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PubMedDate not supplied

The effect of microwave energy on specific migration from food contact plastics.

Experiments have been carried out with (a) microwave treatment of plastics followed by migration testing using the food simulant, olive oil, and (b) microwave treatment of plastics in direct contact with an organic extractant (iso-octane). In neither of these complementary approaches was there evidence of any difference in migration from plastics that had been microwave-treated compared with plastics that had received an equivalent thermal treatment. Five plastics commonly employed in microwave applications were tested and oligomers, plasticizer, antioxidant and volatile contaminants were monitored as representatives of typical migration species.

Dietary Fats, Unsaturated↗
PubMed1997

Behavior of uridine phosphorylase from Escherichia coli K-12 in hydrated reversed micelles of surfactant in organic solvent.

The catalytic activity of uridine phosphorylase from Escherichia coli K-12 entrapped in hydrated reversed micelles of aerosol OT (AOT) in octane has been studied as a function of the degree of hydration of micelles. It was shown that the catalytic activity reaches maximum values at ratios [H2O]/[AOT] equal to 8.4, 12.8, 16.1, and 18.6. On the basis of sedimentation data the conclusion has been made that the maximums of the catalytic activity of uridine phosphorylase correspond to monomeric, dimeric, trimeric, and tetrameric forms of the enzyme.

Bacterial Proteins↗
PubMed1987

"Imposed" and "inherent" mucosal activity patterns. Their composite representation of olfactory stimuli.

Both regional differences in mucosal sensitivity and a gas chromatography-like process along the mucosal sheet have been separately proposed in two sets of earlier studies to produce different odorant-dependent activity patterns across the olfactory mucosa. This investigation evaluated, in one study, whether and to what degree these two mechanisms contribute to the generation of these activity patterns. Summated multiunit discharges were simultaneously recorded from lateral (LN) and medial (MN) sites on the bullfrog's olfactory nerve to sample the mucosal activity occurring near the internal and external nares, respectively. Precisely controlled sniffs of four odorants (benzaldehyde, butanol, geraniol, and octane) were drawn through the frog's olfactory sac in both the forward (H1) and reverse (H2) hale directions. By combining the four resulting measurements, LNH1, LNH2, MNH1, and MNH2, in different mathematical expressions, indexes reflecting the relative effects of the chromatographic process, regional sensitivity, and hale direction could be calculated. Most importantly, the chromatographic process and the regional sensitivity differences both contributed significantly to the mucosal activity patterns. However, their relative roles varied markedly among the four odorants, ranging from complete dominance by either one to substantial contributions from each. In general, the more strongly an odorant was sorbed by the mucosa, the greater was the relative effect of the chromatographic process; the weaker the sorption, the greater the relative effect of regional sensitivity. Similarly, the greater an odorant's sorption, the greater was the effect of hale direction. Other stimulus variables (sniff volume, sniff duration, and the number of molecules within the sniff) had marked effects upon the overall size of the response. For strongly sorbed odorants, the effect of increasing volume was positive; for a weakly sorbed odorant, it was negative. The reverse may be true for duration. In contrast, the effect of increasing the number of molecules was uniformly positive for all four odorants. However, there was little evidence that these other stimulus variables had a major influence upon the effects of the chromatographic process and regional sensitivity differences in their generation of mucosal activity patterns.

Acyclic Monoterpenes↗
PubMed1980

A liquid ionisation chamber for neutron dosimetry.

Theories of ionisation in liquid and the use of liquid ionisation chambers in mixed neutron field dosimetry have been studied. Theoretical models developed by Jaffe and by Onsager were used for comparison with the experimental measurements. The Jaffe method predicts a higher collecting efficiency than does the Onsager model. Gamma and neutron sensitivities of a liquid chamber can be calculated by the Bragg-Gray principle and Onsager's theory. The calculation is subject to relatively large uncertainties, mainly due to insufficient knowledge of the ion distribution in ionisation tracks and of W/e values for iso-octane. The chamber constructed for clinical use should work best for mixed neutron fields with gamma-neutron ratios of 10-20%; however, it would be difficult to use a liquid ionisation chamber to detect small neutron variations in mixed fields with large gamma components.

Energy Transfer↗
PubMed1991

Engineering of functional supramacromolecular complexes of proteins (enzymes) using reversed micelles as matrix microreactors.

The size of the inner water cavity of reversed micelles formed in a triple system 'water-surfactant-organic solvent' can be widely varied by changing the degree of surfactant hydration. This gives grounds to use reversed micelles as matrix microreactors for the design of supramolecular complexes of proteins. Using ultracentrifugation analysis, it has been demonstrated that the oligomeric composition of various enzymes (ketoglutarate dehydrogenase, alkaline phosphatase, lactic dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase) solubilized in reversed micelles of Aerosol OT [sodium bis(2-ethylehexyl)sulfosuccinate] in octane changes upon variation of the degree of hydration. An oligomeric complex forms under conditions when the radius of the micelle inner cavity is big enough to incorporate this complex as a whole. At lower degrees of hydration the micelles 'uncouple' such complexes to their components. The catalytic properties of various oligomeric complexes have been studied. Possibilities of using reversed micelles for the separation of subunits of oligomeric enzymes under non-denaturating conditions have been demonstrated. In particular, the isolated subunits of alkaline phosphatase, lactic dehydrogenase and glyceraldehyde-3-phosphate have been found to be active in Aerosol OT reversed micelles. The dependences of the catalytic activity of oligomeric enzymes represent saw-like curves. The maxima of the catalytic activity observed at these curves relate to the functioning of various oligomeric forms of an enzyme. The radii of the micelle inner cavity under conditions when these maxima are observed correlate with the linear dimensions of the enzyme oligomeric forms. Correlation of the position of a maximum with the shape of an oligomeric complex is discussed.

Alkaline Phosphatase↗
PubMed2004

Parvibaculum lavamentivorans gen. nov., sp. nov., a novel heterotroph that initiates catabolism of linear alkylbenzenesulfonate.

Strain DS-1T is a small (0.8 microm in length and 0.2 microm in diameter) heterotrophic bacterium able to omega-oxygenate the commercial surfactant linear alkylbenzenesulfonate (LAS) and shorten the side chain by beta-oxidation to yield sulfophenylcarboxylates. The morphotype is widespread in cultures able to utilize LAS, and a second organism with similar characteristics, strain AN-8, is now available. Utilization of LAS is concomitant with formation of a biofilm, and cells were non-motile. Many surfactants were utilized. The organisms also grew with acetate or octane, but required no biofilm and were motile. Analysis of the gene encoding 16S rRNA placed the organisms in the alpha-subclass of the Proteobacteria with a sequence divergence of >8 % from any species whose name has been validly published. 16S rRNA gene sequence comparison with entries in the GenBank database showed 98 % similarity to an alpha-protobacterial marine isolate, JP57: strain JP57 displayed the same morphotype as strain DS-1T, but it was unable to utilize surfactants or any single source of carbon tested. The lipid components of strains DS-1T and JP57 were virtually identical. The fatty acids contained ester- and putative amide-linked hydroxy fatty acids, in a combination that is currently unique in the alpha-Proteobacteria. The major respiratory quinone present in both strains was Q11. The polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and two unidentified aminolipids. Data on the 16S rRNA gene sequence and the lipid composition indicated that strains DS-1T and JP57 should be placed in a new genus, for which the name Parvibaculum is proposed. The differences between these strains, supported by DNA hybridizations, lead to the conclusion that strain DS-1T (= DSM 13023T = NCIMB 13966T) is the type strain of a species in the genus Parvibaculum, for which the name Parvibaculum lavamentivorans gen. nov., sp. nov. is proposed.

Acetic Acid↗
PubMed1993

Reverse micelles as a water-property-control system to investigate the hydration/activity relationship of alpha-chymotrypsin.

alpha-Chymotrypsin, solubilized in hydrated reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in n-octane, was used as a model system for studying the involvement of different water structures (strongly bound water, disordered water, water clusters and bulk water) in the development of the catalytically active conformation of the enzyme. Results presented in this study indicate a characteristic dependence of the stability/activity profile on the water content of the reverse-micellar system for values of wo of approximately 5 (wo is defined as [H2O]/[AOT]). The results are consistent with heat-capacity measurements for proteins. At very low wo values, the conformation of alpha-chymotrypsin changes to a very rigid structure in comparison to the structure observed in water. This is demonstrated by the overall center of gravity of the tryptophan fluorescence spectrum of the enzyme at wo = 0.65, which is blue shifted in comparison to the spectrum in bulk water indicating that the enzyme is in an apolar environment. In the absence of a hydration shell, the protein is to a great extent frozen and inactive. A small increase in the level of enzyme hydration (up to wo = 2.3) causes an increase in the amount of strongly bound water associated with the enzyme and the enzyme displays a high catalytic activity. Upon further addition of water, a new unstable water structure with unfavourable enthalpy is developed and the enzyme activity declines, reaching a minimum at wo = 5.1. A new increase of water content within a relatively small range, wo = 5-8, causes a dramatic increase in enzymic activity, reminiscent of a cooperative hydration dependence. In the range wo = 10-29, the effect of hydration on the activity is complete which shows that the enzyme activity depends on the amount of water in contact with the enzyme and not on the total amount of bulk water in the system. The experimental results on enzyme incubation at different wo values followed by dilution to constant high wo, are indicative of inactive conformational substates of alpha-chymotrypsin. It is demonstrated that highly active enzyme conformations at very low, wo values occur via an induced fit mechanism of substrate binding.

Animals↗
PubMed2006

Propane and n-butane oxidation by Pseudomonas putida GPo1.

Propane and n-butane inhibit methyl tertiary butyl ether oxidation by n-alkane-grown Pseudomonas putida GPo1. Here we demonstrate that these gases are oxidized by this strain and support cell growth. Both gases induced alkane hydroxylase activity and appear to be oxidized by the same enzyme system used for the oxidation of n-octane.

Butanes↗
PubMed1983

Inhibition of bacterial adherence to hydrocarbons and epithelial cells by emulsan.

Acinetobacter calcoaceticus RAG-1 and BD413, as well as Streptococcus pyogenes M-5, adhered to octane. Adherence was inhibited by emulsan (100 micrograms/ml), the polymeric emulsifying agent produced by A. calcoaceticus RAG-1. Emulsan also inhibited adherence of S. pyogenes and RAG-1 to buccal epithelial cells. The mean values of bound S. pyogenes per epithelial cell were 57.2 and 20.7 for the control and emulsan-containing suspensions, respectively; mean values of bound RAG-1 per epithelial cell were 221 for the control and 40 for the suspension containing 100 micrograms of emulsan per ml. Desorption of previously bound RAG-1 from epithelial cells by emulsan was concentration dependent: a maximum of 80% desorption was obtained with 200 micrograms of emulsan per ml. The data showing that emulsan desorbed 70% of the indigenous bacterial flora from buccal epithelial cells suggest that hydrophobic interactions mediate not only the in vitro adherence of laboratory strains to epithelial cells, but actually govern the adherence of the majority of the bacteria that colonize this surface. The advantages of using emulsan as an antiadherence agent include its chemical purity, stability, and polymeric nature.

Acinetobacter↗
PubMed2002

Rubredoxins involved in alkane oxidation.

Rubredoxins (Rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. Several Rd genes associated with alkane hydroxylase or Rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (Alk-Rds). Complementation tests in an Escherichia coli recombinant containing all Pseudomonas putida GPo1 genes necessary for growth on alkanes except Rd 2 (AlkG) and sequence comparisons showed that the Alk-Rds can be divided in AlkG1- and AlkG2-type Rds. All alkane-degrading strains contain AlkG2-type Rds, which are able to replace the GPo1 Rd 2 in n-octane hydroxylation. Most strains also contain AlkG1-type Rds, which do not complement the deletion mutant but are highly conserved among gram-positive and gram-negative bacteria. Common to most Rds are the two iron-binding CXXCG motifs. All Alk-Rds possess four negatively charged residues that are not conserved in other Rds. The AlkG1-type Rds can be distinguished from the AlkG2-type Rds by the insertion of an arginine downstream of the second CXXCG motif. In addition, the glycines in the two CXXCG motifs are usually replaced by other amino acids. Mutagenesis of residues conserved in either the AlkG1- or the AlkG2-type Rds, but not between both types, shows that AlkG1 is unable to transfer electrons to the alkane hydroxylase mainly due to the insertion of the arginine, whereas the exchange of the glycines in the two CXXCG motifs only has a limited effect.

Alkanes↗
PubMed2002

Preparation of gelatin microbeads with a narrow size distribution using microchannel emulsification.

The purpose of this study was to prepare monodisperse gelatin microcapsules containing an active agent using microchannel (MC) emulsification, a novel technique for preparing water-in-oil (W/O) and oil-in-water (O/W) emulsions. As the first step in applying MC emulsification to the preparation of monodisperse gelatin microcapsules, simple gelatin microbeads were prepared using this technique. A W/O emulsion with a narrow size distribution containing gelatin in the aqueous phase was created as follows. First, the aqueous disperse phase was fed into the continuous phase through the MCs at 40 degrees C (operating pressure: 3.9 kPa). The emulsion droplets had an average particle diameter of 40.7 microm and a relative standard deviation of 5.1%. The temperature of the collected emulsion was reduced and maintained at 25 degrees C overnight. The gelatin microbeads had a smooth surface after overnight gelation; the average particle diameter was calculated to be 31.6 microm, and the relative standard deviation, 7.3%. The temperature was then lowered to 5 degrees C by rapid air cooling and finally dried. The gelatin beads were dried and could be resuspended well in iso-octane. They had an average particle diameter of 15.6 microm, and a relative standard deviation of 5.9%. Using MC emulsification, we were able to prepare gelatin microbeads with a narrow size distribution. Since this emulsification technique requires only a low-energy input, it may create desirable experimental conditions for microencapsulation of unstable substances such as peptides and proteins. This method is promising for making monodisperse microbeads.

Chemistry, Pharmaceutical↗
PubMed1997

Preparation of useful synthetic intermediates of Taxol analogs, cyclooctenone derivatives.

Stereoselective syntheses of omega-(alpha-bromoketo) octanals and nonanal with oxygenated functions and formation of the corresponding eight-membered carbocyclic aldols by subsequent samarium(II)-mediated cyclization are demonstrated. Cyclooctenones deoxygenated at the C2 or C10 position in the taxane framework are prepared by dehydration of the above aldols.

Aldehydes↗
PubMed2006

Production of alpha, omega-alkanediols using Escherichia coli expressing a cytochrome P450 from Acinetobacter sp. OC4.

Our biotransformation using Escherichia coli expressing a cytochrome P450 (CYP) belonging to the CYP153A family from Acinetobacter sp. OC4 produced a great amount of 1-octanol (2,250 mg per liter) from n-octane after 24 h of incubation. This level of production is equivalent to the maximum level previously achieved in biotransformation experiments of alkanes. In addition, the initial production rate of 1-octanol was maintained throughout the entire incubation period. These results indicate that we have achieved the functional and stable expression of a CYP in E. coli for the first time. Further, our biotransformation system showed alpha,omega-diterminal oxidation activity of n-alkanes, and a large amount of 1,8-octanediol (722 mg per liter) was produced from 1-octanol after 24 h of incubation. This is the first report on the bioproduction of alpha,omega-alkanediols from n-alkanes or 1-alkanols.

Acinetobacter↗
PubMed2004

Direct simulation of transmembrane helix association: role of asparagines.

The forces contributing to the association of transmembrane helices in folded membrane proteins have received considerable attention recently. In this study we investigate the importance of hydrogen bonding by studying the effect of a single Asn residue in the center of an otherwise hydrophobic transmembrane peptide using computer simulations. We use the model peptide MS1 which has been derived from the leucine zipper coiled-coil dimer of the transcription factor peptide GCN4-P1. We follow the trajectory of 36 initially monomeric MS1 transmembrane helical peptides in a membrane-mimicking octane layer as they associate into larger structures. These peptides predominately form dimers. The interaction between the polar asparagine residues, capable of simultaneously being a hydrogen-bond donor and acceptor, contributes strongly to the stability of associated helices. Only dimers with interhelical hydrogen bonds form stable structures, whereas aggregates without any hydrogen-bonding interactions form very transient structures. We examine the hydrogen-bonding patterns and find that there are two forms of dimer, one with symmetric hydrogen bonds and one with asymmetric hydrogen bonds. Based on the structures in our simulation we propose a model with a monomer <--> symmetric dimer <--> asymmetric dimer <--> trimer equilibrium.

Amino Acid Sequence↗
PubMed1993

Effect of silane coupling agents with a bisfunctional hydrolyzable group.

Improvement of the siloxane layer on minerals by using a bisfunctional silane, such as 1,6-bis(trichlorosilyl) hexane and 1,8 bis(trichlorosilyl)octane, and the effects on adhesion of methacrylic resin to glass plates treated with the silanes were studied. The tensile bond strength of the resin to the glass plate treated with bisfunctional silane alone was high (about 20MPa) in spite of the fact that the molecule contains no double bonds. Furthermore, a mixture of bisfunctional silane and 3-methacryloxypropyltrichlorosilane showed an excellent effect for tensile bond strength and water-resistance. Based on the results, it is suggested that the better water resistant adhesion of the mixed silane depends on the higher degree of crosslinking in the siloxane phase and on the formation of an interpenetrating polymer network between the siloxane layer and the matrix resin.

Adhesiveness↗
PubMed2006

[Overall migartion testing with alternative fatty food simulants].

Overall migration from commercial samples of food plastics packaging into 95% ethanol and isooctane--the alternative fatty food simulants--was determined. Testing conditions--time and temperature of the contact of food packaging material with food simulants reflected real or predicted use of given packaging. The analytical methods according to European Standard EN 1186 were used. Test methods by filling the artiecles, total immersion, forming a pouch or using the cell were used for migration as appropriate to allow contact with liquid food simulant only this surface which will come into the contact with food during normal use of the product. The overall migration from the samples of the tested products into both food simulants (95% ethanol and iso-octane) was well below the limit (10 mg/dm2), except of the migration from plasticized PVC films which markedly exceeded above limit, showing that these films must not be used for packaging of food containing fat. Application of food simulants as a alternative to olive oil markedly shortens analytical procedure and reduces workload, both important in routine testing.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

[Comparative study of normal and myelogenic immunoglobulin G in monomolecular layers at air-water and oil-water interface].

Orientation of normal and 12 abnormal immunoglobulins G (IgG) isolated from serum of patients with multiple myeloma in monomolecular layers at 0.15 M NaCl--air and 0.15 M NaCl--octane interfaces has been studied. Majority of abnormal proteins was found to be oriented vertically at phase border of both types unlike normal human IgG which had horizontal orientation. Abnormal IgG differed from the normal one also by lower resistance to surface denaturation at air--water interface. Thus the monomolecular layer method was demonstrated to be capable of distinguishing normal and abnormal IgG.

Air↗
PubMed1993

Action of some new insect growth regulators on mosquito vectors. Part II: Geraniol based diethers.

Biological activity of saturated diethers viz. 1-benzyloxy/phenoxy-8-alkoxy and 1-alkoxy-8-benzyloxy-3,7-dimethyl-1, 8-octanes (IIa-IIq) prepared from Geraniol, were studied on three mosquito species and the bug Dysdercus koenigii. These diethers exhibited oviposition deterrent and developmental inhibition activities of greater magnitudes than the compounds based on citronellol reported in Part I of this paper. Some of these new compounds inhibit development of mosquitoes at 0.05 ppm and deter oviposition at 0.05 per cent doses. Tests were extended to field simulated conditions in selected cases.

Acyclic Monoterpenes↗