A CF4 based positron trap

All buffer-gas positron traps in use today rely on N2 as the primary trapping gas due to its conveniently placed ${{\rm{a}}}^{1}{\rm{\Pi }}$ electronic excitation cross-section. The energy loss per excitation in this process is 8.5 eV, which is sufficient to capture positrons from low-energy moderated beams into a Penning-trap configuration of electric and magnetic fields. However, the energy range over which this cross-section is accessible overlaps with that for positronium (Ps) formation, resulting in inevitable losses and setting an intrinsic upper limit on the overall trapping efficiency of ~25%. In this paper we present a numerical simulation of a device that uses CF4 as the primary trapping gas, exploiting vibrational excitation as the main inelastic capture process. The threshold for such excitations is far below that for Ps formation and hence, in principle, a CF4 trap can be highly efficient; our simulations indicate that it may be possible to achieve trapping efficiencies as high as 90%. We also report the results of an attempt to re-purpose an existing two-stage N2-based buffer-gas positron trap. Operating the device using CF4 proved unsuccessful, which we attribute to back scattering and expansion of the positron beam following interactions with the CF4 gas, and an unfavourably broad longitudinal beam energy spread arising from the magnetic field differential between the source and trap regions. The observed performance was broadly consistent with subsequent simulations that included parameters specific to the test system, and we outline the modifications that would be required to realise efficient positron trapping with CF4. However, additional losses appear to be present which require further investigation through both simulation and experiment

Development of SARS-CoV-2 N-protein specific capture ELISA

Ta na dijagnoza ljudi sa sumnjom na infekciju SARS-CoV-2 je od suštinskog zna aja zasuzbijanje globalnog širenja COVID-19. Prisustvo SARS-CoV-2 može se otkriti RT-PCRom (otkriva RNK virusa) ili detekcijom prisustva virusnih antigena u biološkim te nostimaELISA-om ili sli nom tehnikom koje koriste antitela razvijena u životinjama. Cilj studijeje bio uspostavljanje kvantitativnog testa koji se zasniva na koriš enju poliklonskih serumaza rutinsko odre ivanje koncentracije SARS-CoV-2 nukleokapsidnog proteina merenjamapsorbancije u standardnoj mikrotitarskoj plo ici sa 96 bunara. Za potrebe razvoja testaproizveden je rekombinantni N-protein i koriš en za proizvodnju antiseruma u miševima ize evima. Proizvedeni antiserumi su pre iš eni i odre en im je titar. Poliklonskiantiserumivisokog afiniteta specifi ni za N-protein koriš eni su za razvoj ELISA testa specifi nog zaovaj protein. Test se zasniva na koriš enju poliklonskih seruma miševa koji su adheriranina dno bunara mikrotitarske plo ice za hvatanje N-proteina iz uzorka. Razli itekoncentracije rekombinantnog N-proteina su koriš ene za standardnu krivu zakvantifikaciju proteina. N-protein vezan za antitela miševa je detektovan ze jimpoliklonskim serumom i anti-ze jim antitelom povezanim sa enzimom koji obezbe ujespektrofotometrijsko merenje. Uspešno smo razvili prototip ELISA testa za kvantifikacijuN-proteina sa granicom detekcije u opsegu od ng/mL. Prose na vrednost LOD za prototipELISA testa za detekciju N-proteina je 9,2 ng/mL, dok je prose na vrednost LOQ10,2 ng/mL. Pokazali smo da su proizvedeni poliklonski antiserumi pogodni za detekcijuN-proteina sa sli nim ili boljim afinitetom i specifi noš u od komercijalnih antitela.Štaviše, prototip ELISA testa se može koristiti sa zadovoljavaju om pouzdanoš u zakvantifikaciju N-proteina u uzorcima bogatim proteinima, poput ljudskih seruma.The accurate diagnosis of people with suspected infection with the SARS-CoV-2 isessential to curb the global spread of COVID-19. The presence of SARS-CoV-2 can bedetected by RT-PCR (it detects RNA of the virus) or by the presence of viral antigens inbiological fluids in ELISA or similar techniques using antibodies developed in animals.The aim of the study was the establishment of a quantitative polyclonal sera-based test forroutine measurement of the concentration of SARS CoV-2 nucleocapsid protein usingabsorbance measurement in a standard 96-well microtiter plate. For the purposes of the testdevelopment, recombinant N protein was produced and used for the production of miceand rabbit antisera. Produced antisera were purified and titer was determined. High-affinitypolyclonal N-protein specific antisera were used for N-protein specific ELISA testdevelopment. The test is based on mice polyclonal sera adhered to microtiter plate bottomfor the capture of the N protein from the specimen. Various concentrations of therecombinant N-protein were used to generate a standard curve for protein quantification.The N-protein bound to the mice antibodies was detected with rabbit polyclonal sera andanti-rabbit antibody coupled to an enzyme that provides spectrophotometric measurement.We have successfully developed the prototype ELISA for the quantification of N-proteinwith the detection limit being in the range of ng/mL. The average LOD value for theprototype ELISA was determined to be 9.2 ng/mL, while the average LOQ value was10.2 ng/mL. We have demonstrated that produced polyclonal antisera are suitable for thedetection of N-protein with affinity and specificity similar to, or better than commercialantibodies. Furthermore, the prototype ELISA can be used with satisfactory confidence forquantification of the N-protein in protein-rich samples, similar to human sera.Abstract: [https://cherry.chem.bg.ac.rs/handle/123456789/5361

Development of SARS-CoV-2 N-protein specific capture ELISA

Ta na dijagnoza ljudi sa sumnjom na infekciju SARS-CoV-2 je od suštinskog zna aja za suzbijanje globalnog širenja COVID-19. Prisustvo SARS-CoV-2 može se otkriti RT-PCRom (otkriva RNK virusa) ili detekcijom prisustva virusnih antigena u biološkim te nostima ELISA-om ili sli nom tehnikom koje koriste antitela razvijena u životinjama. Cilj studije je bio uspostavljanje kvantitativnog testa koji se zasniva na koriš enju poliklonskih seruma za rutinsko odre ivanje koncentracije SARS-CoV-2 nukleokapsidnog proteina merenjam apsorbancije u standardnoj mikrotitarskoj plo ici sa 96 bunara. Za potrebe razvoja testa proizveden je rekombinantni N-protein i koriš en za proizvodnju antiseruma u miševima i ze evima. Proizvedeni antiserumi su pre iš eni i odre en im je titar. Poliklonskiantiserumi visokog afiniteta specifi ni za N-protein koriš eni su za razvoj ELISA testa specifi nog za ovaj protein. Test se zasniva na koriš enju poliklonskih seruma miševa koji su adherirani na dno bunara mikrotitarske plo ice za hvatanje N-proteina iz uzorka. Razli ite koncentracije rekombinantnog N-proteina su koriš ene za standardnu krivu za kvantifikaciju proteina. N-protein vezan za antitela miševa je detektovan ze jim poliklonskim serumom i anti-ze jim antitelom povezanim sa enzimom koji obezbe uje spektrofotometrijsko merenje. Uspešno smo razvili prototip ELISA testa za kvantifikaciju N-proteina sa granicom detekcije u opsegu od ng/mL. Prose na vrednost LOD za prototip ELISA testa za detekciju N-proteina je 9,2 ng/mL, dok je prose na vrednost LOQ 10,2 ng/mL. Pokazali smo da su proizvedeni poliklonski antiserumi pogodni za detekciju N-proteina sa sli nim ili boljim afinitetom i specifi noš u od komercijalnih antitela. Štaviše, prototip ELISA testa se može koristiti sa zadovoljavaju om pouzdanoš u za kvantifikaciju N-proteina u uzorcima bogatim proteinima, poput ljudskih seruma.The accurate diagnosis of people with suspected infection with the SARS-CoV-2 is essential to curb the global spread of COVID-19. The presence of SARS-CoV-2 can be detected by RT-PCR (it detects RNA of the virus) or by the presence of viral antigens in biological fluids in ELISA or similar techniques using antibodies developed in animals. The aim of the study was the establishment of a quantitative polyclonal sera-based test for routine measurement of the concentration of SARS CoV-2 nucleocapsid protein using absorbance measurement in a standard 96-well microtiter plate. For the purposes of the test development, recombinant N protein was produced and used for the production of mice and rabbit antisera. Produced antisera were purified and titer was determined. High-affinity polyclonal N-protein specific antisera were used for N-protein specific ELISA test development. The test is based on mice polyclonal sera adhered to microtiter plate bottom for the capture of the N protein from the specimen. Various concentrations of the recombinant N-protein were used to generate a standard curve for protein quantification. The N-protein bound to the mice antibodies was detected with rabbit polyclonal sera and anti-rabbit antibody coupled to an enzyme that provides spectrophotometric measurement. We have successfully developed the prototype ELISA for the quantification of N-protein with the detection limit being in the range of ng/mL. The average LOD value for the prototype ELISA was determined to be 9.2 ng/mL, while the average LOQ value was 10.2 ng/mL. We have demonstrated that produced polyclonal antisera are suitable for the detection of N-protein with affinity and specificity similar to, or better than commercial antibodies. Furthermore, the prototype ELISA can be used with satisfactory confidence for quantification of the N-protein in protein-rich samples, similar to human sera.Poster: [https://cherry.chem.bg.ac.rs/handle/123456789/5362

Chemical Defence in a Millipede: Evaluation and Characterization of Antimicrobial Activity of the Defensive Secretion from Pachyiulus hungaricus (Karsch, 1881) (Diplopoda, Julida, Julidae)

The chemical defence of the millipede Pachyiulus hungaricus is reported in the present paper, in which a chemical characterization is given and antimicrobial activity is determined. In total, independently of sex, 44 compounds were identified. All compounds belong to two groups: quinones and pentyl and hexyl esters of long-chain fatty acids. The relative abundances of quinones and non-quinones were 94.7% vs. 5.3% (males) and 87.3% vs. 12.7% (females), respectively. The two dominant quinones in both sexes were 2-methyl-1,4,-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone. Antibacterial and antifungal activity of the defensive secretion was evaluated in vitro against seven bacterial strains and eight fungal species. With the aid of a dilution technique, the antimicrobial potential of the secretion and high sensitivity of all tested strains were confirmed. The lowest minimum concentrations of these compounds (0.20-0.25 mg/mL) were sufficient for inhibition of Aeromonas hydrophila, Listeria monocytogenes and Methicillin resistant Staphylococcus aureus (MRSA). The growth of eight tested fungal species was inhibited by slightly lower concentrations of the secretion, with Fusarium equisetias the most sensitive fungus and Aspergillus flavus as the most resistant. Values of MIC and MFC in the employed microdilution assay ranged from 0.10 to above 0.35 mg/m L. The given extract contains antimicrobial components potentially useful as therapeutic agents in the pharmaceutical and agricultural industries

Anti-quorum sensing activity, toxicity in zebrafish (Danio rerio) embryos and phytochemical characterization of Trapa natans leaf extracts

Ethnopharmacological relevance: Trapa natans L. (water chestnut or water caltrop) is a widespread aquatic plant, which has been cultivated for food and traditional medicine since ancient times. Pharmacological studies showed that water chestnut exhibits the wide range of biological activities, such as antimicrobial, antioxidative, analgesic, anti-inflammatory, as well as antiulcer. Aim of the study: Evaluation of anti-virulence potential and toxicity of T. natans methanol (TnM), acetone (TnA) and ethyl acetate (TnEA) leaf extracts. Materials and methods: The anti-quorum sensing activity of Tn extracts was addressed by measuring their effects on biofilm formation, swarming motility and pyocyanin and elastase production in Pseudomonas aeruginosa. Specific P. aeruginosa biosensors were used to identify which of the signaling pathways were affected. The lethal and developmental toxicity of extracts were addressed in vivo using the zebrafish (Danio rerio) model system. The phenolic composition of T. natans leafs extracts was analyzed by a linear ion trap-OrbiTrap hybrid mass spectrometer (LTQ OrbiTrapMS) and UHPLC system configured with a diode array detector (DAD) hyphenated with the triple quadrupole mass spectrometer. Results: Subinhibitory concentrations of Tn leaf extracts (0.2 MIC) inhibited pyocyanin and elastase production up to 50% and 60%, respectively, and reduced swarming zones, comparing to non-treated P. aeruginosa. TnA inhibited biofilm formation by 15%, TnM showed a stimulatory effect on biofilm formation up to 20%, while TnEA showed no effect. The bioactive concentrations of TnM and TnA were not toxic in the zebrafish model system. Twenty-two phenolic compounds were tentatively identified in TnM, where thirteen of them were identified in T. natans for the first time. Tn extracts, as well as their major components, ellagic and ferulic acids, demonstrated the ability to interfere with P. aeruginosa Las and PQS signaling pathways. Conclusions: This study demonstrates anti-virulence potential of Tn leaf extracts against medically important pathogen P. aeruginosa and confirms the ethnopharmacological application of this plant against microbial infections.Peer-reviewed manuscript: [http://cherry.chem.bg.ac.rs/handle/123456789/2932]Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/2933

Propolis ethanolic extracts reduce adenosine diphosphate induced platelet aggregation determined on whole blood

Abstract Background Propolis is a well-known bee product containing more than 2000 identified compounds. It has many beneficial effects on human health that include antibacterial, antiviral, anticancer and hepatoprotective justifying its use as a dietary supplement. Platelet aggregation plays crucial role in thrombus formation that can cause stroke or heart attacks. As cardiovascular diseases, including those caused by thrombus formation, are related to 50% of deaths of Western population, the objective of this study was to determine antiaggregatory activity of propolis on platelet aggregation on the whole blood samples. Methods Twenty one propolis samples from Southeast Europe were characterized by spectrophotometric methods to determine content of the total flavonoids and phenolic acids. High performance liquid chromatography coupled with diode array detection was used to identify and quantify individual polyphenols. Platelet aggregation was tested by impedance aggregometry on the whole blood samples of ten healthy volunteers. Results The mean content of total polyphenols was 136.14 mg/g and ranged from 59.23 to 277.39 mg/g. Content of total flavonoids ranged between 6.83 and 55.44 mg/g with the mean value of 19.28 mg/g. Percentage of total phenolic acids was in the range 8.79 to 45.67% (mean 26.63%). Minimal antiaggregatory concentration, representing the lowest concentration of propolis extract sample that can cause statistically significant reduction of aggregation, ranged from 5 μM to 10.4 mM. Samples of propolis with lower content of luteolin and higher content of pinocembrin-7-methyleter showed better antiplatelet activity i.e. lower values of minimal antiaggregatory concentration. Conclusions This is the first study that shows antiaggregatory potential of propolis ethanolic extracts on the whole blood samples in the low micromolar concentrations suggesting that propolis supplementation may influence platelet aggregation and consequently thrombus formation. Further in vivo studies are needed to confirm the beneficial effects in prevention of cardiovascular diseases