Coordination environment friendly silicon in copper(I) chloride π-complexes with tetravinylsilane and dimethyltetravinyldisiloxane

Two crystal complexes of copper(I) chloride with tetravinylsilane (TVS) dimethyltetravinyldisiloxane (DMTVDS) were prepared and examined by IR spectroscopy and X-ray diffraction: sp. gr. P2/a, Z = 4, a = 13.428(1) Å, b = 7.9584(7) Å, c = 14.694(1) Å for [Cu₄Cl₄(TVS)]; sp. gr. P2₁/c, a = 10.505(1) Å, b = 13.487(1) Å, c = 13.870(1) Å for [Cu₄Cl₄(DMTVDS)]. The influence of the vinylsilicon ligands on the efficiency of the Cu?CC interaction is discussed. Thus, the consideration of d_Si ← π∗_CC ← d_Cu conjugate system may help to understand how the silicon π-acceptor properties influence on the degree of trigonal distortion of the Cu(I) coordination tetrahedron as well as on the inorganic part organization. The present studies are aimed at the use of the structure controlled nanoparticles supported on vinyl modified silicon (or silicone) substrate.     

On the Beneficial Role of Silicon to Organisms: A Case Study on the Importance of Silicon Chemistry to Metal Accumulation in Yeast

Silicon is involved in numerous important structural and functional roles in a wide range of organisms, including diatoms, plants, and humans, but clear mechanisms have been discovered only in diatoms and sponges. Silicate availability influences metal concentrations within various cell- and tissue-types, but a mechanism has not been discovered so far. In an earlier study on Baker’s yeast Saccharomyces cerevisiae it was proposed that a chemical mechanism, rather than a biological one, is important. In the present study, the interaction of silicon with Baker’s yeast is further investigated by studying the influence of zinc and magnesium on Si accumulation both at a low and a high silicate concentration in the medium. Si accumulation fitted well with Freundlich adsorption and Si release followed depolymerization kinetics, indicating that silicate adsorbs to the surface of the cell rather than being transported over the cell membrane. Subsequently, adsorbed silicate interacts with metal ions and, therefore, alters the cell’s affinity for these ions. Since several metals are nutritional, these Si interactions can significantly change the growth and viability of organisms. In conclusion, the results show that chemistry is important in Si and metal accumulation in Baker’s yeast, and suggest that similar mechanisms should be studied in detail in other organisms to unravel essential roles of Si.     

Odorant design based on the carbon/silicon switch strategy

Silicon chemistry has been demonstrated to be a novel source of chemical diversity in odorant design. The carbon/silicon switch strategy, i.e., sila-replacement in known odorants, is one of the methods currently used for the development of silicon-based odorants. Examples resulting from this strategy are sila-coranol, sila-dimetol, sila-linalool, sila-muguetalcohol, sila-majantol, sila-hydratropyl acetate, sila-bourgeonal, sila-lilial, disila-versalide, and disila-okoumal.     

Intramolecular interligand charge transfer and a red hexacoordinate Si-complex with salen-type ligand vs. colorless tetracoordinate salen-Si-complexes with similar substituents

The reactions between the tetradentate ligand o-HO-p-OMe-C₆H₃-C(Ph)N-(CH₂)₂-NC(Ph)-C₆H₃-o-OH-p-OMe (1) and the dichlorosilacycles [PhN-(CH₂)₂-NPh]SiCl₂ (2) and [Me₃SiN-(o-C₆H₄)-NSiMe₃]SiCl₂ (4) afforded the red colored complexes [o-O-p-OMe-C₆H₃-C(Ph)N-(CH₂)₂-NC(Ph)-C₆H₃-o-O-p-OMe]Si{2N}, {2N} = [PhN-(CH₂)₂-NPh] (3), {2N} = [Me₃SiN-(o-C₆H₄)-NSiMe₃] (5) with hexacoordinate central silicon atom, respectively. The intense red color of these compounds originates from interligand charge transfer [(amide) → Si → (salen)]. Compound 3a, a cyclic dimer of 3 with tetracoordinate Si atoms, was isolated from the reaction mixture. It is colorless, thus demonstrating that the interligand charge transfer from the amide ligand to the salen-type ligand requires the connection of the imine N atoms to the Si atom and is not possible via an Si-O-connection to the salen-type ligand only. The reaction between ligand 1 and the dichlorosilacycle 7 [Ph₂MeSiN-(CH₂)₂-NSiMePh₂]SiCl₂ with bulky substituents at the amide N atoms gave rise to the monomeric salen-Si-compound 8 [o-O-p-OMe-C₆H₃-C(Ph)N-(CH₂)₂-NC(Ph)-C₆H₃-o-O-p-OMe]Si[Ph₂MeSiN-(CH₂)₂-NSiMePh₂] bearing only tetracoordinate Si atoms. Compound 8 is also colorless. The formation of 8 from 1 and 7 was proven to occur via a hexacoordinate silicon complex 8a, which, however, could not be isolated so far.     

硅提高植物抗旱性的生理机制研究进展

干旱作为限制作物产量和品质的主要非生物胁迫之一,对全球社会、经济和生态造成巨大损失。在全球气候变化背景下,提高植物抗旱性的重要性日益突显。硅能够提高植物的抗旱性：外源硅的施用可以影响气孔导度,改变蒸腾速率,改善植物水分状况;通过调节气孔动力学、合成光合色素,促进光化学反应,从而改善光合作用;此外硅可通过渗透调节以平衡植物对矿质元素的吸收,以及调节抗氧化防御系统,减轻植物在干旱胁迫中的氧化损伤。总结了硅对干旱胁迫下植物水分利用、光合作用、矿质元素吸收、抗氧化系统、植物激素代谢等方面的作用及相关生理机制。建议未来从复合逆境胁迫、低硅积累植物等方面进一步揭示硅提高植物抗旱性的作用机制,从而为农林生态系统合理利用硅素来提高生产效率提供科学依据和理论基础。     

Long-term biocompatibility of NanoGATE drug delivery implant

The fouling of components and the formation of a fibrotic tissue capsule around subcutaneously implanted medical devices are two major obstacles in developing viable, long-term implantable drug delivery systems. NanoGATE is a subcutaneous implant designed for constant-output passive diffusion of a drug of interest through a silicon nanopore membrane. To this end, we have investigated the long-term in vivo biocompatibility of the NanoGATE implant in terms of the fouling of the nanopore membrane and the formation of a fibrotic tissue capsule around the implant. We have also evaluated how these effects influence diffusion of a lysozyme surrogate from the device once implanted within the vascular compartment of a Sprague-Dawley rat model. Using several model biomolecules such as glucose, lysozyme, and albumin, our studies suggest that silicon nanopore membranes do not foul when implanted subcutaneously for 6 mo. This study also reveals the tissue capsule that naturally forms around the implant does not limit diffusion of molecules with molecular weights on the order of 14.4 kDa at therapeutic delivery rates of tens of micrograms per day. This indicates that our NanoGATE implant should be completely functional in vivo, providing constant release levels of a drug over an extended time period. Thus, by adjusting the release rate to fit the pharmacokinetic clearance profile of the Sprague-Dawley rat, long-term steady-state blood plasma concentrations can be achieved.     

硅对低温胁迫后檀香紫檀苗木生长和光合生理的影响

为探究硅(Si)对檀香紫檀(Pterocarpus santalinus)抗寒性的影响,对1年生苗木施Si后经(–3±0.5)℃胁迫24 h恢复栽培90 d的生长、叶片光合参数和4种碳同化关键酶活性进行了研究。结果表明,施Si的檀香紫檀苗木发育健壮,抗寒性提高,显著促进低温胁迫后的生长恢复;施Si显著抑制低温胁迫导致的檀香紫檀苗木叶绿素含量降低和叶绿素a/b减小,促进表观光合电子传递速率(ETR)、实际光量子效率Y(Ⅱ)和PSⅡ调节性能量耗散Y(NPQ),降低PSII非调节性能量耗散Y(NO)和非光化学荧光淬灭(NPQ);施Si提高受低温胁迫檀香紫檀苗木的光合速率(Pn)、气孔导度(Gs)和水分利用效率(WUE);施Si的檀香紫檀苗木在低温胁迫后,核酮糖-1,5-二磷酸羧化酶(Rubisco)、果糖-1,6-二磷酸酶(FBP)、果糖-1,6-二磷酸醛缩酶(Ald)、磷酸烯醇式丙酮酸羧化酶(PEPC)活性显著提高。适量施Si有利于保持低温胁迫下苗木光合膜结构的完整性和生理功能的稳定性,是提高檀香紫檀苗木抗寒性、有效应对低温胁迫的营养管理措施。     

橡胶草异戊烯焦磷酸异构酶基因的电子克隆及分析

利用电子克隆方法获得两条橡胶草异戊烯焦磷酸异构酶基因（IDI）的eDNA序列和编码区基因组序列,分别命名为TkIDI1和TklDl2,并采用生物信息学方法对该基因及其编码蛋白进行系统进化、亚细胞定位、活性位点、高级结构等方面的预测和分析。结果显示,TklDI1的eDNA序列长度为980bp,包含一个696bp的开放读码框（ORF）,编码232个氨基酸,预测定位于内质网或叶绿体上;TkIDl2的eDNA序列长度为1038bp,包含一个843bp的ORF,编码281个氨基酸,预测定位于线粒体或叶绿体;而他们的截短转录本蛋白定位于胞质中,且都具有过氧化物酶体定位信号。结构分析表明TkIDI1和TkIDI2与植物IDI蛋白同源,活性位点保守,高级结构与其他植物的IDI均具有高度的相似性。     

Structure, morphology, and composition of silicon biocomposites in the palm tree Syagrus coronata (Mart.) Becc.

Summary.  Syagrus coronata is an economically important palm tree grown as an ornament, for the oil extracted from its seeds, and the wax from its leaves which has several applications in industry. Silicon biocomposites were analyzed in leaves of S. coronata. Silica bodies were found as extracellular silica masses between the hypodermal-layer cell walls and in granules present in the vacuoles of palisade cells. Scanning electron microscopy of the hypodermal layer of cells showed a collection of spherical bodies embedded in enveloping cavities that outlined the general structure of the bodies. Globular subunits with sharp edges formed the spherical bodies that ranged from 6 to 10 μm in diameter (average, 7.8 μm). X-ray microanalysis detected only silicon and oxygen homogeneously distributed throughout the bodies. Vacuoles of palisade cells contained a large number of granules ranging from 20 nm to 1.2 μm in size (average, 300 nm). Transmission electron microscopy associated with electron spectroscopic imaging and electron energy loss spectroscopy were used to determine the elemental composition of the granules. Vacuolar granules were amorphous and composed of silicon and oxygen, suggesting they consist of amorphous silica biominerals. No nitrogen, indicative of organic matter, was detected in the granules. Received November 26, 2001; accepted July 1, 2002; published online October 31, 2002 RID="*" ID="*" Correspondence and reprints: Departamento de Microbiologia Geral, Instituto de Microbiologia Professor Paulo de Góes, Centro de Ciências da Saude, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil.     

Dietary silicon and arginine affect mineral element composition of rat femur and vertebra

Both arginine and silicon affect collagen formation and bone mineralization. Thus, an experiment was designed to determine if dietary arginine would alter the effect of dietary silicon on bone mineralization and vice versa. Male weanling Sprague-Dawley rats were assigned to groups of 12 in a 2×2 factorially arranged experiment. Supplemented to a ground corn/casein basal diet containing 2.3 μg Si/g and adequate arginine were silicon as sodium metasilicate at 0 or 35 μg/g diet and arginine at 0 or 5 mg/g diet. The rats were fed ad libitum deionized water and their respective diets for 8 wk. Body weight, liver weight/body weight ratio, and plasma silicon were decreased, and plasma alkaline phosphatase activity was increased by silicon deprivation. Silicon deprivation also decreased femoral calcium, copper, potassium, and zinc concentrations, but increased the femoral manganese concentration. Arginine supplementation decreased femoral molybdenum concentration but increased the femoral manganese concentration. Vertebral concentrations of phosphorus, sodium, potassium, copper, manganese, and zinc were decreased by silicon deprivation. Arginine supplementation increased vertebral concentrations of sodium, potassium, manganese, zinc, and iron. The arginine effects were more marked in the silicon-deprived animals, especially in the vertebra. Germanium concentrations of the femur and vertebra were affected by an interaction between silicon and arginine; the concentrations were decreased by silicon deprivation in those animals not fed supplemental arginine. The change in germanium is consistent with a previous finding by us suggesting that this element may be physiologically important, especially as related to bone DNA concentrations. The femoral and vertebral mineral findings support the contention that silicon has a physiological role in bone formation and that arginine intake can affect that role. The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area is an equal opportunity/affirmative action employer, and all agency services are available without discrimination. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.