Entropy driven key-lock assembly

The effective interaction between a sphere with an open cavity (lock) and a spherical macroparticle (key), both immersed in a hard sphere fluid, is studied by means of Monte Carlo simulations. As a result, a 2d map of the key-lock effective interaction potential is constructed, which leads to the proposal of a self-assembling mechanism: there exists trajectories through which the key-lock pair could assemble avoiding trespassing potential barriers. Hence, solely the entropic contribution can induce their self-assembling even in the absence of attractive forces. This study points out the solvent contribution within the underlying mechanisms of substrate-protein assembly/disassembly processes, which are important steps of the enzyme catalysis and protein mediated transport

The Professional Development School : a Descriptive Case Study of its History and Development

Problem. The development o f school/university partnerships is not a simple process. It requires collaboration between two groups o f professionals who come from different cultures, have developed different forms o f expertise, and operate under different organizational conditions and reward structures (Goodlad, 1990; Stoddart, Winitzky & O ’Keefe, 1992). Throughout much o f the last century, collaboration between schools and universities have often been unsuccessful. In order for Professional Development Schools to be successful in educational reform, it is necessary to focus on defining and delineating the essential characteristics of Professional Development Schools and the process o f their establishment. Purpose. The purpose o f this study was to (1) define Professional Development School and delineate its component parts; (2) describe its history, and chronicle the establishment of a Professional Development School; and (3) explore the implications o f Professional Development Schools for local school change, school/university relationships, and national standards. Methodology. This study used a descriptive, qualitative case study method based on interviews, observations, documents, and artifacts, to describe the Professional Development School (PDS). Data were collected from five primary informants, including two deans o f schools o f education, two national PDS specialists, and one local elementary school with its partnering. These data were used to define and describe the process o f establishing a Professional Development School. Findings and Conclusions. The study highlighted some o f the challenges involved in developing and establishing a Professional Development School. It documented the need to (1) provide a clear operational definition o f a PDS; (2) provide a substantial opportunity for developing relationships; and (3) use research to identify developmental stages o f the PDS

Living on the edge of chaos: minimally nonlinear models of genetic regulatory dynamics

Linearized catalytic reaction equations modeling e.g. the dynamics of genetic regulatory networks under the constraint that expression levels, i.e. molecular concentrations of nucleic material are positive, exhibit nontrivial dynamical properties, which depend on the average connectivity of the reaction network. In these systems the inflation of the edge of chaos and multi-stability have been demonstrated to exist. The positivity constraint introduces a nonlinearity which makes chaotic dynamics possible. Despite the simplicity of such minimally nonlinear systems, their basic properties allow to understand fundamental dynamical properties of complex biological reaction networks. We analyze the Lyapunov spectrum, determine the probability to find stationary oscillating solutions, demonstrate the effect of the nonlinearity on the effective in- and out-degree of the active interaction network and study how the frequency distributions of oscillatory modes of such system depend on the average connectivity.Comment: 11 pages, 5 figure

Mass spectrometry captures off-target drug binding and provides mechanistic insights into the human metalloprotease ZMPSTE24.

Off-target binding of hydrophobic drugs can lead to unwanted side effects, either through specific or non-specific binding to unintended membrane protein targets. However, distinguishing the binding of drugs to membrane proteins from that of detergents, lipids and cofactors is challenging. Here, we use high-resolution mass spectrometry to study the effects of HIV protease inhibitors on the human zinc metalloprotease ZMPSTE24. This intramembrane protease plays a major role in converting prelamin A to mature lamin A. We monitored the proteolysis of farnesylated prelamin A peptide by ZMPSTE24 and unexpectedly found retention of the C-terminal peptide product with the enzyme. We also resolved binding of zinc, lipids and HIV protease inhibitors and showed that drug binding blocked prelamin A peptide cleavage and conferred stability to ZMPSTE24. Our results not only have relevance for the progeria-like side effects of certain HIV protease inhibitor drugs, but also highlight new approaches for documenting off-target drug binding

Classification of All Poisson-Lie Structures on an Infinite-Dimensional Jet Group

A local classification of all Poisson-Lie structures on an infinite-dimensional group $G_{\infty}$ of formal power series is given. All Lie bialgebra structures on the Lie algebra {\Cal G}_{\infty} of $G_{\infty}$ are also classified.Comment: 11 pages, AmSTeX fil