Studies of the pyrolysis of tetraethylammonium tetrahydroborate

Tetraethylammonium tetrahydroborate, Et₄NBH₄, in suspension in refluxing decane-dodecane mixtures has been pyrolysed at temperatures between 175 and 190 °C. Et₃NBH₃, which is produced by partial decomposition of Et₄NBH₄, reacts with Et₄NBH₄ to give the intermediate Et₄NB₃H₈. Et₄NBH₄ and Et₃NBH₃ are also involved in the conversion of Et₄NB₃H_8. to (Et₄N)₂B₉H₉, (Et₄N)₂B₁₀H₁₀, Et₄NB₁₁H₁₄ and (Et₄N)₂B₁₂H₁₂ which are formed in varying proportions during the pyrolysis. A 1:1 Et₄NBH₄Et₃NBH₃ mixture gives the same mixture of final products in the same proportions as Et₄NBH₄ alone, but the reaction time is shorter.Results obtained under various conditions, for instance without solvent at 10⁻² torr (50% yield), are explained by the transfer of BH₃ groups occurring not only through Et₃NBH₃, but also by solid—solid reactions involving Et₄NBH₄. A more complete reaction of Et₃NBH₃ is obtained, giving quantitative yields, only when Et₃N is evacuated from the reaction mixture. Optimum conditions for the formation of each hydroborate are examined.     

Receptor of the serpentine-type and heterotrimeric G protein as targets of action of polylysine dendrimers

Molecular processes of the action of polycationic peptides that represent polylysine homo- and heterodendrimers on the functional activity of the biogenic amine- and peptide hormone-sensitive adenylyl cyclase signaling system (AC system) in rat myocardium and brains were studied. An intended use of these peptides is that of highly effective polymer carriers for biologically active substances. The polylysine homodendrimers of the third [(NH₂)₁₆(Lys)₈(Lys)₄(Lys)₂Lys-Ala-NH₂] (I), fourth [(NH₂)₃₂(Lys)₁₆(Lys)₈(Lys)₄(Lys)₂Lys-Ala-NH₂] (II), and fifth [(NH₂)₆₄(Lys)₃₂(Lys)₁₆(Lys)₈(Lys)₄(Lys)₂Lys-Ala-NH₂] (III) generations, as well as polylysine heterodendrimers of the fifth generation, [(NH₂)₆₄(Lys-Glu)₃₂(Lys-Glu)₁₆(Lys-Glu)₈(Lys-Glu)₄(Lys-Glu)₂Lys-Ala-Ala-Lys(ClAc)-Ala-NH₂] (IV), [(NH₂)₆₄(Lys-Ala)₃₂(Lys-Ala)₁₆(Lys-Ala)₈(Lys-Ala)₄(Lys-Ala)₂Lys-Ala-Lys(ClAc)-Ala-Ala-NH₂] (V) and [(NH₂)₆₄(Lys-Gly-Gly)₃₂(Lys-Gly-Gly)₁₆(Lys-Gly-Gly)₈(Lys-Gly-Gly)₄(Lys-Gly-Gly)₂Lys-Gly-Gly-Lys(ClAc)-Ala-Ala-NH₂] (VI), interact with the C-terminal regions of α subunits of the heterotrimeric G proteins, preferably of the inhibitor type, and stimulate its activity in respector-independent manner. The most effective G-protein activators were homodendrimers II and III and heterodendrimer V. The polylysine dendrimers disturbed the functional coupling of receptors of biogenic amines and peptide hormones with G_i proteins and, to a lesser extent, G_s proteins. This was manifested as a decrease in the regulatory effects of the hormones on AC activity and the GTP binding of the G protein, as well as by a decrease in the affinity of receptors to agonists in the presence of polylysine dendrimers, which is a consequence of the dissociation of the receptor-G protein complex. It has also been shown that, based on their molecular mechanisms and selectivity of action on G proteins, polylysine dendrimers are similar to mastoparan and melittin, which are natural toxins of insect venom.     

Specificity of the interaction of DNA-platinum, amount of platinum, and pH measurement]

Interaction between the sodium salt of a DNA extracted from salmon sperm (41% GC) with [Pt(NH₃)₄]Cl₂, [Pt(NH₂? (CH₂)₂? NH? (CH₂)₂? NH₂Cl]Cl, cis-Pt(NH₂? (CH₂)₂? NH₂)Cl₂, cis-Pt(NH₃)₂Cl₂, trans-Pt(NH₃)₂Cl₂, K[Pt(C₂H₄)Cl₃], and K₂[PtCl₄) indicates at least three types of complexation. A correlation is found between the change of pH and the number of platinum atoms fixed per (AT + GC) unit. The first binding site is located on the G-C pairs (guanine–cytosine), most likely the N-7(G) site, as it was shown in a previous study of the guanosine-platinum salts. The fixation of the second platinum atom by the pair (AT + GC) takes place with liberation of protons. In the case of the complexes cis-Pt(NH₂? (CH₂)₂? NH₂)Cl₂, cis-Pt(NH₃)₂Cl₂, and trans-Pt(NH₃)₂Cl₂ the second interaction seems to involve simultaneously the N-7(A) and the N-1(G) and N-3(C) sites. This latter intercrosslink between guanine and cytosine obviously liberates protons and the decrease of pH is related in this case to the trans effect of the platinum compounds. The first two platinum atoms in the reaction of K₂PtCl₄] or the Zeise salt, K[Pt(C₂H₄)Cl₃] with DNA are fixed on the G-C pairs. A maximum of six platinum atoms per (AT + GC) unit were fixed in this case. Preliminary experiments with a DNA extracted from bacteria Micrococcus lysodeikticus (72% GC) give similar results.     

Preparation of mono- or di-metal indenyl-iridium edrivatives and of tri-metal iridium-platinum complexes

Treatment of [IrCl(C₂H₄)₄] with K(C₉H₇) (C₉H₇ =indenyl) gives [Ir(C₂H₄)₂(η-C₉H₇)]. This compound is converted quantitatively into [Ir(CO)₂(η-C₉H₇)] by treatment with carbon monoxide. By reacting together these two iridium complexes [Ir₂(μ-CO)(CO)₂(ηC₉H₇)₂] has been obtained. The compound [Ir(CO)₂(η-C₉H₇)] reacts with [Pt(C₂H₄)₂{P(cyclo-C₆H₁₁)₃}] to give the complex [Ir₂Pt(CO)₃{P(cyclo-C₆H₁₁)₃}(η-C₉H₇)₂]. Protonation of the latter affords the salt [Ir₂Pt(μ-H)(CO)₃{P(cyclo-C₆H₁₁)₃}(μ-C₉H₇)₂] [BF₄]. The main features of the molecular structure of these complexes have been established by IR and NMR spectroscopy.     

Modeling aspects of hydrodesulfurization by molybdenum hydride compounds: Desulfurization of thiophene and benzothiophene and C-S bond cleavage of dibenzothiophene

The molybdenum hydride complexes Mo(PMe₃)₅H₂ and Mo(PMe₃)₄H₄ are capable of cleaving the C-S bonds of thiophene, benzothiophene and dibenzothiophene. For example, Mo(PMe₃)₅H₂ reacts with thiophene to give the η⁵-thiophene and butadiene-thiolate complexes, (η⁵-C₄H₄S)Mo(PMe₃)₃ and (η⁵-C₄H₅S)Mo(PMe₃)₂(η²-CH₂PMe₂). These complexes are also obtained from the reaction between Mo(PMe₃)₄H₄ and thiophene under photochemical conditions, whereas at elevated temperatures thiophene is desulfurized to liberate but-1-ene. Similarly, Mo(PMe₃)₄H₄ desulfurizes benzothiophene at elevated temperatures to liberate ethylbenzene, while the arylthiolate complex Mo(PMe₃)₄(SC₆H₄Et)H₃ is obtained photochemically. Furthermore, Mo(PMe₃)₄H₄ cleaves the C-S bond of dibenzothiophene to give [η⁶,κ¹-C₆H₅C₆H₄S]Mo(PMe₃)₂H.     

Enhancement of BKCa channel activity induced by hydrogen peroxide: Involvement of lipid phosphatase activity of PTEN

Large-conductance calcium and voltage-dependent potassium (BK_Ca) channel is an important determinant of vascular tone. It is activated by hydrogen peroxide (H₂O₂) which occurs in various physiological and pathological processes. However, the regulation mechanism is not fully understood. In the present study, the mSlo in the presence or absence of hβ1 were cotransfected with the PTEN_wt, PTEN_C124S, PTEN_G129E in HEK 293 cells. Typical BK_Ca channel currents could be recorded in cell-attached configurations. We found that PTEN_wt reduced the H₂O₂-induced BK_Ca channel activation during the initial 10 min treatment. In contrast, coexpression with catalytically inactive PTEN_C124S/PTEN_G129E mutants that lack lipid phosphatase activity produced no regulation on the H₂O₂-induced BK_Ca channel activation. These results demonstrated that PTEN regulated the H₂O₂-induced BK_Ca channel activation through phosphatidylinositol 3-phosphatse. However, the inhibitory effect of PTEN on the H₂O₂-induced BK_Ca channel activation was attenuated when cells were treated with H₂O₂ at concentrations higher than 100 μM or at 100 μM for long-term treatment. In addition, the p-AKT expression level in PTEN_wt overexpressing cells was lower than that in control cells, and the increase of cytoplasmic free calcium concentration ([Ca²⁺]_i) induced by H₂O₂ was also inhibited. These findings may elucidate a new mechanism for H₂O₂-induced BK_Ca channel activation and provide some evidences for the role of PTEN on vasodilation induced by H₂O₂.     

Spectroscopical identification of residues of subunit G of the yeast V-ATPase in its connection with subunit E

A critical point in the V₁ sector and entire V₁V_O complex is the interaction of stalk subunits G (Vma10p) and E (Vma4p). Previous work, using precipitation assays, has shown that both subunits form a complex. In this work, we have analysed the N-terminal segment of subunit G (G_1–59) of the V₁V_O ATPase from Saccharomyces cerevisiae by using nuclear magnetic resonance (NMR) spectroscopy. Analyses of ¹H-¹⁵N heteronuclear single quantum coherence (HSQC) spectra of G_1–59 in the absence and presence of the N-terminal peptides E_1–18 and E_18–38 as well as the produced and purified C-terminal segment (E_39–233) shows specific interactions only with the peptide fragment E_18–38. The binding of this peptide occurs via the residues M₁, V₂, S₃, and K₅ as well for V₂₂, S₂₃, K₂₄, A₂₅ and R₂₆ of G_1–59. The specific E_18–38/G_1–59 binding has been confirmed by fluorescence correlation spectroscopy data. The E_18–38 peptide has been studied by CD spectroscopy and NMR. The 3D structure of this peptide adopts a stable helix-hinge-helix formation in solution. A model structure of the E_18–38/G_1–59 complex reveals the orientation of E_18–38 relative to G_1–59 via salt-bridges of the polar residues and van der Waals forces at the very N-terminus of both segments.     

Kinetics and mechanism of alkali-induced decomposition of 2-alkoxyethylcobaloximes

Kinetics of the base-induced decomposition of five 2-alkoxyethyl(aquo)cobaloximes, ROCH₂CH₂- Co(D₂H₂)OH₂ (R = C₆H₅, CF₃CH₂, CH₃, CH₃CH₂, (CH₃)₂CH), have been studied manometrically in aqueous base, ionic strength 1.0 M (KC1) at 25.0± 0.1 °C under an argon atmosphere. For the complexes with good leaving group alkoxide substituents (R = C₆H₅ and CF₃CH₂) the reactions are first- order in cobaloxime and first-order in hydroxide ion and produce stoichiometric amounts of ethylene and leaving group alcohol (ROH). NMR observation of decomposing solutions and workup of cobalt chelate products show that the reaction is initiated by hydroxide ion attack on an equatorial quaternary carbon leading to formation of an altered cobal- oxime product in which one of the Schiff's base linkages has become hydrated. For the remainer of the complexes the yield of ethylene is less than stoichiometric and pH-dependent, and the ethylene evolving reaction is second-order in hydroxide ion activity. The yield-limiting side reaction is shown to be base-catalyzed formation of a base-stable but photolabile alkoxyethylcobaloxime analog in which a Schiff's base linkage of the chelate has become hydrated, β-Elimination to form alkyl vinyl ethers was not observed for any of the alkoxyethylcobal- oximes. The second-order dependence of ethylene formation on hydroxide ion activity for R = CH₃, CH₂CH₃, and CH(CH₃)₂ is discussed at some length, but is not well understood at present.     

Assay of molybdenum cofactor of barley

Conditions for assay of molybdenum cofactor in barley shoot extracts in the presence of molybdate (25 mM N₂MoO₄) and the sulphydryl-group protector, reduced glutathione (5 mM) were optimized. Both total Mo-cofactor (assayed after heat-treatment of cell-free extracts) and ‘free’ Mo-cofactor (assayed in untreated cell-free extracts) were assayed. Compared to control plants grown in the absence of an exogenous nitrogen source total Mo-cofactor levels increased around 70 % when plants were grown for 4 days in the presence of either 15 mM KNO₃ or 15 mM NH₄NO₃. Growth in the presence of 15 mM (NH₄)₂SO₄ did not affect the Mo-cofactor level. Very similar results were seen when plants were transferred to these nitrogen sources for 24 hr after previous growth in the absence of an exogenous nitrogen source. In contrast ‘free’ Mo-cofactor levels of both KNO₃ and NH₄NO₃-treated plants were increased 2-3-fold over untreated controls. Growth in the presence of (NH₄)₂SO₄ did not affect the ‘free’ Mo-cofactor level.     

Proton magnetic resonance studies of the conformational changes of dideoxynucleoside ethyl phosphotriesters

PMR investigations on the diastereomeric phosphate methyl protons of the dinucleoside ethyl phosphotriesters Tp(C₂H₅)T, dA, and dIp(C₂H₅)dI have been used to study the conformational changes of these dimersin solution. In D₂O (273°K), the diastereomeric phosphate-methly groups of Tp(C₂H₅)T appear as a triplet. The methyl resonances of dIp(C₂H₅)dI and dAp(C₂H₅)dA appear as two sets of triplets and their chemical shift differences (δ₁ ? δ₂), decrease with increasing temperature, finally becoming zero at 292°K and 333°K, respectively. The same phenomenon is observed for dAp(C₂H₅)dA in CD₃OD; in this detacking solvent, the difference (δ₁ ? δ₂) diminishes to zero at a lower temperature (261°K). At room temperature in D₂O, the chemical shift of the phosphate methyl of Tp(C₂H₅)T appears at lower field than those of dIp(C₂H₅)dI or dAp(C₂H₅)dA. The differences between the chemical shifts of these groups (δ_I ? δ_T or δ_A ? δ_T) increase with increasing temperature, and reach maximal values at 301°K and 333°K, respectively. The results suggest that at low temperature the largest fraction of the dimer population exists in a stacked state, with the phosphate-ethyl groups outside the stack. Increasing temperature causes an oscillation of the bases and a shift in the dimer population away from the stacked state. Finally at high temperature, the planar bases rorate with respect to one another and in the case of dIp(C₂H₅)dI and dAp(C₂H₅)dA, the ethyl groups experience shielding by the anisotropic ring current of the five-membered ring of the bases. Thus, the current pmr studies and those reported earlier from our laboratory support an “oscillation-rotation model” for the unstacking process of the dimers. The relationship of this model and the “two-state model” is discussed.     

Detection of genotoxicity of metallic compounds by the bacterial bioluminescence test

Twenty metallic compounds were assayed for their genotoxic mutagenic activity by the bioluminescence test restoration of the luminescence of dark mutant of the luminous bacterium Photobacterium fischeri). The activity of the metals was tested in a liquid medium as well as on a solid medium. K₂Cr₂O₇, MnCl₂, BeCl₂, KH₂AsO₄, ZnCl₂ and Na₂WO₄ showed strong activity in liquid medium while AgNO₃, Cd(OOCCH₃)₂, CoCl₂, CuCl₂, HgCl₂, Na₂SeO₃ and Pb(NO₃)₂ were more active in the solid medium test. BaCl₂, Na₂MoO₄, NaAsO₂, NiSO₄, Na₂SeO₄, RbCl, and SnCl₂ were not active in the bioluminescence test. The correlation between the genotoxic activity of the tested metallic compounds in the bioluminescence test and other bacterial tests for genotoxic agents as well as the correlation between these results and the carcinogenicity of these compounds is discussed.     

Characterization of ribonucleoprotein subparticles from 50 S ribosomal subunits of Escherichia coli.

Large ribonucleoprotein subparticles were recovered upon ribonuclease digestion of the 50 S ribosomal subunits of Escherichia coli, partially deproteinized by LiCl. Both their RNA and their protein compositions were analysed. The subunits, treated with LiCl at a concentration of 5.5 m, released an homogeneous subparticle containing proteins L₃, L₄, L₁₃, L₁₇, L₂₂ and L₂₉, about 70% of the 13 S fragment of 23 S RNA and about 50% of the 18 S one. Slightly larger species of subparticles were obtained from 50 S subunits treated with LiCl at concentrations between 3 m and 5 m; they contained in addition proteins L₂₀, L₂₁ and L₂₃ or L₂, L₁₄, L₂₀, L₂₁ and L₂₃ and a few small 23 S RNA fragments. No large subparticle was recovered from the 6 m-LiCl-treated 50 S subunits which contain only proteins L₃, L₁₃ and L₁₇. These LiCl subparticles were compared with those obtained from intact, unfolded and sodium doecyl sulphatetreated 50 S subunits.These studies reveal that in the presence of 0.10 m-magnesium acetate there is a very compact area within 50 S subunits consisting of proteins L₃, L₄, L₁₃, L₁₇, L₂₂ and L₂₉ and of about 60% of 23 S RNA; this area probably has an essential structural role. The results also show that 23 S RNA has a more folded conformation when within the 50 S subunit than when isolated, this conformation being stabilized by some of the 50 S proteins, in particular proteins L₄, L₂₂, L₂₀ and L₂₁. Finally these data permit a more definite localization of the primary and/or secondary binding sites of proteins L₂, L₃, L₄, L₁₄, L₁₇, L₂₀, L₂₁ and L₂₂ on 23 S RNA.     

Functionalization of polyoxomolybdates: the example of nitrosyl derivatives

Nitrosyl derivatives of polyoxomolybdates have been synthesized and characterized by X-ray diffraction. Most of them contain the Mo^II(NO)³⁺ unit and their structures are related to the following structural types: Lindqvist, Keggin and decatungstate [W₁₀O₃₂]^4–. Reductive nitrosylation of (NBu₄)₄[-Mo₈O₂₆] by hydroxylamine in methanol yields (NBu₄)₂[Mo₅O₁₃(OMe)₄(NO){Na(MeOH)}]. 3MeOH, which is a versatile reagent yielding a variety of derivatives (i) by the transformation of [Mo₅O₁₃(OMe)₄(NO)]^3– into [Mo₆O₁₈(NO)]^3– in acetonitrile, (ii) by the formation of [PMo₁₂O₃₉(NO)]^4– by reaction of [Mo₅O₁₃(OMe)₄(NO)]^3– with [PMO₁₂O₄₀]^3– in basic condition and (iii) by the formation of mixed valence Mo^VI/Mo^V/Mo^II decamolybdates [Mo₁₀O₂₄(OMe)₇(NO)]^2–, [Mo₁₀O₂₅(OMe)₆(NO)]^– and [Mo₁₀O₂₀(OMe)₉(NO)₃]^2– by chemical reduction of [Mo₅O₁₃(OMe)₄(NO)]^3–; Mo^II is localized while Mo^V are delocalized in the first two species but localized in the third. The unique ligating properties of [Mo₅O₁₃(OMe)₄(NO)]^3– have been documented: this species acts as a tetradentate ligand in [Ce{Mo₅O₁₃(OMe)₄(NO)}₂]^2–, a symmetrically tetraligating ligand in [Rh₂Cp*₂(-Br){-Mo₅O₁₃(OMe)₄(NO)}] and a bidentate ligand in [Mo₅O₁₃(OMe)₄(NO){RhCp*(H₂O)}]^–. Some polyoxomolybdates of the type [Mo₅(NO)₂O₁₂{RC(NH₂)NHO}₂{RC(NH)NO}₂]^2–, which contain the Mo⁰(NO) ₂ ²⁺ unit, have also been characterized.     

The endogenous gibberellins of dwarf mutants of lettuce

The gibberellin (GA) content of E-1, a tall genotype of early flowering lettuce (Lactuca sativa L.), and of three selected GA-responsive dwarfs, dwf1, dwf2, and dwf2¹, has been determined using ¹³C-labeled internal standards and gas chromatographymass spectrometry (GC-MS). In the shoots of the E-1 parent, GA₁, 3-epi-GA₁, GA₃, GA₅, GA₈, GA₁₉, GA₂₀, GA₂₉, and GA₅₃ were identified by full scan GC-MS and Kovats retention indices. Purification by immunoaffinity chromatography selective for 13-hydroxy GAs, was necessary for GA identification. Relative to the parent E-1, the concentrations of GA₁, GA₈, GA₂₀, and GA₂₉ in the shoots of dwf2 plants were reduced to about 10% and in shoots of dwf2¹ plants to less than 50%. In dwf1 the levels of GA₁, GA₈, and GA₂₉ were also reduced to less than 50% of the parent E-1, but the level of GA₂₀ was fivefold higher than in E-1. Plant height was correlated with the endogenous levels of GA₁ and GA₈.     

Organic derivatives of aluminium. Part I. Reactions of alkanolamines with aluminium isopropoxide

Reactions of alkanolamines [R₁R₂NXOH; R₁ = H, CH₃, C₂H₅; R₂ = H, CH₃, C₂H₅ and X = -CH₂CH₂-, -CH₂CH₂CH₂-, -CH₂CHCH₃, -C₆H₄CH₂CH₂-] with aluminium isopropoxide in different molar ratios (1 to 3) yield compounds of the type Al(OPrⁱ)_3?n(OXNR₁R₂)_n, where ‘n’ can be 1, 2 and 3. Most of the derivatives are distillable liquids, soluble in common organic solvents and susceptible to hydrolysis even by atmospheric moisture. The new derivatives are characterized by elemental analysis, IR and ¹H NMR spectra. Molecular weight measurements of Al(OPrⁱ)_3?n(OXNR₁R₂)_n reveal them to be tetrameric in nature.     

Effect of UV irradiation on different types of luminescence of SrAl2O4:Eu,Dy phosphors

This paper reports the luminescence behavior of Sr_0.097Al₂O₄:Eu_0.01,Dy_0.02 phosphors under UV‐irradiation. The effect of UV‐irradiation on afterglow (AG), thermoluminescence (TL) and mechanoluminescence (ML) of Sr_0.097Al₂O₄:Eu_0.01,Dy_0.02 phosphors is investigated. The space group of Sr_0.097Al₂O₄:Eu_0.01,Dy_0.02 phosphors is monoclinic P2₁. The prepared phosphors exhibit a long AG, intense TL and ML. It is found that the AG, ML intensity and TL increase with increasing duration of irradiation time. The ML intensity decreases with successive impact of the load onto the phosphors, whereby the diminished ML intensity can be recovered by UV‐irradiation. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation of benzophenone imine complexes of transition metals

Benzophenone imine [M(η¹-NHCPh₂)(CO)_nP_5-n]BPh₄ [M = Mn, Re; n = 2, 3; P = P(OEt)₃, PPh(OEt)₂, PPh₂OEt, PPh₃] complexes were prepared by allowing triflate M(κ¹-OTf)(CO)_nP_5-n compounds to react with an excess of the imine. Hydride-imine [MH(η¹-NHCPh₂)P₄]BPh₄ (M = Ru, Os), triflate-imine [Os(κ¹-OTf)(η¹-NHCPh₂)P₄]BPh₄ and bis(imine) [Ru(η¹-NHCPh₂)₂P₄](BPh₄)₂ [P = P(OEt)₃] derivatives were also prepared. The complexes were characterized spectroscopically (IR, ¹H, ³¹P, ¹³C NMR) and a geometry in solution was also established. Hydride-benzophenone imine [IrHCl(η¹-NHCPh₂)L(PPh₃)₂]BPh₄and [IrHCl(η¹-NHCPh₂)L(AsPh₃)₂]BPh₄ [L = P(OEt)₃ and PPh(OEt)₂] complexes were prepared by reacting hydride IrHCl₂L(PPh₃)₂ and IrHCl₂L(AsPh₃)₂ precursors with an excess of imine. Dihydride IrH₂(η¹-NHCPh₂)(PPh₃)₃ complex was also obtained and a geometry in solution was proposed.     

Localization changes of endogenous hydrogen peroxide during cell division cycle of Xanthomonas

Production and localization of endogenous hydrogen peroxide (H₂O₂) were investigated in strains of Xanthomonas by histochemical analysis under electron microscopy. Even though the levels of endogenous H₂O₂ production were different among various strains, the produced H₂O₂ was localized in the cell wall of all Xanthomonas strains tested. The impairment of the level of endogenous H₂O₂ accumulation resulted in a significantly decreased growth rate of bacteria, regardless if the difference of the H₂O₂ level is originally present between wild type strains or caused by mutation of the ahpC gene of Xanthomonas. The endogenous accumulation of H₂O₂ positively correlates with the cell division. Interestingly, the accumulated H₂O₂ was also localized in the mesosome-like structure and nucleoids during the cell division cycle. Furthermore, results revealed quantitative and dimensional changes of H₂O₂ accumulation in the two additional locations. These findings indicated that the additional locations of the accumulated H₂O₂ were closely associated with the process of cell division. Together, these results suggest that the endogenous H₂O₂ production plays an important role in cell proliferation of Xanthomonas.     

Some relationships between the biochemistry of photosynthesis and the gas exchange of leaves

A series of experiments is presented investigating short term and long term changes of the nature of the response of rate of CO₂ assimilation to intercellular p(CO₂). The relationships between CO₂ assimilation rate and biochemical components of leaf photosynthesis, such as ribulose-bisphosphate (RuP₂) carboxylase-oxygenase activity and electron transport capacity are examined and related to current theory of CO₂ assimilation in leaves of C₃ species. It was found that the response of the rate of CO₂ assimilation to irradiance, partial pressure of O₂, p(O₂), and temperature was different at low and high intercellular p(CO₂), suggesting that CO₂ assimilation rate is governed by different processes at low and high intercellular p(CO₂). In longer term changes in CO₂ assimilation rate, induced by different growth conditions, the initial slope of the response of CO₂ assimilation rate to intercellular p(CO₂) could be correlated to in vitro measurements of RuP₂ carboxylase activity. Also, CO₂ assimilation rate at high p(CO₂) could be correlated to in vitro measurements of electron transport rate. These results are consistent with the hypothesis that CO₂ assimilation rate is limited by the RuP₂ saturated rate of the RuP₂ carboxylase-oxygenase at low intercellular p(CO₂) and by the rate allowed by RuP₂ regeneration capacity at high intercellular p(CO₂).     

Self-assembly of cationic palladium complexes by redistribution of pyridine ligands

The reaction of [Pd(OAc)₂(py)₂] with [Li((OEt₂)_2.5)][B(C₆F₅)₄] was conducted with intent to generate the cationic palladium complex [Pd(OAc)(py)₃][B(C₆F₅)₄], (2, py = pyridine). A single crystal structure of this material, however, reveals a 1-D polymer structure formed by the self-assembly of alternating dicationic ([Pd(py)₄]²⁺) and neutral ([Pd(OAc)₂(py)₂]) palladium units bridged by acetato linkages to give [Pd(py)₄][Pd(OAc)₂(py)₂][B(C₆F₅)₄]₂ (3). These two palladium sites are produced by disproportionation of the pyridine ligands in [Pd(OAc)(py)₃][B(C₆F₅)₄]. Proton NMR studies confirm the existence of a solvent dependent equilibrium between [Pd(py)₄]²⁺, [Pd(OAc)₂(py)₂] and [Pd(OAc)(py)₃]⁺.