Laurel forests in Tenerife, Canary Islands

The general wood structure, vessel size and distribution along the stem xylem radius and in petioles were studied in Laurus azorica trees living in a Tenerife laurel forest. The fractions of volume occupied by dry matter, water and air in percentage of wood fresh volume were also studied. The wood showed a diffuse-porous structure, with solitary vessels or vessels somewhat clustered in small radially oriented groups. Vessels had a diameter ranging from 20 to 130 µm. This diameter was minimal close to the pith, increased more than 2-fold with age, and reached its maximum width close to the cambium. Vessel density decreased from 36 vessels mm^-2 near the pith to about 13 vessels mm^-2 near the cambium. Accordingly, the lumen area was small in young xylem close to the pith (0.0015 mm²), reaching a value 5 times larger (0.007 mm²) near the cambium than in the centre of the stem. Lumen area of vessels in petioles was about 1.5% of petiole cross-sectional area and thus much lower than in stems. Mean hydraulic diameter of these vessels was about 20 µm, and mean vessel density about 136 per petiole. There were only small differences in proportions of dry matter, water and air along stem radius. The relevance of each one of these fractions in the wood is discussed as evidence of the possible existence of a number of embolized vessels dispersed in the total functional cross-sectional area of the xylem.     

Sequence and Structural Features of Enzymes and their Active Sites by EC Class

We have analysed a non-redundant set of 294 enzymes for differences in sequence and structural features between the six main Enzyme Commission (EC) classification groups. This systematic study of enzymes, and their active sites in particular, aims to increase understanding of how the structure of an enzyme relates to its functional role. Many features showed significant differences between the EC classes, including active-site polarity, enzyme size and active-site amino acid propensities. Many attributes correlate with each other to form clusters of related features from which we chose representative features for further analysis. Oxidoreductases have more non-polar active sites, which can be attributed to cofactor binding and a preference for Glu over Asp in active sites in comparison to the other classes. Lyases form a significantly higher proportion of oligomers than any other class, whilst the hydrolases form the largest proportion of monomers. These features were then used in a prediction model that classified each enzyme into its top EC class with an accuracy of 33.1%, which is an increase of 16.4% over random classification. Understanding the link between structure and function is critical to improving enzyme design and the prediction of protein function from structure without transfer of annotation from alignments.     

A structurally characterised ruthenium bis(pyrazolyl)borate benzylidene complex containing an agostic Ru?H-C interaction: synthesis and catalytic activity

A ruthenium bis(pyrazolyl)borate benzylidene has been synthesised. A single crystal X-ray diffraction study showed that the complex contained an agostic Ru?H-C interaction. The complex displayed catalytic activity for the ring closing metathesis of diethyl diallylmalonate in the presence of CuCl as a co-catalyst in refluxing toluene.     

Aneuploidies, chromosome aberrations and dominant gene mutations detected in 113,913 consecutive newborn children in Mexico

Data on 113,913 liveborn children from a hospital in Guadalajara, Jalisco (Mexico), were analysed for birth defects (BD); mutation rates were calculated for sporadic aneuploidy, chromosome aberrations and dominant gene mutations. The results showed a general incidence of 13.92 BD cases per 1000 liveborns, of which 1.64% were chromosomal abnormalities, 1.50% were aneuploid, 0.14% were structural chromosome aberrations and 3.23% were dominant gene mutations. The mutation rates were 8.20 x 10(-4) chromosomal abnormalities, 7.5 x 10(-4) aneuploidies, 7.0 x 10(-5) chromosome aberrations and 1.61 x 10(-3) dominant gene mutations/gamete/generation, respectively. The lethality rate was 15.32% of the liveborns with BD. The described findings estimate the incidence of new human mutants detected at birth in a sample of the Mexican population. They show that the rate for some aneuploidies are similar to those found in other populations previously reported in the literature but the rates of chromosome and dominant gene mutations were different.     

Phosphorylation of ribosomal proteins induced by auxins in maize embryonic tissues

The effect of auxin on ribosomal protein phosphorylation of germinating maize (Zea mays) tissues was investigated. Two-dimensional gel electrophoresis and autoradiography of [³²P] ribosomal protein patterns for natural and synthetic auxin-treated tissues were performed. Both the rate of ³²P incorporation and the electrophoretic patterns were dependent on ³²P pulse length, suggesting that active protein phosphorylation-dephosphorylation occurred in small and large subunit proteins, in control as well as in auxin-treated tissues. The effect of ribosomal protein phosphorylation on in vitro translation was tested. Measurements of poly(U) translation rates as a function of ribosome concentration provided apparent K_m values significantly different for auxin-treated and nontreated tissues. These findings suggest that auxin might exert some kind of translational control by regulating the phosphorylated status of ribosomal proteins.     

Isoproterenol oxidation by tyrosinase: intermediates characterization and kinetic study

The present work deals with isoproterenol oxidation by mushroom tyrosinase and sodium metaperiodate. Intermediates produced at short reaction time were characterized by scanning repetitive spectrophotometry and the stoichiometry of the respective aminochrome appearance was established. The oxidation pathway from isoproterenol to aminochrome is parallel to the previously proposed for L-dopa oxidation by mushroom tyrosinase, whose steps are as follow: Isoproterenol----o-quinone-H+----o-quinone----leukoaminochrome---- aminochrome. The stoichiometry for the conversion of o-quinone-H+ into the aminochrome of isoproterenol followed the equation: 2 o-quinone-H+----isoproterenol + aminochrome. The kinetics of chemical reactions that take place from the o-quinone-H+ to aminochrome has been studied as a system of various chemical reactions coupled to an enzymatic reaction (EzCC: Enzymatic-Chemical-Chemical mechanism).