Growth of fat slits and dispersionless KP hierarchy

A "fat slit" is a compact domain in the upper half plane bounded by a curve with endpoints on the real axis and a segment of the real axis between them. We consider conformal maps of the upper half plane to the exterior of a fat slit parameterized by harmonic moments of the latter and show that they obey an infinite set of Lax equations for the dispersionless KP hierarchy. Deformation of a fat slit under changing a particular harmonic moment can be treated as a growth process similar to the Laplacian growth of domains in the whole plane. This construction extends the well known link between solutions to the dispersionless KP hierarchy and conformal maps of slit domains in the upper half plane and provides a new, large family of solutions.Comment: 26 pages, 6 figures, typos correcte

Soluble oligomerization provides a beneficial fitness effect on destabilizing mutations

Mutations create the genetic diversity on which selective pressures can act, yet also create structural instability in proteins. How, then, is it possible for organisms to ameliorate mutation-induced perturbations of protein stability while maintaining biological fitness and gaining a selective advantage? Here we used a new technique of site-specific chromosomal mutagenesis to introduce a selected set of mostly destabilizing mutations into folA - an essential chromosomal gene of E. coli encoding dihydrofolate reductase (DHFR) - to determine how changes in protein stability, activity and abundance affect fitness. In total, 27 E.coli strains carrying mutant DHFR were created. We found no significant correlation between protein stability and its catalytic activity nor between catalytic activity and fitness in a limited range of variation of catalytic activity observed in mutants. The stability of these mutants is strongly correlated with their intracellular abundance; suggesting that protein homeostatic machinery plays an active role in maintaining intracellular concentrations of proteins. Fitness also shows a significant correlation with intracellular abundance of soluble DHFR in cells growing at 30oC. At 42oC, on the other hand, the picture was mixed, yet remarkable: a few strains carrying mutant DHFR proteins aggregated rendering them nonviable, but, intriguingly, the majority exhibited fitness higher than wild type. We found that mutational destabilization of DHFR proteins in E. coli is counterbalanced at 42oC by their soluble oligomerization, thereby restoring structural stability and protecting against aggregation

Mechanisms of activation of interferon regulator factor 3: the role of C-terminal domain phosphorylation in IRF-3 dimerization and DNA binding

The interferon regulatory transcription factor (IRF-3) is activated by phosphorylation of Ser/Thr residues clustered in its C-terminal domain. Phosphorylation of these residues, which increases the negative charge of IRF-3, results in its dimerization and association with DNA, despite the increase in repulsive electrostatic interactions. To investigate this surprising effect, the dimerization of IRF-3 and two phosphomimetic mutants, 2D (S396D, S398D) and 5D (S396D, S398D, S402D, T404D and S405D), and their binding to single-site PRDI and double-site PRDIII–PRDI DNA sequences from the IFN-β enhancer have been studied. It was found that: (a) the mutations in the C-terminal domain do not affect the state of the DNA-binding N-terminal domain or its ability to bind target DNA; (b) in the 5D-mutant, the local increase of negative charge in the C-terminal domain induces restructuring, resulting in the formation of a stable dimer; (c) dimerization of IRF-3 is the basis of its strong binding to PRDIII–PRDI sites since binding of 5D to the single PRDI site is similar to that of inactivated IRF-3. Analysis of the binding characteristics leads to the conclusion that binding of dimeric IRF-3 to the DNA with two tandem-binding sites, which are twisted by ∼100° relative to each other, requires considerable work to untwist and/or bend the DNA

Test of cold denaturation mechanism for proteins as a function of water's structure

In a recent paper [PRL 91, 138103 (2003)] a new mechanism to explain the cold denaturation of proteins, based on the loss of local low-density water structure, has been proposed. In the present paper this mechanism is tested by means of full atom numerical simulations. In good agreement with this proposal, cold denaturation resulting in the unfolded state was found at the High Density Liquid (HDL) state of water, at which the amount of open tetragonal hydrogen bonds decreases at cooling.Comment: 5 pages, 5 figure

Simplicity of eigenvalues in Anderson-type models

We show almost sure simplicity of eigenvalues for several models of Anderson-type random Schr\"odinger operators, extending methods introduced by Simon for the discrete Anderson model. These methods work throughout the spectrum and are not restricted to the localization regime. We establish general criteria for the simplicity of eigenvalues which can be interpreted as separately excluding the absence of local and global symmetries, respectively. The criteria are applied to Anderson models with matrix-valued potential as well as with single-site potentials supported on a finite box.Comment: 20 page

Active methods of formation of competence of information security of the person in professional pedagogical education

The article presents an analysis of the current state of the use of active learning methods of students during their training to ensure information security of the individual pupilsВ статье представлен анализ современного состояния использования активных методов обучения студентов в ходе их профессиональной подготовки для обеспечения информационной безопасности личности школьнико

METHODOLOGICAL APPROACHES TO ORGANIZATION OF SAFE INFORMATION AND EDUCATIONAL ENVIRONMENT OF THE UNIVERSITY

Introduction. One of the tendencies of modern higher education is the ubiquitous use of information and communication technologies. At the same time, the functioning of the electronic information and educational environment (IEE) of the university should be based on the means of IEE and the condition of its information security. The aim of the research is conceptualization of a problem of the rational organization of the safe information and education environment of higher education institution wherein reliable protection of its infrastructure, the personal and unique information of a pupil and teacher and virtual space of their educational interaction is provided. Methodology and research methods. System-based approach is a key approach to organization of safe educational environment of the university. From the point of view of authors, personal-activity and functional approaches are expedient while designing and development of a safe IEE. Socio-historical and theoretical-methodological analysis, modeling, research and synthesis of experience of effective application of the systems approach in educational professional organizations are used.Results and scientific novelty. The concept «safe information educational environment of the university» is specified wherein the first word has to express a predominant quality of the system. Creating a safe information environment in educational professional organizations provides a convenient and safe educational environment in the process of professional training of university students. The components and directions for the organization of the safe IEE are highlighted. Practical recommendations for its design and successful functioning are given. Practical significance. The materials of the present research can be demanded by managers and administrative employees of educational organizations. Введение. Современное высшее образование уже невозможно представить без использования средств информационных и коммуникационных технологий. Вместе с тем информационно-образовательная среда (ИОС) обладает потенциальными угрозами для ее субъектов, в частности из-за наличия в ней возможностей манипуляции сознанием, воздействия на психические и физиологические структуры личности, доступности сайтов террористического и экстремистского характера и т. п. Таким образом, требуются специальные меры по защите ИОС от внешних негативных влияний. Цель статьи – осмысление проблемы рациональной организации безопасной информационно-образовательной среды вуза, в которой предусмотрена надежная защита ее инфраструктуры, персональных и уникальных данных учащегося и педагога и виртуального пространства их учебного взаимодействия. Методология и методы. Ведущим подходом к решению обсуждаемой проблемы является системный подход. При проектировании и разработке безопасной ИОС, с точки зрения авторов, целесообразны также личностно-деятельностный и функциональный подходы. Кроме того, в работе использовались методы социально-исторического и теоретико-методологического анализа, моделирование, обобщение опыта образовательных организаций профессиональной подготовки.Результаты и научная новизна. Уточнено понятие «безопасная информационно-образовательная среда вуза», в котором первое слово должно выражать доминирующее свойство системы. Создание безопасной ИОС трактуется как необходимое условие обеспечения комфортного и качественного процесса профессиональной подготовки студентов. Выделены компоненты безопасной ИОС и представлены направления организации данной среды. Сформулированы практические рекомендации для ее создания и успешного функционирования. Практическая значимость. Материалы исследования могут быть востребованы менеджерами и административными работниками образовательных организаций.

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