Dynamics of water structure in biological system are explained from experimental results obtained from broadband dielectric spectroscopy (BDS). BDS measuring technique makes it possible to observe molecular dynamics in totalized time/frequency range of 200 ks-0.2 ps /1 μHz-1 THz, and is still developed to offer precise and stable measuring system. The BDS measurement looks best to observe slow dynamics of various water structures restricted and/or confined in molecular complex systems such as biological system. Topics on aquametry, confinement, freezing, supercooling, glass transition, etc. are described from the concept of dynamical behavior of complex system.
We have determined the structure of GGA triplet repeat DNA under physiological conditions and found the formation of an intramolecular parallel quadruplex for the first time. The quadruplex comprises a new architecture, G(:A):G(:A):G(:A):G heptad. Minisatellite DNA Pc-1 forms a quadruplex, and thus causes pausing of DNA polymerase during replication. We have found that hnRNP A1 protein can transform the quadruplex to a single strand, and thus abrogate the pausing. In this case, hnRNP A1 functions as if it is a chaperon for DNA, "DNA chaperon". hnRNP A1 and hnRNP D proteins may also function as the DNA chaperons in elongation of telomere DNA.
The chemical and thermal unfolding of pyrrolidone carboxyl peptidase from hyperthermophile (PfPCP) is completely reversible with drastically slow unfolding and refolding rates. The higher thermodynamic stability of the hyperthermophile protein compared to homologous protein from mesophile is characterized by the unusually slow unfolding rate. It is revealed that the stability of the hyperthermophile protein is under kinetic control.
Taste bud cells senses taste substances even if they separately occur on tongues. However, taste bud cells gather to form taste buds. In-situ patch clamp recordings showed that mouse taste bud cells elicited either depolarizing or hyperpolarizing receptor potentials in response to taste stimuli, and in-situ optical recordings revealed a tendency that mouse taste bud cells gather by the polarity of their receptor potentials. They expressed functional gap junctions, glutamate receptors, and serotonin receptors on their basolateral membranes. It is likely that mouse taste bud cells make cell networks to regulate taste transduction mechanisms.
Olfactory receptors (ORs), which comprise the largest G protein-coupled receptor family, play a pivotal role in recognizing a variety of odorants in the vertebrate olfactory system. Recent successes in functional cloning and expression of ORs facilitated construction of ligand-activity matrices of ORs. Activation of a combinatorial receptor repertoire by an odorant determines an odor quality of the odorant, while activated ORs by an odorant mixture is not simply the sum of those for its components due to OR antagonism between odorants. Mixing odorants, thereby, often results in a novel perceptual quality that is not present in each component. The recent atomic-level structure for bovine rhodopsin has provided an opportunity to elucidate a molecular basis for odorant recognition by an OR and characterize the active site of an OR.