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Dendrimer - Wikipedia

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Green Synthesis of Metallic Nanoparticles via ..

Our results described a simple and eco-friendly time-dependent method to biosynthesize green crystalline SNPs and GNPs in metal solution using medicinal plant extracts which does not need special physical conditions. Our research explained that C. zizanioides can be an excellent bioreductant and is an easily available, less expensive plant source for the synthesis of SNPs and GNPs. The C. zizanioides aqueous leaf extract is environmentally friendly and therefore this protocol could be used for the rapid production of SNPs. The size of GSNPs and GGNPs can be easily adjusted by varying the concentration of the leaf extract. The successful synthesis of SNPs and GNPs by reducing silver and gold ions using an aqueous extract of C. zizanioides leaves showed the reduction rate of silver ions was much faster than that of the gold ions. The water soluble compounds, like alkaloids and phytosterols, present in the C. zizanioides were mostly responsible for reducing silver and gold ions to nanosized silver and gold particles. The synthesized and well-studied green nanoparticles can be used for promising potential applications, including water purification, recording media, biosensing devices, nanoelectronics, and catalysis, as reported by Shukla et al. In one of our recent publications, we tissue engineered plant extracts by electrospinning, which makes it possible to combine the advantages of using these plant extracts in the form of nanofibrous mats to serve as skin graft substitutes or as nanofibrous wound dressings for the treatment of burns and wounds. The synthesized SNPs and GNPs were well-capped and showed strong antibacterial activity (results not shown) which is very important for the aspects of its biomedical applications, such as a hydrogel dressing without any preservatives, which would be most efficient for cuts, new burns, and dry wounds. Other major applications that could be worthwhile are drug delivery, gene delivery, and biosensor applications where there is a direct contact of these nanoparticles with blood. This eco-friendly method for SNP and GNP biosynthesis does not use any chemicals and thus has the potential to be exploited in biomedical applications and will play an important role in future optoelectronic and biomedical applications. In our recent studies, we have conferred the ability of the silver nano particles for preventing biofilm in urinary catheters.

The name comes from the Greek word δένδρον (dendron) which translates to "tree"

The present essay offers an overview of the latest developments in the chemistry of organoboron compounds. The unique structural characteristics and the versatile reactivity profile of organoboron compounds continue to expand their roles in several areas of chemistry. A growing number of boron-mediated reactions have become vital tools for synthetic chemistry, particularly in asymmetric synthesis, metal-catalyzed processes, acid catalysis, and multicomponent reactions. As a result, boronic acids and related molecules have now evolved as major players in synthetic and medicinal chemistry. Moreover, their remnant electrophilic reactivity, even under physiological conditions, has allowed their incorporation in a growing number of bioactive molecules, including bortezomib, a clinically approved anticancer agent. Finally, the sensitive and selective binding of boronic acids to diols and carbohydrates has led to the development of a growing number of novel chemosensors for the detection, quantification, and imaging of glucose and other carbohydrates. There is no doubt that the chemistry of organoboron compounds will continue to expand into new discoveries and new applications in several fields of science.

Strategies for Preparing Albumin-based Nanoparticles …

Recent Advances in the Synthesis and Application of Layered Double Hydroxide (LDH) Nanosheets

and for the first time, Cu catalyst concentrations of 100 ppm and lower were used in aqueous media to prepare well-defined macromolecules. The on homopolymerization of One challenge associated with copper based ATRP in water is the dissociation of deactivator complexes to give bromide ions and Cu(II)/L complexes that cannot deactivate the growing radicals. Adding a large excess of a salt with a halide anion (e.g. tetraethylammonium bromide, TEABr) shifts the equilibrium back towards the deactivator complex. The results should be independent of the cation used. This implies that cations such as sodium or potassium could be used, or even polymerizable cations such as those from quarentized tris(pyridin-2-ylmethyl)amine (TPMA) ligand gave stable CuI complexes in water, without any significant disproportionation, and polymers of oligo(ethylene oxide) acrylate were synthesized with low dispersity (Mw/Mn=1.15–1.28) using 20-100 ppm of an active CuBr/TPMA based catalyst in the presence of excess bromide anions. , Cu catalyst concentrations from 20 to 100 ppm chains grow uniformly. When 5 ppm catalyst was used, the molecular weights were higher than in the other polymerizations, indicating a loss of control at approximately 5 ppm due to a lower concentration of deactivator, and longer transient radical lifetimes. (25-26) In this case, a BSA protein with ca. 30 cleavable initiating sites was used as a macroinitiator. The polymer molecular weights, determined, after cleavage from protein, resulting in a final values of Mn (22) the method presented here uses ca. 500 times lower catalyst concentrations, facilitating purification of the PPH.

polymers), and incorporation of polar monomers into various polyolefin classes. For example, if acrylates, vinyl esters, acrylonitrile, and the like could be incorporated into the present low-pressure polyolefin synthesis, the result would be a new family of olefin-based polymers that are likely to have major commercial significance. Of course, improvements in the present catalytic systems will have a pronounced effect on the polyolefins that are commercially available. Improvements in molecular weight distribution control (e.g., narrow molecular weight distribution), the ability to synthesize EPRs in gas-phase reactors, and the control of catalyst decay (e.g., improved efficiency) are advances that will surely occur.

Chemistry - A European Journal - Early View - Wiley …

Regional Centre of Advanced Technologies and Materials

The bulk of polyamides are the co-polymeric proteins. A small group of polyamides are referred to as poly amino acids in order to distinguish them from the proteins due to different features of its biosynthesis. 1, 2 There are some major differences between them: (a) Poly-amino acids are composed of monomeric units of amino acids, at least in the backbone as compared to proteins which are composed by hetero – oligomeric units of amino acids, (b) Proteins are biosynthesized from DNA, through transcription and ribosomal mediated translation mechanism whereas the biosynthesis of poly-amino acids are independent of transcription and translation machinery. Henceforth, the translational inhibitors, such as Chloramphenicol does not affect the biosynthesis of poly amino acids and some specific enzymes regulates and catalyses the biosynthesis of poly amino acid. (c) DNA being the genomic blueprint, determines the length of specific gene sequences which yields specific protein molecules of spatially spaced configured and conformed stable molecules having definite molecular weight whereas poly amino acids shows notable variation in the molecular weight. (d) Amide linkages in proteins are only formed between α-amino and α-carboxylic groups (α-amide linkages), whereas amide bonds in poly amino acids involve other side chain functions (i.e., β -and g carboxylic and α-amino groups). (e) PGA can be stained with dyes like Methylene blue whereas proteins can be stained with Coomassie blue. 1, 2, 32

ZSM-5 is a molecular sieve, which is to say that its three-dimensional crystal structure has an open, lacy quality to it—more hole than crystal. These pores are approximately 5 angstroms (about one-hundred billionth of an inch) in diameter, big enough to accommodate a methanol molecule. ZSM-5 catalytically breaks down the methanol molecule, whose chemical formula is CH3OH, to create a molecule of water and a hydrocarbon fragment (CH2). These fragments assemble themselves into hydrocarbon molecules—the stuff that gasoline is made of. (Gasoline is actually a rich stew of assorted hydrocarbon molecules, ranging from 6 to 12 carbon atoms per molecule.) All zeolites are molecular sieves, and many of them also catalyze this reaction, but the other zeolites keep adding the hydrocarbon fragments on to the gasoline-sized molecules, turning them into heavier and heavier liquids, and eventually into a solid. The pores in ZSM-5, however, are just the right size to construct gasoline-sized molecules, but too small to let larger hydrocarbons form. (Some of the intermediate products formed en route to gasoline-sized hydrocarbons are important chemicals in their own right. These chemicals can be intercepted as they form, and diverted for other uses. These uses include making high-quality synthetic lubricating oils and diesel fuels.)

Practical route to high activity enzyme preparations for synthesis in organic media ..
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  • Stimulating concepts in chemistry (Book, 2000) …

    Nitrogen - Wikipedia

  • Stimulating concepts in chemistry

    937: Zhang, Y.-H.; Gao, Z.-X.; Zhong, C.-L.; Zhou, H.-B.; Chen, L.; Wu, W.-M.; Peng, X.-J.; Yao, Z.-J

  • Lewis acid catalysis in aqueous media / S ..

    - MDPI

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Concentration and pH Dependent Aggregation of …

In comparison with other porous materials, Covalent Organic Frameworks (COFs) have the advantage of low density, large surface area, tunable properties and functionality because of the versatile covalent bonds between organic building units made up of carbon, silicon, oxygen, boron and nitrogen only. The various fields of application leverage on specific characteristic properties of the framework. Gas separation and storage takes advantage of their large surface area and pore volume, they are used in optoelectronics because of the presence of out of plane π-interactions within 2D functionalized COFs, their use as heterogeneous catalysts is because they have inherent network of nanopores, energy storage devices take advantage of their large surface area while their diverse composition and synergistic function makes them invaluable in sensing devices. COFs have also found usefulness in the making of conductive membranes due to their tunable pores and exceptional stability in aqueous media. Inherent large surface area, tunable pores and adjustable functionality makes COFs very alluring candidates for drug delivery systems and separation / enrichment of small molecules.

Concentration and pH Dependent Aggregation of ..

of one of the unique properties of enzymes: they were designed by nature to function together in complex synthetic or degradative pathways. Because of this property, whole cells and microorganisms can be used as catalytic entities that carry out multiple reactions for the complete synthesis of complex chiral molecules. A patent was recently issued for a genetically engineered Escherichia coli that synthesizes the molecule D-biotin directly from glucose. Biotin has three chiral centers, and the current chemical synthesis requires 13-14 steps with low yields. Similarly, researchers are constructing a microorganism that directly catalyzes the synthesis of a vitamin C precursor from glucose. Combining genes from various organisms results in a process that uses a microbially synthesized intermediate with a final chemical conversion to vitamin C. Whole cells of microorganisms are also used in the synthesis of antibiotics from carbohydrate starting materials, and whole cells are used in the biocatalysis of certain steroids. A number of specialty chemicals with complex synthetic schemes can be produced most efficiently by intact microorganisms utilizing a series of enzyme-catalyzed reactions designed by nature to work together.

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