Structure of N-[bis(methylthio)methylene]cinnamamide, C12H13NOS2

M r = 251.34, monoclinic, P21/n, a =14.626 (3), b= 7.144 (1), c= 11.996 (2)\AA \betat=90.03 (2) °, V= 1253.4 (6) \AA 3, Z = 4, Dm= 1.326 (3),Dx=1.331(3)gcm -3, MoKat, \lambda = 0.7107 )\AA , \mu=3.51 cm -3, F(000) = 528.0, T-- 293 K, R -- 3.5% for1455 significant reflections. Of particular interest is an intramolecular attractive interaction between the sulphur and oxygen atoms with an S...O distance of 2.658 (3)\AA, in which the oxygen atom appears to actas a nucleophile.

Beta-Ketoacyl-ACP Synthase I/II from Plasmodium falciparum (PfFabB/F)-Is it B or F?

Condensing enzymes play an important and decisive role in terms of fatty acid composition of any organism. They can be classified as condensing enzymes involved in initiating the cycle and enzymes involved in elongating the initiated fatty acyl chain. In E. coli, two isoforms for the elongation condensing enzymes (FabB and FabF) exists whereas Plasmodium genome contains only one isoform. By in vitro complementation studies in E. coli CY244 cells, we show that PfFabB/ functions like E. coli FabF as the growth of the mutant cells could rescued only in the presence of oleic acid. But unlike bacterial enzyme, PfFabB/F does not increase the cis-vaccenic acid content in the mutant cells upon lowering the growth temperature. This study thus highlights the distinct properties of P. falciparum FabF which sets it apart from E. coli and most other enzymes of this family, described so far.

Structure of ethyl 1,2,2-tricyano 3-(4-nitrophenyl)-cyclopropane-1-carboxylate

C15HIoN404, monoclinic, P2~/c, a = 10.694(8), b = 11.743 (8), c - 12.658 (8) A, fl = 113.10 (7) °, V = 1462.1 A 3, Z = 4, O m = 1 "38, O c = 1.408 g cm -3, t,t(MoKa, ~, = 0.7107 ]~) = 0.99 cm -i, F(000) = 640. The structure was solved by direct methods and refined to an R value of 0.054 using 1398 intensity measurements. The relative magnitudes of interaction of the substituents and the extent to which a ring can accommodate interactions with substituents are discussed.

Biochemical effects of 3,5-diethoxycarbonyl-1, 4-dihydrocollidine in mouse liver

3,5-Diethoxycarbonyl-1,4-dihydrocollidine (DDC) is a porphyrinogenic agent and is a powerful inducer of δ-aminolaevulinate synthetase, the first and rate-limiting enzyme of the haem-biosynthetic pathway, in mouse liver. However, DDC strikingly inhibits mitochondrial as well as microsomal haem synthesis by depressing the activity of ferrochelatase in vivo. The drug on repeated administration to female mice has been found to elicit hypertrophic effects in the liver microsomes initially, but the effects observed at later stages denote either hyperplasia or increase in polyploidal cells. The microsomal protein concentration shows a striking decrease with repeated doses of the drug. The rate of microsomal protein synthesis in vivo as well as in vitro shows an increase with two injections of DDC but decreases considerably with repeated administration of the drug. The activities of NADPH-cytochrome creductase and ribonuclease are not affected in the liver microsomes of drug-treated animals when expressed per mg of microsomal protein. DDC has also been found to cause degradation of microsomal haem, which is primarily responsible for the decrease in cytochrome P-450 content. The drug also leads to a decrease in mitochondrial cytochrome c levels due to inhibition of haem synthesis and also due to degradation of mitochondrial haem at later stages. The biochemical effects of the drug are compared and discussed with those reported for allylisopropylacetamide and phenobarbital.

Structure of ethyl 1,2,2-tricyano-3-(4-nitrophenyl)-cyclopropane-1-carboxylate

C15HIoN404, monoclinic, P2~/c, a = 10.694(8), b = 11.743 (8), c - 12.658 (8) A, fl = 113.10 (7) °, V = 1462.1 A 3, Z = 4, O m = 1 "38, O c = 1.408 g cm -3, t,t(MoKa, ~, = 0.7107 ]~) = 0.99 cm -i, F(000) = 640. The structure was solved by direct methods and refined to an R value of 0.054 using 1398 intensity measurements. The relative magnitudes of interaction of the substituents and the extent to which a ring can accommodate interactions with substituents are discussed.

The C-terminal domain is sufficient for endonuclease activity of Neisseria gonorrhoeae MutL

The mutL gene of Neisseria gonorrhoeae has been cloned and the gene product purified. We have found that the homodimeric N. gonorrhoeae MutL (NgoL) protein displays an endonuclease activity that incises covalently closed circular DNA in the presence of Mn2+, Mg2+ or Ca2+ ions, unlike human MutL alpha which shows endonuclease activity only in the presence of Mn2+. We report in the present paper that the C-terminal domain of N. gonorrhoeae MutL (NgoL-CTD) consisting of amino acids 460-658 exhibits Mn2+-dependent endonuclease activity. Sedimentation velocity, sedimentation equilibrium and dynamic light scattering experiments show NgoL-CTD to be a dimer. The probable endonucleolytic active site is localized to a metal-binding motif, DMHAX(2)EX(4)E, and the nicking endonuclease activity is dependent on the integrity of this motif. By in vitro comparison of wild-type and it mutant NgoL-CTD protein, we show that the latter protein exhibits highly reduced endonuclease activity. We therefore suggest that the mode of excision initiation in DNA mismatch repair may be different in organisms that lack MutH protein, but have MutL proteins that harbour the D[M/Q]HAX(2)EX(4)E motif.

The Line Spectral Frequency Model of a Finite-Length Sequence

The line spectral frequency (LSF) of a causal finite length sequence is a frequency at which the spectrum of the sequence annihilates or the magnitude spectrum has a spectral null. A causal finite-length sequencewith (L + 1) samples having exactly L-LSFs, is referred as an Annihilating (AH) sequence. Using some spectral properties of finite-length sequences, and some model parameters, we develop spectral decomposition structures, which are used to translate any finite-length sequence to an equivalent set of AH-sequences defined by LSFs and some complex constants. This alternate representation format of any finite-length sequence is referred as its LSF-Model. For a finite-length sequence, one can obtain multiple LSF-Models by varying the model parameters. The LSF-Model, in time domain can be used to synthesize any arbitrary causal finite-length sequence in terms of its characteristic AH-sequences. In the frequency domain, the LSF-Model can be used to obtain the spectral samples of the sequence as a linear combination of spectra of its characteristic AH-sequences. We also summarize the utility of the LSF-Model in practical discrete signal processing systems.

Porphyrin synthesis in drug induced hepatic porphyria

Liver δ-aminolaevulate (ALA) synthetase and ALA dehydratase are induced to a greater extent in 3,5-diethoxy carbonyl-1,4-dihydrocollidine (DDC) injected mice as compared to the allyl isopropyl acetamide (AIA) injected rats. DDC treated mice do not show an increase in porphobilinogen (PEG) levels commensurate with the increase in ALA levels and the two enzyme activities, but accumulate enormous quantities of protoporphyrin in the liver. Normal mouse liver has an inherent greater capacity to convert PBG to porphyrins as compared to that of the rat. This together with the inhibition of iron incorporation into protoporphyrin in vivo at later stages of DDC administration can account for the large accumulation of protoporphyrin in these animals.

Two-way converter logic for positive and negative binary numbers

This paper describes a hardware implementation of a two-way converter logic by which conversion between numbers from positive to negative binary representation is possible. Index terms: (i) Negative radix, (ii) Positive radix, (iii) Two-way conversion.

Studies on induction of delta-aminolevulinic acid synthetase in mouse liver

Administration of 3,5-diethoxy carbonyl-1,4-dihydrocollidine (DDC) to mice resulted in a striking increase in the level of δ-aminolevulinic acid (ALA) synthetase in liver. Although the enzyme activity was primarily localized in mitochondria and postmicrosomal supernatant fluid, a significant level of activity was also detected in purified nuclei. The time course of induction showed a close parallelism between the bound and free enzyme activities with the former always accounting for a higher percentage of the total activity as compared to the latter. Studies with cycloheximide indicated a half-life of around 3 hr for both the bound and free ALA synthetase. Actinomycin D and hemin prevented enzyme induction when administered along with DDC, but when administered 12 hr after DDC treatment Actinomycin D did not lead to a decay of either the bound or free enzyme activity and hemin inhibited the bound enzyme activity but not the free enzyme level. The molecular sizes of the mitochondrial and cytosolic ALA synthetase(s) were found to be similar on sephadex columns.

Criticality of the exponential rate of decay for the largest nearest-neighbor link in random geometric graphs

Let n points be placed independently in d-dimensional space according to the density f(x) = A(d)e(-lambda parallel to x parallel to alpha), lambda, alpha > 0, x is an element of R-d, d >= 2. Let d(n) be the longest edge length of the nearest-neighbor graph on these points. We show that (lambda(-1) log n)(1-1/alpha) d(n) - b(n) converges weakly to the Gumbel distribution, where b(n) similar to ((d - 1)/lambda alpha) log log n. We also prove the following strong law for the normalized nearest-neighbor distance (d) over tilde (n) = (lambda(-1) log n)(1-1/alpha) d(n)/log log n: (d - 1)/alpha lambda <= lim inf(n ->infinity) (d) over tilde (n) <= lim sup(n ->infinity) (d) over tilde (n) <= d/alpha lambda almost surely. Thus, the exponential rate of decay alpha = 1 is critical, in the sense that, for alpha > 1, d(n) -> 0, whereas, for alpha <= 1, d(n) -> infinity almost surely as n -> infinity.

A Triggering Mechanism for Enhanced Star-Formation in Colliding Galaxies

We propose a physical mechanism to explain the origin of the intense burst of massive-star formation seen in colliding/merging, gas-rich, field spiral galaxies. We explicitly take account of the different parameters for the two main mass components, H-2 and H I, of the interstellar medium within a galaxy and follow their consequent different evolution during a collision between two galaxies. We also note that, in a typical spiral galaxy-like our galaxy, the Giant Molecular Clouds (GMCs) are in a near-virial equilibrium and form the current sites of massive-star formation, but have a low star formation rate. We show that this star formation rate is increased following a collision between galaxies. During a typical collision between two field spiral galaxies, the H I clouds from the two galaxies undergo collisions at a relative velocity of approximately 300 km s-1. However, the GMCs, with their smaller volume filling factor, do not collide. The collisions among the H I clouds from the two galaxies lead to the formation of a hot, ionized, high-pressure remnant gas. The over-pressure due to this hot gas causes a radiative shock compression of the outer layers of a preexisting GMC in the overlapping wedge region. This makes these layers gravitationally unstable, thus triggering a burst of massive-star formation in the initially barely stable GMCs.The resulting value of the typical IR luminosity from the young, massive stars from a pair of colliding galaxies is estimated to be approximately 2 x 10(11) L., in agreement with the observed values. In our model, the massive-star formation occurs in situ in the overlapping regions of a pair of colliding galaxies. We can thus explain the origin of enhanced star formation over an extended, central area approximately several kiloparsecs in size, as seen in typical colliding galaxies, and also the origin of starbursts in extranuclear regions of disk overlap as seen in Arp 299 (NGC 3690/IC 694) and in Arp 244 (NGC 4038/39). Whether the IR emission from the central region or that from the surrounding extranuclear galactic disk dominates depends on the geometry and the epoch of the collision and on the initial radial gas distribution in the two galaxies. In general, the central starburst would be stronger than that in the disks, due to the higher preexisting gas densities in the central region. The burst of star formation is expected to last over a galactic gas disk crossing time approximately 4 x 10(7) yr. We can also explain the simultaneous existence of nearly normal CO galaxy luminosities and shocked H-2 gas, as seen in colliding field galaxies.This is a minimal model, in that the only necessary condition for it to work is that there should be a sufficient overlap between the spatial gas distributions of the colliding galaxy pair.

Stereospecific total synthesis of (±)-albene via a prochiral precursor

The total synthesis of racemic albene 2 via the prochiral precursor 3, using a stereoselective Claisen rearrangement and an intramolecular diazoketone cyclopropanation as key reactions, is described.