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111.
Silva J Carvalho AS Vitorino R Domingues P Teixeira P Gibbs P 《Protein and peptide letters》2004,11(2):189-194
Protein extraction and the proteome of Lactobacillus delbrueckii subsp. bulgaricus were studied using different stains. The reversible silver staining technique was shown to be more sensitive than the irreversible silver stain. Coomassie colloidal was demonstrated to be as sensitive as reversible silver stain; however, the Coomassie colloidal blue solution developed a higher background and for sample preparation was more time-consuming. 相似文献
112.
Sónia?S.?Leal Miguel?Teixeira Cláudio?M.?GomesEmail author 《Journal of biological inorganic chemistry》2004,9(8):987-996
The ferredoxin from the thermoacidophile Acidianus ambivalens is a representative of the archaeal family of di-cluster [3Fe-4S][4Fe-4S] ferredoxins. Previous studies have shown that these ferredoxins are intrinsically very stable and led to the suggestion that upon protein unfolding the iron-sulfur clusters degraded via linear three-iron sulfur center species, with 610 and 520 nm absorption bands, resembling those observed in purple aconitase. In this work, a kinetic and spectroscopic investigation on the alkaline chemical denaturation of the protein was performed in an attempt to elucidate the degradation pathway of the iron-sulfur centers in respect to protein unfolding events. For this purpose we investigated cluster dissociation, iron release and protein unfolding by complementary biophysical techniques. We found that shortly after initial protein unfolding, iron release proceeds monophasically at a rate comparable to that of cluster degradation, and that no typical EPR features of linear three-iron sulfur centers are observed. Further, it was observed that EDTA prevents formation of the transient bands and that sulfide significantly enhances its intensity and lifetime, even after protein unfolding. Altogether, our data suggest that iron sulfides, which are formed from the release of iron and sulfide resulting from cluster degradation during protein unfolding in alkaline conditions, are in fact responsible for the observed intermediate spectral species, thus disproving the hypothesis suggesting the presence of a linear three-iron center intermediate. Kinetic studies monitored by visible, fluorescence and UV second-derivative spectroscopies have elicited that upon initial perturbation of the tertiary structure the iron-sulfur centers start decomposing and that the presence of EDTA accelerates the process. Also, the presence of EDTA lowers the observed melting temperature in thermal ramp experiments and the midpoint denaturant concentration in equilibrium chemical unfolding experiments, further suggesting that the clusters also play a structural role in the maintenance of the conformation of the folded state. 相似文献
113.
Thirty mesophilic and thermophilic bacteria were isolated from thermobiotically digested sewage sludge in culture medium supplemented with poly-ε-caprolactone (PCL). The ability of each purified isolate to degrade PCL and to produce polymer-degrading extracellular enzymes was assessed. Isolates were characterized based on random amplified polymorphic DNA (RAPD), 16S rDNA sequence-based phylogenetic affiliation and carbohydrate-based nutritional versatility. Mesophilic isolates with ability to degrade PCL were attributed to the genera Acinetobacter, Burkholderia, Pseudomonas, and Staphylococcus. Thermophilic isolates were members of the genus Bacillus. Despite the restricted phylogenetic and genotypic diversity observed for thermophiles, their metabolic versatility and wide range of growth temperatures suggest an important activity of these organisms during the whole composting process. 相似文献
114.
Lip anatomy and its implications for the pollination mechanisms of Bulbophyllum species (Orchidaceae) 总被引:1,自引:0,他引:1
BACKGROUND AND AIMS: The lip structure of six Brazilian and one Asiatic species of Bulbophyllum with wind-assisted fly pollination (B. involutum, B. ipanemense and B. weddellii) and non-wind-assisted fly pollination (B. epiphytum, B. glutinosum, B. regnellii and B. rothschildianum) was studied to investigate the presence of secretory tissues related to these pollination mechanisms. METHODS: The lip study was carried out through scanning electron microscopy (lip surface) and light microscopy (anatomical features). KEY RESULTS: In most of the species studied, the osmophores (odour glands) were located in the lobes and in the upper surface of the lip callus. Differences in the lip structure were observed between the two groups (the presence of a nectary and the extent of osmophore surface), depending on the mechanism of pollination. Nectaries were found in the cavity callus in B. ipanemense, B. involutum and B. weddellii, even though their pollinators were presumably attracted by the instinct to oviposit. CONCLUSIONS: These findings corroborate the hypothesis that, because pollination in these species is dependent on an unpredictable external factor (wind), nectar is necessary to keep the insect in the flower for a long period. Despite the occurrence of a liquid-like nectar in the flowers of B. epiphytum, B. glutinosum, B. regnelli and B. rothschildianum, no anatomical evidence for nectaries was found in the lips of these species, although a similar structure may occur in another region of the flowers. This observation agrees with the fact that pollination by lip movement in the latter species requires only gravity, with no additional mechanism being needed to keep the flies in the flower. 相似文献
115.
An inducible mycelial beta-glucosidase from Scytalidum thermophilum was characterized. The enzyme exhibited a pI of 6.5, a carbohydrate content of 15%, and an apparent molecular mass of about 40 kDa. Optima of temperature and pH were 60 degrees C and 6.5, respectively. The enzyme was stable up to 1 h at 50 degrees C and exhibited a half-life of 20 min at 55 degrees C. The enzyme hydrolyzed p-nitrophenyl-beta-d-glucopyranoside, p-nitrophenyl-beta-d-xylopyranoside, o-nitrophenyl-beta-d-galactopyranoside, p-nitrophenyl-alpha-arabinopyranoside, cellobiose, laminaribiose and lactose. Kinetic studies indicated that the same enzyme hydrolyzed these substrates. Beta-Glucosidase was activated by glucose or xylose at concentration varying from 50 to 200 mM. The apparent affinity constants (K0.5) for glucose and xylose were 36.69 and 43.24 mM, respectively. The stimulatory effect of glucose and xylose on the S. thermophilum beta-glucosidase is a novel characteristic which distinguish this enzyme from all other beta-glucosidases so far described. 相似文献
116.
Lima M Almeida J Teixeira MA Santos AH Queirós ML Fonseca S Moura J Gonçalves M Orfão A Pinto Ribeiro AC 《Journal of biological regulators and homeostatic agents》2004,18(3-4):331-334
Several phenotypic changes have been shown to occur after NK-cell stimulation, involving molecules that have been proved to regulate NK-cell migration into tissues and NK-cell activation and proliferation as well as target cell recognition and killing. Here, we review the reactive phenotypes observed in vivo after acute and chronic NK-cell activation. 相似文献
117.
Talvani A Rocha MO Cogan J Maewal P de Lemos J Ribeiro AL Teixeira MM 《Memórias do Instituto Oswaldo Cruz》2004,99(6):645-649
Global left ventricular (LV) systolic dysfunction is the strongest predictor of morbidity and mortality in Chagas disease. Echocardiography is considered the gold standard for the detection of LV dysfunction, but not always available in endemic areas where chagasic cardiomyopathy is most common. Brain natriuretic peptide (BNP) is a neurohormone that has been recently described as a simple and inexpensive diagnostic and prognostic marker for patients with congestive heart failure. Chagasic patients (n = 63) and non-infected healthy individuals (n = 18) were recruited prospectively and underwent complete clinical examination, echocardiography and 24-h Holter monitoring. BNP was measured from thawed plasma samples using the Triage BNP test. We observed high levels of BNP in association with depression of LV ejection fraction, with increase of LV end-diastolic diameter and with LV premature complexes. An elevated concentration of BNP, defined as a concentration of 60 pg/ml or more, had a sensitivity of 91.7%, specificity of 82.8%, positive predictive value of 52.4%, and negative predictive value of 98% for detecting LV dysfunction (LV ejection fraction < 40%).BNP measurement using a simple, relatively inexpensive and rapid test has a promising role in identifying LV dysfunction associated with chagasic cardiomyopathy. Equally important, patients with Trypanosoma cruzi infection who have low levels of BNP level in plasma have a very low likelihood of severe cardiac involvement, and echocardiography is probably not necessary. 相似文献
118.
Nóbrega OT Santana JM Sturm NR Teixeira AR Campbell DA 《Memórias do Instituto Oswaldo Cruz》2004,99(5):513-516
This work describes the development and functional testing of two episomes for stable transfection of Trypanosoma cruzi. pHygD contained the 5'- and 3'- flanking regions of the gene encoding the cathepsin B-like protease of T. cruzi as functional trans-splicing and polyadenylation signals for the hygR ORF. Evidence is presented to support extrachromosomal maintenance and organization as tandem repeats in transfected parasites. pPac was derived from pHygD by replacement of the entire hygR ORF with a purR coding region. The ability to modify pHygD and the availability of the complete DNA sequence make these plasmids useful tools for the genetic manipulation of T. cruzi. 相似文献
119.
Pereira MM Bandeiras TM Fernandes AS Lemos RS Melo AM Teixeira M 《Journal of bioenergetics and biomembranes》2004,36(1):93-105
Thermophiles are organisms that grow optimally above 50 degrees C and up to approximately 120 degrees C. These extreme conditions must have led to specific characteristics of the cellular components. In this paper we extensively analyze the types of respiratory complexes from thermophilic aerobic prokaryotes. The different membrane-bound complexes so far characterized are described, and the genomic data available for thermophilic archaea and bacteria are analyzed. It is observed that no specific characteristics can be associated to thermophilicity as the different types of complexes I-IV are present randomly in thermophilic aerobic organisms, as well as in mesophiles. Rather, the extensive genomic analyses indicate that the differences concerning the several complexes are related to the organism phylogeny, i.e., to evolution and lateral gene transfer events. 相似文献
120.
The assignment of the trivial name to new isolated or detected brassinosteroid is based on the trivial names of seven different brassinosteroids, with names assigned according to the plant source from which they were first isolated. To avoid some observed mistakes in assigning trivial names to these compounds and the impractical constant usage of their systematic names, we propose a semisystematic nomenclature of brassinosteroids, in which (22R,23R)-2,3,22,23-tetrahydroxy-5-campestane, the trivial name of which is 6-deoxocastasterone, is considered the functional parent compound and is named brassinostane or brassinane. A set of rules for naming the remaining natural brassinosteroids is presented. 相似文献