bluuebunny/crossref_metadata_2025_split huggingface dataset:
The measurement of transmembrane helices by the deconvolution of CD spectra of membrane proteins: A review
Authors: Fasman Gerald D. 
Published: December 2004

AbstractThe interpretation of the CD spectra of proteins to date requires additional secondary structural information of the proteins to be analyzed, such as x‐ray or nmr data. Therefore, these methods are inappropriate for a CD data base whose secondary structures are unknown, as in the case of the membrane proteins. The Convex Constraint Analysis algorithm [A. Perczel, M. Hollósi, G. Tusnády, and G. D. Fasman (1991) Protein Engineering, Vol. 4, 669–679], on the other hand, operates only on a collection of spectral data to extract the common spectral components with their spectral weights. The linear combinations of these derived “pure” CD curves can reconstruct the original data set with great accuracy. For a membrane protein data set, the five‐component spectra so obtained from the deconvolution consisted of two different types of α‐helices (the α‐helix in the soluble domain and the αT‐helix, for the transmembrane α‐helix), a β‐pleated sheet, a class C‐like spectrum related to β‐turns, and a spectrum correlated with the unordered conformation. The deconvoluted CD spectrum for the αT‐helix was characterized by a positive red‐shifted band in the range 195–200 nm (+95,000 deg cm2 dmol−l), with the intensity of the negative band at 208 nm being slightly less negative than that of the 222 nm band (−50,000 and −60,000 deg cm2 dmol−1, respectively) in comparison with the regular α‐helix, with a positive band at 190 nm and two negative bands at 208 and 222 nm with magnitudes of + 70,000, −30,000, and −30,000 deg cm2 dmol−1, respectively. © 1994 John Wiley & Sons, Inc.
Concept and progress in the development of RGD‐containmg peptide pharmaceuticals
Authors: Craig William S. , Cheng Soan , Mullen Daniel G. , Blevitt Jon , Pierschbacher Michael D. 
Published: December 2004

AbstractThe cell adhesion domain, arginine‐glycine‐aspartic acid (RGD), has been incorporated into synthetic peptides to perform either of two modes of drug action, antagonist or agonist. Short, conformationally constrained peptides have been developed as antagonists for the platelet membrane glycoprotein complex, the integrin α11b, β3, using cell‐based and integrin‐based assays. In combination with a comparative molecular modeling study, these results have helped identify common conformotional elements in the pharmacophore of this class of molecules. Peptides are presented that are highly potent, integrin specific, and that possess reduced pharmacological side effects. Also presented is the development of a peptide that modifies, noncovalently, the surfaces of a wide variety of synthetic materials used in medical implants. The agonist activity of this molecule is evident from its ability to stimulate cell attachment on these surfaces. This is shown to translate into an in vivo activity of faster and more complete tissue integration, and a reduction in foreign body response. © 1994 John Wiley & Sons, Inc.
The kinetics of cholesterol oxidase synthesis by Nocardia rhodocrous
Authors: Buckland B. C. , Lilly M. D. , Dunnill P. 
Published: December 2004

AbstractThe production of cholesterol oxidase by 3 liter batch cultures of Nocardia rhodocrous growing on a glycerol/yeast extract medium was investigated. Cholesterol was shown to be a good inducer of the enzyme. The optimum time for cholesterol addition and the quantity to be added were determined, resulting in a 15‐fold yield increase. Cholesterol oxidase synthesis was influenced by the dissolved oxygen tension. Maximum cholesterol oxidase production was obtained at 30–40% air saturation. The effect of growth conditions on the extraction of cholesterol oxidase by Triton X‐100 was investigated. The scale‐up of the fermentation to 800 liters in a pilot‐plant fermenter is described.
Effects of immobilization on the kinetics of enzyme‐catalyzed reactions. II. Urease in a packed‐column differential reactor system
Authors: Ramachandran K. B. , Perlmutter D. D. 
Published: December 2004

AbstractUrease from Jack bean was immobilized on nonporous glass beads by covalent bonding and its kinetics were studied in a packed‐column differential reactor. To facilitate comparison, the urease was immobilized by both diazo and glutaraldehyde coupling. The kinetic properties of immobilized urease were similar to those of the soluble enzyme and different immobilization methods did not appreciably alter the kinetic properties. The affects of three different amino acid activators appear to follow predictions obtained from a relatively simple competitive model, except at very low substrate levels.
Biological treatment of waste with high ash content using a hydrolytically assisted extended aeration process
Authors: Gaudy A. F. , Manickam T. S. , Saidi H. , Reddy M. P. 
Published: December 2004

AbstractIn previous reports from this laboratory it has been shown that the extended aeration process for biological treatment of organically laden municipal and/or industrial waste could be successfully employed for concurrent purification and sludge disposal. Also results using a modified process in which autodigestion was aided and controlled by periodic partial hydrolysis of small portions of the recycle sludge showed that operational control was feasible. There was some question regarding the success of such a process if the original waste contained a large portion of inorganic solids. Accordingly, a 1½ year pilot plant study was made using a waste (hydrolyzed trickling filter sludge) of exceptionally high ash content (50–60%). It was found that the ash content of activated sludge grown on this substrate did not continually increase nor did the high ash content of the waste interfere in any way with the efficiency of removal of organic matter. In general it exceeded 90 percent. Also a highly nitrified effluent was produced. A variety of analyses were performed: COD, BOD, TOC, suspended solids, NH3‐N, organic‐N, NO3‐N, etc. Interrelationships between these important monitoring parameters for assessing plant performance offered useful insight into operational control for hydrolytically assisted extended aeration processes.
Yield and maintenance relations of yeast growth in the chemostat at superoptimal temperatures
Authors: Van Uden N. , Madeira‐Lopes A. 
Published: December 2004

AbstractA model is proposed that accounts for the decreases in yield which occur in chemostat cultures of mesophilic yeasts at superoptimal growth temperatures. Two yield depressing effects were identified, one due to increased maintenance requirements by the viable fraction of the population, the other due to energy substrate dissipation by the nonviable fraction. The two effects are functions of the dilution rate, as is the fraction of nonviable cells. Experimental results were obtained on the yield, maintenance, and dissipation of energy substrate in a glucose‐limited chemostat culture of a respiration‐deficient mutant of Saccharomyces cerevisiae at 39°C. The rates of glucose utilization for maintenance and for dissipation constituted, respectively, 33–28% and 15–9% of the total glucose utilization rate over the range of dilution rates tested (0.038–0.064 hr−1), while the yield varied over this range from 0.066–0.085 g of biomass (dry wt) per gram of glucose.
Influence of cell concentration, temperature, and press performance on flow characteristics and disintegration in the freeze‐pressing of Saccharomyces cerevisiae with the X‐press
Authors: Magnusson K.‐E. , Edebo L. 
Published: December 2004

AbstractThe pressure required for initiation of flow when freeze‐pressing with the X‐press is related to the phase boundaries of water, particularly those between ice I and liquid even at temperatures around −25°C and lower. Widening the orifice of the pressure chamber to diameters larger than 2.5 mm leads to lower pressures and less extensive cell disintegration.Pressing Saccharomyces cerevisiae slowly with the aid of a manual hydraulic jack at −25°C produces a disintegration of 60–75% irrespective of cell concentration. Pressing at −35°C shows no clear differences.Pressing more rapidly with the aid of a motor‐driven hydraulic press produces a similar extent of disruption of diluted cell suspensions (5.4 mg/g) as slow pressing. However, freeze‐pressing a paste of baker's yeast (270 mg/g) increases the degree of disintegration. Under these conditions the disintegration is further enhanced by a lower temperature, −35°C, and by a high velocity of flow through the orifice, such that more than 95% of the S. cerevisiae is disrupted by one pressing at less than 2 × 108 Pa.Mechanisms for flow through the X‐press are suggested and discussed in relation to the phase diagram of water.
Aroma of sherry wines
Authors: Webb A. Dinsmoor , Noble Ann C. 
Published: December 2004

AbstractOver 130 volatile components have been identified in aromas of film (F), submerged‐culture flor (S), and baked (B) sherries. The composition of these volatiles, which include more than 25 alcohols, five carbonyls, ten acetals, three amides, 35 esters, and five lactones, is influenced by the variety of grape used, the nature of the primary alcoholic fermentation, type of cooperage, aging and blending system, and filmphase yeast metabolism in (F) and (S) or reactions occurring during “baking” in (B). The influence of these factors on the aroma and several volatile formation mechanisms which contribute to the characteristic flavor of sherry, particularly during the film growth and during baking, are discussed.
The mode of interaction between the substrate and cell surface of the hydrocarbon‐utilizing yeast Candida tropicalis
Authors: Kaeppeli O. , Fiechter A. 
Published: December 2004

AbstractA method for the measurement of the affinity of the cell surface to hydrocarbons is described. The affinity was basically unaffected by different pH values and temperature as well as by the chain length of the substrate. The contact time required for saturation of the cell surface with substrate was 30 sec. Cells grown on glucose showed a 25% lower adsorption capacity compared to those grown on n‐alkane. The glucose grown cells showed also a more distinguished dependence of the amount of adsorbed hydrocarbon on the quality of the emulsion. The interaction between the substrate and cell surface turned out to be an adsorption that did not involve an enzymatic reaction. These results led to the conclusion that a lipopolysaccharide moiety present at the cell surface is responsible for the affinity.
Large‐scale disintegration of microorganisms by freeze‐pressing
Authors: Magnusson K.‐E. , Edebo L. 
Published: December 2004

AbstractA semicontinuous press has been constructed for the disintegration of microorganisms and other biological material by freeze‐pressing, i.e., pressure extrusion of frozen material through a narrow hole. The material to be freeze‐pressed is frozen in the form of cylindrical rods, which fit into the pressure chamber and are extruded by a piston forced back and forth by means of a hydraulic pump. At a sample temperature of −35°C and a press temperature of −20°C, about 90% disruption is achieved in a single passage of undiluted baker's yeast (Saccharomyces cerevisiae, 270 mg/g) through the orifice of the pressure chamber. With this press about 10 kg of material can be freeze‐pressed per hour.
A mathematical model for microbial growth under limitation by conservative substrates
Authors: Nyholm Niels 
Published: December 2004

AbstractA mathematical model is suggested for growth of microorganisms under limitation by “conservative” substrates such as inorganic ions or vitamins that are not broken down after uptake into the cells, but that wholely or partly remain available for production of biomass. The specific growth rate is expressed here as a function of the intracellular “concentration” of the limiting substrate, defined as the amount of substrate within the cells per unit of cell dry weight.In the model, the intracellular substrate is divided into two parts. One part is a “structural” substrate not available for further growth. The other part is an “excess” or “functional” substrate that is used for biomass production and is assumed to be converted into structural substrate proportionally to growth. The rate of growth is believed to be controlled by the intracellular concentration of excess substrate.
Temperature‐influenced species competition in mass cultures of marine phytoplankton
Authors: Goldman Joel C. , Ryther John H. 
Published: December 2004

AbstractFive marine phytoplankton species (Phaeodactylum tricornutum, Thalassiosira pseudonana, Skeletonema costatum, Monochrysis lutheri, and Dunaliella tertiolecta) were grown in enriched laboratory continuous cultures and natural populations were mass cultured outdoors for 16 months. Competition among the species was shown to be highly dependent on temperature, although the actual production of plant organic matter at the low growth rates used was relatively independent of this variable. Control of marine species in mass cultures does not appear economically feasible, but this drawback may be overcome by selecting herbivorous shellfish that are capable of assimilating those temperature‐dependent phytoplankton species dominating in a particular locale.
A fermentation process for producing both ethanol and lysine‐enriched yeast
Authors: Tanner Robert D. , Souki Nabil T. , Russell Richard M. 
Published: December 2004

AbstractIn 18 batch‐fermentation experiments, baker's yeast was grown in an enriched mineral medium, containing 10% by weight glucose, at various pH and temperature levels. The pH and temperature are just two representative engineering variables which and be easily varied at negligible cost. The commercial yeast inoculum, .20% by weight or about .16% viable cells, was selected to represent industrial (nonsterile) conditions. Free L‐lysine, ethanol, and cell growth were followed in time for each batch run held at a fixed pH and temperature. The maximum free lysine level reached at either 10½ or 24 hr occurred at a pH of 5 and 32°C. At 24 hr, the peak free lysine level, 120 mg/liter, is three times as great as the uncontrolled pH counterpart. In terms of total L‐lysine, (free plus protein‐bound) the peak represents a 25% improvement over the uncontrolled case, based on an average 3.5% lysine level per cell weight. The greatest measured cell level, .9% by weight in the fermentation broth, or a 5½‐fold increase over the inoculum, was reached during the 36°C and pH 3 run, while the largest measured ethanol value (3%, or 30% conversion by weight from glucose) was achieved during the 28°C and pH 6 experiment. The optimal lysine run produced, however, no less than 15% of the maximum cell and 30% of the maximum ethanol levels.
Effects of quantitative shock loadings on the constant recycle sludge concentration activated‐sludge process
Authors: Wong Y. K. , Yang P. Y. 
Published: December 2004

AbstractThe reliability of the process of Ramanathan and Gaudy (Biotechnol Bioeng., 13, 125 (1971)) for the completely mixed activated‐sludge process holding the recycle cell concentration, XR, as a system constant with respect to step changes in hydraulic retention time was investigated. The experiments were run at initial dilution rates of ⅛, ⅙, ¼, and ½ hr−1 treating a soft drink bottling wastewater. The influent substrate concentration was maintained at 1000 mg/liter chemical oxygen demand and the hydraulic recycle ratio at 0.3. The recycle sludge concentration was maintained at about 7000 mg/liter.It was found that the system could accommodate hydraulic shock loads up to 200% positive changes and down to 50%negative changes without disruption of the effluent quality. Shorter retention time of the range studied, from 2 to 8 hr, has the advantage of shorter response time with respect to the response of the concentration of biological solids in the reactor.
Computer‐aided material balancing for prediction of fermentation parameters
Authors: Cooney Charles L. , Wang Henry Y. , Wang Daniel I. C. 
Published: December 2004

AbstractDespite the importance of biomass as a parameter in fermentation processes, there are no commercially available sensors suitable for its measurement. An indirect approach for the assessment of biomass concentration can be based on material balances and on the direct monitoring of fermentation parameters for which there are established sensors (e.g., gaseous oxygen and carbon dioxide). As a consequence, this method requires no assumption of cellular yield coefficients or rate constants. This approach is also readily adaptable to general use since it requires only some knowledge of the compositions of the substrate, cells, and noncellular products.
Nonporous magnetic materials as enzyme supports: Studies with immobilized chymotrypsin
Authors: Munro P. A. , Dunnill P. , Lilly M. D. 
Published: December 2004

AbstractChymotrypsin has been immobilized to several nonporous magnetic materials. Nickel particles were considered to be most suitable as immobilized enzyme supports. Chymotrypsin immobilized to nonporous magnetic supports was not fouled significantly by6 either whole milk or clarified yeast homogenate. AE‐cellulose‐chymotrypsin was rapidly fouled by both these materials and chymotrypsin immobilized to acrylic‐based ion exchangers was slowly fouled. Immobilized enzyme activity was found to be inverted proportional to particle diameter for nonporous rock magnetite particles. Immobilization by adsorption and then glutaraldehyde crosslinking was used to produce controlled amounts of chymotrypsin on the particles. Esterolytic activity increased with enzyme loading but caseinolytic activity did not increase. Chymotrypsin is inhibited by metal ions from the magnetic supports. It is partially protected by use of a preliminary protein coating and may be reactivated by incubation with EDTA or BSA.
Properties of intracellular ribonuclease utilized for RNA reduction in disintegrated cells of Saccharomyces cerevisiae
Authors: Lindblom Marianne 
Published: December 2004

AbstractThe properties of intracellular RNase in disintegrated cell suspensions of Saccharomyces cerevisiae have been studied. The influence of salt addition and/or incubation of the suspension on the activity of RNase and on the degradation of endogenous RNA was determined. No significant change in the RNase activity in the disintegrated suspensions was obtained by addition of 3% NaCl or by incubation at 50°C with 3% NaCl. During the incubation with NaCl the active RNase was able to degrade endogenous RNA. By incubation without salt the RNase was inactivated. Inactivation also occurred after extraction at alkaline pH. The RNase had an optima at pH 5–6 and temperatures between 50–60°C. The main part of the RNase in the unincubated suspension was soluble at pH 5.6 but not at pH 4.0. After incubation with NaCl the RNase was soluble at pH 4.0. No serious protein degradation occurred during the short time incubation needed for RNA reduction. 70% of the protein in the suspensions was recovered in the precipitate at pH 4.0 after 20 min of incubation. The corresponding protein recovery from unincubated suspensions was 77%.
Continuous fermentation in slant tubes
Authors: Wick Emil , Popper Karel 
Published: December 2004

AbstractContinuous, steady‐state grape‐juice fermentation, carried out in experimental slant‐tube fermentors, was characterized by complete fermentation, even at fast pumping rates, because efficient cell retention, as well as rapid yeast growth, quickly built cell density up to the limit permitted by the juice supply rate. Essentially complete fermentation was easily achieved with a juice residence time of 3.1 hr, compared to about 120 hr in normal batch fermentation. Successful continuous fermentation required constancy of gas and liquid flow through the tubes, placing some restrictions on choice of tube configurations. The validity of design equations, developed previously from a settling model, was tested, and some practical aspects of their application to fermentor design and operation were demonstrated.
Aminoacylase pellets
Authors: Hirano Ken‐Ichi , Karube Isao , Suzuki Shuichi 
Published: December 2004

AbstractAminoacylase was immobilized on the mycelium pellets of Aspergillus ochraceus by using albumin and glutaraldehyde. No difference in the optimum pH was observed between native aminoacylase and aminoacylase pellets. The amino‐acylase pellets were stable in pH 4–8 but they were unstable in alkaline conditions. The aminoacylase pellets were more stable against heavy metal ions and inhibitors than native aminoacylase. However, the degree of the activation of aminoacylase with cobalt ion decreased with the immobilization. It was suggested that most of aminoacylase was covalently coupled to the mycelium with glutaraldehyde.
The growth of L‐cells and Vero cells on an autoclavable MEM–peptone medium
Authors: Keay Leonard 
Published: December 2004

AbstractThe growth of L‐60TM cells (a suspension culture adapted L‐cell) on media composed of MEM (minimum essential medium (Eagle)) and bactopeptone autoclaved together or separately under a variety of conditions has been determined. It has been found that MEM autoclaved with 0.5% bactopeptone at 15 psi for 20 min, cooled and then neutralized with NaHCO3, consistently supported good cell growth of L‐60TM and L‐929 cells. Similar results were obtained when the MEM and bactopeptone were autoclaved separately. The cells grew initially as a monolayer, subsequently becoming a stationary suspension. Some experiments were carried out with agitated suspension culture of L‐60TM cells in the autoclaved MEM–bactopeptone combination with and without added methylcellulose and results were obtained which indicate that large scale suspension culture is possible in this system. Other peptones were also found to support cell growth.The autoclaved MEM–bactopeptone combination also supported the growth of Chang liver and Vero cells. The Chang liver cells rapidly dissociated from the plastic surface but the Vero cells remained sufficiently securely attached so that it was possible to grow them near to confluency in roller bottles.
Oxygen transfer in mechanically agitated aqueous systems containing dispersed hydrocarbon
Authors: Hassan Ibrahim T. M. , Robinson Campbell W. 
Published: December 2004

AbstractThe effect of dispersed n ‐dodecane or n ‐hexadecane on the air‐to‐aqueous phase overall volumetric oxygen transfer coefficient in a simulated (cell‐free) stirred‐tank fermentor is described. The oil volume fraction ranged from zero to 0.10; the ionic strength of the aqueous phases was varied from 0 to 0.45. The air‐to‐aqueous phase coefficients in both oil‐free (KLa) and oil‐bearing (KLa*) systems were evaluated from unsteady‐state experiments using a membrane‐covered probe to follow the aqueous phase dissolved oxygen tension.For all systems studied, KLa*/KLa was found to be independent of P/V and vs for all practical purposes. However, for a particular aqueous phase and at a given P/V and vs, the ratio KLa*KLa generally differed from unity. Depending on the combination of hydrocarbon type and volume fraction and the aqueous‐phase ionic strength employed, the dispersed hydrocarbon may, in some cases, reduce the rate of oxygen transfer and in others enhance it relative to that of the corresponding oil‐free gas–liquid dispersion. Enhancement of the air‐to‐aqueous transfer rate by such negative spreading coefficient hydrocarbons has not been reported previously.