Regressões lineares em geocronologia: isócronas, errócronas e pseudoisócronas

Several methods of linear regression reported in the literature for use in geochonology are discussed in order to guide geochronologists in the selection of an adequate model and also to distinguish among isochrons, errorchrons and pseudoisochrons. For Rb/Sr isochron methods, at least 6 models or statistical treatments are available, each one with its peculiarities. Based in two examples, we show that for cases when the experimental data points scatter within limits determined by the experimental errors, and using or not the weighted regression treatment, the resultant parameters are essentially concordant. The estimates of associated error, however especially for initial ratios, show variations by up to a factor of 7, depending upon the statistical procedure. In view of this fact and on the basis of simulated test data, we propose not only more adequate models, but also general criteria that must be observed in the selection of samples in order to obtain an isochron. If the data to be regressed show a scatter in excess of experimental error for geological reasons (open system), four regression models are available to treat the parameters defined in these cases as errorchrons. These models are briefly discussed in terms of their applications. In the Pb/U methods, in which the usual regression treatment is applied to obtain the best-fit line, some additional peculiarities are pointed outDiversos métodos de regressão linear propostos na literatura, para fins geocronológicos, são discutidos de modo a orientar os geocronólogos na escolha de modelos adequados e também distinguir entre isócronas, errócronas ou pseudoisócronas. No caso do método isocrôni co Rb/Sr, são disponíveis pelo menos 6 modelos ou abordagens estatísticas, cada qual com peculiaridades específicas. Exemplifica-se o caso em que os pontos se alinham dentro dos erros experimentais e utilizando modelos, adequados ou não, que empregam a técnica de pondera ção dos pontos, os parâmetros resultantes são praticamente concordantes, porém os erros podem variar até por um fator tão alto quanto 7, conforme a formulação estatística proposta. Em vista deste fato, propõem-se, com base também em exemplos, os modelos mais adequados e também critérios gerais que devem ser observados até na seleção de amostras para a obtenção de isócronas. Nos casos em que os pontos não se alinham dentro dos erros experimentais, por causas geológicas (sistema aberto), são abordados 4 dos modelos sugeridos e é feita também uma discussão em que casos seriam aplicáveis. No método da concórdia Pb/U, em que as regressões usuais também são aplicáveis para determinar a melhor reta, algumas particularidades adicionais são discutida

Identification of cytochrome P450 monooxygenase genes from the white-rot fungus Phlebia brevispora

Three cytochrome P450 monooxygenase (CYP) genes, designated pb-1, pb-2 and pb-3, were isolated from the white-rot fungus, Phlebia brevispora, using reverse transcription PCR with degenerate primers constructed based on the consensus amino acid sequence of eukaryotic CYPs in the O2-binding, meander and heme-binding regions. Individual full-length CYP cDNAs were cloned and sequenced, and the relative nucleotide sequence similarity of pb-1 (1788 bp), pb-2 (1881 bp) and pb-3 (1791 bp) was more than 58%. Alignment of the deduced amino acid (aa) sequences of pb-1-pb-3 showed that these three CYPs belong to the same family with > 40% aa sequence similarity, and pb-1 and pb-3 are in the same subfamily, with > 55% aa sequence similarity. Furthermore, pb-1-pb-3 appeared to be a subfamily of CYP63A (CYP63A1-CYP63A4), found in Phanerochaete chrysosporium. The phylogenetic tree constructed by 500 bootstrap replications using the neighbor-joining method showed that the evolutionary distance between pb-1 and pb-3 was shorter than that between pb-2 and pb-1 (or pb-3). Exon-intron analysis of pb-1 and pb-3 showed that both genes have nearly the same number, size and order of exons and the types of introns, also indicating both genes appear to be evolutionarily close. It is interesting that the transcription level of pb-3 was evidently increased above the pb-1 transcription level by exposure to 12 coplanar PCB congeners and 2,3,7,8-tetrachlorodibenzo-p-dioxin, though the two genes were evolutionarily close

Um sistema nacional de aquisição e processamento de dados acoplado "on line" ao espectrômetro de massa de fonte sólida TH-5 (Varian Mat)

A VARIAN MAT solid source mass spectrometer, varían model MAT TH-5, used for geochronological applications has been coupled on line to a 16-bit HP-9825B computer. An appropriate digital voltimeter and interface, both supplied by Hewlett-Packard, complete the system. The developed prototype allows, through peak switching of 8 channels controlled by a Hall effect probe, isotopic analyses of all the elements which can be carried out by the thermal ionization method. This system has been used since 1983 with success, and the strontium measurements performed on 2 carbonate standards NBS-987 and SrN (E&A) agree, within experimental error, with results obtained in modem instruments. A similar system, with the same performance capabilities as the one described above, using an Apple computer and peripherals available in Brazil, has also been developed. The developed interface is provided with outputs to control external devices and accessories like solenoid valves, vacuum systems, scales, etc, common is mass spectrometry. The software, available in HPL and Applesoft languages, is provided with dinamic interference correction, Dodson's interpolation technique, rejection of the spurious ratios and computes all the common statistical parameters.Um espectrômetro de massa de fonte sólida da VARIAN MAT, modelo TH-5, utilizado em aplicações geocronológicas, foi acoplado "on line" ao microcomputador HP-9825B de 16 bits, tendo um voltímetro digital e interfaces apropriadas da Hewlett-Packard. O protótipo desenvolvido permite, através da técnica de "peak switching" de 8 canais controlados por uma sonda de efeito Hall, medidas isotópicas de todos os elementos analisáveis pelo método de ionização térmica. O sistema utilizado desde 1983, com amplo sucesso, rivaliza com os sistemas modernos conforme medidas efetuadas em 2 carbonatos padrões de estrôncio NBS-987 e SrN (E & A). Experiência semelhante, utilizando um microcomputador da linha Apple, periféricos e interface apropriados e inteiramente nacionais desenvolvidos para o sistema, reproduziu, de forma bastante adequada, a performance anterior. A interface desenvolvida, pela sua versatilidade, pode acionar periféricos e acessórios como válvulas solenóides, sistemas de vácuo, sistema de troca de escala, etc, operações comuns na espectrometria. O software, desenvolvido nas linguagens HPL e Applesoft, é provido de correção de interferência dinâmica, técnica de interpolação de Dodson, rejeição de razões espúrias e cálculos de todos os parâmetros estatísticos normais

環境汚染物質のバイオレメディエーション

NCBIデータベース上のT. versicolor由来の8種類のラッカーゼ遺伝子を，それらの相同性により4つのグループ(Lac1遺伝子，Lac2遺伝子，Lac3遺伝子およびLac4遺伝子)に分け，これらをクローニングするための4対のプライマーを作製した。RT-PCRの結果，これら4種類の遺伝子に相当すると考えられる完全長cDNAを獲得した。4種類の遺伝子の塩基配列を比較したところ，互いの相同性は75%以下となった。これらの遺伝子がコードするタンパク質はラッカーゼ特有の4か所の銅原子結合部位を保存していることが確認された。これらを麹菌A. oryzaeに導入した結果，基質のABTSを酸化してラッカーゼ活性を示す形質転換体が獲得された。以降の実験は，高い酵素活性が得られたLac1およびLac4について行った。形質転換A. oryzaeの培養液から陰イオン交換クロマトグラフィーで精製した酵素の等電点電気泳動では，Lac1は等電点4.0を最大値とする複数バンドが，Lac4は3.6の単一バンドが確認された。　エストロゲン作用等を示し，内分泌かく乱物質の一つと危惧されている6種類のHO-PCBの代謝試験では，4塩素化HO-PCBの2種類の同族体のうち，4-OH-2\u27,3，5,5\u27-TeCBの方が4-OH-2\u27,3\u27,4\u27,5\u27-TeCBよりも強く代謝を受けた。また，4-OH-2\u27,3,5,5\u27-TeCBについてはLac4の方がLac1よりも高い代謝活性を示し，4-OH-2\u27,3\u27,4\u27,5\u27-TeCBについては逆にLac1の方が代謝活性が高く，アイソフォーム間で基質特異性の違いが見られた。　また，ラッカーゼと5塩素化HO-PCBの反応から，PCB同士が結合した二量体の中間代謝物2物質が初めて同定され，そのうちの一種類は水酸基を介してC-O結合しており，他方は，ベンゼン環同士がC-C結合した二量体であることが示唆された。The white-rot fungus T. versicolor UAMH 8272 produced two groups of laccases, each of which included several isoforms showing different isoelectric points (pI). Group 1 and group 2 laccases respectively displayed higher pI 5-6 and lower pI 3-4. Of the four cloned full-length laccase cDNAs. Lac 1 and Lac 4 were expressed in the heterologous protein expression system using Aspergillus oryzae. The measured pI of each Lac 1 and Lac 4 expressed in A. oryzae was lower than that of pI predicted from the amino acid composition. With this regard, isoelectric focusing of Lac 1 showed the presence of multiple protein bands in the 3.0-4.0 pI range, although the predicted pI value of Lac 1 was 4.7. Similarly, Lac 4 exhibited a pI value which was lower than that predicted (3.6 vs. 4.3, respectively). In all tested hydroxyPCBs, higher chlorinated hydroxyPCBs were less susceptible to in vitro degradation by laccase than lower chlorinated hydroxyPCBs. Although Lac 4 showed a generally higher activity than Lac 1, the two laccases were characterized by quite different substrate specificity toward two hydroxy-tetrachlorobiphenyl congeners. Two metabolites were obtained from the metabolism of hydroxy-pentachlorobiphenyl: a 10 chlorine-substituted dimer with a C-O bond, and one with a C-C bond

Expression of a fungal laccase fused with a bacterial cellulose-binding module improves the enzymatic saccharification efficiency of lignocellulose biomass in transgenic Arabidopsis thaliana

Delignification is effective for improving the saccharification efficiency of lignocellulosic biomass materials. We previously identified that the expression of a fungal laccase (Lac) fused with a bacterial cellulose-binding module domain (CBD) improved the enzymatic saccharification efficiency of rice plants. In this work, to evaluate the ability of the Lac-CBD fused chimeric enzyme to improve saccharification efficiency in a dicot plant, we introduced the chimeric gene into a dicot model plant, Arabidopsis thaliana. Transgenic plants expressing the Lac-CBD chimeric gene showed normal morphology and growth, and showed a significant increase of enzymatic saccharification efficiency compared to control plants. The transgenic plants with the largest improvement of enzymatic saccharification efficiency also showed an increase of crystalline cellulose in their cell wall fractions. These results indicated that expression of the Lac-CBD chimeric protein in dicotyledonous plants improved the enzymatic saccharification of plant biomass by increasing the crystallinity of cellulose in the cell wall

Determination of Cortisol and Dehydroepiandrosterone Levels in Saliva for Screening of Periodontitis in Older Japanese Adults

Background. Recent reports have found a positive relationship between periodontitis and the hormones cortisol and dehydroepiandrosterone (DHEA). We investigated the associations between those levels and periodontitis in never-smokers and smokers of elderly subjects. Subjects and Methods. Cortisol and DHEA levels in saliva were determined in 171 subjects (85 males, 86 females), with clinical examinations including probing depth (PD) and clinical attachment loss (CAL) also performed. Results. Smoking had effects on cortisol and DHEA levels, and those were significantly associated with severe PD and CAL in never-smokers. According to ROC analysis, the cutoff values of cortisol and DHEA to obtain the optimal sensitivity and specificity for detecting severe periodontitis were 2.06 ng/mL and 60.24 pg/mL, respectively, for PD, and 2.12 ng/mL and 61.78 pg/mL, respectively, for CAL. Conclusions. Assessment of hormone levels may be a useful screening method for periodontitis, though limited to never-smokers

Síntese de criptomelana

Cryptomelane was synthetised from several runs by methods whose reproductibility was proved. The best conditions of temperature and pH for the synthesis, the influence of the digestion time on the degree of crystallinity, and the role of the presence of Zn and K ions in the cryptomelane structure as a function of aging of the mineral in contact with the mother solution, were studied. By reduction of KMnO4 with HC1 or Zn/H2 SO4 , the highest degree of crystallinity was found at temperatures above 60ºC in an extended digestion time. The behavior of constituent ions as a function of digestion time indicates that the crystallinity of the cryptomelane is improved by increasing incorporation of K and Mn (IV) ions and decreasing of Mn (II) content, H2O and Zn ions. The probable mechanism of cryptomelane formation is thought to occur under conditions of low pH with K+ present, nucleation being induced mainly by H3O+.Foram efetuadas dezenas de sínteses de criptomelanas por métodos de reprodutibilidade testada e comprovada. Estudou-se a melhor temperatura de síntese, a influência do tempo de digestão no grau de cristalinidade, pH e a influência da incorporação de íons Zn e K na estrutura da criptomelana em função do tempo de envelhecimento do mineral em contato com a solução nutriente. As sínteses foram obtidas pela redução de KMnO4 com HC1 e com Zn/H2SO4, obtendo-se melhor grau de cristalinidade em temperaturas superiores a 60ºC e tempo de digestão prolongado. O estudo do comportamento dos íons constituintes da criptomelana em função do tempo de digestão indicou que o aperfeiçoamento cristalino leva a um acréscimo dos íons K, Mn (IV) e diminuição de Mn (II), H2O+ e Zn. Este estudo permitiu estabelecer um provável mecanismo de formação da criptomelana, que deve ocorrer em condições de pH baixos e presença de K+, sendo a nucleação induzida principalmente através dos cátions oxônios