Comment on "Chain Length Scaling of Protein Folding Time", PRL 77, 5433 (1996)

In a recent Letter, Gutin, Abkevich, and Shakhnovich (GAS) reported on a series of dynamical Monte Carlo simulations on lattice models of proteins. Based on these highly simplified models, they found that four different potential energies lead to four different folding time scales tau_f, where tau_f scales with chain length as N^lambda (see, also, Refs. [2-4]), with lambda varying from 2.7 to 6.0. However, due to the lack of microscopic models of protein folding dynamics, the interpretation and origin of the data have remained somewhat speculative. It is the purpose of this Comment to point out that the application of a simple "mesoscopic" model (cond-mat/9512019, PRL 77, 2324, 1996) of protein folding provides a full account of the data presented in their paper. Moreover, we find a major qualitative disagreement with the argumentative interpretation of GAS. Including, the origin of the dynamics, and size of the critical folding nucleus.Comment: 1 page Revtex, 1 fig. upon request. Submitted to PR

Relevance of Social, Economic, and Environmental Impacts on Residents’ Satisfaction with the Public Administration of Tourism

Those in charge of tourism destinations face the need to create tourism development models compatible with the essence of the localities that they manage. These models have to be sustainable, both environmentally and socially, and also must become drivers of the local economy. However, tourists also generate negative impacts in the locality which, when they are perceived by the residents, can give rise to a rejection of visitors. Hence, improving the tourism management is necessary. This is why to know the residents’ perceptions about the impacts of tourism is essential. Moreover, measuring the impact effects on their satisfaction with the public administration of the destination can be of great usefulness. This study falls into this research line, as it proposes a model to measure these impacts and their effect on satisfaction. To do so, an empirical study is performed among residents in the city of Seville (southern Spain, one of the most visited destinations in the world), based on subjective economic, social, and environmental indicators. The results show that the citizens value three types of impacts, the social impact coming after the economic impact as to its influence on their satisfaction with the administration. Based on this, we postulate that the efforts made to attract events to the city, or to improve connections to access a broader market, must be approached as public procurements in which selection criteria that are compatible with the destination’s positioning and strategy prevail. Social and environmental criteria should be considered among these criteria

FastContact: a free energy scoring tool for protein–protein complex structures

‘FastContact’ is a server that estimates the direct electrostatic and desolvation interaction free energy between two proteins in units of kcal/mol. Users submit two proteins in PDB format, and the output is emailed back to the user in three files: one output file, and the two processed proteins. Besides the electrostatic and desolvation free energy, the server reports residue contact free energies that rapidly highlight the hotspots of the interaction and evaluates the van der Waals interaction using CHARMm. Response time is ∼1 min. The server has been successfully tested and validated, scoring refined complex structures and blind sets of docking decoys, as well as proven useful predicting protein interactions. ‘FastContact’ offers unique capabilities from biophysical insights to scoring and identifying important contacts

Exact Random Walk Distributions using Noncommutative Geometry

Using the results obtained by the non commutative geometry techniques applied to the Harper equation, we derive the areas distribution of random walks of length $N$ on a two-dimensional square lattice for large $N$, taking into account finite size contributions.Comment: Latex, 3 pages, 1 figure, to be published in J. Phys. A : Math. Ge

LA INSTRUCCIÓN PROGRAMADA REMOTA Y EL TUTORIAL COMO ESTRATEGIAS EN EL PROCESO DE APRENDIZAJE PARA EL DESARROLLO DE COMPETENCIAS MATEMÁTICAS.

The objective of the research is to determine the importance in the use of the remote programmed instruction and the tutorial as strategies in the learning process for the development of mathematical competences in students of the middle school of Educational Institutions of the District of Barranquilla, Colombia. Given the current situation of remote education caused by the pandemic Sars Cov 2 virus, known as Corona Virus, Covid 19, has had an impact on the fabric of human reality on a planetary level, especially because of the health conditions of communities at the local, regional, national and global levels, educational institutions as social organizations have thus migrated to a form of virtual study. In this sense, the role that the school plays in this current context, its teachers and parents have been decisive to face this formation from the home, where the technologies are the tools that allow to establish the direct connection with the students. Methodologically, the research was descriptive – Field, with a non-experimental, transactional design, with descriptive and inferential analysis. The population consisted of 140 eleventh-grade students. It was found that the eleventh grade students stood out in the high category, when it comes to using technological tools using the Remote Programmed Instruction (IPR) and the tutorial on solving mathematical problems. It is concluded that the use of technologies under the virtual remote modality promotes favorable results in the training of students. It is recommended to establish a curriculum and content in the area of mathematics adapted to learning strategies through remote programmed teaching.El objetivo de la investigación es determinar la importancia en el uso de la instrucción programada remota y del tutorial como estrategias en el proceso de aprendizaje para el desarrollo de competencias matemáticas en estudiantes de la media de Instituciones Educativas del Distrito de Barranquilla, Colombia. Dada la situación actual de una educación a distancia remota provocada por la pandemia del virus Sars Cov 2, conocido como Corona Virus, Covid 19, ha tenido un impacto en el tejido de la realidad humana a nivel planetario, sobre todo por las condiciones sanitarias que presentan las comunidades a nivel local, regional, nacional y mundial, en consecuencia, las instituciones educativas como organizaciones sociales han emigrado en estos tiempos a una modalidad de estudio virtual. En ese sentido, el papel que juega la escuela en este contexto actual, sus docentes y padres de familia ha sido determinante para enfrentar esta formación desde el hogar, donde las tecnologías son las herramientas que permiten establecer la conexión directa con los estudiantes. Metodológicamente, la investigación fue descriptiva – De campo, con un diseño no experimental, transaccional, con un análisis descriptivo e inferencial. La población estuvo constituida por 140 estudiantes de undécimo grado. Se encontró que los estudiantes de undécimo grado se destacaron en la categoría alta, cuando se trata de utilizar herramientas tecnológicas valiéndose de la Instrucción Programada Remota (IPR) y el tutorial en la resolución de problemas matemáticos. Se concluye que el empleo de las tecnologías bajo la modalidad remota virtual promueve resultados favorables en la formación del estudiantado. Se recomienda establecer un currículo y contenidos en el área de matemáticas ajustados a las estrategias de aprendizaje mediante la enseñanza programada remota

Entropic Barriers, Frustration and Order: Basic Ingredients in Protein Folding

We solve a model that takes into account entropic barriers, frustration, and the organization of a protein-like molecule. For a chain of size $M$, there is an effective folding transition to an ordered structure. Without frustration, this state is reached in a time that scales as $M^{\lambda}$, with $\lambda\simeq 3$. This scaling is limited by the amount of frustration which leads to the dynamical selectivity of proteins: foldable proteins are limited to $\sim 300$ monomers; and they are stable in {\it one} range of temperatures, independent of size and structure. These predictions explain generic properties of {\it in vivo} proteins.Comment: 4 pages, 4 Figures appended as postscript fil

Tandem phosphorylation within an intrinsically disordered region regulates ACTN4 function

Phosphorylated residues occur preferentially in the intrinsically disordered regions of eukaryotic proteins. In the disordered amino-terminal region of human a-actinin-4 (ACTN4), Tyr[superscript 4] and Tyr[superscript 31] are phosphorylated in cells stimulated with epidermal growth factor (EGF), and a mutant with phosphorylation-mimicking mutations of both tyrosines exhibits reduced interaction with actin in vitro. Cleavage of ACTN4 by m-calpain, a protease that in motile cells is predominantly activated at the rear, removes the Tyr[superscript 4] site. We found that introducing a phosphomimetic mutation at only Tyr[superscript 31] was sufficient to inhibit the interaction with actin in vitro. However, molecular dynamics simulations predicted that Tyr[superscript 31] is mostly buried and that phosphorylation of Tyr[superscript 4] would increase the solvent exposure and thus kinase accessibility of Tyr[superscript 31]. In fibroblast cells, EGF stimulation increased tyrosine phosphorylation of a mutant form of ACTN4 with a phosphorylation-mimicking residue at Tyr[superscript 4], whereas a truncated mutant representing the product of m-calpain cleavage exhibited EGF-stimulated tyrosine phosphorylation at a background amount similar to that observed for a double phosphomimetic mutant of Tyr[superscript 4] and Tyr[superscript 31]. We also found that inhibition of the receptor tyrosine kinases of the TAM family, such as AXL, blocked EGF-stimulated tyrosine phosphorylation of ACTN4. Mathematical modeling predicted that the kinetics of phosphorylation at Tyr[superscript 31] can be dictated by the kinase affinity for Tyr[superscript 4]. This study suggests that tandem-site phosphorylation within intrinsically disordered regions provides a mechanism for a site to function as a switch to reveal a nearby function-regulating site.National Institutes of Health (U.S.) (Grant R01 GM69668

SUMOylation of nuclear actin

Actin, a major component of the cytoplasm, is also abundant in the nucleus. Nuclear actin is involved in a variety of nuclear processes including transcription, chromatin remodeling, and intranuclear transport. Nevertheless, the regulation of nuclear actin by posttranslational modifications has not been investigated. We now show that nuclear actin is modified by SUMO2 and SUMO3 and that computational modeling and site-directed mutagenesis identified K68 and K284 as critical sites for SUMOylating actin. We also present a model for the actin–SUMO complex and show that SUMOylation is required for the nuclear localization of actin

Solar-driven semi-conductor photocatalytic water treatment (TiO2, g-C3N4, and TiO2+g-C3N4) of cyanotoxins: proof-of-concept study with microcystin-LR.

Cyanobacteria and their toxins are a threat to drinking water safety as increasingly cyanobacterial blooms (mass occurrences) occur in lakes and reservoirs all over the world. Photocatalytic removal of cyanotoxins by solar light active catalysts is a promising way to purify water at relatively low cost compared to modifying existing infrastructure. We have established a facile and low-cost method to obtain TiO2 and g-C3N4 coated floating photocatalysts using recycled glass beads. g-C3N4 coated and TiO2+g-C3N4 co-coated beads were able to completely remove microcystin-LR in artificial fresh water under both natural and simulated solar light irradiation without agitation in less than 2 h. TiO2 coated beads achieved complete removal within 8 h of irradiation. TiO2+g-C3N4 beads were more effective than g-C3N4 beads as demonstrated by the increase reaction rate with reaction constants, 0.0485 min−1 compared to 0.0264 min−1 respectively, with TiO2 alone found to be considerably slower 0.0072 min−1. g-C3N4 based photocatalysts showed a similar degradation pathway to TiO2 based photocatalysts by attacking the C6–C7 double bond on the Adda side chain