Are high-lysine cereal crops still a challenge?

The essential amino acids lysine and threonine are synthesized in higher plants via a pathway starting with aspartate that also leads to the formation of methionine and isoleucine. Lysine is one of most limiting amino acids in plants consumed by humans and livestock. Recent genetic, molecular, and biochemical evidence suggests that lysine synthesis and catabolism are regulated by complex mechanisms. Early kinetic studies utilizing mutants and transgenic plants that over-accumulate lysine have indicated that the major step for the regulation of lysine biosynthesis is at the enzyme dihydrodipicolinate synthase. Despite this tight regulation, recent strong evidence indicates that lysine catabolism is also subject to control, particularly in cereal seeds. The challenge of producing crops with a high-lysine concentration in the seeds appeared to be in sight a few years ago. However, apart from the quality protein maize lines currently commercially available, the release of high-lysine crops has not yet occurred. We are left with the question, is the production of high-lysine crops still a challenge?98599

Free 2-propen-1-amine Derivative And Inclusion Complexes With β-cyclodextrin: Scanning Electron Microscopy, Dissolution, Cytotoxicity And Antimycobacterial Activity

Inclusion complexes and physical mixtures of isomeric mixture of E/Z (50:50) of 3-(4′-bromo-[1,1′-biphenyl]-4-yl)-3-(4-bromophenyl)-N,N- dimethyl-2-propen-1-amine (BBAP) and β-cyclodextrin (β-CD) in the molar proportion of 1:1 and 1:2 were analyzed by scanning electron microscopy. The dissolution behavior of BBAP and of the inclusion complexes were also evaluated for six hours. By scanning electron microscopy (SEM), it was possible to observe an inclusion complex formed between BBAP and β-CD by co-evaporation, either in the molar proportion of 1:1 or 1:2. In the physical mixtures, no complex was observed as previously detected by physicochemical analysis. The dissolution studies showed that the inclusion complexes BBAP/β-CD 1:1 and 1:2 released respectively 49.07 ± 1.48 and 40.26 ± 3.90% of BBAP during six hours. Free BBAP was less soluble than the inclusion complex and reached 9.00 ± 0.75% of dissolution. Biological assays, such as cytotoxicity to J774 macrophages and to a permanent lung fibroblast cell line (V79), indicated that the BBAP does not exhibit any additional toxic effect with the β-CD complexes. However, the complexes were less cytotoxic to V79 cells than the free form. The BBAP/β-CD inclusion complexes were more effective (MIC) than the free compound on several mycobacteria strains. Similar behavior was observed for BBAP/β-CD complexes and rifampicin, a front-line antitubercular drug, on M. tuberculosis H37Rv growing inside J774 macrophages.155682689Bibby, D.C., Davies, N.M., Tucker, I.G., (2000) Int. J. Pharm., 197, p. 1De Souza, A.O., Sato, D.N., Aily, D.C.G., Durán, N., (1998) J. Antimicrob. Chemother., 42, p. 407Pereira, D.G., De Castro, S.L., Durán, N., (1998) Acta Tropica, 69, p. 205De Souza, A.O., Santos Júnior, R.R., Ferreira-Júlio, J.F., Rodrigues, J.A., Melo, P.S., Haun, M., Sato, D.N., Durán, N., (2001) Eur. J. Med. Chem., 36, p. 843De Souza, A.O., Hemerly, F.P., Busollo, A.C., Melo, P.S., Machado, G.M.C., Miranda, C.C., Santa-Rita, R.M., Durán, N., (2002) J. Antimicrob. Chemother., 50, p. 629De Conti, R., Gimenez, S.M.N., Haun, M., Pilli, R.A., De Castro, S.L., Durán, N., (1996) Eur. J. Med. Chem., 31, p. 915De Souza, A.O., Santos Jr., R.R., Sato, D.N., Lima, H.O.S., Andrade-Santana, M.H., Alderete, J.B., Faljoni-Alario, A., Durán, N., (2000) Abstracts of the 29 a Reunião Anual Da Sociedade Brasileira de Bioquímica, , Caxambu, BrazilHiguchi, T., Connors, K.A., (1965) Adv. Anal. Chem. Instrum., 4, p. 117Collins, L.A., Franzblau, S.G., (1997) Antimicrob. Agents Chemother., 41, p. 1004Oh, Y.K., Nix, D.E., Straubinger, R.M., (1995) Antimicrob Agents Chemother., 39, p. 2104Cingi, M.R., De Angelis, I., Fortunati, E., Reggiani, D., Bianchi, V., Tiozzo, R., Zucco, F., (1991) Toxicol. In Vitro, 5, p. 119Denizot, F., Lang, R., (1986) J. Immun. Methods, 89, p. 271Borenfreund, E., Puerner, J.A., (1984) J. Tiss. Cult. Meth., 9, p. 7Melo, P.S., Maria, S.S., Vidal, B.C., Haun, M., Durán, N., (2000) In Vitro Cell Rev. Biol. Animal, 36, p. 539Melo, P.S., Durán, N., Haun, M., (2001) Toxicology, 159, p. 135Shrivastava, R., John, G.W., Rispat, G., Chevalier, A., Massingham, R., (1991) ATLA - Alt. Lab. Anim., 19, p. 39

Carbono orgânico dissolvido e biodisponibilidade de N e P como indicadores de qualidade do solo

Nas últimas décadas, qualidade do solo tem se tornado um tópico importante na ciência do solo. Embora esforços consideráveis tenham sido dedicados com o intuito de definir "qualidade do solo", ainda não há um conceito amplamente aceito pela comunidade cientifica. A seleção de índices qualitativos para definir qualidade do solo é uma tarefa extremamente difícil, e diversas propriedades químicas, físicas e biológicas tem sido sugeridas como potenciais indicadores. A matéria orgânica do solo está associada com processos químicos, físicos e biológicos no solo, e, portanto, é considerada um dos melhores indicadores de qualidade do solo. O manejo do solo pode influenciar significativamente a dinâmica do carbono orgânico e o ciclo de N, P, e S. Entretanto, mudanças na concentração total da matéria organica em resposta ao manejo pode ser dificil de ser detectada devido à variabilidade natural do solo. Quando comparada com a matéria orgânica total do solo, a fração mais prontamente disponível, como o carbono orgânico dissolvido (COD), é mais sensível às mudanças no manejo do solo a curto e médio prazo e, portanto, pode ser utilizada como indicador fundamental de qualidade do solo ou das alterações das condições naturais. Embora a fração dissolvida represente apenas uma pequena porção da matéria orgânica total do solo, o COD é móvel no solo e constitui uma importante fonte de C para os microorganismos, podendo facilmente refletir os efeitos de diferentes sistemas de manejo. Inúmeros métodos são utilizados para caracterizar o COD, mas os processos que influenciam sua mineralização e a disponibilidade dos elementos associado com a matéria orgânica (N, P, e S) ainda não são completamente entendidos. Pesquisas futuras devem buscar entender os processos que governam a dinâmica de nutrientes e do COD e como os mesmos afetam a qualidade do solo.Soil quality has become an important issue in soil science. Considerable attempts have been made to define soil quality, but a general concept has not yet been accepted by the scientific community. The selection of quantitative indices for soil quality is extremely difficult, and a considerable number of chemical, physical, and biochemical properties have been suggested as potential indicators of soil quality. Because soil organic matter (SOM) can be associated with different soil chemical, physical and biological processes, it has been widely considered as one of the best soil quality indicator. Land use can significantly influence dynamics of organic carbon and N, P, and S cycle. However, changes in total soil organic carbon (SOC) contents in response to land use may be difficult to detect because of the natural soil variability. In the short to medium term, biological properties and readily decomposable fractions of SOC, such as dissolved organic carbon (DOC), are much more sensitive to soil management than is SOM as a whole, and can be used as a key indicator of soil natural functions. Despite the fact that labile C accounts for a small portion of the total organic matter in the soils, DOC is the most mobile and important C-source for microorganisms, and can easily reflect the effects of land use on soil quality. Although several methods are used to characterize DOC, the factors influencing mineralization and bioavailability of elements associated with organic matter (N, P, and S) remains unclear. Future research should focus on the processes that govern DOC and nutrient dynamics and how they affect soil quality