Light saturation curves and quantum yields in reaction centers from photosynthetic bacteria.

Reaction centers isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26 mutant were irradiated with laser pulses of variable energy and the amount of photooxidation of the primary electron donor bacteriochlorophyll was measured. The resultant light saturation curve fits an exponential function and not a hyperbolic or hyperbolic tangent function. Analysis using either a Poisson statistical model or a simple kinetic model predicts an exponential light saturation curve in the limit where the light pulse is long relative to any transient intermediate states. The absolute quantum yield of photochemistry was found to be 0.98, utilizing the entire light saturation curve. Distortions from the simple exponential light saturation behavior are predicted when very short laser pulses are used.     

Structure of defective DNA molecules in Epstein-Barr virus preparations from P3HR-1 cells.

Epstein-Barr virus (EBV), isolated from P3HR-1 cells, induces early antigen and viral capsid antigen upon infection of human B-lymphoblasts. The strong early antigen- and viral capsid antigen-inducing activity is only observed in P3HR-1 virus preparations harboring particles with defective genomes, suggesting that this biological activity is directly associated with the defective DNA population. After infection of EBV genome-carrying Raji or EBV genome-negative BJAB cells, defective genomes of P3HR-1 EBV DNA are replicated in excess, depending on the multiplicity of infecting EBV particles. Hybridization of the DNA from such infected cells with 32P-labeled EBV DNA after HindIII cleavage reveals six hypermolar fragments. Mapping of these fragments shows that they form one defective genome unit containing four nonadjacent regions (alpha, beta, gamma, and delta) of the nondefective P3HR-1 EBV DNA. Two of the segments (alpha and beta) contain ca. 17 and 13 megadaltons, respectively, from the terminal regions of the P3HR-1 genome, whereas the two smaller segments (gamma and delta) contain ca. 3.7 and 3.0 megadaltons, respectively, originating from the central portion of the genome. In the defective molecule, the regions gamma and delta are present in the opposite orientation compared with nondefective P3HR-1 EBV DNA. Tandem concatemers are formed by fusion of the alpha and beta regions. Our model suggests that tandem concatemers of three defective genome units can be packaged into virions in P3HR-1 cells.     

Characterization of newly isolated monoclonal antibodies against MHC of a Japanese wild mouse

We have already developed nine B10.MOL congenic strains carrying H-2 haplotypes derived from Japanese wild mice, Mus musculus molossinus, with the C57BL/10 genetic background. To obtain monoclonal antibodies against the H-2 antigen of the Japanese wild mouse, we carried out cell fusion using spleen cells from the animal immunized with one of the B10.MOL strains, B10.MOL-SGR (H-2 ^wm7). As a result, 19 hybridomas producing monoclonal antibodies were produced. Analysis with the intro-H-2 recombinants derived from B10.MOL-SGR indicated that 8 of them reacted with the class I and II with the class II molecule. The class I antibodies were tested for their cross -reactivities on wild mice and on the panels of standard inbred and B10.MOL strains. Most of the antibodies reacted with both the Japanese wild mice and the other subspecies, including standard inbred, while two antibodies highly specific for the donor H-2K region reacted with only three wild-derived mice, two M. m. molossinus from Anj o and Shizuoka, Japan, and one M. m. domesticus from Pigeon, Canada. In addition, all of the other four antibodies reactive with the K antigen of B10.MOL-SGR also reacted with the same three wild mice. The wild mice belonging to different subspecies might share very similar H-2K antigenic determinants in spite of their genetic and geographical remoteness.     

Effect of gamma-ray irradiation on alcohol production from corn

Cracked corn was irradiated with gamma rays at 0-100 Mrad and the effects of the irradiation on sugar yield, susceptibility to enzymatic hydrolysis of starch, yeast growth, and alcohol production were studied. Gamma irradiation at 50 Mrad or greater produced a considerable amount of reducing sugar but little glucose. At lower dosages, gamma irradiation significantly increased the susceptibility of corn starch to enzymatic hydrolysis, but dosages of 50 Mrad or greater decomposed the starch molecules as indicated by the reduction in iodine uptake. About 12.5% reducing sugar was produced by amylase treatment of uncooked, irradiated corn. This amount exceeded the level of sugar produced from cooked (gelatinized) corn by the same enzyme treatment. The yeast numbers in submerged cultivation were lower on a corn substrate that was irradiated at 50 Mrad or greater compared to that on an unirradiated control. About the same level of alcohol was produced on uncooked, irradiated (10(5)-10(6) rad) corn as from cooked (121 degrees C for 30 min) corn. Therefore, the conventional cooking process for gelatinization of starch prior to its saccharification can be eliminated by irradiation. Irradiation also eliminated the necessity of sterilization of the medium and reduced the viscosity of high levels of substrate in the fermentation broth.     

Immobilization of glucoamylase and glucose oxidase in activated carbon: effects of particle size and immobilization conditions on enzyme activity and effectiveness

Glucoamylase and glucose oxidase have been immobilized on carbodiimide-treated activated carbon particles of various sizes. Loading data indicate nonuniform distribution of immobilized enzyme within the porous support particles. Catalysts with different enzyme loading and overall activities have been prepared by varying enzyme concentration in the immobilizing solution. Analysis of these results by a new method based entirely upon experimentally observable catalyst properties indicates that intrinsic catalytic activity is reduced by immobilization of both enzymes. Immobilized glucoamylase intrinsic activity decreases with increasing enzyme loading, and similar behavior is suggested by immobilized glucose oxidase data analysis. The overall activity data interpretation method should prove useful in other immobilized enzyme characterization research, especially in situations where the intraparticle distribution of immobilized enzyme is nonuniform and unknown.     

Respiratory depression produced by centrally administered taurine in the cat

The effects of taurine (0.8-64.8 mumol) were studied on respiratory activity following intracisternal (cisterna magna) and intracerebroventricular (lateral ventricle) injections in cats anesthetized with alpha-chloralose. Respiratory activity was measured by using a Fleisch pneumotachograph and monitoring tracheal airflow. The flow signal was integrated to obtain tidal volume (VT) and respiratory rate (f) was obtained by counting the number of VT excursions over one minute. Inspiratory (TI), expiratory (TE) and total (TTOT) cycle durations were also determined during this time period. In addition, end-tidal CO2 was continuously monitored. Associated changes in arterial pressure (femoral artery cannula) and heart rate were also determined. After injections into the cisterna magna, taurine caused dose-related decreases in minute ventilation (VE). The maximal decrease in VE was from 495 +/- 59 to 64 +/- 14 ml/min (p less than 0.05), and was due to both decreases in VT (from 27 +/- 3 to 5 +/- 1 ml; p less than 0.05) and f (from 18 +/- 1 to 12 +/- 2 breaths/min; p less than 0.05). TE and TTOT were increased from 2.4 +/- 0.4 to 4.5 +/- 0.6 sec (p less than 0.05) and from 3.7 +/- 0.4 to 6.4 +/- 0.8 sec (p less than 0.05), respectively. Mean inspiratory flow (VT/TI), a measure of inspiratory drive, was decreased from 21 +/- 4 to 4 +/- 2 ml/sec (p less than 0.05). Apnea occurred in 5 of 6 animals after the 64.8 mumol dose. This respiratory depression occurred without any significant change in arterial pressure. After lateral ventricle injections, taurine also caused dose-related, but not as pronounced, decreases in respiratory activity. In addition, taurine caused significant decreases (p less than 0.05) in arterial pressure in doses that decreased VE. Taurine administered intravenously had no significant cardiorespiratory depressant effects. These data indicate that centrally administered taurine produces respiratory depression and, depending on the route of CNS administration, also produces hypotension.     

Enhancement by Putrescine of Gibberellin-Induced Elongation in Hypocotyls of Lettuce Seedlings

Effects of diamines, polyamines, and other basic amino acidson the growth of lettuce hypocotyls were investigated. Putrescine,cadaverine and agmatine enhanced the hypocotyl growth in thepresence of gibberellin, while spermidine and spermine werenon-effective. Arginine and ornithine, which may be precursorsof putrescine, had similar effect. While the growth inhibitiondue to arcaine (1,4-diguanidinobutane), which is a agmatineiminohydrolase inhibitor, was recovered by agmatine, cadaverine,putrescine, and spermidine, putrescine most effectively recoveredits growth-enhancing effect. (Received August 25, 1982; Accepted December 27, 1982)     

Effects of Cytokinin and Several Inorganic Cations on the Polyamine Content of Lettuce Cotyledons

Kinetin (4.7 x 10^–5 M) and 6-benzyladenine (2.22 x 10^–5M) were found to increase ca. 2-fold the putrescine contentin cotyledons of lettuce (Lactuca sativa L.) seedlings grownfor 3 days under fluorescent light. On the other hand, severalinorganic ions (K⁺, Na⁺, Ga⁺⁺, Mg⁺⁺) at a concentration of 3x 10^–2 M reduced the putrescine content. The combinationof kinetin with one of several inorganic ions at the same levelmarkedly increased the spermine content, but the putrescinecontent decreased; calcium and magnesium ions were less effective.The physiological significance of these findings is discussed. (Received July 4, 1982; Accepted November 6, 1982)