A ferredoxin-type iron-sulfur protein gene,frx B,is expressed in the chloroplasts of tobacco and spinach

Previously, a ferredoxin-type iron-sulfur protein, frx B protein, was identified in a high-salt extract of the purified thylakoid membrane of Chlamydomonas reinhardtii, a unicellular green alga. Polyclonal antibody was raised against a synthetic pentadecameric peptide with an amino acid sequence corresponding to the highly conserved region of the putative frx B proteins of 3 land plants [21]. In this report, protein(s) reacting strongly and specifically with this antibody was detected in the equivalent high-salt extract prepared from purified chloroplast of spinach and tobacco. One strong reaction polypeptide band from tobacco chloroplast was purified from SDS-polyacrylamide gel and subjected to endoproteinase lys C digestion. The resulting polypeptides were separated by reversed-phase chromatography. N-terminal sequencing of 3 purified polypeptides revealed that the protein is encoded by the frxB gene identified from DNA sequence analysis.     

Analysis of time-resolved fluorescence anisotropy in lipid-protein systems

Fluorescent probes located in heterogeneous environments give rise to anomalous time-resolved fluorescence anisotropy. A simple analytical expression of anisotropy has been derived for the case of a small difference in local fluorescence lifetimes. The expression has the diagnostic advantage that the time dependence of the fluorescence anisotropy can be predicted from the differences in fluorescence lifetimes and residual anisotropies of the probes located in different sites. Using this model, the local fluorescence anisotropy parameters and the relative contributions of the lipid probe octadecyl rhodamine B in a lipid environment and in the vicinity of bacteriophage M13 coat protein reconstituted in phospholipid bilayers, composed of 80% 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 20% 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol have been determined experimentally. At 40°C, the correlation times for bound and free probes are 2.3 and 3.0 ns, respectively, while the corresponding order parameters are 0.85 and 0.62, respectively.Abbreviations ESR electron spin resonance - DMPC 1,2-dimyristoyl-sn-glycero-3-phosphocholine - DMPC 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol - L/P ratio phospholipid to coat protein molar ratio - <> average fluorescence lifetime - r(0) initial anisotropy - r() residual anisotropy On leave of Shanghai Medical Equipment Research Institute, 77 Jiang Ning Rd. Shanghai, People's Republic of China Offprint requests to: M. A. Hemminga     

Different influences of cytochalasin B on the activation of human neurophils settled onto petri dishes displayed by simultaneously detected native and luminol-dependent luminescence

Cytochalasin B (CB) is known to interfere reversibly with the cytoplasmic contractile filamental network of mammalian cells. The role of the microfilament system in the mechanism of the reactive oxygen intermediates release of polymorphonuclear leukocytes (PMNL) was studied for different kinds of stimuli. PMNL from fresh human blood were treated with CB and stimulated by adherence on plastic surfaces, by opsonized zymosan, by phorbol myristate acetate and by N-formylmethionyl-phenylalaline. The production of reactive oxygen species were monitored by simultaneous detection of native, luminol-independent, luminescence (NL) and luminol-dependent luminescence (LDL) using a method of spectral discrimination. Different influences of CB on NL with respect to LDL as well stimuli-dependent influences of CB on the luminescence response of PMNL were observed. Especially phagocytosis-associated activation of PMNL was strongly inhibited by CB, whereas LDL was reduced to a much greater extent in comparison with NL. A firm involvement of the microfilament system is indicated, but it depends on the kind of stimulus engaged.     

A sensitive and rapid luminescence sandwich assay for antibodies to hepatitis-B surface antigen (Anti-HBsAg)

A chemiluminescent assay for hepatitis-B surface antigen is described which used an isoluminol derivative as the label. The assay is precise intra-assay CV, 1.96-2.45%; inter-assay CV, 5.26-8.11% and has a lower detection limit for hepatitis-B surface antigen of 1.3U/I.     

Activation of m1 Muscarinic Acetylcholine Receptor Regulates τ Phosphorylation in Transfected PC12 Cells

Abstract: Hyperphosphorylated τ proteins are the principal fibrous component of the neurofibrillary tangle pathology in Alzheimer's disease. The possibility that τ phosphorylation is controlled by cell surface neurotransmitter receptors was examined in PC12 cells transfected with the gene for the rat m₁ muscarinic acetylcholine receptor. Stimulation of m₁ receptor in these cells with two acetylcholine agonists, carbachol and AF102B, decreased τ phosphorylation, as indicated by specific τ monoclonal antibodies that recognize phosphorylation-dependent epitopes and by alkaline phosphatase treatment. The muscarinic effect was both time and dose dependent. In addition, a synergistic effect on τ phosphorylation was found between treatments with muscarinic agonists and nerve growth factor. These studies provide the first evidence for a link between the cholinergic signal transduction system and the neuronal cytoskeleton that can be mediated by regulated phosphorylation of τ microtubule-associated protein.     

Nucleotide sequence and presumed secondary structure of the 28S rRNA of pea aphid implication for diversification of insect rRNA

Determination of the entire nucleotide sequence of the aphid 28S ribosomal RNA gene (28S rDNA) revealed that it is 4,147 by in length with a G + C content of 60.3%. Based on the nucleotide sequence, we constructed a presumed secondary-structure model of the aphid 28S rRNA which indicated that the aphid 28S rRNA is characterized by the length and high G + C content of its variable regions. The G + C content of the aphid's variable regions was much higher than that of the entire sequence of the 28S rRNA, which formed a striking contrast to those ofDrosophila with the G + C content much lower than the entire 28S molecule. In this respect, the aphid 28S rRNA somewhat resembled those of vertebrates. This is the third report of a complete large-subunit rRNA sequence from an arthropod, and the first 28S rRNA sequence for a nondipterous insect. Correspondence to: H. Ishikawa     

Clean technology in aquaculture — a production without waste products?

A method has been developed for the determination of H₂S and FeS in sediments. FeS is converted into H₂S which is flushed from the samples directly into an excess of chlorine bleach, NaC1O or KClO with some Zn²⁺ added. Either the excess can be titrated back potentiometrically with As₂O₃, or the sulphate formed can be measured colorimetrically. The precision is primarily controlled by the homogeneity of the sediment suspensions and can be better than 99%.