The pyrrolidine ring of nicotine has been shown to be formed from ornithine, glutamic acid, and proline (l-5). Although little information is available concerning the interrelationship of these three amino acids in higher plants, Al-pyrrolinedcarboxylate (in equilibrium with glutamic semialdehyde) has been shown to be a key intermediate in their interconversion in animals and microorganisms (6,...

Density functional theoretical calculations are used to elucidate the epoxidation mechanism of styrene with a cytochrome P450 model Compound I, and the formation of side products. The reaction features multistate reactivity (MSR) with different spin states (doublet and quartet) and different electromeric situations having carbon radicals and cations, as well as iron(III) and iron(IV) oxidation ...

The naphthoquinones lapachol and dichloroallyl lawsone readily undergo oxidative ring fission when incubated with several fungi and streptomycetes. Penicillium notatum was employed to produce the ring fission product of dichloroallyl lawsone which was isolated and characterized by spectral analyses and chemical synthesis. The mechanism of oxidative ring fission of lapachol was studied by growin...

The ground state structure of few-electron concentric double quantum rings is investigated within the local spin density approximation. Signatures of inter-ring coupling in the addition energy spectrum are identified and discussed. We show that the electronic configurations in these structures can be greatly modulated by the inter-ring distance: At short and long distances the low-lying electro...

Under secondary metabolic conditions, the white-rot basidiomycete Phanerochaete chrysosporium degraded 2,7-dichlorodibenzo-p-dioxin (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell-free extracts. The multistep pathway involve...

A ring of aligned glutamate residues named the intermediate ring of charge surrounds the intracellular end of the acetylcholine receptor channel and dominates cation conduction (Imoto et al. 1988). Four of the five subunits in mouse-muscle acetylcholine receptor contribute a glutamate to the ring. These glutamates were mutated to glutamine or lysine, and combinations of mutant and native subuni...

Degraded limonoids are a subclass of limonoid natural products that derive from ring-intact or ring-rearranged limonoids. Establishment robust synthetic routes to access them could provide valuable materials identify the simplest active pharmacophore responsible for observed biological activities parent molecules. This communication delineates development divergent strategy furnish melazolide B...

In this paper, we generalize sone well-known commutativity theorems for associative rings as follows: Let ’, > 1. ,,, .,, and be fixed nou-ncgative integers such that s ik m1, or i/= n1, and let R be a ring xvith unity satisfying the polynomial identity y*[x’,y] [x,y’]x for all y R. Sul,lose that (i) R has Q(z) (that is n[x,y] 0 implies [z,y] 0); (ii) the set of d] nilpotent ,,lem,’nts of R is ...