Search results for "Heterocyclic compound"
showing 10 items of 382 documents
Surface-immobilized DNAzyme-type biocatalysis
2014
The structure of the double helix of deoxyribonucleic acid (DNA, also called duplex-DNA) was elucidated sixty years ago by Watson, Crick, Wilkins and Franklin. Since then, DNA has continued to hold a fascination for researchers in diverse fields including medicine and nanobiotechnology. Nature has indeed excelled in diversifying the use of DNA: beyond its canonical role of repository of genetic information, DNA could also act as a nanofactory able to perform some complex catalytic tasks in an enzyme-mimicking manner. The catalytic capability of DNA was termed DNAzyme; in this context, a peculiar DNA structure, a quadruple helix also named quadruplex-DNA, has recently garnered considerable i…
A surface hopping algorithm for nonadiabatic minimum energy path calculations
2015
The article introduces a robust algorithm for the computation of minimum energy paths transiting along regions of near-to or degeneracy of adiabatic states. The method facilitates studies of excited state reactivity involving weakly avoided crossings and conical intersections. Based on the analysis of the change in the multiconfigurational wave function the algorithm takes the decision whether the optimization should continue following the same electronic state or switch to a different state. This algorithm helps to overcome convergence difficulties near degeneracies. The implementation in the MOLCAS quantum chemistry package is discussed. To demonstrate the utility of the proposed procedur…
Deciphering the DNAzyme activity of multimeric quadruplexes: insights into their actual role in the telomerase activity evaluation assay.
2011
The end of human telomeres is comprised of a long G-rich single-stranded DNA (known as 3'-overhang) able to adopt an unusual three-dimensional "beads-on-the-string" organization made of consecutively stacked G-quadruplex units (so-called quadruplex multimers). It has been widely demonstrated that, upon interaction with hemin, discrete quadruplexes acquire peroxidase-mimicking properties, oxidizing several organic probes in H(2)O(2)-rich conditions; this property, known as DNAzyme, has found tens of applications in the last two decades. However, little is known about the DNAzyme activity of multimeric quadruplexes; this is an important question to address, especially in light of recent repor…
ChemInform Abstract: Aldol Reactions with Erythrulose Derivatives: Stereoselective Synthesis of Differentially Protected syn-α,β-Dihydroxy Esters.
2010
Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-α,β-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent.
Aldol Reactions with Erythrulose Derivatives: Stereoselective Synthesis of Differentially Protected syn -α,β-Dihydroxy Esters
2000
Boron enolates of 1-O-silylated erythrulose 3,4-acetonides prepared with Brown's chloro-dicyclohexylborane/tertiary amine system have been shown to react with achiral aldehydes in a highly stereoselective way to yield a 1,2-syn/1,3-syn stereoisomer. Through oxidative cleavage of the aldol adducts with periodic acid hydrate, enantiopure syn-α,β-dihydroxy esters with either hydroxyl group differently protected have been prepared. These erythrulose derivatives therefore behave as a chiral hydroxy acetate (glycolate) enolate equivalent.
Coumarins and Related Compounds from the Medicinal Plants of Africa
2013
Coumarins (1-benzopyran-2-one) are chemical compounds in the benzopyrone class of organic compounds found in many plants. Coumarins possess a variety of biological properties, including antimicrobial, antiviral, antiinflammatory, antidiabetic, antioxidant, and enzyme inhibitory activity. This chapter gives an overview of the isolation, structural features, and pharmacological actions of variety of coumarins produced by the African plants. The biosynthetic pathway of coumarins is also discussed in this chapter. We identify 117 coumarins in African plants, of which 48 are new. The pharmacological activities of 54 of these coumarins are reported and documented in this chapter.
Generator-based PET radiopharmaceuticals for molecular imaging of tumours: on the way to THERANOSTICS.
2011
Generator-derived radionuclides for PET/CT imaging are promising for optimizing targeted radiotherapy by an individual patient-based approach, applying pre-therapeutic evaluation, as well as dosimetric calculations, and for measuring treatment response after radionuclide therapy.
Alkaloids Isolated from Somatic Hybrid Cell Cultures of the Species CombinationRauwolfia serpentinaxrhazya stricta
1995
Abstract The phytochemical analyses of a somatic hybrid cell suspension culture of the genus and species combination Rauwolfia serpentina x Rhazya stricta revealed a number of monoterpenoid indole alkaloids. The alkaloids were identified as tubotaiwine, an isomeric mixture of vallesiachotamine, stemmadenine and vomilenine and were all produced in small amounts < 2mg/litre cell suspension. The hybrid cells showed a greater diversity of alkaloid biosynthesis when compared with the parental cultures.
Exploring the anticancer potential of pyrazolo[1,2-a]benzo[1,2,3,4] tetrazin-3-one derivatives: The effect on apoptosis induction, cell cycle and pro…
2013
In order to investigate their anticancer potential, four new pyrazolo[1,2-a]benzo[1,2,3,4]-tetrazinone derivatives, designed through the chemometric protocol VLAK, and three of the most active compounds of the previous series have been evaluated on some cellular events including proliferation, apoptosis induction, and cell cycle. The NCI one dose (10 mu M) screening revealed that the 8,9-di-methyl derivative showed activity against Leukemia (CCRF-CEM) and Colon cancer cell line (COLO 205), reaching 81% and 45% of growth inhibition (GI), respectively. Replacement of the two methyl groups with two chlorine atoms maintained the activity toward Leukemia cell (CCRF-CEM, GI 77%) and selectively e…
Characterization of Membrane-Bound Cyclic Nucleotide Phosphodiesterases from Bovine Aortic Smooth Muscle
1992
This study reports the isolation and characterization of cyclic nucleotide phosphodiesterases (PDEs) associated with membrane fraction in comparison to cytosolic forms from bovine aorta. DEAE-Sephacel chromatography of a solubilized membrane fraction from a homogenate, prepared under isotonic conditions in the presence of protease inhibitors, yielded one major peak of PDE activity that specifically hydrolyzed cAMP and was not stimulated by calmodulin: It appeared to contain two subtypes of PDE. The first subtype belonged to the cyclic GMP (cGMP)-inhibited PDE family, (PDE III): It had an apparent Km value of 0.4 microM and was potently inhibited by cGMP, LY186126, and cilostamide. The secon…