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  • Chemical Engineering  (17,979)
  • Biochemistry and Biotechnology  (13,095)
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  • 1
    Publication Date: 2016-03-19
    Description: Exploiting binding affinities between molecules is an established practice in many fields, including biochemical separations, diagnostics, and drug development; however, using these affinities to control biomolecule release is a more recent strategy. Affinity-controlled release takes advantage of the reversible nature of noncovalent interactions between a therapeutic protein and a binding partner to slow the diffusive release of the protein from a vehicle. This process, in contrast to degradation-controlled sustained-release formulations such as poly(lactic-co-glycolic acid) microspheres, is controlled through the strength of the binding interaction, the binding kinetics, and the concentration of binding partners. In the context of affinity-controlled release--and specifically the discovery or design of binding partners--we review advances in in vitro selection and directed evolution of proteins, peptides, and oligonucleotides (aptamers), aided by computational design.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pakulska, Malgosia M -- Miersch, Shane -- Shoichet, Molly S -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2016 Mar 18;351(6279):aac4750. doi: 10.1126/science.aac4750.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering and Applied Chemistry, Institute of Biomaterials and Biomedical Engineering, and Donnelly Centre, University of Toronto, Toronto, Ontario, Canada. ; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada. ; Department of Chemical Engineering and Applied Chemistry, Institute of Biomaterials and Biomedical Engineering, and Donnelly Centre, University of Toronto, Toronto, Ontario, Canada. Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26989257" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Engineering ; Combinatorial Chemistry Techniques ; Delayed-Action Preparations/*chemistry ; Directed Molecular Evolution ; *Drug Design ; Humans ; Lactic Acid/*chemistry ; Microspheres ; Polyglycolic Acid/*chemistry ; Proteins/*administration & dosage
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2014-11-29
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Langer, Robert S -- Gura, Trisha -- New York, N.Y. -- Science. 2014 Nov 28;346(6213):1146. doi: 10.1126/science.346.6213.1146.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Trisha Gura is a freelance writer who lives in Boston. For more on life and careers visit www.sciencecareers.org.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25430772" target="_blank"〉PubMed〈/a〉
    Keywords: Biotechnology ; *Career Choice ; Chemical Engineering ; *Entrepreneurship ; *Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2014-10-04
    Description: Ethanol toxicity in the yeast Saccharomyces cerevisiae limits titer and productivity in the industrial production of transportation bioethanol. We show that strengthening the opposing potassium and proton electrochemical membrane gradients is a mechanism that enhances general resistance to multiple alcohols. The elevation of extracellular potassium and pH physically bolsters these gradients, increasing tolerance to higher alcohols and ethanol fermentation in commercial and laboratory strains (including a xylose-fermenting strain) under industrial-like conditions. Production per cell remains largely unchanged, with improvements deriving from heightened population viability. Likewise, up-regulation of the potassium and proton pumps in the laboratory strain enhances performance to levels exceeding those of industrial strains. Although genetically complex, alcohol tolerance can thus be dominated by a single cellular process, one controlled by a major physicochemical component but amenable to biological augmentation.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401034/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401034/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lam, Felix H -- Ghaderi, Adel -- Fink, Gerald R -- Stephanopoulos, Gregory -- R01 GM035010/GM/NIGMS NIH HHS/ -- R01-GM035010/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2014 Oct 3;346(6205):71-5. doi: 10.1126/science.1257859. Epub 2014 Oct 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. Whitehead Institute for Biomedical Research, Cambridge, MA, USA. ; Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. ; Whitehead Institute for Biomedical Research, Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu. ; Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25278607" target="_blank"〉PubMed〈/a〉
    Keywords: *Biofuels ; Cation Transport Proteins/genetics ; Cell Culture Techniques ; Cell Membrane/metabolism ; Chemical Engineering ; *Drug Resistance, Fungal/genetics ; Ethanol/*metabolism/pharmacology ; Fermentation ; Genetic Engineering ; Glucose/metabolism ; Hydrogen-Ion Concentration ; Phosphates/*metabolism ; Potassium Compounds/*metabolism ; Proton Pumps/genetics ; Proton-Translocating ATPases/genetics ; Saccharomyces cerevisiae/drug effects/genetics/*metabolism ; Saccharomyces cerevisiae Proteins/genetics ; Up-Regulation ; Xylose/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2012-11-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Savage, Phillip E -- New York, N.Y. -- Science. 2012 Nov 23;338(6110):1039-40. doi: 10.1126/science.1224310.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Chemical Engineering Department, University of Michigan, Ann Arbor, MI 48109, USA. psavage@umich.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23180853" target="_blank"〉PubMed〈/a〉
    Keywords: *Biofuels ; Cell Culture Techniques ; Chemical Engineering ; Chlorophyta/*chemistry/growth & development ; *Hot Temperature ; *Hydrostatic Pressure ; *Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2007-11-17
    Description: Artificial biochemical circuits are likely to play as large a role in biological engineering as electrical circuits have played in the engineering of electromechanical devices. Toward that end, nucleic acids provide a designable substrate for the regulation of biochemical reactions. However, it has been difficult to incorporate signal amplification components. We introduce a design strategy that allows a specified input oligonucleotide to catalyze the release of a specified output oligonucleotide, which in turn can serve as a catalyst for other reactions. This reaction, which is driven forward by the configurational entropy of the released molecule, provides an amplifying circuit element that is simple, fast, modular, composable, and robust. We have constructed and characterized several circuits that amplify nucleic acid signals, including a feedforward cascade with quadratic kinetics and a positive feedback circuit with exponential growth kinetics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, David Yu -- Turberfield, Andrew J -- Yurke, Bernard -- Winfree, Erik -- New York, N.Y. -- Science. 2007 Nov 16;318(5853):1121-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Computation and Neural Systems, California Institute of Technology, MC 136-93, 1200 East California Boulevard, Pasadena, CA91125, USA. dzhang@dna.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18006742" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Catalysis ; Chemical Engineering ; *Computers, Molecular ; DNA/*chemistry ; Entropy ; Equipment Design ; Feedback, Physiological ; Mice ; Nanotechnology ; Nucleic Acid Hybridization ; Rabbits
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Process Safety Progress 17 (1998), S. S3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 7
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    Process Safety Progress 17 (1998), S. 1-8 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent guidelines released by the U.S. EPA define a worst-case scenario as a release under stable atmospheric conditions defined as Pasquil-Gifford stability class F. Unfortunately, very few tests at F stability have been available heretofore to provide a basis for models. Recent test data with propane releases by the German research organization TUV provide a set of 60 experiments conducted specifically to define the effects of atmospheric stability class on dispersion. Of these, 25 tests were at F stability. A comparable number were at each other stability class A through E. In addition 23 tests were at wind speeds under 1.5 m/s in stable atmospheres. This paper reports on adjustments made to our models based on these new data by reducing the originally-postulated sensitivity to stability class. In spite of considerable scatter in the TUV data, particularly between two different types of propane analyzers, the model allows us to extract information by averaging over the tests.
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  • 8
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    Process Safety Progress 17 (1998), S. 9-15 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design and deflagration pressure relief vents is based on correlations developed for various types of combustible materials and for enclosures of different strengths. The primary guideline for deflagration vent design in the US is NFPA 68 Guide for Venting of Deflagrations [5]. That document gives guidance for the design of vents for enclosures containing flammable gases, specifically hydrogen, coke oven gas, propane, and methane. Application of the guide to other gases is achieved using the KG value. Values of KG are published for a relatively small number of gases, as seen in Table D-1 of NFPA 68. This work present KG data on several additional gases obtained in a laboratory scale test vessel along with analysis of the results with respect to published values of fundamental burning velocity.
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  • 9
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    Process Safety Progress 17 (1998), S. 20-22 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most audits try to look at a representative selection of the plant procedures and equipment. An alternative is a survey, a look in depth at selected procedures (such as those for testing alarms and trips, issuing permits-to-work, controlling modifications, taking samples or testing relief devices) or selected equipment (such as level glasses or equipment for handling LPG). If the procedure or equipment is well-chosen, surveys may make a bigger contribution to safety, per person-hour, than a conventional audit.
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  • 10
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    Process Safety Progress 17 (1998), S. 16-19 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multi-disciplinary team developed a guideline for determining access restriction zones around vented solids handling equipment. The guideline provides a method for ensuring the discharge from a vented explosion will not cause injury to personnel. The steps in this method include: calculating the extent of external hazards from vented explosions; identifying potential areas where personnel could be exposed to a hazard; identifying ways to eliminate or reduce the hazard area; and establishing and documenting any access restrictions needed. Hazard zone calculations use the latest knowledge from research into fireball size, flame length and external pressure equations in VDI 3673. The guideline provides guidance for using this information. Options for mitigating or reducing external hazards from vented explosions are also described. As part of the project, the team audited several solids handling systems to look for potential oversights in existing restricted access areas. Some of the team's learnings from these audits are reviewed.
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  • 11
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    Process Safety Progress 17 (1998), S. 23-31 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In May 1996, the Flammable and Combustible Liquids Code Committee of the National Fire Protection Association (NFPA) proposed for adoption by the Association a new edition of NFPA 30, Flammable and Combustible Liquids Code. This new edition was the culmination of two and one-half years' work by the Committee and included one of the most significant changes to that document in some twenty years: the incorporation of mandatory fire protection criteria for warehouses and other inside areas that store flammable and combustible liquids in containers and portable tanks.
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  • 12
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    Process Safety Progress 17 (1998), S. 43-48 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper defines situation awareness (SA) and discusses its importance to operator-machine system safety and functioning in the context of process control activities. Specifically, identified are relationships of human detection of critical process cues converying the status of automated control systems and operator interpretation of the meaning and relevance of such information to the potential for negative incidents in chemical processing. Beyond individual operator SA in interacting with control systems, intra- and inter- work team SA are discussed for supporting individual attainment of process control responsibilities. Factors critical to team SA are discussed. “Road blocks” to team SA are also analytically examined. Lastly, methods for assessing individual and team SA are reviewed and vehicles for relating outcomes of these methods to changes in process control operator and team behavior to improve human-machine system safety and performance are relayed.
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  • 13
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of the ingition behavior of dust-air mixtures due to electrical sparks (MIE, Minimum Ignition Energy) and hot surfaces (MIT, Minimum Ignition Temperature) is important for risk assessments in chemical production plants. The ignition behavior determines the extent and hence the cost of preventive protection measures.This paper describes the use of the minimum ignition energy and minimum ignition temperature as very important safety indexes in practice.Based on the latest results from large scale experiments on pneumatic filling of silos with polymeric materials and new results of full scale filling tests using Flexible Intermediate Bulk Containers (FIBC) manufactured from a variety of materials, guidance can be given to ensure safe operation in different situations such as filling, emptying operations, type of powder handled.The aim of this paper is to assist people dealing with product. It reflects the present state of the art and current knowledge of the assessment and measures associated with powder handling.
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  • 14
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    Process Safety Progress 17 (1998), S. S3 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 15
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    Process Safety Progress 17 (1998), S. 83-85 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Safety, health and loss prevention are major areas of interst for the American Institute of Chemical Engineers (AIChE). There has been an evolution of these concerns over the years in the Institute just as it has in industry. This article chronicles this evolution.
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  • 16
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    Process Safety Progress 17 (1998), S. 171-175 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An explosion occurred in a petroleum product storage tank at a refinery. The liquid petroleum product was a heavy oil used as an asphalt extender. There were no injuries, but the cleanup was costly. The storage tank was one of several which received the product stream from a dehydration unit. The accident occurred shortly after the refinery was brought back on-line following a shutdown for schduled maintenance.This was the first incident of this kind to occur at this facility. Analysis of the process data and eyewitness observations indicated that the dehydration tower, which was supposed to be maintained at a minimum of 100°C during the shutdown, was allowed to drift below 100°C for an unknown period of time. This deviation enabled liquid water to enter the storage tank. Three operational factors contributed to the accident. Corrective actions were recommended to prevent a recurrence of a similar incident.
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  • 17
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    Process Safety Progress 17 (1998), S. 157-170 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Risk analysis in chemical process industries is an elaborate exercise involving several steps from preliminary hazard identification to development of credible accident scenarios, to preparation of strategies for prevention or control of damage.All this requires substantial inputs of time and money. In order to get an approximate yet workable assessment of risk at much lesser costs, indices have been developed which link typical findings of elaborate risk analysis to scales of risk. The scales, in turn, provide workable measures of hazards/risks/safety.In the past, indices have been reported for swift risk assessment - the noteworthy among them include Dow fire and explosion index, Mond fire, explosion and toxicity index, IFAL index, and mortality index. A few rapid ranking techniques have also been proposed.This paper presents a new system of methodologies for Hazard Identification and Ranking (HIRA). The system consists of two indices: one for fire and explosion hazards and another for the hazard due to likely release of toxic chemical. The magnitudes of these indices indicate the severity of the likely accident; in terms of the size of the impacted area.HIRA has been applied to a typical chemical process industry - a sulfolane plant - and its performance has been compared with that of the Dow's and the Mond's indices. The study reveals that HIRA is more sensitive and accurate than the other indices.
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  • 18
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    Process Safety Progress 17 (1998), S. 184-189 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosions have been with us for a long time. The first record of a dust explosion occurred in Turin, Italy, on December 14, 1785 [1]. The detailed record of this event is left to us by Count Morozzo. The event took place in Mr. Giacomelli's bakery. We know from his account that the weather was unseasonably dry, that a boy who worked in the bakery was using a shovel to stir and transfer the flour to a chute from a store room to the bakery and he had a lighted lamp to work by. The rest, as the saying goes, is history. No one was killed, and the building was saved by the sagacious fact of having plenty of windows. Since that first record, of course, there have been many explosions with much loss of life and significant economic consequences.
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  • 19
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    Process Safety Progress 17 (1998), S. 176-183 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The safest method to prevent fires and explosions of flammable mixtures in the first place. This method requires detailed knowledge of the flammability region as a function of the fuel, oxygen, and nitrogen concentrations. A triangular flammability diagram is the most useful tool to display the flammability region, and to determine if a flammable mixture is present during plant operations.This paper describes how to draw and use a flammability diagram. A procedure to estimate the flammability region using the available and sometimes limited data is discussed. The paper also shows how to use the flammability diagram with plant operations involving inerting and purging, and from bringing vessels into and out of service. A compilation of flammability diagrams for 30 materials, based on previously published data is provided.An automated apparatus for acquiring data for a flammability diagram is described. The apparatus consists of a 20-L sphere with an automated gas mixing system, a fuse-wire ignition system, and a high speed pressure measurement and data acquisition system. Data derived from the apparatus includes flammability limits, maximum pressure during combustion, and the maximum pressure rate. The effect of fuse-wire ignitor dynamics on the results is studied. A flammability diagram for methane drawn from data obtained from the apparatus, is presented.
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  • 20
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    Process Safety Progress 17 (1998), S. 190-195 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The RSST DIERS vent sizing methodology is revised to provide realistic design equations for reactive systems consistent with available large-scale experience. Using easy to obtain RSST data such as rate of temperature rise and rate of pressure rise excellent agreement is illustrated for hybrid, vapor and gassy reactive systems.
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  • 21
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    Process Safety Progress 17 (1998), S. 200-208 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 22
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    Process Safety Progress 17 (1998), S. 209-212 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: HFC-227ea (CF3CHFCF3;1, 1, 1, 2, 3, 3, 3-heptafluoropropane) is an effective replacement for Halon 1301 in fire suppression systems, providing rapid extinguishment of flames through a combination of physical and chemical mechanisms. The vast majority of applications for HFC-227ea involve the protection of Class A hazards, which are characterized by low fuel loadings and low energy output, with fire sizes often in the range of 5-10 kW. Mid- and large-scale testing has demonstrated that HFC-227ea, at its minimum design concentration of 7.0% v/v, is effective at extinguishing fires typical of those expected to occur in electronic data processing (EDP) facilities, telecommunication facilities and anechoic chambers. The levels of HF produced following extinguishment of typical Class a fires with HFC-227ea were well below the estimated mammalian LC50 and the human Dangerous Toxic Load (DTL), and do not appear to present a threat to electronic equipment.
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  • 23
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method is described to enhance the management of process safety risks such that the number and type of safety systems protecting against any hazard are consistently predicated upon risk. Further, that such an assignment of safety systems can be made consistent throughout an organization. This consistency is gained through standardization of qualitative risk ranking and by setting company guidelines.
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  • 24
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    Process Safety Progress 17 (1998), S. 288-296 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ammonia storage tank was built at the BASF Antwerp site in 1969 on land reclaimed from the sea. After several years of operation uneven foundation settlement, of up 2, occurred. In order to assure stability of this area for the next operation period (at least 10 years) measures were taken to ensure continued safe operation. One key measure was strain gauge monitoring at the location of maximum stress.
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  • 25
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    Journal of Peptide Science 4 (1998), S. 15-20 
    ISSN: 1075-2617
    Keywords: ion transport ; kinetics ; lithium ; NMR ; shift reagent ; vesicles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ion transport across phospholipid vesicles was studied by 7Li and 23Na-NMR using an aqueous anionic paramagnetic shift reagent, dysprosium nitrilotriacetate [Dy(NTA)2]3-, mediated by ionophores, lasalocid A and A23187. The intra- and extracellular 7Li and 23Na-NMR signals were well separated (20 Hz) at mM concentration of the shift reagent. The observed data on the rate constant for lithium transport across DPPC vesicles at various concentrations of the ionophores indicated that lasalocid A is a more efficient carrier for lithium ion compared with the sodium ion transport by this ionophore, while A23187 was not specific to either of the ions (Li or Na). ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 26
    ISSN: 1075-2617
    Keywords: Cα,α-disubstituted amino acids ; crystal structure ; molecular dynamics ; conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of three fully protected tripeptides containing the Dφg residue (Cα,α-diphenylglycine) in the central position are reported, namely Z-Gly-Dφg-Gly-OMe (a), Z-Gly-Dφg-Aib-OMe (b) and Z-Aib-Dφg-Aib-OMe (c). The molecular conformations are quite unusual because the Dφg residue adopts a folded conformation in the 310-helical region when the following residue adopts a folded conformation of opposite handedness (peptidesbandc). In contrast, the Dφg residue adopts the more frequently observed fully extended conformation when the following residue adopts a semi-extended conformation (peptidea). These findings are in agreement with the theoretical calculations on Ac-Dφg-Aib-NHCH3 and Ac-Aib-Dφg-NHCH3 also reported in this work. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 27
    ISSN: 1075-2617
    Keywords: α-hydroxymethylserine peptides ; isopropylidene protecting group ; crystal structure ; peptide conformation ; peptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic methodology has been developed for peptide bond formation with α-hydroxmethylserine as the carboxyl or amino component and also for the preparation of homo-sequences. The key intermediate, O,O-protected α-hydroxymethylserine in the form of an isopropylidene derivative, is easily accessible and represents the first example of a heterocyclic Cα,α-disubstituted amino acid containing an 1,3-dioxane ring. The use of this intermediate facilitates protection of the sterically hindered amino and carboxyl groups and is advantageous for the coupling and deprotection steps. X-ray structure determination of Z-HmS(Ipr)-Ala-OMe revealed that the two crystallographically independent molecules present in the asymmetric unit adopt an S-shaped conformation. In the one molecule the achiral HmS(Ipr) residue has the torsion angle values (φ==61.4°,ψ=40.8°) in the left-handed helical region of the Ramachandran map, while in the second molecule the negative torsion angles (φ=-60.1°, ψ=-44.4°) are associated with the right-handed helix. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 28
    ISSN: 1075-2617
    Keywords: conformational studies ; -OBg esters ; protein tyrosine kinase ; src-PTK ; synthetic peptides ; tyrosine phosphorylation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two Tyr residues are supposed to play a crucial role in the regulation of protein tyrosine kinases of the Src family. Autophosphorylation of Src Tyr416 correlates with enzyme activation, while phosphorylation of C-terminal Tyr527 by Csk gives rise to inactive forms of Src kinases.It has previously been demonstrated that the Src-like tyrosine kinase expressed by the oncogenelyndisplays a particularly high affinity (Km20 μm) toward the dimeric linear and cyclic derivatives of the heptapeptide H-Glu-Asp-Asn-Glu-Tyr-Thr-Ala-OH which reproduces the main autophosphorylation site of most of the Src enzymes. Under the experimental conditions used only one Tyr residue of the dimeric sequence can be phosphorylated [P. Ruzza, A. Calderan, B.Filippi, B. Biondi, A. Donella Deana, L. Cesaro, L. A. Pinna & G. Borin (1995) Int. J. Peptide Protein Res. 45, 529-539].The present study addresses the problem of the efficiency displayed by Lyn towards the two Tyr residues located at positions 5 and 12 of the dimeric peptide. To this purpose, two tetradecapeptides were synthesized by the classical solution method, each containing one of the two Tyr residues alternatively replaced by Phe, and the corresponding univocal cyclic form. A possible correlation between the different structural properties induced by the modifications of the native sequence and the ability of the peptides to act as Lyn substrates was noted. The kinetic data obtained indicate that Lyn phosphorylates the residues located at different positions in the two linear analogues differently. In particular, while the Tyr5, Phe12 derivative presents aKmvalue similar to those obtained for the dimeric linear and cyclic unmodified analogues, theKmvalue of the Phe5, Tyr12 derivative is two-fold higher than those found for the above-mentioned peptides. Moreover, as previously reported for the linear and cyclic dimeric forms of the native sequence, in the mono-tyrosine containing series of dimers the still conformationally flexible cyclic derivative shows a phosphorylation efficiency two-fold higher than those found for the linear derivatives. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 29
    ISSN: 1075-2617
    Keywords: circular dichroism ; FT-IR absorption ; glycopeptides ; 1H nuclear magnetic resonance ; oligo-peptides ; peptide conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stepwise solution syntheses are described of the homo-oligomers Z-(Thr)n-NHCH3 (n=1-4, I1-4), Z-{[Gal(Ac)4β]Thr}n-NHCH3(n=1-5, II1-5) and Z-[(Galβ)Thr]n-NHCH3 (n=1-5, III1-5). Members of the III1-5 series were obtained by de-acetylation of the corresponding oligomers of the II1-5 series. The conformational preferences of the terminally protected homo-peptides of the three series were investigated by FT-IR absorption spectroscopy both in the solid state and in CDCl3 solution, at various concentrations. Proton NMR measurements in CDCl3 and in DMSO-d6 were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO-d6 (range 298-335 K) and in CDCl3 (range 298-320 K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl3 solution for Z-(Thr)4-NHCH3 and for the entire III1-5 series. The existence of unordered structures in the carbohydrate-free oligomers and of more or less extended, organized structures in the glycosylated derivatives is indicated by the NMR and IR measurements. The sugar moieties apparently show a structure-inducing effect on the peptide chain. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 30
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 1-14 
    ISSN: 1075-2617
    Keywords: Mitsunobu reaction ; N-alkyl amino acid synthesis ; amino acid derivatives synthesis ; β-lactam formation ; peptide oxazolines and thiazolines ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mitsunobu reaction - the nucleophilic substitution of an alcoholic hydroxyl group mediated by the redox system trialkylphosphine/dialkyl azodicarobxylate - is widely used in the chemistry of biologically active compounds. The paper deals with applications of the Mitsunobu reaction in amino acid and peptide chemistry. The process provides easy access to many unnatural amino acids and derivatives. Since the reaction occurs with complete inversion of the configuration at the carbinol chiral centre, it can be used for the synthesis of diastereoisomers of hydroxy- and tioprolines. Cyclization of β-hydroxy amino acid containing peptides under Mitsunobu reaction conditions leads to a constrained peptide that mimics the stabilizing reverse turn secondary structure. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 31
    ISSN: 1075-2617
    Keywords: fluorescence quenched assay ; inhibitor library ; Trypanosoma cruzi ; cathepsin B and L inhibitors ; Parasitic protease inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A PEGA-resin was derivatized with a 3:1 mixture of hydroxymethyl benzoic acid and Fmoc-Lys(Boc)-OH and the fluorogenic substrate Ac-Y(NO2)KLRFSKQK(Abz)-PEGA was assembled on the lysine using the active ester approach. Following esterification of the hydroxymethyl benzoic acid with Fmoc-Val-OH a library XXX-k/r-XXXV containing approximately 200,000 beads was assembled by split synthesis. The resulting ‘one bead, two peptides’ library was subjected to extensive hydrolysis with cruzipain. One hundred darker beads were isolated and the 14 most persistently dark beads were collected and sequenced. The putative inhibitor peptides and several analogues were synthesized and found to be competitive μM to nM inhibitors of cruzipain in solution. The inhibitory activity was found to be unspecific to cruzipain when compared with cathepsins B and L and specific when compared with kallikrein. One of the inhibitors was docked into the active site of the cathepsin B and was found most probably to bind to the enzyme cavity in an unusual manner, owing to the inserted D-amino acid residue. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 32
    ISSN: 1075-2617
    Keywords: NMR ; random coil ; rhinovirus ; synthetic vaccine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of a [15]-peptide (H-VKAETRLNPDLQPTE-NH2) from VP2 of rhinovirus HRV2 complexed with a Fab fragment was previously shown by X-ray crystallographic studies to be similar to the one found in the corresponding region of HRV1A. Antibodies raised against this peptide bind to and neutralize HRV2. In order to identify structural features preserved in solution that may explain the ability of this short peptide to mimic the structure of the protein surface, the peptide has been studied by NMR in aqueous solution as well as under denaturing conditions.The peptide is shown to be a random coil in solution. However, the sequence forming a 310 helix in the complex is biased into a helical conformation according to NOE intensity data as well as from urea and pH titrations. This sequence adopts the same conformation in an unrelated protein. NOE data suggest that a β-turn found in the complex may be sampled in solution. Also, Glu4, interacting with Arg6 in the crystal, has a reduced pKa value in solution. It is concluded that the local structure present in the random coil state of VP2(156-170) contains enough information to direct the production of antibodies that bind to and neutralize HRV2. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 33
    ISSN: 1075-2617
    Keywords: bradykinin ; antagonists ; dehydrophenylalanine ; smooth muscle contraction ; radio-ligand binding studies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Continuing the studies on structural requirements of bradykinin antagonists, it has been found that analogues with dehydrophenylalanine (ΔPhe) or its ring-substituted analogues (ΔPhe(X)) at position 5 act as antagonists on guinea pig pulmonary artery, and on guinea pig ileum. Because both organs are considered to be bradykinin B2receptor tissues, the analogues with ΔPhe or ΔPhe(X) at position 5, but without any replacement at position 7, seem to represent a new structural type of B2receptor antagonist. All the analogues investigated act as partial antagonists; they inhibit the bradykinin-induced contraction at low concentrations and act as agonists at higher concentrations. Ring substitutions by methyl groups or iodine reduce both the agonistic and antagonistic activity. Only substitution by fluorine gives a high potency. Incorporation of ΔPhe into different representative antagonists with key modifications at position 7 does not enhance the antagonist activity of the basic structures, with one exception. Only the combination of ΔPhe at position 5 with DPhe at position 7 increases the antagonistic potency on guinea pig ileum by about one order of magnitude. Radio-ligand binding studies indicate the importance of position 5 for the discrimination of B2receptor subtypes. The binding affinity to the low-affinity binding site (KL) was not significantly changed by replacement of Phe by ΔPhe. In contrast, ring-methylation of ΔPhe results in clearly reduced binding to KL. The affinity to the high-affinity binding site (KH) was almost unchanged by the replacement of Phe in position 5 by ΔPhe, whereas the analogue with 2-methyl-dehydrophenylalanine completely failed to detect the KH-site. The peptides were synthesized on the Wang-resin according to the Fmoc/Butstrategy using Mtr protection for the side chain of Arg. The dehydrophenylalanine analogues were prepared by a strategy involving PyBop couplings of the dipeptide unit Fmoc-Gly-ΔPhe(X)-OH to resin-bound fragments. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 34
    ISSN: 1075-2617
    Keywords: Litoria genimaculata ; skin glands ; glandular secretions ; peptides ; antibiotic activity ; maculatins 1 ; caerin 1.1 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six peptides have been isolated and characterized from the dorsal glands of the tree frog Litoria genimaculata. One of these is the known hypotensive peptide caerulein; the others have been named maculatins. The amino acid sequences of the maculatin peptides have been determined using a combination of fast atom bombardment mass spectrometry and automated Edman sequencing. Four of the maculatin peptides show antibiotic activity, with maculatin 1.1 [GLFGVLAKVAAHVVPAIAEHF(NH2;)] showing the most pronounced activity, particularly against Gram-positive organisms. Maculatin 1.1 resembles the known caerin 1 antibiotic peptides, except that four of the central amino acid residues (of the caerin 1 system) are missing in maculatin 1.1. A comparison of the antibiotic activity of maculatin 1.1 with those of caerin 1.1 is reported. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 35
    ISSN: 1075-2617
    Keywords: gelsolin ; actin ; capping proteins ; synthetic peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gelsolin is a protein that severs and caps actin filaments. The two activities are located in the N-terminal half of the gelsolin molecules. Severing and subsequent capping requires the binding of domains 2 and 3 (S2-3) to the side of the filaments to position the N-terminal domain 1 (S1) at the barbed end of actin (actin subdomains 1 and 3). The results provide a structural basis for the gelsolin capping mechanism. The effects of a synthetic peptide derived from the sequence of a binding site located in gelsolin S2 on actin properties have been studied. CD and IR spectra indicate that this peptide presented a secondary structure in solution which would be similar to that expected for the native full length gelsolin molecule. The binding of the synthetic peptide induces conformational changes in actin subdomain 1 and actin oligomerization. An increase in the polymerization rate was observed, which could be attributed to a nucleation kinetics effect. The combined effects of two gelsolin fragments, the synthetic peptide derived from an S2 sequence and the purified segment 1 (S1), were also investigated as a molecule model. The two fragments induced nucleation enhancement and inhibited actin depolymerization, two characteristic properties of capping. In conclusion, for the first time it is reported that the binding of a small synthetic fragment is sufficient to promote efficient capping by S1 at the barbed end of actin filaments. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 36
    ISSN: 1075-2617
    Keywords: Synthetic peptide library ; one-bead-one-compound ; partial cleavage ; soluble phase screening ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A library system was developed for the discovery of bioactive peptides. Library synthesis and peptide sequencing was performed on a solid support while the screening for bioactivity was done with peptides in solution. The peptides were synthesized by split and mix, one-bead-one-peptide library synthesis, using a Tentagel S-NH2 solid support with a loading of approximately 100 pmol/bead. The major part of the peptide was connected to the support by a single acid-labile linker and a minor part of the peptide was acid-stabile attached to the polymer. The percentage of acid-stabile attached peptides could easily be controlled during modification of the amino functionalities of the resin at the start of the process. The cleavage rate of the acid-labile attached peptide from the resin depends on the composition of the cleavage mixture. When cleavage conditions were carefully controlled, a three-step partial cleavage protocol allowed for convergent bioactivity screening on peptide libraries using only one type of acid-labile linker. The partial cleavage and convergent screening procedure was repeated three times, after which the bead containing the bioactive peptide was sequenced. As such a bead still contained acid-stabile attached peptide, the Edman sequencing was straightforward and repetitive yields were excellent because the immobilized peptide was not washed out. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 37
    ISSN: 1075-2617
    Keywords: Bradykinin antagonist ; dimer ; diaminodicarboxylic acid ; bridge residue ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enhancement of a ligand's interaction with a receptor through presenting the ligand in multimeric form is a topic of general interest. Thus dimerization of single-chain bradykinin antagonist peptides has previously been shown to be beneficial in terms of potency and duration of action. While crosslinking polypeptides at terminal positions using suitable dicarboxylic acids and diamines is comparatively straightforward synthetically, internal dimerizations are usually achieved through oxidation or double S-alkylations of cysteine residues, resulting in metabolically unfavourable disulphide and thioether cross-links. Using suitably modified standard solid-phase peptide synthesis protocols, dimeric bradykinin antagonist peptides [H-(d-Arg)-Arg-Pro-Hyp-Gly-Phe]2-X-[(d-Phe)-Leu-Arg-OH]2 were synthesized where X corresponds to a l,l-2,7-diaminosuberic or l,l-2,9-diaminosebacic acid residue, respectively. The biological activity of these peptides was comparable to that of conventional dimeric bradykinin antagonists cross-linked through cystine or bis(succinimido)alkyl bridges. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 38
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 300-304 
    ISSN: 1075-2617
    Keywords: Cryochemistry ; frozen organic solution ; peptide coupling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The freezing effect on peptide coupling in organic solutions of different polarity has been investigated and compared with the results obtained in liquid phase. The model reaction of DCC-activated coupling of Boc-Ala-Phe-OH with H-Ala-OBut has been carried out in dioxane, dimethylsulfoxide and formamide, as well as in mixtures (90%/10%, v/v) of dioxane with acetonitrile, dimethylformamide, dimethylsulfoxide and formamide.The reactions have been traced and evaluated by RP-HPLC analysis. Freezing the reaction mixture resulted in all cases in a significant suppression of the N-dipeptidylurea side-product formation together with a slight decrease of tripeptide epimerization. The coupling yields and the side effects depended on the solvent, with the dioxane and dioxane/acetonitrile mixture produced the best results. The role of freezing and solvent in the improved results is discussed. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 39
    ISSN: 1075-2617
    Keywords: Coloured neurotensin analogues ; coloured peptides ; coloured peptide libraries ; peptide labelling with chromophores ; peptide synthesis on coloured support ; solubilizing tags ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several methods were developed for the solid-phase synthesis (SPPS) of coloured peptides and peptide libraries. At first a bifunctional red compound, 4-(4-(N-ethyl-N-(3-(tert-butyloxycarbonyl)aminopropyl)amino)phenylazo)benzoic acid (Boc-EPAB), was coupled with chloromethyl resin to obtain a new solid support suitable for SPPS using Boc chemistry. Peptides synthesized on this coloured resin had the chromophore at their C-termini. N-terminally coloured peptides were synthesized on a traditional solid support, coupled with chromophoric carboxylic acid before cleavage. A model pentapeptide, Phe-Ala-Val-Leu-Gly, and its ten derivatives were synthesized and their properties studied. It was found that the presence of chromophores decreases the water solubility of peptides. However, insertion of solubilizing tags (penta-lysine sequences or polyoxyethyl chains) into the molecule of any coloured derivative resulted in enhancement of the solubility. The RP-HPLC hydrophobicity indexes (ϕ0) of the coloured peptides were also determined because ϕ0 values are closely related to their water solubility. A coloured pentapeptide library was synthesized using the portioning-mixing method. Each component of this library contained the red azo dye (EPAB) and the penta-lysine tag. Before the last coupling step the samples were not mixed. All of the 19 sub-libraries obtained after cleavage were readily soluble in water, giving intense red solutions.The effect of chromophore (EPAB) and/or penta-lysine solubilizing tag on the biological activity was also studied. Potencies of the bovine neurotensin 8-13 fragment and its different coloured and penta-lysine derivatives were compared in isolated longitudinal muscle strips of guinea pig ileum. It was shown that the hexapeptide with penta-lysine tag had almost the same activity as the 8-13 fragment itself. The activity of the EPAB-derivative was found to be rather low. However, the presence of the solubilizing tag in the coloured hexapeptide compensated the negative effect of the chromophore. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 40
    ISSN: 1075-2617
    Keywords: ion channels ; amphipathicity ; α-helices ; bilayers ; SDS micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic alamethicin analogs, in which all Aib residues had been replaced by Leu (L2) then proline 14 replaced by an alanine (L5), were studied in SDS micelles using circular dichroism and NMR spectroscopy. Nuclear Overhauser effects were used as constraints for molecular modelling. The structures determined for both peptides in SDS micelles were compared with those previously obtained in methanol in order to establish a secondary structure/ionophore activity relationship. Our results indicated that a shortening of peptide helices could be responsible for the observed decrease in ion channel lifetimes. However, the length of helices may not by itself explain the drastic destabilization of channels when Pro14 of alamethicin is replaced by Ala in L5. Indeed analysis of the helical wheel of L5 reveals heterogeneity in the amphipathicity depending on the medium. Thus, loss of amphipathicity seems to underly the observed destabilization of channels. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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  • 41
    ISSN: 0884-3996
    Keywords: stopped-flow ; chemiluminescence ; multicomponent analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The stopped-flow technique was employed to measure chemiluminescent emission from the reaction of a mixture of oxalate and proline with a chemiluminescence reagent, tris(2,2′-bipyridine)ruthenium(III), or Ru(bpy)33+. Ru(bpy)33+ is a versatile reagent and is often used in bioanalytical applications, including the detection of certain drugs and their metabolites, for example. Unfortunately, Ru(bpy)33+ has not yet been fully examined as a possible chemiluminescence reagent for simultaneous kinetic determinations. In this work, a differential reaction rate method, based on simple least squares regressions of the pseudo-first order decay data, was used to resolve two compounds, oxalate and proline, reacting simultaneously with Ru(bpy)33+. Our results indicate that stopped-flow analyses with Ru(bpy)33+ could provide a viable method for simultaneous determinations of unresolvable analytes of environmental and pharmaceutical importance. © 1998 John Wiley & Sons, Ltd.
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  • 42
    ISSN: 0884-3996
    Keywords: chemiluminescent immunoassay ; acridinium ester ; fish ; salmon ; growth hormone ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: An immune complex transfer two-site chemiluminescent immunoassay (CLIA) for salmon growth hormone (GH) was developed to measure serum GH in alevin chum salmon (Oncorhynchus keta) using a chemiluminescent acridinium ester as a label. The immune complex transfer method dramatically reduced non-specifically bound of acridinium ester-labelled antibody without a decrease in the specific binding. Consequently, we could detect lower levels of GH than achieved previously in a two-site CLIA for salmon GH. The detection limit of the assay was 7.8 fg/mL and the standard curve was linear up to 250 fg/mL. Coefficients of variation were 2.2-7.7% within-assay and 5.3-9.1% between-assay. We have developed a highly sensitive and reproducible GH method and applied it to measurement of GH in alevin chum salmon. © 1998 John Wiley & Sons, Ltd.
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  • 43
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 198-210 
    ISSN: 0006-3592
    Keywords: Xanthan fermentation ; agitator speed ; caverns ; dissolved oxygen ; specific oxygen uptake rate ; specific Xanthan production rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Agitation speed affects both the extent of motion in Xanthan fermentation broths because of their rheological complexity and the rate of oxygen transfer. The combination of these two effects causes the dissolved oxygen concentration and its spatial uniformity also to change with agitator speed. Separating these complex interactions has been achieved in this study in the following way. First, the influence of agitation speeds of 500 and 1000 rpm has been investigated at a constant nonlimiting dissolved oxygen concentration of 20% of air saturation using gas blending. Under these controlled dissolved oxygen conditions, the results demonstrate that the biological performance of the culture was independent of agitation speed as long as broth homogeneity could be ensured. With the development of increasing rheological complexity lending to stagnant regions at Xanthan concentrations 〉20 g/L, it is shown that the superior bulk mixing achieved at 1000 rpm, compared with 500 rpm, leading to an increased proportion of the cells in the fermentor to be metabolically active and hence higher microbial oxygen uptake rates, was responsible for the enhanced performance. Second, the effects of varying dissolved oxygen are compared with a control in each case with an agitator speed of 1000 rpm to ensure full motion, but with a fixed, nonlimiting dissolved oxygen of 20% air saturation. The specific oxygen uptake rate of the culture in the exponential phase, determined using steady-state gas analysis data, was found to be independent of dissolved oxygen above 6% air saturation, whereas the specific growth rate of the culture was not influenced by dissolved oxygen, even at levels as low as 3%, although a decrease in Xanthan production rate could be measured. In the production phase, the critical oxygen level was determined to be 6% to 10%, so that, below this value, both specific Xanthan production rate as well as specific oxygen uptake rate decreased significantly. In addition, it is shown that the dynamic method of oxygen uptake determination is unsuitable even for moderately viscous Xanthan broths. © 1998 John Wiley & Sons, Inc. Biotechnol. Bioeng. 57: 198-210, 1998.
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  • 44
    ISSN: 0006-3592
    Keywords: protein ; conformational memory ; organic solvent ; molecular imprinting ; enzyme ; catalysis ; transition state analogue ; bovine serum albumin ; β-lactoglobulin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The induction of catalytic activity in proteins by lyophilization in the presence of a transition state analogue (biomolecular imprinting) has been attempted. It was shown that proteins which were freeze-dried with n-isopropyl-4-nitrobenzyl-amine (a transition state analogue for the reaction of dehydrofluorination of 4-fluoro-4-[p-nitrophenyl] butan-2-one) displayed higher β-elimination activity as compared to their-non-imprinted counterparts. It was also found that native bovine serum albumin has a high dehydrofluorination activity towards the above substrate with kinetic parameters rather similar to those of a catalytic antibody prepared by Shokat et al. (1989). A comparison of the kinetic parameters determined in this study with those obtained for analogous catalytic antibodies and imprinted polymers was made. © 1998 John Wiley & Sons, Inc. Biotechnol. Bioeng. 57: 211-215, 1998.
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  • 45
    ISSN: 0006-3592
    Keywords: waste gas treatment ; trickle-bed reactor ; toluene ; biomass removal ; biofilm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new reactor for biological waste gas treatment was developed to eliminate continuous solvents from waste gases. A trickle-bed reactor was chosen with discontinuous movement of the packed bed and intermittent percolation. The reactor was operated with toluene as the solvent and an optimum average biomass concentration of between 5 and 30 kg dry cell weight per cubic meter packed bed (m3pb). This biomass concentration resulted in a high volumetric degradation rate. Reduction of surplus biomass by stirring and trickling caused a prolonged service life and prevented clogging of the trickle bed and a pressure drop increase. The pressure drop after biomass reduction was almost identical to the theoretical pressure drop as calculated for the irregular packed bed without biomass. The reduction in biomass and intermittent percolation of mineral medium resulted in high volumetric degradation rates of about 100 g of toluene m-3pb h-1 at a load of 150 g of toluene m-3pb h-1. Such a removal rate with a trickle-bed reactor was not reported before. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 497-503, 1998.
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  • 46
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 505-509 
    ISSN: 0006-3592
    Keywords: lipases ; Candida antarctica lipase ; emulsifiers ; food additives ; glucose ; surfactants ; synthesis in organic solvents ; glucose fatty acid esters ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Selective production of emulsifiers from glucose and fatty acids has been achieved using an immobilized Candida antarctica lipase. Optimization of process selectivity considers the solubilities of the sugar and its monoesters in acetone at different temperatures, the percentage of this organic solvent in the reaction mixture, and the reaction temperature. The solvent (acetone) is both easily eliminated and accepted by the European Community for use in the manufacture of foods and/or food additives. Different fatty acids with a longer length chain than that of caprylic acid may be employed. For saturated fatty acids longer than lauric acid, continuous precipitation of the monoester as it is formed at 40°C permits nearly complete conversion (98%) of glucose to the monoester within 2-3 days. The procedure does not require total dissolution of the sugar, and precipitation of the monoester permits selective conversion of charges of glucose higher than 100 mg/mL solvent. A scaleup of the process under the optimum conditions gives high yields of 6-O-lauroyl glucose, which may be readily prepared on a gram scale. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 505-509, 1998.
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  • 47
    ISSN: 0006-3592
    Keywords: NAD(H) retention ; coenzyme regeneration ; coupled reactions ; glucose dehydrogenase ; lactate dehydrogenase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: NAD(H) was retained in a noncharged ultrafiltration membrane reactor for the simultaneous and continuous production of l-lactate and gluconate with coenzyme regeneration. Polyethyleneimine (PEI), a 50-kDa cationic polymer, achieved coenzyme retentions above 0.8 for PEI/NAD(H) molar ratios higher than 5. The ionic strength of the inlet medium caused a decrease of NAD(H) retention that can be counterbalanced by an initial addition of 1% bovine serum albumin (BSA). Continuous reactor performance in the presence of PEI and BSA showed that NAD(H), glucose dehydrogenase, and lactate dehydrogenase were retained by 10-kDa ultrafiltration membranes; l-lactate and gluconate were produced at conversions higher than 95%. PEI enhanced the thermal stability of the enzymes used and increased the catalytic efficiency of glucose dehydrogenase, while no effect was found on the kinetic parameters of lactate dehydrogenase. A model that implements the kinetic equations of the two enzymes describes the reactor behavior satisfactorily. In brief, the use of PEI to retain NAD(H) is a new interesting approach to be widely applied in continuous synthesis with the large number of known dehydrogenases. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 510-517, 1998.
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  • 48
    ISSN: 0006-3592
    Keywords: ammonium ; UDP-GlcNAc ; N -glycosylation ; BHK-21 cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of different ammonium concentrations and glucosamine on baby hamster kidney (BHK)-21 cell cultures grown in continuously perfused double membrane bioreactors was investigated with respect to the final carbohydrate structures of a secretory recombinant glycoprotein. The human interleukin-2 (IL-2) mutant glycoprotein variant IL-Mu6, which bears a novel N-glycosylation site (created by a single amino acid exchange of Gln100 to Asn), was produced under different defined protein-free culture conditions in the presence or absence of either glutamine, NH4Cl, or glucosamine. Recombinant glycoprotein products were purified and characterized by amino acid sequencing and carbohydrate structural analysis using matrix-assisted laser desorption ionization time of flight mass spectrometry, high-pH anion-exchange chromatography with pulsed amperometric detection, and methylation analysis. In the absence of glutamine, cells secreted glycoprotein forms with preponderantly biantennary, proximal fucosylated carbohydrate chains (85%) with a higher NeuAc content (58%). Under standard conditions in the presence of 7.5 mM glutamine, complex-type N-glycans were found to be mainly biantennary (68%) and triantennary structures (33%) with about 50% containing proximal α1-6-linked fucose; 37% of the antenna were found to be substituted with terminal α2-3-linked N-acetylneuraminic acid. In the presence of 15 mM exogenously added NH4Cl, a significant and reproducible increase in tri- and tetraantennary oligosaccharides (45% of total) was detected in the secretion product. In glutamin-free cultures supplemented with glucosamine, an intermediate amount of high antennary glycans was detected. The increase in complexity of N-linked oligosaccharides is considered to be brought about by the increased levels of intracellular uridine diphosphate-GlcNAc/GalNAc. These nucleotide sugar pools were found to be significantly elevated in the presence of high NH3/NH4+ and glucosamine concentrations. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 518-528, 1998.
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  • 49
    ISSN: 0006-3592
    Keywords: bacteriophage λ ; Q - mutant ; Escherichia coli ; recombinant protein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We previously demonstrated that the λ system integrated into the host chromosome can overcome the instability encountered in continuous operations of unstable plasmid-based expression vectors. High stability of a cloned gene in a lysogenic state and a high copy number in a lytic state provide cloned-gene stability and overexpression in a two-stage continuous operation. But the expression by the commonly used S- mutant λ was only twice as high as that of the single copy. To increase the expression in the λ system, we constructed a Q- mutant λ vector that can be used in long-term operations such as a two-stage continuous operation. The Q- mutant phage λ is deficient in the synthesis of proteins involved in cell lysis and λ DNA packaging, while the S- mutant is deficient in the synthesis of one of two phage proteins required for lysis of the host cell and liberation of the progeny phage. Therefore, it is expected that the replicated Q- λ DNA containing a cloned gene would not be coated by a phage head and would remain naked for ample expression of the cloned gene and host cells would not lyse easily and consequently would produce larger amounts of cloned-gene products. The β-galactosidase expression per unit cell by the Q- mutant in a lytic state was about 30 times higher than that in a lysogenic state, while the expression by the commonly used S- mutant in a lytic state was twice as high as that in a lysogenic state. The optimal switching time of the Q- mutant from the lysogenic state to the lytic state for the maximum production of β-galactosidase was 5.3 h, which corresponds to an early log phase in the batch operation. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 529-535, 1998.
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  • 50
    ISSN: 0006-3592
    Keywords: biofilm ; streamers ; biofouling ; drag ; fast Fourier transform analysis ; hydrodynamics ; oscillations ; pressure drop ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 μm in diameter. The largest clusters were approximately 85 μm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 536-544, 1998.
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  • 51
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 545-551 
    ISSN: 0006-3592
    Keywords: enzyme array ; pulsed amperometric detection ; carbohydrate analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The introduction of an enzyme array-electrochemical detection method for carbohydrate analysis is demonstrated by using two complex and one high mannose N-linked oligosaccharides. Instead of measuring the remaining uncleaved oligosaccharides in enzymatic digestion, released monosaccharides are directly quantified by pulsed amperometric detection at a gold electrode. The measured monosaccharide concentrations in combination with the enzyme array analysis provide structural characterization of oligosaccharides. The enzyme array-electrochemical detection method does not require any separation procedure or any prior labeling of oligosaccharides. However, this method is limited by the use of purified oligosaccharide samples and the nature of the enzyme array. The development of more sophisticated enzyme arrays relies upon the introduction of a bank of highly specific (bond, arm, aglycon) exoglycosidases. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 545-551, 1998.
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  • 52
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 557-570 
    ISSN: 0006-3592
    Keywords: Alcaligenes eutrophus ; polyhydroxyalkanoates ; metabolic engineering ; mathematical modeling ; enzyme kinetics ; regulation of metabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model describing intracellular polyhydroxybutyrate (PHB) synthesis in Alcaligenes eutrophus has been constructed. The model allows investigation of issues such as the existence of rate-limiting enzymatic steps, possible regulatory mechanisms in PHB synthesis, and the effects different types of rate expressions have on model behavior. Simulations with the model indicate that activities of all PHB pathway enzymes influence overall PHB flux and that no single enzymatic step can easily be identified as rate limiting. Simulations also support regulatory roles for both thiolase and reductase, mediated through AcCoA/CoASH and NADPH/NADP+ ratios, respectively. To make the model more realistic, complex rate expressions for enzyme-catalyzed reactions were used which reflect both the reversibility of the reactions and the reaction mechanisms. Use of the complex kinetic expressions dramatically changed the behavior of the system compared to a simple model containing only Michaelis-Menten kinetic expressions; the more complicated model displayed different responses to changes in enzyme activities as well as inhibition of flux by the reaction products CoASH and NADP+. These effects can be attributed to reversible rate expressions, which allow prediction of reaction rates under conditions both near and far from equilibrium. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 557-570, 1998.
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  • 53
    ISSN: 0006-3592
    Keywords: baroenzymology ; reversed micelles ; α-chymotrypsin ; catalytic activity and stability ; effect of pressure, temperature, and glycerol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermostability of α-chymotrypsin at normal pressure in reversed micelles depends on both an effective surfactant solvation degree and glycerol content in the system. The difference in α-chymotrypsin stability in reversed micelles at various glycerol concentrations [up to 60% (v/v)] was more pronounced at high surfactant degrees of solvation, R ≥ 16. After a 1-h incubation at 40°C in “aqueous” reversed micelles (in the absence of glycerol), α-chymotrypsin retained only 1% of initial catalytic activity and 10, 22, 59, and 48% residual activity in glycerol-solvated micelles with 20, 30, 50, and 60% (v/v) glycerol, respectively. The explanation of the observed effects is given in the frames of micellar matrix structural order increasing in the presence of glycerol as a water-miscible cosolvent that leads to the decreasing mobility of the α-chymotrypsin molecule and, thus the increase of its stability. It was found that glycerol or hydrostatic pressure could be used to stabilize α-chymotrypsin in reversed micelles; a lower pressure is necessary to reach a given level of enzyme stability in the presence of glycerol. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 552-556, 1998.
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  • 54
    ISSN: 0006-3592
    Keywords: structured model ; morphology ; DiOC6 ; image analysis ; Aspergillus oryzae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A morphologically structured model is well suited for obtaining a good description of growth and product formation of filamentous fungi for use in a process model, for example. This article describes a new morphologically structured model and its application to an α-amylase producing strain of Aspergillus oryzae. The model is based on a division of the fungal hyphae into three different regions: an extension zone, representing the tips of the hyphae; an active region, which is responsible for growth and product formation; and an inactive hyphal region. Two metamorphosis reactions describing branching and inactivation are included in the model, and the kinetics of branching and tip extension are based on known experimentally verified models of fungal microscopic morphology. To verify the structure of the model a double-staining method, based on a combination of fluorescence microscopy and automated image analysis, has been developed for measuring the fraction of active cells. The method employs the fluorescent dye 3,3′-dihexyloxocarbocyanin to stain organelles inside the hyphae and Calcoflour White to stain the cell wall. The ratio between the projected areas of the organelles and of the entire hyphal element is then taken to be proportional to the fraction of active cells. When applied to chemostat and fed-batch experiments, the double-staining method seemed to confirm the basic morphological structure of the model. The model is able to produce accurate simulations of steady-state and transient conditions in chemostats, of batch cultivations, and even the formation of a single hyphal element from a spore, all with the same values of the model parameters. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 321-329, 1998.
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  • 55
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 330-341 
    ISSN: 0006-3592
    Keywords: brewers' yeast ; collision theory ; flocculation ; modeling ; surface erosion ; floc splitting ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flocculation of yeast cells occurs during the fermentation of beer. Partway through the fermentation the cells become flocculent and start to form flocs. If the environmental conditions, such as medium composition and fluid velocities in the tank, are optimal, the flocs will grow in size large enough to settle. After settling of the main part of the yeast the green beer is left, containing only a small amount of yeast necessary for rest conversions during the next process step, the lagering. The physical process of flocculation is a dynamic equilibrium of floc formation and floc breakup resulting in a bimodal size distribution containing single cells and flocs.The floc size distribution and the single cell amount were measured under the different conditions that occur during full scale fermentation. Influences on flocculation such as floc strength, specific power input, and total number of yeast cells in suspension were studied. A flocculation model was developed, and the measured data used for validation. Yeast floc formation can be described with the collision theory assuming a constant collision efficiency. The breakup of flocs appears to occur mainly via two mechanisms, the splitting of flocs and the erosion of yeast cells from the floc surface. The splitting rate determines the average floc size and the erosion rate determines the number of single cells. Regarding the size of the flocs with respect to the scale of turbulence, only the viscous subrange needs to be considered. With the model, the floc size distribution and the number of single cells can be predicted at a certain point during the fermentation. For this, the bond strength between the cells, the fractal dimension of the yeast, the specific power input in the tank and the number of yeast cells that are in suspension in the tank have to be known. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 330-341, 1998.
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  • 56
    ISSN: 0006-3592
    Keywords: biodegradation kinetics ; naphthalene ; nonaqueous phase liquid ; mass transfer ; naphthoquinone ; coaltar ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is formulated to describe dissolution of naphthalene from an insoluble nonaqueous phase liquid (NAPL) and its subsequent biodegradation in the aqueous phase in completely mixed batch reactors. The physicochemical processes of equilibrium partitioning and mass transfer of naphthalene between the NAPL and aqueous phases were incorporated into the model. Biodegradation kinetics were described by Monod's microbial growth kinetic model, modified to account for the inhibitory effects of 1,2-naphthoquinone formed during naphthalene degradation under certain conditions. System parameters and biokinetic coefficients pertinent to the NAPL-water systems were determined either by direct measurement or from nonlinear regression of the naphthalene mineralization profiles obtained from batch reactor tests with two-component NAPLs comprised of naphthalene and heptamethylnonane. The NAPLs contained substantial mass of naphthalene, and naphthalene biodegradation kinetics were evaluated over the time required for near complete depletion of naphthalene from the NAPL. Model predictions of naphthalene mineralization time profiles compared favorably to the general trends observed in the data obtained from laboratory experiments with the two-component NAPL, as well as with two coal tars obtained from the subsurface at contaminated sites and composed of many different PAHs (polycyclic aromatic hydrocarbon compounds). The effects of varying the NAPL mass and the naphthalene mole fractions in the NAPL are discussed. It was observed that the time to achieve a given percent removal of naphthalene does not change significantly with the initial mass of naphthalene in a fixed volume of the NAPL. Significant changes in the mineralization profiles are observed when the volume (and mass) of NAPL in the system is changed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 356-366, 1998.
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  • 57
    ISSN: 0006-3592
    Keywords: methanogenic population dynamics ; anaerobic digesters ; solid waste ; biosolids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic (37°C) and thermophilic (55°C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m3/day and the retention time was 20 days. Ribosomal RNA-targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start-up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start-up period (20 days), stable performance was observed with high gas production rates (1.52 m3/m3/day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start-up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start-up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 342-355 1998.
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  • 58
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 631-641 
    ISSN: 0006-3592
    Keywords: ceramic membrane ; water-oil ; shear rate ; transmembrane pressure ; pore size ; lumen diameter ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recovery of an aqueous bioconversion product from complex, two-phase Pseudomonas putida broths containing 20% (v/v) soybean oil presents a significant challenge for downstream processing. Although not used before in multiple-phase separation for complex biotech products, crossflow filtration employing ceramic filters is one of the most attractive options which allow the design of integrated, continuous bioconversion processes. As a first attempt, we studied multichannel, monolithic ceramic membranes of different nominal pore sizes and lumen diameters under steady-state conditions. The best performance was obtained with 0.2-μm-pore/3-mm-lumen membrane, which completely rejected both cells and oil droplets from the permeate, creating a clear aqueous product stream. Although the same separation was achieved, the 50K molecular weight cut-off (MWCO) ultrafilter showed greater irreversible but similar reversible resistance, in addition to an order-of-magnitude higher membrane resistance. Larger nominal pore microfilters, such as 0.45 and 1.0 μm, experienced both cell and oil leakage even at low transmembrane pressure (10 psig). Attributed to greater shear at the same recirculation rate, smaller lumen filters did provide greater permeate flux. However, for practical purposes, the 0.2-μm-pore/4-mm-lumen ceramic membrane was chosen for further evaluation. Transmembrane pressures up to 50 psig provided only marginal gains in filtration performance, whereas increasing shear rate resulted in linear increases in steady-state flux, presumably due to formation of shear-sensitive, complex gel/oil/cell layer near the membrane surface. A nominal shear rate of 9200 s-1 and 20 psig transmembrane pressure were chosen as optimal operating conditions. Additional studies in a clean system revealed that as low as 5% (v/v) soybean oil in deionized (DI) water resulted in an order-of-magnitude decline in steady-state permeate flux. Breakthrough of oil droplets occurred at 35 psig transmembrane pressure. The severe fouling and breakthrough phenomena disappeared in the presence of washed cells for transmembrane pressure up to 43 psig, implying an oil/cell layer coating the membrane surface, thus preventing oil penetration. Serious membrane fouling was also experienced in microfiltration of oil-free, cell-free supernatant and oil-free whole broth. Consequently, soluble proteins/surfactants were suspected to be the major membrane foulants. Interestingly, soybean oil up to 30% (v/v) enhanced the flux, presumably through complicated interactions with the major foulants. Regeneration of membrane was best achieved with protease and hot caustic/bleach treatments, supporting the hypothesized fouling mechanisms mentioned above. This work provides process and system information for batch microfiltration runs in the future, to be reported elsewhere as Part II of this work. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 631-641, 1998
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  • 59
    ISSN: 0006-3592
    Keywords: islets of Langerhans ; microencapsulation ; poly(ethylene glycol) ; photopolymerization ; hydrogels ; bioartificial organs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method has been defined to interfacially photopolymerize poly(ethylene glycol) diacrylates (PEG diacrylates) to form a crosslinked hydrogel membrane upon the surfaces of porcine islets of Langerhans to serve as an immune barrier for allo- and xenotransplantation. A sensitivity study of six key parameters in the interfacial photopolymerization process was performed to aid in determination of the optimal encapsulation conditions, leading to the most uniform hydrogel membranes and viable islets. The key parameters included the concentrations of the components of the initiation scheme, namely eosin Y, triethanolamine, and 1-vinyl 2-pyrrolidinone. Other parameters investigated included the duration and flux of laser irradiation and the PEG diacrylate molecular weight. Each parameter was doubled and halved from the standard conditions used in the encapsulation process while holding all the remaining parameters at the standard conditions. The effects of changing each parameter on islet viability, encapsulation efficiency, and gel thickness were quantified. Islet viability was sensitive to the duration of laser illumination, viability significantly increasing as the duration was reduced. Encapsulation efficiency was sensitive to the concentrations of eosin Y, triethanolamine, and 1-vinyl 2-pyrrolidinone, to the laser flux, and to the PEG diacrylate molecular weight. Increasing the concentration of eosin Y significantly improved the encapsulation efficiency, while decreasing the concentration of 1-vinyl 2-pyrrolidinone and increasing the concentration of triethanolamine had the greatest effects in significantly reducing the encapsulation efficiency. Gel thickness was sensitive to the concentrations of triethanolamine and 1-vinyl 2-pyrrolidinone, to the duration of laser illumination, and to the PEG diacrylate molecular weight. Increasing the PEG diacrylate molecular weight significantly increased the gel thickness, while decreasing the concentration of 1-vinyl 2-pyrrolidinone and increasing the concentration of triethanolamine had the greatest effects in significantly reducing the gel thickness. From this sensitivity study, conditions were determined to encapsulate porcine islets, resulting in greater than 90% islet viability and greater than 90% encapsulation efficiency. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 655-665, 1998
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  • 60