Omega-Hydroxylation of acyclic monoterpene alcohols by rat lung microsomes

Rat lung microsomes were shown to �-hydroxylate acyclic monoterpene alcohols in the presence of NADPH and O2. NADH could neither support hydroxylation efficiently nor did it show synergistic effect. The hydroxylase activity was greater in microsomes prepared from β-naphthoflavone (BNF)-treated rats than from phenobarbital (PB)-treated or control microsomal preparations. Hydroxylation was specific to the C-8 position in geraniol and has a pH optimum of 7.8. The inhibition of the hydroxylase activity by SKF-525A, CO, N-ethylmaleimide, ellipticine, α-naphthoflavone, cyt. Image and p-CMB indicated the involvement of the cyt. P-450 system. However, NaN3 stimulated the hydroxylase activity to a significant level. Rat kidney microsomes were also capable of �-hydroxylating geraniol although the activity was lower than that observed with lungs.

A note on acyclic edge coloring of complete bipartite graphs

An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic (2-colored) cycles. The acyclic chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and is denoted by a'(G). Let Delta = Delta(G) denote the maximum degree of a vertex in a graph G. A complete bipartite graph with n vertices on each side is denoted by K-n,K-n. Alon, McDiarmid and Reed observed that a'(K-p-1,K-p-1) = p for every prime p. In this paper we prove that a'(K-p,K-p) <= p + 2 = Delta + 2 when p is prime. Basavaraju, Chandran and Kummini proved that a'(K-n,K-n) >= n + 2 = Delta + 2 when n is odd, which combined with our result implies that a'(K-p,K-p) = p + 2 = Delta + 2 when p is an odd prime. Moreover we show that if we remove any edge from K-p,K-p, the resulting graph is acyclically Delta + 1 = p + 1-edge-colorable. (C) 2009 Elsevier B.V. All rights reserved.

Acyclic Edge Coloring of Graphs with Maximum Degree 4

An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The acyclic chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and is denoted by a'(G). It was conjectured by Alon, Sudakov, and Zaks that for any simple and finite graph G, a'(G) <= Delta+2, where Delta=Delta(G) denotes the maximum degree of G. We prove the conjecture for connected graphs with Delta(G)<= 4, with the additional restriction that m <= 2n-1, where n is the number of vertices and m is the number of edges in G. Note that for any graph G, m <= 2n, when Delta(G)<= 4. It follows that for any graph G if Delta(G)<= 4, then a'(G) <= 7.

Binary decompositions and acyclic schemes

It is well known that the notions of normal forms and acyclicity capture many practical desirable properties for database schemes. The basic schema design problem is to develop design methodologies that strive toward these ideals. The usual approach is to first normalize the database scheme as far as possible. If the resulting scheme is cyclic, then one tries to transform it into an acyclic scheme. In this paper, we argue in favor of carrying out these two phases of design concurrently. In order to do this efficiently, we need to be able to incrementally analyze the acyclicity status of a database scheme as it is being designed. To this end, we propose the formalism of "binary decompositions". Using this, we characterize design sequences that exactly generate theta-acyclic schemes, for theta = agr,beta. We then show how our results can be put to use in database design. Finally, we also show that our formalism above can be effectively used as a proof tool in dependency theory. We demonstrate its power by showing that it leads to a significant simplification of the proofs of some previous results connecting sets of multivalued dependencies and acyclic join dependencies.

A necessary and sufficient condition for acyclic graphs

This letter gives a new necessary and sufficient condition to determine whether a directed graph is acyclic.

Recognition And Top-Down Generation Of Beta-Acyclic Database Schemes

Database schemes can be viewed as hypergraphs with individual relation schemes corresponding to the edges of a hypergraph. Under this setting, a new class of "acyclic" database schemes was recently introduced and was shown to have a claim to a number of desirable properties. However, unlike the case of ordinary undirected graphs, there are several unequivalent notions of acyclicity of hypergraphs. Of special interest among these are agr-, beta-, and gamma-, degrees of acyclicity, each characterizing an equivalence class of desirable properties for database schemes, represented as hypergraphs. In this paper, two complementary approaches to designing beta-acyclic database schemes have been presented. For the first part, a new notion called "independent cycle" is introduced. Based on this, a criterion for beta-acyclicity is developed and is shown equivalent to the existing definitions of beta-acyclicity. From this and the concept of the dual of a hypergraph, an efficient algorithm for testing beta-acyclicity is developed. As for the second part, a procedure is evolved for top-down generation of beta-acyclic schemes and its correctness is established. Finally, extensions and applications of ideas are described.

Acyclic peptides as conformational models Crystal structure of Boc-Aib-Leu-Pro-NHMe± 2H2O

The tripeptide Boc-Aib-Leu-Pro-NHMe crystallizes in the orthorhombic space group P212121 with a = 9.542, b = 15.200, c = 18.256 Å and Z = 4. Each peptide is associated wth two water molecules in the asymmetric unit of the crystal. The structure has been solved by direct methods and refined to an R-value of 0.069. The peptide adopts a structure without any intramolecular hydrogen bond. The three residues occupy distinctly different regions of the Ramachandran map: Aib in the left-handed 310-helical region (± = 67°, ± = 23°), Leu in the β-sheet region (± = - 133°, ± = 142°) and Pro in the poly (Pro) II region (± = - 69°, ± = 151°). An interesting observation is that each water molecule participates in four hydrogen bonds with distorted tetrahedral coordination about the oxygen atom.

Omega-hydroxylation of acyclic monoterpene alcohols by rat lung microsomes

Rat lung microsomes were shown to ω-hydroxylate acyclic monoterpene alcohols in the presence of NADPH and O2. NADH could neither support hydroxylation efficiently nor did it show synergistic effect. The hydroxylase activity was greater in microsomes prepared from β-naphthoflavone (BNF)-treated rats than from phenobarbital (PB)-treated or control microsomal preparations. Hydroxylation was specific to the C-8 position in geraniol and has a pH optimum of 7.8. The inhibition of the hydroxylase activity by SKF-525A, CO, N-ethylmaleimide, ellipticine, α-naphthoflavone, cyt. Image and p-CMB indicated the involvement of the cyt. P-450 system. However, NaN3 stimulated the hydroxylase activity to a significant level. Rat kidney microsomes were also capable of ω-hydroxylating geraniol although the activity was lower than that observed with lungs.

Theoretical-Studies On The Conformations Of Acyclic Alditols

The conformational analysis by energy calculation is described for some acyclic sugars such as D-glucitol, D-mannitol and galactitol. Planar Zig-zag conformation is the most favoured conformation for the three alditols. However, the energy difference between the ‘bent-chain’ and ‘straight-chain’ conformation is less in the case of D-glucitol (0.9 Kcal Mole-1)compared to those of D-mannitol (~2.4 Kcal mole-1)and galactitol (~2.5 Kcal Mole-1).The solvent accessibility studies favour bent –chain conformation for D-glucitol and straight-chain conformation for D-mannitol and glactitol. These conformations, arrived at by theorticle analysis are compared with those abseverd in the solid state determined by X=ray differaction techinique and their acetylated derivatives in solution by NMR technique. These studies suggest that, when the energy difference between straight and bent conformations is small, latticc energy (in the case of solids) and solvent (in the case of solutions) do play a dominant role on the favoured conformations.

Metabolism of structurally modified acyclic monoterpenes by Pseudomonas incognita

The ability of Pseudomonas incognita to metabolize some structurally modified acyclic monoterpenes was tested. The 6,7 double bond was found essential for these compounds to serve as a substrate for this organism, whereas the same was not true with the 1,2 double bond. Metabolism of dihydrolinalyl acetate by this strain yielded dihydrolinalool, dihydrolinalool-8-carboxylic acid, dihydrolinalyl acetate-8-carboxylic acid, and 4-acetoxy-4-methyl hexanoic acid. A cell-free extract prepared from dihydrolinalyl acetate grown cells transformed dihydrolinalyl acetate into dihydrolinalool and dihydrolinalool-8-carboxylic acid. Based on the identification of various metabolites isolated from the culture medium, and on growth and manometric studies carried out with the isolated metabolites as well as with related synthetic analogs, probable pathways for the biodegradation of dihydrolinalyl acetate are presented.

Microbial transformations of acyclic monoterpenes

Microbial degradation of geraniol, citronellol, linalool and their corresponding acetates, structurally modified linalool and linalyl acetate, α-terpineol and β-myrcene are presented. Oxygenative and prototropic rearrangements are normally observed during the microbial metabolism of monoterpenes. Three types of oxygenation reactions are observed, namely, (a) allylic oxygenation (b) oxygenation on a double bond and (c) addition of water across the double bond. The studies indicate commonality in the reaction types or processes occurring during the metabolism of various related monoterpenes and also establish the convergence of degradative pathways at a central catabolic intermediate.

Acyclic edge coloring of subcubic graphs

An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The acyclic chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and it is denoted by a′(G). From a result of Burnstein it follows that all subcubic graphs are acyclically edge colorable using five colors. This result is tight since there are 3-regular graphs which require five colors. In this paper we prove that any non-regular connected graph of maximum degree 3 is acyclically edge colorable using at most four colors. This result is tight since all edge maximal non-regular connected graphs of maximum degree 3 require four colors.

d-Regular Graphs of Acyclic Chromatic Index at Least d+2

An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The acyclic chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and is denoted by a'(G). It was conjectured by Alon, Suclakov and Zaks (and earlier by Fiamcik) that a'(G) <= Delta+2, where Delta = Delta(G) denotes the maximum degree of the graph. Alon et al. also raised the question whether the complete graphs of even order are the only regular graphs which require Delta+2 colors to be acyclically edge colored. In this article, using a simple counting argument we observe not only that this is not true, but in fact all d-regular graphs with 2n vertices and d>n, requires at least d+2 colors. We also show that a'(K-n,K-n) >= n+2, when n is odd using a more non-trivial argument. (Here K-n,K-n denotes the complete bipartite graph with n vertices on each side.) This lower bound for Kn,n can be shown to be tight for some families of complete bipartite graphs and for small values of n. We also infer that for every d, n such that d >= 5, n >= 2d+3 and dn even, there exist d-regular graphs which require at least d+2-colors to be acyclically edge colored. (C) 2009 Wiley Periodicals, Inc. J Graph Theory 63: 226-230, 2010.

Conformations of dehydrophenylalanine containing peptides: nmr studies of an acyclic hexapeptide with two delta Z-Phe residues

The conformation of an acyclic dehydrophenylalanine (delta Z-Phe) containing hexapeptide, Boc-Phe-delta Z-Phe-Val-Phe-delta Z-Phe-Val-OMe, has been investigated in CDCl3 and (CD3)2SO by 270-MHz 1H-nmr. Studies of NH group solvent accessibility and observation of interresidue nuclear Overhauser effects (NOEs) suggest a significant solvent-dependent conformational variability. In CDCl3, a population of folded helical conformations is supported by the inaccessibility to solvent of the NH groups of residues 3-6 and the detection of several NiH----Ni + 1H NOEs. Evidence is also obtained for conformational heterogeneity from the detection of some Ci alpha H----Ni + 1H NOEs characteristic of extended strands. In (CD3)2SO, the peptide largely favors an extended conformation, characterized by five solvent-exposed NH groups and successive Ci alpha H----Ni + 1H NOEs for the L-residues and Ci beta H----Ni + 1H NOEs for the delta Z-Phe residues. The results suggest that delta Z-Phe residues do not provide compelling conformational constraints.