-Bis(pyridin-3-ylmeth-yl)ethanedi-amide monohydrate: crystal structure, Hirshfeld surface analysis and computational study

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2020 Jan 01;76(Pt 1):25-31.
PMID: 31921447 DOI: 10.1107/S2056989019016153

The mol-ecular structure of the title bis-pyridyl substituted di-amide hydrate, C14H14N4O2·H2O, features a central C2N2O2 residue (r.m.s. deviation = 0.0205 Å) linked at each end to 3-pyridyl rings through methyl-ene groups. The pyridyl rings lie to the same side of the plane, i.e. have a syn-periplanar relationship, and form dihedral angles of 59.71 (6) and 68.42 (6)° with the central plane. An almost orthogonal relationship between the pyridyl rings is indicated by the dihedral angle between them [87.86 (5)°]. Owing to an anti disposition between the carbonyl-O atoms in the core, two intra-molecular amide-N-H⋯O(carbon-yl) hydrogen bonds are formed, each closing an S(5) loop. Supra-molecular tapes are formed in the crystal via amide-N-H⋯O(carbon-yl) hydrogen bonds and ten-membered {⋯HNC2O}2 synthons. Two symmetry-related tapes are linked by a helical chain of hydrogen-bonded water mol-ecules via water-O-H⋯N(pyrid-yl) hydrogen bonds. The resulting aggregate is parallel to the b-axis direction. Links between these, via methyl-ene-C-H⋯O(water) and methyl-ene-C-H⋯π(pyrid-yl) inter-actions, give rise to a layer parallel to (10); the layers stack without directional inter-actions between them. The analysis of the Hirshfeld surfaces point to the importance of the specified hydrogen-bonding inter-actions, and to the significant influence of the water mol-ecule of crystallization upon the mol-ecular packing. The analysis also indicates the contribution of methyl-ene-C-H⋯O(carbon-yl) and pyridyl-C-H⋯C(carbon-yl) contacts to the stability of the inter-layer region. The calculated inter-action energies are consistent with importance of significant electrostatic attractions in the crystal.
Fulltext Crystal structure, Hirshfeld surface analysis and computational study of the 1:2 co-crystal formed between N,N'-bis-[(pyridin-4-yl)meth-yl]ethanedi-amide and 3-chloro-benzoic acid

Tan SL, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2020 Jun 01;76(Pt 6):870-876.
PMID: 32523755 DOI: 10.1107/S2056989020006568

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2·2C7H5ClO2, comprises a half-mol-ecule of oxalamide (4 LH2), being located about a centre of inversion, and a mol-ecule of3-chloro-benzoic acid (3-ClBA) in a general position. From symmetry, the 4 LH2 mol-ecule has a (+)anti-periplanar conformation with the 4-pyridyl residues lying to either side of the central, planar C2N2O2 chromophore with the dihedral angle between the core and pyridyl ring being 74.69 (11)°; intra-molecular amide-N-H⋯O(amide) hydrogen bonds are noted. The 3-ClBA mol-ecule exhibits a small twist as seen in the C6/CO2 dihedral angle of 8.731 (12)°. In the mol-ecular packing, three-mol-ecule aggregates are formed via carb-oxy-lic acid-O-H⋯N(pyrid-yl) hydrogen bonding. These are connected into a supra-molecular tape along [111] through amide-N-H⋯O(carbon-yl) hydrogen bonding. Additional points of contact between mol-ecules include pyridyl and benzoic acid-C-H⋯O(amide), methyl-ene-C-H⋯O(carbon-yl) and C-Cl⋯π(pyrid-yl) inter-actions so a three-dimensional architecture results. The contributions to the calculated Hirshfeld surface are dominated by H⋯H (28.5%), H⋯O/O⋯H (23.2%), H⋯C/C⋯H (23.3%), H⋯Cl/Cl⋯H (10.0%) and C⋯Cl/C⋯Cl (6.2%) contacts. Computational chemistry confirms the C-Cl⋯π inter-action is weak, and the importance of both electrostatic and dispersion terms in sustaining the mol-ecular packing despite the strong electrostatic term provided by the carb-oxy-lic acid-O-H⋯N(pyrid-yl) hydrogen bonds.
Fulltext Impulsivity, Gambling-Related Cognitions, Cognitive Reappraisal and Gambling Behaviour in a Malaysian Sample

Tan GSL, Tam CL

J Gambl Stud, 2024 Jun;40(2):475-492.
PMID: 37544960 DOI: 10.1007/s10899-023-10246-7

The relationships between cognitive reappraisal and problem gambling have been widely studied in different contexts. However, previous research findings remain inconsistent. This discrepancy might be attributed to the effects of interactions between cognitive reappraisal and other risk factors for problem gambling. Using moderation models, this study examined the association between impulsivity, gambling-related cognitive distortions, cognitive reappraisal and problem gambling in a sample of Malaysian gamblers. A total of 149 community gamblers (103 males, 46 females; mean age = 32.18) completed an online questionnaire. Problem gambling was measured with the South Oaks Gambling Screen (SOGS); cognitive reappraisal was measured using the Emotion Regulation Questionnaire-Cognitive Reappraisal Subscale (ERQ-CR); impulsivity was measured with the Short-UPPS-P Impulsive Behaviour Scale (SUPPS-P); and gambling-related cognitive distortions were measured using the Gambling Related Cognitions Scale (GRCS). The results revealed impulsivity and gambling-related cognitive distortions as significant predictors of problem gambling. At high levels, impulsivity and cognitive distortions are significant moderator variables that strengthen the association between cognitive reappraisal and problem gambling. These findings demonstrate that reappraisal skills could exacerbate problem gambling severity amongst impulsive or self-deceptive gamblers. Future research with larger and more representative samples is needed to validate and generalise these findings.
Acinetobacter baumannii subunit vaccines: recent progress and challenges

Lau YT, Tan HS

Crit Rev Microbiol, 2024 Aug;50(4):434-449.
PMID: 37211625 DOI: 10.1080/1040841X.2023.2215303

Acinetobacter baumannii is a Gram-negative, opportunistic pathogen that causes nosocomial infection with a high mortality rate in immunocompromised individuals. With the frequent emergence of multidrug-resistant A. baumannii strains that have rapidly gained resistance to most antibiotics, an extensive search for an effective A. baumannii vaccine is ongoing. Over the decade, many subunit vaccine candidates were identified using reverse vaccinology and in vivo animal studies for validation. Nineteen subunit vaccine candidates with a wide range of efficacy, from 14% to 100% preclinical survival rates, were included in this review. This article provides an updated review of several outer membrane proteins (Omp) that emerged as vaccine candidates with great potential, including OmpA, Omp34, Omp22 and BamA, based on their high conservancy, antigenicity, and immune protection against A. baumannii infection. However, there is still no licenced A. baumannii vaccine currently due to several practical issues that have yet to be resolved, such as inconsistencies between validation studies, antigen variability and insolubility. Moving forward, much investigation and innovation are still required to tackle these challenges for the regulatory approval of an A. baumannii subunit vaccine, including standardisation of immunisation study parameters, improving antigen solubility and the incorporation of nucleic acid vaccine technology.

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