Positive correlation between the occurrence of chromosome breakage and the induction of point mutations associated with male recombination 31.1 MRF system of hybrid dysgenesis in Drosophila melanogaster

One of the weak singed (snw) mutations, induced by the 31.1 MRF in the X-chromosome of a laboratory strain, is highly unstable, often changing to either a strong expression (snst) or reverting to wild type (sn+). The present study shows that the X-chromosome carrying the (snw) mutation and the X-chromosome carrying one of the snst alleles derived from the snw mutation generate different frequencies of deletions associated with the w locus. Moreover, they produce different frequencies of mutations associated with the w locus in males after the reintroduction of the 31.1 MRF second chromosome. The occurrence of the deletions and the induction of the mutations are positively correlated and increase when flies are raised at a higher temperature. These data indicate that the induction of the w mutations follows the generation of chromosome breaks in the w locus. The break-points of the recovered deletions occurred in specific sites in the 3C subdivision. Furthermore both snw and snst X-chromosomes induce different frequencies of non-disjunction in females depending on the culture temperature and the genetic background. The present data also show that the 23.5 MRF second chromosome which exhibits specific differences in its activities from the 31.1 MRF is unable to induce w mutations. This fact supports our previous indications that the 31.1 MRF and the 23.5 MRF are not identical.     

Microemulsions as a tool for the regioselective lipase-catalysed esterification of aliphatic diols

The efficiency of Humicola lanuginosa and Candida cylindracea lipases to catalyse the regioselective esterification of butane-1,3-diol with oleic acid has been demonstrated in water-in-oil microemulsion systems stabilized with sodium (bis-2-ethylhexyl) sulphosuccinate as a surfactant in isooctane. Mono- and diesters were selectively synthesized with high reaction rates. The product distribution depends on the positional specificity of the lipases. Water-in-oil microemulsions appear to be an effective and fast system for the regioselective enzymatic esterification of diols. Received: 29 April 1996 / Received revision: 29 July 1996 / Accepted: 5 August 1996     

Enzymatic synthesis of perillyl alcohol derivatives and investigation of their antiproliferative activity

The monoterpene perillyl alcohol (POH), an intermediate in the plant terpenoid biosynthetic pathway, has well-established tumor chemopreventive and chemotherapeutic potential. We have previously shown that the primary hydroxyl group of POH is essential for its antitumor and anti-angiogenic activities. In the current study we present the enzymatic synthesis of two POH derivatives with different polar and hydrophobic characteristics, namely perillyl glucoside and perillyl glucoside fatty ester, through a two-step modification. Initial glucosylation of POH on its active hydroxyl group with D-(+)-glucose and subsequent esterification of the perillyl glucoside product with vinyl laurate were carried out using almond β-glucosidase and lipase B from Candida antarctica, respectively, in a low-water system. Optimization of enzymatic reactions was performed to achieve the highest possible conversion yields. The antitumor cell proliferation activity against mouse Lewis lung carcinoma cells was retained in both derivatives, although the perillyl glucoside ester showed greater inhibition than perillyl glucoside. Our results underline the feasibility of enzymatically producing novel bioactive analogs of phytochemicals displaying useful physicochemical properties.     

Enzymatic acylation of hydroxypropyl cellulose in organic media and determination of ester formation by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy

Esters were prepared by acylation of hydroxypropyl cellulose with fatty acid catalyzed by immobilized lipase from Candida antarctica in tert-butanol. The nature of the substrates used, the initial water activity of the system, and the molecular weight of the hydroxypropyl cellulose were investigated. Moreover, Fourier transform-infrared (FT-IR) spectroscopy was used for determination of ester content on hydroxypropyl cellulose. Specifically, a linear relationship was established between the peak height assigned to the absorption of the esterified carboxyl groups of the cellulose and the ester content. At optimum reaction conditions, the ester content on the hydroxypropyl cellulose was about 11%.     

Unexpected reaction profile observed in the synthesis of propyl laurate when using Candida rugosa lipases immobilized in microemulsions based organogels

1-Propyl laurate synthesis should not be used as standard reaction test of immobilized enzymes in microemulsion-based organogels (MBGs) prepared using lecithin/1-propanol as surfactant when extremely active enzymes with high load are used. In these cases, an anomalous kinetic reaction constant value is observed over short reaction times. Such an anomalous profile is strongly dependent on the concentration of catalyst in the crude powder and, consequently, is not appreciated when either commercial or low activity lipase samples are employed.     

Genetic variation of Marchalina hellenica (Hemiptera: Margarodidae) sampled from different hosts and localities in Greece

Random amplified polymorphic DNA (RAPD) analysis was applied to 120 individuals of Marchalina hellenica (Gennadius) representing six populations collected in northern, central and southern mainland Greece. One population was sampled on one species of fir tree and the others on two species of pine trees. Four random decamer primers were used to evaluate genetic variation among the populations examined. The results revealed intra- and interpopulation polymorphism both related to host type and region of origin. Phylogenetic analysis based on genetic distances estimated by the RAPD frequencies revealed an important genetic differentiation in samples collected on fir trees in southern Greece and to a lesser extent in samples from pine trees in central and northern Greece. Furthermore, considerable subdivision and restricted gene flow among the populations examined were observed. The results are discussed in relation to the biology and geographical distribution of M. hellenica in Greece.     

Antimicrobial activity of acidic xylo-oligosaccharides produced by family 10 and 11 endoxylanases

Acidic oligosaccharides were obtained from birchwood xylan by treatment with a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. The main difference between the products liberated by xylanases of family 10 and 11 concerned the length of the products containing 4-O-methyl-D-glucuronic acid. The xylanase from T. aurantiacus liberate from glucuronoxylan an aldotetrauronic acid as the shortest acidic fragment in contrast with the enzyme from S. thermophile, which liberated an aldopentauronic acid. Acidic xylooligosaccharides were separated from the hydrolysate by anion-exchange and size-exclusion chromatography (SEC) and the primary structure was determined by 13C NMR spectroscopy. The acidic xylo-oligosaccharides were tested against three Gram-positive and three Gram-negative aerobically grown bacteria, as well as against Helicobacter pylori. Aldopentauronic acid was proved more active against the Gram-positive bacteria and against H. pylori.     

Catechol 1,2-dioxygenase from Pseudomonas putida in organic media--an electron paramagnetic resonance study

The ability of an isolated isozyme of catechol 1,2-dioxygenase from Pseudomonas putida DSM 437 to function in a non-aqueous environment was investigated. The lyophilized enzyme is able to keep its catalytic function catalyzing the oxidation of catechol in n-hexane. Electron paramagnetic resonance (EPR) spectroscopy at liquid helium temperatures was applied to compare the properties of the non-heme iron of the enzyme in the organic solvent and in the aqueous solution. The catalytic performance of the enzyme in the organic solvent is correlated with the spectroscopic properties of the non-heme iron.