Pectic polysaccharides during ripening of mango (Mangifera indica L)

The content of pectin decreased from 2.0 to 0.7% fresh weight (FW) and there was a concomitant increase in free galacturonic acid from 36 to 168 mg% FW during ripening of mango. Ion exchange chromatography on DEAE/cellulose resolved the pectic fraction into seven distinct peaks, with all of them showing a drastic decrease in pectin content and molecular weight as fruit ripening progressed, which indicated significant depolymerisation in vivo. Fraction I appeared to be an arabinogalactan‐type polymer, while fractions II and III were heterogalacturonans containing more than 60% galacturonic acid. Hydrolases implicated in pectin depolymerisation were polygalacturonase (PG), pectin methyl esterase (PME), galactanase, arabinanase and β ‐galactosidase. They all showed a climacteric peak in activity during ripening, except for PME which showed a continuous decrease in activity after an initial increase. These results are discussed in the light of fruit softening during ripening. Copyright © 2003 Society of Chemical Industry     

Standardisation of water-moderated 241Am-Be neutron source using De Pangher neutron long counter: experimental and Monte Carlo modelling

A convenient neutron source is made for calibration of neutron survey instruments and personal dosimeters that are used in various nuclear installations such as fuel reprocessing, waste management, fuel fabrication and oil and well logging facilities, etc. This source consists of a bare (241)Am-Be neutron source placed at the centre of a 15-cm radius stainless steel spherical shell filled with distilled water. This paper describes the standardisation of the source at Bhabha Atomic Research Centre, using De Pangher neutron long counter both experimentally and using the Monte Carlo simulation. The ratio of neutron yield of water moderated to the bare (241)Am-Be neutron source was found to be 0.573. From the simulation, the neutron-fluence-weighted average energy of water-moderated (241)Am-Be source (fluence-weighted average energy of 2.25 MeV, dose-weighted average energy of 3.55 MeV) was found to be nearly the same as that of a (252)Cf source (fluence-weighted average energy of 2.1 MeV, dose-weighted average energy of 2.3 MeV). This source can be used for calibration in addition to (252)Cf, to study the variation in response of neutron monitoring instruments.     

Design of multifunctionalized piperazine polymer and its activity toward pathogenic microorganisms

The study intends to design a simple and powerful synthesis of piperazine-methacrylate monomer and its homopolymer. The synthesized piperazine-methacrylate monomer was polymerized by solution polymerization technique in the presence of free-radical initiator azobis(2-methylpropionitrile) resulting in the formation of multifunctionalized piperazine polymer. The structural investigation was done by FTIR and NMR (¹H and ¹³C NMR). The thermal properties and degradation of the polymer were examined by DSC and TGA techniques. The polymer exhibited glass transition temperature (T_g) at 88.4 °C. The polymer surface was found to be soft and nonporous which was examined by FESEM. The synthesized polymeric compound exhibited good antimicrobial activity against Gram-negative bacterium Escherichia coli, tubercular variant Mycobacterium smegmatis, and Gram-positive bacterium Staphylococcus aureus with a zone of inhibition at a range of 15.60–19.33, 15.33–17, and 15.67–18 mm diameter, respectively. The polymer also showed good activity against fungus Candida albicans with a zone of inhibition at a range of 16.33–22 mm diameter. The percentage inhibition of microorganisms increased with increase in concentration (1.5–12 mg) which is carried out by optical density method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47521.     

Viscosity and thermal conductivity of ZnO–water-based nanofluids stabilized by grafted SMA-g-MPEG comb-shaped copolymer for heat transfer applications

Iranian Polymer Journal - In this work, the effect of poly(styrene-co-maleic anhydride)-grafted methoxy (polyethylene glycol) (SMA-g-MPEG) copolymer as dispersants on the viscosity and thermal...     

Synthesis and fabrication of high-potent antimicrobial polymeric ultrathin coatings

The development of antimicrobial coatings in various sectors is escalating nowadays. However, design, synthesis, and fabrication of simple antimicrobial polymer coatings with potent biocidal action against pathogenic microbes are necessary to emerge. The current article deals with fabrication of high efficient ultrathin coatings of synthesized polymer for controlling pathogenic bacteria and fungi. The article is intensified with simple synthesis, characterization, fabrication of ultrathin coatings and their antimicrobial studies. The polymer structure is elucidated by FTIR,¹HNMR, and ¹³CNMR, and the thermal properties are explained by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The antimicrobial activity of a polymer and their ultrathin coatings against Escherichia coli, Staphylococcus aureus, tubercular-variant Mycobacterium smegmatis, and Candida albicans are reported elaborately. The morphology of ultrathin coating and their interaction with microorganisms are studied using a scanning electron microscope and an atomic force microscope. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47893.     

Study of neutron spectra emitted by moderated 241Am-Be source for various moderating materials by using simulation technique

A study was done on the tailored neutron energy spectra of (241)Am-Be neutron source due to the effect of moderators. The (241)Am-Be laboratory neutron source was used as the basic source and the emitted spectrum was modified using various neutron moderators. The various moderators used are high-density polythene, light water, heavy water, graphite, (56)Fe, BeO, Be, (6)Li and (7)Li. The absolute energy spectra and fluences in each case are calculated by using the Monte Carlo code FLUKA. This paper describes the simulation work done to design a moderated (241)Am-Be neutron source to produce various energy neutron spectra.     

Quantitation of Acyclovir in Pharmaceutical Dosage forms using High-Performance Liquid Chromatography

A stability-indicating high performance liquid chromatography method for the quantitation of acyclovir in pharmaceutical dosage forms (capsules, ointment and injection) has been developed. The method is accurate and precise with a percent relative standard deviation of 1.2 based on 5 readings. The excipients present in the dosage forms did not interfere with the assay method. The recovery from the synthetic mixtures was quantitative. The samples decomposed under drastic conditions showed a new peak in the chromatogram. Acyclovir appears to be more stable in the alkaline than in the acidic solution. There appears to be a distribution/decomposition problem with the ointment sample being marketed in certain types of tubes used previously and still on the market.     

Anatomical and molecular design of the Drosophila antenna as a flagellar auditory organ

The molecular basis of hearing is less well understood than many other senses. However, recent studies in Drosophila have provided some important steps towards a molecular understanding of hearing. In this report, we summarize these findings and their implications on the relationship between hearing and touch. In Drosophila, hearing is accomplished by Johnston's Organ, a chordotonal organ containing over 150 scolopidia within the second antennal segment. We will discuss anatomical features of the antenna and how they contribute to the function of this flagellar auditory receptor. The effects of several mutants, identified through mutagenesis screens or as homologues of vertebrate auditory genes, will be summarized. Based on evidence gathered from these studies, we propose a speculative model for how the chordotonal organ might function.     

Influence of Linker Length on Conformational Preferences of Glycosylated Sugar Amino Acid Foldamers

Glycosylation of foldamers derived from furanoid sugar amino acids with mannose and a propyltriazole linker results in an unprecedented 16/10 mixed‐turn structure in the glycopeptides in water, with a preference for the higher‐order structure irrespective of the stereochemistry of the starting foldamer. This is in stark contrast to the structures displayed by the same oligomers in water when mannosylated with a two‐carbon‐shorter methyltriazole linker: 16‐membered turn structure in the cis‐foldamer and 10‐membered in its trans congener. This demonstrates the defining influence of the linker length on the structural preference of these novel glycopeptide mimics.     

An ultra-high performance chromatographic method for the determination of artemisinin

Objective: The goal of this study is to develop an ultra-high performance liquid chromatographic method for the quantitative determination of artemisinin at very low concentrations using selective ion mass spectroscopic detection.

Materials and methods: Separation was conducted using a C4 100?mm×?2.1?mm column, and the mobile phase consisted of an isocratic two-component system consisting of 60% of a 0.1% aqueous solution of formic acid and 40% acetonitrile at a flow rate of 0.4?ml/min. The drug was detected by means of an electrospray mass spectrometer with selective ion monitoring of the [M-H₂O+H]⁺ with m/z of 265.3 in positive ion mode.

Results: The calibration curves of artemisinin obtained from the UPLC/MS system were linear in the three ranges analyzed, with a correlation coefficient of no less than 0.9996 for all sets of standards. The peak tailing factor for all measurements were ≤1.7. The method proved to have good repeatability and linearity.

Discussion: The described analytical method reached a LOQ of 0.010?µg/ml with an isocratic system and enables an analysis rate of 20 samples per hour. The linearity of the standards was excellent for all sets of standards analyzed.

Conclusion: The method presented in this study provides a rapid and suitable means for the determination of artemisinin at very low concentrations. This is especially significant when performing dissolution studies where, due to the low solubility of artemisinin, a method that can measure the drug at nanogram levels is necessary.