Genomic and transcriptomic analysis of the streptomycin-dependent Mycobacterium tuberculosis strain 18b.

The ability of Mycobacterium tuberculosis to establish a latent infection (LTBI) in humans confounds the treatment of tuberculosis. Consequently, there is a need to discover new therapeutic agents that can kill M. tuberculosis both during active disease and LTBI. The streptomycin-dependent strain of M. tuberculosis, 18b, provides a useful tool for this purpose since upon removal of streptomycin (STR) it enters a non-replicating state that mimics latency both in vitro and in animal models. The 4.41 Mb genome sequence of M. tuberculosis 18b was determined and this revealed the strain to belong to clade 3 of the ancient ancestral lineage of the Beijing family. STR-dependence was attributable to insertion of a single cytosine in the 530 loop of the 16S rRNA and to a single amino acid insertion in the N-terminal domain of initiation factor 3. RNA-seq was used to understand the genetic programme activated upon STR-withdrawal and hence to gain insight into LTBI. This revealed reconfiguration of gene expression and metabolic pathways showing strong similarities between non-replicating 18b and M. tuberculosis residing within macrophages, and with the core stationary phase and microaerophilic responses. The findings of this investigation confirm the validity of 18b as a model for LTBI, and provide insight into both the evolution of tubercle bacilli and the functioning of the ribosome.

Discriminação quiral por CLAE em carbamatos de polissacarídeos: desenvolvimento, aplicações e perspectivas

The importance of chromatographic separation of enantiomers has been acknowledged. This review surveys the development, application and perspectives of polysaccharide carbamates as chiral stationary phase for HPLC.

Estado da arte da cromatografia gasosa de alta resolução e alta temperatura

The developments in stationary phase synthesis and capillary column technology, have opened new perspectives in analysis of high molecular mass compounds (³600 daltons) and thermolabile organic compounds by High Temperature High Resolution Gas Chromatography (HT-HRGC). HT-HRGC is a new analytical borderline and its application to the analysis of high molecular mass compounds is still in its infancy. The apolar and medium polar gum phases can now be operated at temperatures up to 400-480ºC, being used for the analysis of n-alcanes up to C-100, lipids, oligosaccharides, industrial resins, polyglycerols, cyclodextrins, porphyrins, etc. This technique should play a leading role as a powerful tool, for many different analysis types, in multidisciplinary fields of Science.

Estudo de compostos orgânicos em lixiviado de aterros sanitários por EFS e CG/EM

The main purpose of this work was the qualitative study of organic compounds in landfill leachate. The samples were collected from a sanitary landfill located at Gravataí, a southern Brazilian city, that receive both, industrial and domestic refuse. The samples were submitted to solid phase extraction (SPE) with XAD-4 resin as the stationary phase. The instrumental analysis was performed by Gas Chromatography with a Mass Spectrometry Detector (GC/MSD). The compounds achieved in the SPE extracts were tentatively identified by the GC/MS library. It was found several oxygen and nitrogen compounds like carboxylic acids, ketones, amines and amides. Sulfur compounds and phthalate esters are also identified.

Xerogel p-anisidinapropilsílica: estudo da estabilidade térmica e da resistência à lixiviação com solventes

The xerogel p-anisidinepropylsilica was obtained. This solid presents some residual paraffin and also a small fraction of high organofunctionalized material that was leached in polar solvent. The xerogel purification could be achieved by exhaustively washing with hexane and dichloromethane solvents, or submitting the xerogel to thermal treatment up to 300 ºC, in vacuum. The resulting purified xerogel material present an appreciable thermal stability and resistance to leaching by solvents.

Pré-concentração de nitrosaminas a partir de amostras aquosas por extração em fase sólida e cromatografia capilar eletrocinética micelar

This paper describes the development of a methodology for solid phase extraction (SPE) and pre-concentration of nitrosamines from aqueous samples using granular activated charcoal as stationary phase. micelar electrokinetic capillary Chromatography (MEKC) was used for the separation and identification of the nitrosamines in the extracts. Using a sample with 50 µg l-1 of each nitrosamines standards (dimethylnitrosamine, DMN; diethylnitrosamine, DEN; N-nitrosopyrrolidine, NPYR; N-nitrosopiperidine, NPIP; N-nitrosomorpholine, NMOR), the methodology showed a range of recuperation from 29 to 107% with a linear zone between 10 and 500 µg l-1. The developed methodology can be applicable to the determination of these analytes in different aqueous samples.

Quantificação do linalol no óleo essencial da Aniba duckei Korstermans utilizando uma nova coluna capilar POLYH4-MD em Cromatografia Gasosa

In the present work a polyurethane polymer derived from castor oil was used as stationary phase for capillary gas chromatography. The polymer was obtained by reaction of hydroxylated compound and isocynate (NCO), forming urethane. Columns of 7 m x 0,25 mm were then coated with this stationary phase (film thickness of 0,25 µm) using static coating method. The Grob test was also performed. Samples of essential oil of the Aniba duckei Korstermans was then analysed in POLYH4-MD capillary column in order to evaluate its chromatographic perfomance. The linalool was found to be the major component and has been used as compound of departure for many important syntheses. Results show that the experimental columns give higher resolution and can be employed for analysis of essentials oils.

Quantitative analysis of phenol and alkylphenols in Brazilian coal tar

The main purpose of this work is the identification and quantification of phenolic compounds in coal tar samples from a ceramics factory in Cocal (SC), Brazil. The samples were subjected to preparative scale liquid chromatography, using Amberlyst A-27TM ion-exchange resin as stationary phase. The fractions obtained were classified as "acids" and "BN" (bases and neutrals). The identification and quantification of phenols, in the acid fraction, was made by gas chromatography coupled to mass spectrometry (GC/MS). Nearly twenty-five phenols were identified in the samples and nine of them were also quantified. The results showed that coal tar has large quantities of phenolic compounds of industrial interest.

Novas fases estacionárias à base de sílica para cromatografia líquida de alta eficiência

The present work reviews recent advances in the preparation of new reversed phase packing materials such as sterically protected, bidentate, hybrid organic-inorganic and monolithic phases and phases containing embedded polar groups. The bonding chemistry involved in the preparation of these phases as well as their advantages over conventional C8 and C18 reversed phases are discussed. Understanding the reasons behind the development of these newer column packings helps analysts select the best stationary phase for a given application.

Análise de fármacos em material biológico: acoplamento microextração em fase sólida "no tubo" e cromatografia líquida de alta eficiência

A new solid phase microextraction (SPME) system, known as in-tube SPME, was recently developed using an open tubular fused-silica capilary column, instead of an SPME fiber, as the SPME device. On-line in-tube SPME is usually used in combination with high performance liquid chromatography. Drugs in biological samples are directly extracted and concentrated in the stationary phase of capillary columns by repeated draw/eject cycles of sample solution, and then directly transferred to the liquid chromatographic column. In-tube SPME is suitable for automation. Automated sample handling procedures not only shorten the total analysis time, but also usually provide better accuracy and precision relative to manual techniques. In-tube SPME has been demonstrated to be a very effective and highly sensitive technique to determine drugs in biological samples for various purposes such as therapeutic drug monitoring, clinical toxicology, bioavailability and pharmacokinetics.

Identification of acetates in elasmopalpulus lignosellus pheromone glands using a newly created mass spectral database and kóvats retention indices

Based on a specially created mass spectral database utilizing 23 tetradecenyl and 22 hexadecenyl acetate standards along with Kóvats retention indices obtained on a very polar stationary phase [poly (biscyanopropyl siloxane)] (SP 2340), (Z)-9-hexadecenyl acetate, (Z)-11-hexadecenyl acetate and (E)-8-hexadecenyl acetate were identified in active pheromone extracts of Elasmopalpus lignosellus. This identification was more efficient than our previous study using gas chromatography/mass spectrometry with a dimethyl disulfide derivative where we could only identify the first two acetates. The acetate composition of the pheromone gland differed from region to region in Brazil and from that from the Tifton (GA, USA) population, suggesting polymorphism or a different sub-species.

Validação de método por cromatografia líquida de alta eficiência para determinação da lamivudina e zidovudina em comprimidos

An HPLC method was validated to assay lamivudine and zidovudine combined in tablets. The chromatographic separation was carried out using methanol and acetate buffer pH 6.5 (50:50 v/v) and a RP-18 column, as mobile and stationary phase, respectively. The UV detection was at 270 nm. The method was linear in the range of 24 - 36 µg/mL (lamivudine) and 48 - 72 µg/mL (zidovudine). The recovery (accuracy) ranged from 101.35% to 103.04% and the precision (repeatability and intermediate precision) was less than 2%. The method can be also applied to the quantification of these drugs in the dissolution test of tablets containing both drugs.

Um espalhador de baixo custo de fase estacionária em placas para cromatografia em camada delgada

Chromatography is a means of separating mixtures into their several components. TLC, mainly a liquid/solid process, is one of the separation techniques most often used. It is indispensable in laboratories dealing with natural products, organic and analytical chemistry. Commercial chromatography plates are offered at relatively high cost. In this work the construction of a hand-operated plate coater of stationary phases of low cost and good reproducibility is described to be used in teaching laboratories and research.

Construção de câmara de luz ultravioleta para fotopolimerização de fases estacionárias monolíticas

The assembly of a photochemical reactor with six fluorescent lamps, used for photopolymerizations is described. This chamber presents a mobile support, allowing the placement of samples at different heights and a safety lock that interrupts the radiation, if it is opened during operation. The mirrored internal walls avoid the dispersion and non-uniform distribution of light. There is no high heating because the own character of the used lamps. All parts could be purchased in commerce with less than U$ 150,00. This reactor was successfully used for monolithic stationary phase photopolymerization.

Desenvolvimento de métodos analíticos para determinação de agrotóxicos em sedimentos por cromatografia gasosa monodimensional e bidimensional abrangente com micro detector de captura de elétrons

The development of analytical methods for determination of eight pesticides of different chemical classes (trichlorfon, propanil, fipronil, propiconazole, trifloxystrobin, permethrin, difenoconazole and azoxystrobin) in sediments with gas chromatography-micro-electron capture detector (GC/µECD) and comprehensive two-dimensional gas chromatography with micro-electron capture detector (GCxGC/µECD) is described. These methods were applied to real sediment samples, and the best results were obtained using a 5% diphenyl-methylpolysiloxane column for 1D-GC. For GCxGC the same column was employed in the first dimension and a 50%-phenyl-methylpolysiloxane stationary phase was placed in the second dimension. Due to the superior peak capacity and selectivity of GCxGC, interfering matrix peaks were separated from analytes, showing a better performance of GCxGC.