IN VIVO CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND THE CIRCADIAN RHYTHM OF PHOTOSYNTHESIS IN GONYAULAX POLYEDRA

Abstract— The intensity of chlorophyll a fluorescence during the early part of fluorescence induction at O , initial fluorescence, and P, peak fluorescence, was higher during the day phase of the circadian cycle than during the night phase in continuous light (LL) conditions and was positively correlated with the rate of oxygen evolution. The circadian rhythm in fluorescence in LL persisted in the presence of 10μM 3–(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), which blocks electron flow from photo-system (PS) II in photosynthesis. The rhythmic changes in fluorescence intensity are consistent with a lower rate constant for radiationless transitions during the day phase than during the night phase of the circadian rhythmicity. The circadian changes in the intensity of fluorescence were abolished at 77K, which may indicate the importance of structural changes in membranes in circadian oscillations.     

Thermal stabilities of isoelectronic,isostructural nitrates,carbonates and borates

The effects of temperature changes on an isoelectronic, iso-structural group of compounds containing an iso-electronic, iso-structural complex of ions were studied. The stability of the nitrates is discussed on the basis of their temperature of fusion and solid state transitions; the carbonates from their decomposition temperatures and solid state transitions; and the borates on solid state transitions. The order of thermal stabilities is found to be ABO₃ > A′ CO₃ > A″ NO₃ .     

Asymmetric [2,3]-rearrangement of glycine-derived allyl ammonium ylids

The first examples of highly enantioselective [2,3]-sigmatropic rearrangements of acyclic allylic ammonium ylids are reported. Thus, a range of N-{2'-[(N'-allyl-N',N'-dialkyl)ammonium]}acetyl camphor sultams undergo rearrangement at 0 degrees C in DME solution with high diastereofacial control (up to 99:1 dr) to give allylglycines in generally high yield. The power of the method has been demonstrated in a rapid and efficient synthesis of (R)-allyl glycine.     

Electrospray ionization mass spectrometry studies of noncovalent myosin VI complexes reveal a new specific calmodulin binding site

Among the myosin superfamily, myosin VI differs from all others by a reverse directionality and a particular motility. Little structural information is available for myosin VI. It is known that it binds one calmodulin (CaM) by means of a single "IQ motif" and that myosin VI contains a specific insert located at the junction between the motor domain (MD) and the lever arm, likely to play a critical role for the unusual motility previously observed. Electrospray ionization mass spectrometry (MS) was used to determine the CaM and Ca2+ stoichiometries in several myosin VI constructs. In particular, the experimental conditions required for the observation of multiprotein/Ca2+ noncovalent assemblies are detailed for two truncated MD constructs (less than 20 kDa) and for three full MD constructs (more than 90 KDa). The specificity of the detected stoichiometries is discussed for each construct and the resolving power of Time of Flight mass spectrometry is stressed, in particular for the detection of metal ions binding to high molecular weight complexes. MS reveals a new CaM binding site for myosin VI and highlights a different behavior for the five myosin VI constructs versus Ca2+ binding. In addition to these stoichiometry based experiments, gas-phase dissociation analyses on intact complexes are described. They reveal that Ca2+ transfer between protein partners occurs during the dissociation process for one construct with a full MD. Charge-transfer and dissociation behavior has allowed to draw structural assumptions for the interaction of the MD with the CaM N-terminal lobe.     

The Reaction of Bicyclo [3.2.1] octenyl Halides with Metal Hydrides

Reduction of 2-phenyl- and 2-methyl-exo-3,4-dichlorobicyclo[3.2.1]oct-2-enes with lithium aluminium hydride (LAH) or tributyltin hydride (TBTH) gave endo-2-phenyl-3-chlorobicyclo[3.2.1]oct-3-ene, 2-phenyl-3-chlorobicyclo[3.2.1]oct-2-ene and their methyl analogues. The action of both reagents on 2-phenyl-exo-3, 4-dibromobicyclo[3.2.1]oct-2-ene similarly resulted in reductive monodebromination to give normal and allylically rearranged products. Additionally, further reduction occurred to give endo-2-phenylbicyclo[3.2.1]oct-3-ene and 2-phenylbicyclo[3.2.1]-oct-2-ene. In all cases, LAH gave mainly the allylic rearrangement product whereas TBTH gave mostly unrearranged product. The reason for these differences could have been due either to the intervention of allylic radicals in the TBTH reduction or to differences in nucleophilicity. The results also show that LAH is equally efficaceous as TBTH in the reduction of these allylic halides and equally selective in the reduction of the vinyl bromides. The stereochemistry of the allylic rearrangement was shown to be synfacial in that hydride replaced halide on the same face of the molecule.     

Greener synthesis using hydrogen peroxide in ethyl acetate of alicyclic ring-fused benzimidazoles and anti-tumour benzimidazolequinones

Environmentally-friendly and cost effective hydrogen peroxide in ethyl acetate was used to prepare in high yields pyrrolo[1,2-a]benzimidazoles from commercial o-(pyrrolidin-1-yl)anilines without the requirement for organic-aqueous extraction and chromatography. Six, seven and eight membered ring-fused analogues were similarly obtained in high yields with methanesulfonic acid required for the pyrido[1,2-a]benzimidazole. Anti-tumour benzimidazolequinone derivatives were obtained in high yield via the cyclization of 3,6-dimethoxy-2-(cycloamino)anilines.     

Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles

This review article provides a perspective on the synthesis of alicyclic and heterocyclic ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles, and imidazo[5,4-f]benzimidazoles. These heterocycles have a plethora of biological activities with the iminoquinone and quinone derivatives displaying potent bioreductive antitumor activity. Synthesis is categorized according to the cyclization reaction and mechanisms are detailed. Nitrobenzene reduction, cyclization of aryl amidines, lactams and isothiocyanates are described. Protocols include condensation, cross-dehydrogenative coupling with transition metal catalysis, annulation onto benzimidazole, often using CuI-catalysis, and radical cyclization with homolytic aromatic substitution. Many oxidative transformations are under metal-free conditions, including using thermal, photochemical, and electrochemical methods. Syntheses of diazole analogues of mitomycin C derivatives are described. Traditional oxidations of o-(cycloamino)anilines using peroxides in acid via the t-amino effect remain popular.     

A rapid method for analysis of non-equilibrated 90Sr/90Y in infant formula

Journal of Radioanalytical and Nuclear Chemistry - A rapid analytical method for quantifying 90Sr in infant formula prior to secular equilibrium is presented. The approach is dependent on the use...     

An ideal column algorithm for integer programs with special ordered sets of variables

One of the most frequently occurring integer programming structures is the one which has special ordered sets of variables included in multiple choice constraints. For problems with this structure a set of ideal columns are defined from the linear programming relaxation of the integer program and a reduced integer program is formed by keeping only those columns within a specified distance from the ideal column. Conditions are established which guarantee when the optimal solution to the reduced problem is als optimal for the original problem. When these conditions are not satisfied, bounds on the optimal solution value are provided. Ideal columns are also used to establish weights for the special ordered set variables. This procedure has been implemented through a control program written by the authors for MPSX/370-MIP/370. Computational results are given.