Synthetic polymers have often been employed as the backbones of artificial enzymes because such enzyme-like catalysts could possess thermal, chemical, and mechanical stability not available in the native enzyme. Usually, organic functional groups are present in amino acid side chains. They play the key role in the enzymatic activity of these artifical enzymes by acting as general acids, bases, or nucleophiles (R. B. Silverman, The Organic Chemistry of Drug Design and Drug Action, Academic Press, San Diego, 1992; P. Hodge, Chem. Soc. Rev., 1997, 26, 417). Metal ions or metal-bound hydroxide ions (or water molecules) are often more effective at catalyzing protein cleavage reactions (J. Chin, Acc. Chem. Res., 1991, 24, 145–152; J. Suh, Acc. Chem. Res., 1992, 25, 273–279).
A versatile approach to generate hybrid biomaterials, using atom-transfer radical polymerization (ATRP) from resin-immobilized peptides, has been reported by N. R. Washburn and co-workers at the National Institute of Standards and Technology, Gaithersburg, Maryland (see JACS, 2004, 126, 3472–3476). This approach successfully synthesized a specific peptide unit (GRGDS) to which a controlled molecular weight chain of poly(2-hydroxyethyl methacrylate) was attached. Before describing the polymer-supported synthetic strategy, the reason why peptide/synthetic polymer conjugates are of interest will be described. Future medical implants will probably incorporate materials that are functionalized with groups that engage in targeted recognition with specific cell receptors (see Science, 2002, 295, 1014 and J. Biomed
With the theme of “Helping Grow a Greener Environment,” those of us in the plastics industry—and APC—have a lot to brag about: Environmental Stewardship; New technologies in materials and processes...
Metal-catalyzed organic reactions development has been the fastest growing area of new organic chemistry for the past twenty-five years. The field is enormous and it is essentially impossible for any one individual to grasp or catalog. Transition metals, lanthanide metals, and main group metals all have been involved in this explosive expansion of synthetic organic chemistry. A recent two volume set of books, edited by H. Yamamoto and K. Oshima (Main Group Metals in Organic Synthesis, Wiley-VCH, 2004, 901 pp) covers all aspects of the use of main group metals.
This column illustrates the use of the polymer-supported reagent, polystyrene carbodiimide (d–PS–CDI) in the synthesis of an amide library that was constructed during a search for small molecules that selectively induce apoptosis in cancer cells. Carbodiimides are reagents that couple amines and carboxylic acids to generate amides under mild conditions (see Equation 1) with the corresponding urea as a by-product. If the carbodiimide is supported on polymer beads the resulting amide is formed in solution, while the by-product urea remains insoluble and attached to the polymer, simplifying separations. Apoptosis (programmed cell death) is a highly conserved process used by organisms to remove unwanted or damaged cells
The 2nd International Conference on “Times of Polymer” was held at the Congress Centre of the Continental Terme Hotel (Ischia, Italy) from the 20th to 23rd of June 2004. The Conference was organized by Prof. Alberto D'Amore (The Second University of Naples–SUN) and Prof. Domenico Acierno (University of Naples Federico II), as in its first edition. The Italian Associations of Materials (AIMAT) and Macromolecules (AIM), the Italian Society of Rheology and the National Institute of Materials Science and Technology (INSTM) sponsored the Conference and funding was received from INSTM and companies working within the area of research equipments (ATSFAAR; Belotti Strumenti, MP Strumenti, Perkin Elmer, Viscomate, Zwick/Roell-Italy).
Sustainability is one word—one word with many interpretations, so I will start by saying that to me, sustainability means a balance … a balance between improving the environment and society as a whole, while creating a competitive, stable economic business climate. The ability to strike a balance however is contingent on the economic component. Without economic fundamentals—an industrial base, jobs, business stability, and a long-term and competitive playing field—the model falls apart. Environmental protection and societal enhancement are not possible without a firm foundation for the economic pillar. My presentation is intended to bring us together: “You” as a supplier, and “We” as the chemical industry and one of your major customers.
Alzheimer's disease (AD) is the most common cause of dementia among the elderly, affecting 5% of Americans over age 65, and 20% over age 80. An excess of senile plaques (β-amyloid protein) and neurofibrillary tangles (tau protein), ventricular enlargement, and cortical atrophy characterizes it. Unfortunately, targeted drug delivery to the Central Nervous System (CNS), for the therapeutic advancement of neurodegenerative disorders such as Alzheimer's, is complicated by restrictive mechanisms imposed at the blood brain barrier (BBB). Opsonization by plasma proteins in the systemic circulation is an additional impediment to cerebral drug delivery. Here, we attempt to show that biodegradable polymeric nanoparticles (NPs) with appropriate surface modifications can deliver drugs of interest beyond the BBB for diagnostic and therapeutic applications, thus allowing the study of neurological disorders. Particularly, the radiolabelled Cu2+ or Fe3+ metal chelator Clioquinol (CQ), which has a high affinity for amyloid plaques with a radioisotope 125I, and encapsulated 125I-CQ within small, spherical, lipophilic drug carriers are capable of crossing the BBB. In this feature article, the biodistribution patterns of such nanoparticle drug carriers in wild type Swiss Webster mice are compared with free 125I-CQ. The physicochemical properties of the NPs at different surfactant concentrations, stabilizers, and amyloid-affinity agents could influence the transport mechanism.
I've been asked to reflect on key changes that have shaped the face of the petro chemical industry, and to “look into the crystal ball” to predict what might lie ahead and what we must do to succeed. The “crystal ball” reminds me of Yogi Berra's observation that “predictions are hard, especially about the future.” Now I know I cannot predict the future, but having spent nearly 40 years in the chemical industry, I am willing to say that this.
Diversity-oriented synthesis (DOS) is a term used by Schreiber (S. Schreiber, Science, 2000, 287, 1964) to describe the preparation of a large variety of highly functionalized molecules in a few steps, frequently involving combinatorial methods on polymer supports. Enantioselective 1,3-dipolar cycloaddition of azomethine ylides (see S. Kanemasa, Synless, 2002, 1371–1387) with electron-deficient olefins is a reaction method that produces stereochemical diversification by generating up to four tetrahedral centers on pyrolidine rings. The biological importance of pyrrolidines has stimulated the development of diasteroselective [3+2] azomethine ylide cycloadditions (J. Longmire, B. Wang, and Y. Zhang, J. Am. Chem. Soc., 2002, 124, 413400) and enantioselective variations employing chiral catalysts (K. A. Jorgensen, Angew. Chem. Int. Ed., 2002, 41, 4236). Now, Schreiber has developed the three-component, catalytic, asymmetric [3+2] cycloaddition of azomethine ylides for application in DOS employing solid phase ...
DNA binding ligands that can target a range of nucleotide sequences with high sequence specificity and affinity are essential for gene expression regulation by chemical approaches. Polyamides made from ordered sequences of N-methylpyrrole, 3-hydroxypyrrole, and N-methylimidazole amino acids can serve as molecular recognition tools that can be used in chromosome mapping (M. Gygi et. al, Nucleic Acid Res., 2002, 30, 2790), promotor scanning (J. Ehley et. al, Mol. Cell Biol., 2002, 22, 1723) and transcriptional modulation (P. Dervan et. al, Proc. Natl. Acad. Sci. U. S. A., 1998, 95, 12890; and J. Mol. Biol., 2001, 309, 615). Keywords:
The relatively recent invention of atomic force microscopy (AFM) in the early 1980s has proven to be a boon for the characterization of polymers in the plastics industry. Polymer surface morphology can be characterized at high magnification and resolution by AFM, which is an excellent complimentary technique to the electron microscopy (EM) techniques, such as scanning electron (SEM) and transmission electron microscopy (TEM). AFM has rapidly increased in applications to polymer characterization and has distinguished itself as a primary technique for such characterization. AFM has been especially effective in the characterization of all types of fabricated polymer articles, such as films, injection and blow moldings, and so on and has proven especially effective for characterizing multi-phase polymer systems. One aspect of the AFM technique, in comparison to the electron microscopies, is the ease of sample preparation. AFM requires little or no sample preparation and preserves sample structure, whereas SEM and TEM, typically, require much more sample preparation, which often destroys or modifies sample structure in the process. AFM has the attribute of directness of observation and, therefore, reveals structural features of natural surfaces or cross-sections of fabricated polymer articles, which are often difficult to observe by the electron microscopies, due to the necessity of more extensive sample preparation. The AFM technique also has the advantage of independently providing information both on the in-plane, as well as the height, features of a surface. This article describes aspects of the AFM technique relative to basic principles, sample preparation, morphology of polymers, comparison to the EM techniques and characterization of fabricated plastics. Keywords: atomic force microscopyelectron microscopypolymer morphologytopographyplastic filmblocking Notes 1. D.A. Chernov, S. Maganov, Atomic Force Microscopy, Ch. 19 in Comprehensive Desk Reference of Polymer Characterization and Analysis, R.F. Brady, Jr., Oxford University Press, Oxford, 2003. 2. S.V. Karande, L.G. Hazlitt, M.J. Castille, TAPPI Proc., Polymers, Laminations & Coatings Conf., 1993, 1, 195. 3. H. Zhou, G.L. Wilkes, Polymer, 1997, 38, 5735. 4. M.J. Abad, A. Ares, L. Barral, J. Cano, F.J. Diez, J.Lopez, C. Ramirez, J. Appl. Polym. Sci., 2002, 85, 1553. 5. C. Teichert, A. Haas, G.M. Wallner, R.W. Lang, Makromol. Symp., 2002, 181, 457. 6. J.K. Hobbs, M.J. Miles, Macromolecules, 2001, 34, 353. 7. D.A. Ivanov, B. Nysten, A.M. Jonas, Polymer, 1999, 40, 5899. 8. D.A. Ivanov, Z. Amalou, S.N. Magonov, 2001, 34, 8944. 9. H. Schonherr, R.M. Waymouth, C.W. Frank, Macromolecules, 2003, 36, 2412. 10. L. Jingxin, J.H. Horton, J. Mater. Chem., 2002, 12, 1268. 11. A. Kiriy, G. Gorodyska, S. Minko, M. Stamm, C. Tsitsilianis, Macromolecules 2003, 36, 8704.
The VI National Congress on Chemical Technology in Turkey was held in Bornova Izmir (Turkey) on the campus of Ege University in the period September 7– 10, 2004. Profs. Erden Alpay (Ege University), Mehmet Riza Altiokka (Anatolian University, Ankara), Suheyda Atalay (Ege University), Devrim Balkose (Izmir Institute of Technology), Ertugrul Barka (KMO Ege Bolge Co.), Cumhur Buyukakinci (Polinas Co.), Ahmet Cetinbudaklar (Mopak Co.), Muhsin Ciftcioglu (Izmir Institute of Technology), Timur ERK (Chemical Society of Turkey), Murat Ipekcioglu (Aromel Co.), Gungor Kavadarli (EBSO Co.), Zehra Ozcelik (Ege University), Kivanc Turkel (ALKIM Co.), and Sevgi Ulutan (Ege University) were members of the organizing committee. About 450 participants from 28 research centers of Turkey took part in this congress. There were four invited speakers from USA, Russia and Israel. About 200 sectional reports and 120 posters were included in the program of the congress. In the opening ceremony, the chairman (chairlady) of the congress, Prof. Suheida Atalay, showed the importance of the program and emphasized the role of pure and applied chemistry in the chemical technology.
Fluorine-containing polymers, because of their unique properties, including: low permittivity, low friction, thermal stability, high resistance to chemical attack (especially oxidation), hold a central position in the emerging nanotechnology. Important areas where fluorine containing polymers hold a lot of promise are: Resist technology in photo and radiation lithographies as well as insulators in an emerging “nanoelectronics.” Fluorine-containing polymers (specifically fluoropolyimide, fluoropolyamic acid, fluoroimideamide and fluoropoly acrylates) have been synthesized. The polymers are soluble in a wide range of solvents. Their Langmuir-Blodgett (LB) monolayers and their ultrathin films have been fabricated. Techniques like AFM, surface plasmon resonance (SPR), reflection absorption infrared spectroscopy (RAIR), and dielectric spectroscopy have been used to obtain the surface morphology, film thickness, orientation on the substrate, and dielectric constant. The dielectric constant of 1.5 is the lowest so far reported according to my knowledge.
It is a great pleasure for me to present a report on the 6th International Symposium “Alternative Cellulose” written by Thomas Schultze. During the symposium, important aspects of cellulose research and development were presented. Topics were novel cellulose solvents including ionic liquids, trimethylsilylcellulose as technically applicable fusible cellulose derivatives, recent developments of Lyocell technology including analytical methods, and new materials and textiles based on the Lyocell process.
Five yeas ago, I first spoke on biotechnology to a group in Boston. The main points I shared then dealt with the challenges that biotechnology faced in terms of acceptance and development. The big difference between then and now is progress—progress in acceptance, in generating solid data on the benefits of the technology, and in getting new and exciting possibilities closer to the market. I want to talk to you about how we are already delivering real value through the application of biotechnology. In the past five years we have seen significant development in biotechnology, increased biotech product offerings, and important changes in public acceptance of biotechnology and biotech products around the world.
The fifteenth annual BCC Conference on flame retardancy (FR) of polymeric materials was held on June 7–9, 2004 in Stamford, Connecticut, USA. The conference was organized by Professor Menachem Lewin of the Polymer Research Institute of the Polytechnic University, Brooklyn, NY. It was sponsored by Business Communications Co. of Norwalk, CT. The program consisted of 35 presentations presented in five sessions, namely, general mechanisms of flame retardancy, halogen and non-halogen FR additives, nano-composites, customer focus/industrial products, and testing/standards/methods. There were also several posters and some exhibits. The symposium attracted about 100 participants from 15 countries. The day before the symposium a short course was presented on flame retardancy.
The Center of Excellence in Polymer Science (CEPS) was established in the year 2002 with the massive financial support from University Grants Commission, New Delhi. The center has created new infrastructure to carry out research in the areas of Membrane Science, Drug Delivery, and Molecular Modeling. The experimental and computational facilities at CEPS were inaugurated on December 17, 2004 at 10:30 AM by lighting the lamps by Professor Alan G. MacDiarmid, James Von Ehr Distinguished Chair in Science and Technology, Professor of Chemistry and Physics, University of Texas (UTD) at Dallas and Nobel Laureate in Chemistry, year 2000. Professor Sanjeev K. Manohar, UTD and Professor Padmakar V. Kulkarni, University of Texas Southwestern Medical Center (UTSWMC), Dallas were also present.
Electrospinning has been recognized as an effective way to produce polymeric fibers from solution and molten states. However, the use of electrostatic attraction to deform or elongate a liquid or polymer is not a modern discovery. There is evidence of this technology dating back over 400 years. Modern science has, however, discovered alternative ways of utilizing and optimizing the droplets and fibers produced through electrostatic means. In this comprehensive review, the history of the development of polymeric nanofibers is discussed. Each area in the fabrication including processing, characterization methodology, simulation, and applications are discussed as they have evolved over time.
