Nanostructured material-based optical and electrochemical detection of amoxicillin antibiotic

The penicillin derivative amoxicillin (AMX) plays an important role in treating various types of infections caused by bacteria. However, excessive use of AMX may have negative health effects. Therefore, it is of utmost importance to detect and quantify the AMX in pharmaceutical drugs, biological fluids, and environmental samples with high sensitivity. Therefore, this review article provides valuable and up-to-date information on nanostructured material-based optical and electrochemical sensors to detect AMX in various biological and chemical samples. The role of using different nanostructured materials on the performance of important optical sensors such as colorimetric sensors, fluorescence sensors, surface-enhanced Raman scattering sensors, chemiluminescence/electroluminescence sensors, optical immunosensors, optical fibre-based sensors, and several important electrochemical sensors based on different electrode types have been discussed. Moreover, nanocomposites, polymer, and MXenes-based electrochemical sensors have also been discussed, in which such materials are being used to further enhance the sensitivity of these sensors. Furthermore, nanocomposite-based photo-electrochemical sensors and the market availability of biosensors including AMX have also been discussed briefly. Finally, the conclusion, challenges, and future perspectives of the above-mentioned sensing techniques for AMX detection are presented.     

Aluminum Toxicity: A Case Study on Tobacco (<i>Nicotiana tabacum</i> L.)

Aluminum is an abundant metal in the earth’s crust that turns out to be toxic in acidic environments. Many plants are affected by the presence of aluminum at the whole plant level, at the organ level, and at the cellular level. Tobacco as a cash crop (Nicotiana tabacum L.) is a widely cultivated plant worldwide and is also a good model organism for research. Although there are many articles on Al-phytotoxicity in the literature, reviews on a single species that are economically and scientifically important are limited. In this article, we not only provide the biology associated with tobacco Al-toxicity, but also some essential information regarding the effects of this metal on other plant species (even animals). This review provides information on aluminum localization and uptake process by different staining techniques, as well as the effects of its toxicity at different compartment levels and the physiological consequences derived from them. In addition, molecular studies in recent years have reported specific responses to Al toxicity, such as overexpression of various protective proteins. Besides, this review discusses data on various organelle-based responses, cell death, and other mechanisms, data on tobacco plants and other kingdoms relevant to these studies.     

Synthesis,Biological Evaluation,and Molecular Modeling Studies of New 1,3,4-Thiadiazole Derivatives as Potent Antimicrobial Agents

In this work, the synthesis, characterization, and biological activities of a new series of 1,3,4-thiadiazole derivatives were investigated. The structures of final compounds were identified using ¹H-NMR, ¹³C-NMR, elemental analysis, and HRMS. All the new synthesized compounds were then screened for their antimicrobial activity against four types of pathogenic bacteria and one fungal strain, by application of the MIC assays, using Ampicilin, Gentamycin, Vancomycin, and Fluconazole as standards. Among the compounds, the MIC values of 4 and 8 μg/mL of the compounds 3f and 3g , respectively, are remarkable and indicate that these compounds are good candidates for antifungal activity. The docking experiments were used to identify the binding forms of produced ligands with sterol 14-demethylase to acquire insight into relevant proteins. The MD performed about 100 ns simulations to validate selected compounds’ theoretical studies. Finally, using density functional theory (DFT) to predict reactivity, the chemical characteristics and quantum factors of synthesized compounds were computed. These results were then correlated with the experimental data. Furthermore, computational estimation was performed to predict the ADME properties of the most active compound 3f .     

ELECTRON MICROSCOPIC STUDIES ON THE INDIRECT FLIGHT MUSCLES OFDROSOPHILAMELANOGASTER : II. Differentiation of Myofibrils

The differentiation of the indirect flight muscles was studied in the various pupal stages of Drosophila. Fibrillar material originates in the young basophilic myoblasts in the form of short myofilamants distributed irregularly near the cell membranes. The filaments later become grouped into bundles (fibrils). Certain "Z bodies" appear to be important during this process. The "Z bodies" may possibly be centriolar derivatives and are the precursors of the Z bands. The first formed fibrils (having about 30 thick myofilaments) are already divided into sarcomeres by Z bands. These sarcomeres, however, seem to be shorter than those of the adult fibrils.The H band differentiates in fibrils having about 40 thick myofilaments; the fibrils constrict in the middle of each sarcomere during this process. The individual myofibrils increase from about 0.3 µ to 1.5 µ in diameter during development, apparently by addition of new filaments on the periphery of the fibrils. The ribosomes seem to be the only cytoplasmic inclusions which are closely associated with these growing myofibrils. Disintegration of the plasma membranes limiting individual myoblasts was commonly seen during development of flight muscles, supporting the view that the multinuclear condition of the fibers of these muscles is due to fusion of myoblasts.     

Crystal structure of cod liver class I alcohol dehydrogenase: substrate pocket and structurally variable segments.

The structural framework of cod liver alcohol dehydrogenase is similar to that of horse and human alcohol dehydrogenases. In contrast, the substrate pocket differs significantly, and main differences are located in three loops. Nevertheless, the substrate pocket is hydrophobic like that of the mammalian class I enzymes and has a similar topography in spite of many main-chain and side-chain differences. The structural framework of alcohol dehydrogenase is also present in a number of related enzymes like glucose dehydrogenase and quinone oxidoreductase. These enzymes have completely different substrate specificity, but also for these enzymes, the corresponding loops of the substrate pocket have significantly different structures. The domains of the two subunits in the crystals of the cod enzyme further differ by a rotation of the catalytic domains by about 6 degrees. In one subunit, they close around the coenzyme similarly as in coenzyme complexes of the horse enzyme, but form a more open cleft in the other subunit, similar to the situation in coenzyme-free structures of the horse enzyme. The proton relay system differs from the mammalian class I alcohol dehydrogenases. His 51, which has been implicated in mammalian enzymes to be important for proton transfer from the buried active site to the surface is not present in the cod enzyme. A tyrosine in the corresponding position is turned into the substrate pocket and a water molecule occupies the same position in space as the His side chain, forming a shorter proton relay system.     

Efficacy of foliar extracts against pre- and post-harvest diseases of sponge-gourd fruits

S.K. AHMAD AND J.S. PRASAD. 1995. The inhibitory potential of aqueous foliar extracts of Adhatoda vasica, Azadirachta indica, Catharanthes roseus, Datura fistulosa, Lantana camara, Muraya exotica, Ocimum sanctum, Ricinus communis and Strychnos nux-vomica were evaluated against soft rot diseases of sponge-gourd fruits caused by Helminthosporium spiciferum and Fusarium scirpi. Conidial germination of F. scirpi and H. spiciferum were reduced to about 75% when their spores were treated with A. indica, C. roseus, D. fistulosa, L. camara, M. exotica and O. sanctum. Considerable reductions (50%) in mycelial dry weights and colony diameters were recorded in liquid media containing (20%) aqueous extracts of C. roseus, D. fistulosa and M. exotica . Other extracts reduced the mycelial growth but to a lesser extent. Post-infection treatment of sponge-gourd fruits with the extracts of A. indica, L. camara, M. exotica, O. sanctum, D. fistulosa and C. roseus almost fully inhibited the spread of disease. Treatment of fruits with A. indica and C. roseus before fungal infection reduced the spread of disease caused by both the pathogens, whereas M. exotica, O. sanctum and D. fistulosa reduced the spread of soft-rot caused by F. scirpi but not by H. spiciferum .     

Three-dimensional structure prediction of the NAD binding site of proton-pumping transhydrogenase from Escherichia coli

A three-dimensional structure of the NAD site of Escerichia coli transhydrogenase has been predicted. The model is based on analysis of conserved residues among the transhydrogenases from five different sources, homologies with enzymes using NAD as cofactors or substrates, hydrophilicity profiles, and secondary structure predictions. The present model supports the hypothesis that there is one binding site, located relatively close to the N-terminus of the α-subunit. The proposed structure spans residues α145 to α287, and it includes five β-strands and five α-helices oriented in a typical open twisted α/β conformation. The amino acid sequence following the GXGXXG dinucleotide binding consensus sequence (residues α172 to α177) correlates exactly to a typical fingerprint region for ADP binding βαβ folds in dinucleotide binding enzymes. In the model, aspartic acid α195 forms hydrogen bonds to one or both hydroxyl groups on the adenosine ribose sugar moiety. Threonine α196 and alanine α256, located at the end of βB and βD, respectively, create a hydrophobic sandwich with the adenine part of NAD buried inside. The nicotinamide part is located in a hydrophobic cleft between αA and βE. Mutagenesis work has been carried out in order to test the predicted model and to determine whether residues within this domain are important for proton pumping directly. All data support the predicted structure, and no residue crucial for proton pumping Was detected. Since no three-dimensional structure of transhydrogenase has been solved, a well based tertiary structure prediction is of great value for further experimental design in trying to elucidate the mechanism of the energy-linked proton pump. © 1995 Wiley-Liss, Inc.     

In situ CO2 gas-exchange in fruits of a tropical tree,Durio zibethinus Murray

We examined the in situ CO₂ gas-exchange of fruits of a tropical tree, Durio zibethinus Murray, growing in an experimental field station of the Universiti Pertanian Malaysia. Day and night dark respiration rates were exponentially related to air temperature. The temperature dependent dark respiration rate showed a clockwise loop as time progressed from morning to night, and the rate was higher in the daytime than at night. The gross photosynthetic rate was estimated by summing the rates of daytime dark respiration and net photosynthesis. Photosynthetic CO₂ refixation, which is defined as the ratio of gross photosynthetic rate to dark respiration rate in the daytime, ranged between 15 and 45%. The photosynthetic CO₂ refixation increased rapidly as the temperature increased in the lower range of air temperature T _c (T _c <28.5 °C), while it decreased gradually as the temperature increased in the higher range (T _c 28.5 °C). Light dependence of photosynthetic CO₂ refixation was approximated by a hyperbolic formula, where light saturation was achieved at 100 mol m^–2 s^–1 and the asymptotic CO₂ refixation was determined to be 37.4%. The estimated gross photosynthesis and dark respiration per day were 1.15 and 4.90 g CO₂ fruit^–1, respectively. Thus the CO₂ refixation reduced the respiration loss per day by 23%. The effect of fruit size on night respiration rate satisfied a power function, where the exponent was larger than unity.     

Application of protein-A indirect ELISA (PAI-ELISA) for the detection of anti-Smith antibodies in systemic lupus erythematosus patients

An indirect form of protein-A ELISA (PAI-ELISA) was optimized and, when used to detect anti-Smith antibodies in sera of 31 systemic lupus erythematosus (SLE) patients, gave results comparable with those using a commercial immunodiffusion kit. The number of sera found to be positive for anti-Smith antibodies by ELISA was seven, four of which were also found positive by immunodiffusion.B.O. Siti-Rohana is with the Universiti Kebangsaan Malaysia (UKM), Faculty of Medicine, Kuala Lumpur, Malaysia. I.B. Ahmad is with the Department of Microbiology, Faculty of Life Sciences, Universiti Kebangsaan Malaysia, Bangi, 43600 UKM, Malaysia; B.A. Nasaruddin is with the Institute for Medical Research, Malaysia.