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Topic Review
Pi-Stacking
In chemistry, pi stacking (also called π–π stacking) refers to the presumptive attractive, noncovalent interactions (orbital overlap) between the pi bonds of aromatic rings. However this is a misleading description of the phenomena since direct stacking of aromatic rings (the "sandwich interaction") is electrostatically repulsive. What is more commonly observed (see figure to the right) is either a staggered stacking (parallel displaced) or pi-teeing (perpendicular T-shaped) interaction both of which are electrostatic attractive For example, the most commonly observed interactions between aromatic rings of amino acid residues in proteins is a stagered stacked followed by a perpendular orientation. Sandwiched orientations are relatively rare. Pi stacking is repulsive as it places carbon atoms with partial negative charges from one ring on top of other partial negatively charged carbon atoms from the second ring and hydrogen atoms with partial postive charges on top of other hydrogen atoms that likewise carry partial positive charges. In staggered stacking, one of the two aromatic rings is offset sideways so that the carbon atoms with partial negative charge in the first ring are placed above hydrogen atoms with partial positive charge in the second ring so that the electrostatic interactions become attractive. Likewise, pi-teeing interactions in which the two rings are oriented perpendicultar to either other is electrostatically attractive as it places partial postively charged hydrogen atoms in close proximity to partially negatively charged carbon atoms. An alternative explanation for the preference for staggered stacking is due to the balance between van der Waals interactions (attractive dispersion plus Pauli repulsion). These staggered stacking and π-teeing interactions between aromatic rings are important in nucleobase stacking within DNA and RNA molecules, protein folding, template-directed synthesis, materials science, and molecular recognition. Despite the wide use of term pi stacking in the scientific literature, there is no theoretical justification for its use.
  • 12.9K
  • 12 Oct 2022
Topic Review
PI- based Optical Chemosensors
Perylene imide (PI) molecules and materials have been extensively studied for optical chemical sensors, particularly those based on fluorescence and colorimetric mode, taking advantage of the unique features of PIs such as structure tunability, good thermal, optical and chemical stability, strong electron affinity, strong visible light absorption and high fluorescence quantum yield. PIs-based optical chemosensors have now found broad applications in gas phase detection of chemicals, including explosives, biomarkers of some food and diseases (such as organic amines (alkylamines and aromatic amines)), benzene homologs, organic peroxides, phenols and nitroaromatics, etc.
  • 505
  • 12 Jan 2021
Topic Review
Phytotoxic Metabolites and Fungi of Grapevine Trunk Diseases
Grapevines are one of the most economically important crops worldwide, with approximately 48% of the world’s grape production used for wine production. Fungal diseases are limiting factors to the production of wine grapes, impacting the quality of wine. Grapevine trunk diseases (GTDs), caused by one or several fungal pathogens, cause a progressive decline in vines resulting in a loss in productivity and eventual death of the vines. Internal and external GTDs symptoms sometimes take several years to appear after infection; thus, they are considered slow-progression diseases.
  • 636
  • 16 Jan 2023
Topic Review
Phytosynthesized Metallic Nanoparticles
Phytosynthesized nanoparticles represent a continuously increasing field of research, with numerous studies published each year. However, with the emerging interest in this area, the quality of the published works is also continuously increasing, switching from routine antioxidant or antimicrobial studies on trivial microbial lines to antibiotic-resistant strains or antitumoral studies. However, this increasing interest has not been not reflected in the studies regarding the toxicological effects of nanoparticles (NPs); this should be a subject of greatest interest, as the increasing administration of NPs in general (and phytosynthesized NPs in particular) could lead to their accumulation in the environment (soil, water and living organisms).
  • 496
  • 21 Sep 2022
Topic Review
Phytochemicals Used for Hair Dyeing
Natural dyes have been used since ancient times, when they were used not only for hair coloration, but also for medicinal, decoration and religious purposes. Many organic compounds have been identified as the principal coloring matters in hair dye plants and investigated for dyeing performance under experimental conditions. Natural colorants can be classified based on dye source, application method and chemical structure.
  • 1.6K
  • 23 Nov 2022
Topic Review
Phytochemicals of the Genus Maytenus
The genus Maytenus is a member of the Celastraceae family, of which several species have long been used in traditional medicine. Between 1976 and 2021, nearly 270 new compounds have been isolated and elucidated from the genus Maytenus. Among these, maytansine and its homologues are extremely rare in nature. Owing to its unique skeleton and remarkable bioactivities, maytansine has attracted many synthetic endeavors in order to construct its core structure.
  • 649
  • 09 Aug 2021
Topic Review
Phytochemicals
 The bioactive chemical compounds responsible for these benefits are known as phytochemicals (PHYs). Specifically, PHYs are defined as bioactive chemical compounds found in plants, such as fruits, vegetables, grains, and other plant-derived foods, that may supply health benefits beyond basic nutrition and could help to reduce the risk of major chronic diseases. PHYs are generally produced by plants to help themselves resist fungi, bacteria, and plant virus infections and also to hamper their consumption by insects and other animals
  • 372
  • 08 Sep 2023
Topic Review
Phytocannabinoids, Endocannabinoids and Synthetic Cannabinoids
Generally, the term ‘cannabinoids’ refers to a heterogeneous family of compounds that exhibit activity upon particular human cannabinoid receptors, namely CB1 and CB2. They encompass the natural compounds present in the Cannabis plants, lipid mediators called ECs naturally produced by human cells, as well as by all vertebrates on planet Earth, and the synthetic analogs of both groups designed by scientist, called SCs.
  • 511
  • 01 Sep 2023
Topic Review
Physiochemical Properties of Silver Nanomaterials
Over the last decades, there has been tremendous volume of research efforts focussed on engineering silver based (nano)materials. The interest in silver has been mostly driven by the element capacity to kill pathogenic bacteria. In this context the main area of application has been medical devices that are at significant risk of becoming colonised by bacteria and infected. However, silver nanomaterials have been incorporated in a number of other commercial products which may or may not benefit from antibacterial protection. The rapid expansion of the library and their use raises important questions about possible toxicity and generally human health.
  • 1.1K
  • 28 Oct 2020
Topic Review
Physicochemistry of Deep Eutectic Solvents
Deep eutectic solvents (DESs), considered as one of the greenest families of solvents, are used in many fields, such as organic synthesis, (bio)catalysis, electrochemistry, and (bio)medicine.
  • 497
  • 17 May 2023
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