EVENTS SURROUNDING THE EARLY DEVELOPMENT OF EUGLENA CHLOROPLASTS. 12. SPECTROSCOPIC EXAMINATION OF THE PROTOCHLOROPHYLL(IDE) PHOTOTRANSFORMATION IN INTACT CELLS*

Abstract— Absorption measurements in the 600–720 nm region of dark-grown cells of Euglena gracilis Klebs var. bacillaris Cori were made in vivo at room temperature using computer-assisted spectrophotometry. Dark-grown wild-type cells have a prominent absorption maximum at 634 nm due to protochlorophyll(ide) absorption. Upon illumination, the absorption at 634nm decreases and a peak appears at 674nm, representing the phototransformation of protochlorophyll(ide) to chlorophyll(ide). Using difference spectroscopy, the resynthesis in the dark of protochlorophyll(ide) by previously-illuminated wild-type dark-grown cells was found to begin at about 10min after illumination and reached completion by about 25 min, the amount of protochlorophyll(ide) resynthesized being equivalent to that of dark-grown cells. Resynthesis of protochlorophyll(ide) following a second illumination follows the same kinetics, indicating that protochlorophyll(ide) resynthesis is under tight regulation, possibly via feedback control. Cells of dark-grown wild-type and W₃BUL, a mutant lacking protochlorophyll(ide) contain a component absorbing at 658 nm which does not undergo phototransformation when examined by difference spectroscopy at room and liquid N₂ temperatures. Following the phototransformation of protochlorophyll(ide) 634 to chlorophyll(ide) 674, the chlorophyll(ide) 674 shifts to shorter wavelengths, ultimately to 671 nm. Possible relationships among the various spectroscopic forms of protochlorophyll(ide) and chlorophyll(ide) at room temperature and liquid N₂ temperature in Euglena and higher plants are presented. It is concluded that Euglena, unlike older, etiolated higher plants, contains only protochlorophyll(ide) 634, making it an excellent system in which to examine the phototransformation of this pigment species in the absence of other forms.     

Weak itinerant magnetism as inhibited superconductivity

Thep-state pairing idea proposed recently to explain the ferromagnetism of ZrZn₂ is described in more detail, and the underlying soft-mode hypothesis is examined in relation with experiments, in particular the discovery of antiferromagnetism in TiBe₂. The key result, namely an electron-phonon contribution to the Stoner factor given essentially by the mass enhancement factor, is used to explain the behaviour of the Curie pointT _m and to predict an isotope effect.p-state superconductivity with a transition temperature determined by is predicted in TiBe₂ and, above the critical pressure whereT _m =0, also in ZrZn₂.Work in La Jolla supported by NSF/DMR 77-08469.     

On the asymptotic behavior of solutions of a mildly nonlinear parabolic system

In this paper we study the asymptotic behavior of solutions to the mixed initial boundary value problem for the system of nonlinear parabolic equations

$\text{?u}{}_{\mathrm{t}}\text{+Lu=f(x.t.u.v)}\text{?v}{}_{\mathrm{t}}\text{+Mv=g(x,t,u,v)}$

We show, under suitable technical assumptions, that these solutions converge to solutions of the Dirichlet problem for the corresponding limiting elliptic system, provided that the solution of the Dirichlet problem is unique.     

Synthesis of Halopyrazole Matrine Derivatives and Their Insecticidal and Fungicidal Activities

Matrine is a traditional botanical pesticide with a broad-spectrum biological activity that is widely applied in agriculture. Halopyrazole groups are successfully introduced to the C13 of matrine to synthesize eight new derivatives with a yield of 78–87%. The insecticidal activity results show that the introduction of halopyrazole groups can significantly improve the insecticidal activity of matrine on Plutella xylostella, Mythimna separata and Spodoptera frugiperda with a corrected mortality rate of 100%, which is 25–65% higher than matrine. The fungicidal activity results indicate that derivatives have a high inhibitory effect on Ceratobasidium cornigerum, Cibberella sanbinetti, Gibberrlla zeae and Collectot tichum gloeosporioides. Thereinto, 4-Cl-Pyr-Mat has the best result, with an inhibition rate of 23–33% higher than that of matrine. Therefore, the introduction of halogenated pyrazole groups can improve the agricultural activity of matrine.     

The structure of vapour-quenched GdAg alloys containing between 0 and 16 at% silver

The structures of non-crystalline vapour-quenched GdAg alloy films containing between 0 and 16 at% silver have been examined by X-ray diffraction techniques. Radial distribution functions calculated from the experimental data, are in general appearance similar to those generated from a binary hard-sphere model derived from random layers of unequal-sized spheres for all compositions except those near 13 at% Ag. A hard-sphere model proposed by Sadoc et al. [13] generated from a seed cluster gives better agreement in the region of 13 at% Ag. Magnetic measurements show a Curie-Weiss behaviour for the magnetic susceptibility with p_eff = 7.6 ± 1.9 μ_B for these alloys.     

CHARACTERIZATION OF AN ACRYLAMIDE MODIFIED ETHYL ACRYLATE LATEX BY CARBON-13 NMR SPECTROSCOPY

The structure of a 70/30 ethyl acrylate-acrylamide latex made in a semi-continuous process with surfactant has been investigated. The molar composition and relative concentration of the polymers in the serum phase, on the surface and in the particle were characterized by coupling a filtration procedure, serum replacement, with carbon-13 NMR spectroscopy. The development of polymer in the different phases could be monitored by taking samples at timed intervals during the polymerization. Post-treatment of the latex with sodium hydroxide selectively hydrolyzed the copolymerized ethyl acrylate in the serum and on the surface. By measurement of spin lattice relaxation times it was possible to estimate surface concentration of oligomeric polymer     

Anion effects on the phase transition of N‐isopropylacrylamide hydrogels

NMR spectra were collected for poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel using high‐resolution magic angle spinning (HRMAS) after gel pieces were hydrated in the presence of D₂O, NaF, NaCl, and NaI aqueous solutions. Changes in the peak height intensity of the spectra provide quantitative insight into the phase transition process. The thermodynamic values of the phase transition were calculated using a van't Hoff analysis of the NMR data. Unlike the trend observed for decreases in the (LCST), changes in the enthalpy and entropy did not clearly display a linear dependence with respect to salt concentration. Rather, it was observed that increases in salt concentration did not affect the enthalpy and entropy to the extent as the initial change observed between no salt and 100 mM solutions. Finally, the effect of salts on the hysteresis of the rehydrating process was observed. Hysteresis occurs due to the need for hydrophobic interactions to break down before water is able to infiltrate the polymer matrix. NaF stabilizes hydrophobic interactions while NaI destabilize hydrophobic interactions, causing them to break down at higher temperatures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012