Dynamic aspect of bacteriorhodopsin as a typical membrane protein as revealed by site-directed solid-state 13C NMR

We demonstrate here a general feature of dynamic aspect of membrane proteins as revealed by site-directed 13C NMR studies on bacteriorhodopsin (bR) as a typical membrane protein and a variety of mutants at ambient temperature. 13C NMR signals of [3-13C]Ala- or [1-13C]Val-labeled proteins were assigned regio-specifically with reference to the data of the conformation-dependent 13C chemical shifts from model polypeptides, followed by site-specific assignment based on site-directed mutants. Revealed picture of membrane protein at ambient temperature is not static in contrast to anticipation from crystalline structures but flexible enough to undergo a variety of local fluctuations with frequencies from 10(2) to 10(8)Hz, as pointed out already. This picture was further refined by taking into account of residue-specific dynamics of interfacial domains between the surface and inner part of the transmembrane helices and conformational fluctuation induced by the presence of a kinked structure. The residue-specific dynamics of the former was revealed by observation of broadened or suppressed peaks from the interfacial domains caused by acquisition of internal fluctuation motions interfered with frequencies of proton decoupling or magic angle spinning. The presence of such suppressed peaks due to molecular fluctuations in the interfacial domains was further confirmed by insensitivity of the peak-intensities from the interfacial domains in spite of the presence of accelerated relaxation rate to nearby residues from surface bound Mn2+ ion. Further, conformational change of the transmembrane alpha-helix F due to a plausible kinked structure at Pro 186 was confirmed in view of specific displacements of Ala 184 and Val 187 13C NMR peaks from chemically synthesized [3-13C]Ala(184)-, [1-13C]Val(187)-labeled wild type and P186L mutant of transmembrane fragment F(164-194) incorporated into lipid bilayer. It is emphasized that the observed displacement of [3-13C]-labeled Ala 184 peak at 17.4 ppm in the presence of kinked structure in this model peptide is consistent with that of intact protein at 17.27 ppm.     

Intramolecular nonbonded S?O interaction in acetazolamide and thiadiazolinethione molecules in their dimeric crystalline structures and complex crystalline structures with enzymes

The dimeric crystalline structure of acetazolamide 1 and thiadiazolinethione 2 bearing intramolecular nonbonded S?O interactions, in each different hydrogen-bonding manner was clarified by their X-ray crystallographic analysis. Existence of the dimeric structure of 1 and 2 in a MeOH solution could be suggested on the basis of their cold-spray ionization mass spectrometry. The intramolecular nonbonded S?O interaction was precisely recognized in the complex crystalline structures of carbonic anhydrase I inhibitor 1 and stromelysin inhibitors 2-4 with each specific enzyme. The computational evaluation of the possible monomeric seven conformers of 1 and two model compounds 5 and 6 of 2-4 based on DFT calculations defined that the conformer bearing the intramolecular nonbonded S?O interaction is most stable.     

Formation of eta'(958)-mesic nuclei and axial UA(1) anomaly at finite density

We discuss the possibility of producing the bound states of the eta'(958) meson in nuclei theoretically. We calculate the formation cross sections of the eta' bound states with the Green function method for the (gamma, p) reaction and discuss the experimental feasibility at photon facilities such as SPring-8. We conclude that we can expect to observe resonance peaks in (gamma, p) spectra for the formation of eta' bound states and we can deduce new information on eta' properties at finite density. These observations are believed to be essential to know the possible mass shift of eta' and deduce new information on the effective restoration of the chiral UA(1) anomaly in the nuclear medium.     

Some considerations on fuzzy conditional inference

In much of human reasoning, the form of reasoning is approximate rather than exact as in ‘A red apple is ripe and this apple is more or less red. Then this apple is more or less ripe.’L.A. Zadeh and E.H. Mamdani suggested methods for such a fuzzy reasoning as an application of fuzzy set theory. The method involves an inference rule and a conditional proposition which contains fuzzy concepts.In this paper we point out that the consequence inferred by their methods does not always fit our intuitions and we suggest the improved methods which fit our intuitions under several criteria.     

A simple synthesis of fluorescent uridines by photochemical method

A strongly fluorescent 5-pyrenyluridine was prepared by the photoreaction of 2′,3′-0-isopropylidene-5-iodouridine with pyrene. Several fluorescent analogues of uracil were synthesized by similar procedures.     

Well defined superlattice structures made by phase-locked epitary using RHEED intensity oscillations

Long continuing intensity oscillations of the RHEED pattern in the [100] azimuth on a (001) oriented substrate were observed during MBE growth of GaAs and Al_xGa_1−xAs. Using these oscillations, growth rates of GaAs and Al_xGa_1−xAs, and the Al mole fraction x of the Al_xGa_1−xAs were accurately monitored during the growth. The phase of the RHEED oscillations was analyzed by computer and molecular beam shutters were operated at a particular phase of the oscillations. This computer controlled phase-locked epitaxy (PLE) was used to grow precisely defined (GaAs)₂(AlAs)₂ bi-layer superlattices. Raman scattering spectra of the bi-layer superlattice showed split lines characteristic of superlattices. From TEM observation of a GaAs-AlAs multi-layered structure, it was verified that one cycle of oscillations corresponds to one monolayer growth of GaAs and AlAs. This PLE has a great advantage over the conventional MBE growth method for the precise control of very thin films and superlattice structures because it is invulnerable to fluctuations of molecular beam flux intensity.     

A new synthetic method for 7α-methoxycephalosporins

A new synthetic route for 7α-methoxy-7β-acylaminocephalosporins is described.