No abstract

Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of neutron-drip line have been measured using the RIBF facility at RIKEN. Measurements have been performed for 20–32 Ne on C target at energies around 240 MeV/nucleon. A large enhancement of σI beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes. The possible halo structures with lower orbital angular momentum for 29,31 Ne are discussed by the preliminary analysis.

A 'metal-free' chlorophyll (Chl) a, pheophytin (Phe) a, functions as the primary electron acceptor in PS II. On the basis of Phe a/PS II = 2, Phe a content is postulated as an index for estimation of the stoichiometry of pigments and photosystems. We found Phe a in a Chl d-dominant cyanobacterium Acaryochloris marina, whereas Phe d was absent. The minimum Chl a:Phe a ratio was 2:2, indicating that the primary electron donor is Chl a, accessory is Chl d, and the primary electron acceptor is Phe a in PS II of A. marina. Chl d was artificially formed by the treatment of Chl a with papain in aqueous organic solvents. Further, we will raise a key question on the mechanisms of water oxidation in PS II.

The secondary electron acceptor of photosystem (PS) I in the cyanobacterium Gloeobacter violaceus PCC 7421 was identified as menaquinone-4 (MQ-4) by comparing high performance liquid chromatograms and absorption spectra with an authentic compound. The MQ-4 content was estimated to be two molecules per one molecule of chlorophyll (Chl) a 0 , a constituent of P700. Comparative genomic analyses showed that six of eight men genes, encoding phylloquinone/MQ biosynthetic enzymes, are missing from the G. violaceus genome. Since G. violaceus clearly synthesizes MQ-4, the combined results indicate that this cyanobacterium must have a novel pathway for the synthesis of 1,4-dihydroxy-2-naphthoic acid.

Bacillus subtilis alpha-amylase signal peptide, which consists of 33 amino acids, is functional in Escherichia coli cells. Lysine, glutamic acid, leucine, leucyl-leucine, or leucyl-leucyl-leucine was inserted between positions 28 and 29 of the alpha-amylase signal peptide using site directed mutagenesis. DNAs encoding the wild-type and modified signal peptides were then fused in-frame to DNAs encoding the mature regions of the beta-lactamase of pBR322 and a thermostable alpha-amylase. The secretion of beta-lactamase in E. coli cells was more inhibited by the modified signal peptides than that in B. subtilis cells, although the degree of inhibition varied and the inhibitory effect of each signal peptide was found to be similar in the two strains. In contrast, the difference in the inhibitory effect of each modified signal peptide was no longer detected in the case of the production of thermostable alpha-amylase, except for the insertion of glutamic acid. Nearly 50% of thermostable alpha-amylase in the precursor form was accumulated in the intracellular fraction of E. coli cells containing the DNAs for the modified signal peptides. The insertion of glutamic acid inhibited the secretion of the two enzymes in both B. subtilis and E. coli cells.