Reduction of alpha-amylase by an inhibitor from carob

Inhibitor C, one of the inhibitory fractions of the extract of Carob fruit, reduces the amount of α-amylase in the culture medium of endosperm halves of barley seed which have been treated with gibberellic acid as compared with seed halves treated with gibberellic acid alone. A similar reduction is found in the α-amylase produced by embryo halves of barley seed which have not been treated with gibberellic acid.     

Critical target and dose and dose-rate responses for the induction of chromosomal instability by ionizing radiation.

To investigate the critical target, dose response and dose-rate response for the induction of chromosomal instability by ionizing radiation, bromodeoxyuridine (BrdU)-substituted and unsubstituted GM10115 cells were exposed to a range of doses (0.1-10 Gy) and different dose rates (0.092-17.45 Gy min(-1)). The status of chromosomal stability was determined by fluorescence in situ hybridization approximately 20 generations after irradiation in clonal populations derived from single progenitor cells surviving acute exposure. Overall, nearly 700 individual clones representing over 140,000 metaphases were analyzed. In cells unsubstituted with BrdU, a dose response was found, where the probability of observing delayed chromosomal instability in any given clone was 3% per gray of X rays. For cells substituted with 25-66% BrdU, however, a dose response was observed only at low doses (<1.0 Gy); at higher doses (>1.0 Gy), the incidence of chromosomal instability leveled off. There was an increase in the frequency and complexity of chromosomal instability per unit dose compared to cells unsubstituted with BrdU. The frequency of chromosomal instability appeared to saturate around approximately 30%, an effect which occurred at much lower doses in the presence of BrdU. Changing the gamma-ray dose rate by a factor of 190 (0.092 to 17.45 Gy min(-1)) produced no significant differences in the frequency of chromosomal instability. The enhancement of chromosomal instability promoted by the presence of the BrdU argues that DNA comprises at least one of the critical targets important for the induction of this end point of genomic instability.     

Synthesis and spectroscopic studies of antimony pentachloride complexes with neutral oxygen, sulfur and selenium ligands

The compounds [SbCl₅(R₃EY)] (R = Me or Ph; E = P or As; Y = O or S) have been prepared from SbCl₅ and the appropriate ligand in CH₂Cl₂ or CCl₄ solutions, and characterised by analysis, IR, ¹H, ³¹P{¹H}, ¹²¹Sb NMR spectroscopy and conductance measurements. The [SbCl₅(μ-L-L)SbCl₅] L-L = Ph₂P(O)CH₂P(O)Ph₂, Ph₂P(O)(CH₂)₂P(O)Ph₂, Ph₂P(S)CH₂P(S)Ph₂, Ph₂As(O)CH₂As(O)Ph₂, and o-C₆H₄(P(O)Ph₂)₂ have been synthesised and similarly characterised. The unstable [SbCl₅(R₃PSe)] have been prepared at low temperatures and characterised by IR spectroscopy. In solution in chlorocarbons they decompose rapidly to Se and R₃PCl₂. The reactions of R₃SbS with SbCl₅ produced R₃SbCl₂.     

Crystal structures of the two major aggrecan degrading enzymes, ADAMTS4 and ADAMTS5

Aggrecanases are now believed to be the principal proteinases responsible for aggrecan degradation in osteoarthritis. Given their potential as a drug target, we solved crystal structures of the two most active human aggrecanase isoforms, ADAMTS4 and ADAMTS5, each in complex with bound inhibitor and one wherein the enzyme is in apo form. These structures show that the unliganded and inhibitor-bound enzymes exhibit two essentially different catalytic-site configurations: an autoinhibited, nonbinding, closed form and an open, binding form. On this basis, we propose that mature aggrecanases exist as an ensemble of at least two isomers, only one of which is proteolytically active.     

Bacterial DNA topology and infectious disease

The Gram-negative bacterium Escherichia coli and its close relative Salmonella enterica have made important contributions historically to our understanding of how bacteria control DNA supercoiling and of how supercoiling influences gene expression and vice versa. Now they are contributing again by providing examples where changes in DNA supercoiling affect the expression of virulence traits that are important for infectious disease. Available examples encompass both the earliest stages of pathogen–host interactions and the more intimate relationships in which the bacteria invade and proliferate within host cells. A key insight concerns the link between the physiological state of the bacterium and the activity of DNA gyrase, with downstream effects on the expression of genes with promoters that sense changes in DNA supercoiling. Thus the expression of virulence traits by a pathogen can be interpreted partly as a response to its own changing physiology. Knowledge of the molecular connections between physiology, DNA topology and gene expression offers new opportunities to fight infection.     

Triterpenoid saponins from a cytotoxic root extract of Sideroxylonfoetidissimum subsp. gaumeri

Evaluation of the cytotoxicity of an ethanolic root extract of Sideroxylonfoetidissimum subsp. gaumeri (Sapotaceae) revealed activity against the murine macrophage-like cell line RAW 264.7. Systematic bioassay-guided fractionation of this extract gave an active saponin-containing fraction from which four saponins were isolated. Use of 1D (¹H, ¹³C, DEPT135) and 2D (COSY, TOCSY, HSQC, and HMBC) NMR, mass spectrometry and sugar analysis gave their structures as 3-O-(β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl)-28-O-(α-l-rhamnopyranosyl-(1 → 3)[β-d-xylopyranosyl-(1 → 4)]-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-16α-hydroxyprotobassic acid, 3-O-β-d-glucopyranosyl-28-O-(α-l-rhamnopyranosyl-(1 → 3)[β-d-xylopyranosyl-(1 → 4)]-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-16α-hydroxyprotobassic acid, 3-O-(β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl)-28-O-(α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 4)[β-d-apiofuranosyl-(1 → 3)]-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-16α-hydroxyprotobassic acid, and the known compound, 3-O-β-d-glucopyranosyl-28-O-(α-l-rhamnopyranosyl-(1 → 3)[β-d-xylopyranosyl-(1 → 4)]-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-protobassic acid. Two further saponins were obtained from the same fraction, but as a 5:4 mixture comprising 3-O-(β-d-glucopyranosyl)-28-O-(α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 4)[β-d-apiofuranosyl-(1 → 3)]-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-16α-hydroxyprotobassic acid and 3-O-(β-d-apiofuranosyl-(1 → 3)-β-d-glucopyranosyl)-28-O-(α-l-rhamnopyranosyl-(1 → 3)[β-d-xylopyranosyl-(1 → 4)]-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl)-16α-hydroxyprotobassic acid, respectively. This showed greater cytotoxicity (IC₅₀ = 11.9 ± 1.5 μg/ml) towards RAW 264.7 cells than the original extract (IC₅₀ = 39.5 ± 4.1 μg/ml), and the saponin-containing fraction derived from it (IC₅₀ = 33.7 ± 6.2 μg/ml).