Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chemical Engineering”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed2004

Tissue engineering of cartilage with chondrocytes cultured in a chemically-defined, serum-free medium.

Cell culture with serum-containing medium has potential problems associated with contamination of infectious agents. This study demonstrates for the first time the feasibility of regenerating cartilage tissues in vivo by implantation of chondrocytes cultured in vitro in a chemically-defined, serum-free medium. Chondrocytes cultured in the serum-free medium grew similarly to those in a serum-containing medium. Implantation of chondrocytes cultured in the serum-free medium and seeded on to polymer scaffolds resulted in the regeneration of cartilage tissues with histological aspects similar to those of cartilage tissues regenerated from chondrocytes cultured in serum-containing medium.

Animals↗
PubMed1994

Fabrics that repel.

When exposures to hazardous chemicals cannot be eliminated through engineering changes, substitution of different materials, or implementation of alternative work practices, chemical protective clothing offers the last line of defense. No single material provides protection against all chemicals, and selection of the appropriate CPC is governed by the nature of the hazard, the chemical resistance properties of the protective material and the conditions under which the equipment will be used. Merely making protective equipment available to employees is not sufficient. The equipment must be properly selected, used and maintained. Torn suits or punctured gloves, for instance, do not provide very much protection. A good protective clothing program must also include provisions for employee training and ongoing supervision.

Chemical Industry↗
PubMed2004

Engineered biosynthesis of 16-membered macrolides that require methoxymalonyl-ACP precursors in Streptomyces fradiae.

Development of host microorganisms for heterologous expression of polyketide synthases (PKS) that possess the intrinsic capacity to overproduce polyketides with a broad spectrum of precursors supports the current demand for new tools to create novel chemical structures by combinatorial engineering of modular and other classes of PKS. Streptomyces fradiae is an ideal host for development of generic polyketide-overproducing strains because it contains three of the most common precursors--malonyl-CoA, methylmalonyl-CoA and ethylmalonyl-CoA--used by modular PKS, and is a host that is amenable to genetic manipulation. We have expanded the utility of an overproducing S. fradiae strain for engineered biosynthesis of polyketides by engineering a biosynthetic pathway for methoxymalonyl-ACP, a fourth precursor used by many 16-membered macrolide PKS. This was achieved by introducing a set of five genes, fkbG-K from Streptomyces hygroscopicus, putatively encoding the methoxymalonyl-ACP biosynthetic pathway, into the S. fradiae chromosome. Heterologous expression of the midecamycin PKS genes in this strain resulted in 1 g/l production of a midecamycin analog. These results confirm the ability to engineer unusual precursor pathways to support high levels of polyketide production, and validate the use of S. fradiae for overproduction of 16-membered macrolides derived from heterologous PKS that require a broad range of precursors.

Acyl Carrier Protein↗
PubMed2002

Ordered nanoparticle arrays formed on engineered chaperonin protein templates.

Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

Chaperonins↗
PubMed2006

Charging of tRNA with non-natural amino acids at high pressure.

We show a simple and reliable method of tRNA aminoacylation with natural, as well as non-natural, amino acids at high pressure. Such specific and noncognate tRNAs can be used as valuable substrates for protein engineering. Aminoacylation yield at high pressure depends on the chemical nature of the amino acid used and it is up to 10%. Using CoA, which carries two potentially reactive groups -SH and -OH, as a model compound we showed that at high pressure amino acid is bound preferentially to the hydroxyl group of the terminal ribose ring.

Amino Acids↗
PubMed2003

Bioelectrocatalysts: engineered oxidoreductase system for utilization of fumarate reductase in chemical synthesis, detection, and fuel cells.

Fumarate reductase was used as a model oxidoreductase to demonstrate continuous electrical cofactor reduction-oxidation during the bioelectrochemical synthesis and detection of chemicals. The enzyme preparation was immobilized onto a graphite felt electrode that was modified with carboxymethylcellulose (CMC). Nicotinamide adenine dinucleotide (NAD), neutral red, and fumarate reductase (which contained menaquinone) were covalently linked by peptide bonds to the CMC. The electron mediator neutral red allowed NAD and menaquinone to be recycled electrically during enzymatic chemical synthesis. Succinate detection by the bioelectrocatalyst was linear from 5 microM to 10 mM succinate. Fumarate synthesis using this bioelectrode was dependent on succinate utilization and resulted in proportional production of electricity and fumarate. Succinate synthesis using this bioelectrocatalyst was dependent on current and fumarate concentration. This bioelectrocatalyst system may enhance the utility of menaquinone- and/or pyridine nucleotide-linked oxidoreductases in diverse enzymatic fuel cells and sensors. It may also enhance the utility of oxidoreductase-based chemical synthesis systems because it eliminates the problem of cofactor recycling.

Actinobacillus↗
PubMed2006

Mineralization capacity of Runx2/Cbfa1-genetically engineered fibroblasts is scaffold dependent.

Development of tissue-engineered constructs for skeletal regeneration of large critical-sized defects requires the identification of a sustained mineralizing cell source and careful optimization of scaffold architecture and surface properties. We have recently reported that Runx2-genetically engineered primary dermal fibroblasts express a mineralizing phenotype in monolayer culture, highlighting their potential as an autologous osteoblastic cell source which can be easily obtained in large quantities. The objective of the present study was to evaluate the osteogenic potential of Runx2-expressing fibroblasts when cultured in vitro on three commercially available scaffolds with divergent properties: fused deposition-modeled polycaprolactone (PCL), gas-foamed polylactide-co-glycolide (PLGA), and fibrous collagen disks. We demonstrate that the mineralization capacity of Runx2-engineered fibroblasts is scaffold dependent, with collagen foams exhibiting ten-fold higher mineral volume compared to PCL and PLGA matrices. Constructs were differentially colonized by genetically modified fibroblasts, but scaffold-directed changes in DNA content did not correlate with trends in mineral deposition. Sustained expression of Runx2 upregulated osteoblastic gene expression relative to unmodified control cells, and the magnitude of this expression was modulated by scaffold properties. Histological analyses revealed that matrix mineralization co-localized with cellular distribution, which was confined to the periphery of fibrous collagen and PLGA sponges and around the circumference of PCL microfilaments. Finally, FTIR spectroscopy verified that mineral deposits within all Runx2-engineered scaffolds displayed the chemical signature characteristic of carbonate-containing, poorly crystalline hydroxyapatite. These results highlight the important effect of scaffold properties on the capacity of Runx2-expressing primary dermal fibroblasts to differentiate into a mineralizing osteoblastic phenotype for bone tissue engineering applications.

Animals↗
PubMedDate not supplied

[Comparative study of physico-chemical and biological properties of human somatotropin produced by genetic engineering and isolated from the pituitary gland].

Human somatotropin hormono (STH), produced by means of gene engineering in the complex program "Human growth hormone", managed by the Academy of Sciences of the USSR, Ministry of Medical and Biological Industry of the USSR and Ministry of Public Health of the USSR, was shown to be similar in its physico-chemical properties to the main isoform of highly purified STH, isolated from human hypophysis. As distinct from the hypophyseal STH (STHhyp) containing minor isoforms of the hormone, the preparation of biosynthetic STH (des-Phe1-STH; STHbio) proved to be homogeneous. Studies of biological properties showed that STHbio exhibited high, similar to STHhyp, immunological, growth-stimulating and insulin-like activities as well as it possessed the lipotropic effect in vivo. The lipotropic effect of STHbio in vivo was less prolonged as compared with that of STHhyp, while in vitro it was only slightly expressed in isolated rabbit fat tissue. The effect did not depend on the hormone dose, apparently due to either absence of the hormone modified forms in the STHbio preparation or other hypophyseal contaminating substances responsible for the lipotropic activity. STHbio, similarly to STHhyp, did not stimulate DNA synthesis in blood serum-free culture of human fibroblasts. Studies of STHbio biological properties suggest that multifunctionality of native STHhyp appear to depend on intrinsic specificity of its molecule.

Adipose Tissue↗
PubMed2004

Illuminating the detection chain of bacterial bioreporters.

Engineering bacteria for measuring chemicals of environmental or toxicological concern (bioreporter bacteria) has grown slowly into a mature research area. Despite many potential advantages, current bioreporters do not perform well enough to comply with environmental detection standards. Basically, the reasons for this are the lack of engineering principles in the detection chain in the bioreporters. Here, we dissect critical steps in the detection chain and illustrate how bioreporter design could be improved by mutagenizing specificity and selectivity of the sensing and regulatory proteins, by newer expression strategies and application of different signalling networks. Furthermore, we describe how redesigning bioreporter assays with respect to pollutant transport into the cells and application of other detection devices can decrease detection limits and increase the speed of detection.

Bacteria↗
PubMed1990

Occupational exposure of workers to 1,3-butadiene.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an extent-of-exposure study of the 1,3-butadiene monomer, polymer, and end-user industries to determine the size of the exposed workforce, evaluate control technologies and personal protective equipment programs, and assess occupational exposure to 1,3-butadiene. A new analytical method was developed for 1,3-butadiene that increased the sensitivity and selectivity of the previous NIOSH method. The new method is sensitive to 0.2 microgram per 1,3-butadiene sample. Walk-through surveys were conducted in 11 monomer, 17 polymer, and 2 end-user plants. In-depth industrial hygiene surveys were conducted at 4 monomer, 5 polymer, and 2 end-user plants. Airborne exposure concentrations of 1,3-butadiene were determined using personal sampling for each job category. A total of 692 full shift and short-term personnel and 259 area air samples were examined for the presence of 1,3-butadiene. Sample results indicated that all worker exposures were well below the current OSHA PEL of 1000 ppm. Exposures ranged from less than 0.006 ppm to 374 ppm. The average exposure for all samples was less than 2 ppm. The present American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for 1,3-butadiene is 10 ppm. To reduce the potential for occupational exposure, it is recommended that quality control sampling be conducted using a closed loop system. Also all process pumps should be retrofitted with dual mechanical seals, magnetic gauges should be used in loading and unloading rail cars, and engineering controls should be designed for safely voiding quality control cylinders.

Air Pollutants, Occupational↗
PubMed1994

[Current situation of synthetic immunostimulants].

In the novel field of immunopharmacology, one finds two main classes of potential drugs: immunosuppressive agents (autoimmune disorders, transplantations) and immunostimulants. The latter aim at stimulating the humoral and cell-mediated functions of the immune system, in order to treat various immunodeficiency states and to increase defenses against infectious agents and cancer cells. Some immunostimulants (the so-called adjuvants) enhance the immunogenicity of vaccines. Immunostimulants act directly on various cell populations of the immune system and modulate the production and activity of molecular mediators of the latter (cytokines). From a chemical perspective, one must distinguish between natural macromolecular immunostimulants obtained by extraction or genetic engineering and compounds prepared by chemical synthesis. In the latter class, we find many molecules the structures of which derive from those of natural substances (eucaryotic and procaryotic peptides) and a large number of purely synthetic compounds. The latter belong to a wide variety of chemical families and their mechanisms of action are not always perfectly elucidated. Presently, whereas natural macromolecular immunostimulants (bacterial extracts, cytokines, growth factors) are being increasingly used in human medicine, only a small number of synthetic immunostimulants are beyond the stage of preclinical evaluation or phase I clinical studies.

Adjuvants, Immunologic↗
PubMed2006

The thermal behaviour of enzyme activity: implications for biotechnology.

The way that enzymes respond to temperature is fundamental to many areas of biotechnology. This has long been explained in terms of enzyme stability and catalytic activation energy, but recent observations of enzyme behaviour suggest that this picture is incomplete. We have developed and experimentally validated a new model to describe the effect of temperature on enzymes; this model incorporates additional fundamental parameters that enable a complete description of the effects of temperature on enzyme activity. In this article, we consider the biotechnological implications of this model in the areas of enzyme engineering, enzyme reactor operation and the selection and/or screening of useful enzymes from the environment.

Bioreactors↗
PubMed2003

Non-canonical amino acids in protein engineering.

Methods for engineering proteins that contain non-canonical amino acids have advanced rapidly in the past few years. Novel amino acids can be introduced into recombinant proteins in either a residue-specific or site-specific fashion. The methods are complementary: residue-specific incorporation allows engineering of the overall physical and chemical behavior of proteins and protein-like macromolecules, whereas site-specific methods allow mechanistic questions to be probed in atomistic detail. Challenges remain in the engineering of the translational apparatus and in the design of schemes that can be used to encode both canonical and non-canonical amino acids.

Amino Acids↗
PubMed1989

Host-enhanced chemical indexing in technical databases.

Many files that index engineering, physics, or other technical literature contain references to chemical compounds. Complex chemical formulas in the title or abstract often contain special characters, for example, (,), [,], +, -, degrees, and %. Upper and lower case letters often are also included. A search of these formulas and symbols in the basic index is next to impossible because the terms in this field are usually parsed to all alphanumeric characters without sensitivity to case. It is possible for an online host to use a character-recognition algorithm to scan the title and abstract data for special characters or character strings and place them in a separate index field when such files are loaded. Such an algorithm has been designed by Fachinformationszentrun Energie, Physik, Mathematik GmbH in Karlsruhe, West Germany (FIZ Karlsruhe), the European service center of STN International, the scientific and technical information network. This algorithm recognizes and analyzes chemical formulas, material descriptions, alloys, and eutectic systems as well as nuclear reactions and dopings that appear in the title, abstract, or other fields. These character strings are converted into a standardized form and placed in a new field (the element terms field) which is supplied by the online host during the loading process. A checklist of allowed terms (symbols and chemical formulas) is used to prevent irrelevant terms from being mistaken for legitimate chemical symbols. For instance, the algorithm can recognize that CPU (central processing unit) is not a legitimate chemical formula. It is easy to demonstrate the utility this additional index supplies.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstracting and Indexing↗
PubMed1991

Crystallization and chemical modification of disulfide bond of calf chymosin.

In order to carry out protein engineering of chymosin, purification, crystallization and chemical modification of calf chymosin were undertaken. The resolution of iso-enzymes A,B and the degraded product, fraction C was improved and the period of purification was shortened by using fast protein liquid chromatograph (FPLC). Crystal of approximately cubic shape was obtained from 10 mg/ml purified chymosin B at 4 degrees C after successive dialysis against 1.4, 1.8 and 2.0 M NaCl in 0.1 M sodium phosphate buffer. One disulfide bond located on the surface of chymosin molecule was reduced by 0.72 mM dithiothreitol (DTT) at pH 6.3. The reduced disulfide bond was identified as Cys250-Cys283 by using the method of cyanogen bromide cleavage and peptide separation. The reduction of one disulfide bond resulted in the loss of about 25% activity. Carboxymethylated and mercurated derivatives exhibit the similar activity to that of the reduced enzyme suggesting that Cys250-Cys283 plays some role in keeping the conformation with full activity.

Animals↗