Synthesis of bimetallic fulvalene and bis(cyclopentadienyl)methane derivatives of niobium and tantalum tetracarbonyl

Ring coupled bimetallic derivatives (μ-η^5:5-C₅H₄C₅H₄)[Nb(CO)₄]₂ and [μ-CH₂(η⁵-C₅H₄)₂][M(CO)₄]₂, where M = Nb and Ta have been prepared. The molecular structures of the latter two compounds have been determined: , triclinic, , a = 8.028(2) Å, b = 11.414(1) Å, c = 12.711(2) Å, α = 75.020(8)°, β = 80.34(2)°, γ = 79.46(2)°, V = 1097.3(4) ų, Z = 2, R(F) = 2.79%; [μ-CH₂(η⁵-C₅H₄)₂][Ta(CO)₄]₂, triclinic, , a = 7.815(3) Å, b = 10.275(4) Å, c = 13.135(4) Å, α = 104.25(3)°, β = 100.26(4)°, γ = 96.86(3)°, V = 991.2(6) ų, Z = 2, R(F) = 3.00%.     

Chemical implantation of Group 4 cations on silica via cyclopentadienyl- and N,N-dialkylcarbamato derivatives

Chemical implantation of Group 4 cations [Ti(III), Ti(IV), Zr(IV), Hf(IV)] has been carried out under mild conditions by the reaction of polycyclopentadienyl- (MCp_n; M = Ti, n = 3, 4; M = Zr, Hf, n = 4), mixed cyclopentadienyl/N,N-dialkylcarbamato (ML_x(O₂CNEt₂)_y; M = Ti, L = Cp, C₅Me₅ (Cp*), x = 2, y = 1; M = Hf, L = Cp, x = 1, y = 3), and N,N-dialkylcarbamato (M(O₂CNR₂)_n, M = Ti, n = 3, R = ⁱPr; M = Ti, Hf, n = 4, R = Et; M = Zr, n = 4, R = ⁱPr) derivatives, with the silanol groups of amorphous silica. Cyclopentadiene/pentamethylcyclopentadiene and/or carbon dioxide and the secondary amine are released in the process. The amount of implanted cations depends on the metal and on the ligands, the pentamethylcyclopentadienyl complex being less reactive than the unsubstituted congener. The starting complexes and the final products have been characterized by EPR or by ¹³C CP-MAS NMR spectroscopy.     

Synthesis of tantalum and niobium complexes that contain the diamidoamine ligand, [(3,4,5-F3C6H2NCH2CH2)2NMe], and the triamidoamine ligand, [(3,5-Cl2C6H3NCH2CH2)3N]

Several niobium and tantalum compounds were prepared that contain either the diamidoamine ligand, [(3,4,5-F₃C₆H₂NCH₂CH₂)₂NMe]²⁻ ([F₃N₂NMe]²⁻), or the triamidoamine ligand, [(3,5-Cl₂C₆H₃NCH₂CH₂)₃N]³⁻ ([Cl₂N₂NMe]³⁻). The former include [F₃N₂NMe]TaCl₃, [F₃N₂NMe]NbCl₃, [F₃N₂NMe]TaMe₃, [F₃N₂NMe]NbMe₃, [(F₃N₂NMe)TaMe₂][MeB(C₆F₅)₃], [F₃N₂NMe]Ta(CHSiMe₃)(CH₂SiMe₃), [F₃N₂NMe]Ta(CH₂-t-Bu)Cl₂, [F₃N₂NMe]Ta(CH-t-Bu)(CH₃), and [F₃N₂NMe]Ta(η²-C₂H₄)(CH₂CH₃). The latter include [Cl₂N₂NMe]TaCl₂, [Cl₂N₂NMe]TaMe₂, [Cl₂N₂NMe]Ta(η²-C₂H₄), and [Cl₂N₂NMe]Ta(η²-C₂H₂).X-ray diffraction studies were carried out on [F₃N₂NMe]Ta(CHSiMe₃)(CH₂SiMe₃), [F₃N₂NMe]Ta(η²-C₂H₄)(CH₂CH₃), and [Cl₂N₂NMe]TaMe_2..     

Effect of silica type and grafting method on the reactivity of tetraneopentylchromium(IV) towards and on silica

The grafting of tetraneopentylchromium(IV) onto the surface hydroxyls of silica has been investigated by varying both the method of deposition and the nature of the silica support. Reaction of the volatile organometallic with the silica surface in vacuo is compared with reaction in solution. A faster reaction but a lower ultimate Cr loading was obtained using the solution deposition technique. The reactions of the organometallic compound with Aerosil 200, a fumed silica often used to model catalyst supports, and Sylopol 952, a silica gel used as a carrier for chromium-based ethylene polymerization catalysts, are compared. After thermal pretreatment at 200 °C, grafting on both supports yields bis(neopentyl)chromium(IV) fragments regardless of the grafting method used, suggesting that a paired arrangement of the surface hydroxyl groups exists on both types of silicas. The higher Cr loading achieved on the silica gel is attributed to its higher surface area. Thermally-induced neopentane elimination from the grafted bis(neopentyl)chromium(IV) fragments occurs at the same rate and with the same stoichiometry for both Aerosil- and Sylopol-supported materials. Consequently, interactions of the grafted organometallic fragments with nearby siloxanes appear to be unimportant in the early stages of the transformation of bis(alkyl)chromium(IV) to the alkylidene.     

Magnetic, spectroscopic, structural and biological properties of mixed-ligand complexes of copper(II) with N,N,N,N″,N″-pentamethyldiethylenetriamine and polypyridine ligands

Two new mixed ligand complexes of copper(II) with N,N,N^′,N″,N″-pentamethyldiethylenetriamine and polypyridine ligands have been prepared and characterized by means of spectroscopic, magnetic and single-crystal X-ray diffraction methods. These two complexes are isomorph and isostructure in which the coordination polyhedron about the copper(II) ion is distorted square pyramidal. [Cu(PMDT)(bipy)]²⁺ and [Cu(PMDT)(phen)]²⁺ show an absorption wavelength maximum at 625 and 678 nm, respectively, assigned to the d-d transition. Antibacterial, antifungal and superoxide dismutase activities of these complexes have also been measured. It was observed that [Cu(PMDT)(bipy)](ClO₄)₂ was more effective against P. Pyocyanea and Klebsiella sp. than S. aureus. Similarly, Fusarium sp. was highly susceptible against [Cu(PMDT)(bipy)](ClO₄)₂ but less susceptible against [Cu(PMDT)(phen)](ClO₄)₂.     

Synthesis, spectroscopic, thermal and X-ray structure characterization of 1,3-propanediammonium tetrathiomolybdate and N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate

The title compounds 1,3-propanediammonium tetrathiomolybdate, (1,3-pnH₂)[MoS₄], 1 and, N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate, (tmenH₂)[MoS₄], 2, were prepared by reacting the ammonium salt of [MoS₄]²⁻ with the corresponding organic diamine. In 1 and 2 the organic diamines 1,3-propanediamine (1,3-pn) and N,N,N′,N′-tetramethylethylenediamine (tmen) are present in their diprotonated form. The reaction of 1 or 2 with [Ni(en)₃]Cl₂ · 2H₂O (en is ethylenediamine) results in the formation of the highly insoluble complex tris(ethylenediamine)Ni(II) tetrathiomolybdate, [Ni(en)₃][MoS₄], in quantitative yields. 1 and 2 have been characterized by chemical analysis, vibrational, UV-Vis and NMR spectroscopy, TG-DTA-MS and single crystal X-ray crystallography. Compound 1 is thermally more stable compared to 2. Both complexes decompose in a single step forming amorphous molybdenum sulfide. The structure of the title complexes can be described as consisting of tetrahedral [MoS₄]²⁻ dianions which accept a complex series of H-bonds from the organic dications. The strength and number of these hydrogen bonds affect the Mo-S bond lengths.     

The basis of graft rejection in the earthworms Lumbricus terrestris and Eisenia foetida

Body wall grafts have been exchanged between Lumbricus terrestris and Eisenia foetida unicolor, and the survival times of second-set grafts and a limited number of third-set grafts have been compared with those of first-set grafts. Survival of grafts has also been studied following implantation. The results do not support the hypothesis that second-set rejection is accelerated due to an immune response as in higher vertebrates. Evidence is presented that Eisenia are individually different and that the differential graft survival may be due to tissue incompatibility, survival times depending on the degree of difference in the environment presented by the recipient.     

Application of a Burkholderia cepacia lipase-immobilized silica monolith micro-bioreactor to continuous-flow kinetic resolution for transesterification of (R, S)-1-phenylethanol

Burkholderia cepacia lipase was immobilized in silicates forming from n-butyl-substituted precursors within a silica monolith from methyl-substituted precursors. The resultant preparation gave about 12 times higher rates of transesterification of (R, S)-1-phenylethanol with vinyl acetate and an approximately two-fold increase in the enantioselectivity toward (R)-1-phenylethanol, as compared to a non-immobilized counterpart. The highest enzymatic activity and enantioselectivity (reaching 250) were found at a low water activity of 0.11. The continuous-flow kinetic resolution of (R, S)-1-phenylethanol was successfully conducted using lipase-immobilized silica monolith micro-bioreactors with various inside diameters ranging from 0.25 to 1.6 mm. The reactor performance during continuous operation was consistent with the prediction from the batch reactor. A steady state conversion of 40% and enantiomeric excess more than 98% were maintained over a time period of 15 days.     

Mono, di and polynuclear Cu(II)-azido complexes incorporating N,N,N reduced schiff base: syntheses, structure and magnetic behavior

Three kinds of copper(II) azide complexes have been synthesised in excellent yields by reacting Cu(ClO₄)₂ · 6H₂O with N,N-bis(2-pyridylmethyl)amine (L¹); N-(2-pyridylmethyl)-N′,N′-dimethylethylenediamine (L²); and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (L³), respectively, in the presence of slight excess of sodium azide. They are the monomeric Cu(L¹)(N₃)(ClO₄) (1), the end-to-end diazido-bridged Cu₂(L²)₂(μ-1,3-N₃)₂(ClO₄)₂ (2) and the single azido-bridged (μ-1,3-) 1D chain [Cu(L³)(μ-1,3-N₃)]_n(ClO₄)_n (3). The crystal and molecular structures of these complexes have been solved. The variable temperature magnetic moments of type 2 and type 3 complexes were studied. Temperature dependent susceptibility for 2 was fitted using the Bleaney-Bowers expression which led to the parameters J = −3.43 cm⁻¹ and R = 1 × 10⁻⁵. The magnetic data for 3 were fitted to Baker’s expression for S = 1/2 and the parameters obtained were J = 1.6 cm⁻¹ and R = 3.2 × 10⁻⁴. Crystal data are as follows. Cu(L¹)(N₃)(ClO₄): Chemical formula, C₁₂H₁₃ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 8.788(12), b = 13.045(15), c = 14.213(15) Å; β = 102.960(10)°; Z = 4. Cu(L²)(μ-N₃)(ClO₄): Chemical formula, C₁₀H₁₇ClN₆O₄Cu: crystal system, monoclinic; space group, P2₁/c; a = 10.790(12), b = 8.568(9), c = 16.651(17) Å; β = 102.360(10)°; Z = 4. [Cu(L³)(μ-N₃)](ClO₄): Chemical formula, C₁₂H₂₁ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 12.331(14), b = 7.804(9), c = 18.64(2) Å; β = 103.405(10)°; Z = 4.     

Synthesis, structure and catalytic activity of low-spin dicyano iron(III) complexes of N,N-bis(quinolyl)malonamide derivatives

Two low-spin Fe(III) dicyano-dicarboxamido complexes have been prepared from N,N^′-bis(8-quinolyl)malonamide derivatives. Crystal structures show that the four nitrogen donors available to complex the metal are arranged in the equatorial plane with the two cyanides trans to each other in the axial positions when the malonyl moiety is disubstituted. In contrast, the unsubstituted malonyl results in only three nitrogens in the equatorial plane with the fourth in an apical position and the two cyanides occupying cis sites, one equatorial and the other axial. NMR analyses show that the solid state structure of both complexes is retained in solution. Both types of configurational complexes catalyze cyclic olefin oxidations with H₂O₂ but only the cis-dicyano complex catalyzes stilbene oxidation with formation of epoxides, diols and benzaldehyde.     

Dianthramides A and B,two N-benzoylanthranilic acid derivatives from elicited tissues of Dianthus caryophyllus

Two new phenolic derivatives, dianthramide A and B, were isolated from Dianthus caryophyllus tissues elicited with mycelial extracts of Phytophthora parasitica. The purified substances were identified on the basis of their spectral data and were characterized as N-salicyl-4-methoxyanthranilic acid (dianthramide A) and N-salicyl-4-hydroxyanthranilic acid methyl ester (dianthramide B). Dianthramides A and B co-occur in carnation tissues with the known phytoalexin dianthalexin.     

Synthesis, characterization and redox behaviour of benzoyldiazenido- and oxorhenium complexes bearing N,N- and S,S-type ligands

The reactions of [ReCl₂{η²-N₂C(O)Ph}(PPh₃)₂] (1) with 2-aminopyrimidine (H₂Npyrm), 2,2′-bipyridine (bpy) and tetraethylthiuram disulfide (tds), in MeOH upon reflux, lead to the new η¹-(benzoyldiazenido)rhenium(III) complexes [ReCl{η¹-N₂C(O)Ph}(HNpyrm)(PPh₃)₂] (2) and [ReCl₂{η¹-N₂C(O)Ph}(bpy)(PPh₃)] (3), and the known oxo(diethyldithiocarbamato)dirhenium(v) complex [Re₂O₂(μ-O){Et₂NC(S)S}₄] (4), respectively. The Et₂NC(S)S ligands in 4 result from S-S bond rupture of tds molecules. The obtained compounds have been characterized by IR, ¹H, ³¹P{¹H} and ¹³C{¹H} NMR spectroscopies, FAB⁺-MS, elemental and single-crystal X-ray diffraction (for 2 and 4) analyses. Complex 2 represents the first structurally characterized Re compound derived from 2-aminopyrimidine. Besides, the redox behaviour of 2-4 in CH₂Cl₂ solution has been studied by cyclic voltammetry, and the Lever electrochemical ligand parameter (E_L) has been estimated, for the first time, for HNpyrm. The electrochemical results are discussed in terms of electronic properties of the Re centres and the ligands.     

Synthesis and structure of dichloropalladium(II) complexes of heteroleptic N,S- and N,Se-donor ligands based on the 2-organochalcogenomethylpyridine motif, and Mizoroki-Heck catalysis mediated by complexes of N,S-donor ligands

Ligands containing the 2-organochalcogenomethylpyridine motif with substituents in the 4- or 6-position of the pyridyl ring, R⁴,R⁶-pyCH₂ER¹ [R⁴ = R⁶ = H, ER¹ = SMe (1), SeMe (2), SPh (6), SePh (7); R⁴ = Me, R⁶ = H, ER¹ = SMe (3), SPh (8), SePh (9); R⁴ = H, R⁶ = Me, ER¹ = SMe (4), SPh (10), SePh (11); R⁴ = H, R⁶ = Ph, ER¹ = SMe (5), SPh (12), SePh (13)] are obtained on the reaction of R⁴,R⁶-pyMe with LiBuⁿ followed by R¹EER¹. On reaction with PdCl₂(NCMe)₂, the ligands with a 6-phenyl substituent form cyclopalladated species PdCl{6-(o-C₆H₄)pyCH₂ER¹-C,N,E} (5a, 12a, 13a) with the structure of 13a (ER¹ = SePh) confirmed by X-ray crystallography; other ligands form complexes of stoichiometry PdCl₂(R⁴,R⁶-pyCH₂ER¹). Complexes with R⁶ = H are monomeric with N,E-bidentate configurations, confirmed by structural analysis for 3a (R⁴ = Me, ER¹ = SMe), 7a (R⁴ = H, ER¹ = SePh) and 9a (R⁴ = Me, ER¹ = SePh). Two of the 6-methyl substituted complexes examined by X-ray crystallography are oligomeric with trans-PdCl₂(N,E) motifs and bridging ligands, trimeric [PdCl₂(μ-6-MepyCH₂SPh-N,S)]₃ (10a) and dimeric [PdCl₂(μ-6-MepyCH₂SePh-N,Se)]₂ (11a). This behaviour is attributed to avoidance of the Me···Cl interaction that would occur in the cis-bidentate configuration if the pyridyl plane had the same orientation with respect to the coordination plane as observed for 3a, 7a and 9a [dihedral angles 8.0(2)-16.8(2)°]. When examined as precatalysts for the Mizoroki-Heck reaction of n-butyl acrylate with aryl halides in N,N-dimethylacetamide at 120 °C, the complexes exhibit the anticipated trends in yield (ArI > ArBr > ArCl, higher yield for electron withdrawing substituents in 4-RC₆H₄Br and 4-RC₆H₄Cl). The most active precatalysts are PdCl₂(R⁴-pyCH₂SMe-N,S) (R = H (1a), Me (3a)); complexes of the selenium containing ligands exhibit very low activity. For closely related ligands, the changes SMe to SPh, 6-H to 6-Me, and 6-H to 6-Ph lead to lower activity, consistent with involvement of both the pyridyl and chalcogen donors in reactions involving aryl bromides. The precatalyst PdCl₂(pyCH₂SMe-N,S) (1a) exhibits higher activity for the reaction of aryl chlorides in Buⁿ₄NCl at 120 °C as a solvent under non-aqueous ionic liquid (NAIL) conditions.     

Preparation and characterization of manganese(III) halide derivatives of N,N′-bis(aminobenzylidene)-1,2-ethanediamine

The preparation and characterization of manganese(III) complexes containing the quadridenate ligand, N,N′-bis(aminobenzylidene)-1,2-ethanediamine (H₂amben), and its previously unreported analogue, N,N′-bis(2-amino-5-nitro-benzylidene)-1,2-ethanediamine (H₂nitroamben), are described. The new manganese(III) halide/pseudohalide complexes, Mn(amben)X · nH₂O and Mn(nitroamben)X · nH₂O (X = Cl, Br, I, NCS; n =  0.5 or 1), were isolated as red-brown, microcrystalline solids, which were characterized fully.     

Effect of detergent concentration on the thermal stability of a membrane protein: The case study of bacterial reaction center solubilized by N,N-dimethyldodecylamine-N-oxide

We report on the response of reaction center (RC) from Rhodobacter sphaeroides (an archetype of membrane proteins) to the exposure at high temperature. The RCs have been solubilized in aqueous solution of the detergent N,N-dimethyldodecylamine-N-oxide (LDAO). Changes in the protein conformation have been probed by monitoring the variation in the absorbance of the bacteriochlorine cofactors and modification in the efficiency of energy transfer from tryptophans to cofactors and among the cofactors (through fluorescence measurements). The RC aggregation taking place at high temperature has been investigated by means of dynamic light scattering. Two experimental protocols have been used: (i) isothermal kinetics, in which the time evolution of RC after a sudden increase of the temperature is probed, and (ii) T-scans, in which the RCs are heated at constant rate. The analysis of the results coming from both the experiments indicates that the minimal kinetic scheme requires an equilibrium step and an irreversible process. The irreversible step is characterized by a activation energy of 205 ± 14 kJ/mol and is independent from the detergent concentration. Since the temperature dependence of the aggregation rate was found to obey to the same law, the aggregation process is unfolding-limited. On the other hand, the equilibrium process between the native and a partially unfolded conformations was found to be strongly dependent on the detergent concentration. Increasing the LDAO content from 0.025 to 0.5 wt.% decreases the melting temperature from 49 to 42 °C. This corresponds to a sizeable (22 kJ/mol at 25 °C) destabilization of the native conformation induced by the detergent. The nature of the aggregates formed by the denatured RCs depends on the temperature. For temperature below 60 °C compact aggregates are formed while at 60 °C the clusters are less dense with a scaling relation between mass and size close to that expected for diffusion-limited aggregation. The aggregate final sizes formed at different temperatures indicate the presence of an even number of proteins suggesting that these clusters are formed by aggregation of dimers.     

N,N′-Ethylenediaminobis(benzylphosphonic acids) as a potent class of chelators for metal ions

Aminophosphonates were found to be effective metal ion chelators. Ethylenediamine (EN) itself binds strongly to a series of metal ions forming efficient five-membered chelate ring using two nitrogen donors. Combination of EN with phosphonate function results in the family of low molecular chelating agents. Introduction of a pyridine moiety into EN-phosphonate structure results in the very effective ligands involving a four-nitrogen donor set to coordinate the metal ion. In this work, the potentiometric and spectroscopic data for two analogues 2,2′-(ethylenedi-imino)bis(3-pyridylphosphonic-acid) - L² and 2,2′-(ethylenedi-imino)bis(2-pyridyl-phosphonic-acid) - L³, comprising EN, two phosphonates and two pyridines with Cu(II), Ni(II) and Zn(II) ions are presented showing very high efficacy of one of the ligands studied.     

Cytokinin activity of N-phenyl-N′-(4-pyridyl)urea derivatives

We have synthesized 35 N-phenyl-N′-(4-pyridyl)urea derivatives and tested their cytokinin activity in the tobacco callus bioassay. Among them, N-phenyl-N′- (2-chloro-4-pyridyl)urea is highly active, the optimum concentration of which is lower than 4 × 10^?9 M (0.001 ppm), 3 compounds, i.e. N-(2-methylphenyl)-N′-(2-chloro-4-pyridyl)urea, N-(3-methylphenyl)-N′-(2-chloro-4-pyridyl)urea and N-(3-chlorophenyl)-N′-(2-chloro-4-pyridyl) urea are as active as N⁶-benzyladenine (concentration for optimum yield: 4.4 × 10^?8 M or 0.01 ppm), and N-phenyl-N′-(2-methyl-4-pyridyl)urea and N-(2-chlorophenyl)-N′-(2-chloro-4-pyridyl)urea are as active as N-phenyl-N′-(4-pyridyl)urea (concentration for optimum yield: 4.7 × 10^?7 M or 0.1 ppm), while the activity of the other 29 compounds are not so remarkable and 11 of them are almost or completely inactive.     

A structural study of the hydrated and the dimethylsulfoxide, N,N′-dimethylpropyleneurea, and N,N-dimethylthioformamide solvated iron(II) and iron(III) ions in solution and solid state

The structures of the solvated iron(II) and iron(III) ions have been studied in solution and solid state by extended X-ray absorption fine structure (EXAFS) in three oxygen donor solvents, water, dimethylsulfoxide (Me₂SO), N,N′-dimethylpropyleneurea (DMPU), and one sulfur donor solvent, N,N-dimethylthioformamide (DMTF); these solvents have different coordination and solvation properties. In addition, the structure of hexakis(dimethylsulfoxide)iron(III) perchlorate has been determined crystallographically to support the determination of the corresponding solvate in solution. The hydrated, the dimethylsulfoxide and N,N-dimethylthioformamide solvated iron(II) ions show regular octahedral coordination in both solution and solid state with mean Fe-O, Fe-O, and Fe-S bond distances of 2.10, 2.10, and 2.52 Å, respectively, whereas the N,N′-dimethylpropyleneurea iron(II) solvate is five-coordinated, d(Fe-O) = 2.06 Å. The compounds vary in color from light green (hydrate) to dark orange or red (DMPU). The hydrated iron(III) ion in aqueous solution and the dimethylsulfoxide solvated iron(III) ions in solution and solid state show the expected octahedral coordination, the Fe-O bond distances are 2.00 Å for both, whereas the N,N′-dimethylpropyleneurea iron(III) solvate is found to be five-coordinated with a mean Fe-O bond distance of 1.99 Å. The N,N-dimethylthioformamide solvated iron(III) ion in the solid perchlorate salt is tetrahedrally four-coordinated, the mean Fe-S bond distance is 2.20 Å. Iron(III) is reduced with time to iron(II) in N,N-dimethylthioformamide solution. The compounds vary in color from pale yellow (hydrate) to blackish red (DMPU).     

Rice straw, the role of silica and treatments to improve quality

Rice straw is unique relative to other cereal straws in being low in lignin and high in silica. Unlike other cereal straws taller varieties of rice straws tend to be leafy while the leaves are less digested than stems. This may contribute to higher straw value with rice yield. There is genetic variation in straw quality but has not been exploited and tends to be smaller than environmental variation. Effort in plant breeding has been to develop short varieties with higher grain yield. This development has reduced straw quantity but not nutritive value. The relationship between plant genetics and silica metabolism is virtually uninvestigated, although reviews from plant physiology indicate it is a major factor.

Silica and lignin in that order are the primary limiting factors in rice straw quality. Silicon is a nutrient element which has been overlooked largely because of its assumed inertness, but also because of its geochemical abundance that so greatly exceeds its metabolic use by plants and animals. Silicon is involved in several major roles in rice: carbohydrate synthesis, grain yield, phenolic synthesis and plant cell wall protection. These vectors interact with each other to eliminate statistical association of silica and lignin with straw digestibility when varieties are compared. Yield of grain is highly related to silica content of straw, which reflects soil availability. There are no detailed studies on rice straw lignin. Most papers reporting lignin contents in rice straw have used acid-detergent lignin by either the sulfuric acid or permanganate versions. There are undoubtedly soluble phenolics in rice straw that need investigation. The effects of ammonia and urea on silica is to crack the silicified cuticular layer. Silica is not dissolved by these reagents in contrast to the action of sodium hydroxide.

Treatments on rice straw follow those applied to other lignified materials. In order of frequency of reports, urea followed by ammonia with comparatively fewer papers on sodium hydroxide, steam and pressure treatments or exploded by pressure release, and only one or two papers on acid treatments and white rot fungi. There are reports on animal supplementation and a few growth studies with young animals. Field surveys in India and the southeast Asian countries only report the use of urea, although it appears less efficient than ammonia. Farmer acceptance is related to their perceptions on costs, labor, equipment, health, safety, i.e. the exposure to ammonia vapor, economic and other social factors. The various papers reporting treatments have used animal digestion trials; a variety of in sacco, in vitro digestions with rumen organisms or cellulase, some in combination with pepsin digestion or neutral-detergent extraction. Gas production from in vitro rumen fermentation has also been used. Results are expressed mainly on dry matter basis and fewer reports on organic matter. Results are difficult to compare and standardization of procedures is badly needed. However, most treatments with ammonia and urea show some increase in digestibility and intake where measured in in vivo trials. In vitro and in sacco evaluations tend to overestimate improvement in digestibility.     

Indolethylamine N-methyltransferases of Phalaris tuberosa, purification and properties

Two S-adenosylmethionine-dependent indolethylamine N-methyltransferase activities were purified from soluble extracts of Phalaris tuberosa by fractionation with (NH₄)₂SO₄, and chromatography on DEAE-Sephadex. One enzyme methylated the primary indolethylamines and the other methylated the secondary indolethylamines in the plant. These two enzymes were similar in catalytic and bulk physical properties and could not be separated during purification or by A 1.5 Agarose or hydroxylapatite chromatography. The products of enzymic reactions were identified by TLC.