Chloroplast Biogenesis 77: Two Novel Monovinyl and Divinyl Light-Dark Greening Groups of Plants and Their Relationship to the Chlorophyll a Biosynthetic Heterogeneity of Green Plants

Abstract— On the basis of the steady-state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl-light divinyl (DDV-LDV), dark monovinyl-light divinyl (DMV-LDV) and dark monovinyl-light monovinyl (DMV-LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211-220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV-LDV and DMV-LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re-darkening, this greening group is designated as a light-dark MV (LDMV) subgroup. In DDV-LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light-dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4-vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase-A (POR-A) may be active in LDDV plants, while POR-B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed.     

Circular dichroism of 9,10-dihydrophenanthrene derivatives reveals both the absolute configuration and conformation: a novel approach to Mislow's helicity rule

The absolute configuration and the conformation of 9,10-trans-disubstituted 9,10-dihydrophenanthrenes, known chiral metabolites of phenanthrene-9,10-oxide, have been determined by circular dichroism. The absolute configuration assignment is based on the sign of the long-wavelength Cotton effect (A-band), which is conformation invariant and originates from benzylic chirality. This provides a new interpretation of the Mislow biphenyl-helicity rule for the case of the 9,10-dihydrophenanthrene chromophore. The sign of the B-band Cotton effect reflects the conformation of the biphenyl chromophore in 9,10-dihydrophenanthrenes. It is shown that the origin of chiroptical properties of 9,10-dihydrophenanthrenes is closely related to those of 5,6-trans-disubstituted 1,3-cyclohexadienes.     

Microanalysis of Volatile Organic Compounds (VOCs) in Water Samples – Methods and Instruments

Volatile organic compounds (VOCs), due to their toxicity and persistence in the environment, are particularly important pollutants. Some of these compounds are mutagens, teratogens or carcinogens, while others are responsible for the degradation of organoleptic parameters such as taste and odour of water. This review focuses on a number of key procedural steps in the analysis of volatile organic compounds (VOCs) in water samples. A wide spectrum of techniques for the isolation and preconcentration of the aforementioned pollutants for trace organic analysis by gas chromatography are presented and discussed. The advantages and disadvantages of these techniques are discussed and novel developments are also taken into consideration.     

Ramsey partitions of integers and pair divisions

Ifk ₁ andk ₂ are positive integers, the partitionP = (₁,₂,..., _n ) ofk ₁+k ₂ is said to be a Ramsey partition for the pairk ₁,k ₂ if for any sublistL ofP, either there is a sublist ofL which sums tok ₁ or a sublist ofP –L which sums tok ₂. Properties of Ramsey partitions are discussed. In particular it is shown that there is a unique Ramsey partition fork ₁,k ₂ having the smallest numbern of terms, and in this casen is one more than the sum of the quotients in the Euclidean algorithm fork ₁ andk ₂.An application of Ramsey partitions to the following fair division problem is also discussed: Suppose two persons are to divide a cake fairly in the ratiok ₁k ₂. This can be done trivially usingk ₁+k ₂-1 cuts. However, every Ramsey partition ofk ₁+k ₂ also yields a fair division algorithm. This method yields fewer cuts except whenk ₁=1 andk ₂=1, 2 or 4.     

Extending the coordination chemistry of molecular P(4)S(3): the polymeric Ag(P(4)S(3))(+) and Ag(P(4)S(3))(2)(+) cations

Upon reacting P(4)S(3) with AgAl(hfip)(4) and AgAl(pftb)(4) [hfip = OC(H)(CF(3))(2); pftb = OC(CF(3))(3)], the compounds Ag(P(4)S(3))Al(hfip)(4) 1 and Ag(P(4)S(3))(2)(+)[Al(pftb)(4)](-) 2 formed in CS(2) (1) or CS(2)/CH(2)Cl(2) (2) solution. Compounds 1 and 2 were characterized by single-crystal X-ray structure determinations, Raman and solution NMR spectroscopy, and elemental analyses. One-dimensional chains of [Ag(P(4)S(3))(x)](infinity) (x = 1, 1; x = 2, 2) formed in the solid state with P(4)S(3) ligands that bridge through a 1,3-P,S, a 2,4-P,S, or a 3,4-P,P eta(1) coordination to the silver ions. Compound 2 with the least basic anion contains the first homoleptic metal(P(4)S(3)) complex. Compounds 1 and 2 also include the long sought sulfur coordination of P(4)S(3). Raman spectra of 1 and 2 were assigned on the basis of DFT calculations of related species. The influence of the silver coordination on the geometry of the P(4)S(3) cage is discussed, additionally aided by DFT calculations. Consequences for the frequently observed degradation of the cage are suggested. An experimental silver ion affinity scale based on the solid-state structures of several weak Lewis acid base adducts of type (L)AgAl(hfip)(4) is given. The affinity of the ligand L to the silver ion increases according to P(4) < CH(2)Cl(2) < P(4)S(3) < S(8) < 1,2-C(2)H(4)Cl(2) < toluene.     

From Weakly Coordinating to Non‐Coordinating Anions? A Simple Preparation of the Silver Salt of the Least Coordinating Anion and Its Application To Determine the Ground State Structure of the Ag(η2‐P4)2+ Cation

The unexpected but facile preparation of the silver salt of the least coordinating [(RO)₃Al‐F‐Al(OR)₃]^? anion (R=C(CF₃)₃) by reaction of Ag[Al(OR)₄] with one equivalent of PCl₃ is described. The mechanism of the formation of Ag[(RO)₃Al‐F‐Al(OR)₃] is explained based on the available experimental data as well as on quantum chemical calculations with the inclusion of entropy and COSMO solvation enthalpies. The crystal structures of (RO)₃Al←OC₄H₈, Cs⁺[(RO)₂(Me)Al‐F‐Al(Me)(OR)₂]^?, Ag(CH₂Cl₂)₃⁺[(RO)₃Al‐F‐Al(OR)₃]^? and Ag(η²‐P₄)₂⁺[(RO)₃Al‐F‐Al(OR)₃]^? are described. From the collected data it will be shown that the [(RO)₃Al‐F‐Al(OR)₃]^? anion is the least coordinating anion currently known. With respect to the fluoride ion affinity of two parent Lewis acids Al(OR)₃ of 685 kJ mol^?1, the ligand affinity (441 kJ mol^?1), the proton and copper decomposition reactions (?983 and ?297 kJ mol^?1) as well as HOMO level and HOMO–LUMO gap and in comparison with [Sb₄F₂₁]^?, [Sb(OTeF₅)₆]^?, [Al(OR)₄]^? as well as [B(R^F)₄]^? (R^F=CF₃ or C₆F₅) the [(RO)₃Al‐F‐Al(OR)₃]^? anion is among the best weakly coordinating anions (WCAs) according to each value. In contrast to most of the other cited anions, the [(RO)₃Al‐F‐Al(OR)₃] anion is available by a simple preparation in conventional inorganic laboratories. The least coordinating character of this anion was employed to clarify the question of the ground state geometry of the Ag(η²‐P₄)₂⁺ cation (D_2h, D₂ or D_2d?). In agreement with computational data and NMR spectra it could be shown that the rotation along the Ag‐(P‐P‐centroid) vector has no barrier and that the structure adopted in the solid state depends on packing effects which lead to an almost D_2h symmetric Ag(η²‐P₄)₂⁺ cation (0 to 10.6° torsion) for the more symmetrical [Al(OR)₄]^? anion, but to a D₂ symmetric Ag(η²‐P₄)₂⁺ cation with a 44° twist angle of the two AgP₂ planes for the less symmetrical [(RO)₃Al‐F‐Al(OR)₃]^? anion. This implies that silver back bonding, suggested by quantum chemical population analyses to be of importance, is only weak.     

Structurally heterogeneous electrode films of polyacrylamide and acrylamide/vinylpyridine copolymeric gels: Mediation of ascorbic acid oxidation

The surface chemistry, i.e. adsorption and surface phase formation, on Rh, Ir, Pt and Au single-crystal electrodes in 0.5 M H₂SO₄ has been studied in the potential range between 0 and 4 V vs. a standard hydrogen electrode by X-ray photoelectron spectroscopy and cyclic voltammetry. Both methods gave complementary results which were interpreted as potential-dependent changes from physisorption of water to adsorption of hydroxyl groups, hydroxide film formation, and eventual growth of thick adlayers of oxyhydroxide (Rh, Ir and Au) or hydroxide (Pt) with increasing applied voltage.     

Thermolytic carbonates for potential 5'-hydroxyl protection of deoxyribonucleosides

Thermolytic groups structurally related to well-studied heat-sensitive phosphate/thiophosphate protecting groups have been evaluated for 5'-hydroxyl protection of deoxyribonucleosides as carbonates and for potential use in solid-phase oligonucleotide synthesis. The spatial arrangement of selected functional groups forming an asymmetric nucleosidic 5'-O-carbonic acid ester has been designed to enable heat-induced cyclodecarbonation reactions, which would result in the release of carbon dioxide and the generation of a nucleosidic 5'-hydroxyl group. The nucleosidic 5'-O-carbonates 3-8, 10-15, and 19-21 were prepared and were isolated in yields ranging from 45 to 83%. Thermolytic deprotection of these carbonates is preferably performed in aqueous organic solvent at 90 degrees C under near neutral conditions. The rates of carbonate deprotection are dependent on the nucleophilicity of the functional group involved in the postulated cyclodecarbonation reaction and on solvent polarity. Deprotection kinetics increase according to the following order: 4 < 5 < 10 < 6 < 12 < 7 < 13 < 8 < 14 congruent with 19-21 and CCl4 < dioxane < MeCN < t-BuOH < MeCN:phosphate buffer (3:1 v/v, pH 7.0) < EtOH:phosphate buffer (1:1 v/v, pH 7.0). Complete thermolytic deprotection of carbonates 7, 8, 13, and 14 is achieved within 20 min to 2 h under optimal conditions in phosphate buffer-MeCN. The 2-(2-pyridyl)amino-1-phenylethyl and 2-[N-methyl-N-(2-pyridyl)]aminoethyl groups are particularly promising for 5'-hydroxyl protection of deoxyribonucleosides as thermolytic carbonates.     

Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10⁻² S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10⁻¹ and 1.78 × 10⁻¹ S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.