A quantitative model of a cooperative two-state equilibrium in DNA: experimental tests, insights, and predictions

Quantitative parameters for a two-state cooperative transition in duplex DNAs were finally obtained during the last 5 years. After a brief discussion of observations pertaining to the existence of the two-state equilibrium per se, the lengths, torsion, and bending elastic constants of the two states involved and the cooperativity parameter of the model are simply stated. Experimental tests of model predictions for the responses of DNA to small applied stretching, twisting, and bending stresses, and changes in temperature, ionic conditions, and sequence are described. The mechanism and significance of the large cooperativity, which enables significant DNA responses to such small perturbations, are also noted. The capacity of the model to resolve a number of long-standing and sometimes interconnected puzzles in the extant literature, including the origin of the broad pre-melting transition studied by numerous workers in the 1960s and 1970s, is demonstrated. Under certain conditions, the model predicts significant long-range attractive or repulsive interactions between hypothetical proteins with strong preferences for one or the other state that are bound to well-separated sites on the same DNA. A scenario is proposed for the activation of the ilvPG promoter on a supercoiled DNA by integration host factor.

Magnetic Cooperative Phenomenon with Unpaired sp-Electrons System by MBE Low-Temperature Growth

We present a new possibility of crystal growth as synthesis of materials containing high concentrations of unpaired sp electrons by growth of Be doped Gallium Arsenides at low temperatures of 200-3000C using Molecular Beam Epitaxy (MBE) and investigate a possibility of applications of magnetotransport properties based on these unpaired sp-electrons to spintronics devices.The present study using high concentration of unpaired sp-electrons by the growth of Beryllium-doped GaAs layers at low temperatures resulted in a cooperative transition of localized spins at low temperature and also affected the mechasnism of tranport properties of the sample from hopping conduction to valence band conduction.This attempts will give rise to a possibility of adding new functions to existing electronic devices.

Protein Structural Dynamics of Wild-Type and Mutant Homodimeric Hemoglobin Studied by Time-Resolved X-Ray Solution Scattering

The quaternary transition between the relaxed (R) and tense (T) states of heme-binding proteins is a textbook example for the allosteric structural transition. Homodimeric hemoglobin (HbI) from Scapharca inaequivalvis is a useful model system for investigating the allosteric behavior because of the relatively simple quaternary structure. To understand the cooperative transition of HbI, wild-type and mutants of HbI have been studied by using time-resolved X-ray solution scattering (TRXSS), which is sensitive to the conformational changes. Herein, we review the structural dynamics of HbI investigated by TRXSS and compare the results of TRXSS with those of other techniques.

Cooperative spin-crossover transition from three-dimensional purely π-stacking interactions in a neutral heteroleptic azobisphenolate FeIII complex with a N3O3 coordination sphere

The first neutral spin-crossover FeIII complex with a N3O3 coordination sphere formed a purely π-stacking interaction network and exhibited the cooperative transition.