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The Metropolitan Autonomous University is a public university system in Mexico City, Mexico. Wikipedia.

Ireta J.,Metropolitan Autonomous University
Journal of Chemical Theory and Computation

Under certain circumstances β-sheets prefer to be twisted instead of flat. To get insight into the reasons of such preference, bare and microsolvated parallel and antiparallel two-strand polyalanine β-sheets are investigated using density functional theory. Full geometry optimizations show that microsolvation increases interstrand twisting and promotes a flat to twist transition. It is found that the latter behavior is connected to compressive strain resulting from microsolvation. Residues in flat β-sheets adjust the sense of its local intrastrand twist, which leads to the appearance of interstrand twist, to release strain and to favor water-water hydrogen bonding. The predicted microsolvation effect is corroborated analyzing the geometry of residues forming β-sheet motifs in protein crystals. © 2011 American Chemical Society. Source

Objective. To evaluate the performance of the 2012 Systemic Lupus International Collaborating Clinics (SLICC) criteria in classifying systemic lupus erythematosus (SLE) in an uncontrolled real-life scenario. Methods. Chart review study was performed in which each criterion from the 1997 American College of Rheumatology (ACR) and the 2012 SLICC criteria to classify SLE was applied to patients from an outpatient rheumatology clinic. The clinical diagnosis was used as the gold standard. Results. The sensitivity and specificity of the 2012 SLICC criteria were 92% and 99%, respectively, compared with the 1997 ACR criteria, which were 97% and 99%, respectively. The 2012 SLICC criteria were similar to the 1997 ACR criteria in terms of positive (98.9% versus 99%) and negative (92.5% versus 97.1%) predictive values as well as positive (92 versus 97) and negative (0.08 versus 0.03) likelihood ratios. A concordance of 0.96 (95% confidence interval [95% CI] 0.92-1.00) was observed between clinical diagnosis and the 1997 ACR criteria, while the concordance was 0.91 (95% CI 0.85-0.97) for the 2012 SLICC criteria. Seven SLE patients classified by the 1997 ACR criteria did not meet the 2012 SLICC criteria because of either the new definition for lymphopenia (2 patients) or the presence of isolated cutaneous involvement (5 patients), while 2 SLE patients who were classified by the 2012 SLICC criteria did not meet the 1997 ACR criteria because of either the presence of erosive arthritis or biopsy-proven nephritis with circulating antinuclear antibodies. Conclusion. Overall, the 1997 ACR and the 2012 SLICC criteria are similar to classify SLE in an uncontrolled real-life scenario, although several new items contained in the 2012 SLICC criteria could represent a step forward for research purposes in selected clinical settings. © 2015, American College of Rheumatology. Source

Barrios-Gonzalez J.,Metropolitan Autonomous University
Process Biochemistry

Solid-state fermentation is an alternative culture method that has gained researchers attention over the past 20 years. There are several advantages in employing many SSF processes over the conventional submerged fermentation (SmF) ones, like higher yields of secondary metabolites or enzymes. Moreover, certain enzymes and secondary metabolites can only be produced in SSF. Many of these advantages are related to the special physiology shown by fungi in SSF. This review refers to this physiology (i.e. a behavior that deviates from the one displayed by the fungus in liquid medium), sometimes referred to as "physiology of solid medium", and its molecular basis. The reason for this different physiology in SSF is not fully understood, but recent advances are beginning to draw an interesting and wide panorama. Higher secondary metabolites production has been related to higher transcription of the biosynthetic genes; while studies on enzymes production in SSF have identified SSF-specific genes and provided deeper insight into their genetic expression and regulation. Moreover, some solid culture environmental stimuli (signals) have been identified. Many of these basic findings are also starting to be applied to new genetic improvement methods, novel culture systems, and other technological advances. © 2011 Elsevier Ltd. All rights reserved. Source

Galano A.,Metropolitan Autonomous University
Physical Chemistry Chemical Physics

The reactions of melatonin (MLT) with hydroxyl and several peroxyl radicals have been studied using the Density Functional Theory, specifically the M05-2X functional. Five mechanisms of reaction have been considered: radical adduct formation (RAF), Hydrogen atom transfer (HAT), single electron transfer (SET), sequential electron proton transfer (SEPT) and proton coupled electron transfer (PCET). It has been found that MLT reacts with OH radicals in a diffusion-limited way, regardless of the polarity of the environment, which indicates that MLT is an excellent OH radical scavenger. The calculated values of the overall rate coefficient of MLT + OH reaction in benzene and water solutions are 2.23 × 1010 and 1.85 × 1010 M-1 s-1, respectively. MLT is also predicted to be a very good OOCCl3 scavenger but rather ineffective for scavenging less reactive peroxyl radicals, such as alkenyl peroxyl radicals and OOH. Therefore it is concluded that the protective effect of MLT against lipid peroxidation does not take place by directly trapping peroxyl radicals, but rather by scavenging more reactive species, such as OH, which can initiate the degradation process. Branching ratios for the different channels of reaction are reported for the first time. In aqueous solutions SEPT was found to be the main mechanism for the MLT + OH reaction, accounting for about 44.1% of the overall reactivity of MLT towards this radical. The good agreement between the calculated and the available experimental data, on the studied processes, supports the reliability of the results presented in this work. © the Owner Societies 2011. Source

Galano A.,Metropolitan Autonomous University

The potential role of carbon nanotubes (CNTs) as free-radical scavengers is still an emerging area of research. So far some promising results have been reported strongly suggesting that CNTs can be very efficient for that task. The implications of such a valuable property for applications aimed at biomedical and environmental uses are encouraging. There are still abundant open questions related to the possible use of CNTs for scavenging free radicals. Thus much more work needs to be devoted to this fascinating topic. In this mini review the progress made so far is reviewed and some future perspectives are provided. © 2010 The Royal Society of Chemistry. Source

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