Hasil untuk "Biochemistry"

W. Rehrauer, S. Kowalczykowski, D. A. Dixon et al.

Homologous recombination is a fundamental biological process. Biochemical understanding of this process is most advanced for Escherichia coli. At least 25 gene products are involved in promoting genetic exchange. At present, this includes the RecA, RecBCD (exonuclease V), RecE (exonuclease VIII), RecF, RecG, RecJ, RecN, RecOR, RecQ, RecT, RuvAB, RuvC, SbcCD, and SSB proteins, as well as DNA polymerase I, DNA gyrase, DNA topoisomerase I, DNA ligase, and DNA helicases. The activities displayed by these enzymes include homologous DNA pairing and strand exchange, helicase, branch migration, Holliday junction binding and cleavage, nuclease, ATPase, topoisomerase, DNA binding, ATP binding, polymerase, and ligase, and, collectively, they define biochemical events that are essential for efficient recombination. In addition to these needed proteins, a cis-acting recombination hot spot known as Chi (chi: 5'-GCTGGTGG-3') plays a crucial regulatory function. The biochemical steps that comprise homologous recombination can be formally divided into four parts: (i) processing of DNA molecules into suitable recombination substrates, (ii) homologous pairing of the DNA partners and the exchange of DNA strands, (iii) extension of the nascent DNA heteroduplex; and (iv) resolution of the resulting crossover structure. This review focuses on the biochemical mechanisms underlying these steps, with particular emphases on the activities of the proteins involved and on the integration of these activities into likely biochemical pathways for recombination.

R. Murray..., D. Granner, V. Rodwell

M. Linder, M. Hazegh-Azam

In this review, our basic and most recent understanding of copper biochemistry and molecular biology for mammals (including humans) is described. Information is provided on the nutritional biochemistry of copper, including food sources, intestinal absorption, transport, tissue distribution, and excretion, along with descriptions of copper binding proteins and other factors involved and their roles in these processes. The metabolism of copper and its importance for the functions of a roster of vital enzymes is detailed. Its potential toxicology is also addressed. Alterations in copper metabolism associated with genetic and nongenetic diseases are summarized, including potential connections to inflammation, cancer, atherosclerosis, and anemia, and the effects of genetic copper deficiency (Menkes syndrome) and copper overload (Wilson disease). Understanding these diseases suggests new ways of viewing the normal functions of copper and provides new insights into the details of copper transport and distribution in mammals.

K. Setchell

P. McSweeney

P. Fox, T. Uniacke-Lowe, P. McSweeney et al.

H. Bowen

R. Henderson, D. Tocher

G. Seymour, J. Taylor, G. Tucker

S. Hecht

J. Kägi, Andreas Schäffer

J. Peralta-Videa, M. L. López, M. Narayan et al.

C. Ratledge, J. Wynn

J. Haeggström, C. Funk

R. Wanders, H. Waterham

Miklós Müller, M. Mentel, J. V. van Hellemond et al.

A. Migliore, N. Polizzi, M. Therien et al.

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

Ana Paula Yumi Nishimura, Fernando Augusto Pedersen Voll, Nadia Krieger et al.

Kinetic models are important tools for guiding the design and optimization of lipase-catalyzed processes. These processes follow the Ping Pong bi bi mechanism, for which mechanistic kinetic equations can be derived. However, when there are several competing reactions, fully mechanistic models contain a large number of parameters, making it difficult to obtain reliable estimates, so simplified models are necessary. We present a two-step approach to developing semi-mechanistic models of such processes. The first step involves the estimation of the selectivities of the enzyme, using profiles for the reaction species plotted against the degree of reaction, while the second step involves empirical fitting to the same data, but plotted as a function of time. We demonstrate this two-step approach through four case studies based on the literature data for the lipase-catalyzed esterification of fatty acids with trimethylolpropane to produce biolubricants. The semi-mechanistic models were able to describe the data well. Our approach has the advantage of allowing selectivities to be estimated without confounding effects from phenomena such as enzyme denaturation and inhibition. It therefore provides a promising framework for developing models of enzyme-catalyzed processes that obey Ping Pong bi bi kinetics.

Zahra Tavakoli, Khosro Khajeh, Bijan Ranjbar

Prostate cancer is the second most common cancer globally, causing ≈396,792 deaths in 2022. Early diagnosis and advanced drug delivery are vital to prevent its progression. This research leverages the anticancer properties of selenium nanoparticles and enzalutamide, a leading prostate cancer drug, by coencapsulating them within mesoporous silica nanoparticles (MSNPs). MSNPs offer advantages for drug delivery, including high surface accessibility and a tunable porous structure. The results indicated that MSNPs synthesized via solvent extraction, yielding a specific surface area of 1017.4 m2/g, a pore volume of 0.2531 cm3/g, and an average pore size of ≈10 nm, were superior to those obtained by calcination, which yielded a smaller pore size (≈3 nm). Enzalutamide was loaded into these selenium‐embedded MSNPs, achieving a drug loading efficiency of 76.3 ± 0.5%. Separately, curcumin was encapsulated in chitosan nanoparticles with high efficiency (83.2 ± 0.7%). The combined nanosystem enables pH‐responsive, gradual drug release that mimics the tumor microenvironment. MTT assays confirmed the drug‐loaded system exerts significantly stronger, time‐ and concentration‐dependent anticancer effects than the free drug. Furthermore, curcumin plays a vital role in enhancing anticancer efficacy and inducing apoptosis. This research demonstrates that the designed dual‐nanoparticle system is a promising candidate for targeted prostate cancer therapy.

Stamatia Bellou, M. Baeshen, A. Elazzazy et al.