Ubiquity of ring structures in the control space of complex oscillators

The search for safe and effective anticancer therapies is one of the major challenges of the 21st century. The ineffective treatment of cancers, classified as civilization diseases, contributes to a decreased quality of life, health loss, and premature mortality in oncological patients. Many natural phytochemicals have anticancer potential. Pentacyclic triterpenoids, characterized by six- and five-membered ring structures, are one of the largest class of natural metabolites sourced from the plant kingdom. Among the known natural triterpenoids, we can distinguish lupane-, oleanane-, and ursane-types. Pentacyclic triterpenoids are known to have many biological activities, e.g., anti-inflammatory, antibacterial, hepatoprotective, immunomodulatory, antioxidant, and anticancer properties. Unfortunately, they are also characterized by poor water solubility and, hence, low bioavailability. These pharmacological properties may be improved by both introducing some modifications to their native structures and developing novel delivery systems based on the latest nanotechnological achievements. The development of nanocarrier-delivery systems is aimed at increasing the transport capacity of bioactive compounds by enhancing their solubility, bioavailability, stability in vivo and ensuring tumor-targeting while their toxicity and risk of side effects are significantly reduced. Nanocarriers may vary in sizes, constituents, shapes, and surface properties, all of which affect the ultimate efficacy and safety of a given anticancer therapy, as presented in this review. The presented results demonstrate the high antitumor potential of systems for delivery of pentacyclic triterpenoids.

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Unprecedented Reactivity of γ‐Amino Cyclopentenone Enables Diversity‐Oriented Access to Functionalized Indoles and Indole‐Annulated Ring Structures

Angewandte Chemie International Edition ◽

10.1002/anie.202016015 ◽

2021 ◽

Vol 60 (16) ◽

pp. 8808-8812

Author(s):

Chenna Jagadeesh ◽

Biplab Mondal ◽

Sourav Pramanik ◽

Dinabandhu Das ◽

Jaideep Saha

Keyword(s):

Ring Structures

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A plant endophyte Staphylococcus hominis strain MBL_AB63 produces a novel lantibiotic, homicorcin and a position one variant

Scientific Reports ◽

10.1038/s41598-021-90613-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

M. Aftab Uddin ◽

Shammi Akter ◽

Mahbuba Ferdous ◽

Badrul Haidar ◽

Al Amin ◽

...

Keyword(s):

Gene Clusters ◽

Antimicrobial Activities ◽

Whole Genome Sequence ◽

Antimicrobial Substances ◽

The Core ◽

Rp Hplc ◽

Ring Structures ◽

Core Peptide ◽

Staphylococcus Hominis ◽

Epilancin 15X

AbstractHere we report a jute endophyte Staphylococcus hominis strain MBL_AB63 isolated from jute seeds which showed promising antimicrobial activity against Staphylococcus aureus SG511 when screening for antimicrobial substances. The whole genome sequence of this strain, annotated using BAGEL4 and antiSMASH 5.0 to predict the gene clusters for antimicrobial substances identified a novel antimicrobial peptide cluster that belongs to the class I lantibiotic group. The predicted lantibiotic (homicorcin) was found to be 82% similar to a reported peptide epicidin 280 having a difference of seven amino acids at several positions of the core peptide. Two distinct peaks obtained at close retention times from a RP-HPLC purified fraction have comparable antimicrobial activities and LC–MS revealed the molecular mass of these peaks to be 3046.5 and 3043.2 Da. The presence of an oxidoreductase (homO) similar to that of epicidin 280- associated eciO or epilancin 15X- associated elxO in the homicorcin gene cluster is predicted to be responsible for the reduction of the first dehydrated residue dehydroalanine (Dha) to 2-hydroxypropionate that causes an increase of 3 Da mass of homicorcin 1. Trypsin digestion of the core peptide and its variant followed by ESI–MS analysis suggests the presence of three ring structures, one in the N-terminal and other two interlocking rings at the C-terminal region that remain undigested. Homicorcin exerts bactericidal activity against susceptible cells by disrupting the integrity of the cytoplasmic membrane through pore formation as observed under FE-SEM.

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Quantum dots to double concentric quantum ring structures transition

physica status solidi (c) ◽

10.1002/pssc.200880616 ◽

2009 ◽

Vol 6 (4) ◽

pp. 928-931 ◽

Cited By ~ 4

Author(s):

S. Bietti ◽

C. Somaschini ◽

M. Abbarchi ◽

N. Koguchi ◽

S. Sanguinetti ◽

...

Keyword(s):

Quantum Dots ◽

Quantum Ring ◽

Ring Structures

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Squalene-Hopene Cyclases

Applied and Environmental Microbiology ◽

10.1128/aem.00300-11 ◽

2011 ◽

Vol 77 (12) ◽

pp. 3905-3915 ◽

Cited By ~ 78

Author(s):

Gabriele Siedenburg ◽

Dieter Jendrossek

Keyword(s):

Common Ancestor ◽

Amino Acid Sequences ◽

Enzymatic Reactions ◽

Covalent Bonds ◽

Content Type ◽

Oxidosqualene Cyclase ◽

Ring Structures ◽

One Step ◽

Alicyclobacillus Acidocaldarius ◽

Eukaryotic Organisms

ABSTRACTHopanoids and sterols are members of a large group of cyclic triterpenoic compounds that have important functions in many prokaryotic and eukaryotic organisms. They are biochemically synthesized from linear precursors (squalene, 2,3-oxidosqualene) in only one enzymatic step that is catalyzed by squalene-hopene cyclase (SHC) or oxidosqualene cyclase (OSC). SHCs and OSCs are related in amino acid sequences and probably are derived from a common ancestor. The SHC reaction requires the formation of five ring structures, 13 covalent bonds, and nine stereo centers and therefore is one of the most complex one-step enzymatic reactions. We summarize the knowledge of the properties of triterpene cyclases and details of the reaction mechanism ofAlicyclobacillus acidocaldariusSHC. Properties of other SHCs are included.

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Miniature UWB Filter Using Three-Quarters Wavelength Resonator with Direct-Connected Feed Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.571.721 ◽

2012 ◽

Vol 571 ◽

pp. 721-724

Author(s):

Cai Peng

Keyword(s):

Transmission Lines ◽

Linear Structure ◽

Ultra Wideband ◽

Input Output ◽

Transmission Zeros ◽

Full Wave ◽

Quarter Wavelength ◽

Ring Structures ◽

Loss Characteristic ◽

Better Than

A miniature ultra-wideband (UWB) bandpass filter using three-quarters wavelength resonators is presented in this paper. Direct-connected feed method is employed between the input/output ports and the resonators in order to overcome the shortcomings due to the gap-coupled feed method and produce two transmission zeros in the lower and upper stopbands. On the other hand, two quarter-wavelength matching transmission lines are introduced to the input/output ports to improve the reflection loss characteristic in the passband of the filter. In addition, the resonators are folded to be open ring structures, which are more miniaturized than the conventional linear structure. As a consequence, the filter is compact in size and exhibits good performance. The filter is successfully realized in theory and verified by full wave EM simulation, and simulated frequency response results show that the fabricated filter has an insertion loss of better than 1dB in the passband and two rejections of greater than 25dB in most of the stopbands.

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