In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field
Silver nanoparticles (nano-Ag) are potent and broad-spectrum antimicrobial agents. In this study, spherical nano-Ag (average diameter = 9.3 nm) particles were synthesized using a borohydride reduction method and the mode of their antibacterial action against E. coli was investigated by proteomic approaches (2-DE and MS identification), conducted in parallel to analyses involving solutions of Ag(+) ions. The proteomic data revealed that a short exposure of E. coli cells to antibacterial concentrations of nano-Ag resulted in an accumulation of envelope protein precursors, indicative of the dissipation of proton motive force. Consistent with these proteomic findings, nano-Ag were shown to destabilize the outer membrane, collapse the plasma membrane potential and deplete the levels of intracellular ATP. The mode of action of nano-Ag was also found to be similar to that of Ag(+) ions (e.g., Dibrov, P. et al, Antimicrob. Agents Chemother. 2002, 46, 2668-2670); however, the effective concentrations of nano-Ag and Ag(+) ions were at nanomolar and micromolar levels, respectively. Nano-Ag appear to be an efficient physicochemical system conferring antimicrobial silver activities.
Gold complexes have recently gained increasing attention in the design of new metal-based anticancer therapeutics. Gold(III) complexes are generally reactive/unstable under physiological conditions via intracellular redox reactions, and the intracellular Au(III) to Au(I) reduction reaction has recently been "traced" by the introduction of appropriate fluorescent ligands. Similar to most Au(I) complexes, Au(III) complexes can inhibit the activities of thiol-containing enzymes, including thioredoxin reductase, via ligand exchange reactions to form Au-S(Se) bonds. Nonetheless, there are examples of physiologically stable Au(III) and Au(I) complexes, such as [Au(TPP)]Cl (H2TPP = 5,10,15,20-tetraphenylporphyrin) and [Au(dppe)2]Cl (dppe = 1,2-bis(diphenylphosphanyl)ethane), which are known to display highly potent in vitro and in vivo anticancer activities. In this review, we summarize our current understanding of anticancer gold complexes, including their mechanisms of action and the approaches adopted to improve their anticancer efficiency. Some recent examples of gold anticancer chemotherapeutics are highlighted.
Multistep surface processes involving a number of association reactions and desorption processes may be considered as hypothetical one-step desorption processes. Thus, heterogeneous catalytic reactions can be treated kinetically as consisting of two steps: adsorption and desorption. It is also illustrated that the hypothetical one-step desorption process follows the BEP relation. A volcano curve can be obtained from kinetic analysis by including both adsorption and desorption processes.
Carbides are important phases in heterogeneous catalysis. However, the understanding of carbide phases is inadequate: Fe and Co are the two commercial catalysts for Fischer-Tropsch (FT) synthesis, and experimental work showed that Fe carbide is the active phase in FT synthesis, whereas the appearance of Co carbide is considered as a possible deactivation cause. To understand very different catalytic roles of carbides, all the key elementary steps in FT synthesis, that is, CO dissociation, C 1 hydrogenation, and C 1 +C 1 coupling, are extensively investigated on both carbide surfaces using first principles calculations. In particular, the most important issues in FT synthesis, the activity and methane selectivity, on the carbide surfaces are quantitatively determined and analyzed. They are also discussed together with metallic Fe and Co surfaces. It is found that (i) Fe carbide is more active than metallic Fe and has similar methane selectivity to Fe, being consistent with the experiments; and (ii) Co carbide is less active than Co and has higher methane selectivity, providing evidence on the molecular level to support the suggestion that the formation of Co carbide is a cause of relatively high methane selectivity and deactivation on Co catalysts.
A quantitative approach is used to understand the chain growth mechanism in FT synthesis on the Ru, Fe,
Rh, and Re surfaces. The C−C coupling reactions are extensively calculated on the stepped metal surfaces.
Combining the coupling barriers and reactant stabilities, we investigate the reaction rates of all possible C1
+ C1 coupling pathways on the metal surfaces. It is found that (i) all the transition-state structures are similar
on these surfaces, while some coupling barriers are very different; (ii) the dominant chain growth pathways
on these surfaces are different: C + CH and CH + CH on Rh and Ru surfaces, C + CH3 on Fe surface, and
C + CH on Re surface. The common features of the major coupling reactions together with those on the Co
surface are also discussed.
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