Adsorção de CO2 em peneiras moleculares micro e mesoporosas

Microporous molecular sieves of type Y, Beta, ZSM-5, ZSM-12 and ZSM-35, and mesoporous molecular sieves of type MCM-41 and MCM-48, and these sieves modified with triethanolamine and ethylenediamine were obtained and characterized by XRD, FTIR, TGA and nitrogen adsorption. The adsorption tests were performed by the gravimetric method under a stream of CO2 at ambient temperature and pressure. The adsorbents studied showed maximum adsorption capacity of carbon dioxide in the range of 13.1 to 85.5 mg of CO2 per gram of adsorbent.

Influência da glutamina na mucosa do instestino de ratos submetidos à enterectomia extensa

OBJETIVO: Avaliar a influência de uma dieta suplementada com glutamina sobre as alterações adaptativas no intestino delgado de ratos com enterectomia extensa. MÉTODO: Vinte ratos Wistar, divididos aleatoriamente em dois grupos de dez animais, foram enterectomizados e alimentados com dois tipos diferentes de dieta nos 14 dias de pós-operatório: grupo controle (GC)-dieta padrão; grupo glutamina (GG)-dietapadrão acrescida de 3,05% de glutamina. Avaliou-se evolução ponderal, peso da mucosa intestinal (PM), profundidade das criptas (PC), altura das vilosidades (AV), espessura da parede (EP) e o conteúdo de ácido desoxirribonucléico (DNA) na mucosa intestinal, no início e no final do experimento. RESULTADOS: Com exceção da PC ileal do Grupo GG, todas as variáveis estudadas tiveram um aumento significativo em seus valores finais tanto no jejuno quanto no íleo (p<0,05).Entre os grupos, a comparação do PM, AV, DNA da mucosa, no jejuno e no íleo, tanto inicialmente quanto no final do estudo, bem como da EP inicial no jejuno e íleo eda PC no jejuno final e no íleo inicial e final não mostraram diferenças significativas (p>0,05). No jejuno inicial, a PC no grupo GC foi maior (p=0,005). A EP do jejuno e íleo final foi maior no grupo GC. CONCLUSÃO: A suplementação dietética com a glutamina não melhorou as alterações adaptativas que ocorrem no remanescente intestinal.

Specific fluorogenic substrates for neprilysin (neutral endopeptidase, EC 3.4.24.11) which are highly resistant to serine- and metalloproteases

Two intramolecularly quenched fluorogenic peptides containing o-aminobenzoyl (Abz) and ethylenediamine 2,4-dinitrophenyl (EDDnp) groups at amino- and carboxyl-terminal amino acid residues, Abz-DArg-Arg-Leu-EDDnp (Abz-DRRL-EDDnp) and Abz-DArg-Arg-Phe-EDDnp (Abz-DRRF-EDDnp), were selectively hydrolyzed by neutral endopeptidase (NEP, enkephalinase, neprilysin, EC 3.4.24.11) at the Arg-Leu and Arg-Phe bonds, respectively. The kinetic parameters for the NEP-catalyzed hydrolysis of Abz-DRRL-EDDnp and Abz-DRRF-EDDnp were Km = 2.8 µM, kcat = 5.3 min-1, kcat/Km = 2 min-1 µM-1 and Km = 5.0 µM, kcat = 7.0 min-1, kcat/Km = 1.4 min-1 µM-1, respectively. The high specificity of these substrates was demonstrated by their resistance to hydrolysis by metalloproteases [thermolysin (EC 3.4.24.2), angiotensin-converting enzyme (ACE; EC 3.4.24.15)], serineproteases [trypsin (EC 3.4.21.4), a-chymotrypsin (EC 3.4.21.1)] and proteases present in tissue homogenates from kidney, lung, brain and testis. The blocked amino- and carboxyl-terminal amino acids protected these substrates against the action of aminopeptidases, carboxypeptidases and ACE. Furthermore, DR amino acids ensured total protection of Abz-DRRL-EDDnp and Abz-DRRF-EDDnp against the action of thermolysin and trypsin. Leu-EDDnp and Phe-EDDnp were resistant to hydrolysis by a-chymotrypsin. The high specifity of these substrates suggests their use for specific NEP assays in crude enzyme preparations