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1.
Rev. argent. dermatol ; 104: 1-10, ene. 2023. graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1431487

RESUMO

Resumen El melanoma primariovariedad rabdoide es unapresentación pocofrecuente.Reconocido como un subtipo histopatológico distinto de melanoma maligno generalmente observado en tumores metastásicos o recurrentes.El diagnóstico definitivo requiere el estudio de inmunomarcación y la identificación de células neoplásicas con marcadores melanocíticos. Clínicamente se han reportado mayormente de tipo nodular y amelanótico.


Summary Rhabdoid melanoma has been recognized as a histopathological subtype of malignant melanoma. It generally presents as a recurrent tumor, so its presentation as a primary lesion is infrecuent.Definitive diagnosis requires the study of immunostaining and the identification of neoplastic cells with melanocytic markers. Clinically, mostly nodular and amelanotic types have been reported.

2.
Phys Chem Chem Phys ; 21(46): 25626-25634, 2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31720634

RESUMO

The new capacity of X-ray free-electron laser (XFEL) facilities to produce multi-color X-ray femtosecond pulses paves the way to explore ultrafast phenomena in matter induced by X-ray photons. In the present study, we exploit the site-selectivity and the high temporal resolution of a two-color X-ray femtosecond pump-probe sequence to investigate the isomerization of formamide. The pump pulse excites a particular atomic site in the molecule, while the probe pulse captures changes in the chemical environment at a remote atomic site. The response of the system is found to strongly depend on the nature of the excited site, and the core excitation provides selective control over chemical bond breaking. In particular, we show that the N1s → π* transition can induce the isomerization reaction in formamide and demonstrate the possibility to observe in real time hydrogen migration by measuring the chemical shifts with the X-ray probe pulse. This work opens a unique prospect for X-ray-induced photochemistry at XFEL facilities.

3.
Int J Food Microbiol ; 299: 8-22, 2019 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-30933686

RESUMO

In this study, a collection of 298 wild strains of lactic acid bacteria (LAB) isolated from raw goat milk cheeses, belonging to 8 genera and 24 species, was investigated for their ability to generate volatile compounds. Sensory evaluation showed that goat milk cultures of Leuconostoc and Lactococcus strains reached the highest scores for dairy odour attributes. Fifty six LAB strains with the highest sensory evaluation scores (one per each ten, or fraction, of those belonging to the same species) were selected for gas chromatography-mass spectrometry (GC-MS) analysis. A total of 34 volatile compounds (five carboxylic acids, eleven alcohols, six aldehydes, six ketones, one ester, and five miscellaneous compounds) were detected in lactic curds made with each one of 56 selected LAB strains. The number of volatile compounds in individual curds varied from 15 to 33 while the total abundance of volatile compounds in individual curds ranged from 1.98- to 17.50-fold the total abundance in uninoculated curd. Major differences in volatile generation were related to amino acid catabolism.


Assuntos
Queijo/microbiologia , Lactobacillales/metabolismo , Álcoois/análise , Aldeídos/análise , Animais , Ésteres/análise , Cromatografia Gasosa-Espectrometria de Massas , Cabras , Cetonas/análise , Leuconostoc , Odorantes/análise , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/metabolismo
4.
Food Res Int ; 99(Pt 3): 1002-1010, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28865610

RESUMO

The volatile fraction of dehydrated edible seaweeds belonging to seven species (Himanthalia elongata, Laminaria ochroleuca, Palmaria palmata, Porphyra umbilicalis, Saccharina latissima, Ulva lactuca and Undaria pinnatifida) was analyzed by gas chromatography-mass spectrometry, after solid-phase microextraction of samples. Thirty-six hydrocarbons, 34 ketones, 28 aldehydes, 23 alcohols, 8 carboxylic acids, 6 halogenated compounds, 4 furans, 3 esters, 2 sulphur compounds, 2 pyrazines, 1 pyridine and 1 amine were detected among the 151 volatile compounds found in seaweeds. There were significant differences between seaweed species for all the volatile compounds. Hydrocarbons reached their highest levels in U. pinnatifida, ketones in P. umbilicalis, aldehydes in P. palmata and P. umbilicalis, alcohols in P. umbilicalis, carboxylic acids in S. latissima, and halogenated compounds in L. ochroleuca and S. latissima. Sensory analysis revealed that P. palmata, U. lactuca and H. elongata were the seaweeds showing the most potent seafood odour and seaweed odour characteristics.


Assuntos
Clorófitas/química , Desidratação , Manipulação de Alimentos/métodos , Odorantes/análise , Phaeophyceae/química , Plantas Comestíveis/química , Rodófitas/química , Alga Marinha/química , Compostos Orgânicos Voláteis/análise , Clorófitas/classificação , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Masculino , Percepção Olfatória , Phaeophyceae/classificação , Plantas Comestíveis/classificação , Análise de Componente Principal , Rodófitas/classificação , Alga Marinha/classificação , Olfato , Microextração em Fase Sólida , Especificidade da Espécie
6.
Int J Food Microbiol ; 241: 298-307, 2017 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-27835773

RESUMO

The microbiota of Serrano dry-cured ham of different chemical composition, subjected or not to high-pressure processing (HPP), was investigated using culture-dependent and culture-independent methods. Microbial counts were submitted to analysis of variance with physicochemical parameters (aw, NaCl concentration, salt-in-lean ratio and intramuscular fat content) or HPP as main effects. In untreated hams, physicochemical parameters significantly affected counts of aerobic mesophiles, psychrotrophs, and moulds and yeasts. NaCl concentration and fat content influenced the levels of four and three of the five studied microbial groups, respectively, whereas no influence of aw was stated. The HPP treatment had a significant effect on counts of all investigated microbial groups. Culture-independent methods showed the presence of bacteria such as Staphylococcus equorum, Staphylococcus succinus, Bacillus subtilis and Cellulosimicrobium sp., moulds like Penicillium commune, Aspergillus fumigatus, Sclerotinia sclerotiorum, Eurotium athecium and Moniliella mellis, and yeasts like Debaryomyces hansenii and Candida glucosophila. Absence of B. subtilis bands and weaker bands of E. athecium were recorded for HPP-treated hams. The higher microbial levels found in lean ham might result in a quicker deterioration. HPP treatment confirmed its suitability as a procedure to control spoilage microorganisms. DGGE did not seem to be sensitive enough to highlight changes caused by HPP treatment in the microbiota of ham, but contributed to the detection of microbial species not previously found in ham.


Assuntos
Bactérias/isolamento & purificação , Conservação de Alimentos/métodos , Fungos/isolamento & purificação , Produtos da Carne/microbiologia , Microbiota , Animais , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Manipulação de Alimentos , Conservação de Alimentos/instrumentação , Fungos/genética , Fungos/crescimento & desenvolvimento , Produtos da Carne/análise , Pressão , Cloreto de Sódio/análise , Suínos
7.
Meat Sci ; 122: 101-108, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27513944

RESUMO

One hundred and three volatile compounds were detected by solid-phase microextraction followed by gas chromatography-mass spectrometry in 30 ripened Serrano dry-cured hams, submitted or not to high pressure processing (HPP) and afterwards held for 5months at 4°C. The effect of ham physicochemical parameters and HPP (600MPa for 6min) on volatile compounds was assessed. Physicochemical parameters primarily affected the levels of acids, alcohols, alkanes, esters, benzene compounds, sulfur compounds and some miscellaneous compounds. Intramuscular fat content was the physicochemical parameter with the most pronounced effect on the volatile fraction of untreated Serrano ham after refrigerated storage, influencing the levels of 38 volatile compounds while aw, salt content and salt-in-lean ratio respectively influenced the levels of 4, 4 and 5 volatile compounds. HPP treatment affected 21 volatile compounds, resulting in higher levels of alkanes and ketones and lower levels of esters and secondary alcohols, what might affect Serrano ham odor and aroma after 5months of refrigerated storage.


Assuntos
Manipulação de Alimentos/métodos , Conservação de Alimentos/métodos , Qualidade dos Alimentos , Produtos da Carne/análise , Compostos Orgânicos Voláteis/análise , Animais , Gorduras na Dieta/análise , Cromatografia Gasosa-Espectrometria de Massas , Pressão , Cloreto de Sódio na Dieta , Microextração em Fase Sólida , Sus scrofa
8.
Nat Commun ; 7: 11652, 2016 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-27212390

RESUMO

New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site.

9.
J Dairy Sci ; 96(12): 7500-10, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24140328

RESUMO

Enzyme-rich cheeses are prone to over-ripening during refrigerated storage. Blue-veined cheeses fall within this category because of the profuse growth of Penicillium roqueforti in their interior, which results in the production of highly active proteinases, lipases, and other enzymes responsible for the formation of a great number of flavor compounds. To control the excessive formation of free fatty acids (FFA) and volatile compounds, blue-veined cheeses were submitted to high-pressure processing (HPP) at 400 or 600 MPa on d 21, 42, or 63 after manufacture. Cheeses were ripened for 30d at 10°C and 93% relative humidity, followed by 60 d at 5°C, and then held at 3°C until d 360. High-pressure processing influenced the concentrations of acetic acid and short-chain, medium-chain, and long-chain FFA. The effect was dependent on treatment conditions (pressure level and cheese age at the time of treatment). The lowest concentrations of acetic acid and FFA were recorded for cheeses treated at 600 MPa on d 21; these cheeses showed the lowest esterase activity values. Acetic acid and all FFA groups increased during ripening and refrigerated storage. The 102 volatile compounds detected in cheese belonged to 10 chemical groups (5 aldehydes, 12 ketones, 17 alcohols, 12 acids, 35 esters, 9 hydrocarbons, 5 aromatic compounds, 3 nitrogen compounds, 3 terpenes, and 1 sulfur compound). High-pressure processing influenced the levels of 97 individual compounds, whereas 68 individual compounds varied during refrigerated storage. Total concentrations of all groups of volatile compounds were influenced by HPP, but only ketones, acids, esters, and sulfur compounds varied during refrigerated storage. The lowest total concentrations for most groups of volatile compounds were recorded for the cheese pressurized at 600 MPa on d 21. A principal component analysis combining total concentrations of groups of FFA and volatile compounds discriminated cheeses by age and by the pressure level applied to HPP cheeses.


Assuntos
Queijo/análise , Indústria de Laticínios/métodos , Manipulação de Alimentos/métodos , Leite/química , Penicillium/metabolismo , Álcoois/análise , Aldeídos/análise , Animais , Queijo/microbiologia , Ésteres/análise , Ácidos Graxos não Esterificados/análise , Cetonas/análise , Lipólise , Penicillium/crescimento & desenvolvimento , Pressão , Análise de Componente Principal , Ovinos
10.
J Dairy Sci ; 96(8): 4816-29, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23706489

RESUMO

Penicillium roqueforti plays an important role in the ripening of blue-veined cheeses, mostly due to lactic acid consumption and to its extracellular enzymes. The strong activity of P. roqueforti proteinases may bring about cheese over-ripening. Also, free amino acids at high concentrations serve as substrates for biogenic amine formation. Both facts result in shorter product shelf-life. To prevent over-ripening and buildup of biogenic amines, blue-veined cheeses made from pasteurized ovine milk were high-pressure treated at 400 or 600 MPa after 3, 6, or 9 wk of ripening. Primary and secondary proteolysis, biogenic amines, and sensory characteristics of pressurized and control cheeses were monitored for a 90-d ripening period, followed by a 270-d refrigerated storage period. On d 90, treatments at 400 MPa had lowered counts of lactic acid bacteria and P. roqueforti by less than 2 log units, whereas treatments at 600 MPa had reduced lactic acid bacteria counts by more than 4 log units and P. roqueforti counts by more than 6 log units. No residual α-casein (CN) or κ-CN were detected in control cheese on d 90. Concentrations of ß-CN, para-κ-CN, and γ-CN were generally higher in 600 MPa cheeses than in the rest. From d 90 onwards, hydrophilic peptides were at similar levels in pressurized and control cheeses, but hydrophobic peptides and the hydrophobic-to-hydrophilic peptide ratio were at higher levels in pressurized cheeses than in control cheese. Aminopeptidase activity, overall proteolysis, and free amino acid contents were generally higher in control cheese than in pressurized cheeses, particularly if treated at 600 MPa. Tyramine concentration was lower in pressurized cheeses, but tryptamine, phenylethylamine, and putrescine contents were higher in some of the pressurized cheeses than in control cheese. Differences in sensory characteristics between pressurized and control cheeses were generally negligible, with the only exception of treatment at high pressure level (600 MPa) at an early ripening stage (3 wk), which affected biochemical changes and sensory characteristics.


Assuntos
Queijo/normas , Aminoácidos/análise , Animais , Aminas Biogênicas/análise , Queijo/análise , Queijo/microbiologia , Qualidade dos Alimentos , Tecnologia de Alimentos/métodos , Hipopituitarismo , Pressão , Proteólise
11.
Phys Rev Lett ; 109(16): 163002, 2012 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-23215074

RESUMO

We study vibrational excitations, dissociation, and ionization of H(2)(+) in few-cycle laser pulses over a broad wavelength regime. Our results of numerical simulations supported by model calculations show a many orders-of-magnitude enhancement of vibrational excitation and dissociation (over ionization) of the molecular ion at infrared wavelengths. The enhancement occurs without any chirping of the pulse, which was previously applied to take account of the anharmonicity of the molecular vibrations. The effect is related to strong-field two- and higher-order photon transitions between different vibrational states.

12.
Braz. j. med. biol. res ; 45(9): 806-810, Sept. 2012. ilus, tab
Artigo em Inglês | LILACS | ID: lil-646325

RESUMO

The aim of this study was to investigate the influence of image resolution manipulation on the photogrammetric measurement of the rearfoot static angle. The study design was that of a reliability study. We evaluated 19 healthy young adults (11 females and 8 males). The photographs were taken at 1536 pixels in the greatest dimension, resized into four different resolutions (1200, 768, 600, 384 pixels) and analyzed by three equally trained examiners on a 96-pixels per inch (ppi) screen. An experienced physiotherapist marked the anatomic landmarks of rearfoot static angles on two occasions within a 1-week interval. Three different examiners had marked angles on digital pictures. The systematic error and the smallest detectable difference were calculated from the angle values between the image resolutions and times of evaluation. Different resolutions were compared by analysis of variance. Inter- and intra-examiner reliability was calculated by intra-class correlation coefficients (ICC). The rearfoot static angles obtained by the examiners in each resolution were not different (P > 0.05); however, the higher the image resolution the better the inter-examiner reliability. The intra-examiner reliability (within a 1-week interval) was considered to be unacceptable for all image resolutions (ICC range: 0.08-0.52). The whole body image of an adult with a minimum size of 768 pixels analyzed on a 96-ppi screen can provide very good inter-examiner reliability for photogrammetric measurements of rearfoot static angles (ICC range: 0.85-0.92), although the intra-examiner reliability within each resolution was not acceptable. Therefore, this method is not a proper tool for follow-up evaluations of patients within a therapeutic protocol.


Assuntos
Adulto , Feminino , Humanos , Masculino , Pé/anatomia & histologia , Pé/fisiologia , Variações Dependentes do Observador , Fotogrametria , Valores de Referência , Reprodutibilidade dos Testes
13.
Braz J Med Biol Res ; 45(9): 806-10, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22911379

RESUMO

The aim of this study was to investigate the influence of image resolution manipulation on the photogrammetric measurement of the rearfoot static angle. The study design was that of a reliability study. We evaluated 19 healthy young adults (11 females and 8 males). The photographs were taken at 1536 pixels in the greatest dimension, resized into four different resolutions (1200, 768, 600, 384 pixels) and analyzed by three equally trained examiners on a 96-pixels per inch (ppi) screen. An experienced physiotherapist marked the anatomic landmarks of rearfoot static angles on two occasions within a 1-week interval. Three different examiners had marked angles on digital pictures. The systematic error and the smallest detectable difference were calculated from the angle values between the image resolutions and times of evaluation. Different resolutions were compared by analysis of variance. Inter- and intra-examiner reliability was calculated by intra-class correlation coefficients (ICC). The rearfoot static angles obtained by the examiners in each resolution were not different (P > 0.05); however, the higher the image resolution the better the inter-examiner reliability. The intra-examiner reliability (within a 1-week interval) was considered to be unacceptable for all image resolutions (ICC range: 0.08-0.52). The whole body image of an adult with a minimum size of 768 pixels analyzed on a 96-ppi screen can provide very good inter-examiner reliability for photogrammetric measurements of rearfoot static angles (ICC range: 0.85-0.92), although the intra-examiner reliability within each resolution was not acceptable. Therefore, this method is not a proper tool for follow-up evaluations of patients within a therapeutic protocol.


Assuntos
Pé/anatomia & histologia , Adulto , Feminino , Pé/fisiologia , Humanos , Masculino , Variações Dependentes do Observador , Fotogrametria , Valores de Referência , Reprodutibilidade dos Testes
14.
J Dairy Sci ; 95(7): 3501-13, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22720909

RESUMO

Hispánico cheese is a semihard variety made from a mixture of cow and ewe milks. Production of ewe milk declines in summer and autumn. To surmount the seasonal shortage of ewe milk and prevent the inactivation of milk enzymes by pasteurization, curd made in spring from ewe raw milk was pressurized at 200 and 300 MPa and stored frozen for 4 mo. Thawed ewe milk curds were added to fresh curd made from pasteurized cow milk for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same proportions as those used for experimental cheeses. Experimental cheeses exhibited lower dry matter content, higher aminopeptidase activity and total free amino acid concentration, and higher levels of acetic and propionic acids, aldehydes, alcohols, and esters compared with control cheese. In contrast, the concentration of total free fatty acids and ketones and the levels of textural parameters were significantly higher in control cheese. The use of ewe raw milk curd pressurized at 200 and 300 MPa, stored frozen and thawed for Hispánico cheese manufacture, was generally beneficial for cheese characteristics and increased cheese yield because of the lower dry matter content of experimental cheeses.


Assuntos
Queijo , Leite/metabolismo , Animais , Bovinos , Queijo/microbiologia , Queijo/normas , Feminino , Microbiologia de Alimentos , Conservação de Alimentos/métodos , Tecnologia de Alimentos/métodos , Pasteurização/métodos , Pressão , Ovinos
15.
J Dairy Sci ; 94(10): 4766-76, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21943728

RESUMO

To overcome the seasonal shortage of goat milk in mixed milk cheese manufacture, pasteurized goat milk curd and high-pressure-treated raw goat milk curd manufactured in the spring were held at -24 °C for 4 mo, thawed, and mixed with fresh cow milk curd for the manufacture of experimental cheeses. Control cheeses were made from a mixture of pasteurized cow and goat milk. The microbiota of experimental and control cheeses was studied using culture-dependent and culture-independent techniques. Bacterial enumeration by classical methods showed lactic acid bacteria to be the dominant population in both control and experimental cheeses. In total, 681 isolates were grouped by partial amplified rDNA restriction analysis (ARDRA) into 4 groups and identified by 16S rRNA gene sequencing as Lactococcus lactis ssp. lactis (563 isolates), Leuconostoc pseudomesenteroides (72 isolates), Lactobacillus spp. (34 isolates), and Lc. lactis ssp. cremoris (12 isolates). Temporal temperature gradient gel electrophoresis (TTGE) analysis of cheese showed (1) the predominance of Lc. lactis in all cheeses; (2) the presence of Leu. pseudomesenteroides population in all cheeses from d 15 onward; (3) the presence of a Lactobacillus plantarum population in control cheese until d 15 and in experimental cheeses throughout the ripening period. Due to the most diverse and complete set of peptidases present in the genus Lactobacillus, the prevalence of this population in experimental cheeses could give rise to differences in cheese flavor between experimental and control cheeses.


Assuntos
Fenômenos Fisiológicos Bacterianos , Queijo/microbiologia , Manipulação de Alimentos/métodos , Armazenamento de Alimentos , Leite/microbiologia , Animais , Bactérias/enzimologia , Bactérias/genética , Bactérias/isolamento & purificação , Carga Bacteriana , Biodiversidade , Bovinos , Queijo/análise , Manipulação de Alimentos/normas , Congelamento , Cabras , Concentração de Íons de Hidrogênio , Lactobacillus/enzimologia , Lactobacillus/genética , Lactobacillus/isolamento & purificação , Leuconostoc/genética , Leuconostoc/isolamento & purificação , RNA Ribossômico 16S , Fatores de Tempo
16.
J Dairy Sci ; 93(7): 2896-905, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20630207

RESUMO

Hispánico cheese is manufactured in Spain from a mixture of cow and ewe milk. Production of ewe milk varies throughout the year, with a peak in spring and a valley in summer and autumn. To overcome this seasonal shortage, curd from spring ewe milk may be frozen and used for cheese manufacture some months later. In the present work, ewe milk curds pressed for 15, 60, or 120 min were held at -24 degrees C for 4 mo, thawed, cut to 1-mm pieces, and mixed with fresh cow milk curd for the manufacture of experimental Hispánico cheeses. Control cheese was made from a mixture of pasteurized cow and ewe milk in the same (80:20) proportion. Cheeses, made in duplicate experiments, were analyzed throughout a 60-d ripening period. No significant differences between cheeses were found for lactic acid bacteria counts, dry matter content, hydrophilic peptides, 47 out of 68 vol.tile compounds, texture, and flavor characteristics. On the other hand, differences of minor practical significance between experimental and control cheeses, unrelated to the use of frozen ewe milk curd or the pressing time of ewe milk curd, were found for pH value, aminopeptidase activity, proteolysis, hydrophobic peptides, free amino acids, free fatty acids, and the remaining 21 vol.tile compounds. It may be concluded that the use of frozen ewe milk curd in the manufacture of Hispánico cheese does not alter its main characteristics.


Assuntos
Queijo/análise , Manipulação de Alimentos , Proteínas do Leite/metabolismo , Leite/química , Aminoácidos/análise , Aminopeptidases/metabolismo , Animais , Bovinos , Feminino , Alimentos Congelados , Humanos , Concentração de Íons de Hidrogênio , Lipólise , Peptídeos/análise , Ovinos , Paladar , Fatores de Tempo
17.
Opt Express ; 18(4): 3660-71, 2010 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-20389376

RESUMO

Intense laser ionization expands Einstein's photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete description of photoionization by OAM photons, including new selection rules involving more than one unit of angular momentum. We explore theoretically the interaction of a single electron atom located at the center of an intense ultraviolet beam bearing OAM, envisaging new scenarios for quantum optics.


Assuntos
Elétrons , Modelos Teóricos , Fótons , Simulação por Computador , Transferência de Energia , Íons , Teoria Quântica
18.
J Ind Microbiol Biotechnol ; 35(4): 213-8, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18188625

RESUMO

During Escherichia coli growth on glucose, uptake exceeds the requirement of flux to precursors and the surplus is excreted as acetate. Beside the loss of carbon source, the excretion of a weak acid may result in increased energetic demands and hence a decreased yield. The deletion of ptsG, the gene coding for one of the components (IICB(Glc)) of the glucose-phosphoenolpyruvate phosphotransferase system (Glc-PTS) reduced glucose consumption and acetate excretion. Induction of protein production at the onset of cultivation decreased growth rate and glucose consumption rate for both the WT and the mutant strains. The mutant strain produced beta-galactosidase at higher rates than the wild-type strain while directing more carbon into biomass and CO(2) and less into acetate.


Assuntos
Escherichia coli/metabolismo , Engenharia Genética , Isopropiltiogalactosídeo/metabolismo , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/genética , beta-Galactosidase/metabolismo , Biomassa , Reatores Biológicos , Escherichia coli/genética , Escherichia coli/crescimento & desenvolvimento , Glucose/metabolismo , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/metabolismo
19.
Int J Food Microbiol ; 119(3): 308-13, 2007 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-17905459

RESUMO

Lactococcus lactis AMP15/pAMP31(D471R) is a proteinase negative, lactose negative strain with a modified oligopeptide transport system, and potential as a debittering agent due to its efficient utilization of hydrophobic peptides. Five wild L. lactis strains of dairy origin, which produced cheeses of high flavour quality, were cocultured with L. lactis AMP15/pAMP31(D471R) in an attempt to select adequate combinations of strains for use as defined cheese starters with potential debittering ability. Four of these strains, L. lactis B6, K16, M21 and P21, inhibited growth of L. lactis AMP15/pAMP31(D471R) at a level of 10(6) to 10(7) cfu mL(-1) after 24 h of incubation, even though production of bacteriocin-like compounds could only be proven for L. lactis M21. When L. lactis AMP15/pAMP31(D471R) was cocultured with the fifth strain, L. lactis N22, its growth was significantly (P<0.001) inhibited whereas growth of L. lactis N22 was significantly stimulated. The nature of the interaction was studied and it was established that L. lactis N22 is auxotrophic for folate, a compound produced and excreted by L. lactis AMP15/pAMP31(D471R).


Assuntos
Antibiose , Queijo/microbiologia , Lactococcus lactis/crescimento & desenvolvimento , Lactococcus lactis/fisiologia , Peptídeo Hidrolases/metabolismo , Técnicas de Cocultura , Contagem de Colônia Microbiana , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Lactococcus lactis/enzimologia , Oligopeptídeos/metabolismo , Especificidade da Espécie , Fatores de Tempo
20.
Int J Food Microbiol ; 104(3): 299-307, 2005 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-15975677

RESUMO

Lactic starters used for cheese manufacture play an important role in the production of bitter peptides and their degradation to non-bitter products. The oligopeptide transport system (Opp) of lactococci is essential for milk peptide utilization. The periplasmic substrate binding protein serves to capture the substrate with high affinity and to deliver it to a membrane-bound complex that translocates it inside the cell. Prt(+)- and Lac(+)-derivatives of MG1363 DeltaoppA strains expressing a wild-type MG1363 OppA or a mutant OppA with a single point mutation at residue 471 (OppA(D471R)) from a plasmid were constructed. These strains were used as lactic starters in cheese manufacture to improve flavour quality by removing hydrophobic peptides from the cheese matrix, through their preferential transport by OppA(D471R). Cheeses made with these strains were not significantly different from control cheeses after 1 day of ripening with respect to bacterial counts, pH and proteolysis, and only slight differences were recorded after 9 and 20 days of ripening. HPLC chromatograms of the hydrophilic and hydrophobic peptides present in the water-soluble fraction of experimental cheeses showed significant differences in peptide content as well as in peak profiles. These results suggest a different peptide utilization in the strain expressing OppA(D471R) and make it suitable for use as starter to improve cheese quality.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Queijo/microbiologia , Lactococcus lactis/metabolismo , Lipoproteínas/metabolismo , Mutação , Transporte Biológico , Contagem de Colônia Microbiana , Fermentação , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Lactococcus lactis/genética , Oligopeptídeos/metabolismo , Fatores de Tempo
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