Flash photolysis electron spin resonance studies of the electron acceptor species at low temperatures in Photosystem I of spinach subchloroplast particles

The light-induced electron spin resonance signals of Photosystem I spinach subchloroplast particles have been studied at approximately 6 °K. Using the technique of flash photolysis-electron spin resonance with actinic illumination at 647 nm, a kinetic analysis of the previously observed bound ferredoxin ESR signals was carried out. Signal I (P700⁺) exhibits a partial light-reversible behavior at 6 °K so it was expected that if the bound ferredoxin is the primary acceptor of Photosystem I, it should also exhibit a partial reversible behavior. However, none of the bound ferredoxin ESR signals showed any such light reversible behavior. A search to wider fields revealed two components which did exhibit the expected kinetic behavior. These components are very broad (about 80 G) and are centered at g = 1.75 and g = 2.07. These two components exhibit the expected characteristics of the primary electron acceptor. A model is presented to account for the reversible and irreversible photochemical changes in Photosystem I. The possible identity of the primary acceptor responsible for these two new components, is discussed in terms of the available information. The primary acceptor may be an iron-sulfur protein, but not of the type characteristic of the bound or water-soluble ferredoxins found so far in chloroplasts.     

Photokinesis and Photophobic Responses in the Gliding Flagellate, Euglena mutabilis

A pronounced photokinesis (as indicated by increases in bothpercentage of motile cells and average speed of movement) aswell as step-up and step-down photophobic responses at light/darkboundaries in the gliding flagellate Euglena mutabilis was studiedusing time-lapse video-microscopy. The spectral sensitivitiesof all the observed lightdependent motor responses were similarto each other and showed an activity throughout the whole visiblespectrum with maximum peaks at about 410, 450, 470, 530, 580and 650 nm and a pronounced minimum at about 600 nm. Thus, thephotoreceptor pigments markedly differ from the closely relatedswimming flagellate Euglena gracilis in which a flavin typeblue light receptor is supposed to be responsible for the stimulusperception. Light microscopic studies of mucilage distributionand regeneration suggested that the gliding movements are effectedby parallel gliding of adjacent pellicular strips while themucilage produced on the cell surface and transported to therear end seems to be responsible for adhesion of the cell onthe substrate. (Received November 21, 1985; Accepted January 30, 1986)     

Chiral macrocyclic compounds from lactose derivatives

The reaction of benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-β-lactoside with 1,11-ditosyloxy-3,6,9-trioxaundecane gave benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-3,2′-O--(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (2, 47%). Acid hydrolysis of 2 and condensation of the product with 1,14-ditosyloxy-3,6,9,12-tetra-oxatetradecane afforded benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-(3,6,9,12-tetraoxa-tetradecane-1,14-diyl)-3,2′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (29%). Similarly, the reaction of benzyl 2,6,2′,4′,6′-penta-O-benzyl-β-lactoside with Ts[OCH₂CH₂]₄OTs gave benzyl 2,6,2′,4′,6′-penta-O-benzyl-3,3′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (78%). ¹H-N.m.r. spectroscopy has been used to study the formation of host-guest complexes with some of these macrocyclic compounds and benzyl ammonium thiocyanate.     

Calcium-activated potassium channels in chondrocytes.

The presence of calcium-activated potassium channels in chondrocytes of growing cartilage was tested. Results obtained with fura-2 on cultured resting chondrocytes indicate that the cells respond to an elevation of extracellular calcium concentration ([Ca2+]o) from 0.1 to 2 mM increasing the intracellular concentration of the ion ([Ca2+]i) from 117 to 187 nM. This increment may be blocked by 3 microM La3+. Patch clamp experiments in cell-attached configuration showed that, when [Ca2+]i rises, the open probability (Po) of the K+ channels increases. Increments in both Po and unitary currents of the K+ channels can be obtained after applying 2.5 microM A23187 with 2 mM [Ca2+]o. Hence, the results demonstrate that, in chondrocytes, a class of Ca(2+)-activated K+ channels is present and their activity is related to an increase of [Ca2+]i.     

Evaluation of Chemicals for Restricting Colony Spreading by a Xerophilic Mold, Eurotium amstelodami, on Dichloran-18% Glycerol Agar

Twenty chemicals were screened for their effectiveness in restricting colony spreading by four strains of a xerophilic mold, Eurotium amstelodami, on dichloran-18% glycerol agar. Triton X-100, Triton X-301, Tergitol NP-7, and Tergitol 15-S-3 (each at 200 μg/ml) and 1,000 μg of sodium deoxycholate, 1 μg of iprodione, 0.1 μg of propiconazole, and 0.01 μg of Maxim per ml were judged to be most effective for restricting the rate of colony spreading.     

Carotenoid composition and photon-use efficiency of photosynthesis inGossypium hirsutum L. grown under conditions of slightly suboptimum leaf temperatures and high levels of irradiance

Summary Cotton (Gossypium hirsutum L. var. DP 61) was grown at different temperatures during 12-h light periods, with either 1800–2000 mol photons m^–2 s^–1 (high photon flux density, PFD) or 1000–1100 mol m^–2 s^–1 (medium PFD) incident on the plants. Night temperature was 25°C in all experiments. Growth was less when leaf temperatures were below 30°C during illumination, the effect being greater in plants grown with high PFD (Winter and Königer 1991). Leaf pigment composition and the photon-use efficiency of photosynthesis were analysed to assess whether plants grown with high PFD and suboptimal temperatures experienced a higher degree of high irradiance stress during development than those grown with medium PFD. The chlorophyll content per unit area was 3–4 times less, and the content of total carotenoids about 2 times less, with the proportion of the three xanthophylls zeaxanthin + antheraxanthin + violaxanthin being greater in leaves grown at 20–21°C than in leaves grown at 33–34°C. In leaves from plants grown at 21°C and 1800–2000 mol photons m^–2 s^–1, zeaxanthin accounted for as much as 34% of total carotenoids in the middle of the photoperiod, the highest level recorded in this study. This finding is consistent with a protective role of zeaxanthin under conditions of excess light. At the lower temperatures, the photochemical efficiency of photosystem II, measured as the ratio of variable to maximum fluorescence yield (F _V/F _M) after 12-h dark adaptation, was 0.76 in medium PFD plants and 0.75 in high PFD plants compared with 0.83 and 0.79, respectively, at the higher temperatures. The photon-use efficiency of O₂ evolution () based on absorbed light between 630 and 700nm, decreased with decrease in temperature from 0.102 to 0.07 under conditions of high PFD, but remained above 0.1 at medium PFD. Owing to compensatory reactions in these long-term growth experiments, sustained differences inF _V/F _M and were much less pronounced than the differences in chlorophyll content and dry matter, particularly in plants which had developed at high PFD and low temperature. In fact, in these plants, which exhibited pronounced photobleaching, a largely functional photosynthetic apparatus was still maintained in cells adjacent to the lower leaf surfaces. This was indicated by measurements of photon use efficiencies of photosynthetic O₂ evolution with leaves illuminated first at the upper, and then at the lower surface.Abbreviations F _O yield of dark level fluorescence - F _M maximum yield of fluorescence, induced in a pulse of saturating light - F _V yield of variable fluorescence (=F _M-F _o) - PFD photon flux density - _iw photon use efficiency of O₂ evolution based on white (400–700 nm) incident light - _ir photon use efficiency based on red (630–700 nm) incident light - _aw photon use efficiency based on white absorbed light - _ar photon use efficiency based on red absorbed light     

Isolation,physical map and gene map of mitochondrial DNA from the cryptomonad Pyrenomonas salina

Mitochondrial DNA (mtDNA) from the cryptomonad Pyrenomonas salina was isolated by CsCl-buoyant density centrifugation of whole-cell DNA in the presence of Hoechst dye 33258. mtDNA consists of circular molecules about 47 kb in size as estimated from restriction enzyme analysis. A physical map for six restriction enzymes (Bam HI, Bge I, Eco RI, Pst I, Sac I and Sac I) has been constructed. Genes coding for the small subunit of rRNA, cytochrome oxidase subunits I and II, and apocytochrome b were localized on this map using Southern blot hybridization with heterologous gene probes from Oenothera. Genes for 5S rRNA and NADH dehydrogenase subunit 5 are absent from P. salina mtDNA. The mitochondrial genome, being the first analysed to this extent in chromophytic algae, should be valuable for taxonomic and phylogenetic studies.     

Molybdenum-dependent degradation of quinoline by Pseudomonas putida Chin IK and other aerobic bacteria

Eighteen different aerobic bacteria were isolated which utilized quinoline as sole source of carbon, nitrogen, and energy. Attempts were unsuccessful at isolating anaerobic quinoline-degrading bacteria. The optimal concentration of quinoline for growth was in the range of 2.5 to 5 mM. Some organisms excreted 2-hydroxyquinoline as the first intermediate. Hydroxylation of quinoline was catalyzed by a dehydrogenase which was induced in the presence of quinoline or 2-hydroxyquinoline. Quinoline dehydrogenase activity was dependent on the availability of molybdate in the growth medium. Growth on quinoline was inhibited by tungstate, an antagonist of molybdate. Partially purified quinoline dehydrogenase from Pseudomonas putida Chin IK indicated the presence of flavin, iron-sulfur centers, and molybdenum-binding pterin. M _r of quinoline dehydrogenase was about 300 kDa in all isolates investigated.Abbreviations APS ammonium peroxodisulfate - DCPIP 2,6-dichlorophenol-indophenol - EEO electroendosmosis - MTT thiazolyl blue - PES phenazine ethosulfate - TEMED N,N,N,N-tetramethyl-ethylenediamine     

Non-isotopic detection of chromosome 1 in human meiosis and demonstration of disomic sperm nuclei

Summary Nonradioactive in situ hybridization with the biotin-labeled chromosome 1-specific probe pUC1.77 was performed on human mitotic and meiotic chromosomes, and on sperm nuclei. The streptavidine-horseradish-peroxidase and diaminobenzidine detection system demonstrated heteromorphisms in the Iq12 heterochromatic region, not only in mitotic cells but also in mature sperm heads. The localization of chromosome 1 could be traced through all meiotic stages and in the sperm nuclei. The frequency of chromosome 1 disomy in human sperm, as indicated by two distinct hybridization signals, was calculated to be 0.41%.