NMR Line Shapes and Multi-State Binding Equilibria

Biological function of proteins relies on conformational transitions and binding of specific ligands. Protein-ligand interactions are thermodynamically and kinetically coupled to conformational changes in protein structures as conceptualized by the models of pre-existing equilibria and induced fit. NMR spectroscopy is particularly sensitive to complex ligand-binding modes—NMR line-shape analysis can provide for thermodynamic and kinetic constants of ligand-binding equilibria with the site-specific resolution. However, broad use of line shape analysis is hampered by complexity of NMR line shapes in multi-state systems. To facilitate interpretation of such spectral patterns, I computationally explored systems where isomerization or dimerization of a protein (receptor) molecule is coupled to binding of a ligand. Through an extensive analysis of multiple exchange regimes for a family of three-state models, I identified signature features to guide an NMR experimentalist in recognizing specific interaction mechanisms. Results also show that distinct multistate models may produce very similar spectral patterns. I also discussed aggregation of a receptor as a possible source of spurious three-state line shapes and provided specific suggestions for complementary experiments that can ensure reliable mechanistic insight

The Political Economy of Corporate Governance Change in Bulgaria: Washington Consensus, Primitive Accumulation of Capital, and Catching-Up in the 1990

This study examines three key determinants of corporate governance change in Bulgaria: the Washington Consensus policy, primitive accumulation of capital forces, and 'catching-up' factors. The study reveals that in the early transition (1989-96) primitive capital accumulation prevailed over the Washington Consensus impact on corporate governance transformation while since 1997 Washington Consensus has been in the process of becoming the decisive factor for institutional change. The emerging corporate governance system has been neither Anglo-American (market based) nor bank-based, but rather a 'crony' relationship-based one. The striking features of this system are as follows: (i) a dual enterprise sector, (ii) ownership heterogeneity; (iii) fragile capital markets; (iv) pervasive banks lending behavior; (v) globalization factors discretion. The challenge to policy-makers in Bulgaria is how to design institutions for 'catching-up' that would curb both managerial and globalization factors discretion.

Fluorescence2D: Software for Accelerated Acquisition and Analysis of Two-Dimensional Fluorescence Spectra

The Fluorescence2D is free software that allows analysis of two-dimensional fluorescence spectra obtained using the accelerated “triangular” acquisition schemes. The software is a combination of Python and MATLAB-based programs that perform conversion of the triangular data, display of the two-dimensional spectra, extraction of 1D slices at different wavelengths, and output in various graphic formats

Statistics of resonances in one-dimensional disordered systems

The paper is devoted to the problem of resonances in one-dimensional disordered systems. Some of the previous results are reviewed and a number of new ones is presented. These results pertain to different models (continuous as well as lattice) and various regimes of disorder and coupling strength. In particular, a close connection between resonances and the Wigner delay time is pointed out and used to obtain information on the resonance statistics.Comment: Submitted to the special issue, in memory of Y. Levinson, of the Lithuanian Journal of Physic